Rice is the most important food crop in China, and plays an important role in ensuring national food security. At present, the transformation of the traditional small-scale production to rice production mechanization, intelligent, standardization and modern large-scale production with the intensification are faced. In this important historical node, this review summarized the development of rice cultivation with Chinese characteristics and the main scientific and technological achievements in nearly 70 years, and explored the future of rice cultivation technology development direction is of great significance. Over the past 70 years, the rice agronomist hold the bottleneck problem and key cultivation technology in the large-scale production, and researched the law of rice growth and yield and quality formation and its relationship with environmental conditions and cultivation measures, and explored rice growth regulation, culture optimization decision and some new methods of cultivation and management. A large number of widespread application cultivation technique and theory and its achievements had obtained in nearly 70 years. Ten mainly aspects of rice cultivation scientific and technological achievements were emphatically expounded in China since the reform and opening up, such as rice leaf age model cultivation theory and technology, population quality cultivation and its control, accurate quantitative cultivation, light simplified cultivation, mechanized cultivation, super-high-yield cultivation, high quality cultivation, green cultivation and adversity cultivation, regional cultivation. And the important direction of development of the future Chinese rice cultivation and innovation was pointed out: (1) To strengthen the coordination of rice green, high quality and high yield and extensive cultivation research; (2) To strengthen the research on high quality cultivation of multi-purpose rice; (3) To strengthen the research on synergistic rules and practical cultivation of super high yield and quality improvement of rice; (4) To strengthen the research on the mechanized cultivation of direct seeding rice and reproducing rice with high yield and high quality; (5) To strengthen the intelligent and unmanned cultivation of rice.
【Objective】The differences of physical and chemical characteristics related to appearance and taste of some high-quality japonica rice varieties in China were studied in order to provide some theoretical basis for improvement of high-quality japonica rice varieties.【Method】39 japonica rice varieties participating in the second national high-quality rice variety taste quality evaluation activities were used as materials to study the differences in appearance and cooking taste quality of different japonica rice varieties, and to analyze the relationship between various physical and chemical indexes of rice and taste quality. 15 japonica rice varieties that won the second national high-quality rice variety taste quality evaluation gold medal were divided into two major sources of south and north according to regions, and the differences in appearance and taste related physical and chemical indexes of japonica rice from different regions were compared and studied.【Result】(1) The 39 japonica rice varieties participating in the second national high-quality rice variety taste quality evaluation activities had great differences in grain type, chalkiness rate and chalkiness degree. In terms of cooking taste, the taste value measured by the rice taste meter and the sensory score of experts were 44.00-82.00 and 52.20-91.86, respectively. Amylose content of rice, setback, consistence in RVA spectrum, stickiness and balance in texture characteristics of rice were significantly negatively correlated with taste value of rice, with correlation coefficients of -0.39, -0.60, -0.57, -0.37 and -0.56, respectively. However, the peak viscosity and breakdown in RVA spectrum were significantly positively correlated with the taste value of cooked rice, with correlation coefficients of 0.32 and 0.36, respectively. (2) Compared with northern high-quality japonica rice, chalkiness rate and chalkiness degree of southern high-quality japonica rice increased by 178.78% and 139.11%, respectively; amylose content decreased by 28.25%, protein content increased by 7.37%; setback and consistence in RVA spectra of rice flour decreased by 12.00% and 21.19%, respectively. The absolute values of stickiness and balance in texture characteristics of cooked rice increased by 16.15% and 15.00%, respectively; There was no significant difference between the taste value measured by the rice taste meter and the expert sensory score between the high-quality japonica rice from the south and the north.【Conclusion】The appearance and cooking taste quality of japonica rice varieties participating in the second national high-quality rice variety taste quality evaluation activities were significantly different. The appearance of northern japonica rice was crystal clear, chalkiness degree was 0.50%-3.50%, amylose content of rice was high, protein content was low, and taste was 56.00-74.00. However, the appearance of southern japonica rice was relatively turbid with chalkiness degree of 1.86%-11.21%. Although the protein content was high in rice, the amylose content was low, the rice cooked was soft and sticky, and the taste value was 54.00-82.00.
【Objective】 In order to provide a theoretical basis for rational management of irrigation and nitrogen (N), the effects of the different water and nitrogen application models on the nitrogen absorption and translocation, and nitrogen use efficiency of indica hybrid rice, nitrogen transformation characteristic in paddy soil and their relationships with rice yield were studied. 【Method】 Using the indica hybrid rice Zhongzheyou 1 as experimental material, a two-factor experiment was conducted in 2018 and 2019, including two irrigation regimes (flood irrigation, FI; alternate wet and dry irrigation, AWD) and five nitrogen application types (zero nitrogen, N0; traditional nitrogen level, PUN100; 80% of traditional nitrogen level, PUN80; 80% of control-released nitrogen fertilizer plus biochar, CRFN80-BC; 80% of stable compound nitrogen fertilizer plus biochar, SFN80-BC). The grain yield, nitrogen absorption and utilization of rice, and nitrogen transformation characteristic in paddy soil were measured.【Result】(1) AWD significantly increased the rice yield in relative to that under FI conditions, and rice yields under CRFN80-BC and SFN80-BC treatments were significantly higher than that under PUN80 and even PUN100 treatments (P<0.05). Their values were 9 721 kg·hm-2 and 10 056 kg·hm-2 in 2018, and 9 492 kg·hm-2 and 9 907 kg·hm-2 in 2019, respectively, which was closely related to the increased rice spikelet or tillering number under the AWD condition. (2) Compared with N0, PUN100 and PUN80 treatments, AWD significantly improved the nitrogen accumulation of leaf and stem-sheath before the heading stage, nitrogen translocation and the contribution of nitrogen translocation to panicle from the heading to maturity stage under CRFN80-BC and SFN80-BC treatments. It also significantly increased the contents of the dissolved total nitrogen (DTN) and NO3- in 0-30 cm soil depths at the maturity stage, but greatly suppressed the concentrations of DTN, NH4+ and NO3- in soil leachate. (3) Rice grain yield was significantly and positively correlated with the nitrogen accumulation of nutritional organs (e.g. leaf and stem-sheath), nitrogen translocation and their nitrogen contribution to panicle, and nitrogen use efficiency and soil nitrogen availability at the maturity stage. It indicated that the suitable water and nitrogen management could collaboratively improve the fluency of the nitrogen absorption-translocation in rice and nitrogen availability in paddy soil, which were beneficial for the improvement of rice yield and nitrogen use efficiency.【Conclusion】 Given the results of grain yield, nitrogen utilization and nitrogen availability in rice paddy of the two years, it could be concluded that control-released/stable compound fertilizers combined with biochar could significantly increase the construction of high-yield rice population, rice nitrogen absorption and translocation, and nitrogen use efficiency under AWD irrigation condition, and also reduce the nitrogen leaching loss in paddy soil.
【Objective】Amylose content in rice grain is a key factor affecting the quality of rice noodle. Rice noodles processed from rice with higher amylose content have a strong structure, which can reduce the cooking loss of rice noodle. It is important to regulate the amylose content and quality of noodle rice by ascertaining the amylose accumulation property of noodle rice grain. 【Method】Using two high amylose content noodle rice varieties (Luliangyou 996 and Zhongjiazao 17) and two low amylose content rice varieties (Lingliangyou 268 and Xiangzaoxian 45 as control) as materials, the field experiments were conducted in early and late season in 2016 and 2017. The grain-filling properties and amylose accumulation properties were analyzed based on the Logistic equation. 【Result】The amylose content in noodle rice variety was 44.8%-72.3% significant higher in noodle rice than that of control variety. The amylose accumulation in noodle rice showed 61.2%-92.8%, 60.0%-91.1%, 61.2%-92.3%, and 59.3%-89.3% higher than that in control variety during the gradual increase phase, rapid phase, slow increase phase, and the maximum accumulation rate phase, respectively. In the same planting season, the average rate of amylose accumulation, the accumulation rate during the increasing period and the maximum accumulation rate of noodle rice were 36.7%-91.2%, 40.2%-58.3%, and 29.2%-108.7% higher than that of control variety, respectively. And the duration of the gradual increase period was 0.6-2.8 d longer than the control variety, and the maximum amylose accumulation rate start-up time was 1.4-2.9 d later than that of control variety. The contribution of amylose accumulation in gradual, rapid, and slowly increase period of amylose accumulation duration to total amylose accumulation were relatively stable with different rice varieties growing in different seasons, with the value of 21.03%-21.32%, 57.58%-57.88%, and 11.38%-14.62%, respectively. Grain amylose accumulation was accompanied by the grain filling process, and the gradual, rapid, and slowly increase phase of grain filing dry matter accumulation occurred 0.1-4.9 d earlier than that of the corresponding amylose accumulation. Meanwhile, the grain filling period, maximum filling rate start time and filling duration of noodle rice were on average 0.1-1.8 d, 1.2-2.0 d and 1.2-3.6 d longer or later than that of control variety. The mean temperature and incident radiation during the 5 days after flowering in early season of 2016 were 30.1℃ and 21.1 MJ·m-2, which showed 5.1℃-6.3℃ and 2.0-19.1 MJ·m-2 higher than the other three seasons of the same growing period; while the grain-filling and amylose accumulation duration reduced 6.2-11.5 d and 9.0-13.9 d in the early season in 2016 than the other three seasons, respectively, and the grain-filling rate and amylose accumulation rate was increased by 53.9%-73.7% and 57.4%-67.9%, respectively. 【Conclusion】Higher temperature and incident radiation in the early stage of grain-filling could reduce the duration of grain-filling and amylose accumulation, and improve the grain-filling rate and amylose accumulation rate. The longer duration of gradual period with grain-filling and amylose accumulation as well as the higher amylose accumulation rate in gradual period in rice grain were the basics of high amylose content in noodle rice. The longer grain-filling duration, the higher amylose accumulation rate, the later happened time of the maximum amylose accumulation and grain-filling rate were benefit to amylose accumulation in grain of noodle rice.
【Objective】The aim of this study was to clarify the interaction effect of high temperature at filling stage and nitrogen fertilizer levels on grain storage protein accumulation and its underlying metabolic mechanism, by investigating the relationship of grain storage protein biosynthesis and its accumulation with the activity of key enzymes involving in nitrogen mobilization and transcriptional expression of various genes that encoded prolamin and pre-glutelin biosynthesis during developing grains.【Method】A two-factor pot experiment, including the combination of two nitrogen fertilizer levels with two temperature regimes, was conducted by using two japonica rice cultivars, namely XS134 and XS 09. The nitrogen fertilizer treatments were conducted at the young panicle differentiation stage of rice plants, with the urea supply of 0.5 g/pot and 2.0 g/pot being considered as low nitrogen (LN) and high nitrogen (HN), respectively. After heading, these rice plants in pots with the same nitrogen fertilizer level (LN or HN) were classified into two groups and then imposed to different temperature regimes in phytotrons, with the daily mean temperature being controlled at 30℃ (34℃/26℃) and 23℃ (26℃/20℃) for high temperature (HT) and normal temperature (NT) as control, respectively. The rice grains under four treatments (LN-NT, LN-HT, HN-NT, and HN-HT) were sampled to examine the impact of high temperature on grain storage protein accumulation and its relation to grain N metabolism under different N levels. 【Result】Both nitrogen fertilizer application at young panicle differentiation stage and HT exposure at filling stage evidently enhanced the relative content of storage protein content in rice grains on dry matter basis. However, HT exposure at filling stage decreased the accumulation amount of grain storage protein on per grain basis, with the dramatically dropping extent for 13-kD prolamin among different protein components. In contrast to NT, HT exposure resulted in a relatively higher ratio of glutelin to prolamin. HT-induced decline in amount of 13-kD prolamin was mainly attributable to the remarkably down-regulating transcripts of prolamin family genes (Pro13, Pro14, and Pro17) under HT exposure. However, the dropping extent of grain prolamin content under HT growth appeared to be smaller for HN relative to LN. Comparatively, HN supply significantly enhanced the amounts of total storage protein, glutelin, and prolamin in rice grains, but it had little impact on the ratio of glutelin to prolamin in rice grains, with the nearly equivalent extent of HN-induced increases in both 37-kD α-glutelin and 22-kD β-glutelin and the relatively stable ratio of 37-kD to 22-kD in glutelin components among different N levels. Furthermore, HN notably enhanced the activities of GS, GOT, GPT in rice grains at the middle-late stages of grain filling, but HN-NT had significantly lower activities of GS, GOT, GPT than HN-NT, implying that HT had an inhibitory impact on HN-induced enhancements in N transferring metabolism in rice grains. Under different N levels, HT resulted in the lowering HMR (heading milled rate) and increasing chalky rate. In contrast, HN-HT had relatively heavier grain weight, higher seed-setting rate, higher HMR and lower chalky grain rate than LN-HT, indicating that N deficiency exacerbated the negative impact of HT on some rice yield and grain quality traits, including grain weight, seed-setting rate, HMR, chalky grain rate, etc.【Conclusion】Nitrogen fertilizer application at young panicle differentiation stage play a regulatory role in the effect of HT exposure at filling stage on storage protein biosynthesis and its accumulation in rice grains. Heavy N application evidently accelerated the glutelin and prolamin biosynthesis in filling grains and significantly enhance the total accumulation amount of grain storage protein both on dry matter basis and on per grain basis, but it contribute to the alleviation for HT-induced decline in 13-kD prolamin biosynthesis and its accumulation amount in rice grains. This occurrence was beneficial to the maintenance of the relatively stable ratio of glutelin to prolamin in HT-ripening grains .
【Objective】The aim of this study was to determine the response of different N recovery efficiency (NRE) varieties to external NH4+concentration, and to explain the mechanism of N uptake difference among rice varieties.【Method】A high-NRE (QL) and a low-NRE (HK) rice variety were cultivated hydroponically at different NH4+concentrations, and the varietal difference of NH4+ absorption at seedling stage were compared by analysis of the root NH4+ absorption rate at the low NH4+ concentration of 0-0.80 mmol·L -1 and the high NH4+ concentration of 1.00-12.96 mmol·L -1, and by calculating the NH4+ absorption kinetics parameter Vmax and Km; The difference of seedling growth between varieties were analyzed by comparing the plant height, tiller number, chlorophyll content, dry matter and N accumulation of aboveground and underground part of rice seedlings growing in different NH4+concentrations, root morphology including total root length, root volume, root surface area, average root diameter, and root tip number were analyzed using the root scanning instrument; The root net fluxes of NH4+ were measured non-invasively using SIET (scanning ion-selective electrode technique), root respiration was measured using a Hansatech oxygen electrode and an oxygraph control system.【Result】(1) In the low NH4+ concentration range of 0-0.8 mmol·L -1, the uptake of NH4+ by QL and HK seedlings stage were in accordance with Michaelich-Menten equation, and the Vmax of high-NRE variety QL was 1.66 times higher than that of low-NRE variety HK. In the NH4+ concentration higher than 1 mmol·L -1, the uptake of NH4+ by rice seedlings kept increasing with the increase of NH4+concentration, and the uptake rate of NH4+ by QL was greater than that of HK at the same NH4+level. (2) The root meristematic zone of both varieties showed a net NH4+influx, while it increased with the increase of NH4+ concentration, and the high-NRE variety QL had greater value than low-NRE variety HK by 42.0%, 71.8% and 63.6% at LN, MN and HN, respectively; The net NH4+efflux in the root elongation zone was showed at LN and HN in the low-NRE variety HK, while it was only showed at HN in the high-NRE variety QL, and 34.30% lower than variety HK. (3) Although an appropriate increase of NH4+ could increase the plant height, tiller number, leaf chlorophyll content, dry matter and N accumulations, while HN inhibited plant growth, especially root growth. The growth of high-NRE variety QL did not show an advantage compared with low-NRE variety HK in the treatment of LN and MN, however, QL had greater tillering rate and dry matter accumulation rate by 65.7% and 31.4% compared with HK during 10-20 days after seeding in HN, respectively. Although the N concentration of root of variety QL was 15.1% lower than that of variety HK, it’s aboveground N accumulation was 23.5% greater, which indicated that QL was more efficient than HK in transporting the N absorbed by roots to the aboveground. 【Conclusion】 It was concluded that compared with the low-NRE variety, the high-NRE variety had more NH4+ transport carriers on the cell membrane of the root system, and the NH4+ absorbed by the root system had a fast assimilation and transport speed, as well as a high tiller rate and dry matter accumulation rate in the seedling stage.
【Objective】The objective of the study was to elucidate the effects of different temperatures and light on the yield of high-quality japonica rice in Huaibei region.【Method】Taking medium-maturing medium japonica rice (MMMJ) Nanjing2728 and Nanjing505, late-maturing medium japonica rice (LMMJ) Nanjing9108 and Fujing1606 as experimental materials, seven seeding treatments were set on May 10 (S1), May 17 (S2), May 24 (S3), May 31 (S4), June 7 (S5), June 14 (S6) and June 21 (S7). The effects of rice yield, growth period, mean daily temperature, accumulated temperature and mean daily radiation under different seeding dates, as well as the correlation between yield and mean daily temperature, accumulated temperature and mean daily radiation were studied.【Result】(1) The yield of rice decreased significantly with the delay of seeding time, the seeding date was postponed every seven days, and the yield of MMMJ and LMMJ was reduced by 0.49 t·hm -2 and 0.63 t·hm -2, respectively. (2) With the delay of seeding time, the number of days from seeding date (SD) to stem elongation (SE), stem elongation (SE) to heading (HE) and the whole growth period showed a decreasing trend. The number days from heading (HE) to maturity (MA) showed an increasing trend, LMMJ S5-S7 could not ripen normally, and the number of days from HE to MA decreased. There was a significant positive correlation between the yield of two types of rice and the days of the whole growth period. (3) With the delay of seeding time, the mean daily temperature increased significantly from SD to SE, and decreased significantly from SE to HE, HE to MA and the whole growth period. (4) The yield of the two types of rice was negatively correlated with the mean daily temperature from SD to SE, and positively correlated with the mean daily temperature from SE to HE, HE to MA and the whole growth period. The accumulated temperature of each growth stage of two types of rice decreased with the delay of seeding time. The seeding date was postponed every seven days, the accumulated temperature in the whole growth period of MMMJ and LMMJ was reduced by 106.6℃ and 123.1℃, respectively. There was a significant positive correlation between the yield of the two types of rice and the accumulated temperature at each growth stage. (5) The mean daily radiation in the whole growth period decreased significantly. There was a significant positive correlation between the yield of MMMJ and the mean daily radiation from SE to HE and the whole growth period, and a positive correlation between the mean daily radiation from SD to SE and from HE to MA. There was a significant positive correlation between the yield of LMMJ and the mean daily radiation from SD to SE, and a very significant positive correlation between it and the yield of the whole growth stage, and a positive correlation between it and the mean daily radiation amount from SE to HE and from HE to MA.【Conclusion】In Huaibei region, the rice yield was more sensitive to temperature than light. The higher the accumulated temperature at each growth stage was, the higher rice yield achieved. In order to ensure the safety and maturity of the two types of high-quality japonica rice, MMMJ and LMMJ should be sown before June 14 and May 31, respectively. When the seeding date was from May 10 to May 24, the two types of high-quality japonica rice yield could be higher.
【Objective】The main purpose of this study was to screen out the inbred japonica rice varieties with high grain yield and high nitrogen efficiency in the middle and lower reaches of Yangtze River, so as to provide a reference for the breeding and production application of high grain yield and high nitrogen efficiency varieties in this area.【Method】105 inbred japonica rice varieties (90 in 2017, 105 in 2018) from the middle and lower reaches of Yangtze River were used as experimental materials, and grain yield, dry matter accumulation, nitrogen uptake and utilization efficiency were determined at maturity stage under the treatment of nitrogen and no nitrogen. Nitrogen recovery efficiency, nitrogen agronomic efficiency, nitrogen physiological efficiency, nitrogen grain yield production efficiency and nitrogen dry matter production efficiency were used as the evaluation indexes of nitrogen absorption and utilization efficiency, and the comprehensive evaluation value of nitrogen efficiency (CEV) of each variety (line) was obtained by using the entropy weight fuzzy synthetic evaluation method. Then, the grain yield-nitrogen efficiency index (GYNEI) was calculated by using CEV and grain yield. According to the GYNEI, the varieties (lines) were classified by the method of cluster analysis.【Result】The tested varieties (lines) were divided into three types, and the average values of grain yield, nitrogen recovery efficiency, nitrogen agronomic efficiency, nitrogen physiological efficiency, nitrogen grain yield production efficiency, nitrogen dry matter production efficiency in Type Ⅰ were highest, while those in Type Ⅲ were lowest. Therefore, Type Ⅰ varieties (lines) were characterized by high grain yield and high nitrogen efficiency, and Type Ⅲ varieties (lines) were characterized by low grain yield and low nitrogen efficiency. According to the screening results, 23 and 27 varieties (lines) were divided into high grain yield and high nitrogen efficiency type in 2017 and 2018, respectively, and 19 varieties (lines), such as Nanjing9108, Nanjing5718, Ningjing7, Sidao15, Yangjing239 and so on, were classified into high grain yield and high nitrogen efficiency type in two years. In addition, stem dry matter weight, leaf dry matter weight, panicle dry matter weight, total dry matter weight, spikelet per panicle, grain yield, panicle nitrogen uptake, total nitrogen uptake of high grain yield and high nitrogen efficiency type (TypeⅠ) were significantly higher than those of Type Ⅱ and Type Ⅲ.【Conclusion】 19 varieties (lines) were preliminarily identified as high grain yield and high nitrogen efficiency varieties (lines), such as Nanjing 9108, Nanjing 5718, Ningjing7, Sidao15, and so on. Compared with the low grain yield and low nitrogen efficiency varieties (lines), the high grain yield and high nitrogen efficiency varieties (lines) showed the characteristics of larger biomass, more spikelet per panicle, higher nitrogen uptake, especially higher panicle nitrogen uptake. These results could provide a reference for the selection of inbred middle-ripe japonica rice varieties in the middle and lower reaches of Yangtze River, and also provided materials for the study of the synergistic mechanism of grain yield and nitrogen efficiency.
【Objective】The effect of global warming on rice production has attracted much attention, leading to changes on planting area, cultivated practices and rice varieties. Thus, it is necessary to clarify the responses of rice yield and its formation to warming under different planting patterns.【Method】During 2017 to 2018, we selected two varieties (Nanjing 9108 and Nanjing 46), two planting patterns (simulating machine transplanting and mechanized direct sowing), and three temperature treatments, including normal temperature (NT) as control, moderate temperature (average increase 2℃, MT) and extreme high temperature stress (average increase 5℃, HT), to study the effects of elevated temperature on rice yield, yield composition, assimilation transport and the characteristics of photosynthesis production.【Result】Under MT and HT treatments, the decreasing yields of Nanjing 9108 and Nanjing 46 under transplanting were less than that under direct sowing, while the yield of the long-growth variety Nanjing 46 had smaller decline. The growth rate of the spike dry material showed the trend of NT>MT>HT. The amount and rate of dry matter translocation from rice stem and leaves to spike decreased with the increase of temperature, and the decreasing effects on Nanjing 9108 was greater than that for Nanjing 46. Moreover, after 21 days of heading to maturity, the SPAD of flag leaf increased with elevated temperatures significantly. And the lowest net photosynthetic rate of flag leaf was found under HT at 14-21 days after heading period, while the highest was found at 35 days after heading period. In addition, The stomatal conductance and transpiration rate of flag leaf showed the increasing trend of NT>MT>HT, and the difference was more significant in the later growth stage. The path analysis indicated that the importance of yield components on yield was in the order of filled grain percentage>1000-grain weight>number of panicles>spikelet number per panicle, and all the elevated temperature treatments had negative impacts on yield components, with the greatest effect (-0.819) on filled grain percentage. The relevant analysis showed that the total weight of dry matter at maturity, the amount of translocation were significantly positively correlated to the yield composition factor (except the number of spikes) and the filled grain percentage of primary and secondary branches under MT and HT. 【Conclusion】Increasing 2℃ to 5℃ at the initial heading stage significantly reduced the filled grain percentage of rice, which led to the decrease of rice yield. From the perspective of photosynthetic characteristics, temperature rising reduced the rate of dry matter transported to spikes and declined dry matter accumulation in spikes, increasing SPAD of rice flag leaves in late growth period and thus prolonging the green holding time, which could inhibit the translocation from source to sink. Overall, we suggest that long-growth period varieties with proper plant patterns could have better resistance to elevated temperatures, which could be adaptive to the global warming.
【Objective】The aim of this study was to probe the response characteristics of the grain yield and quality of southern high-quality eating late indica rice to irrigation management.【Method】 Field experiments irrigation were conducted at Shanggao Experimental Base of Jiangxi Agricultural University in 2018 and 2019. The different irrigation management of the field treatments was conducted as follows: conventional irrigation (CK), constant flooding irrigation (CFI) and alternate wetting and drying (AWD). The two indica rice cultivars, including Taiyou 871 for good-quality eating rice and Rongyouhuazhan for common eating quality rice, were used to analyze and determine water use efficiency, grain yield and rice quality. 【Result】 Different irrigation managements had a significant effects on the grain yield components quality of the two indica rice cultivars, and the trend was consistent over the two years, but there were differences among the cultivars. Compared with CK and CFI, the total water use efficiency under AWD in two years was increased by 18.2%-62.5% and 41.2%-91.7%, respectively. Compared with CK, AWD and CFI showed a trend to increase grain yield of the two cultivars, but the grain yield had no significant change in the high-quality eating indica rice cultivars. Only in 2018, the yield of the common indica rice cultivars increased significantly under AWD treatment, mainly because the number of grains per ear increased significantly. AWD was beneficial to the rice processing quality. Compared with CK and AWD, CFI significantly reduced the chalky rate and chalkiness, which was beneficial to the improvement of the rice appearance quality. There were annual differences in the amylose content of the different eating quality cultivars under different irrigation managements. In 2019, compared with CFI, AWD significantly increased the amylose content of the two cultivars, at the same time, AWD also significantly increased gel consistency, peak viscosity and breakdown, decreased setback, and improved the palatability of the two cultivars in two years. Compared with CK, CFI significantly increased protein content of the two cultivars. However, the effects of irrigation management on amylose, nutritional quality and RVA characteristics of high-quality eating indica rice cultivars were higher than those of common eating quality indica rice cultivars. 【Conclusion】 Alternate wetting and drying improved water use efficiency of two cultivars, which was beneficial to increase high-quality eating late-season indica rice yield and improve processing quality, but was not conducive to the improvement of appearance quality. At the same time, alternate wetting and drying could reduce setback and protein content, increase gel consistency, peak viscosity, trough viscosity and breakdown to improve the palatability of cooked rice, but constant flooding irrigation was beneficial to improving the appearance quality of rice. Alternate wetting and drying could be used as a high-quality and high-efficiency water-saving irrigation model for high-quality eating late-season indica rice in South China.
【Objective】A formal experiment was conducted to reveal the effects of dissolved oxygen (DO) concentration on root growth at the tillering stage and nitrogen utilization of rice, so as to provide a theoretical basis to the rice oxygen nutrition and high-yield cultivation.【Method】The formal experiment was conducted at China National Rice Research Institute in 2016. Three rice varieties, including ZZY 1(lowland rice), IR45765-3B (deep-water rice) and ZH 221 (upland rice), were grown in hydroponic condition with different DO concentration (T1-1 mg·L -1, T2-3 mg·L -1, T3-5.5 mg·L -1, T4-7.5 mg·L -1 and CK-natural growth) controlled by on-line test control system (KUNTENG Q45D, America). The portable dissolved oxygen meters (YSI 550A, America) was used to examine the oxygen concentration in the nutrient solution.【Result】(1) The results showed that the decrease rate of total nitrogen content in whole concentration nutrient solution decreased with the increasing of DO concentration, while the change of ammonium salt content showed the opposite tendency under different DO concentrations. At the same determination time, the nitrate content increased with the increasing of DO concentration. Nitrite content was extremely low and was unstable in whole concentration nutrient solution. (2) Compared with CK, the root activity of three rice cultivars increased in T2, while the root vigor decreased under T1 and T4. The longest root length of three rice cultivars was elongated with increasing of DO concentration, while the total length, total surface area, volume and dry matter were reduced under T1 and T4. The root morphological indexes and dry matter accumulation of ZZY 1 and IR45765-3B under T2 were higher than that of CK. (3) The nitrogen content of three rice cultivars decreased gradually with the increasing of DO concentration at jointing stage, which showed an opposite tendency at full heading stage and full ripe stage. Compared with CK, the nitrogen accumulation of three varieties increased under T2 during the whole growth period. The nitrogen uptake of rice decreased under T3 and T4, while the proportion of nitrogen accumulation from full heading stage to full maturity stage of rice increased significantly. At full ripe stage, nitrogen accumulation of three rice varieties increased 2.3%-7.3% under T2 compared with CK, and decreased 0.7%-3.6%, 3.6%-8.5% and 15.0%-27.1%, respectively, in T1, T3 and T4. (4) The dry matter accumulation and yield of three rice varieties were T2>CK>T1>T3>T4 under different DO concentrations at full ripe stage. In all treatments, the nitrogen dry matter production efficiency was the highest under T1. Compared with CK, T2 improved the harvest index and nitrogen harvest index of three rice varieties, which were declined under other DO concentrations. The nitrogen grain production efficiency of ZZY 1 and IR45765-3B under T1 were significantly lower than that of CK, and there was no significant difference in ZH 221.【Conclusion】A moderate increase of DO concentration could improve the formation of rice root system under the condition of water cultivation, increase the dry matter and nitrogen accumulation, and improve the nitrogen utilization efficiency and yield of rice. Both hypoxia and hyperoxia stress could inhibit the root activity of different ecotypes of rice, and reduce the nitrogen uptake. Besides, the tolerance on the oxygen stress of upland rice was stronger than that of lowland rice and deep-water rice.
【Objective】 Simplified nitrogen managements (SNMs) are labor saving methods and could make more profits in rice (Oryza sativa L.) cultivation. In view of labor shortage, high labor cost and low fertilizer utilization in rice cultivation of China, the aim of this study was to explore a simplified and efficient application of nitrogen featured by “one basal-dressing and one top-dressing”, so that the amount and frequency of nitrogen application could be reduced, and the profit of rice planting could be improved. 【Method】In order to study the effects of SNMs on the grain yield, dry matter production, nitrogen use efficiency, and grain quality of double-cropping rice in South China, the field experiment was conducted by a conventional indica rice variety of Wu-Shan-Si-Miao, which was designed by a completely randomized block with four replicates. In 2018, 6 treatments were established, i.e. no nitrogen (N0), three-control fertilization (TC), TC with nitrogen reduction (RTC), and 3 simplified nitrogen managements (SNM1, SNM2, and SNM3). In 2019, 6 treatments were also established, i.e. no nitrogen (N0), three-control fertilization (TC), famers’ fertilizer practice (FP), and 3 simplified nitrogen managements (SNM2, SNM4, and SNM5). 【Result】 In the later growing season of 2018, the grain yield of SNM2 was not significantly different from that of TC, but the yields of both treatments were significantly higher than those of RTC, SNM1, and SNM3. In 2019, the grain yields of SNM2, SNM4 and SNM5 were also not significantly different from that of TC. However, compared with FP, the yields of those treatments were increased by 7.36%-7.51%, which was mainly due to the spikelet number per panicle was improved in 2019. And the panicle numbers, spikelet number per panicle, seed setting rate, and 1000-grain weight of SNM2 were not significantly different from TC (except for 1000-grain weight in 2019) for both seasons. In 2018, the nitrogen recovery rate (RE), agronomy use efficiency (AE), physiological use efficiency (PE), nitrogen harvest index (NHI) of SNM2 were all not significantly differed from that of TC, while the partial factor production (PFPN) of SNM2 was significantly higher than that of TC, and the RE, AE, and PFPN of the SNM1 and SNM3 were obviously lower than that of SNM2. In 2019, the 5 nitrogen utilization indexes (RE, AE, PE, NHI and PFPN) of the 3 SNMs were not significantly different with those of TC, but the RE, AE and PFPN of those treatments were all significantly higher than that of FP. The number of spikelets per unit area, biomass, and nitrogen uptake of the SNMs were all higher than those of FP. In addition, the chalky rice rate of SNM2 was significantly lower than that of TC, but other grain quality of SNMs was not significantly different from that of FP and TC in 2018. 【Conclusion】 The grain yield and nitrogen use efficiency of SNM2, which had 10% less nitrogen application and with only basal application and one topdressing in nitrogen management, was similar with TC. However, SNM2 had significantly higher grain yield and nitrogen use efficiency than FP. Additionally, the appearance quality of SNM2 was significantly improved, while the milling quality, cooking and eating quality were not significantly changed. Thus, it could be widely adopted in rice production in South China for its simplified cultivation.
【Objective】In this experiment, the mixed controlled-release nitrogen (N) fertilizer (composed of two controlled-release N fertilizers with different release periods) and conventional N fertilizer were mixed and then applied as base fertilizers at one time under mechanical pot-seedling transplanting, with a view to select the optimal mixed controlled-release N fertilizer treatment that matched the nutrient absorption of late mid-season japonica rice with good taste quality, so as to provide a scientific basis for high-yield and simplified fertilization of that type of rice under mechanical pot-seedling transplanting.【Method】The experiment was carried out in the rice season of 2018-2019 (May-October). The two late mid-season japonica rice and more panicles cultivars with good taste quality, including Nanjing 9108 and Fengjing 1606, were used as materials under the pure nitrogen condition of 270 kg·hm -2. A mixed controlled-release N fertilizer and a conventional nitrogen fertilizer were combined at a ratio of 5﹕5, and the mixed controlled-release N fertilizer consists of two kinds of controlled-release fertilizers with different release period at a ratio of 4﹕1. Six combinations were set up, including 60 d + 40 d, 60 d + 80 d, 80 d + 60 d, 80 d + 100 d, 100 d + 80 d, and 100 d + 120 d, and conventional urea split fertilization (CK) was used as a control. Then, the yield, population quality index and characteristics of nitrogen absorption and utilization were measured.【Result】The results showed that, compared with CK, the yield of Nanjing 9108 and Fengjing1606 under 100 d+80 d treatment were increased by 4.66% and 4.29% on average for two years, respectively. The increase of grain yield was due to the significant increase in effective panicles per unit area and total spikelet per unit area, and grain number per panicle and filled-grain percentage had no significant difference between 100 d+80 d, 100 d+120 d treatments and CK. The grain yield under 100 d+120 d treatment was next to 100 d+80 d treatment, except for the 100 d+120 d treatment of Nanjing9108 in 2019. There was no significant difference in yield between 80 d+60 d, 80 d+100 d treatments and CK for two years. Compared with CK, the yield under 60 d+40 d and 60 d+80 d treatments was significantly reduced. From sowing to jointing, the group N accumulation under the mixed controlled-release N fertilizer treatments increased, compared with CK, with an average increase of 14.86%, which promoted the occurrence of group tillers and the simultaneous increase in LAI and net assimilation rate, improved photosynthetic productivity, and then increased dry matter accumulation. From jointing to heading, the N accumulation and dry matter accumulation of only 100 d+80 d, 100 d+ 120 d treatments were at the highest level with CK, which increased by 47.02%-55.01% and 14.52%-18.15% respectively, compared with the lowest 60 d+40 d treatment. Compared with the treatments of 100 d+80 d and 100 d+120 d, the net assimilation rate under CK was increased relatively, but the LAI at heading stage decreased significantly. From heading to maturity, the nitrogen accumulation under 100 d+120 d treatment was significantly higher than other treatments, which was increased by 9.23%-22.03% compared with CK. However, the dry matter accumulation under 100 d+80 d and 100 d+120 d treatments was at the highest level, which was significantly increased by 5.44%-8.58% compared with CK, which might be due to that N release under 100 d+80 d and 100 d+120 d treatments, and it could improve photosynthetic leaf area and net assimilation rate relatively coordinately, resulting in relatively sufficient photosynthetic production after heading; While the net assimilation rate of CK was relatively high, but the photosynthetic leaf area was relatively insufficient. With regard to N use efficiency, N partial factor productivity (NPFP) and N agronomy efficiency (NAE) under 100 d+80 d treatment respectively was increased by 3.90%-4.92% and 9.42%-11.93%, compared with CK; The apparent N use efficiency (ANE) under 100 d+80 d and 100 d+120 d treatments was increased by 5.29%-7.21% and 5.79%-8.51%, respectively, compared with CK.【Conclusion】The N release under the 100 d + 80 d and 100 d + 120 d treatments was most consistent with nutrient absorption of Nanjing 9108 and Fengjing 1606, which led to the formation of high-yield population and could be used as a nitrogen fertilizer management method for high-yield and simplified fertilization of late mid-season japonica rice with good taste quality by mechanical pot-seedling transplanting.
With the decrease of high-quality labor in rural areas, the rising of labor cost and the development of large-scale production, direct seeding as a simplified rice planting technology was widely used continuously. Therefore, the promotion of its stable or increased yielding was of great significance in ensuring food security in this country. According to the growth characteristics of direct seeding rice in multiple cropping area of South China, a concept of growth constrained direct seeding rice was put forward. In other words, the rice emergence and seedling growth under direct seeding were significantly imitated and affected by multiple adversities, which were caused by 100% returning the previous crop straw to the field and lower quality of ploughing and sowing in short crop rotation time. And the rice later sowing date under direct seeding method than transplanting rice shortened the plant growth duration, reduced the utilization of temperature and light resources, and imitated the rice growth, as affected by the previous crop. Thus the yield of direct seeding rice was not high and instable. For now, this kind of growth constrained direct seeding rice was widely used in production and restricted the balanced production increase in large area. Therefore, the stable yield cultivation methods of growth constrained direct seeding rice were explored in this paper. The comparison experiments were carried out with a representative japonica rice variety in consideration of more panicles and more grains in Jiangsu, and the treatments of 1.2 million, 2.4 million and 3.6 million basic seedlings per hectare, under representative simplified cultivation and sowing methods on a large scale. With the basic seedlings treatments, three cultivation ways of growth constrained direct seeding rice were formed respectively, including panicles formed with more tillers, panicles formed with both stems and tillers, and panicles formed with more stems in the experiment. The characteristics of photosynthetic matter production, yield and quality of different types of rice were systematically analyzed. “The basic seedlings of rice should be increased appropriately to increase the ratio of main stem to panicle and produce more spikelets with sufficient main stem, and then the dry matter in middle and late growth duration would be produced and accumulated more and more” was tentatively believed as an effective cultivation way for stable yield, high quality and efficiency of growth constrained direct seeding rice. The key techniques of stable yield cultivation and reasonable development suggestions of growth constrained direct seeding rice were also introduced in this paper.
【Objective】The aim of this study was to investigate using the big panicle advantage of indica hybrid rice to obtain a high-yield under the potted machine-transplanted and combined application of slow release nitrogen (N) fertilizer and urea, and to explore N utilization characteristics of the potted-seedling machine-transplanted hybrid indica rice in the Southwest rice region, so as to provide the theoretical and practical basis for the technology of saving-fertilizer and high-yield of machine-transplanted hybrid rice seedling in China. 【Method】 A 2-year split-plot experiment (2016-2017) was conducted in Meishan, Sichuan province, China. In the experiment, two machine-transplanted methods was set, including potted-seedling (M1) and blanket-seedling (M2), and four N treatments were set, including 150 kg·hm-2 slow release N fertilizer (SRNF) as a base (N1), 105 kg·hm-2SRNF + 45 kg·hm-2 urea as a base (N2, SBUB), 105 kg·hm-2 SRNF as a base + 45 kg·hm-2 urea at the panicle initiation stage (N3, SBUP), and another treatment without N fertilizer as a control (N0). F-you 498 was the experimental variety, and the blanket-seedling machine-transplanted method and 100% slow-release N fertilizer as base were the reference. The N utilization characteristics of hybrid indica rice under the potted-seedling machine-transplanted and slow and rapid N fertilizer combined application were studied.【Result】Compared with the blanket-seedling rice, the potted-seedling significantly accelerated the N absorption rate by 0.49-1.33 kg·hm-2·d-1 from elongation stage to heading stage; The potted-seedling improved N transportation and N transportation efficiency of stems and leaves, and the contribution rate of N transportation from heading to maturity; The potted-seedling increased the N accumulation at heading and maturity by 12.63% and 5.20%, respectively; The potted-seedling increased N use efficiency for biomass production and grain yield, and N harvest index by 8.19-11.39, 0.66-5.72 and 5.41-6.42 percentage points, respectively; The potted-seedling improved N agronomic efficiency, N physiological efficiency, and partial factor productivity by 12.62%, 11.94% and 8.69%, respectively; The potted-seedling improved the effective panicles and spikelets per panicle, and improved the yield on 1 042.4 kg·hm-2 and 722.3 kg·hm-2, and increased by 10.3% and 7.2%, in 2016 and 2017, respectively. Under the potted-seedling, compared with 100% SRNF as base, SBUB decreased the N accumulation at heading stage and maturity stage, accelerated the N absorption rate and N accumulation from sowing stage to elongation stage, but decreased them from elongation to heading; N recovery efficiency, N physiological efficiency, the spikelets per panicle and spikelets per unit area under SBUB were significantly decreased, then the mean yield of 2 years decreased by 3.66%. Conversely, compared with 100% SRNF as base, SBUP increased the N accumulation at heading and maturity by 2.34% and 1.80%, respectively; SBUP improved the N absorption rate by 0.60 kg·hm-2·d-1 and N accumulation by 18.01 kg·hm-2 from elongation to heading; N recovery efficiency under SBUP were improved by 2.84 percentage points, and N agronomic efficiency, N physiological efficiency, and partial factor productivity by 12.54%, 7.91% and 52.55%, respectively; SBUP improved the spikelets per panicle and spikelets per unit area, then the yield improved by 4.61%.【Conclusion】Compared with the blanket-seedling, the potted-seedling had obvious advantages on N utilization efficiency, and SBUP could further enhance its N absorption and transfer capacity, then improved indica hybrid rice yield.
【Objective】In order to find the technical pathway to improve both grain yield and resource use efficiency in rice production, this study compared high yield and high efficiency cultivation models integrated by various cultivation measures. 【Method】Four cultivation models were established in a double rice-cropping region in south China, i.e., nitrogen-free cultivation model (CK: 62.5 and 50.0×104 seedlings·hm-2 in early and late season, respectively; 0 kg N·hm-2 in both early and late seasons), local farming cultivation model (FM: 62.5 and 50.0×104 seedlings·hm-2 in early and late season, respectively; 150 and 165 kg N·hm-2 in early and late season, respectively, with 70% as basal fertilizer and 30% as tillering fertilizer in both seasons), high yield and high-efficiency cultivation model (T1: 135 and 112.5×104 seedlings·hm-2 in early and late season, respectively; 120 and 210 kg N·hm-2 in early and late season, respectively, with 50% as basal fertilizer, 30% as tillering fertilizer, and 20% as panicle fertilizer in both seasons; 5 kg Zn·hm-2 as basal fertilizer in both early and late seasons), and more high-yield and high-efficiency cultivation model (T2: 176 and 137.5×104 seedlings·hm-2 in early and late season, respectively; 120 and 240 kg N·hm-2 in early and late season, respectively, with 40% as basal fertilizer, 30% as tillering fertilizer, and 30% as panicle fertilizer in both seasons; 5 kg Zn·hm-2 and 1.8 t·hm-2 organic fertilizer as basal fertilizer in both early and late seasons; bed cultivation in both early and late seasons). Solar radiation and nitrogen use efficiency and yield of rice were compared among these four cultivation models.【Result】 Average annual yield under T2 was 15.1 t·hm-2, which was significantly higher than those under T1 and FM. Compared with FM, the yield of early indica rice and late japonica rice under T2 was increased by 13.3% and 24.9%, respectively. T2 significantly increased panicle number per unit land area and consequently spikelet number per unit land area for both early indica rice and late japonica rice. Average annual yield under T1 was 13.3 t·hm-2, which was higher than that under FM. Compared with FM, the yield of late japonica rice was increased by 9.5% while the yield of early indica rice was slightly decreased under T1. In the early season, dry matter accumulation at maturity under T2 was 12.30 t·hm-2, which was significantly higher than those under T1 and FM. The crop growth rate from transplanting to flowering was significantly higher under T2 than under T1 and FM. In the late season, dry matter accumulation at maturity under T2 was 17.96 t·hm-2, which was significantly higher than those under T1 and FM. The crop growth rate from flowering to maturity was higher or significantly higher under T2 than under FM and T1. Solar radiation use efficiency under T2 in early season and late season was 1.05 and 1.25 g·MJ-1, respectively, which was improved by 31.7% in the early season and 63.4% in the late season as compared to FM. Nitrogen agronomy use efficiency under T2 in early season and late season was 28.8 and 14.7 kg·kg-1, respectively, which was enhanced by 61.6% in the early season and 31.9% in the late season as compared to FM. 【Conclusion】Based on ecological characteristics of double-cropped rice in south China, 10%-20% increases in rice yield as well as solar radiation and nitrogen use efficiency can be achieved by the adoption of T2 model which is integrated by increasing seedling number and reducing nitrogen rate, improving soil oxygen content by bed cultivation, and enhancing the activity of grain filling by other cultivation measures such as Zn fertilizer.
【Objective】 This study aimed to understand the yield formation characteristics and water use efficiency (WUE) of indica/japonica hybrid rice (IJHR) cultivar and their physiological bases under alternate wetting and soil drying (AWD) regime.【Method】The field experiment was conducted at Huangtianfan Experimental Farm which belonged to China National Rice Research Institute, Hangzhou, Zhejiang province, Southeast China, in 2018 and 2019. Two newly-bred IJHR cultivars, Yongyou 1540 and Chunyou 927, and two local high-yielding japonica hybrid rice (JHR) cultivars, Changyou 5 and Jiayou 5, were field grown. Two irrigation regimes, conventional irrigation (CI) and AWD, were imposed from 7 days after transplanting to maturity. The goals of this study were to investigate the effects of AWD on the grain yield and WUE of IJHR and its physiological bases. 【Result】Compared with those under CI regime, the grain yields of JHR cultivars were significantly decreased by 12.3%-12.8% under AWD regime, whereas the difference in grain yields of IJHR cultivars was not significant between CI and AWD regimes. Compared with the CI regime, AWD significantly reduced the amount of irrigation water and significantly increased WUE by 5.9%-8.3% and 13.7%-16.8% in JHR and IJHR cultivars, respectively. In comparison with JHR cultivars, IJHR cultivars showed greater tillering capacity, larger sink size and higher grain filling rate, higher leaf area duration and crop growth rate from heading to maturity, higher root oxidation activity, leaf photosynthetic rates, and activities of sucrose synthase and adenosine diphosphate-glucose pyrophosphorylase in grains at the first and second soil drying periods as well as re-watering periods after heading.【Conclusion】IJHR cultivars could obtain higher grain yields and higher WUE than JHR cultivars under AWD regime. Stronger physiological activities of root, including higher root oxidation activity at the first and second soil drying periods as well as re-watering periods after heading, and above ground plants, including higher leaf area duration, crop growth rate from heading to maturity, greater leaf photosynthetic rates, and activities of sucrose synthase and adenosine diphosphate-glucose pyrophosphorylase in grains at the first and second soil drying periods as well as re-watering periods after heading, contributed to their better yield performance and higher WUE of IJHR cultivars under AWD regime.
【Objective】The aim of this study was to identify the differences of yields among various high-yield varieties of double-cropping rice with machine-transplanted under the early season and the common characteristics of super-high yield varieties in the Northern Margin Area of Yangtze River. 【Method】In this study, nine pre-screening high yield varieties were compared for their yield formation, including dry matter accumulation (DMA), leaf area index (LAI) and the intercepted photosynthetically active radiation (IPAR), in field experiments in the early season of 2018 and 2019 in Lujiang county, Anhui province, China.【Result】The rice grain yields varied across the different high-yield varieties. Through cluster analysis, it could be further divided into three yield types: super-high yield (9.1-9.5 t·hm -2), higher yield (8.1-8.6 t·hm -2) and high yield (7.6-7.8 t·hm -2). Compared with higher yield and high yield varieties, the super-high yield varieties showed more spikelets per panicle, total spikelets and 1000-grain weight. The average daily yield of super-high yield was 82.4 kg·hm -2·d -1, 10.2% and 19.8% higher than that of higher yield and high yield, respectively. DMA was the main reason for the differences in yield among various varieties. The DMA of super-high yield varieties was 18.3%-21.4% higher than that of higher yield and high yield varieties from panicle initiation stage to maturity stage. Super-high yield varieties showed higher IPAR and the photosynthetically active radiation use efficiency (PUE) was related to the higher LAI and sink. IPAR in panicle initiation and heading stage was significantly positively correlated with the spikelets per panicle and 1000-grain weight, respectively. However, the super-high yield varieties showed higher response to the IPAR. The grain weight/leaf of super-high yield varieties was 4.1%-11.3% higher than higher yield and high yield varieties, which was related to the higher PUE from panicle initiation stage to maturity stage. 【Conclusion】 The common characteristics of super-high yield early rice varieties (>9.0 t·hm -2) were higher LAI (panicle initiation stage 5.6-6.0, heading stage 7.1-7.3), higher spikelet numbers per panicle (124-132), higher 1000-grain weight (25.8-27.0 g) and higher average daily yield (80.8-83.7 kg·hm -2·d -1) under machine-transplanted in the Northern Margin Area of Yangtze River.
【Objective】This study aimed to investigate the characteristics of nitrogen (N) absorption and utilization of machine-transplanted indica hybrid rice with different daily yield types, so as to provide a theory and practical basis for the high-yield cultivation and breeding of machine-transplanted medium-indica hybrid rice. 【Method】 The 20 medium-indica hybrid rice varieties bred in Southwest China were clustered into three types (high daily yield, medium daily yield, and low daily yield) based on their daily yields, and then the differences in N accumulation, distribution, redistribution, and utilization characteristics between different daily yield types, as well as their relationships with daily yield were studied. 【Result】(1) There were markedly differences in N accumulation characteristics of different daily yield types. Compared with medium and low daily yield types, N accumulation percentage before the jointing stage was decreased, meanwhile, the N concentration of organs and shoot at the jointing and heading stages, and the N concentration of panicle and shoot at the maturity stage, as well as the N accumulation from the jointing to heading in 2017 and N accumulation rate after the heading in 2018 were increased by high daily yield type, which contributed to the 3.70%-5.97% and 16.57%-18.63% improvement in total N accumulation of shoot, respectively. (2) High daily yield type increased the N distribution percentage of stem plus sheath and panicle at the heading stage and maturity stage, respectively, but reduced that of leaf lamina at the maturity stage. High daily yield type also increased the N redistribution amount of vegetative organs (especially the stem plus sheath). (3) The N use efficiency for biomass production was improved by low daily yield types; however, both N harvest index and partial factor productivity of applied N were increased by high daily yield types. (4) The correlation analysis indicated that the N concentration of shoot at each growth stages, N accumulation amount and rate from the jointing to heading, as well as the N distribution of stem plus sheath at the heading stage and partial factor productivity of applied N were significantly increased with daily yield, while the N accumulation percentage before the jointing stage, N distribution percentage of leaf lamina at the maturity stage, and the N use efficiency for biomass production were decreased with daily yield. 【Conclusion】On the whole, the higher N accumulation amount and rate from jointing to heading, and N distribution percentage of stem plus sheath at the heading stage, as well as greater N distribution percentage of stem plus sheath and panicle respectively at the heading and maturity stage could be selected as the N absorption and utilization characteristics of rice varieties with higher daily yield.
