【Objective】Quantitative analysis of the contribution of main management factors to grain yield is of great importance for narrowing yield gap of maize (Zea mays L.). 【Method】 To clarify the individual contribution rate of main management factors to maize yield, the present study analyzed data from 114 literatures published after 2000, which focused on crowding tolerance of hybrids, plant density, soil tillage method, nutrient management and leaf disease control in spring maize production of North China. Meanwhile, a 2-year field study with an incomplete factorial design with foregoing 5 factors was conducted in tow fixed locations, to verify the result of literature review and furtherly assess the priority of management optimization for reducing yield gap. 【Result】 The results of literature review was consistent with that of management-factor alternative test in field. The priority of 5 management factors was plant density, nutrient management, crowding tolerance of hybrids, and leaf disease control and soil tillage method, which contributed to yield by 12.6%, 9.2%, 6.7%, 6.3% and 5.5%, respectively. Similarly, the contribution rates to PFPN of them were 16.7%, 4.1%, 3.4%, 3.8% and 3.3%, respectively. Yield gap induced by each management factor was mainly attributed to mass productivity and sink capacity, which were initially increased along with mean leaf area index (MLAI). When MLAI exceeded optimum value, enhancing radiation efficiency and grain producing efficiency by optimizing assimilative capacity was of great importance for closing yield gap.【Conclusion】Concurrent enhancing yield and resource use efficiency by 15% to 20% could be reached easily through optimizing plant density and nutrient management. However, synchronously enhancing yield and resource use efficiency by more than 30% to 50%, four or all five management factors should be optimized systematically.
【Objective】In order to provide a theoretical basis for the further improvement of the yield and nutrient efficiency of different maize production levels, the effects of the increasing and decreasing measures on the yield and nutrient efficiency of maize under different technical modes were explored, and the technical priorities were clarified. 【Method】 By investigating the yield level and technical mode of farmers, high-yield and high-efficiency, as well as super high yield, it was clear that planting density, cultivation measures, nitrogen management and varieties were the main measures to limit the yield and efficiency improvement of maize at different production levels. On the basis, three technical models of super high yield (SH), high-yield and high-efficiency (HH) and farmer household (FP) were set up. According to the measure factors under different technical modes, the split area experiment was carried out, in which the tillage method was the main plot, the variety was sub-plot, the nitrogen fertilizer management was sub-sub-plot, and the density was sub-sub-sub-plot.【Result】Under the FP model, the priority order of technical measures to yield contribution was nitrogen management, planting density, soil tillage, and variety, while the contribution rate to yield was 9.9%, 6.0%, 4.4% and 2.5%, respectively. Under the HH model, the priority order of cultivation measures to yield contribution was planting density, nitrogen management, soil tillage, and variety, with the contribution rate of 7.7%, 5.2%, 4.5% and 3.5%, respectively. Under SH mode, the priority order of cultivation measures to yield contribution was planting density, soil tillage, nitrogen management, and variety, with the contribution rate of 8.9%, 7.3%, 6.5% and 4.3%, respectively. Among the three models, the contribution rate of cultivation technical factors to nitrogen efficiency from high to low was nitrogen management, planting density, soil cultivation and variety. Among them, the contribution rate of nitrogen management, planting density, soil tillage and variety to nitrogen efficiency was 30.5%, 6.0%, 4.4% and 2.5% in FP mode, 19.7%, 7.7%, 4.7% and 4.5% in HH mode, 25.4%, 8.3%, 6.5% and 4.5% in SH mode, respectively.【Conclusion】There was no fixed priority order for the contribution of technical factors to the yield. The formation of yield gap under different management levels was affected by multiple factors, and the technical factors had synergistic effect. Under the management of farmer's level, the contribution rate of nitrogen management to the yield ranked first, while the contribution of planting density and soil tillage to the yield was greater under the higher management level. However, the nutrient efficiency gap was mainly caused by nitrogen management, and the contribution rate of nitrogen management to nutrient efficiency ranked the first at different yield levels.
【Objective】The objective of this study was to clarify the regulating effect of improved cultivation modes on canopy structure and population production of spring maize, and the contribution for grain yield increasing in the future.【Method】Maize cultivar “Zhongdan 909” was used as experimental materials, under 105 000 plants/hm2 as planting density, setting four cultivation modes via the combination among different cultivation measures, which were subsoiling tillage (S), wide-narrow rows (W), and chemical regulator (C): (1) Traditional mode (rotary tillage 20 cm, plus 60 cm uniform plant spacing; RU), (2) Tillage improved mode (subsoiling tillage 35 cm, plus 60 cm uniform plant spacing; SU), (3) Canopy improved mode (traditional rotary tillage 20 cm, plus 80+40 cm plant spacing, and foliar spraying ECK; RWC), and (4) Synthetically improved mode (subsoiling tillage 35 cm, plus 80+40 cm plant spacing, and foliar spraying ECK; SWC). Investigated based on the differences of canopy continual sections (vertical), light distribution, photosynthesis, activity of the key sucrose synthetase enzyme, the dry matter accumulation, and grain fulling. 【Result】Compared with the traditional mode (RU; CK), the green leaf weight of tillage improved mode (SU) increased obviously, and the height and ear height of population reduced more than 30 cm under the canopy improved conditions (RWC and SWC), but the regularity degree of maize population were declined markedly; The leaves vertical distribution more uniformly, looked like “spindle type”, were the vertical height of 180-240 cm light interception and was significantly less than traditional mode (8%-37%), while the ear position (120-180 cm) was significantly higher than traditional mode (44%-129%); However, the leaves distribution of RU and SU treatments were more like “funnel type”, leaves were concentrated in the upper layer. Tillage and canopy improving synergistically could improve the canopy vertical structure significantly, promoted the chlorophyll content, net photosynthetic rate of leaves at ear position and under ear position, as well as enzyme activity own in the sucrose metabolic of ear position leaf. Maintaining the physiological activity of canopy leaves in the late growth stage, which would prolong the active accumulation period of dry matter more than 10 days. 【Conclusion】Synthetical improved mode (SWC) significantly increased the light transmission and C metabolic activity of leaves via changing the biomass spatial distribution, which promoted the canopy productivity of the functional leaves meanwhile the grain filling, then the grain yield were enhanced dramatically.
【Objective】The objective of this experiment was to study the effects of planting density on canopy senescence, radiation use efficiency and yield of different plant types maize, so as to provide technical support for cultivation of high yield and high efficiency of spring maize in northern Shaanxi. 【Method】 In 2017 and 2018, the field experiments were conducted by using two maize hybrids, including Shaandan 609 (compact) and Shaandan 8806 (flat), with four planting density treatments, including 45 000, 60 000, 75 000 and 90 000 plants/hm2. Canopy light and nitrogen distribution, leaf senescence, nitrogen accumulation, dry matter production, radiation use efficiency and yield components were determined. 【Result】 Shaandan609 and Shaandan8806 reached the highest grain yield at 90 000 plants/hm2 (13 824 kg·hm-2) and 60 000 plants/hm2 (9 566 kg·hm-2), respectively. Compared with 45 000 plants/hm2, the average kernels per ear (17.8% and 30.1%) and 100-kernels weight (15.2% and 19.6%) of Shaandan609 and Shaandan 8806 both reduced under 90 000 plants/hm2. The canopy light interception and leaf nitrogen concentration of the two varieties showed: the upper layer>the middle layer>the lower layer. With the increase of planting density, the fraction of the photosynthetically active radiation interception (FIPAR) and leaf nitrogen concentration increased at upper layer, but decreased at the mid and lower layer. When the density increased to 90 000 plants/hm2, the FIPAR at middle and upper canopy and the lower canopy of Shaandan 8806 were 8.8% and 70.6% lower than Shaandan 609, respectively, and the leaf nitrogen concentration at middle and upper canopy layer and lower canopy of Shaandan 609 were 16.0% and 40.5% higher than Shaandan 8806. When density increased from 45 000 plants/hm2 to 90 000 plants/hm2, the relative green leaf area at maturity (RGLAm) decreased by 36.4% and 63.3%, respectively, while the mean rate of decrease in RGLA (Vm) increased by 40.2% and 34.6%, respectively. The sequence of date of onset of leaf senescence (Ts) was as follows: the lower layer>the upper layer>the middle layer. Compared with Shaandan 8806, the green leaf area was higher in the middle and upper layer of Shaandan 609, and maintained a higher green leaf area at the lower layer during the later growth stage under 90 000 plants/hm2. With the increasing of planting density, the nitrogen uptake during the pre-silking (Npre) and post-silking (Npost), and nitrogen harvest index (NHI) increased significantly. When the density increased to 90 000 plants/hm2, Npre, Npost and NHI of Shaandan 609 were 23.5%, 43.9% and 12.7% higher than Shaandan 8806, respectively. The biomass yield (BM), intercept photosynthetically active radiation (IPAR) and radiation use efficiency (RUE) increased significantly when improved plant density. When the density increased to 90 000 plants/hm2, the BM, IPAR, RUE and HI of Shaandan 609 were 26.1%, 10.2%, 9.1% and 14.8% higher than Shaandan 8806.【Conclusion】Compared with Shaandan 8806, the compact maize Shaandan 609 could improve the spatial distribution of light and nitrogen at the middle and upper layer under high density, increased the light intercept at the middle and lower canopy, delayed leaf senescence at the mid and lower canopy, and promoted the dry matter accumulation after silking, so a higher grain yield and RUE were obtained.
【Objective】In view of the prominent contradiction of straw utility, the optimization of straw returning method is significant for promoting the green and sustainable development of agriculture in northeast China, where is the main production areas of spring maize. In this study, the effects of tillage and straw incorporation approaches on the morphology and distribution characteristics of root, dry matter accumulation and yield of spring maize were investigated to provide a theory basis for optimizing tillage and straw incorporation measures to maintain agricultural production.【Method】The field experiment was carried out in Shenyang, Liaoning province in 2017 and 2018. The two-factor random zone group design was adopted to set up four treatments, including straw incorporation with full-thickness plough tillage (PTS), straw incorporation with strip plough tillage (PSS), straw incorporation with full-thickness rotary tillage (RTS), and straw incorporation with strip rotary tillage (RSS). Under different tillage and straw incorporation methods, the differences of root length, root dry weight, their spatial distribution in soil, dry matter accumulation dynamics and yield characters of spring maize were analyzed.【Result】Tillage and straw incorporation methods had significant effects on root length and distribution as well as dry weight and specific root length of spring maize at silking stage. In the vertical soil layer of 0-30 cm, the root length of PTS treatment was 7.9%-43.2% and 17.3%-41.5% higher than other treatments, respectively. In the vertical soil layer of 30-60 cm, root length under strip straw incorporation (PSS and RSS) treatments was average 20.1% and 20.3% higher than those under full-thickness straw incorporation (PTS and RTS) treatments, respectively. Centering on maize plant, the horizontal distribution of root length in soil showed that PTS treatment was the highest and RTS treatment was the lowest in 0-10 cm away from the plant. The lowest root dry weight was observed from RTS treatment, PTS, PSS and RSS treatments presented 36.5%, 59.6% and 17.3% higher root dry weight in the 0-10 cm soil layer, respectively. PTS treatment obtained the highest specific root length in 0-20 cm soil layers, with 8.7%-73.8% and 14.3%-44.7% more than those under other treatments. The spatial distribution of root surface area was significantly different among treatments. PTS and RSS treatments had higher root surface area in 0-30 cm soil layer and better root surface distribution in horizontal and vertical directions. The effects of tillage and straw incorporation methods on the accumulation of dry matter in shoot of spring maize at jointing, silking and maturity stages were significant. Compared with other three treatments, RTS reduced the average dry matter weight of stem+sheath and total shoot weight by 15.5% to 19.2% at jointing stage. The weight of ear and shoot dry matter in maturity stage under PTS treatment was 3.6%-12.3% and 2.7%-12.4% higher than those under other treatments, followed by PSS and RSS treatments, and RTS treatment was the lowest. Tillage and straw incorporation methods significantly affected the number of ears and grain yield of spring maize. PTS, PSS, and RSS treatments obtained average 8.3%, 7.9%, and 5.8% higher grain yield than that under RTS treatments in 2017 and 2018. RTS significantly reduced the number of ears by 2.9%-9.1% and 7.0%-9.7%, compared with other three treatments.【Conclusion】Proper tillage and straw returning methods were conducive to promoting the morphological development of crop root and its spatial distribution in the tilled soil layer, optimizing of dry matter accumulation and distribution characteristics, and the distribution of dry matter to ear at maturity, so as to increase the yield of spring maize. In summary, the straw strip returning with plough tillage was recommended in the study area.
【Objective】 This experiment was conducted to study the effects of chemical regulation and nitrogen fertilizer on photosynthesis, grain filling characteristics and radiation, heat and water utilization efficiency of maize under high planting density, so as to provide a theoretical basis for stress resistance, high yield and high efficiency of maize under high planting density. 【Method】 The experiment was performed with three nitrogen rates, N100 (100 kg·hm-2), N200 (200 kg·hm-2) and N300 (300 kg·hm-2) under high planting density (90 000 plants/hm2) during the maize growth season from 2017 to 2018. Chemical control (Yuhuangjin, 30% amine fresh ester·ethyl hydroxide) was sprayed at the seventh leaf stage. The effects of chemical control and nitrogen application on maize growth and development and radiation (RUE), heat utilization efficiency (HUE) and water utilization efficiency (WUE) under high density were studied. 【Result】 With the nitrogen application increasing, the 8 indexes, including net photosynthetic rate (Pn), max photochemical efficiency (Fv/Fm) of maize leaves, the content of grain endogenous hormones, grain filling rate, radiation utilization efficiency, heat utilization efficiency, water utilization efficiency and yield, first increased and then decreased, and all reached the maximum at 200 kg·hm-2 nitrogen rate. Compared with the single application of nitrogen fertilizer, the combination of chemical control and nitrogen fertilizer significantly increased Pn and Fv/Fm in leaves, endogenous hormone content in grains, grain filling rate, RUE, HUE, and WUE, which further increased grain yield. The correlation analysis showed that the grain filling rate was positively correlated with indole-3-acetic acid (IAA), cytokinin (CTK), gibberellin (GA) and abscisic acid (ABA), while the yield was positively correlated with RUE, HUE and WUE.【Conclusion】 Under high planting density, 200 kg·hm-2 nitrogen application and chemical control significantly improved the photosynthetic characteristics, promoted the grain filling process, improved radiation, heat and water utilization efficiency, and significantly increased the yield.
