【Objective】This study aimed to investigate the effects of long-term different straw return methods on productivity and apparent balance of nitrogen, phosphorus and potassium nutrients in rice-rapeseed rotation system, in order to provide the theoretical basis for the efficient utilization of straw resources in the rotation system.【Method】The field experiment was located in Wuxue City, Hubei Province, and started in 2014, with three treatments of straw not return (NPK), direct straw return (NPK+St) and burning straw return (NPK+Sb), to determine and analyze the yields, nitrogen/phosphorus/potassium nutrient uptake and their apparent balances and other related indicators of rice and rapeseed in the consecutive 10-year period from 2014 to 2024.【Result】The average results of the 10-year experiment showed that compared with the NPK treatment, the rice and rapeseed yield in the NPK+St treatment increased significantly by 7.7% and 10.7%, respectively; the rapeseed yield in the NPK+Sb treatment increased significantly by 5.2%, and the effect of yield increase on rice was not significant. The yield increase effects of NPK+Sb and NPK+St increased with the increase in years of straw return, and in the 6th year reached the significant level. Based on the annual nutrient uptake characteristics, compared with the NPK treatment, the annual nitrogen uptake in the NPK+St and NPK+Sb treatments increased by an average of 11.6% and 2.9%, respectively, the annual phosphorus uptake increased by an average of 11.9% and 10.2%, respectively, and the annual potassium accumulation increased by an average of 55.8% and 39.1%, respectively. Direct straw return significantly enhanced the absorption of nitrogen, phosphorus and potassium nutrients in the rotation system. Burning straw return effectively increased the absorption of phosphorus and potassium nutrients in the rotation system. The annual nitrogen, phosphorus and potassium surplus of rice-rapeseed rotation in the NPK treatment were 101.3 kg N·hm-2·a-1, -8.9 kg P2O5·hm-2·a-1 and -296.6 kg K2O·hm-2·a-1, respectively. The annual nitrogen surplus in the NPK+St treatment averaged 166.1 kg N·hm-2·a-1, with an increase of 64.0%. The annual phosphorus and potassium nutrient surpluses were realized for both NPK+St and NPK+Sb treatments, with surpluses of 33.0 and 19.0 kg P2O5·hm-2·a-1, 79.4 and 21.3 kg K2O·hm-2·a-1, respectively. 【Conclusion】Direct and burning straw return significantly increased the crops production potential and nutrient uptake by promoting nutrient cycling in the rice-rapeseed rotation system. The effect of stabilizing rice yield and increasing rapeseed yield was shown among the different crops in the rotation. The straw direct return was more favorable to increase crop yield and to maintain the nutrient balance of the farmland than the straw burning return. Therefore, it was recommended to promote the direct straw return approach in the process of farmland production in order to fully utilize its advantages of yield enhancement, stabilization, and nutrient balancing, and to promote the sustainable development of the rice-oil rotation system.
【Objective】Rice-rapeseed rotation is a major cropping system in the Yangtze River basin of China. Straw utilization is a crucial issue concerning agricultural sustainable development and environmental protection. This study aimed to explore the fertilizer-based utilization methods of straw in rice-rapeseed rotation systems, so as to provide the theoretical support for enhancing productivity and achieving efficient resource utilization in such systems.【Method】This study utilized a six-year (2017-2023) field experiment under rice-rapeseed rotation. Four treatments were chosen: no straw incorporation (NPK), direct incorporation of straw in both seasons (NPK+S/S), straw biochar incorporation in both seasons (NPK+B/B), and straw biochar incorporation in the rice season combined with direct straw incorporation in the rapeseed season (NPK+B/S). Crop yield and its stability, plant N absorption and utilization efficiency as well as the apparent N balance in soil were systematically analyzed.【Result】Direct and straw biochar incorporation significantly increased crop yields and yield stability. Compared with NPK, the rapeseed yields under NPK+S/S, NPK+B/B, and NPK+B/S increased by 13.9%, 14.8%, and 17.3% on average, respectively; rice yields increased by 8.5%, 7.2%, and 3.7%, respectively; annual energy yields improved by 10.5%, 9.9%, and 8.5%, respectively. Compared with NPK, the rapeseed yield sustainability index under NPK+S/S, NPK+B/B, and NPK+B/S was enhanced by 8.1% to 10.2%. Compared with NPK+S/S, NPK+B/B and NPK+B/S were more beneficial for enhancing rice yield stability (24.2% and 1.4%, respectively) and sustainability index (5.3% and 2.3%, respectively). Both straw management practices increased crop N uptake but decreased the N harvest index. Compared with NPK, aboveground N uptake in rapeseed increased by 7.4% to 20.7%, in rice by 3.3% to 15.0%, and in the annual rotation by 6.5% to 17.6% under NPK+S/S, NPK+B/B, and NPK+B/S treatments. However, the N harvest index in rapeseed and rice decreased by 0.2%-3.0% and 1.9%-3.8%, respectively. Compared with NPK+S/S treatment, NPK+B/B treatment significantly reduced N uptake in the above-ground part of rapeseed by 11.0%. The reduction in N uptake in rapeseed grains, rice grains, and the above-ground part of rice was not significant, while the N harvest index of rapeseed and rice was increased by 1.8% and 1.9%, respectively. Direct straw incorporation had an advantage in promoting crop N uptake, while straw biochar incorporation had an advantage in improving crop N distribution. Compared with NPK, NPK+S/S, NPK+B/B, and NPK+B/S significantly increased the partial factor productivity of applied N in rapeseed (13.9% to 17.2%) and rice (2.2% to 7.7%). All treatments showed N surplus, with the NPK+B/S treatment having the highest N surplus. Compared with the NPK treatment, the NPK+S/S, NPK+B/B and NPK+B/S treatments all increased the soil total N content (20.6%-22.7%). Soil total N content was the highest under straw biochar incorporation, which was more effective in converting surplus N into soil N and reducing N loss.【Conclusion】In rice-rapeseed rotation system, considering economic effects, compared with direct straw incorporation or straw biochar incorporation in both seasons, the strategy of applying straw biochar during the rice season and directly incorporating straw during the rapeseed season could not only ensure stable high crop yields but also enhance N fertilizer utilization and increase soil total N content, providing important support for the sustainable development of rice-rapeseed rotation systems.
【Objective】This study aimed to clarify the effects of long-term straw return on crop yield and soil fertility in rice-rice- rapeseed rotation, so as to provide a scientific basis for the efficient use of straw resources and fertilizer replacement and reduction technology in rice-rice-rapeseed rotation system.【Method】In this study, a positioning experiment on straw return in rice-rice- rapeseed triple cropping system were selected, which was carried out for 15 consecutive years from 2007 to 2022, and set up three treatments of conventional fertilizer application + straw not returned to the field (100%F), conventional fertilizer application + straw returned to the field (100%F+St), and fertilizer reduction of 20% + straw returned to the field (80%F+St). The effects of different fertilizer applications on crop yields, nitrogen, phosphorus and potassium nutrient accumulation and soil physico-chemical properties were investigated. Nutrient accumulation and soil physicochemical properties were analyzed to assess the annual nutrient apparent balance and soil comprehensive fertility index of rice-rice-rapeseed rotation. 【Result】The long-term straw return increased crop yield, yield stability and sustainability of the rice-rice-rapeseed rotation system, with the most significant increase in the rapeseed season. Compared with 2007-2010, the late rice and rapeseed average yields under the 100%F+St treatment in 2019-2022 increased by 28.9% and 58.7%, respectively. Compared with 100%F treatment, early rice, late rice, and rapeseed yields under 100%F+St treatment increased by an average of 7.2%, 6.9%, and 13.4%, respectively, and with an average increase in yield stability and sustainability under 100% F+St treatment of 23.6% and 12.5% in the 2019-2022 late rice season. After four consecutive years of straw return in combination with 20% fertilizer reduction, early rice, late rice, and rapeseed yields remained stable or higher than conventional fertilization. Compared with the 100%F treatment, the yields of early rice, late rice, and rapeseed under the 80%F+St treatmentincreased by 5.3%, 3.1%, and 0.8%, respectively, from 2019 to 2022. Long-term straw return (100%F+St) enhanced crop NPK nutrient accumulation and annual nutrient surpluses, and the 20% fertilizer reduction + straw return (80%F+St) treatment reduced the annual NPK surpluses of the rotation by 54.0 kg N·hm-2, 13.7 kg P2O5·hm-2, and 48.6 kg K2O·hm-2. Analysis of the integrated soil fertility index (IFI) of the rapeseed season and the rice season following the long-term straw return revealed that the IFI of 100%F+St treatment was 1.44 and 1.51 in rapeseed season and rice season, respectively, which was significantly increased by 6.4% and 4.3% compared with 100%F treatment, respectively. The increase in IFI was higher in the rapeseed season than in the rice season. Compared with 100%F treatment, 80%F+St treatment had no significant difference in rice season and rapeseed season, with soil IFI values of 1.29 and 1.45, respectively. The increase of IFI under 100%F+St treatment mainly depended on the increase of organic matter, total nitrogen, and available potassium content by 22.8%, 20.5%, and 13.7% in rapeseed season, and the increase of organic matter, total nitrogen, and available phosphorus content by 14.1%, 1.7%, and 4.3% in rice season, respectively.【Conclusion】In conclusion, long-term straw return to the field could improve crop yield, N, P2O5 and K2O nutrient accumulation and comprehensive soil fertility index of rice-rice-rapeseed rotation system, and with the increase of the time period of returning to the field, the stability and sustainability of crop yield increased. Based on the straw return condition with 20% fertilizer reduction, crop yield and nutrient accumulation could be effectively guaranteed to be maintained or higher than the conventional fertilization level, and the sustainability and stability of yield in rice season was higher than that in rapeseed season. Therefore, a 20% reduction of chemical fertilizer in the rice season could guarantee the stable yield and high efficiency of the rice-rice-rapeseed rotation system.
【Objective】To address the critical constraint of soil available magnesium (Mg) deficiency on annual productivity in the rice-rapeseed rotation systems of China’s Yangtze River Basin, this study systematically investigated the effects of Mg fertilizer application rates on annual crop yield formation, nutrient uptake, and Mg balance in the soil-crop system, for providing a theoretical basis for efficient Mg management in rotation systems.【Method】Based on a field experiment initiated in 2017 at Wuxue, Hubei Province, this study selected six rotation cycles (2017-2023) with five Mg fertilizer treatments (0, 15, 30, 45, and 60 kg MgO·hm-2 per season). The crop yield components, nutrient concentrations in different plant parts, and biomass in the rice-rapeseed rotation system were measured. Based on these measurements, crop nutrient accumulation, fertilizer use efficiency, and soil nutrient balance were calculated to clarify the magnesium requirement characteristics of crops in the rotation system and establish fertilization strategies for the rotation system.【Result】(1) Mg application significantly increased annual system productivity, with yield increments of 9.5%-23.8% for rapeseed and 2.2%-4.0% for rice. A linear-plateau model indicated the maximum yields of 2 388 kg·hm-2 (rapeseed) and 8306 kg·hm-2 (rice) at an annual MgO rate of 60.4 kg·hm-2 (38.1 kg·hm-2 for rapeseed season; 22.3 kg·hm-2 for rice season). Yield improvements in rapeseed were attributed to increased siliques per plant and seeds per pod, while rice yield gains resulted from higher effective panicles and filled grains per panicle. (2) Mg application significantly elevated Mg concentrations in all plant parts at maturity, with smaller effects on grains. The maximum increases were 45.1% (rapeseed stem), 66.2% (pod wall), and 8.5% (seed) for rapeseed, and 14.9% (stem and leaf) and 6.5% (seed) for rice. Annual biomass and Mg accumulation increased by up to 1 820 kg·hm-2 (8.5%) and 6.3 kg·hm-2 (29.5%), respectively. While rice showed higher absolute biomass and Mg accumulation, rapeseed 's proportional contribution to annual Mg uptake increased with Mg application. (3) Mg fertilizer apparent utilization rate and agronomic efficiency declined with increasing application rates, with rapeseed consistently exhibiting higher utilization than rice under equivalent Mg inputs. Mg removal by crops exceeded fertilizer input below 90 kg·hm-2 annual application, while 120 kg·hm-2 resulted in Mg surplus. If the straw was returned to the field, Mg surplus would occur when the annual Mg fertilizer application rate was 60 kg·hm-2.【Conclusion】The application of Mg fertilizer significantly enhanced annual crop productivity in the rice-rapeseed rotation system, with rapeseed exhibiting more pronounced demand and utilization advantages for Mg. It was recommended that the annual Mg fertilizer application rate in the rotation system be approximately 60 kg·hm-2, with a seasonal application ratio of about 2:1 between the rapeseed and rice seasons, to achieve efficient Mg fertilizer management and to improve annual productivity.
【Objective】The aim of this study was to investigate the effects of potassium (K) fertilizer application rates on crop productivity, K utilization, and apparent K balance under the rice-rapeseed rotation system in the Yangtze River Basin, so as to provide a scientific basis for the rational application and distribution of potassium fertilizer in the rice-rapeseed rotation system.【Method】A field experiment was carried out from 2016 in Wuxue City, Hubei Province, China. Five treatments were set up with 0 (K0), 60 (K60), 120 (K120), 180 (K180) and 240 (K240) kg K2O·hm-2, respectively. The crop yield, K uptake, K fertilizer utilization and apparent K balance were studied from 2016 to 2024.【Result】K fertilization significantly increased crop yield and aboveground K uptake, with the increase in rapeseed yield and aboveground K uptake being greater than that of rice. Compared with K0, K application significantly increased rice and rapeseed yield by 18.1%-32.7% and 46.7%-93.1%, respectively, and K uptake by 72.3%-240.1% and 124.6%-512.2%, respectively. K fertilization significantly reduced yield stability index of rapeseed yield by 24.2%-41.2%, and markedly increased yield sustainability index (SYI) by 23.2%-45.7%. The yield stability index of rice yield across all treatments was lower than that of rapeseed, and SYI was comparatively higher. The annual energy yield under the K0 treatment exhibited a progressive decline with each successive year of crop rotation. The increase in rapeseed yield was primarily attributed to an increase in pod number and seed number, whereas in rice, it was mainly due to an increase in effective panicles and filled grains per panicle. As the K fertilizer application rates increased, the proportion of K uptake in rapeseed within the annual system rose, with the average K uptake ratio between rice and rapeseed being 3:2. The agronomy efficiency and the recovery efficiency of K fertilizer in rice were on average 4.5 kg·kg-1 and 2.5 percentage points higher than those in rapeseed, respectively. Conversely, the K fertilizer dependency of rapeseed was 11.6 percentage points higher than that of rice. K application shifted the annual K apparent balance from deficit to surplus. When the K fertilizer application rate increased to 180 kg K2O·hm-2 during the rice season, the K balance transitioned from deficit to surplus, while in the rapeseed season, 60 kg K2O·hm-2 was required to achieve surplus. Fitting with a linear-plus-plateau model, the optimal K fertilizer application rates were determined to be 102 kg K2O·hm-2 for the rice season and 147 kg K2O·hm-2 for the rapeseed season. 【Conclusion】In summary, the application of potassium fertilizer increased the yield of rapeseed better than that of rice. The recommended annual potassium fertilizer application rate for the rice-rapeseed rotation system was 250 kg K2O·hm-2, with the fertilization ratio between the rice season and the rapeseed season being approximately 2:3.
【Objective】The rice-rapeseed rotation is a typical paddy-upland rotation cropping pattern in the Yangtze River Basin of China. The seasonal wet-dry alternation in soil affects the transformation of soil nitrogen and the application effect of nitrogen fertilizers. From the perspective of annual rotation, this study explored the differences in the effects of nitrogen fertilizer management on crop yield and nitrogen distribution in the rice-rapeseed rotation system, so as to provide a scientific basis for the efficient utilization of annual nitrogen fertilizer in the rice-rapeseed rotation system.【Method】The field experiment was located in Wuhan, Hubei Province, and was founded in 2012. This study selected 11 consecutive rice-rapeseed rotation years from 2012 to 2023 to conduct the experiment, four nitrogen fertilizer treatments were designed in the experiment: (1) no nitrogen application in both the rapeseed and rice seasons (N0-0); (2) applying 150 kg N·hm-2 of nitrogen fertilizer in both the rice and rapeseed seasons (N150-150); (3) adding 75 kg N·hm-2 of nitrogen fertilizer to the rice season on the basis of treatment (2) (N225-150); (4) adding 75 kg N·hm-2 of nitrogen fertilizer to the rapeseed season on the basis of treatment (2) (N150-225). The related indicators such as crop yield, annual system energy yield, yield components, nitrogen accumulation and soil nitrogen supply capacity were analyzed.【Result】There were differences in the response of yield and nitrogen accumulation to nitrogen fertilizer management between rapeseed and rice. When the nitrogen application rate was N150-150 in both rice and rapeseed seasons, compared with no nitrogen application, the yields of rapeseed and rice increased by an average of 207.1% and 92.4%, respectively, and the nitrogen accumulation increased by an average of 253.2% and 114.7%, respectively. Compared with the N150-150 treatment, further application of nitrogen fertilizer during the rice season increased rice and rapeseed yields by 9.6% and 6.6%, respectively, while application of nitrogen fertilizer during the rapeseed season increased yields by 4.4% and 23.7%, respectively. Nitrogen application mainly increased crop yield by increasing the number of siliques per plant in rapeseed, the number of effective panicles per area in rice, and the number of grains per panicle, with rapeseed having a higher yield increase effect. In addition, from the analysis of the annual nitrogen fertilizer yield-increasing effect in the rotation system, compared with the application of 150 kg·hm-2 of nitrogen in both rice and rapeseed seasons, the system energy yield and nitrogen accumulation of the rotation system under N225-150 treatment increased by 8.4% and 13.5%, respectively, and those under N150-225 treatment increased by 10.6% and 18.4%, respectively; at the same time, the annual nitrogen fertilizer utilization rate in the rice season with additional nitrogen application was 2.7 percentage points lower than that in the rapeseed season with additional nitrogen application, which might be related to the fact that the soil basic nitrogen supply in the rice season was 91.1% higher than that in the rapeseed season, resulting in a lower demand for high nitrogen input.【Conclusion】Therefore, in actual production, the annual nitrogen allocation should be adjusted according to the crop nitrogen requirements and soil nitrogen supply characteristics of the rotation system. In the rapeseed season, the nitrogen fertilizer application could be appropriately increased to achieve high yield, while in the rice season, the soil nitrogen supply capacity should be fully utilized, and the nitrogen fertilizer application should be appropriately controlled to achieve stable and efficient production of the rice-rapeseed rotation system.
【Objective】By studying the effects of nitrogen fertilizer application rates on the annual crop yields, stability, and nitrogen uptake in the rice-rapeseed rotation system, this study explored the changing trends of the appropriate annual nitrogen fertilizer application rates for rice and rapeseed, so as to provide a theoretical basis for rational fertilization in the rice-rapeseed rotation in the middle reaches of the Yangtze River region.【Method】This locational trial was located in Wuxue City, Hubei Province, and was started in 2016. In this study, eight consecutive years of field locational trials were selected from 2016 to 2024. Five nitrogen fertilizer application rate gradients of 0, 90, 180, 270, and 360 kg N·hm-2 were set up for both crops in the two seasons. The yields and their stability, nitrogen accumulation amounts, nitrogen fertilizer use efficiency, apparent nitrogen surplus, and the annual trends of appropriate nitrogen fertilizer application rates in the rice-rapeseed rotation system were analyzed. 【Result】Nitrogen fertilization significantly enhanced crop productivity in rice-rapeseed rotation systems. Compared with the nitrogen-free treatment, in each nitrogen-applied treatment, the average annual yield of rice increased by 1 035-1 769 kg·hm-2, with an increase range of 19.4%-33.2%. The application of nitrogen fertilizer had a significant yield-increasing effect on winter rape; compared with the nitrogen-free treatment, the average annual winter rape yield increased by 1 041-2 208 kg·hm-2, and the yield increased by 1.3-2.8 times. Aboveground nitrogen accumulation in rice and rapeseed increased progressively with elevated N inputs, averaging 36.8-108.2 kg·hm-2 and 43.4-139.3 kg·hm-2 higher than that under the zero-N control, respectively. Continuous observations indicated rising trends in both N accumulation and N recovery efficiency (NRE) for both crops under continuous rotation. During the rice season, with the increase in nitrogen fertilizer application rate, compared with the previous year, the average annual increase in nitrogen accumulation increased from 2.6% to 9.8%. In the rapeseed season, the increase in nitrogen accumulation in the nitrogen-free treatment was not significant among years. After applying nitrogen fertilizer, the nitrogen accumulation increased by an average of 3.4%-5.1% annually compared with the previous year. NRE in rice remained stable during the first three years but exhibited a parabolic rise starting from the fourth year. For rapeseed, NRE under 90-270 kg N·hm-2 N rates increased by 5.6% annually, whereas no significant improvement occurred at 360 kg N·hm-2. Apparent N balance in the zero-N treatment consistently showed deficits, while N-surplus in fertilized plots declined annually by 3.6%-8.3% (rice) and 2.4%-6.7% (rapeseed). Systematic analysis revealed an annual increase of 2.3% in optimal N rates for rice (annual mean: 146.8 kg N·hm-2) and 0.9% for rapeseed (annual mean: 198.0 kg N·hm-2).【Conclusion】In the continuous rice-rapeseed rotation planting mode, it was necessary to apply fertilizers with appropriate nitrogen application rates according to the nitrogen absorption characteristics of the crops in the rotation system, and to dynamically adjust the annual nitrogen allocation amount according to the soil nitrogen status.
【Objective】To explore the potential of optimizing fertilization under rice-rapeseed rotation for increasing crop yield and efficiency in medium and low yield fields, this study analyzed the effects of optimized fertilization on yield, nutrient absorption, and soil fertility in rice-rapeseed rotation, as well as the effectiveness of rice-rapeseed rotation in improving soil fertility. This study aimed to identify fertilization strategies suitable for medium and low yield fields and the potential for improving quality and efficiency in rice-rapeseed rotation, so as to provide the theoretical guidance for reducing obstacles in medium and low yield fields, promoting efficient production in rice-rapeseed rotation, and achieving sustainable development of rice-rapeseed rotation.【Method】The experiment was conducted at the Agricultural Science Research Institute in Rugao City, Jiangsu Province from 2017 to 2024, with low yield fields as the research objects. Through small-scale experiments, no fertilization treatment (CK), no nitrogen treatment (PK), no phosphorus treatment (NK), farmer's habitual fertilization treatment (FFP), and optimized fertilization treatment (OPT) were set up. By analyzing the annual yield of crops in both water and drought seasons, the nutrient absorption of aboveground parts during maturity, and soil nutrient content, the yield change rules under different fertilization systems of rice-rapeseed rotation were clarified, and the main influencing factors were explored.【Result】During the seven year rotation period, compared with FFP, the yield and yield composition of rice and rapeseed treated with OPT were more stable with increasing rotation cycles. Compared with FFP, OPT treatment significantly increased the nitrogen and phosphorus partial productivity of rice and rapeseed, with rice showing 51.5%-73.3% and 81.8%-107.9% higher nitrogen and phosphorus partial productivity, respectively; rapeseed was 137.2%-152.3% and 89.8%-101.9% higher, respectively. During the four-year rotation period, the aboveground biomass of rice and rapeseed treated with OPT was higher than that treated with FFP. Comparing the two annual rotation periods at the beginning and end of the comparative experiment, it was found that the accumulation of nitrogen, phosphorus, and potassium in the aboveground parts of rice and rapeseed treated with OPT was higher than that under FFP treatment, and OPT treatment had a better effect on improving soil organic matter, total nitrogen, and available potassium than FFP treatment. After 7 years of rice-rapeseed rotation, the soil fertility index significantly increased (63.8%-117.2%) under all treatments. Compared with FFP treatment, the average membership degree of five soil chemical indicators in the rice season treated with OPT was higher than that under FFP treatment, and its comprehensive fertility index increased by 13.4%-19.2%. In addition, the soil phosphorus activation coefficient during the three-year rotation period was monitored, and it was found that the OPT treatment had a higher soil phosphorus activation coefficient than under FFP treatment. 【Conclusion】Compared with the traditional fertilization practices of farmers, optimizing fertilization could be achieved by optimizing fertilizer management. Based on reducing nitrogen and phosphorus fertilizer application by 40% and 50% in rice and 60% and 50% in rapeseed, stabilizing their yield composition, maintaining high biomass and nutrient absorption, and achieving stable annual yield in the rice-rapeseed intercropping system; the performance of optimized fertilization treatment in improving fertilizer utilization efficiency and soil fertility was better than that of farmers' habitual treatment. Therefore, optimizing fertilization under long-term fertilizer reduction could coordinate crop nutrient needs and nutrient supply, maintain stable or increased crop yields, and improve fertilizer utilization efficiency. Rice-rapeseed rotation could improve soil fertility in medium and low yield fields, achieve obstacle reduction in medium and low yield fields, and promote sustainable development of rice-rapeseed rotation.
【Objective】Rice-rapeseed rotation is an important paddy-upland crop rotation in China, and the application of nitrogen (N), phosphorus (P) and potassium (K) fertilizer plays an important role in guaranteeing high and stable crop yields. This study systematically assessed the effects of different types of nutrient inputs on the yield and nutrient utilization of the annual crop of a continuous term rotation, so as to provide a reference to the management of nutrients in rice-rapeseed rotation.【Method】A rice-rapeseed rotation field trial was carried out for 8 continuous years from 2016 to 2024, with 4 treatments of equal application of N, P and K (NPK), and no N (-N), no P (-P), and no K (-K), to analyze the yield of annual crops, yield components, nutrient utilization, and apparent balance.【Result】Imbalanced fertilization significantly reduced crop yields, compared with the NPK treatment, the -N, -P and -K treatments reduced yields by 26.7%, 36.7% and 2.8% in rice and 57.4%, 86.4% and 12.3% in rapeseed, respectively, and the reduction in the number of effective number of panicles in rice and the number of pods in rapeseed were the main reasons for the crop yields reduction. With the increase of rotation year, the cumulative crop yield under -N, -P and -K treatments gradually increased the degree of yield reduction; compared with NPK treatment, the yield stability and sustainability of rice and rapeseed were significantly reduced under -P treatment. In terms of annual nutrient allocation in crop rotation, the N, P2O5 and K2O accumulation in rice was higher than that in rapeseed, and the trends of nutrient accumulation in rice, rapeseed and crop annual rotation under imbalanced fertilizer application conditions were consistent with yields. Fertilizer use efficiency analysis showed that the fertilizer contribution rates of N, P and K fertilizers were lower in rice than in rapeseed, while the agronomic efficiency of N and P fertilizers, and the recovery efficiency of P and K fertilizers were higher than those of rapeseed. From the nutrient apparent balance of the annual rotation, the nutrient surpluses of the soil in the rice season were all lower than those of the soil in the rapeseed season, and the annual rotation of the NPK treatment had surpluses of 135.1 kg N·hm-2, 49.6 kg P2O5·hm-2, and deficits of 225.1 kg K2O·hm-2, deficiency of a single nutrient exacerbated the surplus of other nutrients.【Conclusion】In the rice-rapeseed rotation system, the deficiency of any single essential nutrient notably diminished crop yield as well as the utilization of nutrients, and the rate of yield reduction was related to the basic soil fertility level. Under the conditions of this study, the -P treatment had the largest yield reduction, followed by the -N treatment, while the -K treatment showed the smallest reduction. The magnitude of yield reduction in rapeseed was significantly higher than that in rice. Therefore, it was necessary to pay attention to the input of N and P fertilizers to achieve high and stable crop yields, and appropriate supplementation of K fertilizer to alleviate the depletion of soil K reservoirs, in order to realize high yield, high efficiency and sustainable development of the long-term rice-rapeseed rotation system.
【Objective】The aim of this study is to elucidate the long-term effects of tillage practices and fertilization measures on annual crop yield and nutrient utilization in a rapeseed- rice rotation system in the Yangtze River Basin, for providing a scientific basis for sustainable nutrient management to achieve synergistic grain and oilseed production in the region.【Method】Based on a site-specific field experiment (2016-2023) with a rice-rapeseed rotation system, a split-plot design was adopted. The main treatments were different tillage methods: rotary tillage (RT, 12 cm depth) and deep tillage (DT, 20 cm depth). The sub-treatments included three fertilization regimes: no fertilization (CK), chemical fertilizer alone (F), and combined organic-inorganic fertilization (FM, where chemical fertilizer in the rice season matched the F treatment, while the rapeseed season received organic-chemical fertilization). This study analyzed the rapeseed and rice yields, nutrient uptake, and nutrient use efficiency, with a comprehensive evaluation incorporating yield stability index (YSI) and sustainability index (SYI).【Result】Compared with CK, fertilization application significantly increased rice and rapeseed yields by 47.6% and 288.1%, respectively, while improving yield stability (YSI increased by 6.1% and 10.6%) and sustainability (SYI increased by 14.7% and 16.7%). Fertilization was the primary factor influencing crop yield, with FM outperforming F. DT further enhanced rice (9.2%) and rapeseed (7.0%) yields compared with RT, while significantly improving rice and rapeseed yield stability (YSI decreased by 17.9% and 4.7%, respectively) and sustainability (SYI increased by 5.7% and 7.7%, respectively). Among all treatments, FM-DT achieved the highest yields, stability, and sustainability for both crops. Further analysis revealed that FM-DT most effectively promoted nutrient translocation to grains, increasing N and phosphorus (P) harvest indices. The N and P harvest indices reached 76.9% and 76.0% in rice and 68.5% and 69.5% in rapeseed, respectively. Organic fertilizer substitution reduced chemical fertilizer input but enhanced N and P use efficiency, increasing them by 23.1% and 24.5% in rice and 63.7% and 22.8% in rapeseed, respectively. DT combined with organic substitution further improved N and P apparent recovery efficiency. 【Conclusion】The integration of FM with DT significantly enhanced productivity, stability, and sustainability in the rice-rapeseed rotation system while improving nutrient use efficiency. This approach represented an effective nutrient management strategy for achieving sustainable development in rice-rapeseed rotation in the Yangtze River Basin.
【Objective】The application of chemical fertilizers and organic materials is a crucial measure for increasing agricultural production. Rice-rapeseed rotation system is a primary paddy-upland crop rotation pattern in the Yangtze River basin of China. Clarifying the impact of chemical fertilizers and organic material inputs on the annual crop yield and nutrient utilization in rice-rapeseed rotation could provide a scientific basis for ensuring food and oil security and achieving green and sustainable agricultural development. 【Method】From 2017 to 2022, a continuous field experiment was conducted at the Huazhong Agricultural University's Shayang Experimental Station in Shayang County, Hubei Province. Four treatments were established: no fertilizer (CK), chemical fertilizer only (NPK), chemical fertilizer with straw return (NPK+S), and chemical fertilizer with straw return plus organic fertilizer (NPK+S+M). The crop yields, nitrogen (N), phosphorus (P) and potassium (K) nutrient absorption of rapeseed and rice were analyzed. The nutrient use efficiency, apparent nutrient balances, and their relationships with yield were also assessed.【Result】The average results over 6 years showed that compared with no fertilization, the application of chemical fertilizers and organic materials significantly increased the yield of rapeseed (493.5%-758.8%) and rice (94.3%-106.4%), and enhanced crop yield stability (24.6%-72.1%) and sustainability (17.2%-85.0%). Compared with the NPK treatment, the NPK+S treatment increased the yield of rapeseed by 6.3%, but decreased yield stability and sustainability; it decreased the yield of rice by 0.8%, but increased yield stability and sustainability. The NPK+S+M treatment increased the yield of rapeseed and rice by 44.7% and 5.4%, respectively, and improved the sustainability of yield. Throughout the rotation cycle, nutrient uptake by rapeseed was consistently lower than that by rice across all treatments. The addition of organic materials significantly enhanced nutrient uptake in both rapeseed and rice. Relative to the NPK treatment, the NPK+S+M treatment resulted in increases of 5.1%-91.2% in average nutrient uptake and 12.2%-100.4% in trend nutrient uptake. The NPK+S treatment did not significantly differ from the NPK treatment in average nutrient uptake but exhibited a 7.7%-25.4% higher trend nutrient uptake. The input of organic materials decreased the physiological nutrient use efficiency of rapeseed and rice. Compared with the NPK treatment, the physiological N use efficiency of rapeseed and rice in the NPK+S+M treatment decreased by 3.0 and 3.7 percentage points, respectively, and the physiological P use efficiency decreased by 19.3 and 25.5 percentage points, respectively. Further analysis revealed that the application of organic materials led to higher apparent nutrient surpluses, which caused the annual increase in the cumulative yield of crops in the rice-rapeseed rotation. The cumulative apparent nutrient surplus was significantly positively correlated with the cumulative crop yield. 【Conclusion】The application of chemical fertilizers and organic materials significantly increased crop yields and nutrient use efficiency, and its effects were jointly influenced by crop and nutrient type. Increasing organic fertilization along with chemical fertilizers and straw application could further enhance soil fertility and increase crop yield; however, efforts should focus on improving the physiological nutrient use efficiency to fully realize the potential of organic amendments for sustainable grain and oil production.
