Biochar amendment facilitates carbon (C)-neutral crop production in acidic and neutral soils, yet whether such synergistic benefits can be achieved in calcareous soils remains largely unknown. Here, we evaluated a 12-year field experiment involving continuous straw-derived biochar application (2250 and 4500 kg ha−1), sole mineral fertilization and an unfertilized control under maize-sorghum rotation in a Calcaric Cambisol on the Loess Plateau. We examined soil organic C (SOC) stock, microbial respiration and extracellular enzyme activities at various depths down to 60 cm and in different aggregate fractions from the 0–20 cm soil layer. Relative to the initial soil, the SOC stock decreased by 3% under the unfertilized control but increased by 3%, 11% and 22% under the sole mineral fertilizer, half-rate biochar and full-rate biochar treatments, respectively. The threshold annual C input for balancing cultivation-induced SOC loss was 2374 kg C ha−1. Biochar increased char-derived SOC proportion but reduced fungal necromass accumulation, which modulated macroaggregate stabilization. Furthermore, biochar amendment generally reduced soil respiration rate, confirming the occurrence of negative priming effects. Long-term biochar application suppressed phenol oxidase and N-acetyl-glucosaminidase activities, and their consistent positive correlations with soil respiration across soil profiles and aggregates highlighted their central roles in governing SOC decomposition, supporting the ‘enzyme latch’ and stoichiometric decomposition theories. Notably, biochar application, either alone or combined with mineral fertilization, did not improve maize and sorghum yields. Collectively, long-term biochar amendment inhibited microbial anabolism and induced an enzymatic cascading effect that constrained microbial catabolism, which slowed SOC decomposition and enhanced SOC sequestration while failing to stimulate nutrient cycling and crop production in the calcareous cropland soils of the Loess Plateau.

Biochar has gained significant attention for its potential in carbon sequestration, soil health improvement, and crop production sustainability. However, the existing studies predominantly focus on short-term experiments conducted in acidic or neutral soils. This study investigates the long-term effects of biochar application in a calcaric cambisol in a field experiment with four treatments: CK (no fertilizer or biochar), B (only biochar), NPK (chemical fertilizer), and NPKB (combination of chemical fertilizer and biochar). This study assessed soil organic carbon (SOC), sorghum yield, soil bacteria, plant nutrient accumulation in 2020 and 2022, and soil chemical properties after 12 years of consecutive application in 2022. The results revealed a significant increase in SOC due to biochar application in both 2020 and 2022 compared to the treatments without biochar. The 12-year biochar application also significantly enhanced soil total nitrogen (N), available phosphorus (P), and available potassium (K), irrespective of chemical fertilizer application. Notably, sorghum plant N and P accumulation remained unaffected by biochar, and plant N accumulation induced by NPKB was even lower than that of the NPK treatment in 2022. Furthermore, soil bacterial diversity and composition, as well as sorghum yield, showed no significant alterations due to biochar application in both years, despite increased soil nutrient content. These findings affirmed the benefits of carbon accumulation through long-term biochar application in calcaric cambisols, but the positive effects on crop production were found to be negligible.

Fertilization, a widely used agricultural management practice to maximum crop yields, significantly influences microbial community structure and diversity. Soil microbial communities are known to differ across plant growth stages, but how different organic and inorganic fertilization regimes shape microbial temporal variation remains unclear. To investigate the temporal stability of microbial communities under organic and chemical fertilization, rhizosphere soil of sorghum was collected at four growth stages (jointing, heading, filling and maturity) in a long-term field experiment with multiple chemical and organic fertilization treatments. The results showed that, compared with the control and chemical fertilizer treatments, organic manure treatments resulted in less pronounced variation in microbial community diversity and structure across growth stages. Microbial cooccurrence networks in organic manure treatments were more robust compared to the control and chemical fertilizer treatments, indicating greater stability of microbial community temporal variation in organically fertilized soils. Across different growth stages, fungal communities in manure treatments showed no significant differences in diversity or community structure, and maintained low average variation degree, whereas bacterial communities were more variable. These findings suggest that microbes in organically fertilized soils have more stable communities over time, with fungal communities being more stable than bacterial ones. This study provides insights into how fertilization shapes microbial communities and indicates that organic fertilization enhances the resistance of microbial communities under changing environmental conditions.

Organic fertilization and deep ploughing are expected to contribute to carbon (C) sequestration in arable soils. This hypothesis was evaluated over 11 years of chemical and organic fertilization under conventional tillage (20 cm) and deep ploughing (40 cm) in a rainfed sorghum-maize rotation system on the Loess Plateau. Soil was collected and analysed to determine the soil organic C (SOC) and total nitrogen (TN) contents in the soil profiles (0–60 cm) or in the macroaggregates, microaggregates and silt and clay fractions (0–20 cm only). The SOC and TN stocks at the 0–60 cm depth displayed a net decrease in the unfertilized control, a marginal increase with chemical fertilizer, a significant increase of 23–45 % and 19–42 %, respectively, with organic amendments and a significant increase of 54 % and 48 %, respectively, when combined with deep ploughing. A critical input amount of 2064 kg C ha−1 yr−1 or 162 kg N ha−1 yr−1 was found to be required to maintain the initial SOC or TN stock. The annual N input was positively correlated with the C sequestration efficiency (P < 0.001). This supports the microbial N mining theory. Organic fertilization increased soil aggregation and the specific activity of N-acetyl-glucosaminidase, which was positively correlated with the specific respiration rate in the whole soil profile (P < 0.001) and aggregates (P < 0.001). This appears to support the stoichiometric decomposition theory. However, deep ploughing decreased the specific activity of N-acetyl-glucosaminidase at the 40–60 cm depth compared with conventional tillage. Collectively, long-term organic fertilization combined with deep ploughing enhances SOC sequestration in three ways: directly through the input of exogenous C, indirectly by alleviating microbial N limitations and increasing the amount and stability of subsoil-associated C, and to a lesser extent by improving soil aggregation.

【Objective】 Surfactants are soil conditioners to improve soil water flow and reduce soil erosion. This paper investigates their impact on water-nitrogen transport in soil, as well as yield, quality and root growth of greenhouse lettuce. 【Method】 The experiment was conducted in laboratory using a calcareous cinnamon soil. The soil was amended by three surfactants: HydravanceTM200 (T1, moisturizing and synergistic surfactant mix), Methylglucosan polyether-20 (T2, moisturizing single surfactant), and IrrigAid (T3, moisture-regulating surfactant mix), separately. For each surfactant amendment, there were two nitrogen treatments: without fertilization (N0) and nitrogen fertilization (N1). Soil without amendment by any surfactant was taken as the control (CK). During the experiment, we measured the changes in soil water content and soluble nitrogen content, as well as the growth and yield of the lettuce. 【Result】 ① Compared to CK, T1, T2 and T3 enhanced the lateral movement of water in the soil, thereby leading to an even soil water distribution and a reduction in nitrate nitrogen content in the subsoil layer (20-30 cm). ② According to the pot experiment, the above-ground fresh mass and VC content of lettuce in the T1N1 treatment increased by 26.61% and 175.61%, respectively, in addition to the 2.10 times increase in nitrogen utilization efficiency (P˂0.05). Compared to CKN1, T2N1 significantly increased VC content by 104.88%, while T3N1 significantly increased total root length and volume by 61.98% and 112.90% (P<0.05), respectively. In comparison with CKN0 treatment, the aboveground fresh mass, VC amount and nitrate amount of lettuce in T1N0 treatment were significantly reduced by 19.57%, 43.84% and 81.75%, respectively; T2N0 reduced VC content and nitrate content by 24.66% and 86.52% (P˂0.05) respectively, and T3N0 reduced nitrate content by 68.50% (P˂0.05) and increased total root length and volume by 51.64% and 87.18% (P˂0.05) respectively. 【Conclusion】 All three surfactants increased lateral movement of water in the soil, thereby improved water and nitrogen distribution and their adsorption by lettuce roots. However, their efficiency in improving growth, yield, quality and nitrogen utilization of the lettuce depends on nitrogen fertilization.

Context: Crop plants are intimately associated with an enormous diversity of microbiota that profoundly influence their productivity, but the contribution of plant-microbiome interactions to grain yield and quality of sorghum during different developmental stages remains unclear.Objectives: The aim of this study was to evaluate the relative importance of sorghum-associated bacterial and fungal communities in different compartments in predicting sorghum grain yield and quality.Methods: We collected soil and sorghum plant samples from various compartments during the vegetative (jointing and heading stages) and reproductive (filling and maturity stages) periods of a long-term field experiment with multiple fertilization regimes. The sorghum-microbiomes in different compartments, including phyllosphere, leaf endosphere, stem endosphere, root endosphere and rhizosphere, were characterized using bacterial 16 S rRNA gene and fungal ITS region sequencing.Results: Microbial diversity at the filling and maturity stages was higher than that at the heading and jointing stages. Microbial community composition during the reproductive period was distinct from that during the vegetative period, and the microbial co-occurrence network was more stable and complex during the reproductive period. Random forest analysis revealed that the microbiome during the reproductive period had a greater impact on grain yield and protein content than during the vegetative period. In predicting sorghum grain yield and protein content, the microbiomes in the root endosphere and rhizosphere were more important than other compartments. Both bacterial and fungal community in these compartments played an equal role.Conclusions: These findings highlight the importance of bacterial and fungal communities during the reproductive period for grain yield and quality formation in sorghum, with profound implications for developing new microbiome-based strategies to promote plant performance and sustainable agriculture.

Foxtail millet [Setaria italica (L.) P. Beauv.], as a rich source of folates, has been cultivated on arid infertile lands, for which N deficiency is one of the major issues. Growing environments might have a significant influence on cereal folate levels. However, little is known whether N deficiency modulates cereal folate levels. In order to obtain enriched folate foxtail millet production in nutrient-poor soil, we conducted a study investigating the content of folate derivatives of 29 diverse foxtail millet cultivars under two N regimes (0 and 150 kg N ha(-1)) for 2 years to explore folate potential grown under low N. The contents of total folate and most derivatives were reduced by N deficiency. The effect on total folate content caused by N was stronger than cultivar genotype did. Folate content of enriched folate cultivars was prone to be reduced by N deficiency. Structural equation models (SEMs) revealed that N fertilization had a positive indirect effect on grain folate content through influencing plant N and K accumulation. Collectively, the results indicate much more attention should be paid to N management when foxtail millet is cultivated in infertile soil, to improve foxtail millet folate contents.

To investigate the effect of N application level on grain-filling and starch accumulation in individual sorghum grains,sorghum variety Fenjiuliang 1 was used as the experimental material in 2019 and 2020. Six N rates of 0, 75, 150, 225, 300, and 450 kg N hm –2 were applied before sowing to experimental plots in Shanxi, China. To analyze sorghum grain-filling and starch accumulation by the Richards’ growth equation, the superior and inferior spikelets were sampled at seven days intervals at each sampling from anthesis to maturity. The rational N application level(75 kg N hm –2 )showed the maximum grain number per panicle resulting in the maximum yield per hectare. For both superior and inferior spikelets, N had similar effects on grain weight,grain morphology structure, the characteristics of grain-filling, and grain starch accumulation. The grain weight, grain volume,and grain-filling rate increased with the increase of N application rate, whereas the maximum grain weight and grain volume was obtained with the zero N treatment. The grain starch accumulation rate was highly correlated with the activity of ADP-glucose pyrophosphorylase（AGPase）and soluble starch synthase（SSS）. Compared to the zero N treatment, N application enhanced grain starch accumulation rate at early grain-filling stage and grain-filling rate, which may be due to the increased AGPase and SSS activity at the early grain-filling stage. Compared with rational N(75 kg N hm –2 ), excessive N(450 kg N hm –2 )promoted grain starch accumulation by enhancing the activity of AGPase and SSS at the early grain filling stage, whereas zero N application enhanced sorghum grain weight and grain starch accumulation by extending the grain-filling duration and enhancing the activity of key enzymes in grain involved in sucrose-to-starch conversion at the late grain-filling stage.

【Objective】This study was conducted to clarify effects of different row spacings and planting densities on the development, yield, grain quality and NPK (nitrogen, phosphorus and potassium) accumulation of grain-feeding sorghum, and to identify the optimal cultivation mode in agro-pastoral ecozone of Shanxi, so as to provide the theoretical basis for the grain-feeding sorghum cultivation.【Method】A new grain-feeding sorghum variety Liaoxialiang No. 1 was selected for this study. Field experiments were conducted during 2018 and 2019. Three row spacings were set, i.e. 30, 50, and 60 cm, respectively. And there were four planting densities (13.5×104, 16.5×104, 19.5×104 and 22.5×104 plants/hm2) at each row spacing. The plant height and biomass at heading stage, grain yield, NPK accumulation at harvest and grain quality in different row spacings and planting densities were analyzed.【Result】There were significantly effects of row spacing, planting density and their interaction on the grain-feeding sorghum growth, nutrient accumulation, grain yield and quality. As plant density increased, the plant height, biomass and NPK accumulation at heading stage were increased. However, the biomass produced after heading, biomass and NPK accumulation at harvest, along with yield, increased first and then decreased with the increase of density under row spacing with 50 and 60 cm; Actually, the grain yield of feeding sorghum was positively correlated with biomass and N accumulation at harvest and the biomass produced after heading. The average grain yield, N and P accumulation and biomass after heading in row spacing of 50 cm were higher than those of 60 and 30 cm. Among the 12 treatments, the treatment with row spacing of 50 cm, planting density of 16.5×104 plants/hm2 had improved biomass and N accumulation at harvest, which were increased by 3.6%-12.8% and 3.6%-18.6%, respectively, relative to the average value of the total 12 treatments. The grain yield with row spacing of 50 cm and planting density of 16.5×104 plants/hm2 was the highest among all treatments, and they were 10 814 kg·hm-2 in 2018 and 12 434 kg·hm-2 in 2019, respectively. Starch and protein content of grain decreased with planting density increasing, but the influence of row spacing variation on them were less. Grain tannin content was significantly increased with planting density adding, while the row spacing increase also promoted tannin content. The influence of row spacing and planting density on tannin content was obvious, compared with those on starch and protein. Those treatments with row spacing of 50 cm and density of 16.5×104 plants/hm2 had similar tannin content with the average value of different treatments.【Conclusion】Both N accumulation and biomass production after heading were important for high grain yield of feeding sorghum. The appropriate plant spacing under different row spacings could improve feeding sorghum grain yield, but affect grain quality, especially the tannin content. Row spacing of 50 cm and density of 16.5×104 plants/hm2 was recommended in agro-pastoral ecozone in Shanxi (with variety of Liaoxialiang No.1) in terms of grain yield and quality of feeding sorghum.

为探究稻-再-油/肥轮作和施氮对水稻产量及籽粒灌浆特性的影响,于2015-2017年在湖北省武穴市进行稻-再-油/肥轮作定位试验,设置4个处理.T1:稻-再-油轮作,三季均不施氮;T2:稻-再-油轮作,三季施氮量为165、120和180 kg·hm-2;T3:稻-再-肥轮作,三季施氮量与T2相同;T4:稻-再-闲轮作,前两季施氮量与T2相同.研究各处理水稻产量及产量构成因子的变化,并利用Richards方程拟合水稻强、弱势粒的灌浆过程.结果表明:①2015-2017年头季稻和再生稻产量均表现为T3＞T2＞T4＞T1.与T4相比,2016-2017年T2处理的头季稻和再生稻分别增产8.4％和14.4％、22.2％和17.7％,T3分别增产12.7％和17.9％、25.1％和24.4％;与T1相比,2015-2017年T2处理的头季稻和再生稻分别增产35.1％和22.0％、36.4％和30.3％、65.1％和65.6％.②在稻-再-油/肥轮作和施氮条件下,2017年头季稻和再生稻籽粒灌浆特性表现一致.与T4相比,T2、T3均能提高头季稻和再生稻强势粒起始势和弱势粒达到最大灌浆速率的干物质量;与T1相比,T2延长头季稻和再生稻强、弱势粒有效灌浆期,从而实现头季稻和再生稻籽粒粒重增加,产量提高.

在轻简化施肥背景下,为减少渍害损失,解决长江流域冬油菜产区生产面临的重要问题,开展氮肥施用对油菜渍害的缓解作用研究.设置三因素田间试验,分别为不同氮肥用量(0、60、120、180、240和300 kg N/hm2)、氮肥类型(油菜专用控释尿素和普通尿素)和水分处理(苗期渍水和正常排水),测定各处理产量和氮肥农学利用率,明确苗期渍水对不同氮素供应水平油菜的影响,并比较油菜专用控释尿素一次性施用和普通尿素分次施用下油菜对苗期渍水的响应.结果 表明,直播冬油菜产量随氮肥施用量增加而提高,至240 kg N/hm2时不再增加.油菜专用控释尿素一次性施用,在氮肥用量为60～180 kg N/hm2时产量高于普通尿素分次施用;在氮肥用量为240～300 kg N/hm2时,两种氮肥类型产量基本相当.氮肥施用通过增加收获密度、单株角果数和每角粒数提高产量.苗期渍水导致直播冬油菜产量损失1.1％～41.9％,随氮肥用量增加,渍水引起的产量损失率呈先增加后降低趋势.0～60 kg N/hm2处理时,渍水使收获密度显著降低(降幅达29.4％～45.0％),单株角果数增加;施氮量为120～180 kg N/hm2时,渍水导致收获密度和单株角果数分别降低19.5％～33.7％和1.4％～17.7％;施氮高于180 kg N/hm2时,收获密度和单株角果数降幅减小(降幅分别为5％～30.9％和3.6％～9.5％).普通尿素分次施用和油菜专用控释尿素一次性施用,分别在施氮量为120和180 kg N/hm2时产量损失率最高,分别达29.8％和41.9％.相同氮肥用量下油菜专用控释尿素一次性施用的产量损失率大于普通尿素分次施用.渍水显著降低氮肥农学利用率,降幅为8.4％～51.9％,施氮充足(240～300 kg N/hm2)时氮肥农学利用率降幅低于氮素用量较低处理(120～180 kg N/hm2),油菜专用控释尿素一次施用处理的农学利用率平均降幅(36.5％)高于普通尿素分次施用(17.3％).综上可知,苗期渍水时,油菜专用控释尿素一次施用,会加重油菜受渍影响;土壤氮素供应能力较低时,渍害逆境解除后,适量追施速效氮肥可有效缓解产量损失,实现油菜稳产.

[目的]明确华中区域直播冬油菜的氮素稀释曲线模型及其适用性,探讨以氮素营养指数评价油菜氮素营养状况的可行性.[方法]通过2015-2016和2016-2017两个年度设置的不同氮肥用量(2015-2016年度氮肥用量为0、60、120、180和240 kg N·hm2,2016-2017年度氮肥用量为0、60、120、180、240、300和360 kgN·hm-2)的田间试验,研究不同氮肥用量下从苗期到花期油菜各生育时期地上部生物量和植株氮素含量变化,建立直播冬油菜地上部临界氮素浓度稀释曲线模型.并利用该模型和植株氮素含量计算氮素营养指数,明确氮肥用量对油菜植株各个时期氮素营养指数的影响,探究油菜产量和氮素营养指数的关系,确定各时期适宜的氮素营养指数.[结果]氮肥施用显著增加油菜地上部生物量和氮素含量,不同氮肥处理间差异显著.直播冬油菜地上部临界氮素浓度和地上部生物量符合幂指数的关系(Ncnc=3.49Dg0.36).该模型可以将独立的两个试验的氮限制和非氮限制组数据区分开,模型拟合的氮素浓度和植株实际氮素浓度线性相关,RMSE和n-RMSE分别为0.37和13％,模型具有较好的稳定性.在试验氮肥用量范围内,各点不同时期氮素营养指数随氮肥用量的增加而增加,且氮素营养指数对氮肥用量的响应与产量相似.氮肥施用显著增加油菜产量,尽管不同试验点直播冬油菜产量对氮肥用量的响应存在差异,但各点相对产量和不同时期的氮素营养指数均呈一元二次曲线关系,各生育时期氮素营养指数可以准确地反映油莱氮素营养状况.直播冬油菜相对产量为1时,越冬期、薹期和花期的氮素营养指数分别为1.35、1.26和1.03.[结论]油菜氮素稀释曲线模型Ncnc=3.49DM-0.26和氮营养指数能够评价华中区域直播冬油菜氮素营养状况,用于植株氮素诊断.

The use of controlled release urea (CRU) was proposed as a promising approach to improve crop yield and nitrogen use efficiency (NUE) of crops in varying regions. However, such beneficial effects have not been well assessed in winter oilseed rape (Brassica napes L.), which usually has a period longer than 200 days. In this regional scale study covering 9 site-years, the effects of CRU for oilseed rape (CRUrape) application on seed yield, NUE, N physiological efficiency (NPE) and the recommended application rate were investigated, in comparison with conventional urea (CU). Oilseed rape plants were grown with either CRUrape or CU applications with five N rates (0, 60, 120, 180 and 240 kg N ha(-1)). The results showed that CRUrape N release coincided well with oilseed rape N demand. The CRUrape application generally increased seed yield relative to CU, and such effects were more pronounced at higher N rates (180 and 240 kg N ha(-1)) because of the sufficiency N supply over the whole growing season and thus higher pods per plant. While the low N rates (60 and 120 kg N ha(-1)) could not supply adequate N at early development stage. Obvious N source x N rate interaction was observed. Moreover, the N source x site-year interaction was significant. The yield increase by CRUrape over CU varied considerably among site-year, suggesting CRUrape effects may depend very much on the target environmental conditions. Further analysis revealed that precipitation before wintering and accumulative temperature over the over-wintering contributed to variations in such CRUrape effects. The oil yield was remarkably increased by 12.4% and 7.1% by CRUrape relative to CU at 180 and 240 kg N ha(-1), because of the benefits of seed yield and oil concentration. The NUE and NPE of CRUrape were higher than that of CU as the N rate increased to 180 kg N ha(-1). The recommended N application rate of CRUrape was different from that of the CU in 5 of 9 site-years. The mean optimal N rate for the region investigated was quite similar for CRUrape and CU (203 and 201 kg N ha(-1), respectively), but CRUrape application with optimal N rate could enhance the average grain yield by 7.2% and the related gross profit by 17.8%, respectively. In conclusion, the CRUrape application could be used as a feasible strategy to improve oilseed rape seed yield, oil yield and NUE in the investigated region.

Improved weed management strategies are imperative in oilseed rape production. Herbicide and nitrogen (N) fertilization could be integrated into weed management as these are known to affect weed emergence and growth. In this study, two-factor designed field experiments were conducted to investigate the direct and/or interactive effects of herbicide application and N fertilization on weed suppression, crop N uptake, apparent N use efficiency (ANUE) and yield in weed infested winter oilseed rape. Oilseed rape were grown under herbicide-treated or herbicide-free conditions subjected to five N rates. The results demonstrated that herbicide exerted persistent weed suppression, and thereby improved oilseed rape growth. Increasing N supply enhanced the competition ability of oilseed rape against weeds, due to much higher sensibility to N supply. The interaction effects between herbicide and N application resulted in much greater enhancements in N uptake by oilseed rape over weeds in response to increasing N supply, when herbicide was applied. In contrast, weed N uptake in herbicide-free plots could be comparable to or even higher than that of oilseed rape, leading to significantly lower oilseed rape ANUE than in herbicide-treated plots. Oilseed rape yield increased significantly with increasing N rates, and such responses were more pronounced with herbicide application. Therefore, target yields could be fulfilled with substantially reduced N input, if herbicide was applied. In conclusion, effective use of herbicide in combination with optimum N fertilization would be a strategy to achieve weed suppression, yield increase and meanwhile to improve ANUE and reduce N input in winter oilseed rape.

[目的]冬油菜产量常受限于季节性干旱、冬季低温以及土壤肥力较低等因素.考虑到秸秆还田有培肥土壤的优势以及长江中下游地区稻草过剩的现实,通过田间试验研究稻油轮作区稻草覆盖还田对直播冬油菜生长的影响,探讨稻草整株覆盖还田对直播油菜生育期内密度、株高、根茎粗的变化特征及其对油菜产量和养分吸收量的影响.[方法]试验于2014—2015和2015—2016年在湖北省武汉市华中农业大学试验场进行,共设置4个处理,分别为:1)对照,不施肥稻草不还田(CK);2)不施肥稻草覆盖还田(S);3)单施化肥(NPK);4)稻草覆盖还田配施化肥(NPK+S).施肥处理(NPK、NPK+S)肥料用量为N 180 kg/hm2、P2O560 kg/hm2、K2O 75 kg/hm2、硼砂15 kg/hm2.分别于油菜苗期、蕾薹期、花期、角果期和成熟期取样,测定油菜地上部生物量,氮磷钾含量和积累量,并在田间监测油菜生育期内密度、株高和根茎粗.[结果]稻草覆盖还田提高土壤最低温度0.6～1.2℃(播后95天),降低土壤最高温度0.8～1.8℃(播后184天),缩小土壤温度变幅2.3℃(播后95～184天),提高土壤平均含水量8.0％～8.9％(播后48～184天).与稻草不覆盖相比,稻草覆盖还田减少冬油菜80％ 以上的出苗密度;与出苗密度相比,成熟期CK、S、NPK和NPK+S处理的密度分别降低71.3％、40.3％、69.5％ 和32.1％,稻草还田处理的油菜生育期内密度降低幅度小于稻草不还田处理.油菜成熟期S处理的根茎粗和株高分别比CK显著提高了22.7％ 和8.3％,NPK+S和NPK处理株高和根茎粗无明显差异.两年结果表明,S处理的最大生物量较CK平均增加了88.6％,与NPK处理相比,NPK+S处理的地上部苗期生物量降低3.7％～27.9％,角果期生物量平均增加28.1％.CK和S处理氮、磷和钾素积累量均在蕾薹期—花期差异较大,成熟期S处理的氮、磷积累量分别较CK高28.6％～268.2％、93.3％～253.1％,两年增产率分别为218.8％ 和28.5％;施肥处理(NPK、NPK+S)冬油菜氮、磷和钾积累量随生育期持续增加,均在角果期达到最大值,与NPK相比,NPK+S处理分别提高成熟期油菜氮、磷和钾积累量18.1％～19.1％、23.7％～36.9％ 和28.3％～56.9％,两年分别增产1811和1032 kg/hm2,增产率分别达到25.6％ 和20.3％.[结论]稻草覆盖还田能缓解气温骤变对土壤温度的影响,保持土壤含水量,缓解土壤干旱.稻草覆盖还田前期抑制直播冬油菜的出苗密度,后期可维持冬油菜密度的稳定,同时对冬油菜的生长、生物量、产量和养分吸收量有促进作用.

To clarify the effects of different nitrogen (N) application on carbon (C) and N accumulation in oilseed rape and the distribution on the aboveground and underground, a hydroponic test was conducted. The seedling was grown in distilled water and cultured with full strength nutrient solution after transplanted. A total of 6 N levels were set for the test, and they were 0. 01, 0. 05, 0. 1, 0. 5, 1. 0 and 6. 0 mmol/L. Dynamics of dry matter, C and N aboveground and underground of oilseed rape within 35 days was investigated every 7 days. The results showed that with the increase of N application, the leaf area per plant, dry matter aboveground, N concentration and accumulation increased significantly. Dry matter, C and N accumulation underground increased as N application added and then decreased. The C concentration of both shoot and root were not affected. The substance accumulation underground of 0. 1, 0. 5, and 1. 0 mmol/L treatment reached the higher level among the treatments on the 7 th, 14 th, and 21 th days after transplanting, respectively. Substance accumulation underground increased as N application increased after 28 d after transplanting. The R/S of dry matter decreased remarkably as N application increased. C accumulation per unit area of leaf and N accumulation per gram root improved with increasing N concentration as the N supply was deficient. Insufficient N supply increased the distribution of C and N to the root and reduced the rate of C and N accumulation in the plants, exerting greater influence on the aboveground.

[Objective] This study investigated the effects of different dosage of special controlled release urea (CRU) on the yield and nitrogen (N) uptake of winter oilseed rape in different areas.Our aim was to evaluate the suitable rate of the special CRU for oilseed rape and provide the basis for guiding light simplification of oilseed rape production.[Method] Field experiments were conducted in Hengyang (Hunan Province),Jiujiang (Jiangxi Province),and Wuxue (Hubei Province) during the period of 2015-2016,investigating nutrient release and fertilization effects of the special CRU.Each site included 5 nitrogen application rates being 0,60,120,180 and 240 kg N·hm-2,respectively.[Result] Field bagging experiment showed that the release time of special CRU was about 150 days,with the accumulative release amount of 83.4％,which coincided with the N demand of oilseed rape.The application of special CRU could control the harvest density of winter rapeseed,increasing the number of pods per plant and seed number per pod.Compared with no N treatment,the number of pods per plant and seed number per pod increased 15.0-81.5 pods per plant and 0.2-2.4 seeds per pod,respectively.Harvest density changed the coordination group and individual with N fertilizer variation.Oilseed rape production performed the highest grain yield when applying 180 kg N·hm-2 among the sites,which increased by 1 118 and 1 088 and 2 049 kg·hm-2,compared with the without N treatment,respectively.By fitted with linear and platform model,optimal special CRU dosages were 174,180 and 192 kg N·hm-2 in Hengyang,Jiujiang and Wuxue,respectively.The biomass,N concentration and N accumulation of aboveground biomass were significantly increased with the application of the special CRU.With the increase of N application rate,the proportion of N in the stem was raised gradually,and the proportion and distribution of N in the seed decreased,while the ratio of N distribution in the shell kept about 10％.The nitrogen use efficiency (NUE) was different in different periods.The NUE was 50.69％-56.89％ at flowering stage,39.39％-46.71％ at maturing stage,and only 9.20％-23.45％ at seedling stage,respectively.At seedling and flowering stages,the NUE showed increase first and then decrease with N application rate increase,reaching the maximum when the amount of the special CRU dosage was 180 kg N·hm-2.However,at maturing stage,the NUE reduced with the increase amount of nitrogen application.[Conclusion] The special CRU for winter oilseed rape could improve N uptake and promote the growth and development of rape in each growth period,especially in regulating the harvesting density,increasing the pod number per plant and seed number per pod,and eventually enhancing the rapeseed yield.The recommended amount of special CRU was 180 kg N·hm-2 among the sites.

Through adopting plot design and randomized block arrangement, we studied the influences of different nitrogen fertilizer application rates on the seedling emergence rate, nitrogen accumulation, agronomic traits, rapeseed yield and economic benefit of directly-sown oilseed rape in north area of Jiangxi. The results showed that the application of nitrogen fertilizer signifi-cantly reduced the density of directly-sown oilseed rape in its growth process, but it improved the various agronomic traits of this crop to certain extent. The application of nitrogen fertilizer could significantly increase the rapeseed yield and economic benefit of directly-sown oilseed rape, and its economic benefit was the highest (3445 yuan/hm2) when the application rate of nitrogen fer-tilizer was 245.4 kg/hm2 .

Yield loss in oilseed rape is caused by a decline in plant population density (PPD) due to nitrogen (N) insufficiency. The optimization of PPD is the foundation of the high and stable yield of winter oilseed rape. Field experiments were conducted with five contrasting N applications (0, 60, 120, 180 and 240 kg N ha(-1), denoted by NO, N60, N120, N180 and N240, respectively) to identify the effect of different N application rates on PPD dynamics and the influence of PPD at harvest (PPDh) on seed yield. Oilseed rape yield was increased by the increase of PPDh and yield per plant as the N application rate added. The N deficiency decreased PPDh, resulting in a 35.1% and 17.1% yield loss in the NO and N60 treatments compared to the PPDh of the treatment with the highest yield. This loss accounted for 30.9% and 20.6% of the total yield loss in the both treatments, respectively. PPD declined after the seedling emergence over the whole growing season, and the N application rate exhibited different effects at different growth stages. Sufficient N supplying suffered a sharp decline in PPD mainly during the seedling stage, accounting for approximately 46.1% similar to 48.1% of the total mortality. As the N supply was insufficient, PPD declined dramatically both at the seedling stage and after the flowering stage, with the mortality proportion of 38.2% and 39.7% in the NO treatment, respectively, resulting in greater mortality than the other stage over the growth period. A significant difference in the degree of PPD decline between sufficient and insufficient N treatments was observed since 150 days after sowing (DAS) till the harvest stage. Reduction in PPD was regulated by plant N status, and there was a negative relationship between N concentration and PPD. The minimum N concentrations of minimum decline in PPD from seedling emergency to 60 DAS and from 150 DAS to harvest were 4.11% and 2.44%, respectively. A lack of N increased plant mortality led to the reduced PPDh and decreased yield. PPDh should be optimized by the reasonable N management to promote individual growth, guarantee the group development, and achieve economic and efficient production.

[Objectives] Weed is one of the main factors affecting yield of rapeseed.Controlling its growth cost effectively plays key role for improving the production efficiency of direct seeding rapeseed.[Methods] A field trial was carried out in Wuhan during October 2014-April 2015.Three seeding amounts of rapeseed (1.5,4.5 and 7.5 kg/hm2) and five nitrogen application rates (0,60,120,180 and 240 kg/hm2) were designed in the experiment.The biomass,N content and N accumulation of weed and rapeseed were analyzed when the shoot biomass reached maximum.The Pielou evenness of weed community was analyzed with the Shannon index.[Results] The biomass and N accumulation of rapeseed were increased with the increases of seeding rate and nitrogen rate.The average rapeseed biomass of all N treatments with 4.5 and 7.5 kg/hm2 seeding rates were increased by 23.3％ and 45.2％ than those with 1.5 kg/hm2 seeding rate,and the N accumulation was increased by 21.2％ and 39.2％,respectively.Compared with no nitrogen treatment,the rapeseed biomass were increased by 0.9,1.7,2.2 and 2.7 times from N application 60 kg/hm2 to 240kg/hm2,respectively,and the N accumulation was increased by 1.0,2.0,3.5 and 4.4 times,respectively.The biomass and N accumulation of weeds were decreased with the increase of the seeding amount.The average weed biomass of all N treatments with 4.5 and 7.5 kg/hm2 seeding rates were decreased by 16.8％ and 25.8％ than those with 1.5 kg/hm2 seeding rate,and similarly the N accumulation was decreased by 17.3％ and 29.4％,respectively.However nitrogen supply improved weed biomass and N accumulation,but the increases were much lower than those of rapeseed.The N content in weeds was higher than rapeseed at the same treatment,and both of them were improved with the increasing of N supply.However the rapeseed was more sensitive to N fertilizer.Under N 240 kg/hm2,the average N concentration of rapeseed was increased by 46.2％,while that of weeds was increased by 24.1％,compared with the control.The ratios of N accumulation of rapeseed to weeds were less than 1 under the seeding rate of 1.5 kg/hm2,and were increased with the increase of seeding rate.The ratio in the 7.5 kg/hm2 sowing quantity and 240 kg/hm2 N rate was up to 2.2,which suggested that nitrogen competition of direct seeding winter rapeseed could be improved by high density and high N application.However,the increase of N rate could change the structure of weed population,and decrease the evenness of weed community.[Conclusions] The sensitivity of rapeseed in response to the N fertilizer and sowing amount is greater than that of weeds.The nitrogen competition ability of rapeseed can be improved by increasing the amount of N fertilizer and seeding amount.