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To explore the effects of N fertilizer rates on seed yield and quality of winter rapeseed, field experiments were carried out in Wuxue County, Hubei Province during 2019/2020 and 2020/2021 seasons. The experiments were set at five nitrogen application levels of 0, 90, 180, 270, and 360 kg N hm-2. Rapeseed yield, N concentration, and rapeseed quality indexes were measured at maturity stage. The results showed that N application significantly increased rapeseed yield and N content. Compared with the zero N application, the average yield increase after N application was 1548 kg N hm-2, and the average yield increase rate was up to 32.9%. Within the range of N application rate of 0--270 kg N hm-2, rapeseed yield increased significantly with the application of N fertilizer. If N application was continued, rapeseed yield did not change significantly or had a downward trend. N application mainly improved rapeseed yield by increasing the number of pods per plant. N application significantly increased protein content in rapeseed. When the N application rate was 270 kg N hm-2, the protein content was the highest. N application significantly reduced the seed oil content. For every 100 kg N hm-2 increase in nitrogen application, the seed oil content decreased by 1.6%. With the increase of N fertilizer application rate, glucosinolate, oleic acid, linolenic acid, erucic acid, and saturated fatty acids (palmitic acid and stearic acid) increased, while linoleic acid decreased in rapeseed. Rapeseed quality decreased as a whole. In conclusion, to pursue high-quality edible oil and take into account rapeseed yield, the application rate of N fertilizer was 180 kg N hm-2. The optimal application rate of N fertilizer was 270 kg N hm-2 when rapeseed yield and rapeseed cake were taken into account. [ABSTRACT FROM AUTHOR]

The application of nitrogen (N), phosphorus (P), and potassium (K) fertilizers is an important measure to increase yield in agricultural production. Continuous upland and paddy-upland anniversary multiple cropping rotation is the main planting mode of winter oilseed rape in the Yangtze River basin in China. In order to explore the effects and differences of N, P, and K on the yield and nutrient absorption and utilization of rapeseed in different rotations, a field experiment was carried out in Shayang County, Hubei Province for 3 years from 2017 to 2020. Two rotation modes of upland-oilseed rape (maize-rape) and paddy-oilseed rape (rice-rape) were adopted, and four treatments of nitrogen, phosphorus and potassium combined application (NPK), no nitrogen (-N), no phosphorus (-P), and no potassium (-K) applications on the basis of NPK were set in each rotation. The yield, yield components, and nutrient uptake of rapeseed were analyzed, the fertilizer use efficiency and soil indigenous nutrient supply were evaluated. The average results of the three-year trials showed that, compared with the NPK treatments, the -N, -P, and -K treatments in upland reduced rapeseed yields by 68.4%, 89.6%, and 7.0%, and by 71.0%, 84.7%, and 6.4% in paddy fields, respectively. Among the yield components, whether it was upland or paddy, fertilization had the greatest impact on the number of siliques, followed by the number of grains per silique, and had the least impact on the thousand-grain weight. Compared with NPK treatment, the number of siliques in upland and paddy fields was decreased by 61.6% and 52.0%, 82.0% and 67.8%, 16.2% and 19.7% due to N, P, and K deficiency, respectively. There were significant differences in the yield and nutrient absorption of rapeseed in upland and paddy field under different fertilization treatments. The yield of rapeseed in upland was about 27.2%, 15.2%, and 16.7% higher than that in paddy field in the -N, -K, and NPK treatments, while the yield of paddy rapeseed under -P treatment was 20.8% higher than that of upland. Nutrient accumulation trends were similar to the yield, except for -P treatment, the accumulation of N, P, and K in the upland oilseed rape under NPK treatment was 20.4%, 37.3%, and 4.2% higher than paddy oilseed rape, respectively. The soil indigenous N and K supply in upland was 15.0% and 20.9% higher than that in paddy field, while the supply of P in upland was 39.2% lower than that in paddy field. The recovery efficiency of N and P in upland were higher than that of paddy field, while K recovery efficiency was lower than that of paddy field. In summary, the combined application of nutrients could improve rapeseed yield and nutrient use efficiency. The significant differences in rapeseed yield and nutrient utilization among different crop rotations were affected by nutrient types. Compared with the upland, to supplement the nutrients deficiency in the soil and achieve high-yield and high-efficiency production of rapeseed, rapeseed in paddy fields needs to pay more attention to the application of N and K fertilizers, while rapeseed in upland needs to be appropriately increased in P fertilizers compared with paddy fields. [ABSTRACT FROM AUTHOR]

It is important to reduce oilseed rape (Brassica napus L.) yield loss subjected to waterlogging in the Yangtze River Basin under simplified fertilization background. How to alleviate the waterlogging loss by way of nitrogen (N) fertilizer application was studied. Three factors, including different N rates (0, 60, 120, 180, 240 and 300 kg N/hm²), N sources (controlled release urea and common urea) and water managements (waterlogging at seedling stage and normal drainage), were set in a field experiment. Yield and agronomy efficiency of oilseed rape at varying N rates were investigated, to identify effects of waterlogging at seedling on oilseed rape with different N fertilizer rates and their responses with controlled release urea one-off application (CRU1) and common urea split application (U4), respectively. Results showed that oilseed rape yield increased with the increase rate of N fertilizer application, plateaued at 240 kg N/hm². Yield of CRU1 were higher than that of U4 at 60-180 kg N/hm², but similar at 240-300 kg N/hm². N fertilizer application increased plant population density at harvest (PPDh), pod number per plant and seed number per plant, which resulted greater oilseed rape yield. Waterlogging at seedling stage decreased oil-seed rape yield by 1.1%-41.9%. The yield loss increased as N rates added, then decreased as CRU1 and U4 added to 120 and 180 kg N/hm², respectively. The largest yield loss of CRU1 and U4 were 29.8% and 41.9%, respectively. In case of waterlogging, PPDh decreased significantly (with decrease of 29.4-45.0%), but pod number per plant increased at the N rate of 0-60 kg N/hm². When N rate was at 120-180 kg N/hm², both PPDh and pod number per plant decreased by 19.5-33.7% and 1.4-17.7% once subjected to waterlogging, respectively. While as N rate was more than180 kg N/hm², both the PPDh and pod number per plant decrease was reduced (with the decrease of 5-30.9% and 3.6-9.5%, respectively). Yield losses induced by waterlogging of CRU1 were larger than that of U4 at same N rate. Waterlogging at seedling stage decreased N agronomy efficiency by 8.4-51.9%. Generally, the agronomy efficiency decrease with sufficient N supply (240-300 kg N/hm²) was less than that of insufficient N supply treatments (120-180 kg N/hm²), and CRU1 (with the average agronomy efficiency decrease of 36.5%) had greater agronomy efficiency decrease relative to U4 treatments (with the average agronomy efficiency decrease of 17.3%)). In a word, waterlogging at seedling stage had greater impact on direct-sown winter oilseed rape yield with CRU1 application relative to U4. In the area with low indigenous N supply capacity, available N topdressing with appropriate rate after waterlogging can alleviate the yield loss and ensure the high production of oilseed rape. [ABSTRACT FROM AUTHOR]

To investigate the nutrient limiting factors for a practical fertilization proposal on direct - sowing oilseed rape in Guizhou Province, fertilization field experiments were conducted using cultivar Youyan 599 (Brassica napus L.) in main rapeseed planting area of Guizhou during 2011 - 2012. Results showed that compared to no fertilization treatment (CK), seed yield of direct - sowing oilseed rape significantly increased when fertilizers were applied. Among them, NPKB treatment had the best performance with the average yield of 2189kg/hm². While compared to NPKB treatment, yield outputs decreased to 961, 342, 295 and 184kg/hm² in PKB (without N), NKB (without P), NPB (without K), and NPK (without B) treatments, respectively. It indicated that the nutrient limiting factors were ranked as N > P > K > B. Compared to farmers' fertilization practices (FFP ) treatment, NPKB treatment increased the application rate, but the production was improved significantly by 430kg/hm². Nutrient accumulation and fertilizer use efficiency were also significantly improved. Nitrogen, phosphorus and potassium nutrient accumulation (corresponding fertilizer use efficiency) increased 28.6 kg/hm² (13.5%), 9.6 kg/hm² (3.3%), 71.4 kg/hm² (23.9%) compared to FFP . As for economic profits, the revenue of NPKB treatment was increased by 1 109 yuan/hm2 compared to FFP. It suggested that the yield, nutrients accumulation and profits could be significantly improved by a combination of balanced fertilization. [ABSTRACT FROM AUTHOR]

In order to explore temporal-spatial variability of farmland soil pH at Enshi Antonomous Prefecture, Hubei, China, soil pH during the past three decades was analyzed, using the datasets of the Second National Soil Survey (1980-1983) and the Cultivated Land Quality Evaluation (2010-2013). The natural and human factors inducing the change of soil pH were evaluated to provide theoretical guidance for further soil acidification management. Results showed that acidic soil (i.e., pH＜6.5) and neutral and alkaline soil (i.e., pH 6.5-8.5) were accounted for 98.4% and 1.6% in the farmland during the period of 2010-2013, respectively. The ratio increased 61.4% for the acidic soil but decreased 61.2% for the neutral and alkaline soil as compared with the period of 1980-1983. In addition, there was no alkaline soil (pH>8.5) in the region in 2010-2013. According to the dataset of the Second National Soil Survey (1980-1983), acidic soil was mainly distributed at Laifeng, Lichuan, Xuanen and Xianfeng counties, with the area ratio of 74.4%, 63.5%, 61.3% and 60.7%, respectively. For the period of 2010-2013, the ratio of acidic soil enhanced widely which was above 96% for each county. At Enshi Autonomous Prefecture, farmland soil showed an obvious acidification trend during the past three decades, with spatial variation of higher in the eastern part and lower in the western part of the region. Furthermore, soil pH decline occurred among different land use types in different areas. Overall, farmland soil pH declined 0.90 on average, with 1.14 decrease for upland and 0.87 for paddy soil, respectively. Clearly, upland soil acidification was severe than paddy soil. Factors related to soil acidification in the Enshi Autonomous Prefecture were mainly human factors such as unreasonable fertilizer combination, fertilizer ratio change, and more base cations taking away by high crop yield.