Abstract:

【Objective】 The objective of the study was to investigate the current soil nutrient status of oilseed rape-cultivated soil in typical winter oilseed rape production region in China, especially for soil micronutrients status. It would provide critical reference for optimizing fertilizer strategy of winter oilseed rape. 【Method】 430 soil samples distributed in the typical winter oilseed rape production regions in 14 provinces around the Yangtze River Basin were sampled from April to May, 2018. Soil chemical properties, including soil organic matter, total nitrogen (N), soil available phosphorus (P) and potassium (K), pH, soil available calcium (Ca), magnesium (Mg), sulfur (S), iron (Fe), manganese (Mn), copper (Cu), zinc (Zn) and boron (B), were determined. Referring to the second national soil survey and the classification index of soil available P, K and B in rapeseed-cultivated soil, soil nutrient status of rapeseed-cultivated soil was clarified, and the soil nutrient characteristics under different regions (upper, middle and lower Yangtze River Basin), planting systems (paddy-oilseed rape and upland-oilseed rape rotation) and seed yield levels (<2 000 kg·hm ^-2, 2 000-3 000 kg·hm ^-2 and >3 000 kg·hm ^-2) were also analyzed. 【Result】 Results showed that the average soil organic matter, total N, soil available P and K, pH, soil available Ca, Mg, S, Fe, Mn, Cu, Zn and B content in the typical winter oilseed rape production region around the Yangtze River Basin were 25.9 g·kg ^-1, 1.47 g·kg ^-1, 27.5 mg·kg ^-1, 131.1 mg·kg ^-1, 6.04, 2 436.1 mg·kg ^-1, 225.7 mg·kg ^-1, 22.6 mg·kg ^-1, 212.3 mg·kg ^-1, 89.7 mg·kg ^-1, 3.84 mg·kg ^-1, 4.03 mg·kg ^-1and 0.45 mg·kg ^-1, respectively. More than two-thirds of soil organic matter and total N content belonged to the medium class or above. For soil available P content, the proportion of the rich, medium and deficient class accounted for one-third, respectively. While 63.8% of soil available K content was deficient. For soil available Fe, Mn and Cu, all soils belonged to the medium class or above. Only about 8.4% and 12.2% of soils were soil deficient Ca and Zn soil, respectively. The proportions of deficient Mg, S and B soils accounted for 24.2%, 36.0% and 83.5%, respectively. Soil nutrient contents in the upper, middle and lower Yangtze River Basin were different, however, the distributions of soil nutrient status in different regions were similar. There were significant differences on soil nutrient content between paddy and upland soils. The rapeseed-planting soils in paddy-oilseed rape rotation showed significant higher soil organic matter, total N, soil available S, Fe and Zn content. Soil nutrient characteristics under different seed yield levels were slight different. Soils with high rapeseed yield (>3 000 kg·hm ^-2) revealed higher soil available K, Ca, Mg and B content compared with the soils with low rapeseed yield (<2 000 kg·hm ^-2). 【Conclusion】 Soil nutrients content in the typical winter oilseed rape planting area around the Yangtze River Basin was increasing, nevertheless, the percentages of deficient K and B soils were still huge, and soil available Mg and S were gradually becoming the potential limiting factors of winter oilseed rape. Therefore, in the current production of winter oilseed rape in the Yangtze River Basin, we should pay more attention to the rational application of chemical fertilizers, applying N fertilizer continuously and reasonably, increasing K and B fertilize application, reducing P fertilization rate in western Yunnan, northern Guangxi and southern Hunan depending on soil available P content, and focusing on the application of S and Mg fertilizer in northern Guangxi, southern Hunan, and northern Jiangxi.

Key words: winter oilseed rape, soil nutrients, soil nutrients status, soil nutrients classification, soil medium-micro nutrients