Study on the Fertilization Effect and Nutrient Management for Direct Seeding Rapeseed in China

A 10-year study conducted with the support of IPNI China Program, Huazhong Agricultural University demonstrated the positive impact of nutrient management on the productivity of oilseed rape in China. The results of soil investigation showed that soil pH that decreased slightly from 6.6 to 6.4, while the soil organic matter (SOM) and available N, P, K, and B contents in the main winter oilseed rape-planting regions of China were increased over the last four decades. The amount of crop stubble that annually remains in soil increased with the increase in seed yield, and at present it could reach 4 t/ha for some top farmers. This is one of the main reasons for the increase in SOM. Boron fertilization has become a common practice and it directly increased soil available B concentration.

Although compared with 1960s and 1980s, the soil fertility of oilseed rape farms in the Yangtze River Valley in 2004-2006 improved, deficiencies of N, P, K, and B in soil can still be found. This is mainly due to unbalanced fertilization and the fact that the critical soil nutrient concentrations have been revised upwards in the last few decades. The results from field trials indicate that if we measure the soil nutrient concentration when 90% of relative yield was achieved, then we can suggest that 160 mg N/kg, 25 mg P/kg, 135 mg K/kg, and 0.6 mg B/kg could be used as soil critical values. With the new values, the relative soil N, P, K, and B nutrient deficiency areas have reached 95, 89, 79, and 87% in Yangtze River valley, respectively.

Better nutrient management is one of the key factors for increasing not only seed yields, but also seed quality. This investigation shows that about 55% of the seed yield increase was contributed by balanced fertilization in recent years. The agronomy efficiency of N, P, K, and B in 2004-2006 reached their peak values. Therefore, China’s winter oilseed rape planting has benefited from soil fertility improvement and greatly increased the rational application rates of commercial fertilizers in the last four decades.