Evaluate regional potassium fertilization strategy of winter oilseed rape under intensive cropping systems: Large-scale field experiment analysis

• Published in: Field crops research 2016-07, Vol.193, p.34-42
• Main Authors: Cong, Rihuan, Li, Hui, Zhang, Zhi, Ren, Tao, Li, Xiaokun, Lu, Jianwei
• Format: Article
• Language: English
• Subjects: Brassica napus; crop yield; Economic optimum potassium rate; fertilizer rates; field experimentation; intensive cropping; Intensive cropping systems; multiple cropping; potassium fertilizers; soil; Soil indigenous K supply; technicians; watersheds; Winter oilseed rape
• ISSN: 0378-4290; 1872-6852
• DOI: 10.1016/j.fcr.2016.03.004

•Four levels of soil indigenous K supply were graded using 1437 site-year experiments.•Economic optimum K rates (EOKR) were evaluated through the yield-response model.•K fertilizer supply was near optimal in 44–56% of sites, but super-optimal at 30–43% of sites in Yangtze River Basin.•The EOKR could represent the influence of climate and planting systems, which increase yield with efficient K fertilizers input in different IKS levels. Potassium (K) fertilization is essential for winter oilseed rape (Brassica napus L.) especially in the intensive cropping systems. To evaluate the yield response to K fertilization and economic optimum K rate (EOKR) under different levels of soil indigenous K supply (IKS), we collected 1437 site-year experiments with four K application rates at the regional scale in Yangtze River Basin, with large yield range of 665–4470kgha−1. The four treatments were K0 (without K fertilization), LK (half K rate of MK), MK (recommended K rate by local technicians), and HK (1.5 times’ K rate of MK) in this study. We used K uptake under no K fertilization to represent IKS. Four IKS levels (i.e., L1, L2, L3, and L4 from lower to higher) were grouped based on the relationship between the relative yield and IKS. The results indicated that the rapeseed yield and yield increase rate of K fertilizer under the current recommended K rate by local technicians (MK) was higher than that under other K treatments across different IKS levels. However, the K application rate could be further optimized regionally. The MK rate was similar to EOKR in 44.3%-55.6% of the experimental sites (K rate difference in the range of ±10kgha−1). And in 29.6%–42.5% sites, the MK rate could be reduced across the four IKS levels. The EOKR values were 92, 85, 80 and 75kgK2Oha−1 in the L1, L2, L3 and L4 groups of IKS, respectively, which were significant lower than the MK rate in the four IKS levels. Our results can be used to evaluate soil provided the feasible method and valuable data to evaluate soil indigenous K supply and determine the regional K fertilizer rates of winter oilseed rape, especially in those countries that also plant multiple cropping systems and/or small-scale sites across the world.