Fertilization on crop production under rice-oilseed rape rotation system

From the report “Effects of fertilization on crop production and nutrient-supplying capacity under rice-oilseed rape rotation system“, of Muhammad Yousaf, Jifu Li, Jianwei Lu, Tao Ren, Rihuan Cong, Shah Fahad, and Xiaokun Li, published at Nature.

The Yangtze River basin in China is a major planting area for the rice-oilseed rape rotation system, contributing 70% of the total rice and 91% of the total oilseed rape production. Conversely, the yields of rice-upland rotations faced significant decline or yield stagnation with deterioration in soil fertility.

Farmers have resorted to the use of imbalanced fertilization or excessive fertilization to maintain yield levels. This over-fertilization does not always contribute to high yield but it has recently become a common practice for farmers in China nonetheless. Unfortunately, over-fertilization decreases the efficiency of nutrient use6 and causes a series of economic and environmental problems.

Field experiments were conducted from 2011–2013 at three different sites, including Honghu, Shayang, and Jingzhou in China, to determine the effects of fertilization on enhancing crop productivity and indigenous nutrient-supplying capacity (INuS) in a rice (Oryza sativa L.)-rapeseed (Brassica napus L.) rotation.

Four mineral fertilizer treatments (NPK, NP, NK and PK) were applied in a randomized complete block design with three replicates. Crop yields were increased by 19–41% (rice) and 61–76% (rapeseed) during the two years of rice-rapeseed rotation under NPK fertilization compared to PK fertilization across the study sites.

Yield responses to fertilization were ranked NPK > NP > NK > PK, illustrating that N deficiency was the most limiting condition in a rice-rapeseed rotation, followed by P and K deficiencies. The highest and lowest N, P and K accumulations were observed under NPK and PK fertilization, respectively. The INuS of the soil decreased to a significant extent and affected rice-rapeseed rotation productivity at each site under NP, NK, and PK fertilization when compared to NPK.

Based on the study results, a balanced nutrient application using NPK fertilization is a key management strategy for enhancing rice-rapeseed productivity and environmental safety.Rice-upland rotations are important agricultural production systems in South Asian countries. The rice in rotation is followed by next crop called upland crop, and has many different sequences, where numerous grain and industrial crops could be rotated with paddy rice. E.g. rice-rapeseed, rice-wheat, rice-potato, rice-Chinese milk vetch etc. In China and other Asian countries, continuous rice planting has had a negative impact on soil properties, such as reduced soil nitrogen supply and organic carbon content. Paddy-rice-upland crop rotations have been recommended and used to improve soil quality and reduce input.