Abstract
Recovery efficiency of nitrogen fertilizers has always been an important issue, especially for N fertilizer recommendation rate in cropping systems. Based on the equilibrium of N in the soil–plant system, apparent accumulated N fertilizer recovery (NREac) was determined for long-term (15-years) experiments in wheat (Triticum aestivum L.) and maize (Zea mays L.) rotations at five field sites with various soils and climate characteristics in China. The result showed that the frequency of cropping and the content of soil clay affected NREac positively and negatively, respectively. In the absence of nutrient deficiencies and other soil constraints (from NPK (nitrogen, phosphorus and potassium) in S2-CP (site2-Changping) in Beijing, S3-ZZ (site3-Zhengzhou) in Henan province and S4-YL (site4-Yangling) in Shaanxi province), NREac had a narrow range from 70% to 78% with the highest average of 75% in wheat and maize cropping system. Meanwhile, the value 75% of NERac is a rational value proved by 3414 experiments. Additionally, the nitrate-N approach suggested that nitrate-N could be utilized by subsequent crops, the amount of which is calculated by the equation −1.23 × [(NO3−-N) − 87]. Furthermore, another simpler and feasible method was proposed to maintain basic soil fertility while achieving a rational grain yield and maintaining a safe environmental upper threshold of nitrate. The present study provided a suit of methods for N fertilizer recommendations for the optimization of N applications in wheat and maize cropping system in China.
Highlights
The recovery efficiency of N fertilizers applied to crops (REN : the ratio of total N uptake by aboveground plant dry matter to the amount of fertilizer-N applied) has always been an important issue due to opposing goals [1]
Fixen and West [5] reported that fertilizer-N supplies basic food needs for at least 40% of the global population and estimated that at least 60% of humanity will eventually owe its nutritional survival to Agronomy 2018, 8, 293; doi:10.3390/agronomy8120293
S4-YL, NREac from the same treatment were always higher in the wheat–maize rotation per year than in the wheat–maize-maize rotation per 3 years
Summary
The recovery efficiency of N fertilizers applied to crops (REN : the ratio of total N uptake by aboveground plant dry matter to the amount of fertilizer-N applied) has always been an important issue due to opposing goals [1]. On the one hand global food security must keep pace with an increasing world population, but at the same time there are legitimate concerns about environmental pollution caused by excess N applied to crops [1,2]. It is estimated that food demand will rapidly increase to 2.8 × 109 t in 2030 and the corresponding consumption of fertilizer-N is predicted to be 9.6 × 107 t compared with 7.8 × 107 t year−1 in 1995/1997 worldwide [3]. In China, the total consumption of fertilizer-N has increased from 0.93 × 107 t in 1980 to 2.39 × 107 t in 2013 [4]. Environmental pollution due to excess N applied to crops is gradually becoming serious and a major cause for concern
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