Optimizing nitrogen application patterns and amounts to improve maize yield and water-nitrogen use efficiencies in the Loess Plateau of China: A meta-analysis

Context or problem

There is an urgent need to address the contradiction between maize production and soil nutrient shortages to achieve efficient maize production with minimum fertilizer, labor and environmental costs. Determination of rational Nitrogen (N) application patterns is the key to solving this problem.

Objective or research question

N application is an effective strategy to improve maize N uptake (NU), yield and water use efficiency (WUE). However, the effects of different N application patterns on maize NU, yield and WUE vary greatly, and it is difficult to determine the great-yield and high-efficiency N application pattern for maize in the Loess Plateau region according to a single experimental study.

Methods

We synthesized 102 studies (102 sites) in the Loess Plateau region of China to evaluate the effects of different N application patterns (BU: basal urea; TU: basal and topdressing urea; S/C: slow/controlled release urea; S/CU: slow/controlled release urea mixed with normal urea) on maize NU, yield, WUE, and N use efficiency (NUE), and explored their responses to different climates, soil physicochemical properties, and field management practices.

Results

N application significantly increased the maize NU, yield and WUE. S/CU pattern significantly improved maize NU, yield and WUE the most with 110.74 %, 83.13 % and 86.21 %, respectively, compared to non-N application. S/C pattern showed the greatest increase in NUE of maize (3.47 %). Random forest analysis showed that growing season precipitation (GSP) was the most important determinant of the impact of N fertilizer application on maize NU, yield and WUE, while soil total nitrogen (TN) content was the most important determinant of maize NUE. The greatest increase in S/CU pattern yield and WUE enhanced when GSP and MAT were 200–400 mm and ≤ 10 °C, respectively. N application was more effective in increasing maize yield and WUE when the soil texture was clay loam and SOM < 10 g kg⁻¹. Film mulching also further increased maize NU, yield, and WUE. In addition, variety of “Xianyu 335” had higher effect sizes for NU, yield and WUE than “Zhengdan 958”.

Conclusions

S/CU pattern obtained greater maize yield and WUE with lower fertilizer and labor costs, the suitable rate of nitrogen application was determined to be 165.20 kg ha⁻¹ and the urea mix ratio was 65 %.

Implications or significance

The results would provide theoretical support and technical guidance for great-yield and high-efficiency green production of maize in the Loess Plateau of China.