Effects of Straw Returning on Soil Ammonia Volatilization Under Different Production Conditions Based on Meta-analysis

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In order to explore the response of Chinese farmland soil ammonia volatilization to straw returning to the field under different production conditions, this study used no straw returning as a control. Through the collection of published literature test data, the Meta-analysis method was used to quantitatively study the effects of different natural factors and, under the conditions of farmland management measures, the effect of returning straw to the field on the emission reduction of soil ammonia volatilization. At the same time, through partial correlation analysis, the main influencing factors of ammonia volatilization under the condition of returning straw to the field were found, and the ammonia volatilization was quantified. The results showed that the effect of straw returning on soil ammonia volatilization decreased with the increase in accumulated rainfall during the growth period and increased with the increase in average temperature during the growth period. When the soil pH was less than 6, straw returning to the field significantly promoted soil ammonia volatilization, and when the pH was ≥ 6, returning straw to the field significantly inhibited ammonia volatilization in the soil. The reduction effect of returning straw to the field on soil ammonia volatilization increased with the increase in soil clay content. When the total soil nitrogen content was <0.1% and >0.2%, returning the straw to the field significantly inhibited the volatilization of soil ammonia, and when the total soil nitrogen content was between 0.1% and 0.2%, returning the straw to the field significantly promoted the volatilization of ammonia from the soil. When the nitrogen application rate was 60-180 kg·hm-2 and the nitrogen application rate was >240 kg·hm-2, returning straw to the field significantly reduced soil ammonia volatilization (P<0.05), and when nitrogen application rate was 180-240 kg·hm-2, returning straw to the field significantly promoted ammonia volatilization in the soil. Returning straw to the field by plowing or rotary tillage significantly inhibited ammonia volatilization in the soil, whereas returning straw to the field in a mulching mode had no significant effect on ammonia volatilization. When the straw C/N>45, it significantly inhibited ammonia volatilization from the soil, and when the straw C/N ≤ 45, the straw returning to the field significantly promoted the ammonia volatilization of the soil. The reduction effect of straw returning on ammonia volatilization increased with the increase in straw-returning amount. In non-paddy fields, returning straw to the field had a significant inhibitory effect on soil ammonia volatilization, and in paddy fields, returning straw to the field had a significant effect on soil ammonia volatilization. The results of partial correlation analysis showed that in paddy fields, the average growth period and soil pH were the main factors affecting soil ammonia volatilization under the condition of returning straw to the field, and in non-paddy fields, nitrogen application rate and straw C/N were the main factors affecting the conditions. This study can provide reference for the scientific and rational use of straw to achieve ammonia volatilization emission reduction in farmland.