Response of soil microbial communities and rice yield to nitrogen reduction with green manure application in karst paddy areas

Abstract

Fertilizer application practices are one of the major challenges facing agroecology. The agrobenefits of combined application of green manure and chemical fertilizers, and the potential of green manure to replace chemical fertilizers are now well documented. However, little is known about the impact of fertilization practices on microbial communities and tice yield. In this study, the diversity of bacterial and fungal communities, symbiotic networks and their relationship with soil function were analyzed in five fertilization treatments (N: 100% nitrogen fertilizer alone; M: green manure alone; MN60: green manure couple with 60% nitrogen fertilizer, MN80: green manure couple with 80% nitrogen fertilizer; and MN100: green manure couple with 100% nitrogen fertilizer). First, early rice yield was significantly higher by 12.6% in MN100 treatment in 2021 compared with N. Secondly, soil bacterial diversity showed an increasing trend with increasing N fertilizer application after green manure input, however, the opposite was true for fungal diversity. Microbial interaction analysis showed that different fertilizer applications changed soil microbial network complexity and fertilizer-induced changes in soil microbial interactions were closely related to soil environmental changes. Random forest models further predicted the importance of soil environment, microorganisms and rice yield. Overall, nitrogen fertilizer green manure altered rice yield due to its effects on soil environment and microbial communities. In the case of combined green manure and N fertilizer application, bacteria and fungi showed different responses to fertilization method, and the full amount of N fertilizer in combination with green manure reduced the complexity of soil microbial network. In contrast, for more ecologically sensitive karst areas, we recommend fertilization practices with reduced N by 20–40% for rice production.Graphical Abstract

Study on the Effects of Reducing Nitrogen Fertilizer: Stabilizing Yield and Carbon Sequestration by Synergistic Utilization of Chinese Milk Vetch and Rice Straw in Double-Cropping Rice Area

“…This suggests that the use of MV and RS could decrease the amount of chemical fertilizer required by 40% while maintaining high yields, and the yield of double rice cropping was higher in the MV and RS treatments than in the CF treatment, which was similar to another study [24]. This was because both high biomass C and N inputs increase the organic matter and nutrients in the soil, improve soil structure, and promote microbial activity, thereby favoring the growth and development of rice which leads to enhanced rice productivity [4,16]. The mineral N fertilizers were able to quickly provide nutrients for crop growth, and we found that the yield under the N 60 level was lower than that under the N 100 level under the same organic addition treatment.…”

“…The report pointed out that if full N fertilizer was used together with green manure, it might lead to a decrease in microbial network complexity, reducing the types and quantities of microorganisms. Also, excessive chemical N fertilizer application might cause a decrease in soil pH, further affecting the growth of microorganisms [16]. Therefore, to protect the environment and promote the sustainable development of agriculture, it is necessary to reduce the application of chemical N fertilizer.…”

“…Therefore, to protect the environment and promote the sustainable development of agriculture, it is necessary to reduce the application of chemical N fertilizer. Researchers have found that N reduction combined with MV and RS return could facilitate the formation of rice yield components to increase rice yield and soil physical, chemical, and biological properties; improve soil quality; and reduce the negative impacts on soil and the environment in the Guangxi and Jiangxi provinces [16][17][18]. The utilization of MV and RS specifically supplied with different N levels can provide a synergistic effect for the sequestration of organic C in rice soil.…”

Effects of different ratios of organic and inorganic fertilizer on rice yield and soil physicochemical properties under conventional and controlled irrigation conditions

“…(Liu et al, 2021a) found that the addition of organic fertilizers with inorganic fertilizers in different ratios could increase soil organic matter and total nitrogen (TN) content and alleviate soil acidification to some extent. In a recent study by Meng et al (2022), organic fertilizers significantly increased the soil organic matter content and were able to improve the pH of acidic soils compared to the application of chemical fertilizers, and the same results were obtained by Cao et al (2017) and Pu et al (2022). Overall, the combination of organic fertilizer and controlled irrigation techniques can reduce the total rate of nitrogen application (Koothan et al, 2014), effectively improve soil nitrogen effectiveness in rice fields, reduce leaching losses of fertilizer nitrogen (Zhang et al, 2018) and improve sustained water and nutrient uptake by crops (Zhao et al, 2022), thus promoting yield (Liao et al, 2020).…”

Potential of Chromolaena odorata, Ipomoea carnea and Eichhornia crassipes as green manures on soil fertility index and rice production on vertisols

“…The application of green manure on farmland is useful for increasing organic matter and nutrition in the soil and improving the soil characteristics that have a positive impact on production. Green manure provides a source of plant nutrients, and can be used as an alternative to chemical fertilizers, which is extremely important in agricultural development (Pu et al, 2023). One plant that can be found in abundance and grows well in highland areas is C. odorata, although its benefits in farming are not yet widely known (Ahmad et al, 2022).…”