Leguminous Cover Crop Astragalus sinicus Enhances Grain Yields and Nitrogen Use Efficiency through Increased Tillering in an Intensive Double-Cropping Rice System in Southern China

Abstract

Chinese milk vetch (Astragalus sinicus L., vetch), a leguminous winter cover crop, has been widely adopted by farmers in southern China to boost yield of the succeeding rice crop. However, the effects of vetch on rice grain yield and nitrogen (N) use efficiency have not yet been well studied in the intensive double-cropped rice cropping systems. To fill this gap, we conducted a three-year field experiment to evaluate the impacts of the vetch crop on yields and N use efficiency in the subsequent early and late rice seasons. With moderate N input (100 kg N ha−1 for each rice crop), vetch cover significantly increased grain yields by 7.3–13.4% for early rice, by 8.2–10.4% for late rice, and by 8.6–11.5% for total annual rice production when compared with winter fallow. When rice crops received an N input of 200 kg N ha−1, vetch cover increased grain yields by 5.9–18.4% for early rice, by 3.8–10.1% for late rice, and by 6.2–11.3% for annual rice production. Moreover, comparable grain yields (11.9 vs. 12.0 Mg ha−1 for annual rice production) were observed between vetch cover with moderate N and fallow with added N fertilizer. Yield components analysis indicated that the increased tillering number was the main factor for the enhanced grain yields by vetch cover. Vetch cover with moderate and higher N input resulted in higher agronomic N use efficiency and applied N recovery efficiency compared with the fallow treatments. Here, our results showed that vetch as a winter cover crop can be combined with reduced N fertilizer input while maintaining high grain yields, thus gaining a more sustainable rice production system.

Rice-Rape Rotation Benefits to Improve Radiation and Heat Use Efficiencies and Mitigate Global Warming Potential of Paddy Cropping Systems in Central China

“…Crops followed by legume rotations usually showed promoted nitrogen accumulation and higher grain yields (Yu et al 2014;Zhu et al 2016). Sometimes, yield reduction of the main crop resulted from rotation could be attributed to the competition for nitrogen after the incorporation of the second crop residue, such as rape and ryegrass because of a high carbon/nitrogen ratio (Armstrong et al 1996;Nie et al 2019), in spite that the rotation treatments were coupled with crop residue return, which means an additional nitrogen supply during the main rice crop season (Zhu et al 2016). In this study, rotation with wheat or with rape had no significant effect on the grain yield and above ground biomass of rice for both years, possibly due to the high level of rice grain yields (ranged from 12.1 to 13.6 t ha -1 , Fig.…”

“…Previous research has confirmed that rotation in paddy cropping systems, especially those with legumes could play an important role in promoting nutrient cycling, improving soil fertility and maintaining food production by reducing fertilizer investment (Nie et al 2019). The release of environmental hazard compounds such as NO 3 leaching and N 2 O emission from farmland could also be reduced by rotation (Yu et al 2014;Machado et al 2021), or by replacing winter fallow with cover crops (Zhu et al 2016).…”

Effects of Nitrogen Forms and Application Rates on Nitrogen Uptake, Photosynthetic Characteristics and Yield of Double-Cropping Rice in South China

“…Five treatments were set: N0 (without N), N1 (urea), N2 (ammonium sulfate), N3 (ammonium nitrate) and N4 (sodium nitrate). Pure N applied in each pot was 1.62 g, equal to 180 kg/hm 2 . In order to ensure the stability of N fertilizer, 5% nitrogenous nitrification inhibitor dicyandiamide was added in all treatments.…”

“…South China locates in the tropical and subtropical regions, rich in water and heat resources. Rice can be planted several times in the area within one year [2]. To achieve better yield and quality, rice growers have applied large amounts of nitrogen (N) fertilizer in different seasons of rice production.…”

Sustainable Cropping Systems

“…The effects of a winter cover crop of Chinese milk vetch (Astragalus sinicus L.) on subsequent double-cropped rice in southern China is discussed in the article by Nie et al [45]. Under moderate and high N input, they found that a Chinese milk vetch cover crop increased grain yield of the early and late rice crops compared to no cover crop, largely due to increased tillering.…”