Abstract
Cultivation of green manure (GM) crops in intensive cropping systems is important for enhancing crop productivity through soil quality improvement. We investigated yield sustainability, nutrient stocks, nutrient balances and enzyme activities affected by different long-term (1982–2016) green manure rotations in acidic paddy soil in a double-rice cropping system. We selected four treatments from a long-term experiment, including (1) rice-rice-winter fallow as a control treatment (R-R-F), (2) rice-rice-milkvetch (R-R-M), (3) rice-rice-rapeseed (R-R-R), and (4) rice-rice-ryegrass (R-R-G). The results showed that different GM rotations increased grain yield and the sustainable yield index compared with those of the R-R-F treatment. Compared with those of R-R-F, the average grain yield of early rice in R-R-M, R-R-R, and R-R-G increased by 45%, 29%, and 27%, respectively and that of late rice increased by 46%, 28%, and 26%, respectively. Over the years, grain yield increased in all treatments except R-R-F. Green manure also improved the soil chemical properties (SOM and total and available N and P), except soil pH, compared to those of the control treatment. During the 1983–1990 cultivation period, the soil pH of the R-R-M treatment was lower than that of the R-R-F treatment. The addition of green manure did not mitigate the soil acidification caused by the use of inorganic fertilizers. The soil organic matter (SOM), total nitrogen (TN) and total phosphorus (TP) contents and stocks of C, N and P increased over the years. Furthermore, GM significantly increased phosphatase and urease activities and decreased the apparent N and P balances compared with those in the winter fallow treatment. Variance partitioning analysis revealed that soil properties, cropping systems, and climatic factors significantly influenced annual grain yield. Aggregated boosted tree (ABT) analysis quantified the relative influences of the different soil properties on annual grain yield and showed that the relative influences of TN content, SOM, pH, and TP content on annual crop yield were 27.8%, 25.7%, 22.9%, and 20.7%, respectively. In conclusion, GM rotation is beneficial for sustaining high crop yields by improving soil biochemical properties and reducing N and P balances in acidic soil under double- rice cropping systems.
Highlights
Long-term fertility experiments have been important resources for exploring nutrient cycling and performing overall assessments of soil fertility [1]
The results showed that long-term rotations of different green manure (GM) types in the doublerice cropping system significantly (p ≤ 0.05) increased grain yield and sustainable yield index (SYI)
Were 45%, 29%, and 27%, respectively, in early rice and 46%, 28%, and 26%, respectively, in late rice. Compared to those in the winter fallow system, crop yields of both early and late rice were increased over the year, but the highest increase was under the R-R-M treatment (Figure 1)
Summary
Long-term fertility experiments have been important resources for exploring nutrient cycling and performing overall assessments of soil fertility [1]. Irrigation and fertilization are the two most important factors for obtaining higher agricultural productivity and sustainability [3] Other factors, such as climate, pests, cultivars, soil types, and fertilization patterns, contribute to changing yield trends and sustainability in long-term cropping systems [4]. Due to the continuous and unwise use of fertilizers, rice (Oryza sativa) yield has increased significantly, but nutrient use efficiencies have decreased. This over fertilization has resulted in economic losses to farmers due to the misuse of expensive fertilizers but has led to degradation of the soil and affected air, and water quality [5,6]. GM improves the soil biological (microbial activities) and physical properties [11,12] and increases the carbon (C) and
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
