Abstract
The present study aims to assess the influences of long-term crop straw returning and recommended potassium fertilization on the dynamic change in rice and oilseed rape yield, soil properties, bacterial and fungal alpha diversity, and community composition in a rice–oilseed rape system. A long-term (2011–2020) field experiment was carried out in a selected paddy soil farmland in Jianghan Plain, central China. There were four treatments with three replications: NP, NPK, NPS, and NPKS, where nitrogen (N), phosphate (P), potassium (K), and (S) denote N fertilizer, P fertilizer, K fertilizer, and crop straw, respectively. Results showed that long-term K fertilization and crop straw returning could increase the crop yield at varying degrees for ten years. Compared with the NP treatment, the long-term crop straw incorporation with K fertilizer (NPKS treatment) was found to have the best effect, and the yield rates increased by 23.0% and 20.5% for rice and oilseed rape, respectively. The application of NPK fertilizer for ten years decreased the bacterial and fungal alpha diversity and the relative abundance of dominant bacterial and fungal taxa, whereas continuous straw incorporation had a contradictory effect. NPKS treatment significantly increased the relative abundance of some copiotrophic bacteria (Firmicutes, Gemmatimonadetes, and Proteobacteria) and fungi (Ascomycota). Available K, soil organic matter, dissolved organic carbon, and easily oxidized organic carbon were closely related to alterations in the composition of the dominant bacterial community; easily oxidized organic carbon, dissolved organic carbon, and slowly available K were significantly correlated with the fungal community. We conclude that long-term crop straw returning to the field accompanied with K fertilizer should be employed in rice-growing regions to achieve not only higher crop yield but also the increase in soil active organic carbon and available K content and the improvement of the biological quality of farmland.
Highlights
Our research indicated that the microbial diversity and community influenced rice yield and oilseed rape yield; the bacterial community had a higher impact than fungal community on the crop yield
We found that ten years of continuous crop residue management and K fertilizer application in the rice–oilseed rape rotation significantly improved the crop yield; altered soil physiochemical properties such as SOC, EOC, DOC, available K, and slowly available K; and, modified the diversity and composition of soil bacterial and fungal communities
The long-term application of K fertilizer and straw returning had a significant increase rate in yield after one crop rotation, and NPKS treatment resulted in the best effect
Summary
Crop residue is a considerable renewable resource with abundant organic carbon (C). As the country with the largest agricultural production in the world, China produces more than 800 million tons of crop straw per year, which amounts to 3.64, 0.73, and 14.78 million tons of nitrogen (N), phosphorus (P), and potassium (K), respectively [3,4]. Straw incorporation serves as the most effective way of comprehensive straw utilization compared with other ways (as burning, compost, or cooking) at present. Many research studies have confirmed that crop residue recycling could increase crop yield and maintain soil fertility [5,6,7]. With the increased awareness of environmental protection and ban on burning straw, directly returning straw to the field is being accepted by more and more farmers in China
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