Integrated management systems and N fertilization: effect on soil organic matter in rice-rapeseed rotation
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Understanding the effects of long-term crop management on soil organic matter (SOM) is necessary to improve the soil quality and sustainability of agroecosystems.
The present 7-year long-term field experiment was conducted to evaluate the effect of integrated management systems and N fertilization on SOM fractions and carbon management index (CMI). Two integrated soil-crop system management (ISSM-1 and ISSM-2, combined with improved cultivation pattern, water management and no-tillage) were compared with a traditional farming system at three nitrogen (N) fertilization rates (0, 150 and 225 kg N ha−1).
Management systems had greater effects on SOM and its fractions than did N fertilization. Compared with traditional farming practice, the integrated management systems increased soil organic carbon (SOC) by 13 % and total nitrogen (TN) by 10 % (averaged over N levels) after 7 years. Integrated management systems were more effective in increasing labile SOM fractions and CMI as compared to traditional farming practice. SOC, TN and dissolved organic matter in nitrogen increased with N fertilization rates. Nonetheless, N addition decreased other labile fractions: particulate organic matter, dissolved organic matter in carbon, microbial biomass nitrogen and potassium permanganate-oxidizable carbon.
We conclude that integrated management systems increased total SOM, labile fractions and CMI, effectively improved soil quality in rice-rapeseed rotations. Appropriate N fertilization (N150) resulted in higher SOC and TN. Though N application increased dissolved organic matter in nitrogen, it was prone to decrease most of the other labile SOM fractions, especially under higher N rate (N250), implying the decline of SOM quality.
KeywordsSoil organic matter Labile fractions Integrated soil-crop system management (ISSM) N fertilization Carbon management index (CMI)
We thank the Major State Basic Research Development Programmer of the People’s Republic of China (Grant No. 2011CB100505), the National Natural Science Foundation of China (Grant No. 41171195), the Innovative Group Grant of the National Science of Foundation of China (Grant No. 31121062) and the Special Fund for the Agriculture Profession (201103003) for generous financial support. The authors also thank China Scholarship Council for providing fund to Jing Tian to pursue her study in Germany. We also thank the anonymous reviewers for their helpful comments that helped us to greatly improve the manuscript.
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