دانلود رایگان مقاله تنوع میکروبی خاک مربوط به کیفیت محصول در سیستم تولید گندم آلی دیم

Abstract

One of the primary goals of organic agriculture is increasing soil quality through the enhancement of soil biological diversity and activity. Greater soil microbial activity and diversity increase soil organic matter turnover and contribute to soil fertility, one of the main challenges associated with organic management. The objectives of this study were to 1) compare soil microbial abundance and activity between organic and conventional cropping systems, and 2) explore connections between soil microbial community indicators and crop productivity in organic and conventional winter wheat (Triticum aestivum)/spring wheat/winter pea (Pisum sativum) rotations. Soil and plant tissue was sampled following six years of organic and conventional management, and soil was analyzed for microbial abundance and activity. Fungal and bacterial abundance, soil enzyme activity, and soil organic carbon (C) were greater in the organic system than in the conventional system, and all four measures were positively correlated. Community-level physiological profiling (CLPP) indicated that C substrate utilization was greater in the organic than in the conventional system, though bacterial T-RFLP data did not demonstrate different community structure between systems, suggesting that management type affected bacterial community function, but not structure. Fungal T-RFLP results indicated that fungal community structure was different between the organic and conventional systems. Hay yield and tissue nitrogen (N) were greater in the organic system, and were positively correlated with fungal and bacterial abundance, but grainyield and protein were greater in the conventional system. The results of this study indicate that management type (organic vs. conventional) has implications for microbial abundance and microbial community function, and that differences in soil microbial abundance and activity likely impact crop yields and N uptake.

5. Conclusions

The results of this study found greater soil microbial abundance and activity in manure-amended organically-managed soils than in conventional soils receiving synthetic N fertilizer. The accompaniment of N fertilizer inputs with C sources likely stimulated microbial activity and provided a more optimal balance of C and N for microbial growth requirements. While no relationship between microbial activity and grain yield or quality was observed in spring wheat, greater microbial activity likely increased biomass accumulation and N fixation in the winter pea crop, both of which were greater in organically-managed than conventionally-managed soils. Greater N uptake in the legume crop may have been mediated by mycorrhizal, Rhizobial, or other yet-to-be-identified soil microbial taxa that are beneficial for plant growth. Soil microbial diversity and activity are important factors involved in increasing soil quality under organic production principles, and these processes require further characterization. The results of this study suggest that management practices that lead to increased soil microbial abundance and activity can have direct benefits for a legume (pea) crop, and could lead to greater returns for growers. Increased adoption of organic agriculture or more widespread use of organic soil amendments in conventional production systems could occur if quantifiable benefits for crop yield and quality are identified as a result of increased soil microbial diversity and activity