Soil microbial diversity and activity linked to crop yield and quality in a dryland organic wheat production system

Authors: TAUTGES, NICOLE - Washington State University; SULLIVAN, TARAH - Washington State University; Reardon, Catherine - Kate; BURKE, IAN - Washington State University

Submitted to: Applied Soil Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/4/2016
Publication Date: 9/9/2016
Publication URL: https://handle.nal.usda.gov/10113/5598560
Citation: Tautges, N.E., Sullivan, T.S., Reardon, C.L., Burke, I.C. 2016. Soil microbial diversity and activity linked to crop yield and quality in a dryland organic wheat production system. Applied Soil Ecology. 108:258-268.

Interpretive Summary: One of the primary goals of organic agriculture is increasing soil quality. It is thought that by enhancing the soil biological diversity and activity, soil organic matter turnover can be improved and contribute to greater soil fertility. The objectives of this study were to 1) compare the amount and activity of soil microbes in organic and conventional cropping systems, and 2) explore connections between the soil microbial community function (activity) and crop productivity in organic and conventional winter wheat (Triticum aestivum)/spring wheat/winter pea (Pisum sativum) rotations. Soil and plant tissues were sampled following six years of organic and conventional management. The amount of fungi and bacteria, activity of soil enzymes, and soil organic carbon (C) were greater in the organic system than in the conventional system. Community-level physiological profiling (CLPP), an indicator for the capacity of the soil community to use different nutrient sources, indicated that C substrate use was also greater in the organic than in the conventional system. The fungal, but not bacterial, community structure differed between the organic and conventional system indicating that fungi were more sensitive to management strategy than bacteria. Hay yield and tissue nitrogen (N) were greater in the organic system, although grain yield and protein were greater in the conventional system. The results of this study indicate that management type (organic vs. conventional) influences the amount and activity of the soils microbes, and that differences in the microbial communities may relate crop yields and N uptake.

Technical 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. 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 grain yield 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 microbial abundance and activity likely impact crop yields and N uptake.