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Nutritional Management of Microbial Polysaccharide Production and Aggregation in an Agricultural Soil
Author(s) -
Roberson Emily B.,
Shennan Carol,
Firestone Mary K.,
Sarig Shlomo
Publication year - 1995
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1995.03615995005900060012x
Subject(s) - agronomy , chemistry , fertilizer , cropping system , rhizosphere , soil water , soil organic matter , avena , crop , environmental science , biology , soil science , bacteria , genetics
Microbial extracellular polysaccharides (EPS) contribute to the stability of soil aggregates. Nitrogen supply affects microbial growth and metabolism. The effects of fertilizer and cover crop N supply on EPS production and soil aggregation were examined in an irrigated annual cropping system. Two winter cover crops, wooly pod vetch ( Vicia dasycarpa L.), a N 2 fixer, and oat ( Avena sativa L.), and three N fertilizer regimes [0, 168, or 280 kg ha −1 (NH 4 ) 2 SO 4 ‐N] were used to vary soil N supply in a California tomato ( Lycopersicon esculentum Mill.) field. Carbohydrate in the soil heavy fraction (HF, density >1.74 g mL −1 ) was found to have a monosaccharide composition consistent with microbial EPS and was used as an indicator of EPS. The HF carbohydrate content, aggregate slaking resistance, and saturated hydraulic conductivity ( K sat ) were greatest in the vetch and 168 kg N ha −1 treatments and lower in the 0 and 280 kg N ha −1 treatments. The HF carbohydrate content was significantly correlated with K sat and aggregate stability. Organic C and N, microbial biomass, and light‐fraction carbohydrate (density <1.74 g ml −1 ) were not correlated with either aggregate stability or K sat . These results demonstrate that EPS can be important factors affecting soil structure in cultivated soils and that EPS production can be managed by N supply. The HF carbohydrate content may be a useful indication of the effects of soil nutrient and organic matter management on microbial EPS production.