Submitted to: International Soil Conservation Organization Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 8/27/2010
Publication Date: 11/13/2010
Citation: Acosta Martinez, V., Bell, C., Morris, B., Zak, J., Allen, V.G. 2010. Long-term soil microbial community and enzyme activity responses to an integrated cropping-livestock system in a semi-arid region[abstract]. International Soil Conservation Organization Conference Proceedings. November 7-13, 2010, Santiago, Chile. Interpretive Summary:
Technical Abstract: This study is part of a larger long-term project to develop and evaluate integrated crop and livestock systems in order to reduce dependence on underground water sources by optimizing cotton (Gossypium hirsutum) production in the Texas High Plains of U.S. Microbial communities and activities were evaluated (between years 7 – 10) in a clay loam soil (Fine, mixed, thermic Torrertic Paleustolls) under continuous cotton compared to an integrated cropping-livestock system. In the integrated system, steers grazed in sequence a perennial warm-season grass ‘WW-B. Dahl’ old world bluestem (Bothriochloa bladhii) paddock, and then rye (Secale cereale L.) and wheat (Triticum aestivum L.) grown in two paddocks (stages) of a rotation with cotton. Our previous studies after 5 years showed greater microbial biomass C (MBC) in perennial pasture (193 mg kg-1 soil) and the rotation when sampled under rye or cotton (average of 237 mg kg-1 soil) compared to continuous cotton (124 mg kg-1 soil) at 0-5 cm. After 7 years, MBC became significantly higher in the rotation independent of the crop compared to continuous cotton in this study. At the end of 10 yrs, total C was higher in both the rotation and pasture of the integrated cropping-livestock system (average across grazing treatments: 17.3 g kg-1 soil) compared to continuous cotton (11.4 g C kg-1 soil). Soil MBC and several enzyme activities (EAs) were higher under non-grazed areas compared to grazed areas within the integrated cropping-livestock system in some samplings. Microbial community structure of pasture soil showed higher FAME indicators for G- (i.e., a17:0 and cy19:0) and actinomycetes (i.e., 10Me17:0) under grazed areas compared to non-grazed areas, but overall, pasture showed higher fungal populations compared to continuous cotton. The rotation showed intermediate sum of bacterial FAME indicators among systems (continuous cotton > rotation >pasture) and a tendency for numerically higher fungi:bacterial ratios compared to continuous cotton.