Submitted to: Agriculture, Ecosystems and Environment
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/16/2010
Publication Date: 5/15/2010
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. Agriculture, Ecosystems and Environment. 137(3-4):231-240. Interpretive Summary: Water is a significant factor limiting agriculture in many semiarid or arid regions of the world. This study is part of a larger project to develop and evaluate integrated crop and livestock systems that reduce dependence on underground water while optimizing cotton production and maintaining or improving soil quality in the Texas High Plains of US. Scientists and graduate students from USDA and Texas Tech University studied selected soil properties after 5 to 10 years under continuous cotton compared to an alternative system that suggest integration of livestock and crop production. The integrated crop-livestock system consists of a perennial warm-season grass pasture and two stages of a rotation (wheat-fallow-rye-cotton) to provide sequence grazing while maintaining cotton production. This long term study allowed detecting beneficial changes in soil microbial component and nutrient cycling under Integrated Crop-Livestock Systems that may represent positive changes in soil quality and functioning important to consider in decisions to modify the typical practice of continuous cotton.
Technical Abstract: Water availability is a significant factor limiting agriculture in many semiarid or arid regions of the world. This study is part of a larger project to develop and evaluate integrated crop and livestock systems that reduce dependence on underground water while optimizing cotton (Gossypium hirsutum) production in the Texas High Plains of US. Selected microbial, chemical and biochemical properties were studied in a clay soil (Fine, mixed, thermic Torrertic Paleustolls) during the first 10 years under continuous cotton compared to an integrated livestock-crop system with a perennial warm-season grass pasture (Bothriochloa bladhii) and two stages of a rotation (wheat (Triticum aestivum)-fallow-rye (Secale cereale)-cotton). After 5 years, total C (0-5 cm) was only higher under perennial pasture compared to continuous cotton. After 10 years, total C (avg: 17.3 g kg-1 soil) and total N (avg: 1.6 g kg-1 soil) at 0-5 cm were higher in all the integrated crop-livestock systems compared to continuous cotton (11.4 g C kg-1 and 1.1 g N kg-1 soil). After 5 years, microbial biomass C (MBC) was greater in perennial pasture (193 mg kg-1 soil) and in the rotation when sampled under rye or cotton (avg: 237 mg kg-1 soil) compared to continuous cotton (124 mg kg-1 soil), but after 7 years the MBC became significantly higher in all the alternative systems, including the rotation independent when it was sampled. Similar trends were found for the activities of '-glucosidase (C cycling), alkaline phosphatase (P cycling) and '-glucosaminidase activity (C and N Cycling). MBC, MBN and '-glucosaminidase activity were higher under non-grazed areas compared to the grazed areas at 0-5 cm, and in some cases at 5-15 cm. Integrated crop-livestock systems (rotation and pasture) in both grazed and non-grazed areas showed higher soil microbial biomass, enzyme mediated reactions of nutrient cycling and shifts in the microbial community structure with higher fungal FAMEs indicators (i.e., 18:3'9c, 16:1'5c, 18:2'6c and 18:1'9c) compared to continuous cotton in this study (between 5 to 10 yrs) at 0-5 and 5-15 cm.