Submitted to: Eurosoil Congress
Publication Type: Abstract Only
Publication Acceptance Date: 8/25/2008
Publication Date: 8/29/2008
Citation: Acosta Martinez, V., Dowd, S.E., Allen, V. 2008. Soil microbial community structure, diversity and functionality in integrated livestock-crop production systems compared to continuous cotton[abstract]. Eurosoil Congress. Vienna, Austria. August 25-29, 2008. Interpretive Summary:
Technical Abstract: Many regions of the world are facing soil quality and sustainability problems due to monoculture. In the Texas High Plains of US, cotton (Gossypium hirsutum) production under continuous monoculture and conventional tillage (since the 1940’s) has contributed to wind-induced soil erosion and organic matter reduction. 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 productivity and enhancing soil quality. A clay soil (Fine, mixed, thermic Torrertic Paleustolls) was studied 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, but total C (avg: 17.3 g kg-1 soil) and total N (avg: 1.5 g kg-1 soil) 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 10 years. After 5 years, soil microbial biomass C (MBC) was greater in perennial pasture (193 mg kg-1 soil) and in the rotation when sampled under rye or cotton (237 mg kg-1 soil) compared to continuous cotton (124 mg kg-1 soil), but MBC became significantly higher in all the alternative systems after 7 years. Similar trends were found for enzyme activities of C ('-glucosidase, '-galactosidase), P (alkaline phosphatase, phosphodiesterase), N ('-glucosaminidase), and S (arylsulfatase) cycling. The integrated crop-livestock systems had higher protozoa (20:4'6c=1.98%) and fungi (18:3'9c=1.30%) than continuous cotton (20:4'6c =1.09%; 18:3'9c= 0.76%) after 5 yrs. Higher mycorrhizal fungal fatty acids (18:1'9c, 16:1'5c) were detected under ungrazed areas compared to grazed areas in pasture at 0-5 cm. Results from bacterial diversity as affected by the integrated-crop livestock systems will be discussed.