Soil microbial, chemical and physical properties in continuous cotton and integrated crop-livestock systems

Continuous monoculture systems can reduce soil organic matter because of low organic inputs and disturbance from tillage practices. Integrated cotton (Gossypium hirsutum) cropping and livestock production systems in West Texas may provide more sustainable alternatives to the traditional continuous cotton system and improve soil quality. Our study was conducted on a Pullman soil (Fine, mixed, thermic Torrertic Paleustolls) after 5 yr as a complete randomized block design (three replications) that compared continuous cotton and an integrated livestock-crop system with a perennial warm-season grass pasture (Bothriochloa bladhii) paddock and two paddocks (two stages) of a rotation (wheat [Triticum aestivum]-falllow-rye [Secale cerealel -cotton). Total N (average: 1.0 g kg(-1) soil) remained similar among systems and soil pH was >8.1. Organic C was higher (13.5 g kg(-1) soil) in perennial pasture compared with continuous cotton (9.0 g kg(-1) soil) at 0 to 5 cm. A similar trend was found for the soil aggregate stability. Soil microbial biomass C (C-mic,) was greater in perennial pasture (193 mg kg(-1) soil) and the rotation under rye and cotton (237 mg kg(-1) soil) compared with continuous cotton (124 mg kg(-1) soil) at 0 to 5 cm, and in perennial pasture at 5 to 10 and 10 to 15 cm. Soil microbial biomass N (N-mic) showed similar trends. Soil enzyme activities were greater in perennial pasture and the rotation (under rye and cotton) than under continuous cotton at 0 to 5 cm. The integrated crop-livestock system had higher protozoa (20:4omega6c = 1.98%) and fungi (18:3omega9c = 1.30%) than continuous cotton (20:4omega6c = 1.09%; 18:3omega9c = 0.76%). These findings suggest positive differences in soil function and sustainability of the integrated croplivestock system compared with continuous cotton.