Crop Rotation and Tillage Effects On a Thermic Ustalf On the Southern High Plains of Texas.

Considerable research has indicated that changing from plow tillage to no-, minimum- or conservation-tillage will, for many soils, result in improved soil physical, chemical, and biochemical quality.  Recently however, some researchers have reported that for sandy soils in warm temperature regimes, the benefits may not be as apparent or even be absent when compared to finer soils or soils in cooler temperature regimes.  We have completed three rotations of cotton following sorghum and two rotations of cotton following cotton following sorghum on a Thermic Ustalf at the Big Spring Field Station near Big Spring, Texas, USA.  Superimposed on these rotations are four tillage and residue management treatments consisting of 1.) conventional tillage of two passes with a disk plow followed by raising beds on 1 m spacing, 2.) ridge tillage where 1 m spaced beds are raised around the standing residues from the previous crop, 3.) no-tillage where the crop residues are shredded to within 15 cm of the surface, and 4.) no-tillage where the crop residues are left standing at full post-harvest height.  The tillage and residue management treatments have resulted in dry matter and economic crop yield differences and differences in observed wind erosion.  Net carbon in the soil and associated physical properties were not significantly affected by tillage or rotation.  Microbial biomass and community composition, and enzyme activities of nutrient cycling were significantly affected by tillage and rotation.