Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/17/2011
Publication Date: 7/21/2011
Citation: Cotton, J.E., Moore-Kucera, J., Acosta Martinez, V., Burow, G.B. 2011. Responses of Enzyme Activities in Sandy Soils to Cropping System Changes in a Semiarid Region[abstract]. Enzymes in the Environment. July 17-21, 2011, Bad Nauheim, Germany. Interpretive Summary:
Technical Abstract: Sandy soils in the semi-arid Southern High Plains of the United States are inherently low organic matter, and when agricultural practices such as intensively tilled, low-residue cropping (e.g., monoculture cotton) are practiced, soil of organic matter becomes further depleted. Although alternative cropping options are limited in this region due to climate constraints and the limited irrigation capacity of the depleted Ogallala aquifer, drought tolerant, high-residue crops such as sorghum (Sorghum bicolor) offer viable alternative cropping systems that are both economically and environmentally beneficial. This study evaluated the short-term changes in soil functioning related to a transition from cotton to sorghum cropping systems using a suite of five soil enzyme assays targeting soil carbon (ß-Glucosidase), nitrogen (ß -Glucosaminidase), phosphorus (Alkaline Phosphatase, Phosphodiesterase) and sulfur (Arylsulfatase) cycling. Specifically we investigated two high-tonnage yield forage sorghum cultivars with different cell wall composition (typical and reduced lignin content) under 2 deficit irrigation levels (rain-fed non irrigated and supplemental irrigation at 2.88 mm day-1) and 2 biomass removal rates (100% and 50% removal). Baseline soil samples (0-10 cm) were collected in 2008 prior to sorghum planting. Sampling was repeated in 2009 and 2010. After 2 years under sorghum, all five soil enzyme activities had increased 25-38% compared to baseline soil. Certain enzyme activities (ß -Glucosidase, Alkaline Phosphatase, Phosphodiesterase) were higher (16-19%) under irrigated sorghum compared to non-irrigated. However, no differences were detected due to sorghum cultivar or the amount of biomass removed. This study demonstrated that soil enzyme activities are sensitive indicators to short-term changes in cropping systems and that positive responses were detected in a 2-year transition from cotton to a high-tonnage forage sorghum system, regardless of irrigation water level, % aboveground biomass incorporated into soil, and sorghum cultivar.