ARS | Publication request: ENZYME ACTIVITIES IN SEMIARID AGRICULTURAL SOILS

Submitted to: Integrated Biological Systems Conference
Publication Type: Abstract
Publication Acceptance Date: April 14, 2003
Publication Date: April 14, 2003
Citation: Acosta Martinez, V., Zobeck, T.M., Gill, T.E., Kennedy, A.C. 2003. Enzyme activities in semiarid agricultural soils [abstract]. Integrated Biological Systems Conference. p.44.

Technical Abstract: Knowledge of biochemical processes in low carbon content soils of the semiarid regions in West Texas, USA, in response to different land management is limited. The activities of seven soil enzymes involved in C, N, P, or S cycling were compared in an Olton loam (Fine, mixed, thermic, superactive, Aridic Paleustolls) under the conservation reserve program (CRP), native rangeland (NR), sunflowers (Eriophyllum ambiguum (Gray)), continuous cotton (Gossypium hirsutum L.), or wheat (Triticum aestivum L.)-cotton rotation. Soil samples (0-5, 5-10, 10-15, and 15-30 cm) were taken in January 2001, and analyzed for organic C, total N, pH, and the activities of beta-glucosidase, beta-glucosaminidase, arylamidase, acid phosphatase, alkaline phosphatase, phosphodiesterase, and arylsulfatase. The soil pH (7.1-8.4), organic C (6.60-13.10 g kg-1 soil), and total N (0.55-1.03 g kg-1 soil) varied among the management systems. Linear regression analyses indicated that the enzyme activities were positively correlated with organic C (r values up to 0.96, P<0.01). There was a trend of positive relationship between the enzyme activities and total N, but soil pH showed the opposite trend. Enzyme activities were significantly intercorrelated with r values up to 0.98 (P<0.001). Generally, the enzyme activities (mg product kg-1 soil h-1) were significantly (P<0.05) lower under continuous cotton in comparison to the other systems. Alkaline phosphatase activity was the most predominant enzyme with values of 251, 238, 174,127, 114, and 93 mg p-nitrophenol (PN) kg-1 soil h-1 in NR, CRP, wheat-cotton rotation, sunflowers, irrigated continuous cotton, and dryland continuous cotton, respectively. The enzyme activities were lower than corresponding values reported for soils from other regions. The specific enzyme activities (mg product g-1 organic C) were significantly (P<0.05) lower in continuous cotton in comparison to the uncultivated soils (i.e., NR and CRP). The specific activities of beta-glucosidase and arylamidase showed a more pronounced decrease with increasing soil depth than the other enzymes. In general, soils under CRP or wheat-cotton rotations revealed higher enzyme activities than soils under the common agricultural practice for these regions, i.e., continuous cotton under conventional tillage.