Effect of Organic Amendments on Selected Soil Enzyme Activities.

ABSTRACT

 

Modern agriculture involves intensive application of agricultural chemicals to provide nutrients and achieve pest control. Though their application has tremendously increased yields, their long-term environmental impact on soil biological processes has been a major concern.  Any impact of land use practices on biochemical processes can have long-term consequences on soil quality and global carbon, nitrogen and phosphorus budgets.  This calls for exploration of more sustainable land use practices which are less dependent on agricultural chemicals. Soil enzyme activities have been proposed as a means for assessing changes in soil quality caused by contaminants. This study was collaboratively conducted at the University of Maryland and Tuskegee University to assess the possible impacts of alternate land use practices on soil quality as measured by selected soil enzyme activities. At the University of Maryland, Surface soil samples (15cm) were taken from plots where two varieties of tomatoes Debarao Plum (V1) and Brandywine Red (V2) were grown in the previous year in a randomized complete block designed experiment involving four treatments. The four treatments included control soil which did not receive any organic amendment (T1), soil treated with mycorrhiza (T2), soil treated with poultry litter (T3), and the soil treated with mycorrhiza + poultry litter (T4). Soil samples were collected randomly throughout the plots; then, transported to the soils laboratory at Tuskegee University and analyzed for beta glucosidase and acid phosphatase activities. Results showed no significant effect (p=0.05) of soil amendment or tomato variety on soil pH.  Application of all organic amendments significantly (p=0.05) increased activity of phosphomonoesterase in the order T1 < T3 < T2 < T4 while activity of beta glucosidase was only significantly affected by T4. Current findings indicate that organic amendments used in the study may affect P transformation in soils.

Key words: Organic amendments, Soil enzymes, Soil quality