Impact of soil management and two botanical insecticides on urease and invertase activity

Yard waste compost provides an organic amendment useful for improving soil structure and nutrient status. The activities of the enzymes hydrolyzing urea (urease) and sucrose (invertase) in the rhizosphere of potato plants were determined under field conditions. Soil urease and invertase activities were monitored in compost amended soil, grass buffer strips, and in adjacent bare soils during 35 d following soil treatment. Soil urease activity was increased by application of yard waste compost compared to untreated soil which provide evidence of increased soil microbial population following application of compost. Some transitional effects on urease activities were observed following Pyrethrins and Neemix-4E application, these effects were neither drastic nor prolonged enough to be considered deleterious to the soil microorganisms and their activities important to soil fertility. No relationship was found between invertase activity and the three management practices or soil organic matter content. It is, suggested that application of botanical insecticides like pyrethrins and Neemix-4E may be useful in delaying urea fertilizer mineralization to maintain N in a form less leachable, so that the duration of N availability to plants is prolonged. The present study may also provide information on urease activity as a sensitive bioindicator of soil quality that reflects the effects of land management on soil quality and may assist land managers in monitoring long-term productivity and sustainability of agricultural lands.