Dehydrogenase and phosphatase activities in soil as influenced by the growth of arid-land crops

Abstract

SUMMARYThe distribution of dehydrogenase activity (DHA) and the activities of phosphatases were studied in the rhizosphere of four varieties each of clusterbean (Cyamopsis tetragonoloba (L.) Taub.), mung bean (Vigna radiata (L.) Wilczek), moth bean (Vigna aconitifolia (Jacq.) Marechal) and pearl millet (Pennisetum americanum (L.) Leeke) grown in pots containing soil low in available P. Activities of dehydrogenase and phosphatases were greatest 25 days after sowing and remained constant from 50 days after sowing until crop maturity. Rhizosphere soils showed higher activities than other soils: 26–158% for acid phosphatase, 66–264% for alkaline phosphatase and up to 292% for DHA. Dehydrogenase and alkaline phosphatase activities were significantly higher in the rhizospheres of legumes than in those of P. americanum.In general, the rhizospheres of C. tetragonoloba ‘HFG314’, V. radiata ‘PDM62’, V. aconitifolia ‘IPCMO344’ and P. americanum ‘RCB2’ had higher activities than those of other varieties of the same species. Acid phosphatase activity was lower than alkaline phosphatase activity and differences between species and varieties were small and nonsignificant. The results suggest that the higher phosphatase activities in the rhizospheres of some crops may increase P availability and utilization from arid soils.