Biological productivity of vertisol cultivated with field pea under nitrogen fertilization conditions

Abstract

This study evaluates the effect of different rates of mineral nitrogen fertilizer on ammonifier counts, protease activity and some chemical characteristics of vertisol (pH, phosphorus and potassium levels) under field pea cultivation. Increasing rates of mineral nitrogen fertilizers (20, 40 and 60 kg ha-1) combined with standard rates of phosphorus and potassium (75 and 60 kg ha-1, respectively) were incorporated prior to seeding, with their effect on the above biological parameters being monitored during two stages of field pea development (pod formation and wax-ripe stage), and their effect on soil chemical characteristics after field pea harvest. The results show that the use of these fertilizers led to a significant decrease in ammonifier counts in the first stage of the study (particularly the 60 kg ha-1 rate), and a non-significant effect in the wax-ripe stage. Conversely, protease activity was significantly increased by lower fertilization rates (20 and 40 kg ha-1) during the first period of the study, and by all three nitrogen fertilization rates at the milk-wax ripeness stage. The use of these fertilizers did not affect soil pH, unlike readily available phosphorus and potassium levels.