EFFECT OF COMPOSTING PROCESS ON RELEASING NITROGEN PHOSPHORUS AND POTASSIUM

Abstract

This research studied the release of nitrogen (N), phosphorus (P), and potassium (K) under composting conditions in ventilated sacks containing fermented raw materials which consist of pig manure, cow manure, molasses, bran, fish marinade and bat guano in the proportion of 53.89%, 37.50%, 3.43%, 3.15%, 1.14% and 0.94% respectively for a period of 105 days. The samples were collected on days 0, 3, 7, 14, 21, 28, 35, 42, 49, 63, 77, 91, and 105. From this studied, the development of compost maturity was divided after temperature into 3 stages: the initial stage (day 0), the thermophilic stage (day 1-27), and the mature stage (since day 28). The results showed that organic matter (OM) together with carbon by nitrogen ratio decreased throughout composting (r=-0.387, P<0.05 and r=-0.630, P<0.01, respectively).
This indicated the activities of microorganisms utilizing the OM along with releasing ionic nutrients as shown by elevating electrical conductivity (EC) corresponding with time (r=0.895,P<0.01).The N, P, and K were increased and reached their summits within 49 days with the rate of 0.0737, 0.1681, and 0.1217 mg/day, respectively. Later, the amounts of all three elements tended to decline towards the end of composting. Moreover, the latter ECs were slightly increased over the criteria of Thai compost standard. Therefore, the compost should not be kept longer than 63 days. Otherwise, the qualities tended to decline and were not appropriate to use.