EFFECTS OF GLYPHOSPHATE AND ALACHLOR ON MICROBIAL RESPIRATION, AMMONIFICATION, NITRIFICATION AND PHOSPHORUS MINERALIZATION SANDY LOAM SOIL

Abstract

Glyphosate (N-phosphonomethyl) glycne) and alachlor (2-chloro 2, 6-diethyl-N-(methoxymethyl acetanilide) were added at the recommended and twice the recommended rates, viz, 3.0 and 6.0 and 2.5 and 5.0kg/ha active ingredients respectively to a sandy loam and incubated at 60% of the soil's moisture holding capacity for 8 weeks at 30⁰C in the laboratory's Microbial respiration, ammonium nitrogen (NH -N), nitrate nitrogen (NO₃-HI) and available phosphorus (P) production were determined weekly. The herbicide treatments did not stimulate microbial respiration but rather had a negative effect (P = 0.05) during the early stage (2 - 4 weeks) of incubation. Ammonification, nitrification and phosphorus mineralization were not significantly affected also. However, the rate of nitrification was temporarily enhanced in soil samples that received twice the recommended rates of glyphosate and alachlor. High rates of the herbicides could therefore lead to increased loss of NO^-₃-N under humid conditions