Effect of Fertilizer on Competition of Job's Tear and Weeds under different Environments

Abstract

Two experiment were conducted to determine duration of competition between weeds and job's tear and major factors affecting their competition. Results at Loei Field Crops Experiment Station in 1995 indicated that weeds reduced yield of job's tear from 346.1 kg/rai to be 68.8 kg/rai. The linear relationship between yield reduction and duration of competition was expressed as Y=116.0-1X. the competition started at 10.3 DAP (days after planting) and ended at 62 DAP. Soil moisture and fertilizer significantly affected the competition. Under sufficient soil moisture supply, weed competition ended at 2 months after planting. Fertilizer application under this condition caused yield reduction due to weed competition during 30 DAP to 60 DAP at the rate of 3.8 kg/day and was remarkably greater than the rate under no fertilization (2.0 kg/day0. Under less soil moisture supply, weed competition duration prolonged to be 3 months after planting and the rate of yield reduction due to weed competition under fetilization an no fertilization were the same (1.6 kg/gay).