Interaction of weed density and standing water level on rodent damage in rice fields of low country intermediate zone of Sri Lanka

Abstract

Rice is a staple crop in Sri Lanka, where rodent damage is an increasing threat. This study examined the effect of weed density and standing water level on rodent damage in rice fields. The experiment was conducted in selected farmer fields in Kurunegala district with four replicates following a standard statistical procedure. For the study of weed density, three experimental plots were demarcated, each measuring 50×50 m. Three treatments were weed-free, conventional farmer weed management practice, and un weeded. For the study of standing water level, four separate experimental plots were demarcated each measuring 50×50 m, and treatments were no standing water, farmer practice (based on water availability), 5 cm of standing water, and 10 cm of standing water. Damaged and undamaged tillers were recorded in two-week interval before harvesting. Accordingly, un-weeded (minor season – 20.56%, major season - 52.51%) and no standing water (minor - 15.33%, major -16.00%) treatments were given the highest rodent damage, while weed-free (minor - 1.81%, major – 1.48%) and 10 cm of standing water (minor - 0.67%, major – 1.00%) treatments were given the lowest damage. Meanwhile, weeds were collected from each transect by using a quadrate (36×36 cm), and their dry weight was measured. A positive linear relationship was observed between rodent damage and weed dry weight. Data were arcsine transformed and analyzed using ANOVA (SAS 9.1.3), with means compared using the LSD test at P < 0.05. These studies indicate that effective weed management and adequate water availability reduce rodent damage in rice fields.