ALLELOPATHIC EFFECT OF WEEDS ON PHYSIO-CHEMICAL PROPERTIES OF RICE AND NUTRIENT STATUS OF SOILDipul Kalita
The paper describes the allelopathic effect of some common weeds on physio-chemical properties of rice and nutrient availability in soil. Dry plant material of weeds like Ageratum conyzoides, Borreria his pida, Cynodon dactylon and Cyperus rotundus were incorporated into the pot at different concentration (Dry weight of weed : post mixture) and rice seeds (Var. Govind) were sown in the pot. Result showed that seedling emergence and seedling growth was inhibited by all the weed residues at highest (1 : 5) concentration. Number of leaves was reduced at lower concentration (1:15) at early stage whereas leaf area affected at higher concentration both 25 and 50 days after sowing (DAS). Total chlorophyll was considerably reduced by the weed residue of C. dactylon at both the stages. Nitrate reductase (NR) activity in the leaves of rice was reduced during early stage of growth only. N,P,K content of rice plant reduced even at lower concentration also. Soil available nitrogen and potassium contents were decreased linearly with increase concentration of weed residues. Where as available phosphorus was increased along with the increase of residue concentration.
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