Phytosociological Attributes Of Weeds In Rice Fields Of North Costal Andhra Pradesh, India

Weed-crop competition is critical in obtaining crop yields because of greater competition ability of weeds than the crops. Weeds deplete large quantities of mineral nutrients and moisture more efficiently than the crop plants and thrive better over the crops in drought conditions. They shade the crop seedlings and occupy space where crop plants should grow their roots. Weeds have higher contents of nutrients than crop plants; they grow faster and absorb nutrients more efficiently and thus limiting the availability of the same to crop plants. Besides, the weeds inflict allelopathic effects on crop plants which are large through their depressive root exudates. The Important Value Index calculated for the individual weed species encountered in the rice crop fields revealed interesting results. The analysis on the frequency classes of weed species encountered in rice crop field revealed interesting results. A total of 65 weed species (29 dicots, 36 monocots) were recorded from 60 quadrates combining three field sites. Out of 65 species: A class is represented by 40 species followed by 20 under B, 2 under C and 3 under D, no single species under E this results showing the heterogeneity of weed vegetation.