Effect of herbicides on growth, weed infestation and physio-biochemical changes in guava (Psidium guajava L.) seedlings.

摘要

Guava is considered to be one of the exquisite, nutritionally valuable and remunerative crops. Weed is a serious menace to this crop particularly at seedling stage. Weeds compete with the crop at all stages of development for soil moisture, soil nutrient and light besides harbouring insects, pests and diseases. Therefore for normal growth and quality production, it is imperative to develop effective control measures of weeds in guava. Seeds of guava were sown in the third week of July consecutively two years in three replicates of a complete randomized design. Each replication contained 14 plots, each of 2 m x 6 m size, representing different herbicides treatments. To avoid the soil herbicide persistent effect, the experiments were conducted on separate adjoining fields with similar soil type. Four herbicides glyphosate, paraquat, atrazine and sencor [metribuzin] were used. Glyphosate was sprayed at 7.5 ml/litre at three times, 20 days prior to seed sowing, just after sowing and 20 days after germination. Paraquat at 3.0 kg/ha was sprayed 20 days after seed germination while atrazine at 3.0 kg/ha, and sencor at 1.5 kg/ha were applied on the same day just after sowing. Among these herbicides glyphosate and paraquat were very effective in controlling the weeds, in paraquate treatment Saccharum spontaneum reappeared in the month of September. On the other hand atrazine and senecor control the Kharif weed species like Dichanthium annulatum, Fimbristylis tenera, Trichodesma indicum, Launaea pinnatifida and Crotalaria medicaginea only. The post application of glyphosate reduced the leaf number and plant height, but atrazine, paraquat and sencor did not influence the plant height and their leaf number. Besides difference in plant height, variations in physiological and biochemical constituent in terms of rate of photosynthesis, chlorophyll content, nitrate reductase activity, protein and total sugar level were found in various herbicides treatments..