Effect of Herbicides on Potato and their Persistence in Acid Soil under Semiarid Tropical Condition

Potato (Solanum tuberosum L.) is the world’s leading vegetable crop and is grown in 79% of the world countries [1]. It is an economically important staple food in both developed and developing countries because of its high yield potential and rich nutritive values. India is the second largest potato producing country in the world after China [2]. With annual production of 37.3 million tonnes from an area of 1.83 million hectares. The problem of malnutrition and under nutrition can be largely solved if potato is accepted as a major food and not merely as a vegetable. It is a nutritious food containing practically all the essential dietary constituents. Carbohydrates are the major constituents of potato like in cereals and also contain proteins, essential nutrients and minerals like calcium, phosphorus and iron, and vitamins. Moreover, protein of potato is of high biological value [3]. There is a great potential of exporting potatoes from India both for seed and table purposes to neighboring countries of South-East Asia and Middle East. Potatoes can even be exported to some of the European countries during March-May when fresh potatoes are not available in these countries. Hence good and best management techniques and methods are followed by the farmers to increase the production and productivity in India. Weeds, the undesirable plants compete with the early stage of potato establishment and reduce the tuber yield significantly. Though they are effectively managed either by cultural means, nowadays chemical method is highly preferred since it is quick, less laborious [4]. Provides timely weed control and covers large area in a short time. Paraquat dichloride (1,1’-dimethyl4,4’-bipyridylium dichloride) belongs to bipyridylium group is a fast-acting, non-selective contact herbicide absorbed by the foliage and destroys plant tissue by disrupting photosynthesis and rupturing cell membranes. It is highly immobile in soil and i resistant to microbial degradation under aerobic and anaerobic conditions [5]. It does not undergo hydrolysis and photo degradation in aqueous solutions and the environmental dissipation occurs primarily by sorption to biological materials and soil clay particles and becomes environmentally inactive. Persistence of paraquat in soil environment is high with the field halflife of more than 1000 days [6,7]. and can be degraded to non or less toxic compounds by the UV light, sunlight and soil microorganisms [8]. However the strong adsorption to soil particles and organic matter limits its availability to plants and microorganisms with the soil Koc ranged from 8400 to 40,000,000 [9]. Increase in soil pH increases its sorption to soil particles and vice versa and the sorption is weaker in highly organic soils and remains active for long time and present up to 29 days in soil with more than 98% organic matter [10]. Since paraquat is not mobile in most soils [8]. its bound residues persist for long time until transported in runoff along with sediments. Thus the risk of ground water contamination by paraquat is not high until directly applied to water bodies for aquatic weed control [11]. Oxyfluorfen (2-Chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl benzene) is the dominant substitution pattern second generation biphenyl ethers proton herbicide [12]. introduced during 1987 and still research is continued on these groups. Oxyfluorfen is a contact herbicide used for the control of annual broadleaf and grassy weeds [13,14] as pre and post emergence and light is required [15]. for its herbicidal activity in plants like paraquat. It degrades mainly by photolysis, showed moderate dissipation with the half life of 35 days and its sorption is high in moist soils and also with high clay and organic matter content [6]. Since oxyfluorfen persist in soil and contaminate the aquatic surroundings through leaching and runoff [16]. It is considered Volume 7 Issue 3 2017