Assessment of avoidable yield loss in cotton (Gossypium barbadense L.) by fumigation with metham sodium
AbstractFumigation of Rotyienchulus reniform is-infested fields in U.S.A. has been reported to increase the yield of cotton (Jones et al., 1959; Thames et al., 1971). Results of field experiments conducted at Coimbatore, India, for assessment of avoidable yield loss in cotton (Gossypium barbadense L.) cv. Suvin are reported in this paper. Two replicated field trials were conducted during 1978-79 and 1979-80 in a black clayey loam soil. One set of eight plots was fumigated with metham sodium 32% at the rate of 500 l/ha in 5 cm of standing water, 15 days before sowing. Eight non-fumigated plots were maintained as controls. A paired plot design was adopted with a plot size of 5 X 4 m. The crop was given the recommended dosages of fertilizers containing 40 kg N, 40 kg P and 40 kg K/ha as basal dressing and top dressed with 40 N/ha, 45 days after sowing and protected from insects by foliar application of carbaryl 0.1 % at 500 l/ha. The nematodes were extracted from soil samples by a combination of sieving and Baermann funnel technique. The increase in yield due to soil fumigation was considered as the avoidable yield loss. The mean soil population of R. reniformis in the non-fumigated plots at the time of sowing was 229 and 273 nematodes/200 g of soil in 1978 and 1979 trials respectively. Plant-parasite nematodes were not detected in fumigated plots at time of sowing. The avoidable yield loss of seed cotton was 17.4% in the first trial and 9.5% in the second trial (Table I).