Effect of zero tillage on the nematode fauna in a rice-wheat cropping system

Resumo

Field observations and field experiments were conducted in Meerut, Baghpat and Saharanpur districts of western Uttar Pradesh, India, in 2003-2006, to investigate the effects of tillage and no tillage, in a rice-wheat cropping system, on soil nematode population densities, yield of wheat and numbers of weeds at harvest time of the wheat. In the fields used for the observations, at both sowing (November) and after harvest of the wheat crop (March/April), zero-tillage fields had population densities of plant parasitic nematodes (Tylenchorhynchus brevilineatus and Pratylenchus spp.) larger than those of conventionally tilled fields. In the field experiments, ploughing decreased nematode population densities significantly, irrespective of fertilizer application. The plots kept fallow (no ploughing + no fertilizer + no crop) had the lowest final population densities of T. brevilineatus (205/200 cm3 soil). When wheat was grown without disturbing the soil and without fertilizer application, the nematode soil population density was greatest (779/200 cm3 soil). The multiplication rate of the nematode was highest (×3.6) in the no ploughing + no fertilizer + wheat crop treatment, followed by the ploughing + fertilizer + wheat crop treatment. There were more plants of the weed Phalaris minor in the conventionally grown than in the zero-tilled crop.