Effect of farmyard manure, phosphorus and zinc on blackgram (Phaseolus mungo)-wheat (Triticum aestivum) cropping sequence under Vertisols of Chhattisgarh plains

An experiment was conducted during the rainy (kharif) and winter (rabi) scasons of 1997-2000 at Raipur, to study the effect of different levels of farmyard manure, phosphorus and zinc on the productivity of 'RU 9401-2' blackgram (Phaseolus mungo L.)-'Sujata' wheat (Triticum aestivum L. emend. Fiori &. Paol.) cropping sequence. The treatments consisted of 2 levels of farmyard manure (without and with 5 tonnes/ ha), 3 levels of phosphorus (0, 8.6 and 17.2 kg P/ha) and 2 levels of zinc (0 and 15 kg ZnSO 4 /ha). Application of 5 tonnes farmyard manure/ha resulted in significantly higher yield of blackgram (599 kg/ha and wheat (1 347 Lg/ha) than without farmyard manure. The wheat-equivalent yield also followed the similar trend under this treatment. Among the phosphorus levels, 17.2 kg Piha resulted in significantly highest yield of blackgram (628 kg/ha), comparable yield of wheat (1 307 kg/ha) with 8.6 kg P /ha (1 255 kg/ha), highest wheat-equivalent yield (2 984 kg/ha) and the maximum net return (9 334 Rs/ha) Zinc levels did not show significant effect on blackgram and wheat yields. The soil-nutrient status after 3 years of experimentation also indicated build up in nutrient status of soil, even in absence of farmyard manure under blackgram-wheat cropping sequence.