Influence of conjuctive use of organic and inorganic source of nutrients in rice (Oryza sativa) on crop growth, yield components, yield and soil fertility in ricesunflower (Helianthus annuus) sequence

A field experiment was carried out during 2001 and 2002 at Agricultural College Farm, Rajendranagar, Hyderabad, to study the effect of conjunctive use of nutrients in rice on rice (Oryza sativa L.)–sunflower (Helianthus annuus L.) cropping system. Rice fertilized with 75% recommended level of 120 kg N/ha and supplemented with 25% N through organic sources removed more N,P and K from the soil and gave significantly more seed yield (39.57 q/ha) than by the application of N through the fertilizer alone. The yield was increased to 43.67 and 42.91 q/ha by substituting 25% N through the bulky organic manure of FYM and vermicompost. The substitution of 25% N through green leaf manures, viz. Gliricidia and sunnhemp, increased the production to 41.83 and 43.90 q/ha.

Plant height, capitulum diameter, filled seeds/capitulim and seed yield of sunflower were significantly reduced by reducing the level of fertilizers to 75 or 50% of the recommended level of 80, 50 and 30 kg/ha NPK. The crop gave mean seed yield of 8.18 q/ha with the recommended level of 120 kg N/ha to preceding rice through the fertilizer. But the residual fertility of nutrients by the application of 75% N through fertilizer and rest through FYM or vermicompost to rice significantly increased the seed yield of sunflower to 9.23 and 9.14 q/ha respectively. Substitution of 25% N through Gliricidia or sunnhemp to rice also significantly increased the seed yield of succeeding sunflower to 8.82 and 8.70 q/ha. The soil-available N, P and K was also more by the conjuctive source of fertilizer and organic manures applied to rice in rice–sunflower cropping system compared to the initial values.