INTEGRATED NUTRIENT MANAGEMENT IN RICE-MAIZE CROPPING SYSTEM

A field experiment was conducted during the kharif and Rabi seasons of 20082009 and 2009-2010 to study the effect of integrated nutrient management in ricemaize cropping system’ on sandy clay loam soil at Agricultural college farm, Acharya N.G. Ranga Agricultural University, Rajendranagar, Hyderabad, Andhra Pradesh under irrigated conditions. The main objective was to assess the influence of pre-rice incorporation of organic manures viz., green manure and farm yard manure (FYM) on immediate rice crop and their residual and cumulative effect on sequence rabi maize crop. At the same time, the effect of inorganic source of Nitrogen at different levels was also studied to assess the influence of graded Nitrogen levels on productivity of kharif rice and; residual and cumulative effect on rabi maize in relation to graded levels of Nitrogen applied to rabi maize crop. Accordingly the present experiment was planned with three organic manural options viz., no manuring, in-situ incorporation of green manure crop (Sesbania aculeata) and farm yard manure @ 10 t. ha (M1, M2 and M3, respectively) and four levels of Nitrogen viz., 0, 50, 100 and 150% RDN (N1, N2, N3 and N4) and also three more levels of Nitrogen i.e., 50, 100 and 150% RDN (N5, N6 and N7) included among sub plot treatments to observe their residual and cumulative effect on sequence crop of rabi maize in relation to different levels of Nitrogen i.e., 0, 50, 100 and 150% RDN imposed to maize crop. During kharif season, three organic manural options as main plot treatments and seven Nitrogen levels (N1, N2, N3, N4, N5, N6 and N7) as sub plot treatments were tested in a split plot design and replicated thrice. In the same experimental lay out, rabi maize was sown with three organic manural treatments imposed to kharif rice as main plot treatments and seven Nitrogen levels as sub plots; and replicated thrice. The experimental data was recorded on plant growth, development; yield attributes and yield of rice and also in rabi maize crop during both the years of study. In addition, the rice grain quality parameters were also estimated along the soil nutrient status in respect of N, P, K, Zn and Fe after harvest of each crop. The results indicated that the organic manural options i.e., in-situ incorporation of green manure crop (Sesbania aculeata) and farm yard manure @ 10 t. ha (M2 and M3, respectively) significantly influenced the plant growth of rice in terms of plant height, dry matter production, leaf area index etc., in comparison to no manuring treatment (M1). Similarly, the yield attributes and grain yield were also significantly enhanced due to both the organic manural options. Among organic treatments, in-situ incorporation of green manure (Sesbania aculeata) proved its superiority in increasing grain and straw yields of rice over farm yard manure @ 10 t. ha in the first year only (4479 and 5211 kg ha, respectively). The advantage due to M2 and M3 in increasing the grain yield was by 17.4 and 10.4% in the first year and; 19.2 and 21.1% in the second year, respectively over no manuring treatment. Similarly, the soil nutrient status (N, P, K, Zn and Fe) was also improved due to organic manural options in comparison to no manuring treatment. As regards to the influence of Nitrogen levels, increasing the levels from 0 to 150% RDN brought significant improvement in plant growth, development, yield attributes and yield of kharif rice during both years of study. Application of 150% RDN increased the grain yields to an extent of 11.8% in the first year and 8.7% in the second year over 100% RDN. Sole application of inorganic Nitrogen at different levels did not bring considerable change in the nutrient status of soil. Pre-rice organic manural treatments i.e., in-situ incorporation of green manure crop (Sesbania aculeata) and farm yard manure @ 10 t. ha (M2 and M3, respectively) significantly enhanced the growth, development, yield attributes and yield of sequence rabi maize during both the years (4224 and 3905 kg ha in the first year; and 4428 and 4499 kg ha in the second year, respectively). The influence of residual effect of prerice green manuring was more pronounced than FYM incorporation. Whereas, the residual effect of inorganic Nitrogen under different levels was not observed on growth and development of maize. Similarly, soil nutrient status was also not changed due to inorganic Nitrogen levels. While evaluating the system productivity, it was observed that integration of Sesbania green manure along 150% RDN followed by FYM @ 10 t ha in conjunction with 150% RDN recorded the highest mean rice equivalent yields (REY) of 12427 and 12067 kg ha, respectively. A close perusal of the data indicated that M2 N6 (green manure + 100% RDN) and M3 N6 (FYM + 100% RDN) were found very close to M1 N7 (no manuring + 150% RDN) indicating the beneficial effects of organic manuring in minimizing the application of inorganic with saving of 50% of RDN to both the crops of the system. Similarly, the advantage of integration of organic and inorganic sources of Nitrogen was also reflected on economic returns, wherein, M2 N7 (green manure + 100% RDN) recorded the highest B:C ratio (2.23) with 44.5% improvement in net returns over sole application of 100% RDN to both the crops. The INM concept not only enhanced the crop yields, but also benefited the soil through enrichment with N, P, K, Zn and Fe in comparison to sole application of organic and inorganic sources of Nitrogen separately. The present experimental results strongly suggest that adoption of integrated nutrient management in rice-maize cropping system is very essential from the point of productivity and sustainability.