Long-term effects of organics and inorganic fertilizers on the distribution, transformation and nutrition of sulphur, zinc and boron in calcareous soil
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Date
2012
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Rajendra Agricultural University
Abstract
A long-term field experiment was started during rabi 1988-89 in calcareous soil at RAU, Pusa Farm in split plot design with NPK levels in main plots and organic sources in sub-plots. Rice and wheat as 35th and 36th crop were grown for present investigation. Besides yield of crops and uptake of nutrients, post harvest soil samples were analysed for general properties like bulk density, per cent pore space, water holding capacity, organic carbon, pH, EC, CEC, free CaCo3 available, N, P2O5, K2O, S, Zn and B. Soil samples were also collected from six different depths for distribution analysis of S, Zn and B. Post harvest soil samples were also fractionated for different pools of S, Zn and B.
The grain and straw yield of rice and wheat increased significantly with increasing levels of NPK fertilizer. However, the yield at 150 per cent NPK was at par with 100 per cent NPK. The yield was further increased with the conjoint use of organics in the order : compost + crop residue > compost > crop residue > no manure. The result indicated that compost @ 10 t ha-1 could be substituted with crop residues. Similarly, compost + crop residue could save 50 per cent of the recommended dose of NPK i.e. 60 kg N, 30 kg P2O5 and 20 kg K2O kg ha-1. Integrated effect of chemical fertilizers with organic manure and crop residue also augmented N, P, K, S, Zn and B uptake by crops. There was a build-up in available N, P, K and S and depletion of available Zn and B with conjoint use of chemical fertilizer with organics. Addition of different organic materials (compost/crop residue) increase the organic carbon, porosity, water holding capacity, cation exchange capacity and decreased bulk density, pH and EC. Irrespective of NPK levels and organic addition, there was an increase in the mean available sulphur with increasing depth upto 45-60 cm beyond which the values were continuously decreased. The available Zn and B content was higher in surface layer and it progressively decreased along the depth in all the treatments. There was a considerable increase in the population of bacteria, fungi and actinomycetes with continuous application of chemical fertilizers and organic manure alone or in combination. Correlation study indicated that all forms of S, Zn and B were in dynamic equilibrium and positively and significantly correlated with most of the plant parameters. Step down multiple regression equation indicated that difference in plant parameter due to various treatment could well be explained through variation in sulphate S followed by distilled water soluble-S; Zn-bound to crystalline oxide followed by Zn-bound to carbonate and amorphous oxide and oxide bound B followed by readily soluble B. The results of path analysis confirmed the direct effect of sulphate-S, Zn-bound to crystalline oxide and oxide bound-B on crop production and nutrition.
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Keywords
Soils, Calcareous, Organic fertilizers, Inorganic fertilizers, Soil nutrients