Bioavailability of Micronutrient Cations in Rice as Influenced by Inorganic Nitrogen Dynamics in Soil under Typic Haplustepts

Crop establishment methods play a vital role in the predominance of nutrient forms. Nitrogen dynamics in the soil can alter micronutrient availability and uptake. Four treatments each replicated thrice, comprising of three methods of rice establishment viz., puddled transplanted rice (PTR), unpuddled transplanted (UPTR), and direct seeded rice (DSR) in different combinations of rotation with conventionally tilled lentil (CTL) and zero till lentil (ZTL) were compared for their effect on inorganic nitrogen in the soil and its consequent effect on the micronutrient availability in soil and their uptake by rice grain. As per the results obtained from the study, the different establishment techniques with associated treatments after 7 years of continuous cultivation did not have any significant effect on general soil properties like pH, electrical conductivity (EC), organic carbon (OC), and cation exchange capacity (CEC). Treatments had a significant effect on soil nitrogen content and uptake and on soil micronutrient status and their uptake by rice as estimated after harvest of the rice crop. UPTR-ZTL crop rotation with crop residue management and biopriming with Azotobacter was found to be the most efficient management practice and performed better than the conventional crop establishment techniques like PTR and CTL systems. Nitrogen content in soil and plant N uptake showed positive correlations with micronutrient uptake by the rice grain. Significant positive correlations were obtained with the uptake of Fe, Mn, and Zn. Nitrogen dynamics (irrespective of crop establishment methods) in soil especially ammoniacal N, had a positive effect on the cationic micronutrient uptake by the crop, but results were not conclusive enough to suggest the role of N forms on uptake and translocation of micronutrient cations.