Effect of Different Boron Application Schedules on Yields, Boron Concentration and Uptake of Rice-Wheat Rotation and Changes in Chemical Fractions of Soil Boron

The yields realized under rice-wheat rotation are generally low in the geographical regions prone to B deficiency and a sound B application schedule recommendation is required for the sustainable yields and enhanced soil fertility. The effect of different B application schedules involving different dosages and frequency of B application was investigated on yields and B nutrition of rice-wheat rotation and changes in the chemical fractions of B in soil in six years field study carried out on a sandy loam (Typic hapludoll). Based on the average grain yields of rice and wheat during the period of experimentation, application of 1.5 kg B as borax ha-1 to rice crop on alternate years was the profitable practice for mollisols as it gave an average yearly production of 5.51 t of rice grain and 4.28 t of wheat grain ha-1. The average concentration of B in flag leaves and grains of rice was much lower compared to wheat crop. The recommended schedule of B application to rice-wheat rotation resulted in a Benefit: Cost ratio of 11: 1 and also maintained the optimum level of B in soil. Most of the added B markedly increased specifically bound (0.05 M KH2PO4 extractable), ammonium oxalate (pH 3.3) extractable fractions followed by residual and organically bound fraction in the soil.