Mode of copper fertilization in a typic ustipsamment under soybean-wheat cropping sequence

A field experiment was conducted for three years starting from 2002 to 2004–05 on a loamy sand soil (DTPA-Cu 0.27 mg kg⁻¹ soil) classed as a Typic Ustipssament to study the effect of mode of Cu fertilization on the yield and Cu nutrition of soybean and wheat grown in rotation. The treatments consisted of one time soil application of 5 and 10 kg Cu ha⁻¹ to first soybean crop only and three foliar applications each of 0.2, 0.4 and 0.6% copper sulphate (CuSO₄.5H₂O) solution to each crop at weekly intervals. Grain yield of soybean increased significantly by 2.7 q ha⁻¹ (11.1%) over control with soil application of 5 kg Cu ha⁻¹ during first year. Averaged over three years, its yield increased significantly by 2 q ha⁻¹ (9.0%) over control with application of 5 kg Cu ha⁻¹. However, the nonsignificant differences between mean grain yield of soybean produced with soil application of 5 kg Cu ha⁻¹ and three foliar applications of 0.2% CuSO₄.5H₂O proved them to be equally efficient in meeting the Cu requirement of soybean grown in soils with marginal Cu supplying capacity. The residual effect of soil applied Cu as well as foliar application of Cu on the grain and straw yield of wheat was not significant during the period of study. Concentration and uptake of Cu by grain and straw of both the crops increased significantly over control with Cu fertilization irrespective of the mode of their application. Availability of Cu in soil increased while that of Zn decreased significantly due to soil application of Cu.