Zinc requirement of soybean (Glycine max) - wheat (Triticum aestivum) cropping sequence in some swell-shrink soils

Abstract

A study was conducted on 6 swell-shrink soils through laboratory and green-house experiment on zinc requirement of soy be all (Glycine max L.) -wheat (Triticlim aestivum L. emend. Fiori & Paol.) cropping sequence. From the incubation study, mathematical relationship between added zinc and built-up soil zinc was worked out. Soil DTPA-Zn levels were built up to 0.5, 1.0, 1.5, 2.0, 3.0 and 6.0 ppm by adding desirable amount of zinc through ZnSO₄.7H₂ O. Soybean and wheat were grown in rotation in these treated soils. Results indicated that 21.5 to 33% of the added zinc contributed towards the pool of DTPA-Zn in soils. Optimum dry matter yield of soybean was obtained at the built up DTP A -Zn level of 1.0 ppm in all the soils. The initial build up DTPA-Zn also showed significant residual effect on the following wheat crop. The DTPA-Zn contents of 1.1 to 1.2 ppm were found to be adequate for the optimum wheat dry matter production in these soils. It was concluded that the zinc requirement of soybean -wheat cropping sequence could be met by building up the DTPA-Zn content of the soils to 1.5 ppm at the beginning of the cropping sequence.