Effect of preceding crops and their residues on availability of zinc in a calcareous Zn-deficient soil

Limited information is available on the effect of preceding crop on phytoavailability of zinc (Zn) in soil. This pot experiment examined the effect of four preceding crops including clover, sunflower, safflower, and sorghum residues on shoot and grain Zn uptake by two wheat genotypes differing in Zn-deficiency tolerance Back Cross and Kavir in a calcareous Zn-deficient soil. Incorporation of all preceding crop residues into the soil significantly increased organic matter (OM) content, dissolved organic C (DOC), and diethylene triamine pentaacetic acid (DTPA) extractable Zn concentration in the soil. Residues of safflower and clover had the greatest effect on increasing DOC. Shoot and grain Zn concentrations were increased by incorporating all pre-crop residues into the soil although this increase was greater at safflower and clover treatments. Incorporation of sorghum residues into the soil had a negative effect on shoot and grain dry matter yield of wheat. Incorporation of safflower and clover residues into the soil increased Zn uptake by wheat shoot and grain. There was a positive significant correlation between shoot and grain Zn concentration with DOC in soil solution. It shows that DOC, produced from decomposition of crop residues, has facilitated Zn uptake by roots of wheat plants and particularly its transfer to grains.