Long-term (16 years) Influence of Surface Crop Residue Application on Soil Chemical Zn Fractions and Zn Uptake by Sorghum {Sorghum bicolor (L.) Moench} and Cowpea {Vigna unguiculata (L.) Walp} Crops Under Minimum Tillage in Rainfed Alfisol Soil

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A study was conducted to evaluate the long-term (16 years) influence of different levels of surface crop residue applications on chemical Zn fractions in soil and their relationship with uptake and crop yields in sorghum and cowpea crops, grown under minimum tillage in rainfed Alfisol soil at Hayathnagar Research Farm of ICAR-Central Research Institute for Dryland Agriculture, Hyderabad, India.Results revealed an influence of long-term crop residue application under minimum tillage on soil chemical Zn fractions viz., water soluble + exchangeable zinc (Zn-CA), zinc specifically sorbed by inorganic sites (Zn-ACC), zinc specifically sorbed by organic sites (Zn-PYR), zinc occluded by free oxides (Zn-OX), residual zinc (Zn-RES), available zinc (Zn-DTPA) and total zinc (Zn-TOT) and also on Zn-uptake and grain yields of both sorghum and cowpea crops.Multiple regression studies indicated a positive influence of the Zn-ACC, Zn-DTPA and Zn-TOT on Zn-uptake by sorghum, while the sorghum grain yield was positively influenced by Zn-ACC, Zn-PYR, Zn-DTPA and Zn-TOT fractions.The Zn-uptake by cowpea was positively influenced by Zn-PYR, Zn-OX, Zn-RES, Zn-DTPA and Zn-TOT, while the cowpea yield was positively influenced by Zn-CA, Zn-ACC, Zn-RES, Zn-DTPA and Zn-TOT.The Common Fractions of Zn (ZnCF) which showed crop specificity towards both uptake of Zn by sorghum and its grain yield were: Zn-ACC, Zn-DTPA and Zn-TOT.Whereas the ZnCF for cowpea were: Zn-RES, Zn-DTPA and Zn-TOT.Thus, these results have significance and importance in managing the zinc (Zn) nutrition in soils.

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