Residual effect of summer green manure crops and Zn fertilization on quality and Zn concentration of durum wheat ( Triticum durum Desf.) under a Basmati rice-durum wheat cropping system

Field experiments were conducted during the summer-rainy (June-November) and winter (November-April) seasons of 2009-2010 and 2010-2011 at the research farm of the Indian Agricultural Research Institute, New Delhi, India. The objectives were to determine the residual effects of zinc (Zn) fertilizer sources [Ethylene diamine tetra acetic acid (EDTA)-chelated Zn (12% Zn), ZnSO(4)7H2O (21% Zn), ZnSO4H2O (33% Zn), ZnO (82% Zn) and ZnSO(4)7H2O+ZnO (50%+50%)] and summer green manure crops [Sesbania aculeata (dhaincha), Crotalaria juncea (sunhemp) and Vigna unguiculata (cowpea)] on yield, Zn concentration and quality of durum wheat (Triticum durum Desf.) under a Basmati rice-durum wheat cropping sequence. Basmati rice was harvested at maturity and durum wheat (variety PDW 291) was grown to evaluate residual effects of Zn fertilizer sources and summer green manure crops. Beneficial residual effects of Zn fertilizer sources and summer green manures on durum wheat response were observed, with significant increases in all of the determined parameters, in comparison with the control (no Zn application or summer fallow in preceding Basmati rice). The rates of increase varied among Zn sources and summer green manures. Residual effect of S. aculeata incorporation led to a significant increase in grain and straw yields, Zn concentration and quality parameters of durum wheat. Among the Zn fertilizer sources, residual effect of EDTA-chelated Zn was found to be the greatest with respect to grain and straw yields, Zn concentration and quality parameters. Highest Zn concentration in durum wheat grain and straw was recorded with residual effect of EDTA-chelated Zn, followed by ZnSO(4)7H2O, ZnSO4H2O, ZnSO(4)7H2O+ZnO, ZnO and control. S. aculeata incorporation and EDTA-chelated Zn treatments were found to be the best combination with respect to residual effects for higher quality durum wheat production.