Dual purpose summer legumes and zinc fertilization for improving productivity and zinc utilization in aromatic hybrid rice (Oryza sativa)

Field experiments were conducted during 2007–08 at New Delhi, to study the effect of dual purpose summer legumes and zinc (Zn) fertilization on productivity and Zn-use efficiency of aromatic hybrid rice cv ‘Pusa Rice Hybrid 10’ (‘PRH 10’). The experiment was carried out in split plot design with 3 treatments of legume residue in main plots and seven treatments of Zn fertilization in sub-plots. The tallest plant height, number of tillers/m², dry matter accumulation/hill, leaf area index (LAI), yield attributes and grain yield of aromatic hybrid rice was recorded with incorporation of cowpea residue followed by mungbean residue. Zinc fertilization in aromatic hybrid rice increased growth parameters, yield attributes, grain and straw yields. Application of 2% ZEU (ZnSO₄.7H₂O) was found to be the best in terms of all the yield attributes, grain yield of aromatic hybrid rice, 2% ZEU (ZnO) was found very close to it. In respect to Zn concentrations in grain and straw of aromatic hybrid rice, 2% ZEU (ZnSO₄.7H₂O) recorded higher Zn concentrations in grain as well as in straw of aromatic hybrid rice. The highest agronomic efficiency (AE) was obtained with the application of 2% ZEU (ZnSO₄.7H₂O). Physiological efficiency (PE) and Zn harvest index (ZnHI) of applied Zn were also significantly influenced due to dual purpose summer legumes and various Zn fertilization treatments applied in aromatic hybrid rice. Cooking quality parameters were significantly improved by legume residue incorporation and with the application of ZEU. The highest net returns and B:C ratios of the legume-rice sequence were recorded with the legume residue incorporation and with the application of ZEU in the aromatic hybrid rice. Thus, growing of cowpea or mungbean as dual purpose summer legumes along with Zn fertilization as 2% ZEU either with ZnSO₄.7H₂O or ZnO to aromatic hybrid rice led to higher productivity, cooking quality and Zn-use efficiency in aromatic hybrid rice and higher net returns of this sequence.