ENRICHMENT OF BASMATI RICE GRAIN AND STRAW WITH ZINC AND NITROGEN THROUGH FERTI-FORTIFICATION AND SUMMER GREEN MANURING UNDER INDO-GANGETIC PLAINS OF INDIA

Zinc (Zn) deficiency is a well-identified problem in cereals, resulting in decreased crop yields and nutritional quality. Approximately half of the world's population suffers from Zn deficiency. Cereal crops play an important role in satisfying daily calorie intake in developing world, but they are inherently very low in grain-Zn concentrations, particularly when grown under Zn-deficient soils. Therefore, it is essential to increase the Zn concentration in cereal grains particularly in basmati rice. Application of Zn fertilizers or Zn-enriched [nitrogen (N)- phosphorus (P)- potassium (K)] fertilizers (ferti-fortification) offers a rapid solution for increasing Zn concentration in grain and straw. The present study was therefore undertaken to study nutrient concentrations in grain and straw, their uptake and use-efficiencies as influenced by summer green manuring (SGM) and Zn fertilization. Field experiments were conducted for two consecutive years during summer and rainy (Kharif) seasons (April–November) of 2008 and 2009; indicated that SGM and Zn fertilization had significant effects on concentrations and uptake of N, K, sulfur (S), Zn, manganese (Mn), copper (Cu), and iron (Fe) in basmati rice grain and straw. Amongst the SGM and Zn fertilization treatments, Sesbania aculeata green manuring (GM) and 2.0% Zn-enriched urea (ZEU) as zinc sulfate (ZnSO4.H2O) recorded the highest N, K, S, Mn, Cu, and Fe concentrations, and their uptake in grain and straw as well as total (grain + straw) of basmati rice compared to rest of the SGM crops and Zn fertilization treatments. In regards to Zn concentration, foliar spray of 0.2% (ZnSO4.H2O) recorded the highest values of Zn concentration in grain and straw viz. 24.1, 24.1 and 177.7, and 179.2 mg kg−1 DM during 2008 and 2009, respectively. Whereas, 2.0% ZEU as ZnSO4.H2O recorded the highest total Zn uptake viz. 3081.6 and 3089.0 g ha−1 in 2008 and 2009, respectively. The estimated values viz. partial factor productivity (PFP) and crop recovery efficiency (CRE) of applied N were the highest with Sesbania aculeata GM and 2.0% ZEU as ZnSO4.H2O treatments. But, the highest physiological efficiency (PE) of applied N was obtained after summer fallow and control (only N) viz. 25.7, 20.1 and 27.1, and 21.9 kg grain kg−1 of N absorbed in 2008 and 2009. All the Zn-use indices were also influenced significantly due to SGM crops and Zn fertilization treatments except ZnHI of basmati rice. Agronomic efficiency (AE) of applied Zn to rice crop was significantly higher with mungbean (Vigna radiata) GM and ZnO slurry Zn fertilization treatment, however, 0.2% foliar spray of ZnSO4.H2O recorded the highest Zn crop recovery efficiency (Zn CRE) viz. 57.6 and 61.6%, respectively. Overall, application of Zn fertilizer (ferti-fortification) to basmati rice through ZEU and foliar spray of 0.2% (ZnSO4.H2O) increased Zn concentration in grain and straw, resulting in greater bio-availability of grain Zn. Therefore, this would be a very important and useful strategy in solving the Zn deficiency related problems in Indo-Gangetic plains of India.