www.IndianJournals.com Members Copy, Not for Commercial Sale Downloaded From IP - 203.129.216.58 on dated 9-Nov-2015 AGRICULTURAL RESEARCH COMMUNICATION CENTRE www.arccjournals.com/www.ijarjournal.com *Corresponding author’s e-mail: sovan.dta@gmail.com. 1 Present address: Central Institute of Temperate Horticulture, Regional Station – Mukteshwar, Nainital – 263 138, India. Indian J. Agric. Res., 49 (5) 2015 : 414-420 Print ISSN:0367-8245 / Online ISSN:0976-058X Improving use efficiency of applied phosphorus fertilizer by zinc fertilization in Basmati rice-wheat cropping system Sovan Debnath* 1 , S.P. Pachauri and P.C. Srivastava Department of Soil Science, G.B. Pant University of Agriculture and Technology, Pantnagar – 263 145, India. Received: 06-09-2014 Accepted: 02-07-2015 DOI: 10.18805/ijare.v49i5.5803 ABSTRACT Rice-wheat rotation is the most important cropping system of the Indo-Gangetic plains. On-farm experiment was conducted to reveal the effect of Zn fertilization on yield, uptake of nutrient, utilization efficiency (UE) and grain output per unit of fertilizer use through agronomic efficiency (AE) of P and Zn in rice-wheat rotation. The experiment was conducted with rice (cv. Pusa Basmati 1) and wheat (cv. UP–2425) by imposing twelve treatments involving four different doses of P (0, 20, 40 and 60 kg P 2 O 5 ha -1 ) and three different doses of Zn (0, 2.5 and 5.0 kg Zn ha -1 ) with three replications. The yield of basmati rice was not significantly influenced by P×Zn interactions however, for wheat, a conjoint dose of 60 kg P 2 O 5 and 5 kg Zn ha -1 gave the highest grain yield (5.43 t ha -1 ). Phosphorus utilization efficiency (PUE) of wheat was higher compared to basmati rice however, the reverse was true for zinc utilization efficiency (ZUE). Utilization efficiencies of the two nutrients diminished as their rate of fertilization increased, in both the crops. The AE of applied nutrients, in basmati rice varied from 31.4 to 49.7 kg grain kg -1 P and from 43.2 to 121 kg grain kg -1 Zn. In wheat, AE for P varied from 26.9 to 65.5 kg grain kg -1 and for Zn from 56.4 to 83 kg grain kg -1 . In conclusion, the utilization and agronomic efficiency of P in basmati rice can be increased by using 40 kg P 2 O 5 and 2.5 kg Zn ha -1 . Key words: Agronomic efficiency, Basmati rice-wheat rotation, Indo-Gangetic plain, P×Zn interaction, utilization efficiency. INTRODUCTION Rice (Oryza sativa L.)-wheat (Triticum aestivum L.) rotations are one of the predominant agricultural production systems in the world, occupying 13.5 million hectares of cultivated land in the Indo-Gangetic Plains (IGP) in South Asia (Ladha et al. 2009). This rotation constitutes a popular and profitable cropping system for the farmers in India. Rice- wheat systems, as a result of several decades of continuous cropping and the contrasting edaphic requirements for these two cereals, have shown evidence of soil nutrient depletion and imbalances, low nutrient use efficiency, a general reduction in soil organic matter, and stagnating yields (Malewar, 2005; Singh et al. 2013). The most common soil- nutrient deficiencies are those of micronutrients such as zinc (Zn), boron (B) and iron (Fe), even with adequate application of NPK fertilizers under regular adoption of rice-wheat cropping system. In rice–wheat systems, soils cycle between anaerobic conditions during rice cropping and aerobic conditions during wheat cropping. The anaerobic–aerobic cycles in a soil result in differential availability of P and Zn for rice and wheat (Singh et al. 2000). The capacity of soil to supply plant available nutrients can vary greatly among fields and seasons in rice–wheat systems, leading to inefficient use of added nutrients when uniform fertilizer rates are used (Dobermann et al . 2004). The application of phosphatic fertilizers is generally recommended to obtain the optimum returns, but only about 15-20% of the applied phosphatic fertilizer is utilized by the crops and significant amount of P is lost from soil through surface run off and erosion resulting eutrophication of water bodies (Swarup, 2010). Phosphorus (P) and zinc (Zn) interaction is an important phenomenon as deficiencies of both the nutrients are widespread in Indian soils particularly in intensively cropped areas (Jain and Dahama, 2007). High P availability may depress Zn concentrations in plant tissue, may increase physiological requirements for Zn (Cakmak and Marshner, 1987; Aref, 2012), or may result in accumulation of toxic levels of P in these leaves when Zn levels are low (Loneragan et al. 1982). P and Zn interaction is also important globally because of increasing concern over the effects of low levels of micronutrients, especially Zn, in human food (Akhtar et al. 2010). Many greenhouse and field experiments have indicated that within the normal rates of their application, the interaction between P and Zn was synergistic and optimum yields were obtained. Therefore, it is of paramount importance to know the balanced P and Zn fertilization for better utilization efficiency of these nutrients and optimum yield. The hypothesis set for our experiment was that the