Productivity, quality and water expense efficiency of late kharif sown hybrid maize (Zea mays L.) under different irrigation regimes and nitrogen levels.

In the Indo-Gangetic plains of India, the continuous adoption of rice-wheat cropping system has led to a number of adverse effects including deterioration of soil health, severe ground water depletion and emergence of pest and weed infestation. The above factors have led to the need for replacing high water demanding rice with comparatively low water requiring maize crop (Jalota and Arora, 2002). In Punjab, late sown kharif maize (August sowing) has significantly lower maize borer infestation (Anon., 2012), higher grain and stover yields, net return and benefit: cost ratio compared to normal sowing in June and July (Panchanathan et al., 1992). In August sowing, as the crop progresses after kneehigh stage, the temperature goes on falling causing a reduction in evapo-transpiration rate, so there is a possibility of less irrigation water requirement as compared to maize sown in other seasons. The performance of a plant in terms of its growth and yield mainly depends on plant water status which can be maintained at optimum level by following a proper irrigation schedule. Most of the work on irrigation is based on critical stages or soil moisture depletion without incorporating climatic parameters. IW/CPE ratio has been found to be a reliable, economical and practical basis for scheduling irrigation (Prihar et al., 1976). Again, nitrogen is the most limiting factor of all the essential plant nutrients in Punjab soils owing to their low organic carbon content (Benbi and Brar, 2008). Not only the grain yield of maize but the quality of grains is also affected to a great extent by nitrogen availability. It has been reported that maize grown under limited water supply requires less nitrogen to achieve maximum grain yield than that required with well water supply (Moser et al., 2006) and increase in nitrogen supply could improve yield and irrigation water use efficiency (Mansouri et al., 2010). No concrete information is available on irrigation and nitrogen requirements of late sown kharif maize. Keeping this in view, a field experiment was carried out to evaluate the performance of late sown kharif hybrid maize under different irrigation and nitrogen levels. The field experiment was conducted at Students’ Research Farm, Department of Agronomy, Punjab Agricultural University, Ludhiana (30 o 54′N latitude and 75 o 48′E longitude at an altitude of 247 metre above the mean sea level) during late Kharif of 2009-10. Experimental soil was loamy sand in texture. Moisture content of 0-180 cm soil profile at 0.3 and 15 bar was 44.17 and 10.52 cm, respectively, with available soil water 33.65 cm. The average bulk density of 0-180 cm soil profile was 1.60 g cm -3 . The soil pH, electrical conductivity, organic carbon, available N, P and K were 8.1, 0.21 dS m -1 , 0.15 per cent, 185.6 kg ha -1 , 13.9 kg ha -1 and 154.6 kg ha -1 , respectively in the top 0-15 cm layer. The experimental site has been characterized by subtropical semi-arid climate with average rainfall of 705 mm. The experiment was laid out in split-plot design with four replications and treatments comprised of four irrigation regimes as main plot treatment [IW/CPE ratio 0.50 (I0.50), 0.75 (I0.75), 1.00 (I1.00) and 1.25 (I1.25)] and four nitrogen levels as sub-plot treatments [100(N100) , 125 (N125), 150 (N150) and 175 (N175) kg N ha -1 ]. Nitrogen was applied as per treatments. P2O5, K2O and zinc sulphate were applied @ 60, 30 and 25 kg ha, respectively as recommended in the Punjab state (Anonymous, 2012). Urea, single super phosphate and muriate of potash formed the source for N, P and K, respectively. Entire quantity of P2O5, K2O, zinc sulphateand one third of N was applied at sowing and remaining N was applied in two equal splits i.e. at knee high and pre-tasselling stages. The hybrid maize cultivar ‘PMH1’ was sown on August 25, 2009 after giving a pre-sowing irrigation. The sowing was done by dibbling two seeds per hill keeping row to row spacing of 60 cm and plant to plant spacing of 22 cm. Irrigation was scheduled when the cumulative pan evaporation (CPE) reached the level of 60, 75, 100 and 150 mm in case of I1.25, I1.00, I0.75 and I0.50, respectively. The irrigation water was measured with Parshall flume and depth of irrigation was 7.5 cm. The number of irrigations required during crop growing period was 3, 3, 2 and 1 at 1.2, 1.0, 0.75 and 0.50 IW/CPE, respectively, as given in Table 1. The total rainfall and open pan evaporation during the crop season were 216.4 mm and 364.9 mm, respectively and 73 per cent of the rainfall was received during first four weeks out of total 20 weeks of the crop season.