Productivity and Profitability of Pop Corn, Composite and Hybrid Maize ( Zea mays L.) Under Low Nitrogen Stress in Mollisols of Uttarakhand

A field experiment was conducted during kharif 2006 and 2007 at G

The nutritional requirement varies with kind of corn types like composite, hybrid, pop corn and so on; therefore, their nutritional requirements vary. But local faming communities of Tarai and hills usually apply flat dose of nitrogen i.e. 100-120:60:40 N:P2O5:K2O kg/ha irrespective of corn types, that not only reduces nitrogen use efficiency but also increases cost of cultivation (Kumar, 2009). It has also been observed that composites and pop corn require lower nutrition including nitrogen because of short duration of the crop. Hence, there is an urgent need to find out corn types and varieties suitable under low nitrogen conditions. Therefore, the field experiment was carried out to study the effect of nitrogen stress on productivity and profitability of pop, composite and hybrid corns in Mollisols of Uttarakhand.

Materials and Methods
Field experiments were conducted during kharif 2006 and 2007 at G. B. Pant University of Agriculture and Technology, Pantnagar. The soil was sandy loam in texture, neutral in reaction (pH 7.3), medium in organic carbon (0.57 %), low in available nitrogen (223.6 kg ha -1 ), medium in available phosphorus (19.9 kg ha -1 ) and potassium (147.8 kg ha -1 ). The experiment consisted of three nitrogen levels viz., 40, 60 and 80 kg ha -1 and four varieties namely 'VL Amber' (pop corn), 'Him-129' (hybrid), 'Vivek-11' (composite) and 'Pragati' (composite) fitted in split plot design keeping nitrogen levels in main plot and varieties in sub plot, and replicated thrice. The crop was raised as per recommended package and practices. The crop was sown on 25 th July and 25 th June in 2006 and 2007 and harvested on 31 st October 2006 and 21 st Sept 2007, respectively with 15 kg ha -1 seed rate in case of VL Amber (popcorn), 25 kg ha -1 'Him-129' (hybrid) and 20 kg/ha . The crop geometry was 60 cm x 25 cm during both years. One third of N and full P2O5 (60 kg/ha) and K2O (40 kg/ha) were applied as basal and remaining N was top dressed in two equal splits first at knee high and second at tasseling stage. Sources of nitrogen, phosphorus and potassium were urea, SSP and MOP, respectively. Pre-emergence application of Atrazine @ 1.0 kg a.i. ha -1 was done just after sowing for effective weed control. The samples of randomly selected five plants were taken from every plot for analysis of growth and yield parameters. Total rainfall during crop season in the years 2006 and 2007 was 682.2 and 1158.6 mm with number of rainy days 33 and 43, respectively. High rainfall during the year 2007 caused water logging and resulted in poor yield despite timely sowing. Cost of cultivation was calculated by taking current market *Corresponding author email: bhatnagaramit75@gmail.com prices of inputs while gross return was obtained by multiplying grain yield with market price. The B:C ratio was calculated by dividing the gross return by cost of cultivation.

Growth parameters
Plant growth suffered badly under low levels of nitrogen as evidenced with lower dry matter production and leaf area during both years. The highest plant dry matter as well as leaf area was recorded with 80 kg nitrogen at all growth stages (Table1). Poor plant growth at 40 kg nitrogen might be due to less availability of nitrogen which decreased vegetative growth and dry matter production. Adequate supply of nitrogen might have helped the maize plants to grow faster, which in turn put forth more photosynthetic surface and leaf area, thus contributing more dry matter with 80 kg nitrogen. Bangarwa et al. (1988) and Brar et al. (1989) also reported that increased level of nitrogen favored the plant growth and development. Different corn varieties i.e. hybrid, composite and pop corn exhibited differential pattern of growth. 'VL Amber' (pop corn) had faster growth at early stage and produced significantly higher dry matter and leaf area at 30 days after sowing (DAS) but with age advancement, its growth slowed down and exhibited significantly the least dry matter at 60 DAS and harvest. Initial growth of 'Him-129' (hybrid) was slow but it improved with age and produced significantly higher dry matter and leaf area at harvest but was statistically similar to 'Vivek-11'.The genetic constitution of variety might be responsible for differential growth behavior. Ammaji and Surayanarayana (2000) also reported variations in growth of maize cultivars. Plant population is an important parameter for yield in corn as it does not share the trait of tillering and branching. Nitrogen levels did not affect total days required for 50 per cent tasseling and silking during both years indicating no effect of low dose of nitrogen on corn phenology. Owing to same maturity period, varieties did not vary significantly with respect to number of days required for 50 per cent tasseling and silking.

Yield parameters
Significantly higher cob length was recorded at 80 kg nitrogen during both the years (15.4cm) and that was also statistically on par with 60 kg nitrogen. The lowest level of nitrogen (40 kg) produced significantly the lowest cob length. The cob girth did not vary statistically among nitrogen levels though the highest value was obtained at 80 kg nitrogen during both the years (Table 2). More supply of nitrogen might have helped in increasing the cob length by favoring the metabolic activity probably cell division and elongation. Singh (2003) was of similar opinion.'VL Amber' exhibited significantly the lower cob girth (12.3 and 9.7 cm, respectively), while 'Him-129', 'Vivek-11' and 'Pragati' had similar cob girth 261 during both the years. However, variations in cob length were non significant.

Table 2. Flowering, cob characters and plant population of corn as influenced by nitrogen levels and varieties
Crop fertilized with 80 kg nitrogen being at par with 60 kg nitrogen exhibited significantly more 100-grain weight than 40 kg during both the years. Significantly higher grain weight per cob was recorded at 80 kg nitrogen and the lowest at 40 kg that remained statistically similar to 60 kg N. The higher value of 100-grain weight and grain weight per cob at 80 kg N may be attributed to better plant growth consequently better partitioning and translocation of sugars. Sen et al. (1999) also observed similar results. 'Him-129' being at par with 'Vivek-11' produced significantly more 100grain weight than 'VL Amber' and Pragati during both the years. Grain weight per cob was significantly lower in hybrid 'Him-129' and pop corn 'VL Amber' during both the years, respectively.

Grain Yield
The grain yield of corn was significantly higher at 80 kg N that had 12.5 and 41.4 and 2.9 and 31.9 per cent more than 60 and 40 kg N during 2006 and 2007, respectively (Table 3). Mishra et al. (1994) and Tyagi et al. (1998) also observed significant improvement in yield attributes with increasing nitrogen levels. The higher yield was due to more value of yield attributes viz., cob length, cob girth, 100-grain weight and grain weight per cob (Shivay and Singh, 2000). However, variations in grain yield between two years may be attributed to weather conditions prevalent during crop season particularly rainfall that caused water logging in 2007 and had severe adverse effect on corn yield. Nitrogen levels Hybrid 'Him-129' produced significantly higher grain yield and that was 16.2, 31.2 and 37.7 per cent more in 2006 and 16.6, 20.8 and 65.0 per cent more in 2007 than 'Vivek-11', 'Pragati' and 'VL Amber', respectively (Table 3). Being a hybrid, 'Him-129' showed inherent high genetic production potential and produced more yield than pop corn and composites. The lower yield of pop corn 'VL Amber' was due to lower value of yield attributes viz; cob girth, 100-grain weight and grain weight per cob. Shanti et al. (1997) also observed superiority of hybrids over composites. Harvest index recorded was significantly higher in 'Him-129' and the lowest in 'VL Amber'. The superiority of the hybrid could also be due to its inherent efficient sink mechanism. Significant hybrid effect for grain yield was also reported by Farnham (2001).

Economics
Application of higher nitrogen dose of 80 kg not only had higher cost of cultivation but also gave higher gross returns, net returns and B:C ratio during both years mainly because of higher grain yield (Table 4). Owing to maximum grain yield, Hybrid 'Him-129' gave the highest gross, net returns and B:C ratio in spite of higher cost of cultivation. These findings are in conformity with Kumar (2009).