Impact of plant populations and nitrogen levels on maize.

To study the impact of plant population and nitrogen levels on maize, an experiment was conducted at KPK Agricultural University, Peshawar, Pakistan during summer 2006.The experiment was carried out in randomized complete block (RCB) design with split plot arrangement having four replications. Plant populations (4, 6 and 8 plants m -2 ) were kept in the main plots while nitrogen levels (0, 100, 130 and 160 kg ha -1 ) were allotted to the subplots. The size of each subplot was 3 m × 5 m (15m 2 ) with row to row distance of 75cm. Azam variety was sown at the seed rate of 40 kg ha -1 . The required plant population i.e., 4, 6 and 8 plants m -2 were maintained by thinning after emergence. Ears m -2 , grain yield and biological yield consistently increased with increase in plant density from 4 to 8 plants m -2 . However, grains ear -1 and thousand grain weight lessened with increase in plant density. Harvest index declined with increase in plant density but harvest index of plant densities of 4 and 6 plants m -2 was statistically at par with each other. Ears m -2 , grains ear -1 , thousand grain weight, grain yield, biological yield and harvest index constantly improved with increasing level of N. Likewise, ears m -2 , grains ear -1 , thousand grain weight, grain yield, biological yield and harvest index were higher at the highest level of N. The plant density × nitrogen interactions for ears m -2 , grains ear -1 and grain yield were significant. Ears m -2 , grains ear -1 and grain yield continually enhanced with increase in N level from 0 to 160 kg ha -1 at all plant densities. It was concluded that the highest plant population of 8 plants m -2 and the highest N level of 160 kg ha -1 resulted in higher yield of maize.