Effect of Different Nitrogen Doses and Deficit Irrigation on Nitrogen use Efficiency and Growth Parameters of Tomato Crop under Drip Irrigation System

Tomato is one of the most demanding crops in terms of water and fertilizer inputs. To meet irrigation water demand, growers use surface and ground water resources. These resources are in decline. Realizing the importance of water and fertilizer, tomato yield under deficit irrigation regimes, and different Nitrogen (N) levels were studied during 2015 and 2016 at the research farm of the University of Agriculture Peshawar, Pakistan, using factorial arrangement of randomized complete block design (RCBD). These factors were four irrigation levels; full irrigation (I0), 15% deficit (I15), 30% deficit (I30) and 45% deficit (I45); and four nitrogen doses;100% of recommended dose (120 kg ha^-1) (N100), 85% of recommended dose (N85), 70% of recommended dose (N70) and 55% of recommended dose (N55). Io was based on 30% of management allowed deficit. Effect of Nitrogen doses on Nitrogen use efficiency (NUE) was found to be highly significant and showed an increasing trend of 7, 25 and 68% with reducing Nitrogen doses. However, the effect on dry-tofresh weight ratio, plant height, days to 50% flowering, were found to be non-significant. Results indicated that deficit irrigation (I15, I30 and I45) had significant effect (P 0.05) on plant height and NUE. Plant height tends to decrease by 1.3 and 5.5% with deficit irrigation. NUE also decreased by 17, 16 and 24 with deficit irrigation. Compared to I0, while the effect on dry to fresh weight ratio and days to 50% flowering was found to be non-significant.