Abstract
Understanding the preference of a crop for forms of nitrogen (N) is important to ensure efficient use of N-sources in agriculture. A study was conducted to assess nutrient uptake and dry matter yield of six vegetable crops under different ratios of ammonium- N (NH4+-N) and nitrate-N (NO3–-N) in growth medium. Seedlings of cabbage, carrot, capsicum, knolkhol, lettuce, and tomato, were supplied with five N-treatments (NH4+-N: NO3–-N in the ratios of 0:100, 25:75, 50:50, 75:25 and 100:0) under controlled environment in sand culture. Six weeks after initiating treatments plants were harvested and dry matter recorded. Plants were analysed for total N, P and K contents. Dry-matter yield, N and K concentrations in shoot-tissues in response to Ntreatments were significantly different (p <0.05) among crops. Tomato and knolkhol showed high dry matter yield and N content when supplied with NO3–-N than NH4+-N. The highest dry matter yield for cabbage was obtained with equal supply of NO3–-N and NH4+-N than supplying either form alone. Dry matter yield and N concentration in shoots of lettuce, capsicum and carrot were not significantly affected (p>0.05) by N-treatment. Supplying NH4+-N alone significantly reduced K concentration in shoot tissues in knolkhol, capsicum and tomato. This study revealed that performance of vegetable crops is affected by the NH4+-N: NO3–-N in the growth medium. This knowledge can be utilized to optimize fertilizer-N usage in vegetable cultivation.