Simulation of nitrate leaching under different irrigation deficit and nitrogen levels in tomato crop using Hydrus 1-D

Abstract

Tomato is one of the most input demanding crop in terms of water and fertilizer. To fulfill the irrigation water demand, the growers use surface and ground water resources, which are declining day-by-day. Realizing the importance of water, tomato yield was studied under deficit irrigation regimes and different Nitrogen (N) levels during 2015 and 2016 at the research farm of the University of Agriculture Peshawar, Pakistan. A randomized complete block design (RCBD) with factorial arrangement was used for the study. These factors were four irrigation levels i.e. full irrigation (I 0 ), 15% deficit (I 15 ), 30% deficit (I 30 ) and 45% deficit (I 45 ) along with four Nitrogen doses i.e. 100% of recommended dose (120kg) (N 100 ), 85% of recommended dose (N 85 ), 70% of recommended dose (N 70 ) and 55% of recommended dose (N 55 ). Frequency Domain Reflectometry (FDR) was used for soil moisture monitoring. Full irrigation was determined on the basis of MAD 30%. Simulation of nitrate leaching showed that Nitrate leaching was more sensitive to irrigation levels than Nitrogen doses. With the increasing level of irrigation nitration, leaching increased significantly compared to the increasing Nitrogen doses and same pattern was observed with the decreasing irrigation levels and decreasing nitrogen doses. When irrigation levels were increased by 10 and 20% nitrate leaching increased by 38 and 48%. Similarly when Nitrogen levels were increased by 10 and 20% increase in nitrate leaching was about 20 and 35% but when irrigation level were decreased by 10 and 20 % nitrate leaching also decreased by 20 and 48% and when the nitrogen level was decreased to 55% the nitrate leaching also dropped by 70%. Based on the above results, it can be concluded that deficit irrigation with low nitrogen doses can be used to minimize nitrate leaching. HYDRUS-ID can be effectively used for simulating Nitrate leaching.