Estimating nitrogen leaching losses after compost application in furrow irrigated soils of Pakistan using HYDRUS-2D software

Furrow irrigation used in arid areas for maize production is a major cause of groundwater pollution by nitrates, and development of new technologies aimed at reducing pollution is critical for sustainable crop production and water usage. Field experiments and modeling of nitrogen (N) transport were carried out to estimate N losses from compost amended soils under furrow irrigation used for maize production in Pakistan. Press-mud (PrM) and poultry manure (PM) composts were applied at 5 application rates followed by 8 irrigations at rates of 7.5 cm. Changes in inorganic N storage (NH4N and NO3N) were measured in the top 15-cm soil layer. The HYDRUS-2D model was calibrated and validated on measured data and implemented to estimate N leaching losses from soil profile. A four-pools approach used in the simulations considered transformation and transport of the following pools of N: 'Slow soil N', 'Fast soil N', ammonium-N, and nitrate-N pools. Results showed that N leaching losses were higher for: (i) PrM compost due to its higher mineralization rate; (ii) wet year due to washing out of N accumulated in ridges; and (iii) 1:1 ridge to furrow aspect ratio in comparison to the 2:1 ratio, due to an increase in N accumulation in wider ridges. Overall, the HYDRUS-2D software appeared to be a useful tool for predicting inorganic N losses in manure amended soil under furrow irrigation.