Numerical simulations of the effects furrow surface conditions and fertilizer locations have on plant nitrogen and water use in furrow irrigated systems

Abstract

The HYDRUS model can be used to evaluate the effects of different soil surface treatments at the bottom of the furrow, different initial nitrogen fertilizer locations, and different furrow irrigation rates on deep drainage and solute leaching in furrow irrigated systems. This paper extends our 2012 study, in which we considered only one irrigation cycle and ignored the effects of plants. As a result of considering only one irrigation cycle, a large amount of water was used to change the water storage in the transport domain and only limited deep drainage of water and leaching of fertilizer at the bottom of the domain occurred in most scenarios investigated. To obtain a more realistic and complete picture, we have in this study considered multiple irrigation cycles to reflect actual field practices better and accounted for root water and nitrogen uptake and plant transpiration. As in our previous study, soil surface treatments at the bottom of the furrow include untreated, compacted and an impermeable membrane, and fertilizer is initially placed at one of five different locations in the furrow or the ridge. We have also evaluated (1) the effectiveness of triggering irrigation based on a pre-set soil water pressure head at a specific location in the ridge compared with prescribed irrigation at a regular time interval to supply water and nitrogen, and (2) the effects of plant water and nitrogen uptake on the furrow water balance, infiltration, soil evaporation, deep drainage, transpiration and nitrogen leaching. Our simulations show that deep drainage and nitrogen leaching can be substantially reduced by using an impermeable membrane on the bottom of the furrow and that a substantial additional reduction in leaching can be achieved by triggering irrigation rather than using a fixed time schedule. We also show that the initial location of fertilizer has a substantial effect on nitrogen uptake and leaching.