Effect of organic matter and hydrogel application on nitrate leaching in a turfgrass crop: a simulation study using HYDRUS

The intensive cultivation of turfgrass requires a high quantity of water and fertilizer. The fertilizers can leach and reach groundwater or be transported by run-off to water surface. It is necessary to improve irrigation and fertilization techniques to guarantee water and fertilizer optimal use and avoid contamination. The objectives were to analyze water flow and nitrate transport using the HYDRUS-1D and explore the effect of organic matter and hydrogel on the nitrate leaching. The experimental site was divided into 4 plots, each with an approximate area of 40 m2 and a volume of 10 m3. The substrate is composed of sand, which is superimposed on a gravel layer where drainage pipes are installed to collect the leachates. The plots were constructed with different amendments in order to evaluate their influence on water flow and contaminant transport. The plot 1 contains organic matter (OM) and hydrogel (HG). The plot 2 contains OM. The plot 3 was constructed with only HG and the plot 4 with only sand. The results’ simulation indicated that the plot P1 retained water and, accordingly, retained the nitrate leached (2% of total applied nitrogen). The plot P4 drained a greater volume of water and nitrate leached (12% of total applied nitrogen). The greatest differences between the predicted and observed data occurred after 650 h, which appears to confirm the difficulty of modeling relatively long time periods. During this period, there may be changes in the hydraulic parameters that affect water flow. The simulations of nitrate transport indicated that the model partially represents the observed data. This may be due to aspects not considered in the model, such as moisture retention, piston flow, and preferential flow, which favor the leaching of more or less nitrates. The use of hydrogel appears to be a good option for controlling leaching and, therefore, can be recommended, for example, in intensive crop fields or greenhouse crops.