Effect of Zeolite and Nitrogen Sources on Nitrogen Leaching from a Calcareous Soil under Ocimum basilicum Planting and Greenhouse Conditions

The effect of zeolite as a soil conditioner that is used for improving physico-chemical soil properties, improving nitrogen use efficiency, and decreasing nitrogen losses has not been studied on leaching of nitrogen from different sources. Therefore, this study was conducted as a factorial greenhouse experiment using a completely randomized design with 3 replications. The objective was to evaluate the effect of 4 levels of zeolite (0, 15, 30 and 45 g zeolite kg-1 soil) on leaching of nitrogen from different nitrogen fertilizers (control and application of 150 mg N kg-1 soil from urea, ammonium sulfate and nano- N- fertilizer) in a calcareous soil under Ocimum basilicum (var. Green Ardestani) planting. At 4 stages, the leachate of experimental pots was collected and nitrate concentration was determined. After harvesting, ammonium, nitrate, and total nitrogen concentrations of postharvest soils were also determined. Application of 15, 30 and 45 g zeolite kg-1 soil increased ammonium concentration of soil by 16%, 13%, and 22 %, and nitrate concentration by 50%, 130%, and 170 % as compared to control, respectively. Application of 30 and 45 g zeolite kg-1 soil increased total nitrogen concentration by 42% and 28 %, respectively. Among the applied levels of zeolite, only application of 45 g zeolite kg-1 soil significantly decreased nitrate concentration in leachates at different stages. The amount of ammonium, nitrate, and total nitrogen were the highest for soils that received nano-N- fertilizer. Furthermore, nitrate concentration in leachate at different stages was the least when soils received nano-N- fertilizer. In general, zeolite increased nitrogen retention from the studied fertilizers and resulted in lower nitrate leaching through soils. Among the studied treatments, application of 45 g zeolite kg-1 soil and using nano- N- fertilizer were the most effective in nitrogen retention and decreasing nitrogen in leachate. Therefore, it is recommended that these treatments be used in field conditions if complementary field trials confirm the results of this greenhouse experiment.