Effect of Clinoptilolite Zeolite Application on Reducing Urea Leaching from Soil

Nutrients and insecticides in runoff or drainage water from the agricultural lands have of long posed a great challenge to surface and ground water quality. In agricultural production, fertilizers supply the main source of nitrogen required for plant growth. Investigations have shown that part of the nitrogen fertilizers are excluded from the root zone and leached into the groundwater or rivers. Modern technologies employed cultivation, irrigation, and fertigation management s well as changes in the structure of fertilizers and insecticides could have positive effects on reducing the leaching of nitrogen. The objective of this research was to study the effect of clinoptilolite zeolite application on reduing urea leaching from soil. In this greenhouse experiment, four levels of zeolite (0, 5, 10, and 15% added to a silty clay loam soil), one level of leaching (25% of net irrigation depth), one level of fertilizer application (60 mg/L), two sizes of Mianeh zeolite (50 and 200 mesh), and one size of Mashhad zeolite (200 mesh) were used in four irrigation events. The results showed positive effects of zeolite on reducing urea leaching. The nitrogen concentration in the 0% zeolite treatment was reduced from 1337 mg/L (after the first irrigation) to 16 mg/L (after the fourth irrigation event). But, for 15% Mianeh zeolite (50 mesh), these values were 427 and 54 mg/L. Comparison of zeolite types showed that Mashhad zeolite was more effective in adsorbing urea than Mianeh zeolite (both 200 mesh). Zeolite, in addition to reducing the urea potential for groundwater pollution, was able to decrease the rate of solute transport. It was found that zeolite size can have significant effects on the leaching of contaminants. Finer zeolite particles absorb and hold more urea.