Effect of Amount of Fertilizer and Calcic, Potasic and Soil Zeolite on Reducing Nitrate Leaching from Soil

Nitrogen is an essential element for plant nutrition. Urea is a common fertilizer that used by farmers due to high nitrogen content in its structure. This fertilizer transforms into nitrate in soil. Nitrate is leached below the rooting zoon of agricultural soil. Nitrate leaching is not only a waste of a great cost, but also causes the pollution of water resources. Methemoglobinemia and cancer are well known issues that caused by nitrate leaching. For this purpose, many methods have been proposed to prevent nitrate leaching but due to high cost and low efficiency are not accepted. Using of zeolites is one of the ways that is considered due to its low cost and ability. Zeolite is a mineral material that found in many regions in Iran. Although effect of zeolite on nitrate leaching reduction was studied by many researchers, but there was no study on common three types of Iranian zeolite.
For this purpose, a study was conducted as factorial layout based on a CRD with 21 treatments and 3 replications (total of 63 pots) at the Agricultural Research Station (with longitude and latitude 59o 21’ E and 32o 78’ N, respectively, and elevation 1941m), University of Birjand during 2013. Treatments consisted of calcic zeolite (Zca), potasic (Zk) and z-mix (Zs) in three levels: 0 (M0), 2 (M2) and 6 (M6) as wt% and three nitrogen levels: zero (F0), 200 (F2) and 400 (F4) (as mg.kg-1 soil). Natural clinoptilolite zeolite (Zca, Zk and Zs) were collected from Semnan province (53o 15’ E, 35o 25’ N) and analyzed for its chemical composition by X-ray diffraction.
Pots after saffron harvesting irrigated (in October) and urea treatment added to irrigation water (Iranian farmers called as Zaeech Ab). For prepared sufficient drain from all pots, due to different effect of type and amount of zeolite on soil water content, based on former experiments, leaching fraction was considered as 20%. Sample drain from each pot were transferred toa lab, immediately, and were measured by spectrophotometer. Data related to nitrate leaching were analyzed by ANOVA and Tukey’s test. In this study, SAS 9.1.3 software and Microsoft Excel 2013 were used.
Results showed that type of zeolite, amount of zeolite, amount of nitrogen fertilizer, type of zeolite with amount of zeolite (interaction effect) had significant effect (P