اثر زئولیت‌های طبیعی و اصلاح‌شده با سورفکتانت بر عملکرد کمی و کیفی گندم در آبیاری با پساب

The use of wastewater for irrigation has become more important due to water shrotage. The wastewater contains nutrients that, if properly managed, increase soil nutrients. Due to the low efficiency of fertilizer consumption, nitrogen fertilizers result in environmental problems such as groundwater pollution and surface contamination with nitrate and ammonium. Nitrogen loss, especially in irrigated lands and sandy soils, significantly leads to an increase in nitrate concentration in surface- and ground-waters. On the other hand, nitrogen is the most important nutrient for wheat, and its optimum consumption management is of utmost important for success in increasing grain and wheat protein production. The increasing demands for environmental protection and sustainable food production causes an increase in the use of natural and non-toxic materials in agriculture. Therefore, the use of soil amendments such as zeolite becomes important. Zeolites are natural, non-toxic and inexpensive materials which due to their unique physical and chemical properties, including specific surface area and high cation exchange, are considered as suitable soil modifier or carrier for plant foods.
The aims of this study were to investigate the influence of size (mm and μm) and usage (20 and 60 grams per kilogram of soil) of natural zeolite of clinoptilolite (Cp) and surfactant-modified zeolite (SMZ) on the soil’s nitrate and ammonium leaching, and on wheat plant performance using soil columns and applying wastewater for irrigation at Greenhouse of Isfahan University of Technology in 2015-2016. The experimental soils were placed in Polyethylene columns with 11 cm inner diameter and 65 cm height. The experiment was factorial with completely randomized design with three replications for each treatment. The treatments under study from factorial were: two types of soil modifier (natural zeolite and surfactant-modified zeolite), soil modifier with two particle sizes (1 to 1.68 mm and 53 to 63 microns), and two modifier consumption levels (20 and 68 g/kg soil). This study evaluates the grain yield, dry weight, root dry weight, root volume, leaf area index, stem height, stem diameter, stem and leaf nitrogen, grain nitrogen, nitrogen harvested by the plant and nitrogen leaching.
According to the results obtained from the current study, the use of Cp and SMZ modifiers had a significant effect on wheat growth, so that the amount of dry matter of the plant, grain yield, root dry weight, root volume, grain nitrogen and nitrogen harvested by the plants in Cp were significantly (P <0.05) higher in comparison with the SMZ treatments (at the level of 1%), so that the grain yield (2.3 and 0.8%) and dry weight (10.84 and 9.8%), root dry weight (6.61 and 5.37%) and root volume (5.68% and 4.8%), increased in Cp and SMZ treatments, respectively. Also, the concentration of the grain nitrogen and nitrogen harvested by the plant in Cp receptor columns were significantly (1.45 and 2.49%, respectively) higher than SMZ receptor columns. These results could be due to the difference in absorption and desorption of the NH₄⁺ and NO3-N of Cp and SMZ during the study period, respectively. Absorption and desorption of NH₄⁺ in Cp are due to the cation exchange and diffusion, while absorption and desorption of NO₃-N in SMZ are because of surface anion exchange. This means that SMZ would probably act slightly weaker than Cp in the timely release of nitrogen needed for the plant growth. However, Cp and SMZ modifiers did not affect the leaf area index, plant height, stem diameter, and stem nitrogen, leaf nitrogen and nitrogen leaching significantly. However, higher modifier application significantly (at 1% level) created better growth conditions for wheat plant than less modifer application, ie, application of Cp and SMZ at 60 g/kg soil was effective on nitrate leaching and growth of the wheat plant. This means that the use of Cp and SMZ as soil modifier significantly reduces the nitrate leaching and, consequently, increases the amount of nitrogen in the first layer of the soil. As a result, with increasing providing nitrogen in the root environment, pollution not only does not decrease, but the yield of the product increases and it helps to improve the growth of the plant. The size of the modifier particles has a significant effect on the nitrate leaching, but was not effective on the  growth of wheat plant. The use of modifiers at the level of 20 g/kg soil was not effective in reducing nitrate leaching and wheat growth. In general, according to the results, the Cp and SMZ modifiers as environmentally friendly materials, are effective in controlling soil nitrogen leaching and improving nitrogen removal efficiency by the plant.