عنوان مقاله [English]
Soil quality is one aspect of sustainable agroecosystem management. The application of zeolite minerals alone or in combination with other soil amendments (organic and inorganic fertilizers) can, directly or indirectly, affect soil quality indicators. Considering the unique characteristics of zeolites, such as the low-cost and abundance of its mines in Iran and the large area of wheat cultivation in Kurdistan province, the need to study the effect of zeolite application on soil properties and wheat yield becomes apparent. Although there is a lot of research on the impact of zeolite on improving soil properties and increasing the yield of various crops, few studies have been done on its residual effects. Therefore, in this study, we investigated the effect of zeolite and nitrogen (N) application on some basic soil properties, N efficiency, and wheat yield under field conditions after two years of zeolite application.
Materials and Methods
Before conducting the research, a composite soil sample from the soil surface (0 to 30 cm depth) was collected and analyzed to assess the farm's soil properties. The experiment was laid out in a split-plot based on a randomized complete block design with three replications at the University of Kurdistan research farm in Dehgolan. The main plots consisted of natural zeolite at four levels (0, 5, 10, and 15 ton. ha-1). Within each main plot, subplots were subjected to nitrogen applications at five levels (0, 50, 100, 150, and 200 kg. ha-1). Urea fertilizer was used to supply the required nitrogen. Zeolite was only utilized in 2018 and mixed into the surface layer of soil. The experiment was repeated in 2019 except for no addition of zeolite. The field was under potato cultivation in the first year of the experiment and followed by wheat crop in the second year. Wheat cultivation (Pishgam cultivar) was done in 2019 by grain seeders in plots with dimensions of 4.5 × 8.25 m. At the end of cultivation season, harvest was done from each plot, and some plant traits (grain protein, thousand-grain weight, spike number, grain number in spike, an economic yield of the plant, biological yield of plant, harvest index, and chlorophyll concentration) were measured. In order to investigate the effect of zeolite on basic soil properties, soil samples were collected from plots in the second year after harvest, and a number of physical and chemical properties of the soil were measured (dry bulk density (ρb), particle density (ρp), total porosity (f), saturated hydraulic conductivity (Ks), electrical conductivity (EC), soil reaction (pH), cation exchange capacity (CEC), and total soil nitrogen (TN)). Statistical analysis of data was performed using SAS 8.02 software.
Results and Discussion
The results from the second year indicated that the applications of zeolite or nitrogen alone or in combination with each other decreased dry bulk density and particle density of soil, but increased total porosity, saturated hydraulic conductivity, electrical conductivity, soil reaction, and cation exchange capacity. The porous structure of zeolite helps improve soil structure and increase porosity, thereby reducing the bulk density of the soil. Also, zeolites can affect the soil hydraulic conductivity due to channels in their structure. Zeolite is not acidic but marginally alkaline, and its use with fertilizers can help buffer soil pH levels. The very open structure of the zeolite and the similar pore network create a high specific surface area for the storage and exchange of nutrients. Therefore, different salts can be absorbed or desorbed from the zeolite structure. Desorption of salts from the zeolite can increase EC in the soil. The high cation exchange capacity and porosity of zeolite increase soil CEC, which increases the soil's ability to retain nutrients such as ammonium. The results also revealed that the grain protein, thousand-grain weight, spike number, grain number in spike, an economic yield of the plant, biological yield of plant and harvest index, with mean increasing about 37%, 6%, 30%, 15%, 43%, 26% and 7%, respectively, compared with the control, were significantly affected by zeolite and nitrogen applications, and also zeolite and nitrogen interaction. However, the chlorophyll concentration was not meaningfully influenced by them. Increased grain yield can be attributed to reduced nitrogen leaching and increased soil water holding capacity in the presence of zeolite, which improves nitrogen status and the availability of water for growth. Drought stress significantly affects grain yield, harvest index, thousand-grain weight, spike number, grain number in spike, and plant height. The use of zeolite can maintain soil moisture for a longer period and mitigate the adverse effects of drought stress on the crops.
The improved agronomic traits and enhanced grain yield potentials induced by zeolite amendment were related to decreased drought stress in wheat crops and the increase in soil quality indicators and N uptake. The zeolite application probably enhanced NH4+–N retention in the topsoil and prevented NO3-–N from leaching into the subsoil. In general, the results showed that the combined application of zeolite and N can be a beneficial approach for increasing nitrogen fertilizer efficiency and improving the sustainability of agricultural systems.