Introduction: The environmental effects caused by the use of chemical fertilizers, including water and soil pollution, are a threat to the health of the environment. Researchers are trying to reduce the harmful effects of using chemical fertilizers and applying as much mineral resources as possible in the soil to meet the nutritional needs of plants. The use of natural amendments such as zeolite, pumice and bentonite play an important role in reducing the loss of nutrients and increasing the fertilizer use efficiency. These amendments, having a special physical and chemical structure, play an important role to increase the absorption of water and nutrients. As a result, this research was conducted with the aim of determining the effect of zeolite, pumice and bentonite application on the seed yield, yield components and concentration of macro elements such as nitrogen, phosphorus and potassium of soybean seeds and leaves in two soils with different characteristics.
Materials and methods: This experiment was conducted as a split plot in three replicates and in 84 pots in the research greenhouse of Sari Agricultural Sciences and Natural Resources University in 2021. In this experiment, the main factors include two types of soil texture (silty clay and sandy loam) and the secondary factors in fourteen levels include the control, PK chemical fertilizer treatment according to the soil test, zeolite, pumice and bentonite, each at 2 levels of 0.5 and 1% without fertilizer, 0.5% zeolite, pumice and bentonite with 75% PK fertilizer, 1% zeolite, pumice and bentonite with 50% PK fertilizer were considered. each of the treatments was mixed with 10 kg of soil to the pots. After applying the treatment, three germinated soybean seeds were planted in each pot. In all stages of growth irrigation, weeding, pest and disease control were done. After harvesting, seed yield, the thousand seed weight, pod number and concentrations of nutritional elements such as nitrogen, phosphorus and potassium were measured in seeds and leaves. The data obtained from the experiment were statistically analyzed using Statistic software. The comparison of the means was also done using the LSD test method at the 5% level.
Results and Discussion: The results showed that the effect of the type of soil on seed yield, the thousand seed weight and concentration of phosphorus in seeds and also on the concentration of nitrogen, phosphorus and potassium in leaves was significant. In addition, the effect of the amendment treatments on all studied traits was significant except leaf potassium. While the interaction effect of soil type (texture) and treatments was significant on seed yield, leaf nitrogen, seed phosphorus and seed potassium. the highest amount of seed yield of 67/02 gram per pot was observed in silty clay soil and in 0/5 % zeolite with 75% PK fertilizer and the lowest amount of seed yield of 43.73 gram per pot was obtained in sandy loam soil and 1 % pumice with 50% PK fertilizer. Also the maximum amount of thousand seed weight and number of pods in per pot were observed in the 1% zeolite treatment and the lowest in the 1% bentonite with 50% fertilizer treatment. Bentonite 1% treatment, increased seed nitrogen by 11% compared to control. The mean comparison results showed that in silty clay soil, the highest percent of leaf nitrogen of as 7.79 percent in 1% zeolite with 50% PK fertilizer was measured and in sandy loam soil, the highest percent of leaf nitrogen of 6.86 percent was measured in 0.5% zeolite with 50% PK fertilizer. the highest percent of seed phosphorus and seed potassium was obtained in silty clay soil and 1% bentonite and sandy loam soil and 0/5 % zeolite with 75% PK fertilizer treatments respectively. The lowest amount of seed phosphorus and potassium were measured in sandy loam soil and 0/5 % pumice treatments.
Conclusion: among the amendments studied in this research, zeolite and bentonite had the greatest effect on the studied traits. The positive effect of different levels of zeolite alone and with PK fertilizer was observed on seed yield, thousand seed weight, number of pods in per pot, leaf nitrogen and seed potassium. The general results of the present research showed that the use of 1% zeolite, improved the growth of the plants and increased the yield components. Also the use of zeolite with PK fertilizer for increasing the seed yield was recommended.