The Effects of Humic Acid Application on Yield and Yield Components of Wheat and Some Chemical Properties of a Saline-Sodic Soil

  One of the most important reasons for the decrease of yield in salt affected soils is ion toxicity, poor chemical and physical properties of soils, can have profound effects on crop ecosystems. In order to increase the plant production in saline soils, considering salinity and weather conditions, methods such as soil leaching, compatible plant cultivation, the use of suitable cultivars, agronomy operations, and the use of plant growth regulating agents have been proposed. The aim of this study was to investigate the effect of humic acid compounds application on plant growth and yield and chemical characteristics of a saline-sodic soil. In order to study the effect of humic acid on soil chemical characteristics, wheat growth and yield of Arg cultivar, an experiment was conducted in a randomized complete block design with 4 replications. a split split plot experiment carried out as a randomized complete block design with 4 replicates in which there were 2 levels of irrigation salinity (2 and 10 dS/m) as the main plots, 4 levels of Humaster Food application in different stages of growth (without application, application in March or April and in both months) as the sub plots and also application of Pars Humic in 3 levels (0, 75 and 150 Kg/ha) randomly in every sub plot. Before planting and after harvesting, soil samples were taken from the soil and the amount of sodium ions, the sum of calcium and magnesium, electrical conductivity of saturated extract, sodium ratio, pH, and organic matter percentage were measured. At the end of the plant growth period, height, shoot yield, grain number per spike, 1000 seed weight and grain yield were measured and harvest index was calculated. The analysis of variance of the data obtained from the experiment showed that the interaction between Humasterfood and Pars Humic and the interaction effects of salinity, Humasterfood and Pars Humic on shoot dry weight were significant at P< 0.05. The effect of treatments on soil specific properties also showed that the interactions between salinity levels and Humasterfood and Pars Humic on sodium adsorption ratio (SAR) was significant at P< 0.01. Means comparison showed that the application of Humasterfood in March and April, decreased the concentration of sodium and calcium + magnesium, and SAR as amount as 37.3, 30.1, and 28.4 %, respectively. Also, this fertilizer increased the shoot dry weight as 8.5 % compared to control. The ability of humic acid in humic acid containing fertilizers to modify the concentration of single and bivalent soil cations and changes in SAR, permeability and, finally, increased soil leaching are desirable and suggested their application in areas where soils are to be drainage constraints due to high SAR