Effect of Different Levels of Humic Acids on the Nutrient Content, Plant Growth, and Soil Properties under Conditions of Salinity

In this study, the effects were investigated of salinity, foliar and soil applications of humic substances on the growth and mineral nutrients uptake of Corn (Hagein, Fardy10), and the comparison was carried out of the soil and foliar applications of humic acid treatments at different NaCl levels. Soil organic contents are one of the most important parts that they directly affect the soil fertility and textures with their complex and heterogenous structures although they occupy a minor percentage of the soil weight. Humic acids are an important soil component that can improve nutrient availability and impact on other important chemical, biological, and physical properties of soils. The effects of foliar and soil applications of humic substances on the plant growth and some nutrient elements uptake of Corn (Hagein, Fardy10) grown at various salt concentrations were examined. Sodium chloride was added to the soil to obtain 20 and 60mM saline conditions. Solid humus was applied to the soil one month before planting and liquid humic acids were sprayed on the leaves twice on 20th and 40th day after seedling emergence. The application doses of solid humus were 0, 2 and 4 g/kg and those of liquid humic acids were 0, 0.1 and 0.2%. Salinity negatively affected the growth of corn; it also decreased the dry weight and the uptake of nutrient elements except for Na and Mn. Soil application of humus increased the N uptake of corn while foliar application of humic acids increased the uptake of P, K, Mg,Na,Cu and Zn. Although the effect of interaction between salt and soil humus application was found statistically significant, the interaction effect between salt and foliar humic acids treatment was not found significant. Under salt stress, the first doses of both soil and foliar application of humic substances increased the uptake of nutrients. Keyword: humic acids; nutrient content; plant growth; salinity, soil properties In recent years, many advances have been achieved towards improvement on the quality and quantity in agriculture. The advances and development in agriculture depend not only on mechanisation and new hybrid seeds but also on the improvement on the soil properties which also help to increase the crop productivity. Unsuitable soil conditions for the plant development generally arise from the lack of organic contents in the soil. To solve this problem, humic substances have started to be given to the soil in Egypt and in other parts of the world as well to improve the crop yield. For example, humic and fulvic acids preparations have been commonly used in many greenhouses. Majority of them are produced domestically although some of them are imported. The effect of organic matter on the soil properties such as physical, chemical, and biological ones has been well known for a long time. The organic matter content of soil in Turkey is generally low (Eyupoglu 1998). Soil organic matter contains residues of plants and animals and primary and high polymer organic compounds formed by their decomposition. Soil organic matter has not certain chemical formula due to its dynamic structure.Soil organic matter mainly consists of humic and fulvic acids which are called humin materials (Schnitzer 1982; Andriesse 1988). They are