Effects of Coal-Derived Humic Substance on Some Soil Properties and Bread Wheat Yield

In the present study, gyttja and its humic-fulvic concentrate were applied to soil either alone or in combination with a chemical fertilizer in a 2-year replicated field experiment with continuous bread wheat cropping during two seasons between 2005 and 2007 in Cukurova, Adana, Turkey. The changes in soil organic matter (SOM) characteristics and available micronutrient status were monitored by soil samplings performed immediately after the harvest in the 2005 and 2006 cropping seasons. The results showed that single and combined applications of humic substances with different types and doses showed different inclinations on selected soil characteristics in consecutive cropping seasons. The levels of SOM, available phosphorus, and grain yield significantly increased under different humic treatments in the first year of the experiment. However, humic substances added to the soil did not affect selected soil parameters and macro- and micronutrient status in the second year of the experiment.