Influence of Organic Acids on Nutrients Availability from Natural Alternative Fertilizers

         A FIELD experiment was carried out during the summer  ………season with sesame and the winter season with wheat crops in a sandy soil at the Ismailia Agric. Res. Station. The work aimed to study the role of organic acids in nutrients availability and productivity of both indicated crops. Urea- formaldehyde, rock phosphate, feldspar and acidulation with different organic acids ((humic, fulvic, tartaric, salicylic and oxalic) and mineral acid sulphuric) at two concentrations 10 and 15% (C1) and (C2) were used. Results revealed that acidulation had positive effect on chemical properties as well as availability of soil N, P and K nutrients compared to the control treatments; soil pH  decreased especially with C2 which relatively raised soil EC. Also, there was a significant increase in the availability of N, P and K in soil; again, the superiority was with the second concentration. There was a significant response to acidulation compared to the control treatment when assessing yield of each grains or seeds and straw of both wheat and sesame crops, especially when using the second concentration (C2). An increase in the total content of NPK elements with acidulation treatments compared to the control for both wheat and sesame crops was observed. The results also showed high response to salicylic acid compared to other acids while the oxalic acid being inferior. Finally, urea- form, rock phosphate and feldspar (alternative fertilizer) under acidulation with different acids could be a promising approach to enhance release of available N, P and K and to improve soil chemical properties which will be reflected on the yield along with total content of nutrients.