Production of Oxalic Acid as Influenced by the Application of Organic Residue and Its Effect on Phosphorus Uptake by Wheat (Triticum aestivum L.) in an Inceptisol of North India

Phosphorus has been recognized as an important element in plant nutrition [ 1 ]. Considerable research has been done towards defining its chemistry in the soil system. Soils are known to vary widely in their capacity to supply phosphorus to crops, as only a small fraction of it in soil is in available form to crops [ 2 ]. In addition to this, phosphorus occurs in very low concentration in soil solution. Its uptake results in a further decrease of its concentration in the soil solution near plant roots [ 3 ]. As a result, phosphorus deficiency has become a limiting factor in crop production [ 4 ] in agricultural soils worldwide [ 5 ]. Phosphatic fertilizers are costly and their efficiency is very low (15–20 %). A major portion of added phosphatic fertilizer is either chemically fixed by Ca, Al, Fe and Mg or strongly adsorbed on some soil components. Huge amount of organic residues i.e. press mud and bagasse are produced from sugar industries. Their disposal has become a serious problem. Use of press mud and bagasse and crop residue like rice straw, may be useful to overcome the low efficiency of phosphorus. It has been reported that decomposition of sugar rich substance bagasse and press mud release organic acids and play an important role in the mobilization of soil phosphorus [ 6 ]. Plant root activity particularly in rhizosphere has been reported to dissolve unavailable form of P and thereby increase the availability of P to plant. Exudation of organic acids from roots is considered to be one of the mechanisms for plants to adapt to P-deficiency [ 7 , 8 ]. The present study deals with the release of oxalic acid from press mud and bagasse and its effect on phosphorus uptake by different wheat cultivars.