Low-molecular-weight organic acids as a phosphorus nutrient amendment for Solanum melongena production in calcareous soils of the Central Texas Region
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Phosphorus (P) is a vital component for crop production systems and a non-renewable fertilizer resource. Although P applications to farms has been considered a root cause of increased global yields, it has come at the expense of increased phosphate rock (PR) depletion, the main derivative of P fertilizers which is estimated to decline by 2050. On the other hand, soils frequently contain enough native P for production yet it is unavailable due to P fixation. Low-molecular-weight organic acids (LMWOA) are largely responsible for mineralizing P in the soil rhizosphere and making it plant available in soil solution. This study investigated the potential of two LMWOAs, oxalic and citric acid, to mineralize fixed P in bulk soils and the effects on production of eggplant. Two calcareous soils were used, including an alkaline (pH 7.6-7.8) vertisol from the Houston Black series and a slightly acidic (pH 6.5-6.8) mollisol from the Tarpley soil series. Results showed oxalic and citric acid in the high pH calcareous soil mineralized P in amounts equivalent to applied triple superphosphate (TSP) fertilizer (p > 0.05) while eggplant yields indicated no significant difference (p > 0.05) between LMWOA applications and TSP fertilizer. In the low pH calcareous soil, LMWOA treatments were significantly less effective at mineralizing native soil P and matching eggplant yield (p < 0.05) when compared to TSP fertilizer applications.