K. Venkatalakshmi, C. Rajababu and D. Janaki
Abstract
A field experiment was conducted using a randomized block design with three replications. The treatments included rock phosphate alone, rock phosphate combined with single superphosphate, phosphor bacteria, phospho bacteria-inoculated enriched compost, biochar, and a control without phosphorus application. Among the treatments, the application of rock phosphate and biochar in a 75:25 ratio, incubated for 30 days prior to sowing, recorded significantly superior growth parameters, including leaf area index. The rapidly increasing cost of soluble phosphate fertilizers has renewed interest in identifying less expensive and sustainable alternatives to chemical phosphorus (P) fertilizers for enhancing soil fertility and improving phosphorus use efficiency. Several studies have demonstrated that the application of rock phosphate enhances the immediate availability of phosphorus and increases its dissolution rate after incorporation into the soil. Biochar is widely regarded as a low-cost and eco-friendly soil amendment with proven positive effects on soil quality and crop productivity. The results of the experiments showed that pooled analysis indicated that the application of rock phosphate + biochar (75:25) incubated for 30 days before sowing significantly enhanced leaf area, leaf area index, and specific leaf area, performing on par with rock phosphate + enriched compost (50:50). The control recorded the lowest values for the above parameters. Specific leaf weight was highest in the control. Growth analysis revealed that the highest CGR, RGR, and NAR were recorded in the rock phosphate + biochar (75:25) incubated for 30 days before sowing when compared to all other treatments. The highest groundnut yield was recorded in the treatment of rock phosphate + biochar (75:25) incubated for 30 days before sowing compared to the other treatments.