Evaluate the Effect of Some Factors Affecting Solubilization of Phosphorus in Rhizosphere

Abstract

The aim of this work was to conduct pot experiment to study the ability of plant roots on solubilizing various sources of phosphorus and factors that may facilitate or inhibit their activity. A split medium split root technique experiment was conducted to study the effect of CaCO3, pH, organic matter (humic acid) and bentonite on the pH, P solubility in the medium and P concentration in bean plants (Vicia faba var. balady). The changes in pH of the lower solution was recorded, also the root exudate was collected in 500 ml of CaCl2 solution 0.5 × 10-4 M and pH 6.85. Results showed that the highest recorded total dry weight was found when both N forms were applied in the ratio of 1:4 NO-3: NH + 4 or NO-3 alone. The mechanism of solubilizing rock phosphate by exudating protons or organic, amino and other organic compounds is possible at the root surface even in alkaline soil as long as the rock phosphate material was added near the root and organic matter was added to limit the fixing power of the inorganic components as CaCO3 and excess soluble Ca. Also, the availability of P from rock phosphate sources depends on its reactivity value.

The possible use of scarce soluble materials as a source of phosphorus in Vicia faba L. grown in calcareous soils

“…Also, the same results were found when humic acid was added, but for OSP the P solubility increased more than the double. These results agreed with those obtained by Elhag et al (2019) concerning the effect of humic acid on increasing P availability in washed sand. On the other hand, the effect of these natural organic sources was different when the dissolving bacteria was added, as the values of P solubility increased with compost or humic acid in these sources with more P solubility for OSP than for RP or BS.…”

“…This was found in case of without adding or with adding solubilizing bacteria, but the values were generally higher with the later. Elhag et al (2019) reported that, increasing available P in soil by addition of P sources was reflected on increasing P concentration in bean roots and shoots, with high concentrations in shoots more than roots.…”

“…Many factors affect the solubility of P in soil and its availability to growing plants, particularly under P-stressed conditions: with using rock phosphate or other untraditional components as a source of P; such as acidifying the root medium (Houassine, 2020) and adding organic acids, amino acids and other chelating substances (Grover, 2003;Taskin et al, 2019;Elhag et al, 2019). Accordingly, getting benefit of factors that help in increasing solubility and availability of P from insoluble sources may encourage the use of rock phosphate (RP) or recycling untraditional sources i.e., basic slag (BS), even under alkaline conditions, with preserving the environment from contamination.…”

“…Humic acid (HA) is a common fertilizer containing most elements that improve soil fertility and increase nutrients availability, thus enhances plant growth, and yield as well as decreases the harmful effect of stresses (Doran et al, 2003). The effect of HA on the availability of P and micronutrients in calcareous soils have been given especial attention because of observed increases in uptake rates of these nutrients following application of HA (Satisha & Devarajan, 2005;Elhag et al, 2019). Also, compost is seen to be beneficial in improving soil fertility and crop productivity (Adugna, 2016), remediating polluted environment, recycling agricultural wastes (Taiwo, 2011), reducing the phytotoxicity of heavy metals (Huang et al, 2016), increasing water use efficiency (Adugna, 2016), and microbial activity (Huang et al, 2016;Lee et al, 2019).…”