Directly applied Chilembwe phosphate rock for enhanced leaf phosphorus concentration in Tithonia diversifolia
Low availability of soil phosphorus (P) limits crop production in many areas of Zambia. The use of Chilembwe phosphate rock (CPR) from Zambia for direct application has not been successful on annual crops due its low solubility. The modification technique studied was a biological method to transform inorganic P from CPR into plant biomass of 'Tithonia diversifolia.' 'T. diversifolia' was grown in acidic soil treated with finely-ground CPR at rates of 0, 20, 40, 60 and 80 kg P ha-1. Applications of 40 kg P ha-1 or higher CPR significantly increased leaf P concentration after 16 weeks compared to the control. Application of CPR can enhance leaf P concentration and improve biomass quality of ' T. diversifolia.' 'T. diversifolia' was also grown under 'Faidherbia albida' treated with finely-ground CPR. Leaf P concentration was significantly higher under the 'F. albida' canopy compared to the open field after 8 weeks. Biomass from 'T. diversifolia' was used to prepare a leaf extract and evaluate its effects on biomass production of ' Arachis hypogeae.' Application of 750 liters ha-1 leaf extract did not significantly affect biomass production in 'A. hypogeae ' after 12 weeks, compared to the control, or application of 40 kg P ha-1 CPR.