Effect of Phosphates on the Growth, Photosynthesis, and P Content of Oil Tea in Acidic Red Soils

Phosphorus (P) is a limiting factor in Camelia oleifera production as P is easily fixed by iron and aluminium oxides in acidic red soils. To better understand sparingly soluble and organic P utilization by oil tea in these soils, the growth and physiological responses of C. oleifera seedlings and P contents in soil and plants were investigated under Al-P, Ca-P, Fe-P, and O-P treatments. Plant growth was increased significantly when Ca-P was added, followed by Al-P and Fe-P. Net photosynthetic rate (Pn) was increased for all P-treated seedlings, and P treatments except for Fe-P also increased SPAD values. Ca-P, Al-P, and Fe-P treatments increased Fv/Fm, Fv'/Fm', yield, and qP (photochemical quenching). Ca-P and Al-P increased available P the most, while Fe-P increased TP the most in both rhizosphere and non-rhizosphere soils. Available P level in rhizosphere soil was significantly higher than that in non-rhizosphere soil. P treatments significantly increased P content in all plant samples. These results demonstrated that Al-P and Ca-P can be effectively utilized by oil tea seedlings in acidic red soils, suggesting that sparingly soluble inorganic P is the main source of plant P in unfertilized soil.