Phosphorus Uptake and Dry Weight of Stylo and White Clover as Affected by Chlorine¹

Abstract

Caribbean stylo (Stylosanthes hamata L. Taub, ‘Verano’) and white clover (Trifolium repens L., ‘Ladino’) commonly grow in soils of markedly different available P status. In addition, stylo generally grows on highly leached tropical soils that have low levels of Ca and Cl. Before comparisons can be made of P utilization in these species, it is necessary to characterize their nutrient requirements, including the P × Cl interaction in each species, as this affects P uptake and growth. In this work, the effect of solution Cl level on P uptake by stylo and white clover was investigated in a controlled environment, solution culture study. Four P levels (1, 2, 4, 8 µM) and four Cl levels (10, 20, 30, 40 µM for stylo and 10, 30, 100, 200 µM for white clover) were used. Increases in the Fe, Cu, Mo, Ca, and S levels of a previously used nutrient solution were necessary, under the conditions of our work, to satisfy the requirements for growth of species in this study. Maximum dry matter yield and P uptake were recorded in white clover tops and roots in the 8 µM P/100 µM Cl treatment and in stylo tops in the 8 µM P/30 µM Cl treatment. Maximum root yield in stylo was recorded in the 30 µM Cl treatment, with no significant response to P at this Cl level. Stylo root P uptake was at a maximum in the 8 µM P treatment. The results demonstrate the necessity of adjusting the nutrient solution composition to match the requirements of the species under study before embarking on comparisons of differences in the uptake or utilization of a particular element.