Phosphorus requirements for the early growth of red clover, trefoil and flatpea

Abstract

A greenhouse experiment was conducted to compare the P requirements for early growth of red clover (Trifolium pratense L.), birdsfoot trefoil (Lotus corniculatus L.) and flatpea (Lathyrus sylvestris L.). Phosphorus sorption isotherms were used to predict P fertilizer additions required to adjust two Appalachian soils to eight equilibrium solution P levels (0.005 to 0.50 ug P/m1).

Flatpea dry matter production was equal to or greater than that of red clover and trefoil at low adjusted P levels.

However, with increasing P level, flatpea dry matter yield peaked at a lower production level and at a lower adjusted P in soil solution than the other two legumes. The approximate P level in soil solution for 90% of maximum yield was as follows: flatpea, 0.074 ug P/ml; red clover, 0.104 ug P/ml; and trefoil, 0.141 ug P/ml.

Flatpea apparently has a lower internal P requirement than either trefoil or red clover. Phosphorus concentrations in top growth for 90% of maximum yield were found to be: flatpea, 0.21%; trefoil, 0.24%; and red clover, 0.27%. The low internal P requirement and the ability of flatpea to achieve maximum yields at low adjusted P levels would suggest advantages for this legume in low fertility soil environments.

Key words:

• P sorption isotherms
• legume growth
• plant P concentration