Distinguishing between grass and legume species for efficiency of phosphorus use

A proposed screening technique for efficiency of P ultilisation was investigated using 10 grass and 11 legume species. They were grown in pots at 2 P levels, one limiting growth, and results are presented as a diagram of yield at high soil‐P against yield at low soil‐P. This method distinguished between species known to be sensitive to soils low in P and those tolerant to such conditions using the species examined and with other examples obtained from the literature. The grasses, as a group, appeared to be more tolerant of soils low in P than were legumes. They had much more intensive root systems, with longer total root lengths, thinner roots, and much longer root hairs. The grasses were also shown to divide their P between shoot and root in the same way irrespective of the soil‐P level, while the legumes retained more P in the root in soils low in P.