Analysis of the response of pasture legumes to phosphorus in a controlled environment

Abstract

White clover, red clover, suckling clover, and lotus were grown under a controlled environment in soil to which phosphorus had been added at levels of 50, 250, 600, and 2000 ppm w/w. Growth analysis was used to explain differences in yield in terms of attributes describing growth, P uptake, and assimilation. The yield of white clover, red clover, and lotus increased markedly with P supply. Suckling clover responded less to P and its yields were smaller than those of the other species except that of lotus at 50 ppm. In all species the rate of P uptake per unit root length increased with P supply. There were differences in uptake rate among species but these could not be consistently related to differences in yield. The efficiency with which absorbed P was used in the production of dry matter declined as the P supply increased in all species. Lotus used P with the greatest efficiency. Root/shoot ratios and root length/weight ratios were affected by an increase in P supply. Suckling clover had the highest root/shoot ratios, and lotus had the lowest. Suckling clover also had high root length/weight ratios. For these legumes, attributes such as root/shoot ratio, root length/weight ratio, P concentration, and inherent size appear to be more useful than P uptake in explaining response to P.

Keywords:

• phosphorus
• white clover
• Trifolium repens L.
• red clover
• Trifolium pratense L.
• suckling clover
• Trifolium dubium Sibth.
• Lotus pedunculatus Cav
• Leguminosae
• plant growth
• nutrients (plant)
• fertiliser rate