Alfalfa,Medicago sativa L., in highly weathered, acid soils

Summary

Previous selection of alfalfa for productivity in acid soil resulted in germplasms with more acid soil tolerance, but which required high P levels to be responsive. In this investigation, the field performance of alfalfa germplasms (selected in either acid or limed soil conditions) was evaluated over three years at varying soil pH and P levels. Advancement made by selection in high and low yielding soil environments was also determined.

Increasing soil pH from 4.8 to 7.2 increased alfalfa dry matter yield as did increasing P application from 80 to 200 kg P ha⁻¹. At the acid end, levels of Al and Mn were not found to be toxic, but N content of tissue increased with increasing soil pH indicating better N₂-fixation due probably to improved Mo availability. In one of the three years, the acid selections yielded significantly higher than the base population when data were pooled for all soil conditions, but there was no advantage in low pH soil. Acid selections were also more responsive than limed selections to P application over all pH levels. Acid soil selection appeared advantageous in increasing the productivity of alfalfa for use in high yielding environments.