Seed preinoculation and soil liming for growth of forage legumes on acidic clay soils

Abstract

Forages produced in the north central interior of British Columbia are low in percentage crude protein (CP). Growing lucerne (Medicago sativa L.) should increase forage percentage CP, but many of the soils are considered too acidic for this species. The objective of three field experiments, conducted at the Prince George experimental farm, was to evaluate management practices that might accommodate the growth of lucerne on acid soils without the expense of liming. Experiment 1 compared three legume species (lucerne, alsike clover (Trifolium hybridum L.) and red clover (T. pratense L.)), preinoculated lime-coated seed (GNRTM, Grow Tec Ltd, Nisku, Alberta), and soil liming on root nodulation and forage dry matter (DM) yield. Experiment 2 compared lucerne genetic lines, seed preinoculation and soil liming on root nodulation and forage DM yield and percentage CP. Experiment 3 compared lucerne rhizobia genetic strains, seed preinoculation and soil liming on root nodulation, forage DM yield and percentage CP.For effective nodulation, lucerne required seed preinoculation, whereas alsike clover and red clover did not. Lucerne persisted longer than alsike or red clover. In Expts 2 and 3, the combination of lime and preinoculation increased lucerne DM yield by 136% and %CP from 9·2 to 15·4. The addition of lime alone increased lucerne DM yield by an average of 130% and %CP from 9·2 to 16·3. With preinoculation alone, lucerne DM yield increased by 100% and %CP increased from 9·2 to 12·7. Although using preinoculated lime-coated seed alone is not as effective as lime alone, coated seed may be the preferred method, based on ease of application and cost. Neither the six lucerne lines nor the three rhizobial strains evaluated resulted in improved root nodulation under acidic conditions.