Acid and poor soils? Inoculate your legumes

A comprehensive farm study has emphasised the need for growers of pulse crops and legume pastures in acid soil areas to inoculate seed with rhizobia bacteria each time they sow.

Jo Slattery of Agriculture Victoria, Rutherglen, collected soil and plant samples from 50 farms across victoria. She found that where there was a history of pulse or pasture legume production on soils with good nutrient status, there was generally a greater build-up of rhizobia bacteria in the soil. The higher the population the more likely there would be effective root nodulation and, hence, nitrogen production.

"There isn't a tradition of growing pulse crops on acid soils, as opposed to the neutral to alkaline soils elsewhere, and so it is important to inoculate legume seed before sowing," Ms Slattery said. "As well, rhizobia are sensitive to acid soil conditions."

Ms Slattery said the survey also showed that rhizobial populations could be materially affected by the nutrient status of the soil.

Low levels of nutrients such as phosphorus and nitrogen, and organic carbon, were associated with low rhizobial counts — the implication being that a history of legume production alone would not maintain high levels of rhizobia if the nutrient status of soils was low.

Program 3.5.2 Contact: Ms Jo Slattery 02 6030 4500