Cooks Myall - Legumes in tropical grass

Summary

Cooks Myalls Landcare Group members have been successfully sowing subtropical grasses, primarily bambatsi panic, premier digit, Gatton panic and Rhodes grass for almost a decade and find they persist and perform well in favourable seasons. Members now seek ways to increase productivity and returns from these pastures.

Nitrogen availability is a key driver of growth which can be supplied to the pasture in a number of ways. Application of urea, via topdressing is the most common way of providing nitrogen but members were interested in improving grass growth and quality using companion legume species to fix nitrogen.

Two trials were sown comparing ways of increasing subtropical grass production over summer. The first compared two mixes of temperate annual legumes with urea application and the second comparing two cultivars of the tropical legume Desmanthus with urea.

In the years of the trial neither urea nor the temperate legume treatments significantly changed the production or quality of the subtropical grasses compared with the control, however where the temperate legumes were sown, winter pasture production and quality was dramatically improved and it was considered worthwhile for that reason alone. The most productive and persistent legume sown were new varieties of Sub. clover (Trifolium Subterraneum).

Desmanthus was new to the district and low summer rainfall along with poor seed germinability prevented successful establishment so this trial was abandoned. More work may be needed to look at the adaptation and agronomy of the plant itself before any further large scale plantings could be tried.