Perennials are for high feed quality and more production

Such conditions commonly occur across the state and result in widespread ending of winter legume growth of species like subs and medics.

As often happens, when these legumes senesce in spring, they fail to regrow from late spring/summer rains, which occurred this year. Hence the key role of tropical grasses and lucerne that can grow as fast as 150 kilograms of dry matter per day per hectare. This can all be high quality feed.

In contrast where no decent perennials exist weeds like Bathurst burr can be all that responds, although in good moist events in some areas annual summer grasses like Liverseed can contribute good feed. Out of season rain occurred on our property late November 2019 so we purchased 250kg steers on the strength of a partial break. Conditions again dried off but fortunately an ending of the drought for us occurred late January 2020. Having only grazed tropical grasses they gained around 250kg/head and were sold early June.

Further purchases in March/April gained similar weights grazing tropical grasses to June, then winter legumes and oats over winter and since October again tropical grasses. They have made a profit of over $800/head.

Livestock, in this case steers, can gain on average well over a kg/day on perennial grasses. In our case the perennial grass is mainly Premier digit and soil is mainly acidic sandy to light loam. These pastures also contain winter legumes, serradella and sub clover. Because of the drought the legumes didn't contribute much feed in 2017-19 but did in 2020.

These type of growth rates can only be achieved on perennial grass pastures (native, tropical or temperate) if soil fertility is high. It is also important to appreciate that lighter soils, not that long ago commonly regarded as not much suited to "fattening", can equally provide quality feed as that of heavier soils with higher natural fertility.

A key aspect of high feed quality is the correction of soil deficiencies. We are not "high input" grazing but we monitor soil fertility carefully and correct deficiencies in a conservative fertiliser program as required. Sulphur and phosphorus are our main deficiencies, also nitrogen. Provided suitable legumes are grown for a given area, and sensibly managed, they can provide nitrogen for the grasses.

Even from day one when we purchased our property 11 years ago, we have used single superphosphate at 100kg/ha (11 per cent available sulphur, 8.6pc available phosphorus). While initially phosphorus and sulphur levels were low these have steadily increased with fertiliser applied at this rate. Soil tests indicated no fertiliser was required in the past two years so none was used. We will check again in January to decide on the 2021 fertiliser program.

Important has been recent research that shows the winter legume serradella, which does extremely well on our lighter acidic soils, including also with acidic subsoil, performs at near maximum productivity at lower soil phosphorus levels than is required for most other legumes. On our low phosphorus buffering soils (PBI) serradella requires a Colwell phosphorus test of around 20mg/kg but sub clover requires 30 mg/kg. Important for making fertiliser decisions.

To get the best quality and quantity from tropical grasses, native and temperate perennials on once regarded poor country, it is sometimes necessary to top-dress nitrogen fertiliser in addition to correcting phosphorus and sulphur deficiency. In years with good companion legume growth, such as 2020 for many of us, they may well have supplied all the nitrogen required. Well nodulated legumes can fix 25kg/ha nitrogen per t/ha legume growth (drymatter basis) and 4t/ha legume growth has not been unusual this year, equivalent to 200kg/ha urea.

But in years with little legume growth, such as 2017-19 for many, it was commonly highly profitable to add nitrogen fertiliser to our perennial grass. It has proven profitable and sound policy.

Next week: Northern grazing management research valuable to NSW.