Down to Earth with Bob Freebairn: Tropical grass big help in providing drought feed

It was mainly a wheat sub clover rotation and except for the odd lucerne paddock, which commonly didn't persist for long.

Such a season occurred for us, and many others, this year in the northern half of the Central West, as well as much of the North West Tablelands, slopes and plains.

Many coastal areas are similarly affected.

In our case, total rain for a period of just under six months, from April 7 to October 4, was 55 millimetres - 22 per cent of average rain for this period.

Dual purpose crops provided good winter feed, largely based on early sowing in late February, and on stored sub soil moisture.

But by early October these crops had mainly been utilised and their soil water had run out.

Legumes, especially serradella, provided useful winter feed.

There was also useful carryover dry feed from last summer.

However, by early October feed was becoming scarce but what was different to my growing up era was that much of our property, 50pc, has been established to tropical grasses combined with winter legumes

A 20mm rain event that occurred on October 5, while not breaking the possibly-emerging drought, provided almost immediate respite.

Much of our property is acidic through the profile hence why lucerne is not that valuable as a summer feed option for us.

However, premier digit grass, and consol lovegrass are acid soil tolerant and are also able to root well into the sodic clay loam sub soil, common on much of the farm.

The oldest tropical grass stand on our farm is now 20 years with no sign of decline.

It is common to find good stands throughout NSW now well over 30 years old.

Hence tropical grasses, provided suitable varieties are chosen, have dramatically lifted spring, summer and autumn feed should periodic rain events occur during their main growing period.

Even before the 20mm received in early October, they were commonly growing from leftover sub soil moisture that accumulated from good March rains.

A late frost for us on October 6 burnt back growth on lower-lying paddocks but recovered growth began a few days later.

A big change from my younger days, and for many areas, has been acid soil correction via lime use.

Provided only top soils are acidic, lime can change these into good soils for growing lucerne.

Good varieties combined with sound grazing management can often achieve four or more years of good lucerne growth throughout the year.

An excellent feature of tropical grasses is that unless heavily grazed over an extended period, they are able to capture storm rains effectively.

A good example was documented in research at the NSW Department of Primary Industries research centre coming out of the 2020 drought.

Lucerne had very little groundcover with much of the breaking heavy rains running off the paddock with slow growth recovery.

In contrast, tropical grass captured most of the rain and grew at up to 150 kilograms per hectare drymatter per day.

In no time there was over four tonne per hectare tropical grass compared to less than one t/ha lucerne.

Tropical grasses are part of our drought management strategy.

Especially on our lighter textured soils, they are able to grow feed even on rainfall events as low as 5mm.

Even in droughts there are commonly occasional light to moderate rain events, quickly forgotten if one doesn't have the pastures capable of using them.

Important for good tropical grass production is good to high soil fertility.

The same applies to native grasses, which have a similar growth pattern to tropicals, but for most areas at a slower growth rate.

Winter legumes can grow well with them, suppling nitrogen at around 20kg/ha/t legume drymatter.

If poor legume growth has occurred in previous years it is commonly highly economical to add via fertiliser.

Next week: Correct rhizobia worth millions if right for legume crops and pastures.