Complementary forage rotation is sustainable
From the April 2009 edition of Agriculture Today.
An intensive system offering dairy farmers the opportunity to produce more home grown feed than could be achieved from pasture alone is environmentally sustainable, according to a study.
Project leader, Associate Professor Yani Garcia, said FutureDairy’s complementary forage rotation (CFR) may have benefits to dairy farmers with limited land and irrigation, particularly if grain-based concentrates become more expensive.
The CFR involves growing two or three crops on the same area of land within the one year, for example, maize, forage rape and Persian clover.
“The idea is to allocate inputs, such as nitrogen and water properly in a relatively smaller area, rather than scattered throughout the whole farm with reduced efficiency,” Yani Garcia, based at Elizabeth Macarthur Agricultural Institute (EMAI), said.
Annual yields from the CFR are more than 40 tonnes dry matter per hectare, compared to a maximum of about 20t from the best managed perennial ryegrass pastures.
“We use crops that complement each other or the system. But the CFR is an intensive system, involving high inputs of fertiliser and water so we were particularly interested in its environmental impact,” said Assoc Prof Garcia.
Over the past four years, FutureDairy conducted several studies to investigate this.
Firstly, Pancha Shrestha evaluated the impact of growing double- and triple crop CFRs on soil fertility, health (microbial activity) and pathogen build-up in the soil.
The study found no evidence of any adverse effect of the CFR on these soil characteristics.
In a larger scale study Bertin Kabore monitored the key indicators of health status and nutrient flows within the system over four seasons.
The data allowed Mr Kabore to assess the likely impact on areas away from the CFR site and to compare nutrient and water use efficiency with both intensively and extensively managed pasture systems.
The results showed no changes in soil organic matter or any adverse effects of an intensively managed CFR.
The organic matter content of a soil is an indicator of its potential fertility and it can be dramatically reduced after a few years of continuing cropping.
However this doesn’t seem to happen with CFR, which involves crops such as forage rape and legumes which provide beneficial properties to the soil.
Although the system requires a high level nitrogen fertiliser, it is twice as efficient at using nitrogen due to increased forage yields.
“And the high yields mean the CFR is also twice as efficient at using irrigation water,” said Associate Professor Garcia.
“The loss of soil nutrient through run-off was surprisingly low, even in a relatively wet year.
“Overall, these studies show that the increased intensification in home grown feed through CFR system can be achieved without adverse effects on soil physical and chemical properties,” he said.
FutureDairy’s ongoing research is investigating the CFR on a larger scale, where it is being grown on 35 per cent of the farm area, with the rest used for intensively managed kikuyu-based pasture, oversown with short rotation ryegrass each autumn.
Contact Dr Yani Garcia, Camden, (02) 9351 1631, sgarcia@usyd.edu.au or www.futuredairy.com.au
