IRRIGATED fodder production under centre pivot irrigation is opening up new opportunities for the beef industry in northern WA and warm weather didn’t deter producers, industry and consultants from attending a pasture and fodder field walk at the Water Corporation’s Waste Water Treatment site at north Broome recently.
Jointly organised by the Department of Primary Industries and Regional Development’s (DPIRD) Northern Beef Development project and the Water Corporation, highlights of the day included DPIRD’s series of irrigated agronomy trials and an introduction to the sterile leucaena project, both of which are co-funded by MLA Donor Company, and an insight into fine-tuning irrigation scheduling.
DPIRD research officer Geoff Moore said the environment in the north presented both a great opportunity for agriculture and a challenge.
“The year-round high levels of solar radiation and warm to hot temperatures, combined with irrigation and adequate fertiliser, are a recipe for very high biomass production,” Mr Moore said.
“This was highlighted at the field walk in many of the trials.
“The results from the annual fodder grass trial showed daily growth rates of 200 to 250kg dry matter (DM) per hectare, with 3.5-5 tonne (DM) biomass after just 19 days of regrowth.
“However, the high growth rates and high to extreme temperatures over the October to April period presented a challenge, with a trade-off between biomass production and feed quality.
“The high temperatures negatively impact both the growth and quality of temperate species like lucerne.
“The sub-tropical and tropical species are much better adapted, but they have inherently lower feed quality and the very high growth rates increase the proportion of structural carbohydrates.”
Mr Moore said Rhodes grass was the species most widely grown under irrigation in the north and it was well suited to the soils and environment, but could be challenging to manage under grazing.
“Our results from last year clearly showed that in order to grow animals on Rhodes grass, the important measurement is the amount of leaf produced, not the total biomass.
“The stem provides a maintenance diet, about 7-8MJ of energy, while the leaf is suitable for growing animals.”
Mr Moore said it could be difficult to maintain irrigated Rhodes grass pastures with a high level of leafy growth under rotational grazing.
“There is a combination of extremely high growth rates once the biomass reaches about 3t/ha, an increasing proportion of stem compared to leaf, and cattle avoid dung and urine patches, and areas under-grazed on one rotation are likely to be rank and have low palatability when the pasture is next grazed.”
Given these issues, the Mosaic Agriculture project is looking at fine-tuning Rhodes grass management to maximise the amount of leaf on offer and evaluating alternatives to Rhodes grass.
Trials evaluating alternatives to Rhodes grass, include perennial grasses, kikuyu, panic grass and Jarra grass, which early results indicate may be easier to manage under direct grazing.
At the recent field walk, DPIRD senior development officer Chris Ham described the results of his work with commercial irrigators to fine-tune irrigation scheduling.
Mr Ham said it was important to take the time to plan, budget, prepare and ask lots of questions before investing in irrigation, mentioning resources are available online from Irrigation Australia, and reputable companies and researchers such as DPIRD and CSIRO.
“Site selection, soil type and water quality, depth and adequate flow rates are critical choices that impact the long-term profitability of irrigation,” Mr Ham said.
“If you are managing an irrigation system, learn as much as you can about the soil type you are on and some basic plant physiology to understand the difference between tropical (C4) and temperate plants (C3).
“Plants behave differently and can require dissimilar watering strategies – it’s important station managers and staff understand the plant requirements to make effective and efficient irrigation decisions.”
Technology can support decision making but it takes time to learn how to effectively use it.
Soil moisture probes provide feedback on what the roots are doing.
Satellite technology, such as CSIRO’s Irrisat website, can assist irrigators to monitor crop health and water use.
Users can find specific paddocks and monitor them using satellite technology using the link – https://irrisat-cloud.appspot.com/
Mr Ham said benchmarking irrigation system outputs and efficiency was important as manufacturer specifications were provided as a guide, and users may be putting on more or less water than they think.
“Matching system performance to soil moisture and crop productivity is vital information for advisors and consultants – it is hard to manage it if you don’t measure it,” Mr Ham said.
“The decisions you make daily are the ones that truly affect profitability.”
Field walk participants also visited DPIRD’s leucaena nursery which features a diverse range of leucaena species.
DPIRD development officer Sam Crouch described the project investigating the feasibility of developing a sterile leucaena for northern WA.
“The project is exploring strategies to breed a sterile leucaena by applying novel breeding and molecular technologies which, if successful, should significantly reduce the weed risk for the rangelands of northern Western Australia,” Mr Crouch said.
“The project involves exploring breeding strategies, economic possibilities and practical feasibility for a sterile product.
“We are focusing on developing a sterile leucaena that has all the production benefits of leucaena grown in Queensland, but does not produce viable seed, minimising the weed risk to Western Australia’s northern rangelands.
“In some conditions leucaena can become a weed of the natural environment, as it is on the Ord River near Kununurra.
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“Leucaena is highly valued by beef producers in Queensland, where it is the most profitable tropical pasture.”
This year, DPIRD’s mosaic agriculture team assembled 15 species of leucaena to evaluate their adaptation to the conditions in northern WA, and field nurseries have been established in Carnarvon, Broome and Kununurra to reflect key climate and soil types.
Mr Crouch said plants would be assessed on their ability to recover after cutting (grazing), drought tolerance, feed quality and growth habit.
The elite plant parent material will go into the breeding program to produce a sterile product.
“The goal is to produce a 100 per cent sterile leucaena that is adapted to the environment, has high feed quality and is easy to manage,” he said.
“This project is focusing on the feasibility of developing a sterile leucaena, and it is worth keeping in mind that a typical plant breeding program takes about 10 years.”
Mr Crouch and a pastoralist from the Kimberley recently attended the International Leucaena Conference in Brisbane, Queensland, which included a three-day tour of cattle producers who grow leucaena.
“The producers identified the establishment of leucaena as both difficult and costly and highlighted the fine-tuning of weed management and soil fertility as being integral to successful establishment of the plant.”
