ON FARM NORTHERN CATTLE FEEDBASE f Not as simple as just adding water Forage crops grown under quality than the temperate species. when growing rapidly, Rhodes grass irrigation in northern WA “To provide cattle with a suitable diet can produce more stem than leaf. have the potential to achieve for growth with adequate energy and This, combined with cattle avoiding any massive daily growth rates, crude protein levels often requires a areas where there are dung or urine provided the inputs are well trade‑off between biomass production patches, means that under rotational managed, new research is finding. and feed quality.” grazing it can rapidly become rank and unpalatable.” The MLA Donor Company The research focuses on (MDC)‑funded project is evaluating three areas: In these situations, a hay cut is often grass and legume species to determine required to reset the pasture. 1. High quality data the best fit for the climatic conditions “First, we’re collecting high quality While optimum fertiliser rates for and how best to manage them. baseline data on production and feed irrigated forages are still to be Department of Primary Industries quality for northern WA, with its unique established by the research, fertiliser and Regional Development research combination of climate and soils,” rates trialled were 1kg and 2kg officer Geoff Moore said it’s essential Geoff said. N/ha/day applied monthly, with the to work with the environment, which, in 2kg rate predominantly increasing the This information will inform economic percentage of crude protein rather than northern WA, presents opportunities analysis of irrigation developments. and a few challenges. biomass production. One trial is evaluating the interaction “With high solar radiation and between the DM of fodder production The project is also simulating grazing warm‑to‑high temperatures year‑round, and feed quality, for a range of tropicalscenarios to fine‑tune Rhodes grass high production is possible, given (C4 or high‑temperature tolerant) management. irrigation and adequate fertiliser,” annual fodder grasses, including hybrid “We found extreme rotations, such as Geoff said. sorghum and pearl millet. Another trial defoliating every week, reduced biomass is looking at the potential for irrigatedproduction too much,” Geoff said. “Recent results from an annual fodder grain or silage production. grass trial showed daily growth rates “The window for the sweet spot with of 200–250kg dry matter (DM)/ha, with 2. Fine‑tuning management This involves working with industry grazing Rhodes grass is narrow, so we are 3,500–5,000kg DM biomass after just also looking at alternative species such as 19 days of regrowth. to improve and refine management, particularly for Rhodes grass under panic grass, Jarra finger grass and kikuyu, “On the other hand, from October to ‘stand‑and‑graze’ systems. Rhodes which may be easier to manage.” April, temperatures in the region can grass is currently the main species 3. Exploring new options be extreme, with average monthly grown under irrigation in northern WA. “We’re in a good position to evaluate maximums often above 40°C and new plant options for irrigated daily maximums often reaching the “Rhodes grass is well suited to the soils and environment, and under irrigation agriculture, including tropical legumes mid‑forties. like centro, butterfly pea, lablab it can produce high growth rates of “These extreme temperatures limit the 100–200kg DM/ha/day, but it’s not and cowpea, as well as alternatives,” growth of temperate species such straight forward to manage under Geoff said. ■ as lucerne. grazing,” Geoff said. “The tropical species are much better “Growing leaf material is the key to Geoff Moore adapted, but generally have lower feed good animal production; however, E: geoff.moore@dpird.wa.gov.au 2222