The feasibility of fertilising oats and forage sorghum with nitrogen and phosphorus in the Brigalow belt of Queensland: A modelling study

Abstract

Annual forage crops such as oats and forage sorghum are sources of high-quality feed for mixed grain and beef enterprises in the northern region. However forage productivity declines over time as organic matter and subsequent supply of nutrients decrease with continued cultivation. The use of fertilisers to maintain production from oats and forage sorghum is common practice in higher rainfall and irrigated situations, however fertiliser use in generally drier and more variable environments such as the Brigalow belt is minimal despite declining productivity. We undertook a desktop, modelling assessment of the feasibility of fertilising these forages with nitrogen and phosphorus in the Brigalow belt in southern and central Queensland to better understand the dry matter and feed quality responses necessary to generate positive economic impacts.
Results indicated significantly higher dry matter production is possible with fertiliser use, which can lead to higher animal liveweight gain and stocking rates. However under current market conditions the additional costs associated with applying fertiliser outweighed the extra benefits that can be generated. A combination of high dry-matter and animal production responses, lower costs associated with fertiliser application and positive price margins for the livestock grazing the forage are required to make fertiliser application consistently profitable. This modelling study demonstrates land-managers in the northern region need to carefully consider and monitor both the production and economic responses from trial areas before paddock scale applications are implemented.