Efficient Nitrogen Fertilizer Strategies for Tropical Beef and Dairy Production Using Summer Rainfall and Soil Analysis

Nitrogen (N) deficiency is a major limitation to growth of pastures in tropical and subtropical regions. In the tropics and subtropics of north-eastern Australia, grass yield is curvilinearly related (R2=0.75) to summer rainfall and the rate of N fertiliser. Data from a range of grazing experiments also indicate that beef and dairy production (kg/ ha) are related to N fertiliser rate in a curvilinear manner; production is near optimum at N rates of 250-300 kg N/ha/year, when summer rainfall is >1000 mm. Given the importance of summer rainfall and N fertiliser, climatic analysis can enhance the usefulness of N fertiliser recommendations. Using the Southern Oscillation Index, we can predict with a high level of success the probability of receiving above or below average rainfall in the following 3 months. Climatic analysis for fertiliser management was carried out for 5 key areas in Queensland where intensive beef and dairy production are practised.