The impact of farming systems with more legumes and nutrient inputs on nitrogen phosphorus and potassium inputs and use

Jon Baird1, Jayne Gentry2, David Lawrence2, Lindsay Bell3, Darren Aisthorpe2, Greg Brooke1, Andrew Erbacher2, Andrew Verrell1, Andrew Zull2, Kaara Klepper4

1NSW Department of Primary Industries, Narrabri, NSW, 2390, jon.baird@dpi.nsw.gov.au

2Qld Department of Agriculture and Fisheries, Toowoomba, Qld, 4350

3 Commonwealth Scientific and Industrial Research Organisation, Toowoomba, Qld, 4350

4 Grains Research and Development Corporation

Abstract

Farming systems are currently underperforming in terms of yield, due to challenges that include declining soil fertility, herbicide resistant weeds and increasing soil pathogens. Farming system changes are required to maintain and improve productivity. In 2014 long term farming systems research began at seven sites located throughout Queensland and northern New South Wales. These experiments assessed the impact of nine farming systems with respect to numerous measures, including system production and economics, resource use efficiency, pathogen loads/populations, weed populations and soil health. Changes included modifying farming systems to include more legumes and applying fertiliser rates aimed at higher yield potential. The farming system ‘modifications’ impacted several facets of nutritional results. By applying nutrients via fertiliser (nitrogen (N) and phosphorus (P)) to meet the demands of 90th percentile grain yield potential (higher nutrient system), nutrient exports and inputs were balanced, resulting in stable mineral N when compared to current growers’ practice (baseline system) at 10 of the 11 sites. The higher frequency of legumes (higher legume system) increased N and potassium export from the system at most sites (9 of 11 sites), but there was no legacy benefit to plant available N (nitrate and ammonium) for the following grain crops compared to growing non-legume crops. Longer-term examination of farming systems may lead to greater differentiation between systems and geographical location, providing greater insights into the impact different farming systems have on nutrient balances and long-term soil fertility.

Host

The Australian Society of Agronomy is the professional body for agronomists in Australia. It has approximately 500 active members drawn from government, universities, research organisations and the private sector.

Photo Credits

David Marland Photography david_marland@hotmail.com Graham Centre for Agricultural Innovation, Charles Sturt University

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