Fertilising Cereal Crops with a New Approach
Methods for fertilising dryland cereal crops during the growing season could be altered in the future, as trials for a new approach enter their second year.
Promising trials last year found mid-row banding of nitrogen (N) in-season, increased uptake of nitrogen fertiliser in wheat by more than 50% – when compared with other methods of in-season N application in Victorian trials last year.
Agriculture Victoria’s regional research agronomist Ashley Wallace, who has undertaken the work as part of the Grains Research and Development Corporation (GRDC) and Victorian Department of Economic Development, Jobs, Transport and Resources (DEDJTR) Bilateral Research Agreement, said results from the trials were encouraging.
“Trials of mid-row banding of N in-season have produced promising results, including increasing fertiliser uptake by an average of 46% and up to 52% in wheat when compared with other methods of in-season N application.
“The method also boosted grain yield by up to 0.5 tonnes/hectare.”
While last year's results may have been influenced by exceptional rainfall and yields in many regions, including the Wimmera and Mallee where the trials were conducted, trials are being validated in 2017, with testing currently taking place at Ultima, Horsham and Telangatuk.
Mr Wallace said there had been a significant swing towards in-season management of N fertiliser in southern dryland cropping regions as growers looked to improve management amid variable seasonal conditions.
The crop’s demand for N is largely determined by its yield potential, which is strongly related to growing season rainfall.
“The time when crops are sown is a period when seasonal forecasts and hence, yield predictions have limited accuracy,” Mr Wallace said.
“This makes decisions around N application up-front difficult and risky.
"Applying N during the growing season better matches the timing of application to crop demand.
“Unfortunately, surface application of N fertilisers such as urea during the growing season increases the risk of N loss through volatilisation.
“Mid-row banding of fertiliser, where N is applied below the surface of every second inter-row, has the potential to reduce this risk, where the current research has focused on application during the growing season, rather than up-front at sowing,” he said.
Last year’s trials at Longerenong and Quambatook were undertaken in collaboration with BCG (Birchip Cropping Group) and aimed to compare mid-row banding with other forms of in-season N application, including top-dressed, liquid foliar and mid-row surface applications of N.
Mid-row banded treatments of liquid N were applied using a purpose-built three-point linkage mounted fertiliser banding gear which used twin disc openers to place fertiliser at a depth of 30 mm below the soil surface.
Each pair of discs was followed by a press wheel to assist with furrow closure.
Fertiliser treatments were applied at one of two times between the start of stem elongation and second node growth stages.
At each trial site, the first timing of application coincided with forecast rainfall in the days following, while the second timing of application coincided with dry weather forecast in the days following.
This approach was used to examine the effects of rainfall following application on potential losses of N and fertiliser use efficiency of the crop.
“Results from 2016 indicated that the benefit of mid-row banding to crop uptake of N was greater where rainfall was limited soon after application and the surface applied urea was not washed into the rooting zone,” Mr Wallace said.
“This indicates that mid-row banding could be a more effective way of applying N under drier seasonal conditions.”
GRDC Manager Soils and Nutrition – South, Stephen Loss, says it will be important to test mid-row banding in a range of seasons and situations to work out when and where growers will get the biggest bang for their buck.
“With 2017 looking like a more typical season, this year’s trials will provide another layer of data to inform industry about the potential benefits of applying N in-season through mid-row banding,” Dr Loss said.
He said that even if results from this year’s trials are again positive, any future adoption by growers will require careful consideration of economic and practical factors, such as the availability and the cost of midrow banding machinery, the speed with which operations can be undertaken, and potential crop damage in comparison with existing methods of spreading N fertilisers.
Such changes may also have impacts on other elements of the farming system that should be considered, such as the effect of inter-row disturbance and fertiliser application on weed germination and growth.
A report of the 2016 trial results, co-authored by Mr Wallace, is available for viewing and downloading via the GRDC website.
Image Source - Agriculture Victoria’s Regional Research Agronomist Ashley Wallace says work is continuing thisyear to validate the benefits of mid-row banding demonstrated in 2016 trials. Photo: Piotr Trebicki