From YARA UK
Effective uptake of nitrogen fertilisers to optimise yields, maximise spending and minimise losses is a key challenge for the arable sector, and to maximise Nitrogen Use Efficiency (NUE) there are three key factors to consider: right product, right timing and right rate.
Natalie Wood, arable agronomist at YARA says using a product that contains nitrate nitrogen means it is immediately available to the crop and does not have to undergo a conversion process first, like urea fertilisers might, taking up to six weeks in cold conditions.
Another important part of product choice is sulphur, says Ms Wood.
“With up to 97 per cent of UK soils being deficient in sulphur then it is likely that you do, so growers should consider a nitrogen sulphur (NS) or an NPKS product.”
There is a close relationship between nitrogen and sulphur within the plant meaning that there needs to be sufficient amounts of both for each to be utilised efficiently within the crop.
“If we need sulphur, it makes sense that sulphur is applied little and often with nitrogen to improve the NUE.”
The first application should go on as soon as the crop starts to grow, usually around the end of February. Getting the first nitrogen and PKS on early means that the crop can get off to a good start in the spring and build plenty of biomass before the ‘biomass cut-off’ date of around the end of March when the plant switches to its reproductive phase.
Rates will depend on crop type and market; but it is important not to apply more than the crop requires.
Taking feed wheat as an example, Ms Wood says: “Usually 220kgN/hectare is a good target to base your calculations on. The first application at the end of February should be about 70-100kgN to influence that biomass growth. Second dressing will be similar at about 100kgN/ha.
“The last dressing is where you are able to fine tune the rate as the majority of the nitrogen has already gone on. There are various tools that can help with this final application, including the Yara Bluetooth N-Tester which measures how much nitrogen is in the crop.”
Another option is variable nitrogen applications. Yara’s N-Sensor scans the crop and identifies real-time what the nitrogen levels are and then adjusts the spreader/sprayer accordingly.
Variable application can also be done using Yara’s AtFarm software – a currently free, web-based programme that allows users to map their fields and get variable application maps based on the NDVI biomass; which then can be imported to variable-rate spreaders/sprayers. It uses the algorithm that is in the N-Sensor to get results not solely based on NDVI, which can be saturated at certain growth stages.