Yara deliver more than just fertilizer, instead Yara supply complete crop nutrition and following Yara's recommendations will ensure the optimum return on investment in fertilizer.
What is your return on investment in nitrogen?
Yara nitrogen response trials confirm you should be expecting a return of at least 400% on nitrogen applied to cereals and oilseed rape. At the optimum rate, £1 spent on nitrogen will deliver around £5 return, using last season’s prices, as can be seen below.
To achieve this return on investment it is important that no other nutrient is limiting, and that nitrate nitrogen is applied accurately and that it is applied at the optimum rate, at the most appropriate time.
These three factors have a bearing on the returns expected from nitrogen and therefore form the basis of Yara's recommendation.
A total of 12 nutrients are required by all plants and if any of these are less than optimum, yield will be restricted.
This is illustrated by Liebig’s 'Law of the minimum' which states that 'Yield is limited by the nutrient that is in least supply'.
Twelve nutrients are required by plants: Nitrogen, Phosphorus, Potassium, Sulphur, Magnesium, Calcium, Boron, Copper, Iron, Manganese, Molybdenum and Zinc.
Typically nitrogen is the most limiting factor, but shortages of any other nutrient will limit yield, and limit the benefit of nitrogen applied.
As well as being important in their own right, most nutrients have the role of ensuring that the most is made of any nitrogen applied.
Nutrients are also important for plant health, improving resistance or tolerance to disease. Shortages in any nutrient (particularly potassium, calcium, boron, manganese, copper or zinc) could lead to an increase in disease levels, which if not controlled effectively through fungicides can also decrease the yield response from nitrogen.
Accurate application is essential and requires quality product which can be evenly applied through correctly calibrated machinery.
The accuracy of application achieved by liquid fertilizer systems is well renowned, especially over large boom widths.
Very good accuracy can also be achieved using a well calibrated fertilizer spreader if a good quality uniform granular or prilled product such as YaraMila or YaraBela grades is being applied.
The calculation of nitrogen response is based on small plot trials, with no application limitations due to the size involved. When applying on-farm, the accuracy of application (Coefficient of Variation, CoV) can have a bearing on the performance of the crop as the poorer the application the bigger the variation in rates in different areas of the field.
Product quality is important for reducing the CoV, whether quality compound eg YaraBela Extran, or liquid fertilizer eg Chafer Nuram.
The third step is to maximise the returns specifically from nitrogen, mainly through targeting the right rate.
Apply nitrate nitrogen at the right rate and at the right time
Applying the right source of nitrogen at the right rate and at the right time ensures the optimum yield and the maximum response.
Calculating the optimum rate of nitrogen is something that can only really be achieved retrospectively from a nitrogen dose response trial. Even with this information it is generally accepted that there is a 40kgN/ha tolerance either side of the calculated value, therefore it is not a figure, but a range.
The average Yara optimum from the last decade of trials in winter wheat is 225kgN/ha (therefore a range from 185kgN/ha to 265kgN/ha).
Several organisations giving recommendations for winter wheat would suggest keeping nitrogen rates simple and apply 200-220 kgN/ha for most situations.
Although this may seem reasonable considering the optimum from Yara trials varies very little each year, this is because the average can hide the detail.
Looking back again over the last decade of trials, the optimum range of nitrogen is actually only correct 55% of the time. Therefore 45% of trials require either less than 185kgN/ha (~25%) or more than 265kgN/ha (~20%).
Applying the average optimum would therefore only be right on 5 or 6 fields in every 10.
A similar story is true for oilseed rape, with only 50% of the results fitting into the average optimum range, with 20% below and 25% above. In oilseed rape even greater variations can occur, due to the link between canopy size and optimum nitrogen rate.
The average optimum may be the right starting point, for plans put together during the winter, however this should not just be stuck to as a matter of course during the season, without taking the seasonal variations into consideration. The last few years have shown some big differences which can affect this optimum, from high rates of mineralised soil nitrogen in 2014, to late drilled, poorly rooted crops in 2013.
Fine-tune nitrogen applications through the growing season
Fine-tuning nitrogen recommendations in-season, based on assessments of the crop, is an important step to getting closer to the optimum rate, helping to take efficiency of uptake and soil nitrogen into account. There are different ways this can be achieved, using visual assessments or lab tissue analysis, however Yara has developed a range of tools to simplify the processes.
Shown above are the results of a recent trial where five plots have all received different rates of nitrogen, 0, 100, 200, 300 and 140 followed by the N-Tester recommendation.
N-Tester readings were been taken weekly since the beginning of April to monitor the nitrogen levels of the plots. On the last plot, N-Tester was used to make a recommendation of nitrogen for the final dressing.