ADAS scientists have brought together new and topical information to help farmers make correct nitrogen decisions this Spring/Summer. The full text of the advice can be downloaded below this article
Summary
• Total overwinter rainfall (to 24 March) indicates that winter 2009-2010 was wetter than average in many arable areas. This can be taken into account when assessing SNS Indices in fields using the Index tables in RB209, and may result in slightly higher recommended N rates (up to 20 kg N/ha) in some situations. Final N decisions should also take account of other information, local experience and the performance of previous crops.
• Some reports have indicated that measured SMN levels in early spring 2010 were on the low side. This corresponds with some research evidence that average SMN levels in autumn 2009 were also very slightly lower than normal. However, delayed mineralisation this year due the unusually cold winter may mean that less of this soil N pool was picked up in SMN analyses this year. However, the full contribution of mineralised N is still likely to be available for crop uptake in the spring and summer.
• Most samples for SMN analysis will now have been taken. Any last minute sampling should only be considered if there has been no application of N fertiliser or organic manure this spring. Remember that samples must reach the laboratory with minimum delay, as results can increase by up to 10% for each days delay between sampling and analysis, even when samples are kept cool.
• Main N dressings may need to be slightly delayed this year but the principles of applying N are unchanged.
• For land inside an NVZ, make sure that all nitrogen applications to crops (fertiliser and livestock manures) comply with the N max limit which is calculated across the whole area of each crop type on NVZ land on the farm. The NVZ N max limit for spring N applied to oilseed rape is now 250 kg N/ha but including any N applied last autumn.
• All farms and land inside an NVZ must also comply with all other NVZ rules. Key requirements now are to keep plans of nitrogen use up to date and to keep the required field records (a common failing). Non compliance can result in a reduction in the Single Farm Payment.
• Water soluble sulphur should be applied this spring to potential deficient crops. One of the most potentially deficient crops is grass silage and consideration should be given to whether sulphur application is needed to each cut.
• A summary of over 110,000 commercial routine soil analysis results from 2008-09, shows a wide range of soil PK Indices ranging from worryingly low to unnecessarily high.
• A table of the NPK content of different types of organic manures is provided with their current financial value. Allowing for these nutrients can result in large financial savings.
For the full details of this advice, please download the free document below this article. If you have any queries, please contact the ADAS customer services line on 0845 766 0085.