Livestock and arable farmers alikelook set to benefit from the launch of a new service for maize growers tomeasure soil nitrogen. The new N-Min for maize soil test from fertilisermanufacturer, GrowHow UK, is an extension of the well-established service forcereals and oilseed rape. Uniquely it provides an accurate assessment of thetotal amount of nitrogen the crop will be able to get from the soil over thefull growing season.
Maize has become a staple foragecrop for many livestock enterprises and with more and more arable farmersbeginning to grow it as a biofuel, this introduction is very timely.
N-Min measures both the amount ofnitrogen in the soil at the time the sample was taken (the SMN Soil MineralNitrogen) and the Additionally Available Nitrogen (AAN), which is the amount ofN that will become available through mineralisation the turnover of organic Nto make plant available N. In this way it allows farmers and their fertiliseradvisers to calculate whether any additional nitrogen is required to allow thecrop to achieve its optimum yield potential. GrowHows N-Calc system has alsobeen updated to include maize so that N-Min results can readily be convertedinto field recommendations.
On-farm trials over the past fiveyears have shown that the N-Min service can be extended successfully to maizecropping. The trials were conducted across a variety of different regimes from thetraditional dairying scenario, with regular muck use, to rotational sites onmixed or livestock farms with less manure applied and, more recently, togrowers on arable units who are diversifying their cropping into energy cropsfor biogas production in anaerobic digestion plants.
Across the farms and the years ofthe trials work, the N-Min measured N reservoir or N that will be availableto the crop over the growing season varied widely. The values ranged fromless than 55 to over 500 kg N/ha.
It was interesting that whilst thelowest results were generally on sites that did not routinely receive manure,not all of the lower results were from un-manured fields, nor were the highestones always from sites which had received organic material of some kind, notesGrowHows Grassland Specialist, Elaine Jewkes.
For a late-harvested, and sopotentially risky crop like maize, targeted N rates are extremely worthwhile,she suggests. Making sure there is enough N to grow a good crop, but not toomuch so that crop quality and the environment are compromised has to makesense.