Livestock and arable farmers alike look set to benefit from the launch of a new service for maize growers to measure soil nitrogen. The new N-Min for maize soil test from fertiliser manufacturer, GrowHow UK, is an extension of the well-established service for cereals and oilseed rape. Uniquely it provides an accurate assessment of the total amount of nitrogen the crop will be able to get from the soil over the full growing season.
Maize has become a staple forage crop for many livestock enterprises and with more and more arable farmers beginning to grow it as a biofuel, this introduction is very timely.
N-Min measures both the amount of nitrogen in the soil at the time the sample was taken (the SMN – Soil Mineral Nitrogen) and the Additionally Available Nitrogen (AAN), which is the amount of N that will become available through mineralisation – the turnover of organic N to make plant available N. In this way it allows farmers and their fertiliser advisers to calculate whether any additional nitrogen is required to allow the crop to achieve its optimum yield potential. GrowHow’s N-Calc system has also been updated to include maize so that N-Min results can readily be converted into field recommendations.
On-farm trials over the past five years have shown that the N-Min service can be extended successfully to maize cropping. The trials were conducted across a variety of different regimes – from the traditional dairying scenario, with regular muck use, to rotational sites on mixed or livestock farms with less manure applied and, more recently, to growers on arable units who are diversifying their cropping into energy crops for biogas production in anaerobic digestion plants.
Across the farms and the years of the trials work, the N-Min measured ‘N reservoir’ – or N that will be available to the crop over the growing season – varied widely. The values ranged from less than 55 to over 500 kg N/ha.
“It was interesting that whilst the lowest 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 highest ones always from sites which had received organic material of some kind,” notes GrowHow’s Grassland Specialist, Elaine Jewkes.
“For a late-harvested, and so potentially 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 too much so that crop quality and the environment are compromised has to make sense.”