Greater precision is essential in crop nutrition these days to make the most of modern high cost production systems, growers were advised at a specialist SMART Farming meeting this week (Wednesday November 9). What is more, it needs to be planned early and with as much flexibility as possible to cater for very much more uncertain growing seasons.

Speaking at the company’s AgriFocus trial site near Marlborough, Masstock technical support manager, David Langton pointed out that with most combinable crops costing in excess of £1000/ha to produce these days, the cost of failure is fast becoming prohibitive. At the same time, increasingly frequent and less predictable extremes of weather are significantly adding to this risk.

“More than anything else, output drives crop profitability,” he stressed. “And, in turn, nutrition drives output. So it isn’t surprising that Masstock Farm Consultancy budgets for 2011/12 show fertilisers as the single biggest variable cost of almost every crop, with the possible exception of pulses.

“The vital importance of fertilisers and the fact that they typically account for around 50% of crop variable costs makes it essential to get fertilisation spot on, both in the individual nutrients supplied and their timing. Several dry springs in a row have really underlined this as far as  micro-nutrients like magnesium are concerned, not to mention nitrogen.

“Our whole emphasis in modern crop nutrition must be on avoiding limiting factors. Plants need a balance of different nutrients for the most efficient functioning. Their demand for these nutrients varies both with growth stage and with their uptake of other nutrients – particularly nitrogen. Equally, the availability of nutrients to plants depends on soil conditions like pH, soil moisture levels, root mass and nutrient interactions. These factors all need to be taken into account in planning soil and foliar fertiliser applications to deliver the greatest crop value.”

So, how can this best be done ? Well David Langton has no doubt that the first fundamental has to be broad spectrum soil analyses to identify critical limiting factors which can vary widely within as much as between fields.

As well as P, K and pH, these should include magnesium, copper, zinc, molybdenum, and boron (mainly for oilseed rape). The analyses should, further, be undertaken well ahead of the spring to enable fertiliser programmes to be optimised from the start of the new growing season. 

For the dynamic element nitrogen, he advises a different strategy involving an accurate soil mineral nitrogen assessment in early spring as the basis for application planning.

“Professional interpretation of laboratory results with an experienced agronomist is as vital as good sampling and analysis practice in both these respects,” David Langton insisted. “Mainly because you need to take account of  all the key factors governing nutrient availability together with specific crop requirements and the extent to which they will alter with yield to get the nutritional balance right.

“Getting the balance of even apparently minor nutrients wrong can seriously limit the crop’s ability to utilise nitrogen correctly and, as a direct result, its performance. Especially so where high yields are being sought in the face of particular environmental stresses.

“It’s also important to appreciate that the best solution for any crop and season won’t necessarily be extra fertilisation,” he warned. “With a good micro-nutrient dressing costing less than 10% of a typical crop’s nitrogen spend, it can be highly cost effective.  Indeed, where nitrogen uptake is restricted by lack of soil moisture it can have a dramatic effect on crop performance. But equally valuable may be an early season application of Nutriphite PGA at under £10/ha to stimulate root growth.

“Overall, a programmed approach is the most important fundamental for success. Understand your crops and the key nutritional risk factors posed by your particular soils. Plan to achieve the best nitrogen fertilisation balance early enough in the spring to take advantage of sufficient soil moisture. And keep on top of events by tweaking your nutrition with the season as it develops.  

“After all, this is the sort of precision most growers already employ in their disease management which, most agronomists would agree, is very much less critical to final crop performance and profitability than nutrition.”