Adopting a prescription nutrition approach to wheat has allowed a Worcestershire grower to cut back fungicide and nitrogen inputs.

Fertiliser advice has generally been oversimplified and has distorted the truth about crop nutrition, leaving many cereal crops in intensive care, says a crop nutritionist.

“There’s a perception that anything you spray on or spread is sure to be available to the crop, but we know that many nutrients are quickly lost through leaching or locked up by others,” says Steve Townsend of Soil First Farming, based in Gloucestershire. “Applying nitrogen fertiliser to increase yield is only cost-effective if everything else is correctly balanced.”

Mr Townsend urges growers to adopt a policy of “prescription nutrition” to benefit from more consistent yield and quality along with considerable reductions in disease severity. The reason fungi are then less of a threat is that nitrogen is being fully utilised by the crop and, thus, there are few free amino acids available for fungal growth.

“When the soil biology and chemistry are right for a particular crop, not only can fungicides safely be reduced, but it is possible to omit up to 20% of the usual N fertiliser rate and still obtain the same yield,” he suggests.

Among the most commonly deficient macro/micronutrients – magnesium, sulphur and manganese – sulphur is probably the least well understood. Mr Townsend stresses that supplying sulphur rather than nitrogen at the right time is the key to high quality.

But it isn’t just deficiencies that cause loss of potential. Excesses can create imbalances, for example, soil magnesium can lock up potassium, which has a knock-on effect on the efficiency of nitrogen fertiliser use and bulk yield, he warns.

“The truth is, chlorophyll is what arable growers are really farming in the process of photosynthesis, and magnesium is central to its production. But having a high soil level is useless, indeed damaging, since it is not in a form the plants can use very well.

“Growers applying bitters salts, such as Epsom salts or magnesium sulphate, may not be getting enough in. If only they knew that for the same price, they could buy chelated or liquid magnesium.”

It’s important to work through what each and every crop needs and what it doesn’t need, using the law of maximum as well as the law of minimum, he concludes.

CASE STUDY: Jim Bullock

Prescription nutrition is the most exciting thing Jim Bullock has introduced at Mill Farm since converting to min-till and direct drilling 12 years ago.

His Worcestershire clay loam soil, with its unusually high magnesium level, is benefitting from additional micronutrients in the form of Maxi-Phi products.

Mr Townsend devised a programme for Mr Bullock, similar to one that gave a 5% yield advantage over the control in his trials, to test across three tramlines in adjacent fields of Solstice wheat last year. The Maxi-Phi treatments were selected following soil and leaf nutrient analyses carried out by an independent laboratory, and the decision made to withhold all fungicides where they were used.

Tests showed magnesium to be at soil index 6, however Maxi-Phi Hi-Mag was used at timings corresponding to T1, T2, and T3 to raise levels in the leaves and thus improve the uptake of nitrogen fertiliser. Phosphate uptake was also expected to be compromised, so three liquid applications were given, as Activate MP.

Maxi-Phi Manganese was also used at T1, T2 and T3, whereas usually it would only be applied once or twice early in the spring. Zinc and sulphur formulations were also included where necessary, to lift protein.

The most remarkable effect of the micronutrient programme was on quality, specifically protein content (on average 1.2% up on the control), but also Hagberg (on average 36 up on the control). On top of that, though he didn’t measure yield, Mr Bullock felt the Maxi-Phi treated areas produced as much if not more grain a hectare than the surrounding wheat fields.

Although a low disease pressure year generally, “the crop never looked stressed bearing in mind that no fungicides were used”. Overall, the treatment input cost of £33.60/ha was considered reasonable in the light of the greater returns and savings on fungicides.

“Having seen the results for myself, I’m planning to use the micronutrient programme more widely based on Steve’s recommendations. I won’t use fungicides unless I have to, and I may try cutting back on my current nitrogen fertiliser use.”