Optimising phosphorus nutrition to power up backward crops


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Ensuring adequate supplies of readily available phosphorus will be key this spring to help maximise the potential of small, backward winter cereal crops.

Crops have been sitting in cold, waterlogged soils for months due to the prolonged wet weather that hit all areas of the UK last autumn.

Shoot and root development has suffered as a result, says Chris Martin, head of soil health at Agrovista. “This season in many wheat crops, it is very much a case of managing tiller numbers upwards rather than down, and ensuring they have an adequate root network to support that growth.

“Plenty of winter barley and oilseed rape crops also need nurturing. We need to supply the right nutrients in an easily accessible form when plants really need them.”

Phosphorus is one of the most important nutrients in crop production due to its role in stimulating early plant growth and development.

Readily available source

“Soil indexes may suggest crops have adequate reserves of phosphate, but it can be quickly locked up on soils with chemical imbalances or unsuitable pH,” says Chris. “Supplying a fresh, readily available phosphate source is key, as traditional soil-applied products such as TSP can be very inefficient, with as little as 10% being recovered by that season’s crop.”

Tests on more than 400 grain samples submitted by Agrovista customers last season revealed that just over 30% had a phosphorus content below the 0.32% guideline, despite receiving traditional phosphate applications.

Chris advises growers to consider applying Luxor and Calfite Extra this spring, just before the peak growth period, prior to or around T0 in cereals and before stem extension in OSR, to promote early growth.

Luxor delivers readily available foliar phosphorus, as well as humic and fulvic acids that stimulate soil biology to maximise nutrient availability. It also contains L-PGA (pidolic acid) to improve nitrogen assimilation within the plant.

Calfite Extra contains calcium phosphite, which ‘tricks’ the plant into reacting as if it were deficient in phosphorus, stimulating root and shoot growth. It also contains L-PGA.

Damage roots

Unium’s commercial manager Andrew Cromie says: “Excessive rainfall in the establishment period of winter cereals is likely to have damaged root systems, reducing the plant’s ability to produce tillers.

“Research shows roots suffer around twice as much as above-ground growth, skewing the root-to-shoot ratio. Correcting the problem early using these products can lead to season-long benefits. A poor damaged root system from this winter will be much more susceptible to drought in the spring/summer.”

Trials carried out last season by manufacturer Unium with Cambridgeshire grower Russell McKenzie used three winter wheat varieties on three different fields, comparing untreated plots, plots treated with 200kg/ha of DAP at the end of February and plots treated with 1 litre/ha of Luxor just before T0.

Yields averaged 11.36t/ha, 12.3t/ha and 12.49t/ha respectively, resulting in a margin over input cost of over £170/ha for the Luxor-treated crops, more than £92/ha ahead of those treated with DAP and producing a return on investment of nearly 15:1.

Russell says: “Our soil P index ranges from +1 to -2. Applying Luxor in place of DAP gave us a consistent result, nearly always improving on the results we were getting from the DAP application.

“We could see where we had applied the Luxor on our NDVI maps. We are now incorporating the product into our commercial programme and I think it will be particularly useful in a year like this, when crops need as much help as they can get.”

Calfite Extra has also produced impressive results. In 2018-2019, in 20 Unium trials it produced an average yield response of 0.75t/ha in winter wheat. Overall, the product has delivered an 8% increase in wheat applied at 0.5 litres/ha at GS 25-30, and an 11% increase in oilseed rape applied at early stem extension at 0.75 litres/ha. This delivered a return on investment of £79/ha and £71/ha respectively over several years of trials.

Combined approach

Applying a combination of both products in the field often produces the greatest effect as their modes are complementary, says Chris.

“In two years of our own trials, we’ve never seen a yield drop, and in the vast majority of cases we’ve seen a significant increase, in addition to typical savings of £70/ha over a traditional phosphate programme.”

young crop