Agrovista UK is exploring different feeding techniques to help top- and soft-fruit plants acquire phosphorous (P) and other elements such as manganese, iron, copper and zinc from the soil.

Global P reserves are being depleted rapidly, with the result that market prices are rocketing. Most of the P applied in conventional fertilisers may be absorbed by the soil, and then not available to plants it was meant to feed. Phosphorous is also a non-renewable resource, like nitrogen.

When phosphorous is applied as fertiliser, 80 to 90 per cent of the application is absorbed by the soil particles, rendering it unavailable for most plants. It is also highly immobile in the soil.

James Dick, fruit specialist at Agrovista UK, said: “We have looked at other ways of increasing P delivery to the roots, namely encouraging root proliferation and mycorrhizal symbioses with the roots. Then we needed to promote root absorption by increasing the P concentration in the soil by releasing it from complex or organic forms. This can be achieved by spraying the crop with Odyssey, a phosphonate-based product applied during the period of rapid vegetative growth. We are used to seeing phosphorous, manganese, iron, copper and zinc deficiencies during this phase in many crops.”

The Phosphite triggers a P-starvation response in the plant. P-starvation responses include increased root growth, enhanced root hair formation and enhanced excretion of organic acids by the roots. The new growth will naturally increase P delivery to the plant. The organic acids cause localised acidification of the rhizosphere that not only mobilises P but also iron, manganese and zinc. This in turn increases their uptake and concentration within the crop. The root exudates also provide a food source and therefore encourage mycorrhizae within the rooting zone.

Mycorrhiza can improve plant acquisition of other soil-based mineral elements that are not readily available in high clay-content soils (for example vertisols) where high pH can also be an issue.

Currently, there are several commercial products that contain phosphonate (for example, phosphite, the salt of phosphorous acid), but Agrovista warns that there are differences. Odyssey is manufactured in Germany to the highest quality and formulation using highly refined ingredients. This exacting process ensures Odyssey contains no contaminants harmful to either the plant or consumers of the crop.

Dick stressed that some cheaper sources of phosphonates can contain heavy metals like cadmium and growers should be cautious when purchasing phosphites. “Always ensure that you source a quality product and get good advice on application timing and rates," he said. Using this technique along with nutrition sampling will allow for higher yields and quality, as well as relieving crop stress at critical times of the year.”

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