Application of a simple liquid complexing agent this autumn could release 40kg/ha of  locked up phosphate from the soil, reducing fertiliser expenditure and increasing resulting winter wheat yields by up to 1.0t/ha, according to Agrii R&D.

The vital early-season nutrient boosting technology in Agrii-Start Release  encourages better establishment through stronger root formation and could prove invaluable this coming year, believes Agrii National Fertiliser Manager Tom Land.

"Soil health and fertility have taken a hammering in recent months across most parts of the country," he explains.

"If you are on high pH soils, growing a second wheat or maybe drilling later in the year, releasing P from the soil is a super-efficient way to kickstart crops, but it's got advantages for all wheat growers.

"That's particularly the case if you are farming on land with inherently low P indices or have deliberately chosen to take a P and K holiday because of costs in recent years.

"There are signs that such a strategy is not only reducing yields and soil fertility but we are also starting to see declining P levels in grain now and this is directly linked to low N levels in the grain too, so grain quality is starting to suffer.

"We would hope to see grain P levels around 0.32% but 0.25% is increasingly common and where grain P levels are below optimum, this could result in yield loss due to insufficient use of soil P.

Mobilising phosphate

Getting soil phosphate mobilised and absorbed by crops is increasingly important, therefore, but the issue is the majority of P in the soil is in essentially insoluble forms and unavailable to plants, he points out.

"A large proportion of UK agricultural soils are over chalk or limestone and these have high levels of Ca which in turn means they generally have a very high pH and the P contained within them is largely locked up

"Agrii-Start Release is soil applied and works on cations in the soil to displace the phosphate that is locked up, with not only Calcium but also Aluminium and Iron, and keeps this in plant available forms for uptake by plant roots.

"We also know that largest amounts of P are held in the topsoil, typically in the 0-30cm rooting zone, so what we really want to do is increase plant available P at this depth during establishment.

"Agrii-Start Release helps to keep P in a water soluble form that roots can easily access and makes this available for anything up to 120 days, so plants have this vital nutrient early in the growing cycle at a time when they really need it.

"Once those roots have been formed, the plant is in the ideal position to make as much use of future nutrient applications and gives it real resilience to cope with future abiotic stresses and challenging weather conditions.

"Agrii-Start Release also has great relevance to farmers in high P areas who for environmental reasons cannot apply any extra nutrients. The approach can release P from the soils to satisfy crop needs without the need for any applied fertiliser and also helps to manage P levels longer term."

Compelling trial results

Agrii-Start Release has been shown to replace up to 40kg/ha P from applied fertiliser and, depending on pH and the existing P index of the soil, yield responses range from 0.5t/ha to 0.9t/ha in Winter Wheat, Tom Land explains.

"In high P soils at index 4.1 and a relatively neutral pH of 6.9 we've seen yield responses as high as 0.7t/ha and in lower P soils at index 1.1 and a higher pH at 7.9 we've seen yield increases of 0.6t/ha, so that seems to be the range.

"In two years of trials with wheat set at a current price of £180/tonne, the improvements in margin range from around £60/ha to over 120/ha giving a return on investment of £36/ha to £81/ha.

"Plus, don't forget the saving you will be making on applied fertilisers in any one give year and the environmental gains be ensuring P is taken up by crops and not left sitting in soils from where it can potentially leave the system."

For Autumn use in winter wheat, the product can be applied at drilling or emergence at a rate of 4.0l/ha with a water volume of 150 to 200l/ha and can be used effectively with glyphosate and pre-emergence herbicides, Tom Land advises.

"While Agrii-Start Release is best applied during the establishment phase and just prior to a period of active crop growth when seedling and young plant phosphate demand is at its height, Spring applications have proved beneficial in late drilled crops."

Autumn Guidance for Agrii Start Release

• P index 0 - 1 - use bagged phosphate or combination of Agrii-Start Release and bagged phosphate.
• P index 1.0 - 2.0  - use Agrii-Start Release or combination of  Agrii-Start Release and bagged phosphate.
• P index 2 + - consider P holiday but use Agrii-Start Release on high pH soils where P lock up likley.
• P index 3 + - No actual OP recommendation but use Agrii-Start Release on high pH soils where P lock up likely.