As market prices for phosphate and potash fertilisers fall to their lowest for nearly four years growers are being urged to take advantage of the opportunity to restore soil reserves.

Openfield, Britain’s leading grain and inputs co-operative, says prices for diammonium phosphate (DAP), triple superphosphate (TSP) and murate of potash (MOP) are at their lowest level since the New Year of 2010.

“Phosphate (P) and potash (K) markets have seen significant price falls over the past 12 months and are currently trading near to the lows of 2009-10 due to lack of recent demand,” says Openfield fertiliser manager for the south of England, Adam Thwaites.

“For those who have taken a P and K holiday in recent years, the current prices represent a good opportunity to redress the balance and avoid depleting soil reserves further,” he adds.

He cites the recent Soil Nutrient Status summary for 2012-13 from NRM Laboratories which found that a significant proportion of arable and forage soils from across the UK were below the target index 2.

“The results are quite telling with more than a fifth of the soil samples tested for phosphorus and magnesium below target index 2 and almost a third of soils tested for potassium below target index 2-.  Restoring these soils to the target levels, particularly in the case of potash in clay soils, can take up to 10 years so now is a good time to start,” says Mr Thwaites.

In addition to ensuring sufficient nutrient availability to meet plant needs, maintaining soil indices for potash at the target indices of 2 or 2+ also bolsters a soil’s ability to retain other nutrients during periods of extreme weather.  “K fulfils a vital holding role. Maintaining target indices is the best way to ensure the soil retains the ability to buffer the effects of adverse weather as deficient soils tend to suffer from reduced nutrient availability,” he says.

“Equally, it’s important not to overreact in periods of poor weather. Remember, phosphate and potash do not leach. While some soil types are more vulnerable to the effects of extreme weather there are others, such as clays, that release K into the available ‘pool’,” he says.

Mr Thwaites also warns of the need to test soil pH, particularly after a period of prolonged wet weather, and correct any imbalances in order to ensure nutrient availability is not adversely affected.

“Heavy rain can acidify soils through the increased leaching of nitrates, sulphur and other mobile nutrients and this is more likely to have an adverse effect on pH than indices levels. Restoring the pH of previously waterlogged soils will improve nutrient availability so pH testing and liming should be considered vital after periods of extreme wet weather,” he says.