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Research indicates crop-available legacy phosphorus could fertilize crops while saving farmers money

Researchers at the University of Florida Institute of Food and Agricultural Sciences (UF/IFSAS) report soil legacy phosphorus could be enough to fertilize crops – at least for a planting season or two. Using the abundance of this common fertilizer already in their fields would save farmers from applying more. It would also improve their bottom line in the short-term.

“Our study showed, in some acidic soils with negative soil phosphorus storage capacity (SPSC), crops could draw out the nutrient already in the soil,” said Vimala Nair, a research professor of environmental soil chemistry with the UF/IFAS Soil and Water Sciences Department. Negative SPSC suggests phosphorus is available for plant uptake.

The Research

The group planted rye, silage corn, and forage sorghum in succession during a two-year period. This was done at three sites in Florida. However, their article published in the journal Agrosystems, Geosciences & Environment focuses on corn production. The corn crop had the greatest yields and removed the greatest amount of phosphorus.

“As a vital resource, this legacy phosphorus, which has accumulated over the years, could be ‘mined’ by crops,” Nair said, “but only to the point at which there is adequate phosphorus in the soil for optimum crop yields.”

Drawing down this existing phosphorus would have two benefits. First, it would save farmers on the cost of phosphorus fertilizer. The price of phosphorus is expected to increase, as supplies of the limited natural resource are depleted. Reducing phosphorus in the soil also improves the environment. Excess amounts in the soil due to repeated fertilizer applications increase the potential for its loss from the soil and eutrophication of adjacent and downstream water bodies. Eutrophication results in the decrease of oxygen in the water causing the death of many aquatic organisms, such as fish, which need oxygen for survival.

The Results

Nair says the early results are promising, but they need to study it further.

“We have to determine more precisely the negative phosphorus thresholds – the lowest absolute value – at which phosphorus mining would no longer be adequate to avoid a deficiency in the crop,” she explained.

Researchers from the UF/IFAS Agronomy Department and the Department of Crop Soil and Environmental Sciences at the University of Arkansas participated in this study. You can read the full journal article at https://acsess.onlinelibrary.wiley.com/doi/full/10.1002/agg2.20056