Are we overfertilizing our fields? Researchers challenge conventional soil testing

A new study led by Dr. Shikma Zaarur of the Hebrew University of Jerusalem has found that agricultural soils may contain a previously unaccounted-for reservoir of potassium, an essential nutrient for plant growth. This discovery challenges conventional soil testing methods, which often underestimate the potassium available to crops.

The research, published in the journal Plant and Soil, suggests that potassium fertilization strategies could be revised using this new understanding of soil potassium dynamics. The study found that despite conventional soil tests underestimating potassium availability, plants absorbed significantly more potassium than expected, with 50% to 74% of the potassium taken up by plants originating from non-exchangeable soil reserves.

The research, conducted over 13 months using three agricultural soil types common in Israel's Mediterranean environment, revealed that potassium levels in clay-rich soil were largely maintained by natural mineral reserves, while red sandy soils benefited from potassium fertilization. The findings highlight the importance of considering soil mineral composition in fertilizer recommendations, particularly for Mediterranean agriculture where alkaline soils are prevalent and efficient fertilizer management is crucial.