More recently, with emphasis on sustainable crop production, there are a number of tests that assess soil health. Some of the soil health tests such as the Haney Soil Health Tool (HSHT), which is adopted by USDA-NRCS, assess soil quality parameters as well as nutrient availability. The HSHT uses the H3A-4 extractant to estimate ‘plant available’ nutrients. The H3A-4 extractant simulates plant root environment by using organic acid plant exudates and has been touted as more representative of phosphorus availability. Some commercial soil testing laboratories offer HSHT and provide corresponding fertilizer recommendations. How does the test values and recommendations from H3A-4 relate to Mehlich-3 extraction? Publicly available information relating H3A-4 to Mehlich-3 extractable nutrients is limited. Continue reading →