Soil Test Interpretations for Iowa High Ph Soils
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The Iowa State University Integrated Crop Management Conference is Iowa's premier crop production education event. No other program in Iowa brings together the diverse range of topics, slate of expert presenters and results of the latest University research.
The ICM Conference offers workshops focusing on the latest in crop production technology. Experts from Iowa and surrounding states will provide research updates and results in soil fertility, soil and water management, crop production and pest management.
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Abstract
A variety of soil tests are reliable for evaluating plant available phosphorus (P) of neutral or acid soils but there is still uncertainty about appropriate soil tests and soil-test interpretations for calcareous soils. The Bray-PI is the most widely used soil-test P method by soil testing laboratories operating in Iowa, although many also offer the Olsen method. Extensive research has shown that the Bray-PI test is reliable on neutral or acid soils but that it tends to underestimate available P on many calcareous soils. The Olsen test seems more reliable for calcareous soils. Because of this problem, many soil testing laboratories base fertilizer recommendations on one or the other method depending on the pH of the sample.