Managing Legacy Soil Phosphorus to Sustain Agriculture and Protect Water Quality

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Title: Managing Legacy Soil Phosphorus to Sustain Agriculture and Protect Water Quality
Authors: Sims, J.T.
Murphy, Paul
Wall, David
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Date: 9-Sep-2013
Online since: 2019-05-20T08:20:27Z
Abstract: A central tenet of modern nutrient management planning is the need to maintain soil phosphorus (P) in a range that optimizes crop production and protects water quality. Decades of research have identified the soil test P (STP) critical values needed for economically optimum crop yields, leading to well-established recommendations for efficient use of inorganic and organic P sources as soil amendments. However, in many areas of the USA and other countries, long-term over-application of animal manures and fertilizers has led to soil P accumulations to values that are considerably above agronomic optima and of concern for surface water quality. These soil P accumulations are a legacy of historically inefficient P management and present serious challenges to our efforts today to prevent nonpoint P pollution of surface waters. The fundamental issue identified in most research has been that it can take years, even decades, to decrease soil P values from “excessive” to “optimum”. Thus, even if P inputs to “high P” soils are restricted or eliminated, environmentally significant P losses to water may continue. For example, in Delaware, statewide summaries show ~60% of soils tested have STP values more than twice the critical value (~30 mg P kg-1 , Mehlich 3); in the intensive poultry producing regions, >30% of soils have STP values more than six times the critical value. A recent long-term (11 yr) cropping (corn-soy) study we conducted at two sites with initial Mehlich 3 P values of 98 and 70 mg kg-1 found that ceasing P applications decreased STP by 43% and 27%, with no negative effects on crop yields, providing guidance for emerging strategies for management of “high P” soils. Although similar long-term studies are somewhat rare, we have analyzed the findings of > 25 studies from the US and Europe investigating the relationship between P management, cropping system, and changes in amount and form of P in “high P” soils. Our presentation summarizes the findings of long-term P depletion studies in Delaware and our quantitative analyses of similar studies conducted in settings varying in initial STP, soil type, cropping system, and climate. We present strategies and policies to address the “legacy” P issue in overfertilized soils, toward a goal of sustaining soil P values in ranges optimum for crop production and protection of water quality.
Type of material: Conference Publication
Keywords: Nutrient management planningSoil phosphorusCrop productionPhosphorus pollutionWater quality
Language: en
Status of Item: Not peer reviewed
Conference Details: The 7th International Phosphorus Workshop (IPW7), Uppsala, Sweden, 9-13 September 2013
ISBN: 978-91-576-9162-0
Appears in Collections:Agriculture and Food Science Research Collection

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