USING SPATIAL ANALYSIS TO OPTIMIZE CONTINUOUS FIELD MANURE APPLICATIONS WITHOUT ADVERSE ENVIRONMENTAL IMPACT 1 2 3 4 5 6

ABSTRACT. Manure applications can enhance phosphorus (P) contamination of nearby waters. Erosion related P contamination is due to runoff water and eroding sediment carrying dissolved and particulate P, respectively. Environmental conditions, soil properties and management affect soil erosion, but minimizing P loss requires considering other factors (rate, method, timing of manure application; soil test P level). As a result, new indices have been proposed to guide animal waste application. The Kentucky Phosphorus Index (KPI) is designed for “field-average ” assessment of P loss vulnerability. The KPI may not represent all parts of the field equally well. Our objective was to assess spatial variation in the KPI due to differences in: I) hydrologic soil grouping, II) soil test phosphorus (STP), and III) slope. Two fields (112, 950) were chosen. Field 112 had been fertilized, while 950 had a history of both fertilizer and manure application. Soils were largely well-drained, but areas with a fragipan were found in both fields. Slopes ranged from 0 to 7%. STP values ranged from 15 to 330. KPI values ranged from 52 to 61, causing in-field areas to be classified as “medium ” or “high ” in P loss vulnerability. Spatial analysis showed that these fields should not be subjected to uniform manure and/or chemical fertilizer management in order to minimize P loss while maximizing manure application longevity