|Saporito, Louis - Lou|
Submitted to: Nutrient Cycling in Agroecosystems
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/28/2004
Publication Date: 5/1/2004
Citation: Saporito, L.S., Lanyon, L.E. 2004. Evaluating the spatial and temporal dynamics of field phosphorus and potassium balances on a mixed crop and livestock farm. Nutrient Cycling in Agroecosystems. 69(1):85-94. Interpretive Summary: Nutrient management decisions on farms affect not only the soil nutrient pools but may affect herd health and the environment. Monitoring soil nutrient levels and tracking their movement at different scales can be the foundation for integrating farm activities and information technologies in a new generation of performance enhancing tools. In this study, annual nutrient balances and soil tests were used to determine phosphorus (P) and potassium (K) changes at varying spatial scales from a 120 ha mixed crop and dairy farm in a central Pennsylvania limestone valley for each of nine years. It is evident from this study that combinations of periodic soil tests and annual balances can help producers maintain nutrient stocks in fields before soils become nutrient deficient. In addition, monitoring balances at the farm gate and at the set of all-fields in combination with periodic soil testing over time may allow producers and crop consultants to obetter understand how overall management strategies may lead to nutrient excesses or deficiencies.
Technical Abstract: Methods to track phosphorus (P) and potassium (K) on farms over time at varying spatial scales can improve farm agronomic and environmental performance monitoring. An annual nutrient balance was used to determine P and K balances at varying spatial scales from a 120 ha mixed crop and dairy farm in a central Pennsylvania limestone valley for each of nine years. Alfalfa (Medicago sativa L.) and corn (Zea mays L.) occupied 60% and 34% o the cropland, respectively. Inputs of P and K to the farm exceeded outputs over the study period. Net increases of P and a decrease in K were determined in the aggregate of all fields over the nine year period. The balance of P and K varied with time within a field, and by field within a year, because nutrient inputs and removals of nutrients varied with crop selection and management and year in the rotation. Recognizing that increases in field P are in proportion to P entering the farm can help reduce P accumulation in fields by addressing surpluses at their source or balancing managed flows for the farm. Conversely, decreases in field K associated with forage crops may stimulate K inputs to the farm. Monitoring nutrient stocks (soil testing) and flows (Input/Output balances) at different scales in conjunction with spatial patterns of nutrient balances can be the foundation for integrating farm activities and information technologies in a new generation of performance enhancing tools.