Current University of Wisconsin-Extension guidelines recommend 60 lb-N/ac for snap bean grown on soils less than 2% organic matter, which are most soils in the Central Sands of Wisconsin. However, the typical rate that snap bean growers apply is much greater than this rate. In addition, it is possible that rates lower than 60 lb-N/ac may be economically optimal for some varieties. Snap beans are a legume and some, but not all, varieties nodulate, meaning they have the ability to fix nitrogen (N) from the atmosphere. This will result in different N response curves and perhaps different N recommendations for different snap bean varieties. It is often assumed that when we fertilize legumes with N, the added N replaces the amount of fixed N in a one-to-one manner – but this is rarely true. In fact, we know little about the tradeoffs between N application and nodulation in snap beans. The objectives of this paper are to review the state of knowledge of snap bean response to N fertilizer and evaluate the different ways nitrogen use efficiency can be determined.
Soil Science Extension
University of Wisconsin Madison