Processing Snap Bean Variety Responses to Applied Nitrogen and Irrigation in the North Central United States

Irrigated processing snap bean (Phaseolus vulgaris L.) production in Wisconsin, mostly in the central sands region, ranks first in both yield and harvested hectarage in the U.S. However, there is little information assessing N need across processing snap bean varieties under different irrigation strategies on sandy soils. The objective of this study was to determine the effects of N rate and irrigation on yield, pod quality, and other agronomic traits across different varieties with known differences in nodulation. Results indicated that nodulating varieties such as DMC04-95 consistently produced higher yields than the non-nodulating variety Huntington by 3.5 to 4.3 Mg ha–¹. Yield and pod quality responses to in-season supplemental N fertilizer at the rates of 0 to 135 kg ha–¹ varied across varieties. In each year, Huntington responded the most to N fertilizer, and had the lowest harvest index and the poorest pod quality. Reduced irrigation on sandy soils did not significantly reduce yield and pod quality when applied in minimal quantities sufficient to avoid permanent drought stress during blossom and pod set. Across years, the optimal in-season N rate was 90 kg N ha–¹. This, together with the 22 kg N ha–¹ applied as starter fertilizer, suggests 112 kg N ha–¹ is the optimal N rate for irrigated snap beans on sandy soils in the central sands region of Wisconsin. This rate is greater than recommended from previous studies conducted in other soil types, and may be warranted only when high yielding varieties are grown.