Nitrogen Economy of Pulse Crop Production in the Northern Great Plains

Abstract

Previously published data were used to examine the N economy of pulse crops typically grown on the Northern Great Plains with the goal of assessing the potential contribution of field pea ( Pisum sativum L.), lentil ( Lens culinari s Medik.), chickpea ( Cicer arietinum L.), common bean ( Phaseolus vulgaris L.), and faba bean ( Vicia faba L.) to soil N accretion. Incremental changes in soil N associated with the pulse crops (i.e., the nitrogen increment, N inc ), were strongly correlated to N 2 fixation and were highly variable. Data suggest that crops that can achieve relatively high levels of N 2 fixation, such as faba bean, field pea, and lentil are more likely to contribute positively to the overall N economy, particularly when a cropping system is evaluated over a long term. In contrast, pulse crops that typically achieve only modest levels of N 2 fixation such as desi and kabuli chickpea and common bean are more likely to be either N neutral or contribute to a soil N deficit. Because of extreme variability in levels of N 2 fixation achieved, presumably reflecting variability in soil productivity as well as variations in local climate and weather, the N inc of pulse crops likewise is highly variable. Thus, the N contribution to a subsequent crop is difficult to predict with any certainty, particularly on a yearly or short‐term basis.