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 culinaris 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, Ninc), 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 Ninc 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.

Underestimated role of legume roots for soil N fertility

“…High air temperature increases root and nodule decomposition and mineralization rate in soil; then, the recovered material at harvest was probably lesser under the present field conditions than in controlled environments, since the rhizodeposition was not taken into account. We emphasize that our values are much lower than those 22-68 % reported in the studies of Walley et al (2007), Fuhrer (2004, Fustec et al (2010), Mathieu et al (2007), McNeill andFillery (2008), Griffiths (2009), andYasmin et al (2006) which included the rhizodeposits that represented more than 7 %.…”

“…Estimates for both lupine species (7-9 %) were smaller than the values (13-14 %) quantified by Unkovich et al (1997) and Walley et al (2007) for lupine roots under the field condition. However, they were in the range of values (9-12 %) reported by Fillery and McNeill (2001) for Lupinus angustifolius L. The value determined in the present pasture legume (11 %) is also within the last range, but is smaller than the estimate of 12.6 % reported by Huss-Danell et al (2007) for the red clover in a mixed stand under rainy conditions and even smaller than the range of values (17-24 %) reported by McNeill et al (1997) for subclover grown in intact cores of soil-plant systems.…”

“…Plant N from symbiotic fixation of atmospheric N 2 is added to the ecosystem mainly via the decomposition of legume parts or via urine and feces from grazing animals in pastures. In addition, rhizodeposition, i.e., exudates and products of root and nodule necrosis, may also add N to the soil (Fustec et al 2010;Herridge et al 2008;Huss-Danell et al 2007;Høgh-Jensen and Schjoerring 2000;Walley et al 2007). Thus, N 2 -fixing plants can make important contributions to increase the sustainability of agricultural ecosystems by reducing the use of energetically costly mineral N fertilizers.…”

“…Most methods of quantifying belowground biomass require a considerable labor and time investment. Recently, Walley et al (2007) assumed that root and rhizodeposited N was respectively 14 and 10 % of total plant N when calculating N 2 fixation by pulse legumes in the Northern Great Plains of North America.…”

Legume, cropping intensity, and N-fertilization effects on soil attributes and processes from an eight-year-old semiarid wheat system

“…Longer-term studies suggest that N-benefits to wheat may be realized only after multiple years of legumes in rotation (Campbell et al 1992;Zentner et al 2004;Walley et al 2007;Allen et al 2011). This delayed response may be a reality of cool, waterlimited conditions in the NGP leading to low annual legume biomass contributions, slow breakdown of residues, and subsequent slow release of available N (Janzen et al 1990;Bremer and van Kessel 1992;Beckie et al 1997), especially in no-till systems (Schoenau and Campbell 1996;Triplett and Dick 2008).…”