The influence of legume cropping sequences on above and below ground carbon and nitrogen inputs
Pulse crops included in cereal and oilseed crop rotations can provide environmental and economic benefits such as reduced greenhouse gas (GHG) emissions and a reduced dependence on synthetic nitrogen (N) fertilizers. Pulse crop rotations have shown positive impacts on soil nutrient cycling and crop yields due to contributions of bioavailable carbon (C) and N to soils. Pulse crops in symbiosis with rhizobia can input N to soils from atmospheric N fixation. Soil C inputs are derived from aboveground crop residue inputs and below ground root exudates. Stable isotope (13C and 15N) methodologies are being utilized to quantify above and belowground contributions (roots and rhizodeposits) of both C and N inputs from chickpea, pea and lentil residues to soil. 15N is introduced into the stem of plants using a stem feeding technique (stem wick method). 13C is introduced using atmospheric pulse 13CO2 labeling. The more precise nutrient budgets can be used to determine the best pulse crop rotations to improve GHG budgets, reduce farmer dependence on N fertilizers and therefore improve environmental and economic sustainability of the system. Preliminary results will be discussed.
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