Cropping sequence effects on N fixation and C and N inputs of pea, lentil, and chickpea

  • Chickpeas
  • Lentils
  • Peas
  • Crop Rotation
  • Soil Health
  • Sustainability
  • University of Saskatchewan

Lead Investigator(s)

Dr. Diane Knight

Lead Investigator(s) Institution

University of Saskatchewan - Dept. of Soil Sciences

Objective

To quantify nitrogen (N) fixation of pea, lentil, and chickpea grown in sequence with oilseeds, pulses, and cereals by determining N fixation and pulse residue N inputs (roots, rhizodeposits and aboveground). To determine carbon (C) and N inputs of pea, lentil, and chickpea as they are affected by cropping sequence. To examine the influence of previous crop (oilseed, cereal, or pulse) on soil inputs of pea, lentil, and chickpea. To investigate differences in microbial community structure between the pea, lentil and chickpea and as affected by cropping sequence. To quantify biological N fixation in different pulses in rotations of different diversity in the field.

Outcome

Greenhouse and field studies were conducted to measure and compare amounts of carbon and nitrogen (N) added by different pulse crops (chickpea, pea, and lentil) in different rotation sequences with wheat and brassica crops (canola or mustard) through aboveground residues (leaves, pods, and stems) and belowground residues (roots and rhizodeposits). In this study, growing a brassica crop immediately before the pulse crop reduced productivity, biological N fixation and altered the amount and quality of the rhizodeposits excreted from roots of the next pulse crop in rotation. This in turn affected the composition of the microbial community in the soil the pulse crop was growing in. Differences in C:N ratios of the rhizodeposits affected the rate of decomposition and amounts of C and N in different soil pools. Crops grown in the first year of the three-year rotation also affected the pulse crop grown in the third year of the rotation. Chickpea – wheat – chickpea and lentil – wheat – lentil performed better than chickpea and lentil in pea – wheat – chickpea and pea – wheat – lentil rotations. Cropping sequence did not affect the proportion of C and N originating from above-ground and below-ground residues but had a large affect on the quality of the rhizodeposits, which in turn affected the microbial community and decomposition of these compounds and their stability in different soil pools.

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Agronomy

SPG Contribution

$254,956.10

Project Status

Complete

Duration/Timeline of Project (Year to Year)

2011 - 2014

Co-funders

Saskatchewan Ministry of Agriculture - Agriculture Development Fund