Tuesday, November 6, 2007
194-1
Does Lentil Fix Nitrogen for the Succeeding Crop in Rotation?.
Including pulse crops in rotations increases soil Nitrogen (N). Either higher rates of fixed N (%Ndfa) or lower rates of harvested N in seed (%NHI) produce positive “N incrimination (Ninc)” in soil. Lentil obtains most of its N from nitrogen fixation; however wide ranges of positive to negative N balances have been reported for %Ndfa and %NHI in lentil. The effects of three fertilities (seed inoculation, 50 kg ha-1 N and no N- no inoculation called ‘50N’, ‘Inoc’ and ‘Control’, respectively) were tested for %Ndfa, %Ninc and %NHI and dry weight plant %N of lentil in zero-tillage soil with a previous history of legumes. Nitrogen incrimination was calculated by subtracting the %NHI from %Ndfa and %NHI was obtained from seed N/plant N. Results showed a non- significant positive effect of inoculation on %Ninc, plants fixed 2.1% more than the amount of N translocated to seed; Control and 50N produced 0.5 and – 0.17 %Ninc. The highest rate of nitrogen was fixed by the Inoc (78%); 50N and Control fixed 66 and 64% N, respectively; N treatment did not reduce %Ndfa compared to the Control. Similar %NHI was also measured among the treatments (72, 68 and 64 for 50N, Inoc and Control, respectively). Plant N concentration was significantly affected by treatments, ranging from 1.9 to to1.6% N. Although root N exudation can not be accounted by this method, results showed that including lentil to Dark brown soils of Saskatchewan rotation did not deplete soil N.
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