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Effects of rates and times of application of starter dressings of nitrogen fertilizer to surface sown perennial ryegrass‐white clover on hill peat
Author(s) -
HAYSTEAD A.,
MARRIOTT CAROL
Publication year - 1979
Publication title -
grass and forage science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.716
H-Index - 56
eISSN - 1365-2494
pISSN - 0142-5242
DOI - 10.1111/j.1365-2494.1979.tb01476.x
Subject(s) - sowing , agronomy , perennial plant , field experiment , nitrogen , trifolium repens , fertilizer , lolium multiflorum , biology , chemistry , organic chemistry
The effects on clover and grass growth of five levels of ammonium nitrogen (NH 4 ‐N) applied before sowing, at sowing and after nodule initiation have been investigated. A pot experiment in which S184 white clover was grown in a peat soil showed that NH 4 ‐N up to 688 mg N per pot (approx. equivalent to a field rate of 120 kg ha ‐1 N) applied before sowing and at sowing did not affect clover growth. N‐fixing activity (C 2 H 2 ‐reduction), on the other hand, was reduced progressively up to the highest level (688 mg N per pot). Application after nodule initiation increased growth relative to the zero‐N treatment at all levels of application. Maximum growth and N fixation occurred at 516 mg N per pot where the DM yield was 70% higher than in the absence of added N. A field trial in which S184 clover and S24 perennial ryegrass were surface sown on to a peat soil showed an increase in grass and clover growth in the first year in response to 120 kg ha ‐1 N applied at sowing. Grass growth alone was increased at 120 kg ha ‐1 N applied 40 d before sowing. Lower rates of application before sowing and at sowing did not affect clover or grass growth. The effect of the delayed application of NH 4 ‐N on legume growth was less marked than that in the pot experiment, 90 kg ha ‐1 N stimulating clover growth by 40% in the first year. The effect was however different from that in the pot experiment, in that, whilst 30kg ha ‐1 N increased N fixation relative to the zero‐N treatment, plants exposed to higher levels showed a depression in N‐fixing capacity. N‐fixation was correlated with nodule numbers in the delayed NH 4 ‐N application, the closest correlation being with the number of multilobed nodules which was highest at 30 kg ha ‐1 N and lowest at 120 kg ha ‐1 N. It is suggested that circumstances exist when the use of a relatively low starter N dressing (20–60 kg ha ‐1 N) at sowing would not increase clover or grass growth in the early stages of the establishment of a hill reseed. Under such circumstances higher rates of application (100 kg ha ‐1 N), preferably delayed until the seedlings are in a position to take up the nitrogen rapidly, would have the greatest effect.