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This article in AJ

  1. Vol. 72 No. 3, p. 525-527
    Received: Apr 16, 1978

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Stand Thinning in Seed Production of ‘Cougar’ Kentucky Bluegrass1

  1. David W. Evans2



Kentucky bluegrass (Poa pratensis L.) seed production typically decreases as the stand ages. Eliminating or reducing this decrease would greatly benefit growers. In earlier research, stand thinning by gapping (removing sections of sad from the row) increased Kentucky bluegrass seed yield for one season where stands were fertilized with low to moderate rates of N. The present study was conducted to determine the effects of single and repeated gapping on seed yield, seed yield components, and the age-associated seed yield decline in Kentucky bluegrass fertilized with different rates of N.

‘Cougar’ Kentucky bluegrass was grown in rows under sprinkler irrigation and fertilized yearly with 100, 200, or 300 kg N/ha. Alternate 23-cm sections of the row were removed after harvest in 2 consecutive years, in the 1st year only and in the 2nd year only. Also, alternate 23-cm sections of ungapped rows were clipped for 2 consecutive years to remove panicles at panicle emergence.

Gapping increased seed weight per panicle by 12% the 1st year and panicles per meter of row and seed yield by up to 39 and 32%, respectively, the 2nd year. Repeated gapping was as effective as first-time gapping in either year. Clipping, while it decreased panicle numbers and seed yield, increased seed weight per panicle by 20% or more each year and 1,000-seed weight by 5 to 8%. Seed production was highest for 200 kg N/ha in 1969 and 1970 and for 100 kg N/ha in 1971. Nitrogen rates did not affect gapping or clipping responses.

Density of panicle production within the bluegrass sod was the principal factor affected by gapping. Gapping consistently increased panicle density. Density was increased as much by repeated as by first-time gapping.

Results of the study indicate that appropriate sod management can increase seed yield and reduce the rate of age-associated seed yield decline.

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