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This article in AJ

  1. Vol. 67 No. 4, p. 533-537
     
    Received: Oct 9, 1974


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doi:10.2134/agronj1975.00021962006700040020x

Optimum Size of Sampling Unit to Estimate Coastal Bermudagrass Yield1

  1. H. Soplin,
  2. H. D. Gross and
  3. J. O. Rawlings2

Abstract

Abstract

Because the field-plot techniques used on ‘Coastal’ bermudagrass [Cynodon dactylon (L.) Pers.] have been empirically transferred from temperate species research, our objective was to define an optimum sampling-unit size for this species. Optimum size of sampling unit was evaluated under six managements: three heights of available forage (avg. 3.75, 7.50, and 11.25 cm), each maintained by grazing or clipping. Three samplings were made on each treatment, corresponding to early, mid, and late-summer harvest dates. The basic sampling unit was a 20-cm square.

Plots more nearly square and those perpendicular to the slope gave larger estimates of variance than plots that were parallel to the slope and rectangular. Variance of yield/unit area arranged over plot size-harvesting date combinations increased with height of available forage.

Three weighted coefficients of the logarithm of variance of mean yield by heights, regressed on the logarithm of plot size, were computed. Optimum size of sampling unit, regardless of treatment, was found to be not greater than 20 ✕ 20 cm for a cost function based on hand clipping. Assuming costs associated with mechanized harvest, optimum size was found to be 16, 15, or 10 units in size (respective to the three heights) with thelonger dimension parallel to the slope.

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