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This article in CS

  1. Vol. 31 No. 6, p. 1459-1464
     
    Received: Oct 9, 1990


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doi:10.2135/cropsci1991.0011183X003100060013x

Predicted and Actual Yield and Nitrogen Concentration of Alfalfa in Different Nitrogen Environments

  1. L. R. Teuber ,
  2. D. A. Phillips,
  3. S. Geng and
  4. W. F. Lehman
  1. Univ. of California, Imperial Valley Agric. Res. and Ext. Ctr., El Centro, CA 92243.

Abstract

Abstract

Glasshouse studies with alfalfa (Medicago sativa L.) have shown that improving both forage dry weight (DW) and N concentration (NC) requires selection under N2- and NH4NO3-dependent conditions. The objectives of the present study were to (i) determine genetic variances of forage DW and NC in the field under different levels of N fertilization, (ii) use the genetic variances to predict selection gain for DW and NC at each level of N, (iii) select for increased DW and NC under field conditions and compare actual gains with predicted values, and (iv) compare the efficiencies of field and glasshouse selections for DW and NC. Twenty-five randomly chosen half-sib families from ‘Moapa 69’ were planted in each of 2 yr at four locations using a split-plot design with four levels of N fertilizer (0, 33, 66,100 kg N ha-1). Forage DW and NC of plants were measured at each location, and individual plants were selected at one location for both DW and NC in each N level using independent culling levels. Genetic variance and predicted gain per cycle for DW were maximized with 100 kg N ha-1 (118 g kg-1), while those for NC were greatest without N fertilizer (64 g kg-1). Selection for either DW or NC alone under these N levels predicted negative correlated responses in the unselected character. Theoretical selection response using independent culling levels for DW followed by NC was greatest under the 33 kg N ha-1 fertilization level (197 g kg-1 and 61 g kg-1 per cycle, respectively). Results of actual selection tests agreed closely with predicted gains and indicate that effective selection for forage DW and NC can be conducted in the field with a low level of N fertilization.

Research supported by Western Regional Project W-126 and the California Crop Improvement Assoc.

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