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Agronomy Journal Abstract -

Growth of Subterranean Clover in a Range Soil as Affected by Microclimate and Phosphorus Availability. I. Field Studies1


This article in AJ

  1. Vol. 69 No. 1, p. 21-25
    Received: Jan 31, 1975

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  1. C. A. Raguse and
  2. R. A. Evans2



Relationships between microenvironment and phosphorus availability are important to stand establishment and winter growth of introduced annual legumes in California's foothill rangelands.

Ridge, furrow, north-facing, and south-facing microsites were established to create variations in light and temperature micro environments in previously tilled soils of the Sobrante and Las Posas series. An additional microsite treatment, consisting of a simulated range drill seeding, with and without a litter cover, was made on adjacent untilled soil. Phosphorus rates, applied as single superphosphate, were 0, 40, 80, and 160 kg P/ha.

Pellet-inoculated seeds of subterranean clover (Trifolium subterranean L.) were sown in rows 15 cm apart perpendicular to the microsite ridges, slopes, and furrows.

Soil (1 cm) and air (3 cm above soil) temperatures were monitored hourly with thermistors.

Plant sampling was done at four times from November to March to determine morphological development, plant weight, and percent P per plant. At maturity, remaining plants were sampled to estimate seed production.

Large diurnal temperature differences were associated with microsite treatments and were more pronounced for soil than for air.

Percent P in shoot tissue generally reached highest values in January, indicating that plant growth was restricted more during winter than was P uptake. With warmer temperatures and higher light intensities in February, growth dilution resulted in a decrease in P percentage. Small modifications of microrelief significantly altered the microenvironment, especially soil temperature. Morphological development and plant weight responses were greatest on south-facing slopes and at the highest P level. Seed production was not influenced by P fertilization.

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