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Charlie Feldhake Dave Belesky

Photosynthically Active Radiation Use Efficiency of Dactylis glomerata in a Hardwood Silvopasture. Charlie Feldhake Dave Belesky. Photosynthically Active Radiation Use Efficiency of Dactylis glomerata in a Hardwood Silvograss-sward. Charlie Feldhake Dave Belesky.

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Charlie Feldhake Dave Belesky

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  1. Photosynthically Active Radiation Use Efficiency of Dactylis glomerata in a Hardwood Silvopasture Charlie Feldhake Dave Belesky

  2. Photosynthically Active Radiation Use Efficiency of Dactylis glomerata in a Hardwood Silvograss-sward Charlie Feldhake Dave Belesky

  3. USDA-ARSAppalachian Farming Systems Research Center Beaver, West Virginia

  4. Appalachia is 23% larger than the state of California

  5. Question 1: How efficiently does orchardgrass utilize PAR at different PAR levels under deciduous trees?

  6. Question 2: Do juvenile plants function differently than vernalized (mature) plants?

  7. (0) Open Site (Eo) 2 m within forest edge (Ew) 7 m within forest edge (W) 30 m within forest

  8. Grasses were grown in 15 cm dia. pots which were placed in the ground after bottoms were removed One set placed in May 2001 Another in August 2001 for harvesting in 2002 3 Harvested at 20 cm height, others clipped to 5 cm

  9. Table 1. Summer solstice (7-week average) actual and relative PAR. Measurement Site O Eo Ew W Max PAR (Mol m-2 d-1) 2001 39.7 18.7 9.7 4.9 59.3 2002 26.8 10.7 6.9 3.7 59.3 % of Open (100-Shade) 2001 100 47 24 12 2002 100 40 26 14 % of Max 2001 67 32 16 8 2002 45 18 12 6

  10. PAR Use Efficiency is equal to total PAR summed from the previous harvest divided by dry leaf mass.

  11. PAR Use Efficiency Eo/O Ew/W W/O 2001 1.4 3.4 3.0 2002 1.2 1.7 2.6

  12. Given one of the most important objectives of agriculture is to harvest solar radiation for human use, then C3 grass open pasture in a temperate, humid climate is not a very efficient way to do it.

  13. But: These Grass Roots Were Not Competing With Tree Roots. What Happens In The Real World?

  14. Leaf Growth Decreased With Daily PAR But Less Rapidly. There Was Less Than A 2-Fold Increase In PAR Use Efficiency.

  15. Leaf Growth Did Not Decrease With Daily PAR. There Was A 5-Fold Increase In PAR Use Efficiency.

  16. The Duration Of Daily PAR Is Important In Addition To The Amount Of Daily PAR.

  17. Forages Under Deciduous Trees Also Receive A Spring And Autumn “Spike” In PAR That Does Not Happen Under Conifers

  18. If you can utilize much of the solar radiation by trees midday through early afternoon and during peak summer intensities you can substantially increase overall system solar radiation harvesting efficiency.

  19. Star PAR Extra-Solar PAR contributes about 5 mg ha-1 yr-1 to corn grain yield.

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