Submitted to: Agroforestry Systems
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/3/2008
Publication Date: 3/3/2008
Citation: Burner, D.M., Belesky, D.P. 2008. Relative effects of irrigation and intense shade on productivity of alley-cropped tall fescue herbage. Agroforestry Systems. 73(2):127-139. Interpretive Summary: Information on the design and management of agroforestry practices is lacking, limiting adoption by American landowners. There are strong competitive interactions when crops and trees are grown in close association in agroforestry systems. Our objective was to determine which of two factors, tree shade or soil water, was the greatest impediment to tall fescue production in loblolly pine alleys. Contrary to expectation, ARS scientists from Booneville, AR and Beaver, WV found that tree shade was a greater constraint to grass yield, leaf and stem development, and grass quality than low soil water. The challenge for producers is to design plantations to maximize number of trees per unit area for greatest yield of wood product over time, while simultaneously maintaining alleys sufficiently wide for greatest crop production. The optimum design configuration will depend on site, species, and management objectives.
Technical Abstract: The comparative effects of reduced irradiance and soil water on alley cropped herbage are poorly understood. Our objective was to determine effects of irrigation on herbage productivity when tall fescue [Lolium arundinaceum (Schreb.) Darbysh. = Festuca arundinacea Schreb. var. arundinacea Schreb.] was grown in two sites, a meadow and a shaded (70% canopy cover) loblolly pine (Pinus taeda L.) alley (620 trees/ha), near Booneville, Arkansas. ‘Kentucky 31’ with or without the fungal endophyte [Neotyphodium coenophialum (Morgan-Jones & Gams.) Glenn, Bacon, & Hanlin comb. nov.], and ‘Jesup’ with novel endophyte (MaxQ) were space planted in the meadow and pine alley with or without irrigation. Herbage mass and nutritive value were determined at 8-wk intervals for 2 yr. Solar irradiance, as measured by daily photosynthetically active radiation (PAR), was 16.5 and 11.5% of meadow PAR in 2004 and 2005, respectively. Irrigation compensated for low rainfall and evapotranspiration in the meadow in 2004 and 2005, an especially dry yr, but not in the pine alley. Differences among tall fescue – endophyte associations tended to be small and inconsistent compared to differences between site and irrigation. Low solar irradiance was a greater constraint to herbage specific leaf weight (SLW), leaf extension rate (LER), tillers/plant, mass/tiller, mass/plant, and total nonstructural carbohydrate (TNC) than low soil water. Various silvicultural practices, e.g., wide tree spacing, thinning, and pruning could improve penetration of solar irradiance to the alley crop, although competition for soil water could constrain herbage productivity at the crop-tree interface.