Relative effects of irrigation and intense shade on productivity of alley-cropped tall fescue herbage

Abstract

The relative effects of 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.] was grown in two sites, a meadow and a loblolly pine (Pinus taeda L.) alley (620 trees ha -1 ), near Booneville, Arkansas. Three tall fescue entries were space planted in the meadow and pine alley with or without irrigation. Herbage mass and nutritive value were determined at 8-week intervals for 2 years. Mean daily PAR was 33.9 (2004) and 37.5 mol m -2 d -1 (2005) in the meadow, while the pine alley received 5.6 mol m -2 d -1 (17% of the meadow) in 2004 and 4.3 mol m -2 d -1 (11% of meadow) in 2005. Effect of tall fescue entry tended to be small relative to site and irrigation. Irrigation compensated for evapotranspiration in the meadow, but not in the pine alley when summer rainfall was about normal (2004) or low (2005). Nevertheless, site (PAR) had a greater effect on herbage specific leaf weight, leaf elongation rate, tillers plant -1 , mass tiller -1 , and total nonstructural carbohydrate concentration than soil water. Irrigation might have had greater impact on herbage productivity if more water had been applied or if canopy cover had been less extreme. Silvicultural practices should be imposed to improve penetration of solar irradiance to the alley crop.

Effects of tree shading on maize crop within a Poplar-maize compound system in Hexi Corridor oasis, northwestern China

“…However, water and nutrient are sufficient for agriculture in this area because the soil water completely depends on irrigation, and fertilizers are added at the same time. But in agroforestry systems in this area, irrigation generally fails to improve herbage productivity under intense shade of tree, because photosynthetically active radiation (PAR, 400-700 nm wavelength) is a limiting factor (Burner and Belesky 2008) according to the Sprengel-Liebig Law of the Minimum (van der Ploeg et al 1999). Previous studies also showed that when plant growth is not limited by water and nutrients, production is limited by the amount of radiant energy that the foliage can intercept (Monteith et al 1991;Monteith 1994).…”

Limits to recruitment of tall fescue plants in poplar silvopastoral systems of the Pampas, Argentina

“…Besides that effect, the availability of seeds in the soil did not show any constraints. In contrast with tall fescue plants showing declining flowering under evergreen pines (Burner and Belesky 2008), tall fescue plants under deciduous poplars may not compromise the reposition of seeds in the soil bank.…”

“…Grass tillering is usually reduced because the tree canopy decreases the ratio of red/far red light (R:FR) reaching the understory (Casal et al 1987). C 3 grasses' tillering is reduced under pines, poplars or oaks when compared with open pastures (Burner and Belesky 2008;Pincemin et al 2007). …”

“…The timing of litterfall may be a key factor regulating plant tillering throughout temporal changes in light quality (Pincemin et al 2007;Burner and Belesky 2008); but it could also be a barrier to grass seedlings recruitment. Accumulated tree litter limits the recruitment of small-seeded tree species (Dupuy and Chazdon 2008).…”

Management Factors Affecting the Establishment of Pine Based Silvopastures in Southern Grasslands in the United States

“…After trees have become established, it is more likely that growth in the understory will be limited by reduced solar irradiation. Burner and Belesky [5] found that solar irradiation limited the productivity of tall fescue (Lolium arundinaceum Schreb.) growing in the understory of loblolly pines (Pinus taeda L.) planted at 620 tree per ha.…”