Dactylis glomerata Growing Along a Light Gradient in the Central Appalachian Region of the Eastern USA: III. Nonstructural Carbohydrates and Nutritive Value

Abstract

Microsite conditions influence plant development and resource allocation of Dactylis glomerata L. (orchardgrass), a traditional pasture species with potential as an understory crop in woodlots. A field experiment was conducted to determine how open (O), shaded woodland (W) and open-to-shaded woodland transition zone (E O , E W ) microsites influenced the quantity and distribution of nonstructural carbohydrate (TNC) and crude protein (CP) among plant parts of defoliated orchardgrass. Plants established in spring (SP) or late summer (LS) were clipped each time mean sward height reached 20 cm.Microsite conditions influenced nutritive value of herbage. Nutritive value was acceptable when not more than 45-50% light attenuation (as a function of shading by nearby trees) occurred relative to open pasture. Twice as much TNC accumulated in stembases of LS compared to SP plants. Concentrations of TNC were least in plants growing at W, regardless of planting time. Stembase TNC depletion occurred in SP plants, regardless of microsite, and LS plants growing at W. CP concentrations were greater in herbage from W compared to O sites, suggesting the N needs of the plant were met with minimal fertilizer N inputs. The ratio of C:N and thus herbage energy expressed as total digestible nutrients (TDN), relative to CP declined as shade increased. Increased protein content is offset by lower fiber, lower nonstructural carbohydrate and the possibility of reduced preference by grazers. Nutritive value is improved by modest amounts of shade relative to plants growing in full sunlight, and allowing cool temperate origin grasses to vernalize is beneficial in terms of productivity, nutritive value, and persistence.

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

“…The apparent increase in herbage N observed in the pine alley in 2004 but not 2005 may be a mechanistic response to decreased specific leaf weight (Burner and MacKown 2006;Kephart and Buxton 1993). Belesky et al (2006) observed similar N enrichment when orchardgrass was grown in partial shade compared to unshaded pasture.…”

<b>Growing tropical forage legumes in full sun and silvopastoral systems

“…Under said conditions, the vegetable uses some strategies to reduce stressful effects from the environment. When it comes to shading, there are morpho-physiological changes that allow for increased efficiency in light capture in places where luminosity is reduced (Belesky et al, 2006). The main changes in vegetables subjected to intense shading are: increase in leaf surface, leaf angle, reduction in the number of leaves (drains) and elongated stems (Andrade et al, 2004;Paciullo et al, 2008).…”

Photosynthetically active radiation use efficiency of Dactylis glomerata and Schedonorus phoenix along a hardwood tree-induced light gradient

“…They adapt when growing Agroforest Syst (2009) 75:189-196 193 in shade so their photosynthetic rate is higher at low PAR than for full sun-adapted plants at low PAR (Peri et al 2002), leaves elongate using less structural fiber per unit length, and less photosynthate is allocated to roots and crown, but more is directed toward leaf production. Forage grasses might sustain some level of leaf elongation and production as a response to shading, but nutritive value measured in available herbage energy could be compromised (Belesky et al 2006;Buergler et al 2006). Energy expressed as structural fiber or readily available non-structural carbohydrates is less in shade grown plants than those grown in full sunlight.…”

“…Energy expressed as structural fiber or readily available non-structural carbohydrates is less in shade grown plants than those grown in full sunlight. Since available herbage energy very often is a limiting factor in forage-based livestock production systems, Belesky et al (2006) and Neel et al (2008) found that silvopastures might maintain productivity (forage mass) yet not satisfy grazing ruminant energy requirements. Many of these adaptations are associated with changes in the red/far-red ratio that occurs along with changes in PAR (Wherley et al 2005).…”