Digestibility of Kleingrass Forage Grown Under Moisture Stress1
- W. D. Pitman,
- D. M. Victor and
- E. C. Holt2
Low forage digestibility of warm-season perennial grasses frequently limits performance of grazing animals. Digestible energy intake is of particular concern during hot, dry periods of mid-summer. Although relationships between plant characteristics affecting digestibility and temperature, irradiance, and soil fertility have been reported, the relationship between forage digestibility and moisture stress has yet to be clearly determined. The purpose of this study was to determine the influence of moisture limitations on digestibility of kleingrass (Panicum coloratura L.) forage.
Kleingrass plants cloned from a single parent were grown in pots under greenhouse conditions at five watering levels. Soil moisture ranged among watering levels from field capacity down to near the permanent wilting point. Four pots or replications for each of five watering levels were arranged in a randomized block design. Plants were harvested on four successive harvest dates after a 15-day period of regrowth. In vitro digestible organic matter (IVDOM) of leaves and stems, gravimetric soil moisture, plant water status (leaf xylem pressure potential), forage yield, and plant leafiness were determined at each harvest date. Although percent soil moisture and leaf xylem pressure potential declined as a result of successively lower watering levels, yields per pot and IVDOM of both leaves and stems were not significantly reduced until reduced watering lowered soil moisture to 9.1% and leaf pressure potential to −7 bars. Only leaf growth occurred when soil moisture and leaf xylem pressure potential were reduced to 7% and −14 bars, respectively. Leaf and stem IVDOM ranged from 63.8% and 60.8% with non-stressed material down to 33.6% and 42.8% at the most stressed level producing leaf or stem growth, respectively. The results indicate that low forage digestibility of warm-season grasses in midsummer may be associated with moisture limitations.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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