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  • Author or Editor: David E. Radcliffe x
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This study determined the effect of soil amendments on plant available water (PAW) and readily available water (RAW). Intact soil cores were collected from a Cecil sandy clay loam soil landscape planting beds that had been amended annually for 5 years with 5 cm (25% by volume) of pine bark and broiler litter. Soil cores were also collected from a landscape bed that had been amended once in April 2000 with 5 cm (25% by volume) of Permatill (expanded slate). The results of this study indicated that amending soil with pine bark or broiler litter compost increased soil porosity, drainage, aeration and PAW. The volumetric RAW (cm3·cm-3) did not differ among treatments, but amending the soil with pine bark or broiler litter did increase the gravimetric RAW (g·g-1). Permatill increased drainage and aeration, but did not increase available water to plants.

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Container-grown Viburnum plicatum Thunb. var. tomentosum (Thunb.) Miq. `Mariesii' were planted in unamended planting holes, tilled plots, and tilled plots amended with aged pine bark. A 36-day drought was initiated 108 days after planting. Amending induced N deficiencies, reduced shoot growth, and increased root growth. Plants harvested from tilled and planting-hole plots at drought initiation had 63% and 68% more dry weight, respectively, than plants from amended plots. Between 8 and 19 days after drought (DAD) initiation, plants from tilled plots maintained higher relative leaf water content (RLWC) than plants from planting holes. Plants in amended plots maintained higher RLWC than both other treatments between 7 and 33 DAD. Amended and tilled treatments had higher relative leaf expansion rates (RLERs) than the planting-hole treatment 8, 11, 13, and 15 DAD. As the drought lengthened, plants in amended plots maintained higher RLERs than plants in tilled plots. While plants in pine bark-amended plots were more drought tolerant than those in tilled plots, it is unclear if increased drought tolerance was caused by the improved rooting environment or N deficiency.

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