Monday, 7 November 2005 - 8:00 AM
63-2

Potassium Content of Turfgrass Leaves Expressed on a Tissue Water Basis.

Micah S. Woods, Frank S. Rossi, and Quirine M. Ketterings. Cornell University, Dept. of Horticulture, 134A Plant Science Building, Ithaca, NY 14853

Potassium content of turfgrass leaves is usually reported on a dry weight basis as g K kg-1 dry matter (KD). By measuring tissue water content (TWC), K can alternatively be expressed as mmol K L-1 (KW). We compared KD to KW in creeping bentgrass [Agrostis stolonifera var. palustris (Huds.) Farw.] tissue samples collected from field- and greenhouse-grown plants that were treated with varying rates of K fertilizer, grown in sand rootzones of differing exchangeable K content, and allowed to vary in TWC. A generally accepted sufficiency range of KD is (15 to 30 g kg-1), and KW may need to be maintained above 80 mmol L-1 to meet the biochemical K requirement, with additional K contributing to the biophysical demand for K. We found that in a range of KD from 5 to 25 g kg-1, the KW ranged from about 50 to 230 mmol L-1. However, samples with KD below 15 g kg-1 often had KW above 150 mmol L-1. Increasing TWC is associated with lower KW and higher KD. It appears that much of the variability in KD can be explained by TWC, and the sufficiency ranges for creeping bentgrass K content may be more physiologically meaningful if they are based on KW rather than KD.

 


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