Root Morphology and Vigor Effects on Winter Heaving of Established Alfalfa1
- E. Perfect,
- R. D. Miller and
- B. Burton2
There has been considerable speculation regarding the influence of root system morphology on the susceptibility of alfalfa (Medicago sativa L.) to frost heaving injury. This field study represents a first attempt at quantification of that relationship. A tagging technique was developed for monitoring heave of established alfalfa plants during winter. Measurements were made on a Collamer silt loam (Glossoboric Hapludalf) intergrading to a Niagara silt loam (Aeric Ochraqualf) near Ithaca, NY. Final (net) crown displacement above the soil surface was positively correlated with plant upheaval in midwinter, although maximal uplift was partially reversed as the soil thawed. Plants were retrieved after the winter and evaluated for differences in vigor and taproot architecture. Under comparable soil heaving conditions, 2-yr-old plants with the creeping root trait experienced a mean net uplift of 5.5±1.1 mm compared to 8.5±1.2 mm for plants with a pronounced taproot; this difference was significant at P < 0.06. In contrast, spatial variation in maximum soil heave was more important than root morphological parameters in determining uplift of 3-yr-old plants from a single taprooted cultivar. Only 45% of the total variance in maximal crown displacement could be explained by multiple regression analysis, suggesting that undefined variables, such as root anchorage and tissue elasticity, may be involved. Approximately 60% of the taproots appeared to have heave related lesions. The vigor of these mature plants was generally unrelated to frost heaving; net upheaval was correlated with the degree of crown rot, but not with root rot, number of crown buds, or curculio (Silona hispidula F.) scarring.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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