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Abstract
Nursery cultural practices are used to help growers achieve pre-determined size and physiological targets for seedlings. In that regard, irrigation is used to accelerate or slow growth and as a trigger for changing growth phase. In a case study highlighting the effects of irrigation on seedling development, western larch (Larix occidentalis Nutt.) seedlings were grown under three irrigation regimes to study seedling irrigation frequency, growth, and instantaneous water use efficiency (WUEI). Seedlings were irrigated when daily container weights were reduced to 65% of saturated weight (SW), 85% SW, or at 85% SW for 8 weeks and then 65% SW for the remainder of the growing season. Mean irrigation frequency was once per 7.9, 4.6, and 3.8 days for the 65%, 85% to 65% and 85% treatments. Root-collar diameter (RCD) and height of all seedlings measured mid-way through the experiment revealed that seedlings receiving higher irrigation frequency (85%) were more variable in height than those receiving less irrigation. Irrigation regime did not influence final height or dry mass root:shoot. Mean RCD of seedlings in 85% moisture content treatments was only 2.4% larger than seedlings grown at 65% SW, and WUEI measured on five sample dates during moisture stress periods did not vary between irrigation treatments. Our results show that the environmental costs of increased nursery water use were not justified by a return of increased seedling size and that reduced irrigation decreased variability in seedling height.
Parent Publication
Citation
Davis, Anthony S.; Keefe, Robert F. 2011. Nursery cultural practices to achieve targets: A case study in western larch irrigation. In: Riley, L. E.; Haase, D. L.; Pinto, J. R., tech. coords. National Proceedings: Forest and Conservation Nursery Associations - 2010. Proc. RMRS-P-65. Fort Collins, CO: USDA Forest Service, Rocky Mountain Research Station. p. 128-132.
