Weed control is a major concern for Christmas tree growers in the midwestern United States. Controlling weeds improves initial conifer seedling survival and growth after establishment (Harper et al., 2005; Knowe and Stein, 1995; NeSmith and Lindstrom, 1996; Schneider et al., 1998). Weed control is also important to maintain Christmas tree quality by reducing shading of lower branches (Brown et al., 1991). Chemical weed control and mowing are the most common methods of weed control in current production systems and may comprise up to 18% of direct production costs for growers in the midwestern United States (Nzokou and Leefers, 2007). As production costs and environmental concerns related to chemical inputs increase, Christmas tree producers are interested in reducing chemical inputs and costs while maintaining crop quality and growth.
Plastic mulch—usually low-density polyethylene film—improves crop growth in a variety of horticultural production systems (Lamont, 2005). Plastic mulch or synthetic mulch mats have also been used to aid establishment of trees for afforestation and reforestation (Samyn and DeVos, 2002; Walker and McLaughlin, 1989). Plastic mulch typically improves early tree survival and growth, although Harper et al. (2005) found little effect of mulch mats on 10-year height and diameter of douglas fir [Psuedotsuga menziesii (Mirb.) Franco] trees. Plastic mulch reduced growth of Scots pine (Pinus sylvestris L.) Christmas trees compared with a bare-ground control (Lamont et al., 1993).
Plastic mulches affect plant growth by improving soil moisture availability through reduced surface evaporation, reduced water and nutrient loss to competing vegetation, reflected radiant energy, and increased length of effective growing season as a result of soil warming (Lamont, 2005). Organic mulches also improve growth by conserving soil moisture and improving soil physical properties (Chalker-Scott, 2007).
To determine the potential of plasticulture and other mulches as alternative weed control methods, we established a Christmas tree plasticulture study at Michigan State University's Southwest Michigan Research and Extension Center (SWMREC) near Benton Harbor, MI. The objective was to determine the effect of plasticulture technology and other weed control techniques on growth, photosynthetic gas exchange, water relations, and nutrition of newly planted seedlings of fraser fir [Abies fraseri (Pursh) Poir.] and colorado blue spruce (Picea pungens Engelm.), two major Christmas tree species in the upper midwestern United States. We also examined growth and physiological response of seedlings grown with mulch mats and wood chip mulch as alternatives for growers that do not have access to specialized equipment to form raised beds and install polyethylene mulch.
Specific objectives were to: 1) evaluate tree growth, photosynthetic gas exchange, water relations, and foliar nutrition of Christmas trees to irrigation and plastic and organic mulches; and 2) monitor changes in soil environment associated with mulch treatments.
Arthur, M.A. & Wang, Y. 1999 Soil nutrient and microbial biomass following weed control treatments in a Christmas tree plantation Soil Sci. Soc. Amer. J. 63 629 637
Bryla, D.R. & Linderman, R.G. 2007 Implications of irrigation and amount of water application on Phytophthora and Pythium infection and severity of root rot in highbush blueberry HortScience 42 1463 1467
Decoteau, D.R., Kasperbauer, M. & Hunt, P.G. 1989 Mulch surface color affects yield of fresh-market tomatoes J. Amer. Soc. Hort. Sci. 114 216 219
Díaz-Pérez, J.C. & Batal, K.D. 2002 Colored plastic film mulches affect tomato growth and yield via changes in root zone temperature J. Amer. Soc. Hort. Sci. 127 127 136
Díaz-Pérez, J.C., Phatak, S.C., Giddings, D. & Bertrand, D. 2005 Root zone temperature, plant growth, and fruit yield of tomatillo as affected by plastic film mulch HortScience 40 1312 1319
Dodd, I.C., He, J., Turnbull, C.G.N., Lee, S.K. & Critcchley, C. 2000 The influence of supra-optimal root-zone temperatures of growth and stomatal conductance of Capsicum anuum L J. Expt. Bot. 51 239 248
Harper, G.J., Comeau, P.G. & Biring, B.S. 2005 A comparison of herbicide and mulch mat treatments for reducing grass, herb, and shrub competition in the BC interior douglas-fir zone—Ten year results West. J. Appl. For. 20 167 176
Heiberg, N. 1999 Effects of raised beds, black soil mulch and oxadixyl on root rot (Phytophthora fragariae var. rubi) in red raspberry Acta Hort. 505 249 255
Knowe, S.A. & Stein, W.I. 1995 Predicting the effects of site preparation and protection on the development of young douglas-fir plantations Can. J. For. Res. 25 1538 1547
Lamont, W.J., Hensley, D.L., Wiest, S. & Gaussoin, R.E. 1993 Relay-intercropping muskmelons with Scotch pine Christmas trees using plastic mulch and drip irrigation HortScience 28 177 178
Ngouajio, M. & Ernest, J. 2005 Changes in the physical, optical and thermal properties of polyethylene mulches during double cropping HortScience 40 94 97
Nzokou, P. & Leefers, L.A. 2007 Costs and returns in Michigan Christmas tree production, 2006 Michigan State Univ. Ext. Bull. E-2999
Samyn, J. & DeVos, B. 2002 The assessment of mulch sheets to inhibit competitive vegetation in tree plantations in urban and natural environments Urban Forestry and Urban Greening 1 25 37
Schneider, W.G., Knowe, S.A. & Harrington, T.B. 1998 Predicting survival of planted douglas-fir and ponderosa pine seedlings on dry, low elevation sites in southwestern Oregon New For. 15 139 159
Slesak, R.A. & Briggs, R.D. 2007 Christmas tree response to N fertilization and the development of critical foliar N levels in New York No. J. Appl. For. 24 209 217
USDA NRCS 2006 10 Nov. 2008 <http://websoilsurvey.nrcs.usda.gov>.
Walker, R.F. & McLaughlin, S.B. 1989 Black polyethylene mulch improves growth of plantation grown loblolly pine and yellow-poplar New For. 3 265 274