Diversifying agriculture and finding ways to sustainably feed more people with ever-shrinking farmland has become increasingly important. One option to increase production on limited farm space is to use intercropping systems. Intercropping is the process wherein two or more crops are grown in the same plot to more efficiently use space (Andrews and Kassam, 1976). In addition to not competing for light and space, plants used in an intercropping system must be temporally and physiologically compatible for this growing method to work.
Other options for increasing crop production include using rowcovers and high tunnels for season extension (Lamont, 2009). High tunnels are low-cost structures used for season extension and to protect high-value specialty crops from sudden dips in temperature or damage from high winds and hail (Belasco et al., 2013; Ward and Bomford, 2011). Because high tunnels are heated with passive solar energy, they do not use electricity and are ideal for the cold winters of northern New Mexico, where there is ample sunlight to warm the air in high tunnels even when temperatures fall below freezing (Hecher et al., 2014). In New Mexico, high tunnels can be constructed for as little as $2 to $3 per square foot, making them more economically viable than greenhouses for many small-scale farmers (Walker et al., 2012). Investing in a high tunnel means a farmer may produce crops earlier and can expect to produce longer with the ability to charge premium market prices (Carey et al., 2009). Studies conducted in New Mexico growing blackberry cultivars in high tunnels have shown blackberry to produce 1 to 3 weeks earlier and produce over a longer period than those grown in fields (Yao et al., 2018). In similar high tunnel studies, blackberry yields have more than doubled with the use of high tunnels while reducing pest pressure and lowering the need for pesticide applications (Demchak, 2009; Rom et al., 2010).
Winter greens were chosen for their high market value when grown organically and their suitability to cooler temperatures and frost tolerance (Ernst et al., 2012; Heyduck et al., 2019; Johnny’s Selected Seeds, 2019; Walker et al., 2012). In this study, ‘Red Russian’ kale and ‘Bloomsdale Long Standing’ spinach were selected as the annual winter intercrops. The temperature range for optimal production of kale is between 45 and 60 °F (Johnny’s Selected Seeds, 2019). The temperature range for optimal spinach production is between 60 and 65 °F with lethal minimum temperature being 0 and 5 °F (Walker et al., 2012). Kale grows to a mature leaf size in 50 d, whereas spinach grows mature-sized leaves in 45 d (Walker et al., 2012). Similar maturity rates and harvest methods make the greens compatible for this intercropping study where plots of both greens were often harvested at the same time. These two greens species were also chosen because they could be direct seeded in autumn under the dormant blackberry canes and harvested multiple times in the “cut and come again” method (Voyle, 2014). High tunnel growing also consistently produces high-quality produce because it can prevent crop stress by maintaining a more controlled growing environment (Lamont, 2009). Previous surveys of commercial growers have shown that high tunnels may be beneficial for the production of winter greens worldwide by protecting crops from inclement weather and through season extension (Lamont, 2009). The use of high tunnels in other states with similar climates to that of northern New Mexico have been successful in growing blackberry, kale, and spinach (Borrelli et al., 2013; Lamont, 2009; Lamont et al., 2003; Yao et al., 2018). In addition, kale, spinach, and blackberry are already being grown and sold in local farmers’ markets in northern New Mexico.
In previous studies, growers report that cane fruit grown in high tunnels also produces higher quality fruit with a longer shelf life than field grown berries (Lamont, 2009). Both cultivars of blackberry are floricane-fruiting, meaning that they grow productive floricanes off of 1-year-old primocanes (Galletta et al., 1998a). Blackberry, like other cane fruit, are perennials and require a period of winter dormancy with a gradual increase in temperatures to break dormancy and promote bud formation (Black et al., 2008). The primocanes must maintain good vine health over the winter dormancy to be able to bud out into fruitful floricanes the following spring (Black et al., 2008). Blackberry has a lethal minimum temperature of 0 °F, after which canes will exhibit damage and be less fruitful (Yao, 2018). To be fruitful, blackberry needs a dormancy period with 300 to 900 chilling hours spent in temperatures below 45 °F (Stanton et al., 2007). Blackberry canes can live for 15 years and are productive for 9 years, depending on cultivar and cultivation practices (Takeda et al., 2002). The goal of this study was to determine the functionality of growing winter greens and blackberry in an organic year-round intercropping high tunnel production system. The objective was to evaluate yield and quality of two blackberry cultivars in an organic open field without any intercropping and in a high tunnel intercropped with kale and spinach.
Andrews, D.J. & Kassam, A.H. 1976 The importance of multiple cropping in increasing world food supplies, p. 1–10. In: R.I. Papendick, P.A. Sanchez, and G.B. Triplett (eds.). Multiple cropping. ASA Spec. Publ. 27. ASA, CSSA, and SSSA, Madison, WI
Belasco, E., Galinato, S., Marsh, T., Miles, C. & Wallace, R. 2013 High tunnels are my crop insurance: An assessment of risk management tools for small-scale specialty crop producers Agr. Resour. Econ. Rev. 42 403 418
Black, B., Frisby, J., Lewers, K., Takeda, F. & Finn, C. 2008 Heat unit model for predicting bloom dates in Rubus HortScience 43 2000 2004
Borrelli, K., Koenig, R.T., Jaeckel, B.M. & Miles, C.A. 2013 Yield of leafy greens in high tunnel winter production in the northwest United States HortScience 48 183 188
Carey, E.E., Jett, L., Lamont, W.J., Nennich, T.T., Orzolek, M.D. & Williams, K.A. 2009 Horticultural crop production in high tunnels in the United States: A snapshot HortTechnology 19 37 43
Ernst, T., Drost, D. & Black, B. 2012 High tunnel winter spinach production. 19 July 2019. <https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=1298&context=extension_curall>
Hecher, E.A.D.S., Falk, C.L., Enfield, J., Guldan, S.J. & Uchanski, M.E. 2014 The economics of low-cost high tunnels for winter vegetable production in the southwestern United States HortTechnology 24 7 15
Heyduck, R., Guldan, S.J. & Guzman, I. 2019 Effect of sowing date and harvest schedule on organic spinach grown during the winter in high tunnels HortTechnology 29 320 329
Johnny’s Selected Seeds 2019 What to plant now—Beets, fennel & kale. 5 Oct. 2019. <https://www.johnnyseeds.com/growers-library/vegetables/growers-library-vegetables.html>
Lamont, W.J., Orzolek, M.D., Holcomb, E.J., Demchak, K., Burkhart, E., White, L. & Dye, B. 2003 Production system for horticultural crops grown in the Penn State high tunnel HortTechnology 13 358 362
Longstroth, M. 2013 Winter dormancy and chilling in woody plants. 10 Mar. 2019. <https://www.canr.msu.edu/news/winter_dormancy_and_chilling_in_woody_plants>
McWhirt, A. 2016 Blackberry variety selection. 19 July 2019. <http://extension.missouri.edu/greene/documents/Horticulture/Blackberry/Blackberry%20Cultivars%2C%20McWhirt%20Nov_15%2C2016.pdf>
Rom, C.R., Garcia, M.E., Johnson, D.T., Popp, J., Friedrich, H. & McAfee, J. 2010 High tunnel production of organic blackberries and raspberries in Arkansas Acta Hort. 873 269 276
Salgado, A.A. & Clark, J.R. 2015 Blackberry growth cycle and new varieties from the University of Arkansas. 19 July 2019. <http://www.vsuag.net/wp-content/uploads/2015/03/Salgado-Virginia-2015.pdf>
Stanton, M.A., Scheerens, J.C., Funt, R.C. & Clark, J.R. 2007 Floral competence of primocane-fruiting blackberries Prime-Jan and Prime-Jim grown at three temperature regimens HortScience 42 508 513
Takeda, F., Strik, B.C., Peacock, D. & Clark, J.R. 2002 Cultivar differences and the effect of winter temperature on flower bud development in blackberry J. Amer. Soc. Hort. Sci. 127 495 501
U.S. Department of Agriculture 2019 Plant hardiness zone map New Mexico. 20 July 2019. <https://planthardiness.ars.usda.gov/PHZMWeb/Default.aspx>
Voyle, G. 2014 Cut and come again vegetables. 31 May 2019. <https://www.canr.msu.edu/news/cut_and_come_again_vegetables>
Walker, S.J., Uchanski, M.E. & Jimenez, D. 2012 Hoop house vegetable production. New Mexico State Univ. Coop. Ext. Serv. H-252
Weather Atlas 2019 Monthly weather forecast and climate Alcalde, NM. 20 July 2019. <https://www.weather-us.com/en/new-mexico-usa/alcalde-climate>
Yao, S. 2018 Blackberry production in New Mexico. New Mexico State Univ. Coop. Ext. Serv. H-325
Yao, S., Guldan, S. & Heyduck, R. 2018 Organic blackberry cultivar trials at high elevation and in high pH soil in the southwestern United States J. Amer. Pomol. Soc. 72 201 208