Annual and perennial alleyway cover crops vary in their effects on physical, chemical, and biological properties of soil quality in Pacific Northwest red raspberry

Authors: RUDOLPH, RACHEL - Washington State University; Zasada, Inga; Hesse, Cedar; DEVETTER, LISA - Washington State University

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/28/2020
Publication Date: 2/6/2020
Citation: Rudolph, R.E., Zasada, I.A., Hesse, C.N., Devetter, L.W. 2020. Annual and perennial alleyway cover crops vary in their effects on physical, chemical, and biological properties of soil quality in Pacific Northwest red raspberry. HortScience. 55(3):344-352. https://doi.org/10.21273/HORTSCI14511-19.
DOI: https://doi.org/10.21273/HORTSCI14511-19

Interpretive Summary: Cover crops are plants that are grown with, before, or after a cash crop with the intention of benefiting the cash crop and surrounding soil by lessening soil erosion, increasing water infiltration, and promoting pest management. Cover crops are not commonly grown in the area between a raspberry cash crop, known as the alleyway, in the northern part of the United States where most of the US processed raspberries are produced. This means that about 80% of the soil in a raspberry field is left bare. This research was conducted to evaluate the potential positive physical, chemical, and biological impacts that alleyway cover crops can have in the raspberry production system. Alleyway cover crops were compared to the industry standard of bare ground. Results indicate that there were no negative impacts of alleyway cover crops on raspberry yield. The many potential benefits that cover crops provide to soil out-weigh the industry standard of bare soil. This research will be used by scientists and farms to further the adoption of cover crops in the raspberry production system.

Technical Abstract: Cover crops can lessen soil erosion and compaction, improve water infiltration, enhance nutrient availability, suppress weeds, and promote pest management. However, cover crops are not commonly used in alleyways of established red raspberry (Rubus idaeus) fields in the Pacific Northwest of the U.S. A two-year study was conducted in an established ’Meeker’ raspberry field in northwest Washington to evaluate the effects of eight annually-seeded alleyway cover crops (cultivars of wheat, cereal rye, triticale, oat, and ryegrass), one perennial ryegrass alleyway cover crop, mowed weed vegetation, and the industry standard of cultivated bare soil (Till) on the physical, chemical, and biological properties of soil quality; raspberry yield and fruit quality were also evaluated. Twelve months after the first seeding, raised beds adjacent to ‘Norwest 553’ wheat had the highest CEC, but was only significantly higher than ‘TAM 606’ oat (11.9 and 9.8 meq 100 g-1, respectively). Six months after the second seeding, beds adjacent to ‘Trical 103BB’ triticale and ‘Rosalyn’ wheat had the highest CEC (12.1 and 11.8 meq 100 g-1, respectively), significantly higher than bed soil adjacent to ‘Nora’ oat (9.5 meq 100 g-1). At that same sampling date, alleyways planted to ‘Trical 103BB’ had the highest mean CEC (10.2 meq 100 g-1) and ‘Nora’ oat alleyways had the lowest (8.4 meq 100 g-1). The alleyways planted with the perennial ryegrass mix had the lowest mean Db six months after seeding (1.10 g cm-3) and 24 months after seeding (1.09 g cm-3). Tilled alleyways had the lowest Db 12 months into the study (1.01 g cm-3) and 18 months into the study (1.03 g cm-3). Raspberry grown adjacent to Till did not have significantly higher yield or fruit quality than raspberry grown adjacent to cover crops in either year of the experiment. Differences in microbial community structure were observed among seasons rather than treatments. These results indicate that alleyway cover crops have no impact on raspberry production and minimal impact on the quality of soil surrounding the raspberry crop.