Evaluating Cover Cropping and Non-Herbicide Weed Management Strategies in Hops, a Perennial Crop

Evaluating Cover Cropping and Non-Herbicide Weed Management Strategies in Hops, a Perennial Crop

Summary

We are investigating the best strategy to establish and maintain a hopyard with minimal weed populations. Our experimental methods are addressing the following two questions: 1) what is the best non-herbicide cultural practice to control weeds (none, straw, tilling), and 2) is a weed-suppressing cover crop effective in reducing weed populations and is it worth delaying hops planting by a year. In spring, 2011 we established 3 additional acres of hops. This land was previously pasture (2009-2010) or fallow (2011) before we purchased the land in 2011. In October 2011 the land was plowed, disced, and soil tested. It abuts lawn, old field, fallow field, and cultivated land.

To investigate question 1, we established hops plantings in 2012 and used three approaches to manage weeds between plants (‘intra-row’): none (control), 5 cm straw mulch, or bi-weekly tilling. We will conduct these practices again in 2013 to be able to measure weed impacts on both one-year old and two-year old hops plants.

To investigate question 2 we have established some of our new hopyard in a weed-suppressing cover crop (rapeseed, Brassica napus) for year one. We will also maintain an area of fallow land to permit same-year comparisons. In 2013, we will establish hops plants in previously fallow and previously covered plots for comparison. We are using four varieties of hops (Cascade, Centennial, Willamette, and Mount Hood) that have different growth characteristics and represent commonly grown hops with the Northeast. We will measure our results by comparing hops linear growth, weed biomass, weed composition, and soil biology across treatments (n > 10 per treatment except for soil biology) and varieties. Hops linear growth is measured as the total plant height from soil to apical tip. Weed biomass and composition are measured using 0.5 m2 quadrats, in which the percent coverage of each weed category/species are tallied in ten plots per variety X treatment. Soil biology will be tested to assess microbial activity differences between fallow, fallow/tilled, fallow/straw, and previously covered plots; however, since only one soil test per treatment will be conducted results will be qualitative only.

To assess question one, we can compare fallow versus straw versus tilling in one year and two year hops. To assess question two, we will compare previously fallow versus previously cover cropped plots’ one–year old hops plant linear growth and weed biomass and composition. We will compare hops planted after cover (2013), with hops planted after fallow (2012) as well as with hops planted on fallow plots during 2013 to control for year effects. ANOVA with Tukey’s test will be used to test significance of potential differences in linear growth and weed biomass. Differences in weed species counts will be transformed to normal before conducting parametric tests. We will also measure time spent conducting all activities and materials costs, in order to produce a standardized dollar value for cost per acre by treatment.

In the 2012 season, we established our new 3-acre hopyard. The land had been bushhogged and plowed in the fall of 2011. In early spring it was disced, and then we added lime and organic nitrogen fertilizer that was tilled to incorporate. Forty-one hop rows, 250 feet long were established at 12 foot intervals. About half of these were planted in 2012 (some for SARE and some not) and the remaining half will be planted in 2013.

While not supported by the SARE, establishing the trellis was the major part of our farm’s work this year, and will be completed in 2013. We peeled, treated and erected 328 22’-25’ tall spruce poles, installed anchors and some cables. The remaining cables will be installed in early spring 2013. We were did not trellis our first year plantings (which is also a customary practice for commercial growers).

This was a slight deviation from our plan to string the vines, but we were still able to accurately measure linear growth of plants and will use the same method again in 2013 for first year plants. We established our SARE plots in 5 rows per variety to accommodate our experimental design (till, do nothing, mulch in year one; with two rows planted in rapeseed for year two plantings). Rapeseed was planted in mid-July, covering 12’ wide for each row to be planted in 2013. The rapeseed established and covered very well, persisting long after a few hard frosts. At the end of the growing season (mid-August through mid-September) we measured plant linear growth and number of bines (all measured within a two-day period) and weed density. The percent coverage of seventeen weed species/categories were tallied in 10 0.5 m2 plots per variety X treatment (120 weed plots total). At the end of the season all plots were straw mulched for overwinter survival.

Since we are comparing the results of 2012 with the coming year’s work in 2013, much of the work remains to be done. We have yet to establish our 2013 plants in the field that was cover-cropped in rapeseed the previous year. In 2013, we will continue to implement three methods of weed control (none (control), straw mulch, or bi-weekly tilling) and record hop plant linear growth, as well as weed biomass and composition in the previously cover-cropped plots at a comparable time of the year (September 2013). We also plan to plant rhizomes on a plot that was previously fallow to control for year effects. We will conduct soil tests again in the fall of 2013. All data analysis, result summaries, website reporting, and manuscript preparation remain to be completed after final data collection is completed after the end of the 2013 growing season.

Accomplishments/Milestones

The rhizomes we purchased had a very low success rate for one variety (Cascade) in particular. Other farmers in the same purchasing pool had the same problem, with an overall germination rate of about 10%. While this reduced our sample size, we think we will still have enough in each of the treatment groups.

Aroostook Hops had previously established a 1-acre hopyard. This past year, we established another 3-acre hopyard, which we will finish planting in the spring of 2013.

We will continue to seek advice from our technical advisor, Marcus Flewelling of Crop Production Services, Inc.

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