Advancing living mulch in plasticulture vegetables

Advancing living mulch in plasticulture vegetables

Summary

Replacing bare row middles with living mulch has the potential to reduce herbicides while improving harvest conditions on Northeast vegetable farms. In 2014 we established 4 living mulch treatments between rows of peppers on a cooperating farm in Yates County, NY and between onions on another cooperating farm in Seneca County. The living mulches were rye, barley, rye+clover and clover+barley.  To measure the effect of the living mulch we collected data on yield, weed growth and crop nutrient levels.  There were significant differences in the different mulch treatments in weed suppression. Adding clover to the grasses vastly improved ground cover by cover crop late in the season. Rye+clover surfaced as one of the better options. Crop yield differences are not as pronounced, but often similar to cultivation plots. Statistical analysis is ongoing. Current results were shared with other farmers at field meetings and will continue this winter at formal educational events throughout the state in the coming months.

Objectives/Performance Targets

2 on-farm demonstration trials were established with cooperating farms in Yates and Seneca Counties (NY). Replicated plots of peppers and onions were established in the Spring of 2014 with living mulch treatments of rye, barley; combinations these winter grains with Dutch white clover, cultivation (Seneca) and composted mulch (Yates). Our seeding rates were 150 lbs/ac for grains and 20 lbs/ac for the Dutch White clover. Seeding occurred immediately after plastic was laid, prior to transplant. Fertility and pest management per grower standards. Marketable yield as measured by fruit number and weight, fresh weight of weeds, crop disease severity, plant height (onions only), vegetable crop petiole nutrient levels, insect damage incidence, and percent soil cover data were recorded throughout the season. In the fall/winter treatment response data was tabulated, and processed through an analysis of variance (ANOVA). Treatment means were separated using Fisher’s Protected LSD at the .05 significance level.  A demonstration meeting was held at the Yates County cooperating farm on August 29th with project findings also presented in Seneca County on July 23 and Cattaraugus County on August 8.  An article was published in the team newsletter ‘VegEdge’ on August 8th; social media feeds on Twitter and LinkedIn promoted the project with photo updates.

• Handout from a summer field meeting

Accomplishments/Milestones

Pepper Weed control: 

In the pepper trial rye+clover had the lowest fresh weight of weeds, and the highest percentage of ground cover; approaching 100% at the July sample date (see attached charts). Our observations are that barley dies out too early (often from a Rust caused by the fungus Puccinnia graminis) and provides very little coverage allowing weeds to germinate in mid-summer.  Rye outlasts barley but also dies too early to compete with mid-late season weed pressure.  Barley+clover provides fair weed control, but the barley may die back too early for complete clover establishment.  To date in our trials rye+clover provided the best weed control as the rye lasts long enough for the clover to establish.

Onions: Weed Control

Cultivated plots were hand hoed once on June 23. All plots were managed with a string trimmer for the remainder of the season. Therefore, weed fresh weight and cultivation plot percent ground cover on June 12 should be evaluated in a pre-control context. Above ground biomass weed fresh weights did not differ among treatments in July, August, or September (see attached Onion Charts).  

Weed control significantly differed among treatments. The barley died out early and allowed weeds to become the dominant ground cover by August. At the end of the season barley clover and rye were better than barley alone, while cultivation overlapped all three. While there were fewer weeds in the plots with good living mulch canopies, the escapes were large and rebounded more quickly after trimming. Conversely, the plots with poor living mulch canopies often had a flush of weeds that were younger and less established before trimming. Fresh weights and ground cover by weeds should be considered together to gain the most complete understanding of weed competition.

Winter barley and cereal rye are not well adapted to summer conditions in the vegetative state. Barley began to die back in June, and was essentially gone by mid-August. The rye decline started in late June and was less severe. Rye alone still provided 22% ground cover in early September. Adding clover to the grasses vastly improved ground cover by cover crop late in the season.

Weeds alone contributed to the total ground cover in the cultivation treatment. In an ideal system, excellent weed control in those plots would be associated with very low (5% or less) ground cover. Total ground cover varied between treatments after June. However, control varied within living mulch treatments in August and September only, when barley/clover had significantly more ground cover than rye. Barley clover was the only treatment included in the analysis where more of that total cover was in living mulch than weeds. Though not included in the analysis, rye clover’s two plot average indicates that it controls weeds at least as well as barley clover.

Onions: Yield

The average weight/bulb in the cultivation treatment was statistically greater than the rye, barley and barley clover treatments. There were no significant differences in grade distribution (boiler, small, medium, jumbo, colossal) or weight. Onions were classified into three market groups: “Big” (medium and up), “Tiny” (small and boilers), and “Unmarketable/Bad” (rot and general cull). There was no difference in market category and economic value ($0.50/big onion). Small onions have very little wholesale value and thus were not included in economic calculations.

Data analysis to be completed in 2014 includes foliar nutrient analysis and pepper yield.

• Charts showing weed control in pepper trial

Impacts and Contributions/Outcomes

Grower interest in living mulch as an alternative continues, although stand establishment and management continue to be a challenge.  Inadequate moisture or poor weed control prior to seeding can reduce weed control.  Both cooperating growers express concerns with the management (mowing) of a living mulch in-season, although this labor appears to be similar or less than cultivation.  The project team has gained confidence in recommending the addition of Dutch White Clover to a winter grain for those growers interested in the benefits offered by this system: weed control without herbicides, improved harvest conditions, reduced erosion potential and increased organic matter.

Collaborators: