Biodegradable Paper Mulch: An Organic Option for Day‑Neutral Strawberry Growers

UNIVERSITY OF MINNESOTA EXTENSION - www.extension.umn.edu

Organic day‑neutral (DN) strawberries continue to gain interest across Minnesota and Wisconsin thanks to their long harvest window and strong local demand. But DN systems also bring significant weed pressure, and most growers rely on polyethylene (PE) plastic mulch for weed control and moisture management. With growing concerns over the environmental fate of plastic-based mulch, many growers are asking whether paper mulch is a viable alternative.

A recent two‑year study from the University of Minnesota and the University of Wisconsin–Madison compared biodegradable paper mulch with three types of PE plastic mulch in certified organic DN strawberry production. Below are the key findings for growers.

Why Consider Paper Mulch?

• It is the only biodegradable mulch type currently allowed under USDA Organic rules.

• Paper mulch can be tilled into the soil, reducing waste and end‑of‑season cleanup.

• PE plastic is still permitted but must be removed annually, adding labor and disposal costs.

• PE plastic can be difficult to remove completely, and contributes to microplastics in the soil and environment

Study Overview

Researchers evaluated four mulch types:

• White PE plastic (industry standard)

• Black PE plastic (lower cost)

• Metallic PE plastic (higher cost, improved pest suppression)

• Biodegradable paper mulch (NOP‑compliant)

Trials were conducted in St. Paul, MN and Madison, WI during 2022–2023.

Measurements included yield, labor, material costs, and net returns using realistic direct‑market prices ($8/lb).

Image: Day-neutral strawberries are typically grown in mounded rows with variations of plastic. Far left and far right: white on black plastic; left: paper mulch; center: reflective plastic; right: black plastic.

Key findings

Paper mulch did not reduce yields.

Across Minnesota and Wisconsin, biodegradable paper mulch produced yields similar to PE mulches, averaging about 0.6 lb per plant. Metallic PE mulch had the highest yields overall, particularly in Wisconsin.

Paper mulch costs more to use.

Paper mulch had the highest material cost and required additional labor due to installation challenges and storm damage repairs. Some labor savings occurred later in the season due to good weed suppression, improved moisture retention, and reduced end-of-season removal. Still, these savings did not fully offset higher costs.

Images: Paper mulch is an alternative to plastic shown in tact (top) and disassembled after storm damage (bottom).

Metallic PE mulch was the most economical option.

Despite a higher upfront cost, metallic plastic mulch produced higher yields and lower labor costs per pound, resulting in the lowest total cost per pound among all mulches tested.

Paper mulch was profitable at direct-market prices, but margins were the smallest.

At an assumed price of $8.00/lb, all mulch systems generated positive returns. Paper mulch returned less profit than the PE mulches, averaging about $0.55/lb across both states.

Yield improvements mattered more than price.

Based on a sensitivity analysis, increasing yield per plant had a much greater effect on profitability than increasing price. At high yields (1.0–1.25 lb per plant), all mulch systems—including paper—generated strong returns.

Labor dominated total costs.

Labor accounted for 75–90% of production costs, with harvest making up about half of total labor time.

Take-home message:

Metallic plastic mulch performed best economically. Biodegradable paper mulch is a viable but higher-cost option for organic growers selling at premium prices. Regardless of mulch choice, profitability in day-neutral strawberries depends primarily on yield and labor efficiency.