Don’t scrimp on plastic when wrapping midsize square bales, say University of Wisconsin researchers.

That’s one of their recommendations following a series of bale wrapping studies at the university’s Lancaster Research Station. All studies involved 34 x 32 x 60” bales of alfalfa and alfalfa-grass mixtures.

In one trial, bales were wrapped with two to 10 layers of either 1- or 1.5-ml-thick plastic. Average moisture content at baling and wrapping was 30%, and the initial internal bale temperature was about 105º.

Bales wrapped with two 1-ml layers of plastic remained at 105-110º, indicating that oxygen was leaking through the plastic to support continued microbial activity. Those bales had significant mold throughout when opened for feeding.

In bales wrapped with 6 mls or more of plastic (four 1.5-ml layers or six 1-ml layers), the temperature immediately began to decline and fell to ambient temperature in eight to nine days. Those bales had only a little white mold on their exteriors.

The study also was conducted using 56%-moisture bales, with similar results.

The Wisconsin workers offer these additional bale wrapping suggestions:

• Wrap bales within 24 hours of baling to avoid high internal temperatures, moldiness and lower forage quality.

• Select a target moisture you can work with. Producers often want 40-55% moisture bale silage, but some bale and wrap wet hay (20-35% moisture). That can help avoid rain, but probably isn’t the best option.

• Make dense bales. They have less oxygen in them initially and let less oxygen enter later. Ideally, midsize square bales should have 100 lbs of dry matter per foot of length.

• Make bales the correct size and weight for the wrap-per. Heavy bales have more problems with plastic tears and holes during wrapping, stacking and storage. Typically, bale weights in excess of 1,400 lbs are a problem.

• Select a good working area for wrapping. It should be level and free of hay stubble or other sharp projections.

• Stack the wrapped bales. Stacked bales take up less space and help protect themselves from the elements, rodents, birds, etc. Stacks also are easier to check and manage than individual bales.

• Check the stacks monthly and repair damaged plastic. Tape small holes and tears, and rewrap any bales with significant tears.