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During 1998 we addressed 2 questions with our garden. First, how well does growing through a tarp work? Second, can you grow potatoes using no-till?


Does growing through a tarp improve productivity? This trial comes in 2 parts; first with black tarp (visqueen {defined}) and second with a clear tarp. The idea being that the tarps would help warm the soil and speed plant growth. I would like to point out that these trials are qualitative, rather than quantitative, designed to give us an idea whether they are worth pursuing with our limited manpower.

The dark tarp actually cooled the soil. This produced a marked variation in weed growth, with the tarped area sprouting weeds a week sooner than the adjacent untarped area. As soon as this was evident we discontinued the test.

The clear tarp markedly increased germination and growth rate. We had a 6m by 7 m (19 foot by 24 foot) spot of potatoes planted under a clear tarp. Some of the area was planted before the tarp was spread, and some after (the part that was planted after tarp was spread was done by cutting holes in the tarp). After germination holes were cut in the tarp for the plants to grow through.

Results were impressive. Growth was about 20% faster than normal, weeds were almost completely controlled (the only place weeds grew was through the holes the potatoes were growing through) and yield was well above normal. In addition the tarped area needed slightly less water than untarped areas, especially during the critical early month (when rainfall in Fairbanks is practically non-existant).

Two problems were encountered.

  1. Lack of water on the top rows. This was caused by the tarp preventing water from getting to the plants. The lower parts (downhill; the plot slopes about 5 degrees) of the tarp received enough water through the holes. This problem would be overcome by creating small ridges in the soil before the tarp was spread, trapping the water closer to where it fell (or was applied).
  2. The rapid growth exceeded the ability of our organic soil to release nutrients. This did not prove to be a problem this time, for the crop was nearly ready to harvest before symptoms of deficiency (yellowing of older leaves, indicating nitrogen deficiency) appeared. A manure tea would offset this problem.

Tarping is an excellent way to boost yield and growth rate. This may not prove applicable in our CELSS {defined} projects, for we will attempt to maintain a more ideal soil temperature.



We had a few seed potatoes left over when we were done planting, so we decided to see if they would grow in an area that hadn't been tilled since the previous year. Potatoes definitely do not grow well (yield was down about 75%) unless you till.

We still believe that growing wheat using no-till will be a good way to go. Experiments have not yet been done to prove this though, so we will be doing this kind of experiment once we have an operational CELSS.

Copyright © Spring 1999