2018 ASHS Annual Conference

Interest in using impermeable black tarps has increased among farmers. Tarps offer a low-cost option for small scale farmers to prepare land in a reduced or no-till system. Tarping can be used in place of tillage for weed control and cover crop reduction. Lastly, tarps change the soil environment by altering moisture content and temperature effecting soil N mineralization.

In 2017 Research was carried out at the University of Maine Agricultural and Forestry Experiment Station: Highmoor Farm in Monmouth, ME. Two target planting dates were determined, each consisting of four different tarping durations (long, 6 week, 3 week and no tarp) and three tillage treatments: full-till (6 inches); shallow-till (2 inches); no-till laid out in a split block design. Tarps were placed overwinter 24 weeks before planting 1, 10 weeks prior to planting 2, and then 3 or 6 weeks prior to both plantings. Tarps were placed over an oat cover crop for the overwinter treatment and the cover crop residue for the remaining treatments. Upon tarp removal and prior to tillage, weed and cover crop residue were assessed and soils were sampled for nitrogen (NO3-N and NH4-N). ‘Boro’ beet (Beta vulgaris) was then planted by hand. No weeding was performed in any of the plots. Just prior to harvest weed assessments were made and weed biomass was determined A once-over harvest was made when greater than 50% of the crop reached a diameter exceeding 0.75 inch. Harvested beets were graded by size and quality and then counted and weighed.

Tarping significantly increased marketable yields in both plantings. Tillage intensity, deep, shallow or no-till had no effect on marketable yield in either planting of tarped plots. However, in plots without tarps or tillage yields were significantly lower. NO3-N levels increased in planting 1 with tarps, although not significantly. In planting 2, NO3-N levels significantly increased with tarping period while NH4-N levels were significantly lower under tarps. Weed cover immediately after tarp removal was significantly lower in all tarping treatments compared to no tarp; while, cover crop residue was similar between tarping lengths. Weed biomass at harvest was significantly greater in plots without tarps and tillage in both plantings.