Science Experiment

 How often does a Community Garden in a suburban town get to prove – and perhaps even to emphasize the importance of – an evolving understanding of an area of agricultural science?

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Appreciation for the concept of the ‘food web’ is surprisingly recent. Here's a nutshell explanation: there is a biome in the soil beneath our plants that is crucial to those plants’ success. It is an interlocking network of microbes, fungi, bacteria and arthropods that are necessary elements of successful agriculture. When you mess with that food web, bad things happen.

Ads proclaim plastic mulch
is eco-friendly

Two years ago, one of the plot-holders in our Community Garden covered a 936-square-foot space (600 square feet of gardens plus a three-foot-wide pathway around the garden’s perimeter) with plastic mats, and was emulated by a few other gardeners. Betty and I began doing research into the topic and found opinions about their efficacy and impact were all over the map.

The gardening season ended and the mats came up.  Over the course of the winter of 2019-2020, we did a deeper dive and found an emerging theme: plastic mulch has a negative effect on the food web. It appears to benefit a crop the first year (by warming the soil), but harms it thereafter as the biome is sharply degraded by leaching petroleum distillates and excess heat which kill off the microscopic life in the soil.

The mats went down for a second year;
the gardener claimed 'hardship'

At the start of the 2020 season, we advised our gardeners not to use plastic mulch. As chronicled here, one gardener claimed to have already put down mats before we notified everyone of the ban, refused to take them up, and demanded a hearing before our town’s Conservation Commission, which approved our ban on plastic mulch but granted the gardener a one-year ‘hardship’ exemption.

In early September, the crops grown
with mats had fared poorly

Betty and I noted across the 2020 season that the crops in the plastic-covered plot didn’t appear to do as well as its neighbors, but there could have been other reasons in play. Without comment, the mats came up at the end of October; but the gardener notified us over the winter that,

An adjacent garden on the same date

because of the pandemic, the family planned to live out of state for the following twelve months.

Demand for plots, already high, exploded this spring of 2021. Many gardeners who had started with 300-square-foot sites wanted to upgrade to full-size ones. In response, Betty and I activated a plan to expand the Community Garden by an additional 3600 square feet – adding between five and ten new plots.

We have been no-till for eight years
and the results have been stunning

For the past eight years, the Community Garden has been ‘no-till’, meaning plots are cleared each fall of fencing and non-compostable garden debris but otherwise left alone for the winter. In the spring, we ask gardeners not to use rototillers and to disturb the soil only as needed to plant; explaining the importance of the food web that is disrupted by unnecessary tilling. The results have been stunning: our dark black soil is alive with organic material, worms and other beneficial organisms. Nutrients are at optimal levels (we take soil samples each spring from multiple plots and blend for testing by the UMass Soil Lab). By not tilling, we also won our war against bindweed, a nasty vine that readily regenerates a new root system when cut into pieces as small as an inch.

In planning for the 2021 season, we made an assumption that, over the winter and early spring, the ‘wildlife under the garden’ would re-colonize the formerly plastic-covered space. In March, we assigned the site to an enthusiastic second-year gardener moving up from a 300-square-foot plot.  She planted both seeds and sets for an intelligently designed vegetable garden. She watered regularly when warranted.

The garden in mid-June 2021. 
Vegetables simply wouldn't grow
in the plot and even weeds were sparse

Six weeks later, she had sparse germination and plants that refused to grow. Instead of lush and dark green, her cucumbers and squash were an anemic yellow. The dirt – ‘soil’ is the wrong word for the brown, dusty stuff that topped the plot – would not hold water. In late July, she gave up. I wrote her a personal check for the cost of her plot, seeds, and extensive plant sets.

At the end of September, Betty and I are allowing the plot to grow up in weeds. Next month, we will overspread it with, and dig in, manure.

Will the space be healthy next spring? It is surrounded by gardens with non-compromised biomes. No point is more than thirteen feet from soil teeming with life. Surely, seventeen months after the plastic mulch was removed from the plot (October 2020), the soil will have healed. Won’t it?

We’re not so certain. We’ll test the plot’s soil early in the spring; then decide if the space is ready to be gardened again.