Living Mulches: CSA Week 17

August 21 – 24, 2017

The long season vegetable crop field looks a little hairy, but that is a minor symptom of a great system. Crops like tomatoes and peppers that take a while to mature and then may be harvested over several weeks, or melons and winter squash that take a very long time to mature and get viney, are grown using a plastic mulch strip forming a row. We willfully sow seeds between the plastic strips creating living mulch, while commercial vegetable growers spray herbicides or may repetitiously cultivate out any plants between the plastic. While each is a system, we like ours for several reasons.

John has a big implement he hooks to a big tractor that skillfully opens a furrow to tuck the mulch edges in, as it unrolls the thin film. Then it has a coulter that neatly covers the edges as it moves across the field. Actually three rows are laid with each pass, and after each round (up and back), a drive row is skipped. The trickle irrigation tape is precisely placed under the plastic, adjacent to where the plants will be placed on a later pass. This mulch product is only allowed to be used under the organic standards if we agree to remove it at the end of the crop, so as to prevent the plastic from getting old, becoming brittle and flaking apart. There are several plant-based plastic products on the market, however none are allowed for an organic system at this time. The black color plastic solarizes weed seeds by heating the soil. It also conserves moisture from the trickle irrigation system, and creates a nice warm, moist root zone for our precious transplants to thrive. This technology is a sound, secure, not necessarily cheap, system. The real action is in the middles.

The strip of loose soil between the two edges of plastic must be managed so as to prevent weeds from encroaching over the plastic or even shading the crop. A good farmer would also not like to allow any soil erosion or compaction. Despite these three really big management principles to consider, the “How to….” guidebooks advise growers to either spray herbicides (that’s plural) or design and engineer some type of steel implement to regularly drag up and down the rows to control weeds. Weeds rob moisture first and foremost, but also harbor pests and disease, impede movement of work crews, have their seeds stick to the crop in wet harvests, and the list goes on.

Basically, it is difficult to modify tillage tools to cultivate out small weeds without ripping the edges of the plastic as you go along. But, if you don’t get those pesky weeds (and they can be the most problematic for the crop anyway), your work is unfulfilled. With the growth in market farming, some small businesses have fabricated some slick tools to cultivate in all sorts of conditions, but the equipment is expensive, and time consuming to adjust and run. By continually disturbing the soil to eliminate weeds, the soil particles remain loose and vulnerable to erosion, especially on sloping fields. Considering the water runoff from atop the plastic that is channeled to the edges, the middles have to control more than their share of water anyway. Compaction from tractor tires and harvest crews trampling along helps prevent erosion somewhat in this type of system.

Because of all the work and worry of tillage, most conventional produce growers spray some combination of toxic-to-human chemicals for weed control. Some sprays systemically kill any actively growing weeds while others are engineered to prevent the germination of weed seeds. Simple, proven, reliable, not necessarily cheap technology, but weed problem solved. This is another system.

At Elmwood Stock Farm, we manage the middles in a very different way, with compounding benefits. As soon as the plastic is laid, John sows annual ryegrass, which promptly germinates, dominating the species of active plant growth between the rows of plastic. As you have learned by now, the biology of Mother Nature is our guide. First, the ryegrass, plus the normal share of weed seeds that also germinate, does in fact form a carpet of plants. But it does not rob the crop plants of moisture since we give them all the water they need through the trickle irrigating hose laid under the plastic. The roots of the carpet of plants, hold the soil in place, and prevent erosion even in the heaviest of rains. The plants do, in fact, harbor insects, albeit beneficial ones. The carpet greatly reduces compaction of the soil as harvest crews pick the produce, and there is essentially no dirt splashed up onto the crop, which makes it easier to clean later.

To keep the middles carpet-like, we have several different types of mowers that keep the plants in the middles from getting too tall. Annual ryegrass, by nature, stays short, and being an annual will die back at some point anyway. We spend many hours each week mowing the middles and sometimes even use a weed-eater for detail work. When the viney crops start running we have to let it go, and it can look a little hairy along those rows, but the plants in the middles are not hurting the crop to any extent.

With all the benefits of using living mulch between the rows of plastic mulch, growing of the produce in your share is improving the health of the planet, not taking a little something away. That’s a system that we can believe in. Enjoy! – Mac Stone

In Your Share

Green Beans

Cabbage

Cucumbers

Garlic

Baby Kale

Green Bell Pepper

Potatoes

Tomatoes