Spring planting in mulch helps control weeds, including reducing the need to weed as much. Few weeds will come up through a 4-inch layer of hay.
Advantages and Costs of Mulching
In spring we plant several crops into hay mulch to help control weeds, including reducing the “weed seed bank,” (the “deposit” of weed seeds in the soil that will grow in the future). “One year’s seeding, seven years weeding.” Few weeds other than perennial grasses will come up through a 4″ layer of hay. Mulches of natural materials keep the soil damper, which can mean higher yields and less need to water.
Organic mulches keep temperatures lower in summer, an advantage for cool-weather crops. (Plastic mulches raise soil temperature, an advantage for crops that like warm weather). To avoid cooling the soil when using organic mulches for warm weather crops, it is often best to wait for a month after planting out, remove one round of weeds, then roll out the mulch. Mulches also reduce rain splash, which helps prevent fungal diseases.
Organic mulches improve soil structure and add some organic matter. The earthworm count at the end of the season can be twice as high as under plastic mulch.
It is possible to spread hay or straw over a double layer of newspaper. Only half as much hay or straw is needed, compared to mulching with straw alone, and the final result is only half as deep. This is an advantage when transplanting small plants, which can get lost in deep organic mulch. We avoid using glossy paper with colored inks, because of concerns about toxicity of the inks and the paper coatings. I believe the colored inks used on regular newsprint are not toxic.
Some people warn against the dangers of organic mulches “locking-up” nitrogen from the soil. This may happen in soils that are short on organic matter and micro-organisms, or if high-carbon sources are worked into the soil. In my experience, surface mulches have not caused nitrogen shortages to the crops they mulch.
Possibly our soil is very fertile, and the regular use of mulch has encouraged soil micro-organisms to steadily increase in numbers, so that they can readily digest it. The long-term effect of high-carbon soil mulches can be an increase in soil nitrogen when the micro-organisms feeding on the carbon die and decompose.
We grow our own hay, so we know it is unsprayed – there is a danger from pyridine carboxylic acids, a class of broadleaf herbicides which persist through composting and even through the digestive systems of livestock, and can kill or seriously damage food crops and flowers. Grazon is one brand; picloram is the plant growth regulator it contains.
Mulching With Our Homegrown Hay
Our hay does have some weed seeds, so it’s not the perfect mulch. Unsprayed straw would be better than hay, but we don’t live in a grain-growing area, so there is no straw for sale.
We bale into the big round bales, which we move with the forks or a rear bale spike (spear) on the tractor. We plan our rows to be 5-5-1/2 feet apart (tomatoes) and our beds to be 5 feet apart on centers. We prepare our beds and get the hay delivered to the uphill end (even a small difference in altitude is helpful!). We don’t mulch around our plants, but transplant into rolled out hay, which is much quicker, easier and more effective.
When we plant garlic, we unroll the bales over the top of the freshly-planted garlic as soon as we’ve covered the cloves with soil. For transplants we do what we call “making nests” in the hay.
We remove the twine (sometimes it has already rotted and fallen off) and study the end of the bale to determine which way it will unroll. This can be surprisingly hard to determine, so we might just try it and see. If we have to turn the bale, or maneuver it to line up, we sometimes apply three people.
Once we get it rolling, it’s a two person job (or a solo job once it’s half-rolled). We always have to spend some time with wheelbarrows moving hay from the very thick places to the thin spots. This is partly because the hay we use for mulch is not the best, but often the bales from the field edges.
Making Nests in Hay Mulch
Two people work across from each other, as we plant two rows of broccoli (or cabbage, chard, celery) in each bed. One of the pair has an 18-inch stick and measures the spacing center-to-center. The other person doesn’t measure, but matches the pattern to make a zig-zag, staggering their row compared to the measurer’s row. Both people try to stay 16 inches (less than a stick) from the edge of the bed, so the rows are evenly spaced. Using both hands, they tease an opening in the hay, down to soil level.
The diameter of the “nest” is about 4 inches. We make all the nests before we start planting, to minimize the time the transplants are out in the field still in the flat.
Transplanting into Mulch Nests
We’re busy transplanting our spring broccoli, which you can read about on my blog, www.SustaianableMarketFarming.com. It’s been a challenging “broccoli-planting season” with two very cold nights (20 degrees F and 22 degrees) since we started, some high winds (very cold and drying, hard to keep the row covers in place).
In order to have as long a broccoli harvest period as possible, we use several varieties with different days-to-maturity, and do two sowing dates. This gives us the longest possible harvest period before it gets plain too hot and the broccoli tastes bitter.
We use carts to take the flats and tools out to the field. Each person works along a row, transplanting into the soil revealed in the nests, firming the plants in and watering from a can every 10-20 plants (depending how hot or windy it is). One person wrangles the hose and wand up and down the aisles and gives all the plants a second watering. Then we “tuck the plants in” by pulling the hay around the stems at ground level.
Having the plants “untucked” is the signal to the Hose Wrangler that the plants need water. Once they are tucked, it is the signal to those spreading the row cover to go ahead and cover. We like systems that indicate the next task needed.
Pam Dawling manages the vegetable gardens at Twin Oaks Community in central Virginia. She often presents workshops at MEN Fairs. Pam also writes for Growing for Market magazine. Find her book, Sustainable Market Farming: Intensive Vegetable Production on a Few Acres, in our online store.
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