Several species of both specific and generalist predator and parasite populations have been shown to increase in living mulch plots. But many other studies indicate that several insect pests are controlled in living mulch as compared to bare soil plots. Researchers from South Dakota found lower seedling emergence and survival and higher amounts of disease-causing fungi in clover and hairy vetch mulched fields, when crops were planted during cool weather. In cold, wet soil, living mulches may encourage disease and some pests such as slugs or snails. In a 2- year study, we discovered that the living mulch was providing a home for many kinds of predators who were controlling cabbage worms in our commercial plantings of broccoli, cabbage, and Brussels sprouts. In my 17-year living mulch vegetable production system, insect and disease problems simply dropped off the radar – including cabbage worms.

LESS PEST MANAGEMENT Living mulches provide diversity and a legume “crop rotation” which is the foundation of disease suppression in all organic gardens and farming systems. Again, the key is managing the competitive interrelationships between the living mulch and your crops. We can design around this biological fact. In other words, over time living mulches can conserve moisture in your garden, but in the short term, especially right after planting, they compete with crops for soil water. Soil water levels were higher than in bare soil after four weeks. But, by two to four weeks after planting, soil moisture levels were the same as in bare soil treatments. In one study, corn grown in mowed hairy vetch struggled for water during the first 1 – 4 weeks after planting. Living mulches hold onto and recycle soil water when NOT actively growing. However, in the short term, most living mulches steal soil water from crops when both are actively growing, especially early spring through early summer. Soil organic matter acts like a big sponge soaking up water and releasing it slowly when needed. LESS IRRIGATION, MORE WATER CONSERVATION Because living mulches add soil organic matter over time, in the long term they help to conserve soil water. The key is managing the competitive interrelationships between the living mulch and your crops. Though fruit maturity was delayed, yields of tomatoes grown in hairy vetch were higher and fruit weights were greater than in bare soil treatments. Corn yields were higher in red clover that had been killed in strips.

Leaf cover and yields of bush green beans was higher when planted into a killed stand of hairy vetch. When compared to plants grown without mulch in bare soil, legume living mulches produce higher vegetable yields. When mowed regularly or tilled into the soil, living mulches add plant nutrients for free, including the big three: nitrogen, phosphorus, and potassium, as well as sulfur, calcium, and micronutrients. This is because living mulches add organic material into the soil without disturbing it. HAPPY PLANTS PRODUCE MORE Over time, living mulches improve soils and build the skeletal framework which holds plant nutrients so that they are available when plants need them. Learn more about Helen’s techniques at including her short video about conservation farming. This article was kindly contributed by Helen, an agronomist who farmed and experimented for 17 years with living mulches in Montana.

Living earth mulch