Cover-Cropping & Occultation for Increased Soil Fertility
If you are familiar with us here at Rivendell, you understand that soil health is one of the most important topics & practices we recommend. It is not uncommon for us to diagnose a soil concern that may only need minor adjustments and not a list of products and procedures. Over the years, we have researched and discovered many different methods for increasing soil health and fertility. One of those I would like to talk about today is Cover-Cropping.
Cover crops, also known as “green manure” have been used as a technique to increase soil health in crop production long before common day fertilizers were around. In the early days of United States Agriculture, the U.S monoculture boom heavily depleted our native soils of nutrients. However, by the late 1700’s the use of cover crops grew in popularity and became essential in restoring life to this once vital soil. To know more about how cover cropping can improve biodiversity it’s good to understand how plants react with the soil. In strictly “non-scientific terms” all plants give something to the soil and all plants take something from the soil. Normally this is in the form of essential mineral elements such as; nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, etc. These minerals are essential to plant health and to maximum soil conditions. Most common fertilizers applied these days are synthetic and often are too high in many of these minerals individually. Cover-Cropping however, can replace the synthetic fertilizer with a much more sustainable feeding of organic nutrients over time.
Personally speaking, some of my favorite cover crops are the legume families (Fabaceae or Leguminosae). These legumes are commonly used in cover cropping practices as they add one of farmer’s all-time favorite nutrients into the soil, Nitrogen. Nitrogen for those that don’t know increases the amount of “green growth or new growth” in your plant(s), mostly pushing out more stem and leaf material. This is one of the most common nutrients in commercial fertilizers and tends to be over-applied leaving soils depleted over time rather than restoring it. Many times nitrogen is considered to be a quick-fix for production problems, however in life, the quick fix is often times not the ideal way to go about things. In this regard, cover-crops can release healthy amounts of nutrients into the soil over time, rather than providing a quick dump of nutrients for fast results. Patience is key here as this can take place over years, but overall you will see much improved quality in your soil in comparison. Providing less erosion, less noxious species invasion, less need for pesticides and a much better water retention system for your space. Some of our favorite legumes for cover-cropping are: Hairy Vetch, Red or Berseem Clover & Winter Peas. (See Fig1.) Often when sowing these legumes, we can mix in a Winter Rye or Annual Ryegrass for support. These grasses sprout very quickly providing great erosion control, increasing percolation, reducing compaction.
Another favorite cover crop of ours worth mentioning is the Tapper Radish. We have personally had much success with its application in our sod fields. (See Fig2.) Tapper radish is similar to a “Daikon” variety of radish. It has a much longer tap root than the traditional table radish. This root when planted among other cover crops works in a contrary motion that’s quite spectacular. While most legumes and grasses tend to grow upward, the tapper radish grows downward into the soil, releasing compaction with a large taproot. This also increases soil aeration and water infiltration improving rooting depth and promoting opportunities for successive crops.
Generally speaking, a cover crop is planted preferably in the late fall or early spring. After these crops grow, providing their nutrients and benefits to the soil, the crops are to be terminated shortly after seeing them flower or bloom. While in large scale farming they use termination methods such as crimping, rolling or mowing. In smaller garden spaces, or sometime even small scale market farms, the act of occultation is the preferred termination method before replanting cover cropped gardens. This is the method I am most familiar with for cover crop termination.
Occultation is described as an event that occurs when one object is hidden by another object that passes between it and the observer, in this case we’re hiding the soil for the Sun with a black/transparent tarp or fabric. You want to make sure your tarp over the garden bed, greenhouse or desired plot is pinned down securely to outlast the wind and weather as it starts to work its magic. There are several options available on the market today but lately I have used an EPDM 45 mil Pond Liner (See Fig3.). It’s expensive and heavy so not the best recommendation on a large-scale bed or garden, but it was here on the farm and works extremely well for my small greenhouse. After tarping the desired area, wait 2 to 4 weeks, checking periodically to see how the deterioration process is continuing. Once finished you will see much more dirt and what remains of the plant material yellow and dead-ish looking in color. (See Fig4.) At this point you’re ready to remove the tarp and plant straight into the area. You may also choose to lightly rake in the all of the left over material and add compost for volume as needed.
There you have it! Your garden has now been fertilized in the most natural manner. Now plant away, sit back, and watch the continued improvement in the quality of your plants and soil health. For an added fertilizing regimen, ask us about granular Organic Alpha One fertilizer or OMRI listed Dramm Fish & Kelp products. For any more questions on cover-cropping or soil health in general, give us a shout here at Rivendell!
Fig1. Red Clover & Hairy Vetch
Fig2. Tapper Radish Aeration
Fig3. EPDM Liner Covering Greenhouse Floor
Fig4. Terminated Red Clover and Hairy Vetch