Growing With Green Manure

Green Manure Cover Crop

Cover cropping is a well known practice, and the current groundswell of interest in backyard organic gardening has everyone doing it. It is pretty common to find field peas, oats, buckwheat and other traditional agricultural cover crops in garden centers, packed in small packets to sow in plots as small as fifty square feet. Planting a green manure cover crop intensifies the fertility benefits of traditional cover cropping.

Check out 8 Steps to Better Soil:

Green Manure Definition

What’s the difference between a cover crop and a green manure? A cover crop is planted to maintain or improve the garden’s fertility when it is not in active crop production. A green manure is a cover crop that has been tilled into the soil . The term “green manure” implies that the fertility benefits resulting from this practice are similar to the benefits of using animal manure in the garden.

Reaping The Benefits

Crop selection and timing are key elements of successfully using a green manure cover crop. During crop selection, consider what each  option has to offer and how that may relate to the needs of the garden plot. Mixing several plant families in the cover crop can be very beneficial for general improvement. From a timing standpoint, matching the crop to the season is critical. Also, consider that the greatest nutrient value is generally obtained by incorporating the crop into the soil after it flowers but before it goes to seed.

The Best Green Manure Crops

Legumes, grasses and brassicas are traditionally considered the best green manure cover crops. Legumes (peas, beans, vetch, clover) collect nitrogen from the atmosphere and store it in their roots. Grasses (rye grass, rye, wheat, oats) scavenge nutrients from the soil that would otherwise leach away with rainfall or snow melt, and they produce abundant biomass which translates into soil organic matter after tillage. Brassicas (radish, mustard), in addition to their nutrient scavenging ability, help to suppress soil-borne pests such as bacteria, fungi, insects, nematodes and weeds by releasing  biotoxic chemical compounds as they grow.

Check out 9 Great Cover Crops to plant in your garden:

Green Manure Advantages And Disadvantages

The advantages of incorporating a green manure in the garden are plentiful. Green manure:

• improves soil structure (water drainage and retention balance).
• builds soil organic matter.
• stimulates soil microbe activity.
• increases nutrient levels.
• makes existing nutrients more readily available for production crops.

Two possible disadvantages of using cover crops as a green manure. First, the decomposition process of the green manure requires water, which means a bit more irrigation may be in order early on as the successive crop gets established. Also, when space is limited or where year-round gardening is possible, green manure cover crops may “get in the way” of production crops. In these instances, copious amounts of compost may be a good alternative.

For healthier soil and a more productive garden, consider adding a green manure cover crop into the crop rotation. It is a good way to recharge the soil, after several seasons of vegetable production. Also for new gardens, it is a perfect way to condition the ground prior to the first vegetable planting. Happy gardening!