cover crop

Green Manure

The term “Green Manure” is to describe specific plant or crop varieties that are grown and turned into the soil to improve the soil quality. The plants are usually started in the fall are early spring and then cut and tilled into the soil before going to seed.  Some types are left in the ground for an extended period prior to tilling garden areas. It is called green manure because it adds significant amounts of organic matter and plant nutrients to the soil much the same as animal manures do.

We plant Caliente mustard in the fall and it usually winters over and is tilled into the raised garden beds and other areas in the spring a week or two before planting. The reason we use mustard is that studies show that as the leaves are fractured that chemicals (glucosinolates) are released into the soil.  The chemicals act as a natural soil fumigant when the mustard is plowed under and help reduce certain disease and nematode problems especially for potatoes and garlic.

Another good green manure is called Groundhog Radish (there are many varieties). These varieties are bred specifically to form huge tap roots that can reach down into the soil to reclaim nitrogen. The roots also help with water infiltration and soil aeration. Planted in late summer or fall the radishes are left in the soil or turned under.  They are also referred to as a “no tillage radish”.  If left in the soil to die off in the winter and decay to contribute a nitrogen supply for spring planting.  Money times in our area they will still have to be tilled in the spring.