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Beneficial soil fungus


The beneficial fungus, mycorrhizae...

Paul Zimmerman 
is an internationally known rosarian with interests in antique and heirloom roses. His Website (click on his name, above) has excellent links with information about roses, many of which do very well in our zones.

He is currently doing some research on the efficacy of using the beneficial soil fungus,
mycorrhizae, to restore the soil and ultimately the plant vigor in old rose beds. The illustration (left) shows the function of the mycorrhizae fungi as additional food gatherers for the roots of the plant. The link (below) from Zimmerman's site contains a very readable and highly informative paper available on the Website of RootGrow, a horticultural/agricultural business in England, regarding the benefits of using mycorhizzal innoculants to improve soil conditions for rose beds. 

Addressing conditions that might have led to problems in rose beds, the paper states: "Large scale soil removal and replacement is a labor intensive and costly operation and the imported soil may be of variable quality. It is also likely that imported soil will contain very few natural living beneficial organisms as it may have been stored in a large pile prior to delivery. If soil is not used by living plants then the beneficial organisms soon leach away..." 
 

Addressing conditions that might have led to problems in rose beds, the paper states: "Large scale soil removal and replacement is a labor intensive and costly operation and the imported soil may be of variable quality. It is also likely that imported soil will contain very few natural living beneficial organisms as it may have been stored in a large pile prior to delivery. If soil is not used by living plants then the beneficial organisms soon leach away..." 
 
Commenting on deep cultivation for weed control, the authors of the paper comment:"If weed control is achieved by forking over the soil in the spring, this will damage an active layer of mycorrhizal fungi down to 20cm (almost 8"). If weeds are regularly hoed off to a depth of greater than 2” or 5cm this will also damage native mycorrhizal fungi..." 

Drawing a direct line from mulch to soil health, the paper concludes: "Every year nature mulches plants through leaves falling off trees. This layer of low nutrient leaf litter is beneficial to many soil organisms, including mycorrhizal fungi, and without it the delicate balance of the soil is easily disturbed..."

The authors of the paper also comment on the problems of heavy, clayey soils: "Lack of available nutrients is particularly important on heavy clay soils, sandy soils, and soils with a low amount of organic matter or humus. The soil should always be enriched in these cases as roses are quite hungry feeders. Even in enriched soils the plant may not be able to extract enough nutrients early on in its life given its poor root system. The use of mycorrhizal fungi solves this problem..."

The entire paper is available. 

 Black Hills gardeners should know that mycorrhizae is available in small packs as a powdered innoculant for the (garden) soil and sold at several of the area greenhouses. It is also available in larger quantities (for use in planting windbreaks, for instance) in powdered form and also in a form for a root dip when planting bare root shrubs and trees from Warne Chemical in Rapid City.

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