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Sugar as a Soil Amendment

In the unending search for new practices and procedures to increase farm productivity, the use of specific nutrients and substrates have been examined by soil scientists. Soil amendments range from gypsum for sodium exchange on the clay particles, to lime for pH shifts, to organic matter for sustained nutrient release, and a more friable soil. In the past, soil scientists have been primarily concerned with the chemical properties of the soil, and the effects of amendments, rather than being concerned with the microbial properties of fertile soil.

The determination of the effects of soil amendments upon the microbial population in the soil has been under closer examination following the publication of the book Biological Control of Plant Pathogens, by Baker and Cook. Researchers have found strong effects upon certain sclerotial pathogens from the incorporation of chitin, green soybean residue, and salt. The initial effects of the addition of these materials was found to lower the levels of pathogens, and to produce a positive growth response in a subsequent crop plantings.

Although it is clearly documented that the soil bacteria, fungi, and actinomycetes rely upon regular inputs of carbon in the form of sugars, cellulose, and long-chain carbohydrates, there is no advantage to applying large amounts of simple sugars to the soil. The soil life depends upon the chain of events which break down the complex structural components of the plant residues; the lignin, cellulose, hemicellulose building blocks which are acted upon in turn by different microorganisms in the soil community are released slowly and in a balanced way through the recycling pathways. The addition of simple sucrose to the seed row at planting time is to be avoided; there is a strong tendency of such applications to disturb the balance between the native (autochtonous) organisms, and the zymogenous organisms to the detriment of the young seedling plants. Only the zymogenous microorganisms will increase in numbers but not the autochtonous. This creates an imbalance. Different soils will also react to the immediate higher release of carbon dioxide and the subsequent lowered oxygen content of the soil. Heavier soils will be more negatively impacted in this manner.

In addition to the disturbance of the native microflora and the resulting detrimental effect upon young plants, it is also possible in soils with past damping-off problems to stimulate the development of the seedling pathogens Pythium spp. Pythium, commonly known as the "sugar fungus," which could be expected to react favorably to incorporation of sugar into the planting row, to the detriment of the crop plant.

Thirdly, in addition to disturbing the natural balance between the autochtonous and zymogenous microflora, as well as favoring Pythium as a pathogen, there is the direct effect of high amounts of sugar upon sensitive plant cells in the roots of the crop plants. Sugar would act as an osmoticum, and tend to "draw cut" the water within plant cells in close proximity to a high concentration of added sugar. Clearly then, the use of simple sugars as soil amendments is to be avoided as an agricultural practice. It is far better to supply the complex carbohydrates in the form of plant residue, and let the native soil microflora proceed with their timeless conversion processes.