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This week's Book of the Week feature is From the Soil Up, by Donald L. Schriefer.
From Chapter 4: Tillage Principles and Systems
Fertility management is the final act in our farm show. The first three acts in the drama were the management of soil aeration, soil water and residue decay to set the stage for the last act, management of soil fertility.
We place fertility management last because we cannot have a fertile soil unless those first three acts have been done well. A soil’s fertility is judged by the response of the crop to that fertility. A crop’s response and growth is based on the balance of soil fertility and its recovery by the plant. High fertility is of little value unless it can be efficiently recovered by the crop.
We have learned the value of soil oxygen for root growth and in nutrient uptake by the roots and recognize the relationship between water management and soil fertility that makes it necessary to avoid either water excesses or deficiencies. We have a basic understanding of the many benefits bestowed upon the soil-plant system by the decay process.
We will now briefly interrupt our study of the four basics of soil management and place the study of tillage ahead of the fourth basic, soil fertility. This is done because of our belief that tillage has the greatest impact on the first three basics, soil air, soil water and decay, and is a prime prerequisite of fertility management.
Tillage affects soil aeration by its positioning of crop residue which influences its decaying process. Correct decay will impart a biological granulation of soil particles and assure soil aeration. Deeply buried residue will not decay and will deprive the soil of this natural granulation process. A barren soil surface seals over and impedes the exchange of soil gasses. Properly positioned residue has a positive effect on soil aeration by promoting decay and preventing surface sealing.
Tillage also influences water management by positioning residue to either encourage or discourage water insoak. It is tillage that creates barriers such as plow pans and it is tillage that can remove them. Tillage can either permit or prevent water insoak and penetration to storage, thus affecting its recovery by the plant.
For these reasons we believe that the tillage stage must be properly set before working on the final act, soil fertility. The final act will “make” or “break” the show, so all the props must be in place before it begins.
Development of an effective tillage system requires careful coordination of two basic areas. First, we must carefully define soil management principles. In other words, we must know precisely the tillage requirements necessary to meet the needs of the soil-plant system. Second, we must select the tools that are properly engineered to meet these carefully defined soil management requirements.
Tillage may be considered a science in the respect that it requires the knowledge and integration of the soil and plant sciences to design systems that, when used correctly, will meet the needs of each.
The primary purposes of tillage are to enhance the growing crop and, at the same time, minimize damage to the soil system. All tillage is detrimental to the soil to one degree or another, but it must be considered as a necessary evil in the growing of crops. This may come as a surprise to some, so let us briefly review the ways in which tillage damages soils.
Tillage speeds the oxidation and decomposition of organic matter by aeration of the soil. From the moment the virgin prairies were first plowed there began a slow but steady decrease in humus. The original levels of twelve to fifteen percent or even higher of humus have often been reduced to as low as four percent or less. The early sod-busters would not recognize their ash-bed soils if they could see them today. Under natural conditions soils carefully regulate their oxygen levels and were never over-exposed as they are through tillage.
Nature regulated soil aeration very carefully through residue management on the surface and also throughout the naturally firm soil horizon. The surface residue not only stopped erosion, but prevented the soil surface from sealing over. The living and dead roots provided the “wick” action needed to permit air to penetrate or exchange through an unsealed surface. This principle must be considered in the design of tillage tools and systems.
Tillage also causes rapid drying of soil which creates hardened clods and greatly influences the microbiological systems. Over-aeration, erosion, destruction of soil texture and biological fluctuations are sufficient to impress upon us that tillage is, to a degree, soil destructive.
Erosion may be the major cause of soil destruction. We believe that proper tillage is necessary for high yields on most soils. We must recognize, however, that these high yields can also be accompanied by massive soil erosion. Therefore our goal must be to obtain high yields for an indefinite length of time by managing tillage in a manner to make certain the soil-building processes exceed the soil destruction.
Therefore each tillage system must be specifically planned to enhance the management of soil air, soil water and residue decay. However, proper design and proper use are not always coordinated at the farm level. The best designed tillage tools can be misused and fail totally in their originally planned purpose. An understanding of the soil basics is essential in the effective application of properly engineered tillage tools.
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About the Author
Donald L. Schriefer passed from this life on July 30, 1998. He had spent more than five years battling acute leukemia, but he did not lie down and wait for death to come. He left this manuscript as a legacy to his lifelong friends — the farmers — knowing that those left behind would have it published.
One of America’s first “environmental agronomists,” he is best known for his consulting work on behalf of many of the country’s largest, most successful farmers. His innovation in tillage systems, foliar feeding of crops, and soil fertility management earned him the respect of both conventional and ecological farmers. He contributed frequently to various agricultural publications and was well known for conducting numerous seminars and farm programs annually.
Books by the Same Author
Agriculture in Transition – This book covers such topics as soil chemistry, plant and soil dynamics, above- and below-ground plant management, row support fertilization, zone-tillage, disc-chiseling, and more.
Buy From the Soil Up and Agriculture in Transition as a combo and save!
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