Soil Management in Agriculture

Sustainable Agriculture
Focus on Issues Facing Farmers and Producers

The issues that are important to farmers across the country include stewardship, profitability, sustainability and the health of their community. And those are the topics to be covered in Kansas in an upcoming agriculture roundup.

The practice of sustainable agriculture is built upon soil fertility and the protection of soil health. For centuries, farmers around the world have been employing these basic techniques to keep their soil productive. Early in colonial American history, George Washington was using cover crops and manure applications on his farm. American farmers, who did not carefully tend their soil, eventually "wore it out." The Westward Expansion partly reflected the lowered productivity of eastern lands and the search for new farmland farther west.

The first publications from the Kansas State Agricultural College appeared in the late 1880's, at a time when Kansas soils had been tilled for less than fifty years. Soil scientists were well aware at that time that the long term sustainability of farming depended upon the use of legumes for fertility and the addition of organic matter for tilth. As Kansas farmers began to report declining fertility levels in the early 1900's, scientists cautioned that farmers must not rely solely upon the natural fertility of the prairie soils.

Between 1900 and 1950, Kansas State researchers guided farmers in the use of legumes and the preservation of soil organic matter. With the advent of inexpensive nitrogen fertilizers after World War II, traditional soil management techniques took a back seat to the use of commercial products that were easy to use and often provided greater economic returns in the short-term.

At the beginning of the twenty-first century, farmers are becoming increasingly conscious of the importance of soil health, water quality, and energy conservation. The rising cost of nitrogen fertilizers has revived interest in nitrogen-fixing legumes. Excess phosphorus levels in surface water indicate a need to emphasize soil conservation and the careful use of manure resources. Traditional soil management practices continue to be vital for the sustainable agriculturist and are regaining an audience with conventional agriculture.

This review of Kansas State University soil publications profiles the research and recommendations of Kansas scientists during the early to mid-twentieth century. Generally, recommended practices such as crop rotations, manure use, cover crops, and other sources of fertility are considered including the shift to commercial fertilizers in the 1950's. The special consideration of western Kansas soils is treated separately. Limited rainfall in western Kansas affects the research conducted in that part of the state and alters the use of traditional soil health practices.

Soil Health

Within every aspect of Kansas agriculture, healthy soil is a key element. Its structure and fertility provide the basis for all crop and livestock production. Throughout the historical publications of Kansas State University from the late 1800's to the mid-1900's, researchers and educators have been concerned with the protection of this vital resource.

In their 1918 publication, Soil Fertility, L.E. Call and R. I Throckmorton caution the Kansas farmer. "The soil is the most important source of wealth in an agricultural state. If it is maintained in a high state of productivity, by wise systems of soil management, the people prosper. If its fertility is wasted through careless methods of farming, both the farmer and the state suffer" (1918, Soil Fertility, p. 3).

Forty years later, in 1956, Orville Bidwell echoes this same message with its promise of a precarious wealth. "Unlike most other resources, soil is inexhaustible if properly managed." Bidwell recounts the variety of Kansas soils each with a different waterholding capacity, permeability, response to fertilizers, and susceptibility to erosion. He emphasizes that the Kansas farmer must understand the character of a particular soil in order to best manage it as an "inexhaustible" resource (1956, Major Soils of Kansas, p.3).

Decline of Kansas Soils

Throughout many of the earliest publications, the authors are clearly concerned about the declining condition of Kansas soils. By the early 1900's, much of the rich prairie soil in eastern Kansas had been farmed for 50 years. A 1903 publication from the veterinary department of the Kansas State Experiment Station states, "The fertility of the soil of the Middle states and the West is being rapidly diminished and if means are not taken to prevent it, the time is not far distant when it will be as necessary to apply artificial fertilizers to the soil as it is now in the East" (1903, Bacteria of the Soil, p. 167).

A few years later, chemists at the agricultural experiment station raised the same concern. "In the early history of Kansas no attention was paid to the composition of its soils except to boast of their inexhaustible fertility. The voice of the chemist has been lifted constantly, warning the people that this idea of possession of a fertility that is practically limitless is a delusion that can lead only to squandering of our natural resources, and to leaving posterity handicapped in the struggle for existence. To-day he is seeing his warnings justified. People in many localities of the eastern part of the state are making inquiry concerning chemical analysis of their soils with reference to learning what fertilizers should be applied and to what crops their soils are best adapted" (1910, Fertilizers and Their Use, p. 57-58).

By 1918, L.E. Call and R. I. Throckmorton attempted to put dollar figures to the losses in soil fertility. They estimated that the plant food removed from Kansas soils by wheat crops over the previous fifty-five years equaled a value of more than seven hundred million dollars. Even the wheat straw, which was regularly burned or wasted, had a value in plant nutrients of more than twelve million dollars. The majority of the wheat products were both milled and eaten outside the state which Call and Throckmorton equated with the export of soil fertility (1918, Soil Fertility, p.3).

Call and Throckmorton credited the declining productivity of Kansas soils to five factors: depletion of soil organic matter, failure to grow enough acres of leguminous crops for nitrogen fixation, depletion of mineral nutrients, the lack of proper crop rotations, and the erosion of fertile topsoil. These five factors are the subject of nearly every soils publication prior to the advent of inexpensive nitrogen fertilizers in the mid-1900's. They continue to be the basis of soil health for every farming system regardless of the use of commercial fertilizers.

Soil Organic Matter

The early Kansas State publications recognized the importance of soil organic matter to soil health. Replenishment of soil organic matter is the most basic step in addressing a number of other issues. According to Call and Throckmorton, organic matter holds the soil's store of nitrogen, provides good tilth, holds moisture, and provides food for the bacteria that make nutrients available to plants.

Soil studies in western Kansas spanning over 30 years of crop production give mention to the importance of organic matter. Progress reports in 1943 and 1957 indicate that as the organic carbon content of the soil has decreased, more power is needed for tillage, water intake is decreased, seedling emergence and root growth are hindered. The 1943 report also mentions that the presence of coarse, fibrous organic matter helped reduce wind erosion (1943, Nitrogen and Organic Carbon Changes in Soils, p. 31 and 1957, Nitrogen and Organic Carbon Changes in Cultivated Western Kansas Soils, p. 24).

Numerous publications cite frequent plowing and intensive cultivation as culprits in the loss of organic matter. Row crops depleted the soil more quickly than small grain crops. Without a regular practice of restoring organic matter, the levels of carbon in the soil would drop, threatening fertility and soil structure.

The 1918 publication, Soil Fertility, promotes barnyard manure applied to the soil as a primary source of organic matter. However, when sufficient manure is not available, the farmer should grow a crop to plow under to supply organic matter. These green manure crops may be legumes such as alfalfa, cowpeas, soybeans, clover, or sweet clover. Legumes would capture atmospheric nitrogen and fix it in the soil in addition to supplying organic matter. Non-legume crops such as rye, buckwheat, sorghum, and turnips were also cited as possible sources for organic matter (1918, Soil Fertility, p. 21).

Although most of the methods for increasing organic matter focus on the addition of green manure crops or barnyard manure, the conservation of all organic matter is addressed. Throckmorton and Call state that most wheat straw is either burned or destroyed after threshing. They recommend its use as feed and bedding for livestock. Eventually the soiled bedding and any manure would be returned to the soil. They also suggest use of the straw as a surface mulch on wheat during the winter at a rate of 1 - 1.5 tons per acre (1918, Soil Fertility, p. 20).

In 1962, farmers were again cautioned not to waste the organic matter provided by straw or stubble. In an effort to control weeds and increase yields, burning of wheat stubble had become a common practice. A series of studies in western Kansas produced data showing that stubble burning did not increase yields for subsequent crops. Not only did it present increased potential for wind erosion, it also decreased the soil's ability to absorb water (1962, Investigations of Cropping Systems, Tillage Methods, and Cultural Practices for Dryland Farming, p. 36).

Nitrogen and Organic Matter

The supply of nitrogen in the soil was closely linked to the organic matter content. The practice of returning organic matter to the soil in the form of leguminous plants or animal manures was also the method for supplying nitrogen prior to the use of commercial nitrogen fertilizer. Legume crops, grown in rotation with other crops, could be worked back into the soil as a green manure crops or the legume hay crop was fed to livestock and their manure was returned to the soil.

Off-farm sources of nitrogen in the early 1900's included waste materials from the packing houses and inorganic compounds such as saltpeter, which was mined in Chili, and manufactured compounds of ammonium sulphate or calcium cyanamide. Researchers noted that "the purchase of nitrogenous fertilizers should be limited to the meeting of special requirements of certain conditions or crops...Nitrogen...is the (nutrient) most cheaply restored, since by the cooperation of clovers, alfalfa, peas, beans, and other legumes with bacteria that grow upon their roots the abundant nitrogen of the air in the pores of the soil is brought into organic combination. This means of adding nitrogen to a soil must never be lost to view..." (1910, Fertilizers and Their Uses, p. 56).

Through the first half of the twentieth century, researchers and farmers sought to understand the best methods for capturing nitrogen with legumes especially when those crops were being used for other purposes on the farm. In 1918, researchers were concerned that the nitrogen found within the crop roots and stubble might not be significant compared with the amount removed in a hay crop. They hypothesized that a certain amount of leaf loss during the haying process might be returning some nitrogen to the soil. Still they cautioned that the best practice was to feed the hay on the farm and return all manure to the soil (1918, Soil Fertility, p. 11).

The 1939 publication on fertility studies at the Manhattan experiment station beginning in 1910 gave evidence that soil nitrogen could be increased even when the hay was removed. The average increase in the 5-9 year old hay plots was twice that for the 1-4 year plots. The researchers also found that the residual effects of the "nitrogen accumulating capacity" remained for eight to nine years following the breaking of the alfalfa sod that had been in alfalfa for more than two years (1939, Nitrogen and Organic Carbon of Soils as Influenced by Cropping Systems and Soil Treatments, p. 24-25).

But nitrogen was not the only concern when hay was taken off the farm. "If alfalfa is sold off the land it is one of the most soil-exhausting crops raised, while if it is fed on the farm, and the manure produced applied to the land, it is a conserver of fertility. The same argument applies to clover" (1914, Chemical Analysis of Some Kansas Soils, p. 641). Potassium, phosphorus, calcium and other mineral elements are taken up by the plants and must be cycled back to the soil as green manure or barnyard manure. When hay is sold off the farm, the phosphorus and potassium are more rapidly depleted than with a continuous grain crop.

Regardless of the use of green manure crops, any farm with livestock had a source of organic matter and nutrients in animal manure if it was used wisely. "If the livestock farmer properly saves and utilizes his manure he can maintain his soil in a high state of productivity, but the livestockman who feeds his cattle in woodlots along the banks of streams, and so wastes his manure, usually depletes the fertility of his soil more rapidly than the man producing grain only (1918, Soil Fertility, p. 23-24).

It was important to manage manure so that nutrients were not lost before they were cycled back to the soil. The seepage of liquid waste or urine, leaching of manure by rain and runoff water, and the "decay" of manure solids and the subsequent loss of nitrogen are all a result of poor handling techniques. Throckmorton and Call recommend that the most practical method of manure handling would be to feed the stock on the cultivated fields so that the manure is scattered by the animals and the nutrients are retained by the soil. In any case, the manure should be returned to the soil as soon as possible and long term, open storage of six months or more should be avoided (1918, Soil Fertility, p. 24).

Manure could also be used sparingly as a top dressing on corn, kafir, or winter wheat where it would act as mulch to retain moisture. If there was not a large supply of manure, it was deemed better to apply the available supply lightly to more acres rather than a heavy application on just a few acres (1918, Soil Fertility, p. 28).

As a percentage of volume, the nutrients present in manure are small. "The figures for the fertilizing constituents are always low, but they are present in readily available form and the accompanying organic matter has itself a highly beneficial effect on the land. Even with these low percentages the total amount of plant food in the manure produced on a farm reaches very significant quantities" (1910, Fertilizers and Their Uses, p. 77).

Phosphorus

Fertilizers were commonly used to provide phosphorus and other minerals long before nitrogen fertilizers were in general use. By 1918, the soils in eastern and southeast Kansas had such low stores of phosphorus that it was profitable to purchase phosphorus fertilizers. Grain farms lost phosphorus the most rapidly when it was exported off the farm with the grain. In order to retain the mineral, the farmer had to feed the grain to livestock and apply the manure to the croplands or else import a supply of phosphorus (1918, Soil Fertility, p. 10).

Alfalfa and other deep-rooted crops could be used to collect phosphorus from the subsoil. The nutrients then needed to be cycled back into the upper levels of the soil as either a green manure crop or manure from animals fed on the hay.(1918, Soil Fertility, p. 31).

Commercial sources of phosphorus included bone, basic slag, rock phosphate, and apatite (1910, Fertilizers and Their Uses, p. 54-55). Bones were a valuable product rich in phosphorus and nitrogen. They could be ground raw but they were more commonly steamed before grinding. This processing made grinding easier, concentrated the phosphorus slightly and increased the availability to plants.

Basic slag was a by-product from a particular method of iron refinement. Minerals removed from certain iron ore contained high amounts of phosphate, which could be ground for use as a fertilizer. This was not a common product in America, being chiefly available in Europe.

Primary sources of rock phosphate were found in Florida, South Carolina, and Tennessee during the early part of the twentieth century. Although it was most often used to produce superphosphate, it could be finely ground and used raw. Superphosphate was produced by treating the raw phosphate with sulphuric acid and was in use to some extent throughout the twentieth century (1910, Fertilizers and Their Uses, p. 54-55).

Although superphosphate was more readily available to the plant, Kansas State researchers advised that the raw phosphate was usually a wiser choice. "In the application of phosphate fertilizers the farmer naturally expects and desires immediate results, which are secured by the use of superphosphate, but at the same time if larger quantities of phosphates can be applied in other less soluble and available forms at the same expenditure, the ultimate value of the investment may be much greater, as the phosphorus will remain in the soil and be rendered available by slow natural processes (1910, Fertilizers and Their Uses, p. 55).

There was also indicated a positive relationship between the bacteria found in organic matter and the availability of phosphorus from raw phosphate. "The cheapest source of phosphorus is ground rock phosphate, and in this form it will be available for the use of crops if the soil is well supplied with organic matter from farm manures and legumes (1914, Chemical Analysis of Some Kansas Soils, p. 664).

Apatite, a crystal found in granite, was abundantly available in Canada. It needed to be converted to superphosphate to be used as a fertilizer.

Potassium

Potassium occurs in the mineral or rock portion of the soil. Plant roots are able to access potassium directly from tiny soil particles, chiefly silt and clay. Potassium is also present in decaying crop residues and organic matter, indicating the need, once again, for returning plant materials to the soil (1918, Soil Fertility, p. 10). A traditional source of additional potassium was hardwood ashes. Muriate of potash, a processed form of potassium in wide use today, was also available early in the twentieth century but due to the chlorine content of the compound, its use was restricted with certain crops (1910, Fertilizers and Their Use, p. 51-52).

Calcium (Lime)

Calcium, while an essential element for plant growth, was usually not deficient in Kansas soils. However, its application in the form of lime, was a common soil amendment. "(Calcium) is generally present in all cultivated soils in sufficient quantity to supply fully the need of the plant. Yet even where this is the case, the soil may be greatly in need of liming. Lime is used, therefore, as a soil amendment not so much for its effect directly on the plant as for its effect on the soil, which indirectly affects the plant. Soils that are low in lime are said to be sour" (1918, Soil Fertility, p. 38). The acidity of these soils could be neutralized by the application of calcium compounds.

A 1918 publication recommended two tons of ground limestone per acre followed by one or two tons every five to six years thereafter. The limestone should be worked into the bare ground six months to a year prior to seeding alfalfa or clovers. The effects of the limestone are slow and gradual but long lasting. The bacteria that live on the roots of alfalfa, sweet clover, and clover thrive in more alkaline soils so these crops respond well to liming. Crops considered less sensitive to acid soils were corn, wheat, timothy, and oats (1918, Soil Fertility, p. 38-40).

The change in soil pH improved the availability of phosphorus and potassium as well as improving the texture of the soil. "It is a well-known fact that soils well stocked with a supply of lime will be more productive under the same conditions of plant-food content than soils not so stocked...While soils use very small amounts of lime as compared with phosphorus and potassium, yet the presence of a relatively large supply of lime insures crop production. In the words of Hilgard, 'A lime country is a rich country'" (1914, Chemical Analysis of Some Kansas Soils, p. 647-648).

Soil Bacteria

Although the exact relationship did not seem to be clear, researchers in the early part of the twentieth century were writing about a correlation between humus or organic matter, bacteria, and fertility. A series of studies beginning in the 1890's showed crop yields in "direct proportion" to the bacterial content of the fields (1903, Bacteria of the Soil, p. 178).

In this same publication, the authors speculate that fertility depends to a large extent on bacterial activity and that by manipulating the bacteria of the soil, one might avoid the need for artificial fertilization. They proposed additional experiments to find ways to increase soil bacteria.

A few years later, Walter King and Charles Doryland report on their studies of soil bacteria with this same basic assumption. Assuming that bacterial activity indicated increased soil fertility, they set about collecting samples from various soil depths on plots representing a variety of tillage practices. They admitted tremendous variability in their data, which was collected over a period of only three months from March to June 1908. Nevertheless, they concluded that deep plowing, conveniently the tillage practice most commonly used at that time, increased bacteria levels and bacterial activity and decreased denitrification. They noted that bacterial activity increased with the temperature of the soil and decreased when the soil became saturated with moisture. Different species were predominate at different times and activity seemed to rise and fall with a regularity independent of moisture and temperature (1909, The Influence of Depth of Cultivation Upon Soil Bacteria and Their Activities, p. 161).

Analysis of the Soil

As farmers began to experience decreasing yields on exhausted soil, they began to show interest in chemical analysis of their soil. Inexpensive, reliable soil tests were not yet available in the early part of the century. Throckmorton and Call noted that although they could determine the nutrient needs of a crop and the chemical analysis of the soil, their current methods did not tell them what nutrients were available to the crop. They felt that available nutrients "fluctuate greatly" depending upon the total nutrients in the soil, the organic matter content, the weather, cultivation methods and the current crop. Consequently, a chemical analysis would only give a farmer a general outline. Probably the greatest deterrent to using a chemical analysis was the expense which made it impractical for individual farmers (1918, Soil Fertility, p. 12).

In 1909, the Extension Station council authorized the Chemistry Department to collect and analyze typical soils from across Kansas. This body of work did give farmers an idea of the basic properties of their soil and requirements of common crops even if it could not provide specific answers regarding fertility (1914, Chemical Analysis of Some Kansas Soils, p. iii).

In 1910, the Chemistry Department cautioned that chemical analysis of the soil was not a reliable indicator regarding crop needs. They recommended that the farmer should test his soil by raising small crop plots that had been "fractionally fertilized" in order to determine the optimal rates. The complexities of variable rate plots involving a significant amount of land and more than one growing season probably doomed this testing method for on-farm use.

More practical advice involved a farmer's observational skills. "Chemical and physical investigation of soils...must be supplemented or...replaced by observations upon the natural growth of trees, shrubs, grasses or weeds upon the soil, and by experiments in the production of plants or crops upon it. Let organic nature answer the question, What is this soil good for? Observations concerning the natural plant growth upon a soil have always been used by practical men in judging of its value...This means of gaining an insight into soil values is one that, while used from time immemorial, is worthy of more extended study and application (1910, Fertilizers and Their Use, p. 63).

Commercial Fertilizers

Throughout the Kansas State publications from the first half of the twentieth century, farmers are cautioned about reliance on chemical fertilizers. "It should not be forgotten...that barnyard manure, because of its content of organic matter in a state of decay, is superior to chemical fertilizers containing equal amounts of potassium, phosphorus, and nitrogen compounds" (1910, Fertilizers and Their Use, p. 67-68).

In 1918, Throckmorton and Call warned that although commercial fertilizers are more concentrated, they do not supply organic matter, which is "absolutely necessary to supply plant food, to preserve good tilth, and to retain water in the soil." Because commercial fertilizers do not supply organic matter, "they can't be expected to replace manure in soil improvement, but should be used, where they can be used profitably, in addition to barnyard manure and other forms of organic matter" (1918, Soil Fertility, p. 30). This caution continued for more than thirty years while Kansas farmers were advised to use legumes and manures as nitrogen sources and pay careful attention to nutrient cycling on their farms.

In 1956, the Kansas State Agricultural College publication, "Legumes vs. Commercial Fertilizer" documented a major change on Kansas farms. The authors reported on a study of the economics of Kansas cropping systems. One objective was to understand why farmers were planting fewer legume acres than were recommended. "Data indicate considerable advantage to certain legume rotations...Even though this is more profitable, farmers probably grow fewer legumes because they need income quickly" (1956, Legumes vs. Fertilizers, p. 12-13).

Once a farmer began using commercial fertilizers, the soil would be slow to return to a more natural cycle of fertility that did not include commercial fertilization. In 1918, farmers were already asking whether commercial fertilizers "impoverish the soil." There were reports that farmers who stopped using commercial fertilizers experienced reduced crop yields. Throckmorton and Call explained that these fertilizers "cannot in themselves be expected to maintain the fertility of the soil. They should, therefore, be used only when a good rotation of crops is practiced, and when organic matter is supplied systematically" (1918, Soil Fertility, p. 31).

Crop Rotations

In the 1910 bulletin, "Fertilizers and Their Use," the authors speculate that there is something other than the chemical analysis of the soil, which affects plant growth. They expected that rotations of crops may have an impact on "soil conditions" (1910, Fertilizers and Their Use, p. 61-62). Without fully understanding the dynamics of rotations, farmers and researchers already considered them an essential part of good soil management.

By 1935, researchers were refining their view of the use of rotations. "Rotation of crops should not be loosely recommended without stating specifically what the rotation should be, or having in mind the wide differences existing between possible rotations". Citing studies of soil fertility under various cropping patterns and soil treatments over a period of twenty years, Throckmorton and Duly emphasize that not all rotations can be used interchangeably.

Some rotations are less effective than others at maintaining soil fertility as well as at providing economic returns. In some instances, continuous cropping of hay or small grains for a few years was better for the soil or the pocketbook than rotations, which included row crops. Soil quality concerns aside, the prices of individual crops and their cost of production weigh heavily in determining the most profitable rotations. As prices fluctuate, the rotations providing the greatest economic return also vary.

During the latter half of the 1930's, an analysis of these continuing soil fertility studies in Manhattan looked at nitrogen and organic carbon levels. One conclusion was that within the cropping patterns studied, "the larger the percentage of the crop cycle occupied by biennial or perennial legumes or sod crops, the higher will be this level (of nitrogen and carbon)." The use of manure, fertilizers, and lime, if they stimulated crop growth, particularly of a legume, would maintain higher levels of nitrogen and carbon (1939, Nitrogen and Organic Carbon of Soils as Influenced by Cropping Systems and Soil Treatments, p. 24).

Wrong Turns

Besides repeated references to the importance of organic matter in retaining soil moisture, researchers have addressed other means of moisture conservation. A very early bulletin from 1899 examined the possibility that fertilizers themselves might slow water evaporation from the soil. Various treatments were tried on outdoor plots and on small pots within the laboratory over a number of years. In every case, there was no difference in treatment (1899, Soil Moisture, p.22).

Perhaps the most intriguing study was sponsored by the E.I. DuPont de Nomours Powder Company from 1911 to 1913. The dynamite industry had been heavily promoting the use of their product for improvement of all types of soils. The study included plots on heavy clay soils at the Fort Hays and Manhattan experiment stations as well as on numerous farms across the state. On a field eighty rods long and eight rods wide, thirty-inch holes were dug fifteen feet apart in rows sixteen feet apart. One half stick of dynamite was placed in each hole and exploded.

Data showed no significant differences in crop yields, soil moisture, nitrate levels, or bacterial activity on the dynamited soil. Unfortunately, the physical characteristics of the soil were considerably diminished. The explosion forced soil at the center of the charge into the surrounding pore spaces producing a cavity surrounded by a hard, compact mass. These "jugs" would fill with water during rainstorms and hold it until evaporated.

The cost was prohibitive with the dynamite expense alone at $12.20/acre. Labor was an additional $5.00/acre. The researchers concluded, "In no instance was there improvement sufficient to pay the expense of dynamiting" (1915, The Use of Dynamite in the Improvement of Heavy Clay Soils, p. 5-6).

Erosion Control

Erosion was recognized as one of the factors resulting in soil depletion. Throckmorton and Call felt erosion could be prevented by deep plowing, adding organic matter and by "working the ground at right angles to the slope of the land" (1918, Soil Fertility, p. 14). Although plowing would later be seen as a culprit in erosion, it may have offered an advantage over shallow disking by initially creating a rough surface more resistant to wind.

The merits of organic matter in stabilizing the soil were universally touted throughout early publications. However, in 1957, researchers in western Kansas reported findings indicating that increases in the soil's organic carbon content did not necessarily mean less susceptibility to wind erosion. Heavy soils could be more vulnerable with the addition of well-decomposed organic matter. Undecomposed crop residues or other organic matter were beneficial in slowing the effects of the wind (1957, Nitrogen and Organic Carbon Changes in Cultivated Western Kansas Soils, p. 25).

Farmers could create another tool to control wind erosion by alternating strips of crops. Researchers in the 50's set out to determine the ideal width of these strips for maximum protection. They considered the quantity of crop residue and soil roughness that would be produced during years of low rainfall, high wind, and low crop yields. Full wind protection during such years required strips so narrow that they would be impractical to farm. When combined with other erosion control methods such as high residue management, the field strips could be increased in size to an acceptable level and still provide a high degree of protection (1957, Width of Field Strips to Control Erosion, p. 13)

A 1962 bulletin on farming systems in western Kansas notes that contour farming resulted in increased yields for a wheat, wheat, sorghum, and barley rotation at Fort Hays. These researchers also experimented with dikes around very level fields to capture moisture and found some yield advantage (1962, Investigations of Cropping Systems, Tillage Methods, and Cultural Practices for Dryland Farming, p.37).

Western Kansas Cropping Systems

Kansas State research bulletins and publications documenting the work in western Kansas over the first half of the 1900's reflect a very different type of cropping system from that used in the eastern parts of the state. Dryland farming in areas of low rainfall and high winds presents special challenges for soil health. This flat, arid region in the western half of the state supports a fragile wealth that requires careful consideration to maintain soil resources.

Soil studies in western Kansas date back to the very earliest years of the twentieth century. A continuous study of organic carbon and nitrogen in soils at Ft. Hays Experiment Station lasted for more than thirty years with follow-up research continuing for at least another fifteen years. The western Kansas studies covered a number of topics including the use of fallow periods, changes in organic carbon and nitrogen, tillage methods, and crop rotations. In nearly every instance, the principle concerns were the conservation of soil moisture and fertility.

Fallow

Fallow is the "practice of keeping land free of all vegetation throughout one season for the purpose of storing moisture for a crop the following year (1941, Summer Fallow in Kansas, p. 5). Where rainfall is too low to support yearly crop production, fallow can be an important part of the cropping system.

Using fallow to store soil moisture results in production stability by decreasing the number of crop failures. Adherence to the fallowing pattern in high rainfall years is important since a portion of that moisture is stored for following dry years (1941, Summer Fallow in Kansas, p. 23).

In 1962, Ft. Hays researchers reported that milo yields after fallow were twice the yields of milo crops following milo. Although this was the greatest percentage increase for any crop studied, all crops saw increases (1962, Investigations of Cropping Systems, Tillage Methods, and Cultural Practices for Dryland Farming). A 1941 publication states that corn, oats, and barley grown on fallowed ground show a marked increase in quality even if the yield from one year does not equal two crops. Fallow in a rotation with forage crops "allows farms without pasture to reintegrate livestock and supplement the carrying capacity of those farms with pasture" (1941, Summer Fallow in Kansas, p. 25-26).

The successful use of fallow is related to soil type with its greatest value seen on heavier soils that have an increased moisture storage capacity. Light soils without a heavy subsoil, shallow soils, and hilly topography are not likely to provide an economic advantage with fallowing since moisture cannot be held (1941, Summer Fallow in Kansas, p. 28-29).

Soil management techniques for fallow rotations must always be directed toward capturing moisture, preventing evaporative losses, and timely destruction of weeds. The average rainfall in western Kansas may be adequate to produce a crop however the moisture losses from evaporation, runoff, and weed pressure rob a large portion of the water before it can be utilized. Throckmorton and Myers hypothesize that the farmer has little control over evaporative losses which can be 60-75% of total precipitation. "Fallow is extravagant in so far as storage of total precipitation is concerned, but it is essential as a means of stabilizing production through having sufficient moisture in the soil at seeding time to justify the seeding of a crop" (1941, Summer Fallow in Kansas, p. 13).

Tillage is a key to the successful management of runoff and weed growth. "A good summer fallow is one in which the soil is free of all growing plants throughout the fallow period and has a rough open surface which will permit a ready and rapid penetration of moisture." If possible the stubble of the preceding crop should be left standing during the winter and spring to capture snow and prevent wind erosion. Thereafter, cultivation should be used when weeds are still small and the soil will form clods to create a rough surface. To further protect the soil from wind erosion, fallow strips can be alternated with crop strips following field contours. The fallow that is poorly managed is doubly exposed to the wind. Proper management is an effective means of checking erosion (1941, Summer Fallow in Kansas, p. 14-20).

In 1962, Luebs adds that shallow cultivation using a one-way disk plow or a subsurface tillage tool is just as effective as a plow or a lister for destroying weeds. This type of tillage leaves plant residues on the surface of the soil to slow the wind action (1962, Investigations of Cropping Systems, Tillage Methods, and Cultural Practices for Dryland Farming, p. 36).

Organic matter content of western Kansas soils

General soil management techniques would indicate that increasing the organic matter content of the soil would be one tool to build its water holding capacity. Long term studies of organic carbon and nitrogen levels in soils at Colby, Hays, and Garden City provide an interesting look at organic carbon levels.

All cropping systems examined in the studies were resulting in decreases in both soil carbon and nitrogen levels. The cropping systems were generally depending upon native fertility of the soil or some applications of manure for crop production. Continuous small grain production or small grains in rotation with a fallow period showed the least destruction of soil organic matter levels. The practice of fallowing in itself decreased organic matter levels since nothing was allowed to grow on the soil but when fallow was used in a rotation with small grain crops, the losses were decreased (1957, Nitrogen and Organic Carbon Changes in Cultivated Western Kansas Soils).

The use of green manure crops to build organic matter might be considered in a higher rainfall area. However, as early as 1918, researchers warned western Kansas farmers that green manure crops would use too much moisture prior to the main crop. They recommended finding some other source of organic matter (1918, Soil Fertility, p. 23).

Sampling for the long-term studies began in 1916 and in each successive report, researchers found that applications of animal manure and/or straw slowed the loss of organic carbon and nitrogen or provided a small increase. The relationship with regard to crop yields was less positive.

In 1943, researchers reported that manure applications increased yields only under "certain conditions" and added that "perhaps (manure's) advantage will become more evident in the future (1943, Nitrogen and Carbon Changes in Soils, p. 34). In 1957 manure and straw applications showed no benefit to yield data. Citing the maintenance of nitrogen and organic matter content, researchers concluded that "these results indicate, even at the present time, that all manure should be conserved and applied to the land (1957, Nitrogen and Organic Carbon Changes in Cultivated Western Kansas Soils, p. 23).

In 1962, researchers stated the manure was of "negligible" value for wheat and sorghum in a fallow-wheat-sorghum rotation (1962, Investigations of Cropping systems, Tillage Methods, and Cultural Practices for Dryland Farming, p. 37). In 1965, after more than forty years of soil studies at the Ft. Hays Experiment Field, the researchers acknowledge that green manures and animal manure applications lower nitrogen and organic carbon losses. But they maintained that their use to maintain soil productivity "in this area is not practical" citing the need for 25-30 tons of manure per acre every three years to maintain nitrogen and carbon levels (1965, Effects of Cropping and Management of Nitrogen and Organic Carbon Contents of a Western Kansas Soil, p. 19).

The data regarding crop yields and carbon levels in these studies did not vary significantly over the course of forty years. However the conclusions regarding "practicality" are considerably different. It may be that as farming practices changed and manure was less accessible on the average farm, its use was, indeed, less practical. As livestock concentration has increased in some parts of western Kansas at the end of the twentieth century, we are once again revisiting the practicality of manure applied to cropland. Although the economics may be driven by a need to dispose of excess manure, wise use indicates the "practicality" of using those manures to build fertility and organic matter levels.

Fertility of Western Kansas Soils

"From a practical standpoint, the question of the use of nitrogen fertilizers in western Kansas presents a number of important problems." Researchers in 1943 could see that frequent crop failures and low yields were due to limiting factors other than fertility - principally moisture. They also felt that the use of summer fallow "will reduce the need (for fertilizers) due to the accumulation of nitrate nitrogen" (1943, Nitrogen and Carbon Changes in Soils, p. 33). For years they examined nitrogen changes in the soils and considered the best course for maintaining fertility at a level that permitted crop production with an economic return.

The first sixteen years of the long term soil studies at Hays, Colby, and Garden City showed nitrogen losses from 1916-1938 that were nearly equal to the nitrogen removed by the crops. The losses immediately following sod breaking were greater than the losses later in the study. For a time, there was hope that this trend indicated a possible equilibrium for nitrogen levels (1943, Nitrogen and Carbon Changes in Soils, p. 4)

Nitrogen lost through crop removal was being somewhat offset by the deposition of nitrogen in rain and snow during the fallow period. However, researchers estimated this amount to be only three to eight pounds per acre per year with an average deposition of 3.44 pounds per acre each year. They also speculated that there might be some fixation of nitrogen by free-living bacteria (Azotobacter and Clostridium) although they had not been able to verify this was true in any field experiments (1957, Nitrogen and Organic Carbon Changes in Cultivated Western Kansas Soils, p. 24).

Crop yields in these early studies fluctuated so much depending on rainfall patterns, no trend in decreasing yields due to fertility could be tracked. (1943, Nitrogen and Carbon Changes in Soils, p. 30). It is most likely that farmers were still mining the native fertility of the soil but at a much slower rate than the farmers in the eastern half of the state due to the difference in rainfall.

Considering the fragility of western Kansas cropping systems, farmers in that area need to be able to adapt their cropping patterns to fit the current conditions. "The successful dryland farmer in this area must, as far as possible, be flexible in choosing cropping sequences, tillage methods, and cultural practices". He or she must consider the weather, soil conditions, preceding crops, residue, weed populations, soil moisture, tilth, and the removal of nutrients (1962, Investigations of Cropping Systems, Tillage Methods, and Cultural Practices for Dryland Farming, p. 37).

Looking to the future of Kansas soils

Although healthy soil is the basis for the rich diversity of agriculture in Kansas, a host of barriers, both economic and social, prevent us from protecting and building soil quality. Short term leases of rented farm ground discourage the use of practices that only see an economic return after multiple years. Inexpensive commercial fertilizers have precluded the need to monitor nutrient cycling on the farm.

New interest in protecting water quality, conserving water use, managing excess livestock wastes, and developing farming systems that reduce the use of commercial fertilizers and pesticides may refocus attention on some of the same questions that were addressed during the first half of the twentieth century. Farmers may gain understanding from the early research of Kansas State University and then begin to ask the questions that will lead us into the twenty-first century with renewed interest in our soil.

The following documents have been identified as those historical publications which are relevant to sustainable agriculture in the Soil Management category.

An historical summary by Lisa French highlights the significant research and
recommendations.

Bidwell, O. W. July 1956. Major Soils of Kansas. Circular 336. Agricultural Experiment Station. K-State College of Agriculture and Applied Science.

Bray, James O. and John A. Schnittker. November 1956. Legumes or Commercial Fertilizer? Bulletin 384. Agricultural Experiment Station, Kansas State College of Agriculture and Applied Science.

Call, L.E. and Throckmorton, R.I. December 1915. The Use of Dynamite in the Improvement of Heavy Clay Soils. Bulletin 209 Agricultural Experiment Station, Kansas State Agricultural College.

Call, L.E. and Throckmorton, R.I. August 1918. Soil Fertility. Bulletin 220 Agricultural Experiment Station, Kansas State Agricultural College.

Chepil, W.S. 1957. Width of Field Strips to Control Wind Erosion. Technical Bulletin 92. Agricultural Experiment Station, Kansas State College of Agriculture and Applied Science.

Hobbs, J.A. and Brown, P.L. 1957. Nitrogen and Organic Carbon Changes in Cultivated Western Kansas Soils. Technical Bulletin 89. Agricultural Experiment Station, Kansas State College of Agriculture and Applied Science.

Hobbs, J.A. and Brown, P.L. 1965. Effects of Cropping and Management of Nitrogen and Organic Carbon Contents of a Western Kansas Soil. Technical Bulletin 144. Agricultural Experiment Station, Kansas State College of Agriculture and Applied Science.

King, W.E. and Doryland, C.J.T. August 1909. The Influence of Depth of Cultivation upon Soil Bacteria and their Activities. Bulletin161 Experiment Station, Kansas State Agricultural College.

Luebs, R.E. 1962. Investigations of Cropping Systems, Tillage Methods, and Cultural Practices for Dryland Farming. Bulletin 449. Fort Hays Branch of the Kansas Agricultural Experiment Station, Kansas State College of Agriculture and Applied Science.

Mayo, N.S. and Kinsley, A.T. May 1903. Bacteria of the Soil. Bulletin 117 Experiment Station, Kansas State Agricultural College.

Metzger, W.H. May 1939. Nitrogen and Organic Carbon of Soils as Influenced by Cropping Systems and Soil Treatments. Technical Bulletin 45. Agricultural Experiment Station, Kansas State College of Agriculture and Applied Science.

Myers, M.E., Hallsted, A.L.; Kuska, J.B.; and Haas, H.J. 1943. Nitrogen and Carbon Changes in Soils. Technical Bulletin 56. Agricultural Experiment Station, Kansas State College of Agriculture and Applied Science.

Swanson, C.O. June 1914. Chemical Analyses of some Kansas Soils. Bulletin 199 Agricultural Experiment Station, Kansas State Agricultural College.

Throckmorton, R.I. and Meyers, H.E. March 1941. Summer Fallow in Kansas. Bulletin 293 Agricultural Experiment Station, Kansas State College of Agriculture and Applied Science.

Willard, J.T. and Clothier, R.W. June 1899. Soil Moisture. Bulletin 89 Experiment Station, Kansas State Agricultural College.

Willard, J.T., Swanson, C.O., and Wiley, R.C. September 1910. Fertilizers and their Use. Bulletin169 Experiment Station, Kansas State Agricultural College

Source: Ecochem, Sustainable Agriculture