While engaged upon the preparation of a paper treating of the relations of the homemade windmills of our State to its agriculture, the writer finds such great and increasing demand for some short and immediate report on the subject, that he is led at the request of correspondents to publish the following brief preliminary paper, awaiting the time when a systematic and formal report may be possible.

lt is not the writer's object or intention to offer our citizens advice—for he is the one who is under instruction—but rather to bring together views of a number of mills, and to compile facts about their uses, construction, cost, and durability, which may be of possible use to prospective builders, and by which they may be enabled to select the design which seems to them least faulty, or best suited to their individual wants.

In the judgment of the writer, whose seven years of residence has enabled him to visit nearly every corner of the State, this is an important agricultural movement, and is worthy of much fuller treatment than is possible within the scope of this paper.

The importance of this movement, inaugurated by our inventive farmers, is made manifest in that many acres of garden truck, fruit land, and even farm land are irrigated; that stock is supplied with water; that ranchmen and sheep herders are benefited; that dairy products are increased and improved; and that the comfort of the village and the rural home is often enhanced. The merit of homemade mills has enjoyed such prompt recognition that they are going up daily. Not to the detriment, we are happy to say, of those important adjuncts to the farm, the shopmade mills, but in addition to them. . . .

The towns in the Platte valley are each of them oftentimes windmill centers about which are often clustered twenty to thirty or more mills of homemade design. Columbus, Grand Island, Kearney, Overton, Cozad, Lexington, Gothenburg, Ogalalla, and intermediate and adjacent towns are, in a way, each a center for homemade mills as well as other forms of water lifters. Those at Grand Island are especially numerous as may be better appreciated from the fact that we were unable to see them all after having driven for four days among the excellent mills designed and built by the German farmers living around this growing city.

As said before, the first mill sets the style in mills for a community. Accordingly in certain German settlements we find the old-fashioned Holland mills, more or less modified, until they little resemble the original or mother mill.

In other communities especially in eastern Nebraska, the Jumbo or "go-devil" mill is the prevailing form. In central Nebraska, and well to the west, the type of homemade mill known as the Battle-ax is plainly the prevailing type, and it is a first rate form of mill. Besides there are a variety of other designs to be described later in a more specific manner.

Includes 78 figures (pen & ink drawings).

Study Area Description ................................. 4

Field and laboratory Procedures. . . . . . . . . . . . . . . . . . . . . . . . . . 9

Soil and Groundwater Measurements ...................... 10

Well Water Measurements ............................... 15

Summary ............................................ 17

PONDS IN WASHINGTON AND POPE COUNTIES ................. 17

Ponds in Washington County ............................ 17

Ponds and a Lake in Pope County ......................... 25

Summary ............................................ 30

Bibliography ............................................. 31

Appendix ............................................... 34

This bulletin is one of six publications growing out of a four-and a- half-year study of nitrogen as an environmental quality factor. Although the study, including publication costs, was supported principally by a grant from the Rockefeller Foundation, the effort was initiated through a grant from the Illinois Agricultural Association. This phase of the study was supported through staff assistance provided by a number of state agencies but in particular by the Illinois Agricultural Experiment Station and the Illinois State Water Survey.

Three other bulletins in the series have been published: "Nitrates, Nitrites, and Health," Bulletin 750; "Environmental Decision Making: The Role of Community Leaders," Bulletin 756; and "Economic Effects of Controls on Nitrogen Fertilizer," Bulletin 757. One final bulletin will deal with the management of nitrogen in crop production. A book on nitrogen in relation to food, environment, and energy is also being prepared as part of the series.

E. C. Dickey is a graduate assistant and W. D. Lembke is a professor in the Department of Agricultural Engineering, College of Agriculture, University of Illinois at Urbana-Champaign.

The authors wish to thank the following people: C. D. Baker, research associate, M. D. Stone, research assistant, and E. C. Doyle, consultant, for their research contributions; L. E. Arnold, associate forester at the Dixon Springs Agricultural Center, and W. H. Walker, formerly with the Illinois State Water Survey; T. R. Peck, professor of soil chemistry, for his help with data analysis; B. Commoner, G. Shearer, and D. Kohl, with the Center for the Biology of Natural Systems, Washington University, St. Louis, Missouri, for conducting the delta 15N tests and for offering valuable suggestions; W. D. Smith, Extension adviser in Washington County; and 0. Pannier, L. Groennert, and several other farmers who, with their families, encouraged us and allowed us to conduct research on their property.

Most runoff events were infiltrated completely, resulting in no filter discharge. Runoff from larger events was partially discharged. Filters removed as much as 95% of nutrients and oxygen-demanding materials from the applied runoff on a weight basis, and 80% on a concentration basis. Removal was directly related to Dow distance or contact time with the filter. Channelized Dow with greater Dow depths required greater contact time or Dow distance than shallow overland Dow to achieve the same level of treatment.

Residue reduces erosion in two ways. First, the residue dissipates raindrop impact energy, reducing the amount of soil that is detached. Residue also forms a series of intricate obstructions or small darns that slows any flowing water. This reduces the amount of soil that can be transported. (Refer to NebGuide G8I-544, Residue Management for Soil Erosion Control, for further details on the erosion process and the benefits of residue cover.)

Historically, the term "conservation tillage" was used to describe any tillage and planting system that did not use a moldboard plow.

The current definition of conservation tillage that has been adopted by the Soil Conservation Service specifies that at least 30 percent of the soil surface must be covered with crop residue following planting to reduce soil erosion by water. So when a Conservation Plan indicates conservation tillage will be practiced, the producer has agreed to leave a minimum of a 30 percent cover after all tillage and planting operations have been completed.

Many Conservation Plans specify that crop residue cover left after planting will be the primary erosion control method. The required amount of cover ranges from 30 percent (conservation tillage) to as much as 85 percent

Today, conservation tillage systems are used to reduce preplant tillage operations, thus reducing soil erosion and moisture loss while saving labor and fuel. The label "conservation tillage" represents a broad spectrum of farming methods, and is most often defined by the amount of residue cover remaining on the soil surface. The minimum amount recommended is 20 to 30 percent after planting. Research in Nebraska and other Midwestern states has shown that leaving at least this much residue will reduce erosion by more than 50 percent of that occurring from a cleanly tilled field. To achieve effective erosion control, this minimum residue cover should be maintained during the critical soil erosion period between spring seedbed preparation and crop canopy establishment.

Conservation tillage does not necessarily require new equipment. Most conventional farm implements can be used. For corn, grain sorghum, or wheat residue, one or two passes with a field cultivator, disk, or chisel plow will usually leave more than the 20 percent minimum cover. Additional operations reduce the amount of residue, and thus reduce erosion control. Other tillage and planting systems such as ridge-plant (till-plant) and no till leave even more residue, and thus offer greater erosion control. However, no-till planting is the only method that consistently leaves the minimum surface cover in the more fragile and less abundant soybean residue.

No single tillage system is best for all situations at all times. Selecting the best tillage system for a particular soil and cropping situation requires matching the operation to the crop sequence, topography, and soil type. Rotating systems to coincide with crop rotations often provides an excellent combination. For example, a no till system could follow soybeans while a chisel or disk system might follow corn. This tillage rotation provides the best erosion control following soybeans, and provides an opportunity for some tillage in the less fragile and more abundant corn residue.

Previously, the most common tillage system included a moldboard plow to turn residue under either in the fall or spring. Following plowing, spring tillage normally included one or more shallow diskings to kill weeds, incorporate fertilizer and pesticides, and provide loose soil for seed. Other light tillage operations, including field cultivation and harrowing, were also conducted to provide a finely pulverized, weed free, seedbed. Today, preplant tillage operations are being reduced on many farms. Labor, fuel and equipment costs, better erosion control, moisture conservation, and more timely planting are all reasons for the trend toward reduced tillage operations.

The wide array of tillage and planting systems available today provides an opportunity to match the tillage system to specific soil and cropping conditions. Six different tillage systems are described here to aid in tillage system selection.

Tillage System Descriptions

Moldboard Plowing. Fall or spring moldboard plowing has been an accepted tillage operation primarily because of soil pulverization and nearly complete residue incorporation (Figure 1). When followed by one or two spring diskings, moldboard plowing provides an excellent seedbed and allows fertilizer and pesticide incorporation before planting. Even though the moldboard plow buries weed seeds, postemergent cultivation for weed control is often needed. Fall plowing also speeds up soil drying and warming in the spring, thus avoiding delays in spring tillage and planting on soils that dry slowly.

Fall moldboard plowing has often been used to reduce the number of spring tillage operations. Poor weather conditions in the spring may cause crops to be planted late because of insufficient time to plow and prepare the seedbed. The primary disadvantage of fall plowing, however, is the potential for soil erosion throughout the winter and early spring because no surface residue is available to protect the soil.

Spring plowing not only reduces the potential for wind and water erosion, but also provides winter grazing for livestock. Spring labor and time shortages, however, often offset these advantages. Furthermore, spring plowing may produce clods, which require an extra, unplanned tillage operation to develop a desirable seedbed. Excessive soil moisture loss, especially during dry years, is another disadvantage with spring plowing.

Subsoiling reduced the rate of water runoff but did not significantly reduce the soil erosion rate after equilibrium had been reached between water application and runoff rates. Surface condition and farming direction did not significantly affect runoff. However, the untilled surface treatments had about 55% less soil loss than the tilled surfaces. The contour farming direction treatments also had about 65% less soil loss than up-and-downhill farming.

Soil Factors that Affect Absorption Fields

The rate of movement of water and air through a soil, called soil permeability, is a large factor in determining how well an absorption field will function. Depth, seasonal high water table and bedrock, slope and proximity to streams or lakes are other factors that need to be considered in the layout of a septic tank and absorption field (Figure 1).

The amount of sand, silt and clay in the soil influences soil permeability. Water moves faster through sandy soils than through clay soils. However, locating an absorption field in a sandy or gravelly soil is not recommended since the septic tank effluent will not be filtered properly, especially if soil is thin and over-lies a shallow water table. Similarly, locating an absorption field in a soil having a high clay content is not recommended due to the slow permeability. Also, the clay in most Nebraska soils generally swells when wet, reducing permeability, which limits the effectiveness of the absorption field.

The depth to groundwater is an important consideration not only for groundwater protection, but also for insuring efficient operation of systems. In areas that have a seasonal high water table, sewage effluent can easily contaminate the groundwater, especially if the soil above the groundwater is sand or gravel. In other areas there may be a seasonal high water table due to a clay layer which inhibits downward flow. In this case, adding septic effluent to the soil will bring the water table even closer to the surface during the wet season. Effluent in this perched water can cause odor and result in the spread of disease.

Generally speaking, a groundwater table should be at least 4 ft (1.2 m) below the absorption field during the wettest season. Similarly, the depth of soil should be greater than 4 ft (1.2 m) from the bottom of the absorption trench to coarse sands and gravels or to bedrock. This thickness is needed for adequate filtration and purification. In sandy or gravelly soils, additional depth to the water table will help prevent contamination.

Soil slopes of less than 15 percent usually do not create a serious problem in laying out or maintaining an absorption field. However, where slope exceeds 5 to 6 percent, extra caution should be taken to place absorption trenches on the contour. On steeper slopes, laying out and maintaining absorption fields is more difficult, especially where the downward flow of effluent is intercepted by a horizontal layer of clay or rock. Interception of these flows will cause effluent to move horizontally and to seep to the soil surface.

Septic systems should be located at least 50 feet (15m) from streams or lakes. This is important to insure proper filtration and the removal of disease organisms before septic effluent reaches surface waters. Never locate an absorption field in a flood-prone area. Occasional flooding reduces the efficiency of the system, while frequent flooding could destroy its effectiveness as well as contaminate the flowing stream.

For the first rainfall event after tillage and planting, the average soil loss for all systems on the contour was 3.0 t/ha which was a 74% reduction from the average soil loss of 11.5 t/ha for tillage and planting conducted up-and-down hill. Similarly, the average soil erosion rate for systems on the contour was 9.5 t/(ha·h), a 65% reduction from the 26.2 t/(ha·h) average soil erosion rate for up-and-down hill tillage systems. All tillage systems compared showed a significant reduction in soil erosion, soil erosion rate, and sediment concentration for row direction on the contour rather than with the slope.