Road Ditch Spraying can Contaminate Shallow Ground Water

Herbicides are the most often detected pesticides in shallow aquifers in eastern South Dakota. Since most of the people in this part of the state obtain drinking water from these shallow aquifers, there is increasing concern for aquifer water purity. In the Oakwood Lakes-Poinsett project area, Lasso was the herbicide most often detected in the aquifer, followed by 2,4-D. Tordon 22k (picloram) was second to Lasso in 1991 data from Turner County and Bowdle aquifer studies. The road ditch over the aquifer is one of the most sensitive environments to ground water pollution. This is particularly true for naturally shallow soils with only 1 to 3 feet of soil over the gravel aquifer material. In the process of building up the road, an average of 1 foot of soil is taken from the road ditch. This leaves the ditch with O to 2 feet of soil over the gravel. Thus, these road ditches are extremely sensitive to the leaching of herbicides into ground water

Drop Size Distributions from Medium-Sized Agricultural Sprinklers

THE drop size distribution of sprinkler spray is of practical importance for two reasons. First, the small droplets are subject to wind drift, distorting the application pattern. Second, large droplets possess greater kinetic energy which is transferred to the soil surface causing particle dislodgement and puddling that may result in surface crusting and runoff. The drop size distributions from medium-size agricultural sprinklers were measured to study the effects of pressure and nozzle size on the distributions. These are two parameters that farmers can change on existing systems to cope with field problems caused by low intake rates and runoff

Chapter 21: Metric Conversion

Weights and measures were among the earliest tools invented by man

Sprinkler-Induced Soil Temperature Changes Under Plant Cover

An experiment was conducted to determine the amount of soil temperature reduction to be expected from irrigating potatoes (Solanum tuberosum) at various intervals. Soil temperatures were measured at the 10-cm depth under potato ridges with various amounts of plant cover. The mean daily soil temperature at the 10-cm depth in a silt loam soil after 7 days following irrigation increased as much as 2 C above the daily irrigated plot with full cover and 4 C above the daily irrigated plot without cover. Similar soil temperature increases occurred in a loamy fine sand soil irrigated after 5 days which is the normal irrigation intervals for these soils

Air Temperature and Vapor Pressure Changes Caused by Sprinkler Irrigation

The downwind effect of evaporation from sprinkler spray was studied in the field to determine if air temperature and vapor pressure were changed enough to influence plant growth and water use. Wet-bulb and dry-bulb temperature profiles were measured upwind and at three distances downwind from a sprinkler lateral before and during sprinkling. Wind-speed and direction were also measured. Air temperature generally was reduced less than 1 C, and vapor pressure in the air was increased less than 0.8 mb. This amount of change in the air temperature and humidity is not likely to be sufficient to cause any significant change in plant growth or evaporative loss of water

Sugarbeet Yields Unaffected by Afternoon Wilting

Sugarbeet irrigation has been studied extensively in the western United States. The present "state of the art" has been reviewed by Loomis and Haddock (2) 8. Most field experiments have been run at three or more levels of soil moisture—wet, medium and dry. Differences in root and sugar yields under these moisture regimes have not been strikingly different so long as the "dry" treatment did not cause prolonged wilting, and so long as the "wet" treatment did not cause leaching of nutrients

Soil Water Uptake by Alfalfa

Water uptake patterns of alfalfa (Medicago sativa L.) assist us in understanding proposed models governing plant water uptake. The data in this paper are presented to elucidate some details of passive water uptake from profiles with nonuniform soil water distributions. Soil water content under an alfalfa seed crop was monitored with a neutron moisture probe. Alfalfa roots withdraw soil water in the lower portion of the root zone (where soil matric potentials were between —7 and —10 bars), while the upper portion of the profile was above —2 bars. This indicates that for passive water uptake to occur, large water potential differences must exist between the root xylem and the soil in the upper, moist portion of the profile. Plant water potential measurements support passive uptake

A Model for the Stray Light Contamination of the UVCS Instrument on SOHO

We present a detailed model of stray-light suppression in the spectrometer channels of the Ultraviolet Coronagraph Spectrometer (UVCS) on the SOHO spacecraft. The control of diffracted and scattered stray light from the bright solar disk is one of the most important tasks of a coronagraph. We compute the fractions of light that diffract past the UVCS external occulter and non-specularly pass into the spectrometer slit. The diffracted component of the stray light depends on the finite aperture of the primary mirror and on its figure. The amount of non-specular scattering depends mainly on the micro-roughness of the mirror. For reasonable choices of these quantities, the modeled stray-light fraction agrees well with measurements of stray light made both in the laboratory and during the UVCS mission. The models were constructed for the bright H I Lyman alpha emission line, but they are applicable to other spectral lines as well.Comment: 19 pages, 5 figures, Solar Physics, in pres

Tow Line Sprinkler Systems

A tow line sprinkler system consists of one or more sprinkler laterals made from 30 or 40 foot lengths of sprinkler tubing rigidly connected together. The laterals are towed from one set to the next with a tractor. Excluding the cost of the tractor, which is used for other farm functions, the tow line system is the most economical mechanical move system available and is convenient for pasture, hay and grain crops

Irrigation of Crops: Drainage Water Quality

Recent research has provided new knowledge on managing irrigation water to decrease the degrading effects of irrigation on the mineral quality of drainage water and to increase crop yield and quality by effective use of sprinkler irrigation. In sprinkler irrigation, water is exposed to the atmosphere, which enhances evaporation. The evaporation process cools the droplets, increases the heat absorbed by the droplets from the air through which they pass, and adds water vapor to the atmosphere. It has also been determined that the plant as well as its environment can he cooled with water applied by sprinklers