FIGURE 7.-Pneumatic methods lend themselves to applying asphalt emulsion mortar canal lining over sterilized canal subgrade. IRRIGATION IMPROVEMENTS BY REDUCING INFILTRATION Sprinkler irrigation, chemical compounds, fatty and resin soaps, and fatty acids Infiltration reduction on sandy soils would be of very material aid in reducing water losses and eliminating drainage problems caused by excessively deep percolation. Sprinkler irrigation appears to be the most practical way of reducing these losses, but this method is expensive. Chemical compounds have been used in trials on sandy soils to reduce infiltration rates but with only limited success. Fatty soaps, resin soaps, and selected fatty acids are also being studied as possible surfactants for this purpose. Wax emulsions Preliminary tests on wax emulsions as canal lining materials suggest this material might be effective in reducing infiltration rates if the average cost of 25 cents per square yard could be reduced. Effects on yield and functional deterioration due to soil reactions and cultivation will be important considerations on any type of chemical developed. Continued research is needed to develop a reliable method which will not hinder or reduce crop productions and will be inexpensive. It may be possible to achieve this goal by a process of controlling the ratio of various cations on the clay-exchange complex. There are circumstances in which it may be desirable to reduce infiltration rates on a watershed as a means of increasing runoff for municipal purposes. IRRIGATION IMPROVEMENTS BY INCREASED INFILTRATION Desirability Situations also exist in which an increase in infiltration is desirable. Two examples are the necessity to facilitate subsurface drainage of tight soils and allow oxygen to reach the root zone of crops, and to permit replenishment of ground water supplies with natural moisture as an alternate to rapid, erosive runoff. Various wetting agents which reduce surface tension and the wetting contact angle of the soil will increase infiltration rates. While effective surfactants are available for treatment of limited areas, there is a great need for materials economical for treatment of very large areas. CONTROL OF EVAPORATION FROM SOILS Sheet plastic, asphalt impregnated paper, asphalt and wax emulsions, resinous polymers and cationic asphalts Control of evaporation from soil has been successfully accomplished with sheet plastic and asphalt impregnated paper. The technique not only reduces evaporation, but it reduces weed infestation and may increase yields. It is probable that high value row crops will utilize similar means of conserving water in the future. Some of the processes developed for canal lining such as use of asphalt emulsions, wax emulsions, resinous polymers, cationic asphalts, and sprayed-in-place sealants may have merit for control of evaporation under particular circumstances. MONOMOLECULAR FILM TO REDUCE TRANSPIRATION FROM PLANTS The monomolecular film technique for reducing evaporation from ater surfaces has been applied to the problem of transpiration from ants. Hybrid corn grown in soil enriched by various amounts of tty alcohols such as hexadecanol has required up to 40 percent less ater than control plants. It is believed by some that transpiration om corn plants can safely be reduced by the blocking action of olecules of hexadecanol carried through plants and deposited at the omate water-vapor interface. Preliminary tests show no reduction yield. Further research is needed on the reaction of this chemical ith other plants and the possible deleterious effects such treated lants may have on the consumer. DIRECT-CURRENT ELECTRICAL TREATMENT OF SOILS The process of direct-current electrical treatment has been conidered for reclaiming alkali and saline-alkali soils. Field experiments ave shown some desirable effects, such as increased sodium content in drain water, accumulation of salts near the cathode, and improvenent in plant growth. Electricity alone, however, cannot be conidered a complete process of alkali soil reclamation, and leaching of vater is considered a necessity to carry away the great quantities of indesirable salts. The favorable effects of electrical treatment were hose encouraging desirable reactions within the soil-water-chemical ystem. SALINE WATER CONVERSION The current work done in the field of saline water conversion will have application to savings of water on the farm. The amount of water necessary to prevent salinization of the soil profile is proportionately related to the dissolved mineral content of the water. In many areas significant savings in water could result from reduction of the mineral content in the irrigation water. Such a decrease in the leaching requirement would make water available for other purposes or in other areas. LESS EXPENSIVE SUBSURFACE DRAINS Efficient crop production can best be obtained under well-drained soil conditions. Economic factors frequently limit the amount of drainage that can be provided under a given set of ecologic and climatic conditions. A continued search is needed in the field of less. expensive subsurface drainage. Currently holding promise, but not yet proven, is the use of plastic lined drains. REDUCTION IN SOIL COMPACTION The need for even distribution and penetration of water in the soil requires the development of equipment to reduce soil compaction. Significant differences occur in water penetration between rows which have, and have not, been subjected to compaction by farm machinery. The result is a depression in crop yield as well as greater surface runoff losses. JUTES, PLASTICS, AND CHEMICAL CANAL SEALANTS The activities of the Bureau of Reclamation and other research groups in the area of lower cost canal linings have direct application to farm irrigation. Inexpensive linings for farm laterals are needed. Research is now being done with materials such as jute, plastics, and chemical sealants. BUTYL PLASTIC PIPE FOR IRRIGATION Developments in the area of cheaper closed-pipe systems are also needed. Butyl plastic pipes hold promise of replacing more expensive aluminum gated pipes. The closed-pipe systems on irrigation farms are now usually installed in areas where climatic conditions are favorable for the production of crops yielding high net incomes per acre. Development of less expensive closed-pipe systems would see the extension of this practice to lower net income producing regions with subsequent large savings in water. MEASUREMENT OF WATER It has been estimated that 75 percent of the water used in irrigation remains unmeasured. Only a few farmers have devices for measuring the distribution of water to their individual fields. Accurate and economical measurement and distribution of water are important factors for increasing the efficiency and usefulness of available water supplies. The improvement, simplification, and development of equip ment and methods for measuring both large and small quantities would bring progress toward conservation of water resources. INSTRUMENT TO DETERMINE SOIL MOISTURE CONDITIONS Improved instrumentation is needed to assist farmers in determining when to irrigate and when to turn off the water. While several instruments aimed at meeting this objective have been developed, they have not yet attained widespread adoption by irrigators. An instrument is needed to integrate the soil moisture conditions throughout the entire root zone rather than at one, two, or three points in the soil profile. AGRICULTURAL WEATHER FORECASTING Equipment and procedural developments are needed in the area of agricultural crop forecasting. Weather observations should be made in the crop environment involved, the agricultural weather directly related to farm operations, and extension advisory service provided to show farmers how to use the weather information, and procedures established for simultaneous distribution of weather information. Extension of such practices to an irrigation project area could result in saving water on the farm and in the irrigation distribution system as well. |