All Issues

The new Cobalt-60 gamma-ray irradiator, recently installed at the Davis campus, is designed specifically for biological research. The first application of the new facility involves a study of possibilities for extending the storage life of fruits by irradiation. The irradiator has also been used in studies of genetic mutations and breeding programs for agricultural products. Desirable features for research include a large, uniform radiation field, temperature control, atmospheric modification, and safety of operation. Ten feet of de-ionized water in this pool-type unit maintains a constant radiation barrier against the 32,500 curies of Cobalt-60. The unit is one of the largest of its type in existence.

Two years of field experiments have shown that 3,4-dichloro propionanilide (DPA) can selectively control watergrass, Echinochloa crusgalli (L.) Beauv. in rice when used as a foliage spray. In 1960 yields of rice were increased by as much as 4,700 pounds per acre as a result of weed control from DPA applied at rates of 2, 4, and 8 pounds per acre. The only injuries observed were necrotic areas at the tips of rice leaves. In no case was subsequent growth of rice adversely affected by treatments.

Field studies conducted at Tule Lake provide striking evidence that ponding water is not always an efficient method of leaching. In some plots, as much as 6 acre-ft. of water per foot of soil depth was applied, yet the soil salinity was not reduced below one half of the original amount present. Of the six feet of water applied, the first one-half foot was responsible for the leaching obtained. During the winter months, 4 inches of rainfall was recorded. In this case the soil salinity was reduced by one half again, yet the quantity of water involved was 18 times less. Irrigation techniques can also be used to produce similar results. Reasons for these effects involve consideration of the structure of the soil and the variation in the pore velocity. Similar results have been found in other parts of the world. Reclamation of soils inundated by the sea in the Netherlands flood disaster of 1953 was more efficiently carried out by rainfall than by ponding.

Soil aeration is an important factor in crop production. For maximum production, optimum levels of soil oxygen must be maintained as well as plant nutrient and water supplies. Experiments are being continued to learn more about the relationships between soil aeration and plant growth and to provide information leading to management for the highest production.

Despite higher annual installation costs, benefits from use of plastic levees for rice production can result in earnings of about one and a half times the extra cost, as compared with soil levees. Increased yields per acre result from production on land otherwise taken up by soil levees. Savings in time, labor and machinery are possible in tillage and harvesting operations. Plastic levees also permit a more rapid harvest so that problems with early fall rains are minimized. Photo to left shows completed plastic rice levee with upper check flooded.

Some mixtures of pure-line varieties of self-pollinated crops show promise of improving yields and stabilizing productivity, as compared to the pure lines.

Four years of testing have shown that chemicals incorporated in the soil as pre-emergence treatments give satisfactory control of watergrass and many broad-leaved weeds in corn growing in the organic soils of the Sacramento-San Joaquin Delta. Eptam, Tillam, atrazine and Randox-T are all potentially useful chemicals. The method of incorporation in the soil and the amount of soil moisture available appear as important as the chemical selected. The least soluble materials are most handicapped by low soil moisture and inadequate mixing in the soil. The remaining task involves application equipment and fitting the use of these chemicals into the farming enterprise.

New resinous stabilizers for raw soil that will also allow water penetration for plant growth are now available. Some of these materials show pramise for control of wind or rain erosion previously possible only by a well established cover crop. New experimental formulas, found effective in the laboratory, along with others already on the market, are being field tested to determine their value in erosion control and water conservation.