All Issues

Certain types of basic information about soil-plant relations are indispensable for a sound basis for soil management. However, soils are an extremely complex body—consisting of almost endless numbers of chemical compounds and minerals, aqueous solutions, gas, and microorganisms—and are continuously changing.

In the course of a long-term fertilizer experiment with Washington Navel oranges at Riverside, studies were made—during the period 1953-1957—on the relation of tillage and fertilizer treatments to the rate of water intake by the soil and to yield and fruit quality.

Crop loss—of 20% or more—from the splitting of Navel oranges is no new problem. The trouble has plagued orange growers the world over and the general opinion seems to be that internal pressure develops within the fruit—probably as a result of extreme changes in moisture content associated with certain weather and soil moisture conditions—which ruptures the rind at the weakest point, the navel opening. Once started, the split usually expands rapidly dividing the fruit into two or more segments.

Part of the work described in the following progress report was conducted by Enrique Stein, Graduate Student in Subtropical Horticulture, University of California, Los Angeles, under the direction of Professor George F. Ryan.

Sprays have been the most effective method—to date—of supplying the micronutrients iron and zinc to many crops. Although considerable research has been done in recent years on the use of metal chelates for soil application of these two nutrients, the use of such materials is recommended only for high-value plantings. Spray application is still indicated for most crops. For this reason basic studies are being conducted on factors influencing the absorption and the subsequent translocation of these two elements.

Citrus trees utilize very little or no chlorine in their nutrition processes. They do, however, tend to accumulate chlorine in certain tissues. When such accumulations become excessive, they may cause the tissue to burn as in leaf tips and margins. In addition, the leaf size may be reduced and a fading may take place in the chlorophyll or green coloring matter of the leaves.

Populations of red mite—spider—on citrus are influenced by temperature and humidity, local air movements and weather variations.

Continuation of the third article in a series of reports of a survey of characteristics of and services offered by retail grocery stores in five counties in California made cooperatively by the Department of Home Economics, University of California, and the United States Department of Agriculture under the authority of the Research and Marketing Act as part of Western Regional Research Project WM-26.

Woolly apple aphid and green apple aphid are two of the more important pests of apple, especially in the coastal districts of northern California. Both are difficult to control because they are able to reinfest trees after spray applications.