Calag Archive

THE USDA'S ECONOMIC RESEARCH Service and the University of California, Davis, are cooperating in an economic analysis of the mechanical harvesting of wine grapes. Machine harvesting of grapes in California began in 1969 and expanded to over 100 machines in the 1972 harvest. Just before the 1973 harvest, an initial survey was made which included 37 growers who owned grape harvesting machines and 40 growers who used hand labor for harvesting grapes. The study analyzed the effect of substituting machines for labor, provided current information on the status of mechanization, and gave farmers some background information to help them adjust to the changing technology. Some preliminary observations are given here, from a full report to be published later this year.

POTASSIUM DEFICIENCY OF CITRUS in California had not been recognized prior to about 1960. Since then, experimental work has led to a greater understanding of potassium nutrition and the effects of potassium levels (as determined by leaf analysis) on yield and fruit quality of oranges, lemons and grapefruit.

Commonly available commercial phosphate fertilizers move very little from point of contact with the soil—resulting in inefficient utilization of surface-applied materials. An organic phosphate compound, glycerophos-phate, has been shown to move through the soil with applied irrigation water. Potential utilization advantages of glycerophosphate as a fertilizer include: possible correction of deficiencies in mid-season; application with the water in sprinkler or drip irrigation systems; and proper placement, and timing of surface applications.

When the California Aqueduct was completed, it brought high quality water from northern California to replace poor quality local well water, which usually contained high levels of boron and salts and made much of the area unsuitable for many crops. New experimental and commercial plant-ags of a variety of crops are continuing to le made to determine whether production, locality and economics warrant more extenive plantings. Grapes are one of the crops receiving wide interest. This study indicates that suitability of the area for grapes is strongly related to a relocation in soil boron, which accumulated in roils during irrigation or was present from natural causes. Boron can be removed by bleaching, although copious amounts of good duality water are needed to remove it. However, good irrigation practices with the new rater supply can be expected to reduce.iron to acceptable levels within a few years 3rd all crops in well-drained soils. Soil and land analysis can be used to evaluate the rogress in reclamation and to determine coil suitability for planting.

THE FOOD PROCESSING INDUSTRY in California uses large quantities of water, most of which becomes waste. The water contains some nutrients, such as nitrogen and phosphorus and minor elements, plus an increased salt load of two to three times that of the original water.

Germination and depth-of-emergence were studied in seven species of desert shrubs, because the shrubs are of potential use as vegetative cover on disturbed desert sites. All the shrubs germinated adequately in the laboratory. Field emergence from a depth of 1 or 2 cm (0.4 or 0.8 in.) was adequate for the four larger-seeded species, but even at 1 cm it was poor for two species and zero for the smallest-seeded species. Emergence of all species was inhibited by planting depths of 4 cm (1.6 in.) and greater.

Four desert plants species were grown in plexiglass cylinders in which thermocouple psychrometers were placed so that soil moisture potential could be measured. After establishment the plants were allowed to extract the soil moisture to -60 bars. Different samples of each were then irrigated at different time intervals to measure recovery characteristics. Partial wilting of each occurred at much lower soil moisture potentials than agricultural crops and each recovered in varying degrees for irrigation 8 to 10 days after reaching the point of -60 bars soil moisture potential. These studies of drought resistant species help understand some responses of other plants to soil moisture variations.

Atriplex hymenelytra (Torr.) Wats. (desert holly), a highly drought-resistant desert plant, was used as a test plant to study root behavior in wet and dry soils. Roots did not penetrate dry soil, but continued to grow profusely in soil having adequate soil moisture. Roots extracted water from soil progressively downward. They dried soil to -60 bars even though more water was available at a greater depth.

The information reported here is intended only as a progress report of accomplished research and does not constitute a recommendation by the University of California.