All Issues

Since the Installation on the Davis campus of the Mark II Gamma Irradiator in 1962, research in food irradiation progressed to the point that it was desirable to begin semi-commercial test shipments involving large quantities of fruits and vegetables—to evaluate the effects of actual transit on irradiated fruits and vegetables.

The performance of solid-fuel heaters (4-lb petroleum coke bricks) was unsatisfactory only after a long rainy spell just prior to burning, and then because of difficulties at starting time. However, the quality of the material had not suffered from exposure to prolonged hot, cold, or rainy weather. Although 10 bricks give the same heat output as one oil heater, only 150 bricks per acre were needed for a temperature rise normally produced by 25 oil heaters. In calm conditions a need for extra heaters at all borders became evident. However, a reduction in number of bricks toward the center of the plot appears possible since the temperature increased constantly toward the middle of the heated area in these tests.

These tests, and other field observations, indicate that moisture is a key consideration in selecting a fertilizer program for safflower in the Valley. For dry-land soils or soils with low sub-surface moisture levels, 20 to 60 lbs per acre of N appear to be sufficient. Excess N may reduce yields. Greater amounts of N may be utilized when safflower is grown under irrigation, or on soils with a high water table, or on deep soils filled with moisture. The effect of the previous crop is important here: when safflower follows rice or sorghum, up to 150 lbs per acre of N are generally adequate. However, when it follows a nitrogen-fixing crop such as alfalfa or vetch, smaller amounts may be sufficient. No reduction in safflower yield has been observed from excess N under highmoisture conditions. Because safflower may not be irrigated, fertilizers should be placed in the moist root zone, at least 4 inches deep. If a nitrogen fertilizer is broadcast, at least 1 inch of rain or its equivalent in irrigation is needed to move it into the root zone. Spring applications are preferable to fall applications. In a dry spring, aqua or anhydrous ammonia placed at a depth of from 4 to 8 inches can be expected to be more effective than broadcast dry materials. If dry materials are to be used, applications early in the spring are desirable to take advantage of spring rains.

Growers of sprouting broccoli, Brassica oleracea var. italica, find that plants developing during the summer and fall months have a high percentage of hollow stem. These experiments were conducted in the central coastal broccoli districts of California to study hollow stem and pith discoloration in relation to growth and environmental factors. Foliar applications of the trace nutrients boron, magnesium, manganese, copper, zinc, and iron during the growth of the crop had no effect on the incidence of hollow stem and pith discoloration. Close plant spacing reduced the percentage of hollow stem. Higher rates of application of nitrogen fertilizer increased the incidence of hollow stem. The hollow stem condition begins following the initiation of the central inflorescence, the “center bud.” At first these are elliptical transverse gaps in the tissues which gradually enlarge so much that the stem is hollow as shown in the photo. There is ordinarily no discoloration of the surfaces of these openings at harvest. However, pith breakdown and discoloration may develop during shipping and marketing.

Historical Records show that the common quince rootstock has been used in Santa Clara County pear orchards since 1852, and Angers quince since the 1880's. These rootstocks were planted in a wide variety of soils—and frequently on slowly drained soils with perched ground water.

The effects of leaf-washing techniques for removal of surface contaminants were evaluated with regard to possible mineral losses that might affect orange-leaf analysis. Techniques used were: (1) nonwashed, (2) rubbing in detergent and rinsing, (3) rubbing in detergent, then dipping in 3% HCl and rinsing. Concentrations of N, P, K, Ca, and B in the leaves were not significantly affected by the washing procedures. Concentrations of Mg, Na, Cl, Zn, Mn, Cu, and Fe in or on the leaves were affected. No significant leaching losses of nutrients from the leaves were found due to washing treatments.

Although Quaking Aspen, Populus tremuloides Michaux, is not an economically important forest tree in California, it does show promise as a landscape tree, particularly because of its wide distribution and demonstrated hardiness in many climatic zones. Studies on Quaking Aspen indicate that vegetative propagation of this difficult-to-root species may be commercially feasible. Rooting of stem cuttings varies from 0 to 100% depending upon the time of year and the clone from which cuttings are taken. Cuttings treated with indolebutyric acid (IBA) have a higher rooting percentage than do the controls. Age of wood is the most important factor in rooting of Quaking Aspen. Every adventitious stem taken from root cuttings of mature trees rooted under intermittentmist conditions with IBA treatments, whereas stem cuttings from mature trees rooted only in the greenwood state. Hence, rooting of adventitious shoots may prove the best method for commercially propagating Quaking Aspen.

Numerous Unsuccessful attempts have been made to replant sites in citrus groves where trees have been infected with Armillaria mellea. The original rootstock, sweet orange, is susceptible. Some sour orange rootstocks are resistant to the disease, but cannot be recommended because of susceptibility to tristeza (quick decline). Troyer citrange and trifoliate orange are most commonly replanted now, but both are extremely susceptible to Armillaria mellea. An Ichang hybrid has shown resistance in greenhouse tests and is now being field tested.

Phosphorus fertilization increased beet yields an average of 2.6 tons per acre in five Glenn-Butte County experiments.