Calag Archive

Soil mulching materials, ranging from plant debris to synthetic plastic films, have been used for years in agriculture to manipulate soil temperature, soil moisture and alter the physical structure of the soil. Application procedures, costs and availability of mulching materials are critical considerations to the grower. Relatively simple handling, application and disposal procedures possible with petroleum mulch offer definite advantages. Preliminary studies reported here indicate that petroleum mulch was beneficial in promoting early germination and establishing stands in a number of vegetable species.

The main reason large rates of potassium are required on cotton soils in the San Joaquin Valley, is that most of the added potassium becomes fixed within the soil and is not available to the cotton plant. This soil condition, resulting in small amounts of exchangeable potassium and large potassium-fixing capacities, may be widely prevalent within the valley, according to recent chemical and minerological analyses of many soils—and is reflected in plant deficiencies and large potassium fertilizer requirements.

Epizootic bovine abortion has caused heavy calf losses—as high as 65% in initial pregnancies—in California beef herds since 1954. Affected cows show no signs of illness, but edema, hemorrhage, and liver damage are characteristic findings in the fetus. The cause of the disease is a large virus related to the psittacosis (parrot fever) virus. There are indications that an immunity develops in cattle which abort, but attempts to prevent the disease by vaccination have not been successful thus far. Antibiotic therapy is not a practical control measure. How the virus is maintained is not yet known. If it is proven to be venereally transmitted, artificial insemination may offer the only hope of bringing the disease under control.

Since 1954, the spotted alfalfa aphid has severely damaged alfalfa in California, Arizona, and Nevada. Plant breeders and entomologists from all three states have worked to develop Sonora—a new variety, resistant to the aphid and high producing, particularly in winter and early spring. The purple-flowered, upright-growing Sonora recovers rapidly after cutting and is adapted to areas of the Southwest, formerly planted to African, where winter forage production is desired.

Uptake and utilization of sulfur by range clovers are increased by sulfur fertilization but may be limited by low temperatures, according to controlled-environment tests. If the level of available sulfur in the soil is low, higher temperatures do not appear to aid in plant uptake of sulfur. A form of sulfur with a high degree of availability would be best for greatest plant response in warm spring months—although leaching losses may occur in the event of excessive rainfall. Uptake and utilization of fertilizer sulfur was notably greater for subterraneon clover than for rose clover.

THE IMPORTANT DEHYDRATING chili pepper industry in California is located in the coastal counties from Santa Maria to San Diego. The loss of agricultural acreage in these areas is necessitating a search for new areas of production. Inland valleys of central and southern California offer extensive acreages for this crop, but differ from coastal climates by higher summer temperatures and shorter growing seasons.

In Salinas Valley trials, Great Lakes lettuce produced more than 70% of its fresh weight during the 21 days before first harvest—and absorbed over 70% of the total nutrient uptake of the crop during the same period. These results indicate that the practice of some growers using a preplant application of from one-half to two-thirds of the total amount of nitrogen to produce the crop is questionable. Since lettuce absorbs little nitrogen in the early phase of growth, a more realistic program would include preplant applications of only one-fourth the amount of total nitrogen to be used and two side-dressings to apply the balance—one after thinning and a second a month before the predicted first harvest.

Leaf-spray treatment of poinsettias with the growth retardant N-dimethylamino-succinamic acid (B995) decreased plant height without injury or increased production time, but did not result in foliage density and bract size comparable with plants treated with CCC. Both CCC and B995 were more effective in shortening plants than variable temperature-forcing treatments.