Calag Archive

Use of sprinklers to supplement the usual subbing method of irrigation increased October-harvested sugar beet production by 8.4 tons per acre. In addition to alleviating drought conditions, sprinkling increased the plant uptake of nitrogen and phosphorus from this highly organic soil.

Avocado trees are subject to fruit drop from hot weather. Field tests recently made in an avocado orchard, using overhead sprinklers for evaporational cooling, were effective in modifying air temperatures sufficiently to indicate possible control of this disorder. Temperature reductions of 5° to 7° were obtained.

The collection, cleaning, drying and storage of enough tree seeds for reforestation in California is increasingly important in today's forest management. A prime factor inhibiting seed production is insect damage. Many insect pests are not externally visible, and empty seeds or deformed or diseased embryos cannot be discovered except by seed dissection. A new highspeed X-ray technique for the rapid analysis of the proportion of sound seed is discussed in this report.

Damaging populations of spider mites in Delta field corn are most effectively controlled when acaricides are applied before injury occurs to leaves above the 3-foot level on the plants. Premature drying of the corn foliage, caused by mite infestations, reduces grain yields by increasing stalk breakage, lowering moisture content of grain at harvest and causing kernel shrinkage. Mite control has increased grain yields by 100 to 2,500 pounds per acre in recent tests. This is a progress report of experimental work and growers should contact their farm advisors or read current pesticide control bulletins for specific recommendations on mite control.

INITIAL TRIALS in 1961 comparing Piper sudan, SX-11 (a sudan x grain sorghum cross) and NK-300 (a forage sorghum) showed that there was no significant difference in total seasonal yield in dry matter production when used as pasture, although Piper outyielded the other two. When used as green chop there was no significant difference between Piper and SX-11, and both significantly outyielded NK-300. These trials were grown in 12-inch rows and harvested throughout the season as each variety reached 24 inches in height as pasture or 50% late boot stage as green chop.

Automatic irrigation, controlled by instruments capable of detecting moisture needs of plants, has been successfully used to study evapotranspiration rates for turfgrass at Riverside. Tests indicated that frequent, automatic sprinkling with relatively low-volume applications per irrigation might allow easy measurement of evapotranspiration. Tensiometers, acting as hydrostats, can turn “on” irrigation water when needed, but unpredictable flow rates in soils make it necessary to use a separate timing mechanism to set the duration or amount to be applied and turn the water off. Automatic irrigation management programs are now feasible, under many conditions, using tensiometers or other instruments responding to an energy variable of water in the soil. However, to be accurate for evapotranspiration measurements, such procedures should account for water losses below the rooting depths in the soil.

PLANTING A POTATO CROP during high temperatures in July and August is a hazardous undertaking in the San Joaquin Valley. Potato seed piece survival seems to be dependent on favorable soil and air temperatures. However, it is not uncommon to find marked differences in seed piece survival and stand of plantings made between adjacent fields with similar handling and climatic conditions.