Calag Archive

High water tables and associated high salinity now hamper farm production across 400,000 acres of farmland in Fresno, Kings, Tulare and Kern Counties in the San Joaquin Valley. The two following reports describe farm demonstration projects undertaken to reduce drainwater volume while maintaining profitability. Performed at different sites under differing conditions, the projects yielded different results. An analysis of the combined results appears on page 11. (Ed.)

Cotton was produced using conventional furrow irrigation, an upgraded continuous-flow furrow design, surge irrigation, and subsurface drlp lrrlgatlon in 1987 and 1988. We found that the most economical method of reducing potential drainage at this site was to reduce the furrow length by half and decrease the set time by more than one-half during preirrigation. A subsurface drip system reduced potential drainage most effectively and increased production, but caused an overall profit loss. Subsurface drip systems may be profitable if properly designed and managed; however, a substantial yield increase or reduction in drainage disposal costs must be achieved. Otherwise, profitability of subsurface drip would be less than that for furrow irrigation systems.

Cotton was produced using subsurface drip, low-energy precision application (LEPA), scheduled furrow, and conventional furrow irrigation systems in 1989. Subsurface drip irrigation produced the highest net return to the grower through increased cotton yields. Significant water conservation was achieved with both pressurized irrigation systems (subsurface drip and LEPA). However, computer aided scheduling of furrow irrigation did not result in significant water savings. Pressurized irrigation systems may offer the flexibility and control necessary to significantly limit unnecessary water additions to the shallow groundwater table.

In this discussion of the two projects and their different results, the Five Points project is denoted as DWR, for the sponsoring California Department of Water Resources, and the Stratford project is denoted as UC, for the sponsoring UC Salinity and Drainage Task Force. (Ed.)

A recent survey of oak regeneration in four southern Sierra counties found sufficient regeneration of seedlings, but a general shortage of pole-size trees. Managers will need to find ways to encourage oak seedling recruitment into the pole-size class to ensure sustainable oak woodland stands.

During a single season, researchers compared California fresh peaches for quality and price at the producer and retail levels. While prices at both levels declined during the season, they responded differently to changes in quality characteristics. The results suggest a potential for increased revenues from marketing sweeter, more mature fruit.

Poor soil-water infiltration in the eastside of the San Joaquin Valley is frequently attributed to low-salinity irrigation water. This report assesses the feasibility of improving infiltration rates by blending the more saline westside drainwater with the less saline FriantKern Canal water, a strategy which would also provide a disposal method for westside drain water. However, the study found that boron and molybdenum concentrations in the drainwaters require large blending ratios to prevent crop yield reductions of tree crops grown along the eastside. These large blending ratios mean that the blended irrigation water may have little effect on improving filtration.

Low-input farming techniques offered energy-saving, cost-effective alternatives for resource-poor farmers of Mexican origin in the Salinas Valley. Most of these farmers currently manage small acreages using intensive vegetable cropping systems and high-input technologies.

Elm leaf beetle control efforts in northern California can be effectively timed using temperature monitoring. Two available control methods are a new biological insecticide, and an insecticide applied as a bark band. Both methods help preserve the beetle's natural enemies.

Recent increases in obscure mealybug infestations in central-coast vineyards have been associated with Argentine ant activity. Mealybug infestations were reduced by controlling these honeydew-seeking ants in the spring, using chemical treatments directed at the base of the vines. This control strategy avoids full coverage treatments disruptive to bene ficials.

No control measures are now available for reducing losses to cavity spot, the most damaging carrot disease in California. Researchers have found a fungicide that provides excellent control of the disease, though it is not yet registered for use on carrots.

Resistant rootstocks protect grape vines from phylloxera; however, a new form of this insect, Biotype B, threatens the survival of 70% of Napa and Sonoma County vineyards, those which are planted on the rootstock AxR#1. Research demonstrates that different accessions of AxR#l are equally susceptible to damage by this insect, a form of plant lice. The insect has spread from two sites in 1983 to more than 70 sites in those two counties; spread to other grapegrowing counties is likely.