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September-October 1992

Cover: Despite the intent of the 1986 Immigration Reform and Control Act (IRCA), California farmers continue to rely on new immigrants for most field labor needs. Photo by Jack Kelly Clark

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California Agriculture, September-October 1992

Volume 46, Number 5
Most seasonal farm work still goes to new arrivals

Peer-reviewed Research Articles

Effects of immigration reform not as expected: California farmers still rely on new immigrants for field labor
by J. Edward Taylor, Dawn Thilmany
pp4-6, doi#10.3733/ca.v046n05p4
Abstract
Employer sanctions under the 1986 Immigration Reform and Control Act (IRCA) were intended to encourage US. employers to adjust to a smaller, more legal workforce. This study focuses on changing patterns of farmworker turnover and the use of farm labor contractors to test IRCA's effectiveness. The authors' findings do not support the hypothesis that IRCA would succeed in reducing California agriculture's reliance on new immigrants to meet its labor needs.
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Whitefly invasion in Imperial Valley costs growers, workers millions in losses
by Refugio A. Gonzalez, George E. Goldman, Eric T. Natwick, Howard R. Rosenberg, James I. Grieshop, Stephen R. Sutter, Tad Funakoshi, Socorro Davila-Garcia
pp7-8, doi#10.3733/ca.v046n05p7
Abstract
Two years of sweetpotato whitefly infestations in Imperial County have resulted in huge losses to growers of melons and Cole crops and in high unemployment among farmworkers. The economic impact on the county is analyzed here.
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Cracks in irrigated clay soil may allow some drainage
by Mark E. Grismer
pp9-11, doi#10.3733/ca.v046n05p9
Abstract
Cracking clay soil poses unique water management problems. Typically, clay soil is presumed to have negligible drainable pore space. Field measurements, however, suggest that there may be as much as 10% drainable pore space available, due in part to soil cracking. Such pore space may be useful in designing irrigation-drainage systems for these soils.
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Pay method affects vineyard pruner performance
by Gregory E. Billikopf, Maxwell V. Norton
pp12-13, doi#10.3733/ca.v046n05p12
Abstract
A new study indicates that vineyard pruners paid on a piece-rate basis tend to work more quickly than those paid by the hour. Pay method had little effect on pruning quality as perceived by growers, although crews paid by the hour did seem to do a slightly better job. Total pruning costs were also influenced by vine vigor and vineyard location.
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Income risk varies with what you grow, where you grow it
by Steven C. Blank
pp14-16, doi#10.3733/ca.v046n05p14
Abstract
Farmers seeking credit today are up against a lending “crunch” that is forcing them to re-assess what they grow and where they grow it. To assist those looking for new market opportunities, a new study offers ways of calculating the kinds of financial risks that concern the lenders who read today's credit applications.
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“Residue-free” tomatoes? Bush tomatoes show very low levels of pesticide residues
by Frank V. Sances, Nick C. Toscano, Lyle K. Gaston
pp17-20, doi#10.3733/ca.v046n05p17
Abstract
Do pesticide residues persist on bush tomatoes? Apparently not — or at least not much, according to a new study. When fruit was treated directly, then washed and brushed during normal postharvest handling, most — if not all — chemical residues were reduced by 50 to 95%. Extensive sampling at commercial packing facilities showed no detectable residues.
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Before-and-after tests on emitters show organic fertilizers can be injected through low-volume irrigation systems
by Lawrence J. Schwankl, Glenn McGourty
pp21-23, doi#10.3733/ca.v046n05p21
Abstract
The practice of injecting organic fertilizers into low-volume irrigation systems is not widespread, partly because of concerns that the materials will clog emitters. This study looks at two spray-dried organic fertilizers (fish protein and poultry protein) that were injected through various low-volume irrigation systems, and finds only minimal clogging and even distribution of fertilizer throughout the irrigated area.
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Cost comparison: engines vs. electric motors for irrigation pumping
by Robert G. Curley, Gerald D. Knutson
pp24-26, doi#10.3733/ca.v046n05p24
Abstract
Farmers may save money in the long run by switching from electric to diesel, natural gas, or propane-powered irrigation pumps, but fuel cost trends are hard to predict. A new computer program can help growers compare potential costs of all four irrigation power sources.
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Gophers love oak — to death
by Theodore E. Adams, William H. Weitkamp
pp27-29, doi#10.3733/ca.v046n05p27
Abstract
Weed competition, insects, and small mammals all account for oak seedling loss. High populations of pocket gophers, as at Lopez Lake County Park in San Luis Obispo County, can destroy 90% of 2 to 3-month-old transplanted valley oak seedlings in the first year. Without effective protection from pocket gophers, any control of or protection from other small mammals and control of competition may be of little value
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Environmental factors contribute to acorn quality: Elevation, on- or off-tree collection influence the viability of blue oak acorns
by Ralph L. Phillips
pp30-32, doi#10.3733/ca.v046n05p30
Abstract
Concern about the regeneration of California's native oaks has inspired several investigations that indicate acorn quality is one of many factors affecting regeneration. A survey conducted in Kern County in 7990 indicates that elevation influences blue oak and valley oak acorn quality; location with regard to water drainage is another factor for blue oak acorns.
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Editorial, News, Letters and Science briefs

EDITORIAL: Food safety: a matter of fact
by John E. Kinsella
pp2, doi#10.3733/ca.v046n05p2
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Use of saline irrigation waters and minimal leaching for crop production
by W. A. Jury, H. Frenkel, H. Fluhler, D. Devitt, L. H. Stolzy
pp169-192, doi#10.3733/hilg.v46n05p169
Abstract
An experiment in 24 lysimeters irrigated with water at three salinity levels is reported. Two crops—wheat and sorghum, were grown in the lysimeters, each of which contained one of four soil types—two clay loams and two sandy loams. Hydraulic conductivity, water potential, and water capacity were measured as functions of volumetric water content in nine of the lysimeters at the beginning of the experiment. Afterward, wheat, followed by sorghum and a second wheat crop, were grown while irrigated with water of 2.2, 4.2, or 7.1 mmho per cm electrical conductivity. There were no yield differences among treatments in the first wheat crop, because most of the growth was completed before yield-limiting levels of soil salinity were developed. Yields in the medium- and high-salinity treatments were reduced by 6 and 28 percent, respectively, compared with yield from the low-salinity treatment. Evapotranspiration was reduced 7 and 15 percent respectively, for the same treatments. Yield and evapotranspiration were substantially reduced in all treatments of the second wheat crops. The grain yield of the low-, medium-, and high-salinity irrigation treatments averaged 76, 72, and 54 percent of the corresponding yields in the first wheat crop. Salt precipitation averaged about 55 percent of the applied amount for all salinity treatments over the entire experiment. Profile salinization was still incomplete at the end of the third crop, a consequence of the low (10 percent) leaching fractions in all lysimeters.
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Use of saline irrigation waters and minimal leaching for crop production
by W. A. Jury, H. Frenkel, H. Fluhler, D. Devitt, L. H. Stolzy
pp169-192, doi#10.3733/hilg.v46n05p169
Abstract
An experiment in 24 lysimeters irrigated with water at three salinity levels is reported. Two crops—wheat and sorghum, were grown in the lysimeters, each of which contained one of four soil types—two clay loams and two sandy loams. Hydraulic conductivity, water potential, and water capacity were measured as functions of volumetric water content in nine of the lysimeters at the beginning of the experiment. Afterward, wheat, followed by sorghum and a second wheat crop, were grown while irrigated with water of 2.2, 4.2, or 7.1 mmho per cm electrical conductivity. There were no yield differences among treatments in the first wheat crop, because most of the growth was completed before yield-limiting levels of soil salinity were developed. Yields in the medium- and high-salinity treatments were reduced by 6 and 28 percent, respectively, compared with yield from the low-salinity treatment. Evapotranspiration was reduced 7 and 15 percent respectively, for the same treatments. Yield and evapotranspiration were substantially reduced in all treatments of the second wheat crops. The grain yield of the low-, medium-, and high-salinity irrigation treatments averaged 76, 72, and 54 percent of the corresponding yields in the first wheat crop. Salt precipitation averaged about 55 percent of the applied amount for all salinity treatments over the entire experiment. Profile salinization was still incomplete at the end of the third crop, a consequence of the low (10 percent) leaching fractions in all lysimeters.
PDF