California Soils Research Articles

Soil phosphorus requirements for maximum growth of northern California subclover‐annual grass pastures

Abstract Annual grassland soils of California are generally quite deficient in phosphorus (P), but the amount of fertilizer P required to obtain optimum pasture production is quite variable. This paper reports on the relationships between five soil‐P tests and the amount of applied P required to obtain near maximum growth of subclovergrass pasture on 12 sites representing four soil series in the north coastal range of California. Dry matter (DM) yield response curves resulting from application of nine levels of P were fitted to the Mitscherlich equation: y = a{l‐b([EXP(‐cx)]}, where: y = DM when x = kg/ha of P were applied, a = maximum DM when P was not limiting, and b and c are constants that were adjusted to give the best fitting curves buy an iterative algorithm. This equation was used to calculate the amount of P required to bring yields to 90% of the maximum DM represented by “a”; in the equation. Then the regression equations relating P requirements to soil‐P extracted by the Bray‐1, Olsen, and modi...

Cover‐Crop‐Enhanced Water Infiltration of a Slowly Permeable Fine Sandy Loam

AbstractInfiltration improvement in many sandy to medium textured soils of California's Central Valley is often hampered by unfavorable soil properties, unfavorable management practices, and the need to protect perennial crop roots. Minimum‐tillage practices using chemical sprays, mulches, and cover crops avoid soil structure deterioration due to high traffic, but some properties of these methods are not universally acceptable. Furrow irrigation water infiltration, water use, and ‘Thompson Seedless’ grape production were evaluated on a Hanford fine sandy loam (coarse‐loamy, mixed, nonacid, thermic Typic Xerorthent) for three management systems for 2 yr to develop a useful system. The compared systems were (i) continuous cover crop [winter ‘Blando’ bromegrass (Bromus mollis L.) followed by summer resident vegetation] (CC); (ii) winter bromegrass, herbicide treated to form a summer mulch (CHT); and (iii) bare soil, herbicide treated as needed (BHT). Cumulative infiltration for 8‐h irrigation periods, averaged for five irrigations, was 177 mm for CC, 125 mm for CHT, and 74 mm for BHT during the second season. Eight‐hour cumulative infiltration was unchanged from the first year to the second for BHT but increased with CC from 107 mm to 202 mm at the first irrigation of each year; the increase for CHT was intermediate. Cover cropping between vineyard rows increased soil water depletion in the between‐row zone profile by an average of 14 mm for CHT and 27 mm for CC for each drying cycle between irrigations. Soil water depletion beneath vine rows was unchanged by treatment.

Soil Interactions with Chemical Insecticides and Nematodes Used for Control of Japanese Beetle (Coleoptera: Scarabaeidae) Larvae

Mortality of last-instar Japanese beetles, Popillia japonica Newman, was highest when exposed to isazophos, bendiocarb, and chlorpyrifos in 30-ml arenas containing California soils in laboratory assays. Carbaryl and two nematodes, Heterorhabditis bacteriophora Poinar and Steinernema glaseri (Steiner), were less effective treatments in these arenas. Soil × treatment (insecticides and nematodes) interactions were highly significant, often changing larvicide rank order of efficacy within soils. Soil characteristics identified by regression analysis as affecting insecticidal activity were organic matter (chlorpyrifos, bendiocarb, and S. glaseri ) and pH (carbaryl and isazophos). In arenas (7.6-cm diameter by 15 cm) simulating turf conditions, S. glaseri was the most effective treatment, followed by chlorpyrifos, then bendiocarb. The influence of irrigation on improving insecticide efficacy increased with higher soil organic matter. Because no treatment was completely effective against larvae, eradication of Japanese beetles cannot depend entirely on control tactics directed against the immature stages.

Assessing Health Risks Associated with DDT Residues in Soils in California: A Proposition 65 Case Study

Population growth in California has increased the pressure to convert agricultural land to commercial, industrial, or residential uses. In the ensuing property transactions, buyers and sellers must address the presence of toxic materials in soils such as pesticides, several of which are known to the State of California to cause cancer under Proposition 65. While this statute does not specifically address soil contaminants, the potential scope of its enforcement is sufficiently broad that owners of former agricultural properties may be obliged to provide warning of exposure to potential buyers, occupants, or construction workers about exposure to residues in soil from pesticide applications. However, Proposition 65 provides no guidance on how to assess exposures to chemicals in soil. The U.S. EPA Risk Assessment Guidance for Superfund (RAGS) provides a method for assessing soil-related exposure pathways that is consistent with the intent of Proposition 65. Using this approach, we have calculated the lifetime average concentrations of DDT in soil corresponding to the no-significant-risk level stipulated under Proposition 65 (1 x 10(-5)) for a hypothetical residential exposure scenario. The concentration of DDT in soil corresponding to a no-significant-risk ranges from 7.9-18.8 mg/kg, depending upon which exposure pathways are deemed to be complete for residential land use. It is argued that Proposition 65 forces the assessment and possible cleanup of such a situation through the threat of creating a health risk perception that could affect the market value of a property.

The use of a dry combustion infrared instrumental technique to determine total and organic carbon in California soils

Abstract A simple, reliable, method for determining both total and organic carbon in California soils using a dry combustion technique has been developed. Five soils of widely varying carbon contents were selected from locations in California and their total carbon and organic carbon content determined using a modified Dohrmann Carbon Analyzer (Model No. DC‐85A).The carbon analyzer was modified by the inclusion of an expansion chamber, which allowed for the determination of > 160 μg total carbon. A temperature differential method was developed to identify both the organic and, by difference, carbonate‐carbon components of each soil sample. Data obtained by this method compared favorably with determinations of organic carbon derived from a rapid dichromate oxidationlltralion technique.

Metabolism of tryptophan in soil

Production of auxins in soil is stimulated by the addition of l-tryptophan ( l-Trp) as a precursor. Metabolism of l-Trp results in the formation of many products including niacin (kynurenine pathway) and serotonin (hydroxylation) in addition to auxins and is regulated by two distinct enzymes, L-TRP-2,3-dioxygenase (TDO) and indole-2,3-dioxygenase (IDO). The roles of IDO and TDO in l-Trp metabolism and indole-3-acetic acid (IAA) formation in soil were studied by the use of bactericides and specific enzyme inhibitors. The addition of a broad spectrum bactericide, chloramphenicol, to soil resulted in a significant decrease of l-Trp catabolism and stimulated hydroxylation of l-Trp. There was no evidence in this work to support the view that l-Trp is transformed through extracellular reactions in soil. Inhibition of TDO by the addition of benzaldehyde and norharman (a potent inhibitor of TDO and IDO) also reduced l-Trp catabolism in soil. Although IAA was detected in all soils treated with bactericides or enzyme inhibitors, production of this secondary metabolite (IAA) was not reduced by blocking the kynurenine pathway or hydroxylation. Auxins were not detected in soils tested with the addition of intermediates of the TDO and IDO pathways (kynurenine and 5-hydroxytryptophan, respectively). Incubation of d-TRP as a possible auxin precursor in California soils resulted in a significant decrease in metabolism compared with l-Trp additions as measured by CO 2 evolution and HPLC analysis. Rhizosphere bacteria isolated from lettuce ( Lactuca sativa) were found to produce more IAA derived from l-Trp after they had been cultured on a medium containing l-alanine, l-asparagine and l-lysine compared with cultures that had been exposed to l-Trp or nutrient agar and then gron on a l-TRP supplemented minimal salts liquid medium. A soil which had extremely low yields of l-TRP-derived IAA increased production of auxin derivatives, including TRP-derived IAA, when incubated for 1 week with the amino acids, l-lysine, l-asparagine and l-alanine. The results suggest that synthesis of IAA in soil may not be the result of direct catabolism of l-Trp but may be linked to the cometabolism of l-Trp by the broad specificity of l-aminotransferases present in soil.

Spectral band selection for the characterization of salinity status of soils

Reflectance spectra of salt-affected surface soil samples have been measured at 10 nm spectral resolution between 495 nm and 2395 nm. The samples were collected in California (41) and in Hungary (49) to compare the effect of different salinization and alkalization processes on reflectance properties. The data set consisted of 272 spectra having 2–12 cases (repetitions) for each sample. Sixteen classes were defined based on chemical soil properties, accounting for changes in pH, electrical conductivity (EC), and exchangeable sodium percentage (ESP), of which 12 were represented in the sample. The reflectance data set was statistically analyzed using a modified stepwise principal component analysis (MSPCA) approach to select 1, 2, 3, … bands for classification of salinity status. Recognition of the above-described classification was tested by discriminant function analysis (DFA). Its results can be applied in further studies for weighing spectral bands according to their sensitivity to the chosen classification as well as in defining broad, but still potentially sufficient bands. Recognition accuracy of salinity status was 91%, 90%, and 88% with 10 nm, 20 nm, and 40 nm bands, respectively, for the entire data set. Comparison with PCA using all bands showed only slight differences. The California soil samples had more distinct spectral characteristics than the Hungarian ones. Key spectral ranges were identified in the visible (550–770 nm), near-infrared (900–1030 nm, 1270–1520 nm), and middle infrared (1940–2150 nm, 2150–2310 nm, 2330–2400 nm) portion of the spectrum at 20 nm, 40 nm, and 80 nm spectral resolution. Two of these (1270–1520 nm and 1940–2150 nm) cannot be used with satellite data due to water vapor absorption in the atmosphere. In addition, six broad bands in these ranges were identified, leading to considerably higher overall accuracy than currently available Landsat MSS, TM, and SPOT XS, in terms of spectral recognition of salinity status.

Role of copper resistance in competitive survival of Pseudomonas fluorescens in soil.

A copper-resistant strain (09906) of Pseudomonas fluorescens that was isolated from a citrus grove soil is being investigated as a biological control agent for Phytophthora root rot. Since citrus grove soils in California are often contaminated with copper from many years of copper fungicide applications, the role of copper resistance in survival of strain 09906 was investigated. Three copper-sensitive Tn5 mutants were obtained with insertions in different chromosomal DNA regions. These insertions were not in the chromosomal region that hybridized with the copper resistance operon (cop) cloned from Pseudomonas syringae. A copper-sensitive mutant survived as well as the wild type in a sterile loamy sand without added copper, but with 10 and 15 micrograms of CuSO4 added per g of soil, populations of the copper-sensitive mutant were 27- and 562-fold lower, respectively, than that of the wild type after a 25-day period. In a sterilized citrus grove soil, populations of the copper-sensitive mutant and wild-type strain were similar, but in nonsterile citrus soil, populations of the copper-sensitive mutant were 112-fold lower than the wild type after 35 days. These data suggest that copper resistance genes can be important factors in persistence of P. fluorescens in soil contaminated with copper. In addition, these genes appear to play a role in competitive fitness, even in soils with a low copper content.

Distribution of DDT residues (DDT, DDD, and DDE) in California soils

Abstract DDT residues (DDT, DDD, and DDE, or DDTR) occur in detectable concentrations in soils from southern California over 20 years after a ban (1973) on the widespread use of the pesticide in the U.S. A comparison of DDT residues found in soils from western Riverside/San Bernardino Counties to a much larger statewide database of Mischke et al. (1985) suggests that a systematic regional variation in relative abundances of DDTR exists in California soils. It is suggested that factors such as physical/chemical properties of DDT residues, local/regional soil‐forming processes, soil management practices, and climatological regimes may help to explain the observed relative abundances of DDT‐related species in California soils. Knowledge of regional trends in the concentrations and composition of soil DDTR may be useful in formulating more rational risk‐based soil management strategies where soil DDTR concentrations are at or above regulatory levels.

Viticultural soils of California, with special reference to the Napa valley

Abstract This paper provides an analysis of the soils and terroirs of the vineyards of the Napa Valley, CA. Following an overview of the geological history of the state and its effect on soil formation, a summary of the physical environment of the Napa Valley is given. This is followed by a survey of the different viticultural environments found in the Napa Valley, divided into four geographical regions. The paper argues that the natural physical environment exerts important controls on viticulture and that subtle soil differences can be reflected in the wines of the region.

Seal Formation, Runoff, and Interrill Erosion from Seventeen California Soils

Soil Science Society of America JournalVolume 57, Issue 1 p. NP-NP ErrataFree Access Seal Formation, Runoff, and Interrill Erosion from Seventeen California Soils This article corrects the following: Seal Formation, Runoff, and Interrill Erosion from Seventeen California Soils Yves Le Bissonnais, Michael J. Singer, Volume 57Issue 1Soil Science Society of America Journal pages: 224-229 First Published online: January 1, 1993 Yves Le Bissonnais, Yves Le BissonnaisSearch for more papers by this authorMichael J. Singer, Michael J. SingerSearch for more papers by this author Yves Le Bissonnais, Yves Le BissonnaisSearch for more papers by this authorMichael J. Singer, Michael J. SingerSearch for more papers by this author First published: 01 January 1993 https://doi.org/10.2136/sssaj1993.03615995005700010053xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume57, Issue1January-February 1993Pages NP-NP RelatedInformation

Interspecific Breeding for Beet Armyworm Resistance in Celery, Evaluation of Fl Hybrids

Abstract The commercial celery ‘Tall Utah’ 52-70R (Apium graveolens L.), the wild species A. prostratum spp prostratum var. filiform (A230 from Australia), and the Fl (A. graveolens X A. prostratum) were obtained from germplasm resources held at the University of California, Davis, Department of Vegetable Crops. Beet armyworm, Spodoptera exigua (Hiibner), larvae were from a laboratory colony maintained on artificial diet at 27 ± 2°C and 16:8 (L:D) photoperiod. Test plants were transplanted into 1-liter pots in University of California soil mixture on 5 March 1991 for replicate 1 and on 3 October 1991 for replicates 2 and 3, and maintained under the same moisture, light, and nutrient regimes in a greenhouse equipped with charcoal filters to remove air pollutants. A one-half strength Hoagland‘s nutrient solution was used to fertilize the plants twice per week. For each replicate, bioassays were initiated 5 months after transplanting by filling 30-ml cups containing agar gel with fresh plant parts (leaf + petiole) of each plant genotype. One neonate beet armyworm was placed in each cup, which then was capped with a plastic lid with pin-holes. The plant tissue was renewed every other day and the agar gel every week. Treatment cups were arranged as a complete block with three replicates of thirty cups per replicate, i.e. a total of 90 cups per genotype were tested. All tests were maintained in environmental chambers at 27 ± 2°C, 75% RH and 16:8 (L:D) photoperiod. Weight of larvae at 7 and 9 days, time to pupation, weight of pupae, time to adult emergence, and survivorship were recorded for each treatment.

Seal Formation, Runoff, and Interrill Erosion from Seventeen California Soils

Seal Formation, Runoff, and Interrill Erosion from Seventeen California Soils

Tryptophan-dependent biosynthesis of auxins in soil

The presence of auxins in soil may have an ecological impact affecting plant growth and development. A rapid and simple colorimetric method was used to assess California soils for their potential to produce auxins upon the addition of L-tryptophan (L-TRP). The auxin content measured by colorimetry was expressed as indole-3-acetic acid (IAA)-equivalents. A substrate (L-TRP) concentration of 5.3 g kg-1, glucose concentration of 6.7 g kg-1, no nitrogen, pH 7.0, 40°C, shaking (aeration) and 48 h incubation time were selected as standardized conditions to assay for auxin biosynthesis in soil. IAA was confirmed as a major microbial metabolite derived from L-TRP in soil by use of high performance liquid chromatography (HPLC). Under standardized conditions, L-TRP-derived auxins in 19 soils varied greatly ranging from 18.2 to 303.2 mg IAA equivalents (auxins) kg-1 soil. This study suggests that the phenotypic character of the soil microbiota has more of an influence on auxin production than the soil physicochemical properties (e.g., pH, organic C content, CEC, etc.).

Isolation of mycoparasitic species of Pythium with spiny oogonia from soil in California

Soils from 40 counties in California, at various geographical locations and elevations, were surveyed for the presence of Pythium acanthicum, P. oligandrum and P. periplocum , a group of mycoparasites that are characterized by the presence of spines on the oogonial wall. A new isolation method, employing sclerotia of Sclerotinia sclerotiorum as bait, was developed and compared with a standard dilution-plate technique. Thirty soils were used in this study. The mycoparasitic species were obtained from only 3 soils using Dilution Plate Technique (DPT) and from 26 soils using the Sclerotia Bait Technique (SBT). Only P. oligandrum was isolated by DPT, whereas the SBT yielded all 3 mycoparasitic species. An additional 63 soils were assayed with only the SBT method. The mycoparasitic species of Pythium were found in 92% of the soils studied, when taking into account the 93 soils analysed. Pythium oligandrum, P. acanthicum and P. periplocum were present in 80%, 27% and 13%, respectively, of all soils tested. Parasitism of the baited sclerotia by these mycoparasitic species was not detected. In addition, no obvious correlation was found between the occurrence of P. oligandrum, P. acanthicum and P. periplocum and type of vegetation, pH and texture of the soils analysed.

Variation in mitochondrial DNA among vegetatively compatible isolates of Fusarium oxysporum

Thirty-nine isolates of Fusarium oxysporum, obtained from agricultural field soils in California, were examined for variability in mitochondrial DNA. Thirteen isolates belonging to the same vegetative compatibility group all had the same mitochondrial DNA haplotype (C). Among 11 isolates in a second vegetative compatibility group, there were two mitochondrial DNA haplotypes, A (8 isolates) and B (3 isolates). At least three changes in length appear to be necessary to inter-convert mitochondrial DNA haplotypes A and B. To assess the potential for exchange of mitochondrial DNA haplotypes between isolates in different vegetative compatibility groups, we examined 15 isolates of F. oxysporum which collectively represented 11 pairs of weakly compatible isolates in otherwise distinct vegetative compatibility groups. In 8 of these 11 pairs the 2 isolates had different mitochondrial DNA haplotypes, either A or B; in the remaining 4 pairs both isolates had the same mitochondrial DNA haplotype. Our data indicate that weak vegetative interactions may permit transfer of mitochondria between isolates in different vegetative compatibility groups.

Modification of Infiltration Rates in an Organic‐Amended Irrigated

AbstractSlow water infiltration in some California soils results in considerable irrigation water loss through increased runoff and evaporation. This 25‐mo study was conducted to evaluate the effects of different organic amendments on soil physical parameters and water infiltration rates on an irrigated soil. Incorporation of three loadings (25 Mg ha−1 each) of poultry manure, sewage sludge, barley straw (Hordeum vulgare L.), and alfalfa (Medicago sativa L.) to an Arlington soil (coarseloamy, mixed, thermic Haplic Durixeralf) for 2 yr increased soil respiration rates (139‐290%), soil aggregate stability (22‐59%), organic C content (13‐84%), soil saccharide content (25‐41%), soil moisture content (3‐25%), and decreased soil bulk density (7‐11%). The change in soil physical properties resulted in significantly increased cumulative water infiltration rates (18‐25%) in the organic‐amended plots as compared with the unamended plots. Although additions of poultry manure and sewage sludge contributed to higher soil organic matter compared with straw and alfalfa, the straw amendment was statistically more effective in increasing soil aggregate stability, total saccharide content, infiltration rates, and soil respiration rates and in decreasing bulk density in the tillage zone. The increase in cumulative infiltration rates measured with the first organic addition (April 1987–January 1988) were significantly correlated with increased soil aggregation (P ≤ 0.01). Cumulative infiltration rates during the second (February 1988–September 1988) and third (October 1988–May 1989) organic incorporation were significantly correlated with decreased bulk density (P ≤ 0.01), but not with aggregate stability. Multiple linear regression analyses indicated that water infiltration rates in the organic‐amended soils were initially increased by stimulation of microbial activity, which increased the stability of soil aggregates. Cumulative infiltration rates were further increased by a decrease in soil bulk density with additional organic treatments to the tillage zone.

FOLIAR POTASSIUM SPRAY TIMING EFFECTS ON SEASONAL LEAF POTASSIUM AND PRODUCTIVITY OF FRENCH PRUNE (PRUNUS DOMESTICA)

Soil applied potassium (K) may not alleviate K deficiency in fine textured California soils when high numbers of prunes per tree are produced leading to leaf necrosis and limb death. Because K demand is increased by fruit, K nitrate (KN) sprays appear to be a corrective option for growers in this situation. Our objectives were to determine best seasonal KN spray liming strategies to minimize K deficiency, quantify K uptake into leaves after spray and to evaluate spray effects on productivity. Results indicated that regardless of spray timing leaf K was increased by approximately 0.3% and three weeks later decreased 0.2%. Average leaf K in sprayed trees was 0.7% higher than untreated trees at harvest. Fruit fresh to dry weight ratios were lower (better) from summer sprayed trees than spring. Summer KN sprayed trees had yield efficiencies equal to those having soil applied K. Fruit size was similar regardless of K application method. Foliar KN sprays may be a viable K augmentation to soil application in heavy crop years on fine textured soils.

Hydrologic Properties of Chaparral-Covered Soils in California

Hydrologic Properties of Chaparral-Covered Soils in California

Dissipation of s-triazines and thiocarbamates from soil as related to soil moisture content

Half-lives ( t 1 2 ) of two soil incorporated s-triazine (atrazine and prometon) and two thiocarbamate (EPTC and triallate) herbicides were determined in relation to soil moisture content in two California soils. Treated soils were incubated at three moisture levels in aerated glass vials at 25 ± 1°C and were analyzed at 0, 7, 16, 28, 56 and 112 day intervals. Loss of herbicides in all treatments followed first-order kinetics. The t 1 2 - values of all herbicides decreased with increasing soil moisture and followed an empirical equation, t 1 2 = aM −b (where t 1 2 is half-life; M the moisture content; and a and b are constants). Soil moisture had a greater effect on carbamates than on s-triazines. Prometon exhibited the longest half-life in both soils, whereas EPTC was least persistent in one soil and atrazine in another. The t 1 2 - values for atrazine, prometon, EPTC, and triallate with medium moisture levels and 10 μg/g concentration were 34·6, 43·2, 25·4 and 38·1 days in sandy loam and 26·5, 44·4, 44·1 and 25·9 days in loamy sand, respectively. Disappearance of 50% of the applied concentrations of most of the herbicide-soil combinations (except EPTC and triallate in one soil) took longer for lower initial concentrations (1 μg/g) than for higher concentrations (10 μg/g).