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1

Electronic Resource

Analysis and Testing of a Concentric-Disk Tension Infiltrometer (1999)

Zhang, Y. ; Smith, R. E. ; Butters, G. L. ; [et al.]

Springer

Soil Science Society of America journal 63 (1999), S. 544-553

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ISSN: 1435-0661

Source: Springer Online Journal Archives 1860-2000

Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: o )) and matric flux potential (φ(ho)) in the field without secondary measurements or explicit reliance on a specific conductivity form. Using measured pairs of K(ho) and φ(ho), a parameter estimation method is suggested to allow extrapolation of K(h) to lower than measured soil water potentials. The design of the infiltrometer and the accuracy of parameter estimation were tested against results of numerical simulations. We found that an outer-disk radius of 150 mm was sufficient to establish a 50-mm-radius inner-disk of one-dimensional (1-D) infiltration under a wide range of simulated conditions. Identification of input K(h) functions using the suggested method of analysis was excellent, although errors were introduced by nonsteady-state infiltration data. A field test of a CD infiltrometer is that, in addition to providing a rapid, direct estimate of K(h), the results are not conditional upon an assumed form of K(h) and they may be used to estimate the parameters of a K(h) form of choice.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/

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2

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Impact of irrigation timing on simulated water-crop production functions (1997)

Scheierling, Susanne M. ; Cardon, G. E. ; Young, Robert A.

Springer

Irrigation science 18 (1997), S. 23-31

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ISSN: 1432-1319

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract Estimates of the effects of alternative discrete irrigation water scheduling options on consumptive use or evapotranspiration and on crop yield are developed for a northeastern Colorado case study. The analysis proceeds from the premise that farmers, rather than considering irrigation water as a continuously variable input, tend to treat irrigations as discrete events, and make scheduling decisions as choices among numbers of irrigations of approximately equal volume. The van Genuchten-Hanks model is employed to develop a transient-state water-crop production function model. Results for two crops – corn grain and edible dry beans – are presented here. Findings are that the effect of the number of irrigations on evapotranspiration and yield per hectare varies widely, depending upon the timing of applications. When farmers can choose the optimal timing of irrigations, a reduced number of irrigations has a relatively limited adverse effect on crop production until irrigations are reduced to less than four per season. However, there are many situations in which an inability to apply water can result in a very large reduction from potential maximum yield, particularly if water is withheld early in the season and/or during the rapid growth period of the crops. In many contexts of irrigation water management, water policy analysts will wish to consider the more realistic discrete-input simulation model for policy evaluation.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s002710050041

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3

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Simulated crop production under saline high water table conditions (1991)

Bradford, S. ; Letey, J. ; Cardon, G. E.

Springer

Irrigation science 12 (1991), S. 73-77

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ISSN: 1432-1319

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Summary Many irrigated lands in semi-arid regions of the world are underlain with saline high water tables. Water management is critical to maintain crop productivity under these conditions. A multi-seasonal, transient state model was used to simulate cotton and alfalfa production under various irrigation management regimes. The variables included in-season water application of 1.0 or 0.6 potential evapotranspiration (PET), and 18 or 33 cm pre-irrigation amounts for cotton. The water table was initially at a 1.5m depth and a 9 dS/m salinity. A impermeable lower boundary at 2.5 m depth was imposed. Irrigation water salinity was 0.4 dS/m. Climatic conditions typical to the San Joaquin Valley of California were used for PET and precipitation values. The simulations were for no-lateral flow and also lateral flow whereby the water table was raised to its initial level prior to each irrigation event. Uniform application of 1.0 PET provided for relative cotton lint yields and alfalfa yields of 95% or more for at least 4 years. In-season irrigation of cotton with 0.6 PET had higher yields when associated with a 33 cm rather than an 18 cm pre-irrigation. Lateral flow provided for higher cotton lint yields production than the no-lateral flow case for each pre-irrigation treatment. The beneficial effects of lateral flow diminished with time because of the additional salt which accumulated and became detrimental to crop production. Substantial alfalfa yield reductions occurred after the first year when irrigation was set at 0.6 PET regardless of other conditions. Evaporation losses from the soil during the cotton fallow season were higher when the soil water content entering the fallow season were higher.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00190013

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4

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Effect of various irradiation treatments of plant protoplasts on the transformation rates after direct gene transfer (1990)

Köhler, F. ; Benediktsson, I. ; Cardon, G. ; [et al.]

Springer

Theoretical and applied genetics 79 (1990), S. 679-685

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ISSN: 1432-2242

Keywords: Brassica nigra ; Direct gene transfer ; Petuniahybrida ; Plasmid degradation rate ; X-ray

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary In P. hybrida and B. nigra an enhancement of transformation rates (direct gene transfer) of about six to seven-fold was obtained after irradiation of protoplasts with 12.5 Gy (X-ray). The effect of protoplast irradiation was similar in experiments where protoplasts were irradiated 1h before transformation (X-ray/DNA) or 1h after completion of the transformation procedure (DNA/X-ray). Increased X-ray doses up to 62.5 Gy resulted in further enhancement of percentages of transformed colonies, indicating a correlation between relative transformation frequencies (RTF) and the doses applied. Estimation of degradation rates of plasmid sequences in plant protoplasts yielded a reduction of plasmid concentration to 50% 8–12 h after transformation. In 1-day-old protoplasts, the level of plasmid fragments dropped to 0%–10% compared to 1h after transformation. The results demonstrate that the integration rates of plasmid sequences into the plant genome may in part be governed by DNA repair mechanisms. This could be an explanation for the observed genotypic dependence of transformation rates in different plant species and plant genotypes. Gene copy number reconstructions revealed enhanced integration rates of plasmid sequences in transformed colonies derived from irradiated protoplasts.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00226883

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Enhancement of transformation rates in higher plants by low-dose irradiation: Are DNA repair systems involved in the incorporation of exogenous DNA into the plant genome? (1989)

Köhler, F. ; Cardon, G. ; Pöhlman, M. ; [et al.]

Springer

Plant molecular biology 12 (1989), S. 189-199

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ISSN: 1573-5028

Keywords: Brassica nigra ; direct gene transfer ; Nicotiana tabacum ; Petunia hydrida ; Vigna aconitifolia ; X-ray

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Irradiation (X-ray; 5–15 Gy) of protoplasts treated with plasmid-DNA and PEG yielded higher transformation rates in comparison to non-irradiated protoplasts transformed by the same method. This could be demonstrated for four plant species. The irradiation doses used did not affect the total number of colonies regenerated without selection pressure, but resulted in 3–6-fold enhancement of hygromycin- or kanamycin-resistant colonies. Plant regeneration frequencies of transformed colonies derived from irradiated and non-irradiated protoplasts were similar in tobacco as well as in Petunia. Higher integration rates of foreign DNA as a consequence of an increased recombination machinery in irradiated cells may be responsible for the enhancement of the number of stably transformed colonies.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00020504

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6

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Soil boron and selenium removal by three plant species (1993)

Bańuelos, G. S. ; Cardon, G. E. ; Phene, C. J. ; [et al.]

Springer

Plant and soil 148 (1993), S. 253-263

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ISSN: 1573-5036

Keywords: Brassica species ; soil boron ; soil selenium ; tall fescue

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract High concentrations of boron (B) and selenium (Se) naturally found in the environment are detrimental to sustainable agriculture in the western USA. Greenhouse pot experiments were conducted to study B and Se uptake in three different plant species; Brassica juncea (L.) Czern (wild brown mustard), Festuca arundinacea Schreb. L. (tall fescue), and Brassica napus (canola) were grown in soil containing naturally occurring concentrations of 3.00 mg extractable B kg−1 and 1.17 mg total Se kg−1 soil. During the growing season, four intermediate harvests were performed on wild mustard and tall fescue. Final harvest I consisted of harvesting wild mustard, canola, and clipping tall fescue. Final harvest II consisted of harvesting wild mustard, which had been planted in soil in which wild mustard was previously grown, and harvesting previously clipped tall fescue. The greatest total amount of above ground biomass and below surface biomass was produced by tall fescue. Plants were separated into shoots and roots, weighted, and plant tissues were analyzed for total B and Se. The highest concentrations of tissue B were recovered in shoots of wild mustard and canola at final harvest I, while roots from tall fescue contained the highest concentrations of B irrespective of the harvest. Tissue Se concentrations were similar in all plants species. Soils were analyzed for residual B and Se. Extractable soil B concentrations at harvest times were lowered no less than 32% and total Se no less than 24% for all three species. The planting of wild mustard, canola, or tall fescue can reduce water-extractable B and total Se in the soil.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00012862

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