Henry F. Mayland

Silicon accumulation and water uptake by wheat

Silicon (Si) content in cereal plants and soil-Si solubility may be used to estimate transpiration, assuming passive Si uptake. The hypothesis for passive-Si uptake by the transpiration stream was tested in wheat (Triticum aestivum cv. Stephens) grown on the irrigated Portneuf silt loam soil (Durixerollic calciorthid) near Twin Falls, Idaho. Treatments consisted of 5 levels of plant-available soil water ranging from 244 to 776 mm provided primarily by a line-source sprinkler irrigation system. Evapotranspiration was determined by the water-balance method and water uptake was calculated from evapotranspiration, shading, and duration of wet-surface soil. Water extraction occurred from the 0 to 150-cm zone in which equilibrium Si solubility (20°C) was 15 mg Si L−1 in the Ap and Bk (0–58 cm depth) and 23 mg Si L−1 in the Bkq (58–165 cm depth).At plant maturity, total Si uptake ranged from 10 to 32 g m−2, above-ground dry matter from 1200 to 2100 g m−2 and transpiration from 227 to 546 kg m−2. Silicon uptake was correlated with transpiration (Siup=−07+06T, r2=0.85) and dry matter yield with evapotranspiration (Y=119+303ET, r2=0.96). Actual Si uptake was 2.4 to 4.7 times that accounted for by passive uptake, supporting designation of wheat as a Si accumulator. The ratio of Si uptake to water uptake increased with soil moisture. The confirmation of active Si uptake precludes using Si uptake to estimate water use by wheat.

Utilization of globemallow (Sphaeralcea) taxa by sheep.

Globemallows (Sphaeralcea spp.) are well adapted to semiarid and arid environments. They are potentially useful as the forb component of seeding mixtures for rangeland improvement in the western states. However, the degree of acceptability of globemallow forage to livestock has not been well established. We tested 13 globemallow accessions representing 4 species and compared their utilization by sheep (Ovis aries) with that of crested wheatgrass [Agropyron cristatum (L.) Gaertn. X A. desertorum (Fisch.) Schult.] and alfalfa (Medicago sativa L.) during fall 1988 and 1989, and spring 1990 and 1991. Alfalfa consistently produced more forage per plant than wheatgrass or globemallows, and a greater portion of the alfalfa was eaten than of the other species. Sheep utilized wheatgrass more than globemallows in the fall, but the converse was true during spring pasturing. Over the 4 years, sheep ate similar proportions of wheatgrass and individual globemallows. The percentage of S. coccinea (Pursh) Rydb. forage consumed equaled that of crested wheatgrass or alfalfa in the fall but did not equal the percentage of alfalfa consumed in spring. However, S. coccinea produced much less total forage than the other species evaluated. Pre-grazing plant dry weight, dry matter content, and the occurrence of rust caused by Puccinea sherardiana Korn were negatively associated with globemallow utilization. Over-winter mortality of grazed globemallow exceeded that of ungrazed plants. Crested wheatgrass and alfalfa stands were not reduced by grazing. Globemallows are acceptable, but not highly preferred, forbs which can be seeded in environments where alfalfa and other more desirable species are not adapted.

Sulfate uptake by salinity‐tolerant plant species

High soluble-sulfate (SO4) concentrations affect water quality, soil chemistry, plant sulfur (S) levels, and possibly ruminant-animal health. The objective of this greenhouse pot study was to determine the potential for accumulating high levels of S by tansy mustard (Descurainia pinnata (Walt.) Britton), kochia (Kochia scoparia L. Schrad.), yellow sweet clover (Melilotus officinalis L.), slender wheatgrass (Elymus trachycaulus (Link) Gould ex Shinners), and sunflower (Helianthus annuus L.). Plants were grown on both a Brinegar (fine-loamy Ultic Argixeroll) and Portneuf (coarse silty Durixerollic Calciorthid) soil. Each species received five-SO4 levels. The saturation extract electrical conductivity (EC) of the cropped soils ranged from 6 to 16 dS/m, while the soluble SO4 varied from 16 to 200 mmolc/kg soil. Soil solutions were saturated or very nearly saturated with respect to gypsum at the conclusion of each study. Plant dry matter yield, except of grass growing on the non-calcareous soil, was not reduced by SO4 treatment nor by the sulfate-induced decrease in mole fraction of calcium (Ca)/(sum cations) to values less than 0.10 for kochia and grass. Sulfur concentration in the plants ranged from 2.5 mg/g in grass to 10 mg/g in mustard and for each species was linearly related to the SO4 treatment and soil-SO4 activity. Plant SO4-S values ranged from 70 µg/g in the grass to nearly 900 µg/g in mustard. Total nitrogen (N):organic S was 4.4, 7.5, 11.4, 16.5, and 5.8 for mustard, kochia, clover, grass, and sunflower, respectively. It was concluded that these species could accumulate high levels of S in the above ground tissue.

Calcium, magnesium, and potassium uptake by crested wheatgrass grown on calcareous soils

Forage intake with potassium/(calcium + magnesium) (K/(Mg + Ca)) values in excess of 2.2 are associated with grass tetany and Mg deficiencies in ruminants. This study was conducted to determine the degree to which forage K and Mg concentrations and K/(Ca + Mg) ratios could be predicted from soil bicarbonate (HCO3) extractable phosphate-phosphorus (PO4-P), and saturation extract Ca, Mg, K, sodium (Na), and nitrate-nitrogen (NO3-N) concentrations. Crested wheatgrass (Agropyron spp) strains and cultivars representing four ploidy levels were grown in the greenhouse on eight calcareous soils with differ- ent saturation extract Ca, Mg, K and K/Mg ratios. The plants were harvested three times. Soil solution 1C/(Ca + Mg) and K/Mg ratios were the only measured soil parameters that showed a consistent correlation with plant K/(Ca + Mg) ratios. Bicarbonate extractable soil P was positively related to plant P and K uptake in the first harvest, but was not related in the second and third harvests nor was soil P related to plant Ca or Mg content. There was a tendency for the higher ploidy level entries to have higher plant K/(Ca + Mg) ratios. It was concluded that soil K/(Ca + Mg) ratios can be used to predict relative forage K/(Ca + Mg) ratios for grasses grown under similar conditions.

Elemental Uptake in Relation to Root Characteristics of Tall Fescue

Abstract HiMag, an accession of tall fescue (Festuca arundinacea Schreb.), was selected for high magnesium (Mg) concentration in leaves to reduce grass tetany risk to ruminants. However, the mechanism for enhanced Mg uptake in HiMag leaves has not been determined. The objective was to investigate if increased Mg uptake in HiMag could be explained by differences in elemental distribution among plant parts, root characteristics, or organic acid concentrations compared to its parental cultivars, “Kentucky 31” (KY31) and “Missouri 96” (MO96). The study was conducted on a surface-irrigated calcareous Portneuf silt loam (coarse-silty, mixed, mesic, Durinodic Xeric Haplocalcid). Vegetation and soil cores of 7.6-cm diameter were sampled to a 45-cm soil depth in 15-cm increments. Mass and ash were determined for leaves, crowns, and roots. Leaf area, root length, root area, root length density, elemental concentration, and uptake [potassium (K), calcium (Ca), Mg, sodium (Na), and phosphorus (P)], and malate and citrate concentrations also were determined. Leaf Mg concentration was higher in HiMag than parental cultivars. HiMag generally did not differ in crown and root elemental concentrations from its parents. Risk of causing grass tetany, indicated by leaf K/(Ca + Mg), was lower in HiMag than KY31 and MO96 in both 1994 (P = 0.03) and 1995 (P = 0.01). Root length, area, and mass were not related to cation concentrations in the three tall fescue accessions, suggesting that HiMag may have an active uptake or transport mechanism for Mg. #University of Idaho Ag. Expt. Sta. No. 01709.

Element concentrations in globemallow herbage.

Globemallows (Sphaeralcea spp.) are native, drought-resistant forbs of interest for inclusion in seed mixtures for semiarid rangeland renovation. Little is known of their nutritional value for ungulates. We measured element concentrations in representative globemallow species and evaluated their adequacy for livestock nutrition. We also correlated forage selection by sheep (Ovis aries) with element concentrations. Alfalfa (Medicago sativa L.), crested wheatgrass [Agropyron cristatum (L.) Gaertn. X A. desertorum (Fisch.) Schult.], and 13 accessions of globemallows [S. coccinea (Pursh) Rydb., S. grossulariifolia (H. & A.) Rydb., S. munroana (Dougl) Spach., and S. parvifolia A. Nels.] were transplanted into replicated grazing trials in southern Idaho. Herbage was sampled and the pastures were grazed by sheep in the fall of 2 years and in the spring of the following 2 years. Concentrations of Ca and Mg in crested wheatgrass were lower than in forbs. Differences between seasons were greater than the differences among globemallow species. Forage selection ratios were positively associated with the N concentration of globemallow leaves and with the Ca:P ratio of globemallow stems but were negatively associated with stem Zn concentrations. Herbage from pastures containing crested wheatgrass with globemallows and/or alfalfa would meet the dietary element requirements of beef cattle (Bos taurus) and sheep.