Shallow Lysimeters Research Articles

Water use, water use efficiency and drought resistance among warm-season turfgrasses in shallow soil profiles.

As the available water supply for urban turfgrass management is becoming limited in Australia, it will be crucial to identify drought-resistant turfgrass species and water-saving management strategies. Eight (pre-)commercial turfgrasses grown in Australia, two each of four species including the bermudagrasses (Cynodon dactylon L.), the Queensland blue couches (Digitaria didactyla Willd), the seashore paspalums (Paspalum vaginatum Swartz.) and St Augustinegrasses (Stenotaphrum secundatum (Walt.) Kuntze) were evaluated in two lysimeter experiments. Shallow lysimeters (28 and 40cm) were used to represent shallow soil profiles typical of urban environments. We measured gravimetric water use for the eight cultivars and calculated water use efficiency (WUE, clipping yield to water use ratio) and WUEr (ratio of WUE under drought to that under irrigated conditions). WUEr measured in both experiments correlated strongly with survival period and this relationship was not affected by soil type or cutting height. Using survival period as the criterion for drought resistance, the best were the bermudagrasses and the worst were the seashore paspalums and Queensland blue couches. The bermudagrass genotypes had the lowest water use, highest WUE and WUEr and the Queensland blue couches and seashore paspalums had the greatest water use, lowest WUE and WUEr. The possible mechanisms of drought resistance included lower water use and lower stomatal conductance as indicated by higher canopy temperature in the early stage of water deficit.

A comparison of soil moisture relations between standing and clearfelled plots with burnt and unburnt harvest residue treatments of a clonal <i>eucalypt</i> plantation on the Zululand Coastal Plain, South Africa

The effects of clearfelling and subsequent residue retention or burning on water and nutrient balances needs to be understood and quantified on forest sites that are sensitive to loss, so that the long-term sustainable productivity of such sites can be maintained and promoted. An experimental site was established in a clonal eucalypt compartment on the Zululand Coastal Plain, to compare changes in water fluxes through the mature undisturbed eucalypt stand with those after felling and re-planting, under 2 conditions: burning, and retention of the harvesting residues. The study was located in an area of high rainfall and high stand productivity, with sandy soils and low soil carbon and nutrient status; chosen so that the effects of intensive demands on water and nutrient fluxes on a potentially sensitive site could be investigated. This paper presents only the hydrological component of the study. Data collection included weekly determination of rainfall, throughfall, stemflow and soil moisture fluxes from the surface to a depth of 1 m. Drainage rates through the profile were established using time domain reflectometry probes while water drainage volumes were assessed using shallow plate lysimeters. Despite slow growth in the unfelled crop during the monitoring period (attributed to a pest infestation), soil moisture depletion remained rapid and drainage below 1 m remained low. Soil moisture was recharged within a few months after clearfelling, but became rapidly depleted as the canopy of new crop developed and approached canopy closure. A decreased wetting-front velocity and a marginally higher field capacity were proposed as evidence of pore clogging that appeared to occur during the inter-rotation period. The soil profile under the unburnt residue maintained a marginally higher soil moisture status and lower drainage than the soil profile under the burnt residue. Although soil moisture and drainage in the burnt and unburnt residue treatments became similar to the unfelled crop from canopy closure onwards, rainfall additions to soil moisture were depleted faster under the new crop during the first few months after canopy closure. Small differences in soil moisture status between the burnt and unburnt residue treatments presented here may not be sufficient to influence residue manage ment decisions. The length of the inter-rotation period and practice of residue burning may, however, need consideration where soil carbon and nutrient loss or displacement may negatively affect the sustainability of the site.

Nitrogen Fluxes through Unsaturated Zones in Five Agricultural Settings across the United States

The main physical and chemical controls on nitrogen (N) fluxes between the root zone and the water table were determined for agricultural sites in California, Indiana, Maryland, Nebraska, and Washington from 2004 to 2005. Sites included irrigated and nonirrigated fields; soil textures ranging from clay to sand; crops including corn, soybeans, almonds, and pasture; and unsaturated zone thicknesses ranging from 1 to 22 m. Chemical analyses of water from lysimeters and shallow wells indicate that advective transport of nitrate is the dominant process affecting the flux of N below the root zone. Vertical profiles of (i) nitrogen species, (ii) stable isotopes of nitrogen and oxygen, and (iii) oxygen, N, and argon in unsaturated zone air and correlations between N and other agricultural chemicals indicate that reactions do not greatly affect N concentrations between the root zone and the capillary fringe. As a result, physical factors, such as N application rate, water inputs, and evapotranspiration, control the differences in concentrations among the sites. Concentrations of N in shallow lysimeters exhibit seasonal variation, whereas concentrations in lysimeters deeper than a few meters are relatively stable. Based on concentration and recharge estimates, fluxes of N through the deep unsaturated zone range from 7 to 99 kg ha(-1) yr(-1). Vertical fluxes of N in ground water are lower due to spatial and historical changes in N inputs. High N fluxes are associated with coarse sediments and high N application rates.

Phosphorus, nitrogen and sediment losses from irrigated cropland and pasture grazed by cattle and sheep

Grazing forage crops during winter can lead to soil physical damage and contaminant losses especially on Pallic soils prone to compaction and structural degradation. A site in North Otago (Timaru silt loam) with 2 years sheep and cattle grazing on winter forage crops and pasture was used to measure phosphorus (P) and nitrogen (N) losses in sub-surface (leachate from shallow lysimeters) flow and P losses in overland flow. Keywords: phosphorus, nitrogen, sediment, irrigation, overland flow, treading, grazing, pasture, crop land

Leaching and persistence of herbicides for kudzu (Pueraria montana) control on pine regeneration sites

Clopyralid, picloram, triclopyr, metsulfuron, and tebuthiuron were applied to control kudzu on four loblolly pine forest regeneration sites during July 1997. Spot treatments were applied to recovering kudzu in June 1998 and June 1999. Soil leachate was monitored for these five herbicides from July 1997 to December 2000. All herbicides were detected in shallow (51–58 cm deep) and deep lysimeters (84–109 cm deep). Clopyralid was not persistent and limited leaching occurred, with residue levels of 0.4 to 2.8 μg L−1in 12 of 102 deep lysimeter samples. Picloram was mobile and persisted at 0.6 to 2.5 μg L−1in shallow and deep lysimeters for at least 10 mo after the initial application. Triclopyr residues were not persistent in shallow lysimeters and remained < 6 μg L−1during the study. Metsulfuron persisted at < 0.1 μg L−1for 182 to 353 d in shallow lysimeters and at < 0.07 μg L−1for 182 to 300 d in the deep lysimeters in various plots. Tebuthiuron peaks in the deep lysimeters ranged from 69 to 734 μg L−134 to 77 d after the first spot treatment. In the soil that was essentially a fill area, tebuthiuron residues remained > 400 μg L−1(402–1,660 μg L−1) in the shallow lysimeter samples and > 180 μg L−1(181–734 μg L−1) in the deep lysimeters throughout a 354-d period that followed the first spot application. When used as part of a forest regeneration program, the relative potentials of the herbicides to move into shallow groundwater were: tebuthiuron > picloram > metsulfuron > clopyralid > triclopyr.

Radionuclide Transport Above a Near‐Surface Water Table: IV. Soil Migration and Crop Uptake of Chlorine‐36 and Technetium‐99, 1990 to 1993

Vertical distributions of (36)Cl and (99)Tc are presented from deep and shallow lysimeters above artificially controlled water tables for a 4-yr experiment from 1990 to 1993. Activity concentration profiles were all measured in late summer when a winter wheat (Triticum aestivum L. cv. Pastiche) crop was harvested. After harvest, activity concentrations in different organs of the crop were determined and crop uptake quantified as both an inventory ratio (IR) and a transfer factor (TF(w)), weighted to account for differential root and radionuclide distributions within the soil profile. Vertical distributions of radionuclides, crop roots within the soil, and IR and TF(w) values were each subjected to analysis of variance to estimate the individual and combined effects of soil depth and the year of the experiment on the results obtained. Chlorine-36 and (99)Tc exhibited highly significant variations in activity concentrations with soil depth and from year to year, indicating considerable physical mobility of both radionuclides. Soil-to-plant transfer was also high for both radionuclides compared with data obtained for gamma-emitting radionuclides. The IR values indicated that up to 40% of (36)Cl was incorporated in the crop's tissues at harvest, compared with a maximum of less than 1% for the less mobile gamma-emitting radionuclides. On the basis of the TF(w) values determined, (36)Cl uptake by winter wheat exceeded (99)Tc uptake, indicating that (36)Cl is highly bioavailable. Factors controlling the migration and bioavailability of both (36)Cl and (99)Tc in soils are discussed.

Fate of Steroidal Hormones During Soil‐Aquifer Treatment

AbstractThere is increasing concern that endocrine disrupting compounds such as steroidal hormones present in treated waste water effluents can affect ground water quality where waste water is used to recharge local ground water. Little is known how efficiently steroidal hormones are removed or transformed during percolation through the subsurface. The scope of this study was to examine the fate of hormones during soil‐aquifer treatment (SAT) leading to ground water recharge in controlled laboratory soil‐column studies and at two water reuse field sites where treated waste water is fed to ground water recharge basins. The selected steroidal hormones represented estrogens (17β‐estradiol and estriol) and androgens (testosterone). Composite samples of treated waste water and from ground water monitoring wells were collected and analyzed for steroidal hormones using enzyme‐linked immunosorbent assays. The study revealed that the mobility of the selected hormones in subsurface systems was low, and estriol and testosterone were both not detected (< 0.6 ng/L) in ground water monitoring wells or shallow lysimeters representing water samples after 1.5 m of travel through porous media. 17β‐estradiol, however, was consistently detected at concentrations < 2 ng/L in monitoring wells after travel of 1.5 m through porous media. Results from field sites that have been operational for more than 13 years indicated no breakthrough of the target compounds in ground water samples collected downstream of the surface spreading operation. These findings were confirmed by controlled laboratory studies simulating SAT in soil‐column experiments. It appeared that the majority of attenuation was due to adsorption of the three target compounds to the porous media matrix, and additional attenuation to below the detection limit occurred due to the presence of bioactivity regardless of dominating redox conditions (aerobic vs. anoxic) or the type of organic carbon matrix present (hydrophobic acids, hydrophilic carbon vs. colloidal carbon).

Estrogenic effect of leachates and soil extracts from lysimeters spiked with sewage sludge and reference endocrine disrupters.

Several experiments were conducted to evaluate the behavior and performance of some potential endocrine disrupters (ECDs). Two in vitro screening assays, one based on MCF7-cell proliferation (E-screen test) and the other on estrogenic receptor activity [enzyme-linked receptor assay (ELRA)], were used for the tests, which were done in lysimeters 80 cm in diameter with depth of 30 cm (shallow) or 90 cm (deep). A sandy soil was used to fill in all lysimeters, which were spiked on the surface with either: (a) a sewage sludge (SS) at a dose equivalent to 20 tons ha-1; (b) a mixture of reference ECDs, comprising 17 alpha- and 17 beta-estradiol (E2), nonylphenol, octylphenol, and bisphenol A at doses 100 times higher than the maximum concentrations respectively found in the applied SS; or (c) a mixture of ECDs and SS. After percolation of the lysimeters with rain and/or artificial water, five leachates were sampled from each lysimeter during a period of 210 days. Immediately after the lysimeter percolation experiments, four and six soil fractions were dissected from, respectively, the 30-cm and 90-cm lysimeters and extracted by water. Both the leachate and soil extract samples were analyzed for their estrogenicity using the assays indicated above. The E-screen assay was highly sensitive only for some leachate and extract samples but gave no response for most leachates and soil extracts. The results of the ELRA assay suggests a significantly higher estrogenicity of leachate samples from shallow lysimeters compared with that of leachates from deep lysimeters. In contrast, the estrogenic effect measured for soil extracts of shallow lysimeters was lower than that measured for soil extracts of deep lysimeters. The results of the E-screen assay suggests the occurrence of a fast mobilization of applied ECDs and a moderate retardation effect of native ECDs contained in applied SS in the sandy soil used in the lysimeters. In lysimeters spiked with a mixture of SS and ECDs, the washing-out effect of ECDs in the first leachate fraction decreased, but the distribution of ECDs in the lysimeters increased. The relatively high estrogenic impact measured for soil water extracts suggests that the ECDs were mostly associated with water-soluble fractions of organic matter and/or water-suspended fractions of the mineral soil matrix. The application of SS to agricultural and forest fields may determine the immobilization of ECDs in soil or their movement to surface and/or groundwater. Therefore, an endocrine risk of exposure exists for the water and soil organisms.

Radionuclide transport above a near-surface water table: III. Soil migration and crop uptake of three gamma-emitting radionuclides, 1990 to 1993.

This paper summarizes the vertical distributions of 22Na, 137Cs, and 60Co above controlled water tables in deep and shallow lysimeters during a four-year experiment. The activity concentration profiles were all determined at the time of harvest of a winter wheat (Triticum aestivum L. cv. Pastiche) crop. Activity concentrations in different crop tissues were determined and crop uptake expressed as both an inventory ratio (IR) and a transfer factor (TFw), weighted to account for root and radionuclide distributions within the soil profile. Experimental variates were subjected to analysis of variance to determine the single and combined effects of the soil depth and the year of the experiment on the results obtained. Each radionuclide showed significant variations in activity concentration with soil depth, but the significance of these variations from year to year was dependent on radionuclide. A distinction in the behavior of weakly sorbed (22Na) and more highly sorbed (137Cs and 60Co) radionuclides was observed. The former exhibited significant variations in its distribution in the soil profile from year-to-year whereas the latter did not. Relatively high TF, values for 22Na were maintained throughout the experiment, whereas for 137Cs and 60Co, the highest TFw values were recorded in 1990 followed by a significant decline in 1991, with TFw remaining low in 1992 and 1993. The TFw values were, in general, significantly higher for deep lysimeters than for shallow lysimeters. This is thought to provide evidence of enhanced radionuclide absorption by the relatively small fraction of roots in the vicinity of the deeper water table.

Estimation of potential evapotranspiration with shallow lysimeters in a forest tree nursery

Daily evapotranspiration values (ETL) were obtained during three consecutive summers from water balance measurements on eight shallow drainable lysimeters in similarly planted nursery beds of either white spruce [Picea glauca (Moench) Voss] or black spruce [Picea mariana (Mill) B.S.P.]. Values of ETL and of potential evapotranspiration (PET), calculated with the Penman equation, were nearly equal for most of the sampled days during the first two years. During the last year of study, the ratio ETL/PET was reduced to 0.8 due to a lack of water input (precipitation and irrigation) to the lysimeters. Water balance measurements from the surrounding seedling beds showed that values of actual evapotranspiration (AET) for the first two years were 0.61 times those of either PET or ETL. Rates of evapotranspiration in the lysimeters remained high because of the high water contents in the shallow lysimeters induced by the presence of a zero tension plane at the base of the lysimeters, above the drainage holes. Results indicate that well-watered shallow lysimeters can be used to estimate values of PET and be used directly for the purpose of driving water balance models for irrigation scheduling. Key words: water relations, irrigation scheduling, lysimeters, evapotranspiration, white spruce, black spruce

The effects of SO2 and O3 fumigation on acid deposition and foliar leaching in the Liphook forest fumigation experiment

ABSTRACTThe ambient pollution climate at the Liphook forest fumigation site, where coniferous trees were fumigated with SO2 and O3, for 4 years under field conditions, was characteristic of the fringes of the areas where pollutant effects are a problem. Experimental treatments increased SO2 concentrations to levels more characteristic of Eastern Europe, and summer O3 concentrations by 30%. Deposition of SO2 to the soil between the trees (inferred from shallow lysimeters) was significant, the deposition velocity being 2–1 mms−1. Deposition to Scots pine and Sitka spruce canopies was greater, deposition velocities being 8.5 and 9.4 mm s−1, respectively. These high values may perhaps be explained by co‐deposition with NH3. Calculations assume that dry deposition was the sole source of SO42− gain in throughfall, and that there was no significant retention by the trees. There was a trend for O3 to enhance SO2 deposition to both soil and trees. Fumigation with SO2 led to a significant increase in leaching of cations from foliage. Each species neutralized about 63% of the dry‐deposited SO2, predominantly by ion exchange for Ca and K. Equations are provided which allow calculation of foliar leaching given SO2 concentrations or SO42− deposition. Fumigation increased the rate of nutrient cycling considerably, without affecting foliar concentrations or damaging the trees. Ozone treatments did not enhance foliar leaching, calling into question some suggested mechanisms for the causes of forest decline.

Radionuclide Transport above a Near‐Surface Water Table: II. Vertical Distribution of Gamma Activities within Soil Profiles in Relation to Wheat Rooting Density and Soil‐to‐Plant Transfers

AbstractRadiochemical results are described from a replicated field lysimeter experiment to investigate the upward migration of radionuclides in vegetated soils above near‐surface contaminated groundwater. Water tables were maintained at depths of 35 cm (shallow) and 65 cm (deep), below which a cocktail of radionuclides including 137Cs, 109Cd, 60Co, and 22Na was introduced. Results of the vertical migration and plant uptake are presented from the first 2 yr of an ongoing experiment with winter wheat (Triticum aestivum L.). As expected, 137Cs, 60Co, and 109Cd proved to be highly sorbed to the soil solid phase in the regions of the water table and exhibited a lesser degree of up‐profile transport than 22Na in shallow lysimeters. However, in deep lysimeters, 137Cs and 60Cs appeared to be preferentially accumulated at the soil surface; a biological translocation mechanism is postulated to account for this observation. It was clear from a statistical analysis of vertical radionuclide distributions that, in physicochemical terms, 22Na was the most mobile of the radionuclides studied. The distribution of this radionuclide within the soil profiles showed a significant shift between the two growth seasons examined, whereas the distributions of the other radionuclides remained static between 1990 and 1991. Each radionuclide showed a distinct and consistent distribution pattern throughout the crop tissues, although the differences in tissue specific activities for individual radionuclides were found to be nonsignificant with the exception of 22Na. Soil‐to‐plant transfer factors (TFw) were calculated using mean soil specific activities weighted according to the fractional abundance of roots and measured soil specific activities in discrete soil layers. The TFw values were significantly lower in 1991 than in 1990 in both shallow and deep lysimeters; it is postulated that this was due to a much greater fiux of water through the crop in 1990, which was characterized by high evapotranspiration rates and a substantial negative water budget. In both years, TFw values were, in general, significantly higher for deep lysimeters than for shallow lysimeters. This is thought to provide evidence of enhanced radionuclide absorption by the relatively small fraction of roots in the vicinity of the deeper water table.