Surface Soil Drying Research Articles

Uptake of subsoil water below 2 m fails to alleviate drought response in deep-rooted Chicory (Cichorium intybus L.)

AimsDeep-rooted agricultural crops can potentially utilize deep soil moisture to reduce periods where growth is water limited. Chicory (Cichorium intybus L.) is a deep-rooted species, but the benefits of deep roots to water uptake has not been studied. The aim of this study was to investigate the value of deep roots (>2 m) under topsoil water limitation.MethodsChicory grown in 4 m deep soil-filled rhizotrons was exposed to either topsoil drought or resource competition from the shallow-rooted species ryegrass (Lolium perenne L.) and black medic (Medicago lupulina L.). The effect on deep water uptake was assessed using non-destructive measurements of roots, soil water and tracers.ResultsWater uptake occurred below 1.7 m depth in 2016, and below 2.3 m depth in 2017 and contributed significantly to chicory water use. However, neither surface soil drying nor intercropping increased deep water uptake to relieve water deficit in the shoots.ConclusionChicory benefits from deep-roots during drought events, as it acceses deep soil moisture unavailable to more shallow rooted species, yet deep water uptake was unable to compensate for the reduced topsoil water uptake due to soil drying or crop competition.

The effect of long-term drying associated with experimental drainage and road construction on vegetation composition and productivity in boreal fens

Land-use and climate change are expected to cause drying of vegetation and surface soils in continental boreal peatlands. We examined the effects of multi-decadal drying and drainage on plant community structure and productivity in four fens located in Alberta, Canada. Long-term drying resulted in a two to fourfold increase in total biomass in three of the four fen sites, with a similar large increase in NPP in Treed Fen 1. The treed poor fens consistently had decreased moss cover and productivity with drainage. Across all sites, changes in understory community composition were related to the change in water table position as well as overstory canopy development that occurred post-drainage. Overall, drainage induced a shift toward a drier peatland regime, favoring increased canopy and vascular plant density at the expense of ground-layer mosses or the understory. Within the ground layer communities, drainage favored dry-adapted hummock moss and lichen species over those wet-adapted but dessication-prone species typical of low-lying lawns and hollows. Alteration of fen vegetation due to ecosystem drying will not only influence carbon sequestration but also will increase the vulnerability of peatlands to wildfire, increasing the risk of further ecosystem degradation and possible loss of resilience.

Photosynthesis, root respiration, and grain yield of spring wheat in response to surface soil drying

The aims of this research were to test the influence of surface soil drying on photosynthesis, root respiration and grain yield of spring wheat (Triticum aestivum), and to evaluate the relationship between root respiration and grain yield. Wheat plants were grown in PVC tubes 120 cm in length and 10 cm in diameter. Three water regimes were employed: (a) all soil layers were irrigated close to field water capacity (CK); (b) upper soil layers (0–40 cm from top) drying (UD); (c) lower soil layer (80–120 cm from top) wet (LW). The results showed that although upper drying treatment maintained the highest root biomass, root respiration and photosynthesis rates at anthesis, the root respiration of the former was significantly (P < 0.05) lower than the latter at the jointing stage. There were no differences in water use efficiency or harvest index between plants from the upper drying and well-watered treatment. However, the grain weight for plants in the upper drying treatment was significantly (P< 0.05) higher than that of in well-watered control. The results suggest that reduced root respiration rate and the amount of photosynthates utilized by root respiration in early season growth may also have contributed to improve crop production under soil drying. Reduced root activity and root respiration rate, in the early growth stage, not only increased the photosynthate use efficiency (root respiration rate: photosynthesis ratio), but also grain yield. Rooting into a deeper wet soil profile before grain filling was crucial for spring wheat to achieve a successful seedling establishment and high grain yield.

Demographic and environmental causes of the decline of rural Song Thrushes Turdus philomelos in lowland Britain

We review current knowledge of demographic mechanisms and environmental factors implicated in the population decline of Song Thrushes Turdus philomelos in rural Britain since the mid‐1970s, and present new analyses of regional variation in population changes. Increased mortality during the first year of life (from fledging to recruitment) is highlighted as a potential demographic mechanism having driven the population decline, while Song Thrushes in a rapidly declining farmland population were making too few nesting attempts to sustain local numbers. Breeding Song Thrushes are strongly associated with non‐cropped habitats such as woodland edge, field boundaries, gardens and scrub; they make substantial use of grassland, but avoid cereals when foraging. Earthworms constitute a key component of Song Thrush diet and the availability of this prey is strongly influenced by moisture levels in surface soils. Several lines of evidence suggest that dry surface soils during summer are deleterious to the productivity and survival of Song Thrushes, and regional variation in the rates of population change in Britain during 1970–86 was negatively correlated with the extent of under‐field drainage on farmland (the main function of which is to promote the drying of surface soils). Increasing dryness of agricultural soils and the loss of grassland from eastern arable counties have probably both contributed to the declines of rural Song Thrushes in Britain. Loss of hedgerows and scrub, and the degradation of woodland may also have contributed to population declines but the role of predators remains unclear. Recovery of rural Song Thrush populations requires challenging new policy initiatives that should aim to restore nesting cover (scrub and woodland understorey), grazed grassland in arable‐dominated areas and damper soils in summer.

Physiological Adaptation of Kentucky Bluegrass to Localized Soil Drying

This study was designed to investigate effects of surface soil drying (SD) on water relations, gas exchange, growth characteristics, and abscisic acid (ABA) content of leaves and roots for Kentucky bluegrass (Poa pratensis L.), and to examine whether physiological adaptation to SD is associated with hydraulic or chemical regulation. ‘Award’ and ‘Nuglade’ were subjected to three soil moisture treatments in a growth chamber: (i) well‐watered control; (ii) SD (0–20 cm); and (iii) full soil profile (0–40 cm) drying (FD). Under SD, turf quality (TQ), relative water content (RWC), photosynthesis, and cell membrane stability remained the same as the controls, but stomatal conductance (gs) declined by 35 and 45%, and shoot growth rates were reduced by 50 and 40% for Award and Nuglade, respectively. Root DW decreased in 0‐ to 20‐cm dry soil, but increased compared with controls in the 20‐ to 40‐cm wet soil under SD. The ABA content increased by four to sixfold in roots at 0‐ to 20‐cm drying soil and did not change in the 20‐ to 40‐cm wet soil under SD conditions. The ABA content was also higher in leaves of SD plants. The results suggested Kentucky bluegrass adapted to localized soil drying by maintaining TQ, photosynthesis, leaf water status (WS), and root growth using water in the deeper soil profile. Decline in gs and shoot growth was independent of leaf WS, and could be hormonally controlled, which could help maintain favorable WS in leaves by reducing water loss under SD conditions.

Decomposition of mountain birch leaf litter at the forest-tundra ecotone in the Fennoscandian mountains in relation to climate and soil conditions

Litter decomposition is a key process in terrestrial ecosystems, releasing nutrients, returning CO2 to the atmosphere, and contributing to the formation of humus. Litter decomposition is strongly controlled both by climate and by litter quality: global warming scenarios involving shifts in vegetation communities are therefore of particular interest in this context. The objective of the present study was to quantify the role of climatic environment and underlying substrate chemistry for the decomposition of standard mountain birch (Betula pubescens Ehrh. spp. czerepanovii) leaf litter at four sites, spanning the forest-tundra ecotone, in the Fennoscandian mountain range. Litter quality effects were thus held constant, but the study incorporated systematic changes in (i) latitude/altitude, (ii) `continentality', and (iii) vegetation community at each site, together with (iv) experimental manipulation of temperature using passive warming systems. The study was undertaken during a 3 year period, and forms part of a broader investigation of forest-tundra ecotone dynamics in the Fennoscandian mountains. Our results showed (1) higher decomposition rates in forest sites compared to tundra, (2) that the difference between the two vegetation communities was most pronounced at the more maritime sites, and (3) that chemistry of litter remaining after the three years experiment varied according to site and vegetation community (e.g. at the most southerly site, more lignin had decomposed at tundra communities compared with the forest). (4) Surface temperature explained 58% of the variation in mass loss at forest sites; at tundra sites, however, we hypothesise that litter moisture content was the more important factor. (5) Experimental warming lent weight to this hypothesis by reducing rates of mass loss: this reduction was likely the result of surface soil drying, an artefact of the warming treatment. We conclude that a replacement of tundra by forest would likely accelerate litter decomposition both via changes in surface and near-surface temperature and moisture regimes, although the strength of this response will vary between maritime and continental parts of the mountain range.

Habitat selection by song thrushes in stable and declining farmland populations

Summary Losses of farmland birds from the wider countryside have become a major conservation issue in the UK and Europe. Song thrush Turdus philomelos populations in lowland rural Britain declined by approximately 70% during 1970–95, most severely on intensively managed arable farmland. Comparison between a stable population on mixed farmland and a rapidly declining population on arable farmland revealed fewer nesting attempts each summer by birds in the declining population, and annual productivity was insufficient to maintain local population density. Inadequate food resources were the most plausible cause. We compared breeding season habitat selection (using radio‐telemetry) and earthworm availability (a major component of summer diet) for song thrushes in the same two farmland populations. Territory settlement in the mixed farmland landscape involved the selection of field boundaries and woodland and the avoidance of arable crops. Field boundaries and gardens were selected in the arable landscape, while arable break crops and small areas of woodland were avoided. Habitat selection (intensity of usage) did not change through the breeding season and did not differ between study areas. Scrub, woodland edge, wet ditches and bare soil in gardens were preferred foraging habitats, while cereals were avoided. Habitat utilization (amount of usage) differed markedly between study areas. Woodland and grassland accounted for 53% of all habitat usage in the mixed farmland landscape compared with just 13% in the arable landscape. Gardens and arable crops were more heavily utilized in the arable landscape, accounting for 58% of all usage compared with 22% in the mixed landscape. Earthworm availability declined markedly between April and June as surface soils dried out. Lower earthworm availability in the arable landscape was associated with more rapid and pronounced drying of surface soils. Synthesis and applications. Lack of woodland and grassland, and the faster drying of surface soils in the arable landscape, combined to limit the availability to thrushes of key summer invertebrate prey. Loss of hedgerows, scrub and permanent grassland with livestock, and the wide‐scale installation of under‐field drainage systems, have probably all contributed to the decline of song thrushes on UK arable farmland. New agri‐environment measures may be needed to provide the nesting cover adjacent to invertebrate‐rich damp soils that song thrushes require to sustain annual productivity.

Effects of Top-Soil Drying on Saltceder Photosynthesis and Stomatal Conductance

Phreatophytes are trees and shrubs with deep roots tapping the water tables. As such they are presumed to be able to tolerate a water deficit in the top soil. Growth of some phreatophytes is decoupled from environmental factors such as incident precipitation. This study examined the effects of surface soil drying on gas exchange and stomatal conductance of a riparian phreatophyte Tamarix gallica L. (saltcedar) during 2 consecutive growing seasons in which summer precipitation varied substantially. Daily average gas exchange (A) was 13.5 micromol m(-2) sec(-1) in June and 13.4 micromol m(-2) sec(-1) in September, 1991 when surface soil was wet as compared to the same periods of 1990 in which very little rain occurred (6.44 and 8.08 micromol m(-2) sec(-1), respectively, P < 0.0001). Stomatal conductance (g) or maximal conductance showed a similar trend of photosynthesis. Both average gas exchange and stomatal conductance were correlated with water content in the upper portion of the soil (r = 0.83 to 0.88 for A, P < 0.05 and r = 0.65 to 0.70 for g, P < 0.05) in 1990 (a dry year). The variations in gas exchange or stomatac conductance of saltcedar were mainly caused by water availability in the upper soil layers, not by depth to the water table (0.65 vs 2.74 m). The responses of gas exchange and stomatal conductance to surface soil drying in the phreatophyte saltcedar were similar to that of several crop species [lupin (Lupinus cosentinii Guss. cv. Eregulla), wheat (Triticum aestivum L. cv. Cadensa) and sunflower (Helianthus annuus L.)]. Our data suggest that upon soil re-wetting, when water availability to shallow lateral roots increased, the entire root system of saltcedar was actively involved in water uptake, leading to higher stomatal conductance and photosynthesis. DOI:10.2458/azu_jrm_v55i1_mounsif

Effects of top-soil drying on saltcedar photosynthesis and stomatal conductance

Phreatophytes are trees and shrubs with deep roots tapping the water tables. As such they are presumed to be able to tolerate a water deficit in the top soil. Growth of some phreatophytes is decoupled from environmental factors such as incident precipitation. This study examined the effects of surface soil drying on gas exchange and stomatal conductance of a riparian phreatophyte Tamarix gallica L. (saltcedar) during 2 consecutive growing seasons in which summer precipitation varied substantially. Daily average gas exchange (A) was 13.5 micromol m(-2) sec(-1) in June and 13.4 micromol m(-2) sec(-1) in September, 1991 when surface soil was wet as compared to the same periods of 1990 in which very little rain occurred (6.44 and 8.08 micromol m(-2) sec(-1), respectively, P &lt; 0.0001). Stomatal conductance (g) or maximal conductance showed a similar trend of photosynthesis. Both average gas exchange and stomatal conductance were correlated with water content in the upper portion of the soil (r = 0.83 to 0.88 for A, P &lt; 0.05 and r = 0.65 to 0.70 for g, P &lt; 0.05) in 1990 (a dry year). The variations in gas exchange or stomatac conductance of saltcedar were mainly caused by water availability in the upper soil layers, not by depth to the water table (0.65 vs 2.74 m). The responses of gas exchange and stomatal conductance to surface soil drying in the phreatophyte saltcedar were similar to that of several crop species [lupin (Lupinus cosentinii Guss. cv. Eregulla), wheat (Triticum aestivum L. cv. Cadensa) and sunflower (Helianthus annuus L.)]. Our data suggest that upon soil re-wetting, when water availability to shallow lateral roots increased, the entire root system of saltcedar was actively involved in water uptake, leading to higher stomatal conductance and photosynthesis.

Involvement of antioxidants and lipid peroxidation in the adaptation of two cool-season grasses to localized drought stress

In natural environments, drought often occurs in surface soil while water is available for plant uptake deeper in the soil profile. The objective of the study was to examine the involvement of antioxidant metabolism and lipid peroxidation in the responses of two cool-season grasses to surface soil drying. Kentucky bluegrass ( Poa pratensis L) and tall fescue ( Festuca arundinacea Schreb.) were grown in split tubes, consisting of two sections (each 10 cm in diameter and 20 cm long). Grasses were subjected to three soil moisture regimes: (a) well-watered control: whole soil profile was watered; (b) surface drying: surface 20 cm of soil was dried by withholding irrigation and the lower 20 cm of soil was watered; (c) full drying: whole soil profile was dried. Surface drying had no effects on relative water content (RWC) and chlorophyll content (Chl) for both grasses and only slightly reduced shoot growth for tall fescue. Superoxide dismutase (SOD) activity increased, while catalase (CAT) and peroxidase (POD) activities remained unchanged during most periods of surface drying. Malondialdehyde (MDA) content was unaffected by surface drying for tall fescue, but increased initially and then decreased to the control level for Kentucky bluegrass. Under full drying, RWC, Chl content, and shoot dry weight decreased, but MDA content increased in both grasses; SOD and POD activities initially increased transiently and then decreased; CAT remained unchanged for 25 days and then decreased. These results suggested that both Kentucky bluegrass and tall fescue were capable of surviving surface soil drying. This capability could be related to increases in antioxidant activities, particularly SOD and CAT. However, full drying suppressed antioxidant activities and induced lipid peroxidation.

Photosynthesis, respiration, and carbon allocation of two cool-season perennial grasses in response to surface soil drying

The study was conducted to investigate carbon metabolic responses to surface soil drying for cool-season grasses. Kentucky bluegrass (Poa pratensis L.) and tall fescue (Festuca arundinaceae Schreb.) were grown in a greenhouse in split tubes consisting of two sections. Plants were subjected to three soil moisture regimes: (1) well-watered control; (2) drying of upper 20-cm soil (upper drying); and (3) drying of whole 40-cm soil profile (full drying). Upper drying for 30 d had no dramatic effects on leaf water potential (Ψleaf) and canopy photosynthetic rate (Pn) in either grass species compared to the well-watered control, but it reduced canopy respiration rate (Rcanopy) and root respiration rate in the top 20 cm of soil (Rtop). For both species in the lower 20 cm of wet soil, root respiration rates (Rbottom) were similar to the control levels, and carbon allocation to roots increased with the upper soil drying, particularly for tall fescue. The proportion of roots decreased in the 0-20 cm drying soil, but increased in the lower 20 cm wet soil for both grass species; the increase was greater for tall fescue. The Ψleaf, Pn, Rcanopy, Rtop, Rbottom, and carbon allocation to roots in both soil layers were all significantly higher for upper dried plants than for fully dried plants of both grass species. The reductions in Rcanopy and Rtop in surface drying soil and increases in root respiration and carbon allocation to roots in lower wet soil could help these grasses cope with surface-soil drought stress.

Water relations and root activities of Buchloe dactyloides and Zoysia japonica in response to localized soil drying

Effects of localized soil drought stress on water relations, root growth, and nutrient uptake were examined in drought tolerant ‘Prairie’ buffalograss [Buchloe dactyloides (Nutt.) Engelm.] and sensitive ‘Meyer’ zoysiagrass (Zoysia japonica Steud.). Grasses were grown in small rhizotrons in a greenhouse and subjected to three soil moisture regimes: (1) watering the entire 80-cm soil profile (well-watered control); (2) drying 0–40 cm soil and watering the lower 40 cm (partially dried); (3) and drying the entire soil profile (fully dried). Drying the 0–40 cm soil for 28 days had no effect on leaf water potential (Ψ leaf ) in Prairie buffalograss compared to the well-watered control but reduced that in Meyer zoysiagrass. Root elongation rate was greater for Prairie buffalograss than Meyer zoysiagrass under well-watered or fully dried conditions. Rooting depth increased with surface soil drying; with Prairie buffalograss having a larger proportion of roots in the lower 40 cm than Meyer zoysiagrass. The higher rates of water uptake in the deeper soil profile in the partially dried compared to the well-watered treatment and by Prairie buffalograss compared to Meyer zoysiagrass could be due to differences in root distribution. Root 15N uptake for Prairie buffalograss was higher in 0–20 cm drying soil in the partially dried treatment than in the fully dried treatment. Diurnal fluctuations in soil water content in the upper 20 cm of soil when the lower 40 cm were well-watered indicated water efflux from the deeper roots to the drying surface soil. This could help sustain root growth, maintain nutrient uptake in the upper drying soil layer, and prolong turfgrass growth under localized drying conditions, especially for the deep-rooted Prairie buffalograss.

Drying of surface soil decreased Lupinus angustifolius root length and manganese uptake in a split-root experiment

In a glasshouse, a split-root experiment was used to determine the ability oflupins (Lupinus angustifolius L.) to take up manganese(Mn) from dry soil either when young or at mid-flowering of the primarybranches. Three soil-watering regimes (maintained at field capacity,maintained below wilting point, and alternating from field capacity to wellbelow wilting point) were imposed after taproots had grown through topsoil andinto a nutrient solution below. Four sequential harvests (11, 22, 37, and 49days after sowing) were taken to determine the effect of soil drying on lupingrowth, Mn uptake, and soil-extractable Mn.Soil drying early in the lupin plant's life stopped the growth of lateralroots in the soil and slowed the growth of roots grown in subsoil solution andthe growth of lupin tops. Soil drying decreased uptake of Mn in the tops to13% of that under continuous wet soil conditions. Of the 13%,most (11%) was taken up while the soil was drying. Soil re-wettingenabled the plants to resume uptake of Mn and soil re-drying (just beforeanthesis) decreased the Mn concentration in the lupin stems to 4·8µg/g, whereas stems of lupins grown in the wet and dry soilscontained 10·3 and 3·3 µg/g, respectively. Easilyreducible and plant-available soil Mn were not affected by soil wetting anddrying treatments.This study confirms that the uptake of Mn by lupin may be severely restrictedby drying of surface soil at both the beginning and the end of the lupinplant's life. The decrease in root length rather than the chemical form of Mn restricted Mn uptake.

Drought‐Resistance Mechanisms of Seven Warm‐Season Turfgrasses under Surface Soil Drying: I. Shoot Response

Knowledge of drought response differences in turfgrasses would accelerate the effectiveness in developing water‐use‐efficient species. The study was designed to evaluate shoot morphological and physiological traits in relation to drought resistance for seven warm‐season turfgrasses: bermudagrass [Cynodon dactylon (L.) Pets. ‘Common’], centipedegrass [Eremochloa ophiuroides (Munro) Hackel ‘TifBlair’], seashore paspalum (Paspalum vaginatum Swartz, four ecotypes), and zoysiagrass (Zoysia japonica Steudel × Z. tenuifolia Steudel ‘Emerald’) under surface soil drying and rewatering conditions. Plants were grown in a greenhouse during 1995 and 1996 in sectioned PVC tubes under four soil moisture treatments. Drought resistance among the turfgrasses was assessed using canopy temperature, leaf chlorophyll content, relative water content, and shoot dry matter production in response to drying of 0‐ to 20‐ and 0‐ to 40‐cm soil layers. The rank in drought resistance in the 0‐ to 40‐cm drying regime was: Paspalum PI 509018 = TifBlair centipedegrass &gt; AP14 = PI 299042 &gt; Adalayd &gt; Common bermudagrass = Emerald zoysiagrass. Shoot dry matter production recovered fully after rewatering for TifBlair centipedegrass and paspalums except Adalayd, but only partially for Common bermudagrass and Emerald zoysiagrass. The differences in shoot responses to drought stress and rewatering among the seven grasses were presumably related to variations (plasticity) in rooting characteristics as demonstrated in root responses.

Drought‐Resistance Mechanisms of Seven Warm‐Season Turfgrasses under Surface Soil Drying: II. Root Aspects

Knowledge of drought‐resistance mechanisms in turfgrasses would improve management strategies and facilitate turfgrass breeding for drought resistance. The experiment investigated root morphological and physiological characteristics in response to surface soil drying and rewatering for bermudagrass [Cynodon dactylon (L.) Pers. ‘Common’], centipedegrass [Eremochloa ophiuroides (Munro) Hack ‘Tif‐Blair’], seashore paspalum (Paspalum vaginatum Swartz, four ecotypes), and zoysiagrass (Zoysia japonica Steudel × Z. tenuifolia Steudel ‘Emerald’). Plants were grown in sectioned PVC tubes with four soil moisture regimes in a greenhouse during 1995 and 1996. Root growth was reduced when the upper 20‐ and 40‐cm soil layers dried for Emerald zoysiagrass, Common bermudagrass, and Adalayd paspalum, but only with upper 40‐cm soil drying for PI 299042, AP14, and PI 509018 paspalums, and TifBlair centipedegrass. Root dry weight recovered fully to control levels after rewatering for TifBlair centipedegrass and the three paspalum accession, but only partially for Adalayd paspalum, Common bermudagrass, and Emerald zoysiagrass. Superior drought resistance to surface soil drying for PI 509018 paspalum and TifBlair centipedegrass was associated with enhanced root growth and rapid root water uptake at deeper soil layers, maintenance of root viability at the surface drying soil, and rapid root regeneration after rewatering. Differences in these drought avoidance characteristics among turfgrasses could serve as selection criteria for improving turf drought resistance.

Measured and Simulated Surface Soil Drying

AbstractThe USDA initiated the Wind Erosion Prediction System (WEPS) to develop improved technology for predicting wind erosion. A HYDROLOGY submodel has been developed for WEPS to simulate the soil energy and water balances. This study was conducted to evaluate the performance of the HYDROLOGY submodel in predicting surface soil drying. Water content was measured gravimetrically in a bare 5‐ by 30‐m plot for 14 d after irrigation during July and August 1991. The plot was located 5 m directly north of a bare weighing lysimeter at the USDA‐ARS Conservation and Production Research Laboratory at Bushland, TX. Hourly samples were taken from depth increments of 0 to 2, 2 to 6, 6 to 10, 10 to 30, and 30 to 50 mm. Furthermore, soil cores were taken to 900 mm at 6‐h intervals. Water content was also measured daily at the lysimeter and between the lysimeter and gravimetric sampling plot using a neutron probe to 2.1 m. The submodel accurately predicted that no deep percolation occurred throughout the simulation period. Simulation results agreed well with the measured daily evaporation rates from the lysimeter (r2 = 0.96). Furthermore, the submodel reasonably estimated the soil water content profiles, particularly the status of soil water at the soil‐atmosphere interface. The mean absolute error, which describes the average absolute deviation between measured and simulated soil water contents, was 0.015 m3 m−3. The HYDROLOGY submodel of WEPS shows a potential to accurately simulate soil water dynamics, as needed for wind erosion modeling. The submodel successfully predicts the changes in water content at the soil surface, which relate to the susceptibility of the soil to wind erosion.

Runoff Reduction by Venting with Shallow Subsurface Drainage

ABSTRACT HIGH intensity rainfall events were simulated on a Buchanan stony loam with a shallow subsurface drain placed just above the fragipan at a depth of 0.52 m. The soil was drained for either 2 or 4 days and in some treatments disturbed to 100 or 150-mm depths to evaluate the effect of the change in volume of soil air in the plow layer before each rainstorm. Runoff occurred earlier and in greater volumes when soil air was trapped within the soil ahead of the wetting front than when the air was vented via shallow subsurface drains. Surface soil drying and disturbing the soil to 100 or 150 mm increased the number of macro pores and voids resulting in additional soil air being available for entrapment thus causing greater reductions in infiltration.

Germination of Blue Grama Seeds Buried by Dung Beetles (Coleoptera: Scarabaeidae)1

Natural establishment of blue grama (Bouteloua gracilis) seedlings is not reported to occur on shortgrass prairie. Lack of adequate moisture at the soil surface prevents germination, and, once germination has occurred, rapid drying of surface soils frequently results in the death of elongating seminal roots. Establishment of blue grama seedlings may be facilitated by dung-burying beetles. Greenhouse experiments with Canthon pilularius showed that blue grama seeds mixed into fresh cattle feces survived formation and burial of brood balls, larval development within the brood ball, and subsequent emergence of adult beetles. Blue grama seedlings were recorded at several sites where C. pilularius had buried dung in cages filled with sterilized (autoclaved) potting soil.

Planting Germinated Grass Seed

ABSTRACT RAPID drying of the surface 2 or 3 cm of soil often prevents grass seedling establishment in the Southern Great Plains. In this greenhouse study, seeds that were germinated before planting avoided water stress caused by rapid surface soil drying. Kleingrass (Panicum coloratum L.) and hardinggrass (Phalaris aquatica L.) seeds, that were germinated before plant-ing, established substantially more plants than untreated seeds under dry surface conditions. Kleingrass seeds need to be germinated only to the point at which the radi-cle is just ready to emerge from the seed coat. Ger-minated seeds emerged when watered following 20 days in dry soil.

EXTENT AND LONGEVITY OF THE SEMINAL ROOTS OF CERTAIN GRASSES

Grasses possess two distinct root systems. primary or seminal root system begins development immediately upon the germination of the seed and consists of one to several main roots and their branches, the number varying with the species. young plant is entirely dependent upon this primary root system for water and soil nutrients. Later, especially during the period of tiller production, a secondary or nodal root system develops from the lower nodes of the parent culm and from the tillers. seminal roots are often designated as temporary in general texts and even in special books on grasses. Hitchcock (1) states: The primary root persists only a short time after germination, its place being taken by secondary roots produced from the nodes of the young culm. It has been observed by Locke and Clark (5) that where extremely dry surface soil or soil drying or crusting prevented normal development of nodal roots, the seminal roots furnished sufficient moisture to maintain the growth of the wheat plant to maturity. Weaver, Jean, and Crist (13), after numerous investigations on the root systems of several cereal crops, concluded that the seminal roots remain alive and active until the time of harvest. Simmonds and Sallans (12) found that the wheat plant may produce seed when dependent almost entirely upon the seminal roots. Simmonds (ll) states that the seminal roots of wheat remain functional throughout the entire life of the plant. Records on absorption of water and salts from water cultures by Krassovsky (3) have shown that the seminal roots of wheat, barley, and rye are active up to the time of harvest. These findings were later confirmed by plants grown in soil (4). Pavlychenko (9) states that in the several annual grasses studied in arid climates, seminal roots functioned throughout the entire growing season and were frequently the only roots supporting the plant from emergence to maturity. Studies on seminal roots of perennial grasses, however, are very few, and usually mention of their development is only incidental. purpose of this study was to ascertain the extent of their development among perennial grasses ; how long they remain alive and functional after the secondary root system is established and how much growth grasses can make when supported by the seminal roots alone.