Low Soil Moisture Conditions Research Articles

Effects of a Reduction in Soil Moisture from One Month beforeFlowering through Ripening on Dry Matter Production and Ecophysiological Characteristics of Wheat Plants

We found in the previous study that the wheat plants grown under relatively low soil moisture conditions (D plot) could attain heavier dry matter than the plants watered on the basis of average local precipitation (W plot). The aim of this study was to make a detail analysis of the ecophysiological characteristics that cause the difference in dry matter production between the plants in the W and D plots under different soil moisture conditions. Soil matric potential at a depth of 30 cm was kept at about −4 kPa in the W plot. It decreased gradually after watering at about one month before heading and at heading, reaching about −80 kPa at heading stage and at the mid-ripening stage respectively, in the D plot. The plants in the D plot produced heavier dry matter and a better developed root system than the plants in the W plot. The higher net assimilation rate and larger leaf area, which accounted for the higher crop growth rate of the D plot, weredue both to avoiding suppression of the photosynthetic rate and leaf expansion owing to water stress, and to maintaining high rates of leaf photosynthesis and a large leaf area during leaf senescence. A larger amount of nitrogen was accumulatedat the flowering stage and the nitrogen content of leaves remained higher during senescence in plants in the D plot than those in the W plot. The activity of cytokinins in the xylem sap was higher in plants in the D plot. These characteristics might have contributed to the delay in the decline in the rate of photosynthesis and in leaf area during leaf senescence and seemed to be supported by the enhanced development of the root system under moisture-restricted conditions.

Surface runoff and soil erosion on unpaved forest roads from rainfall simulation tests in northeastern Spain

The generation of surface runoff and transport of sediment were studied on unpaved forest roads in the Iberian Range (Spain). To this end, a mobile rainfall simulator was used so that information could be compared. Twenty-eight rainfall simulations were carried out on the cutslope (12), sidecast fill (6) and roadbed (10). Under low soil moisture conditions, cutslopes had runoff coefficients of 58%, and overland flow was generated in 3 min. On the sidecast fill and the roadbed, the runoff coefficients were 34% and 46%, respectively. The part of the road that showed the greatest erosion was the cutslope (161 g m −2), where mass wasting and freeze–thaw processes supply loose material to be transported by overland flow. The cutslope soil loss rates exceed those from the sidecast fill and the roadbed by 16 and 11 times, respectively. In these tests, the maximum sediment concentration was recorded in the first few minutes. The concentration reduces with time as a consequence of the exhaustion of loose surface material. Correlation coefficients and regression analysis showed that the gradient, plant cover density and stone cover of the cutslopes, fill areas and roadbeds had statistically significant effects on runoff and erosion. A comparison of these data with others obtained on different land-uses allowed us to conclude that some parts of forest roads have similar hydromorphological behaviour to abandoned fields in mountainous areas and to cereal fields.

Creeping Bentgrass Physiological Responses to Natural Plant Growth Regulators and Iron Under Two Regimes

Creeping bentgrass (Agrostis palustris Huds.) is an extensively used cool-season grass for fine turf areas such as golf course putting greens, but suffers from poor summer stress tolerance. These studies were conducted to investigate the influences of natural plant growth regulators (NPGR) and Fe on creeping bentgrass photochemical activity (PA), antioxidant superoxide dismutase (SOD) activity, root growth and leaf color under two fertilization regimes. The bentgrass was maintained in well-watered field conditions or water-stressed glasshouse conditions. A mature bentgrass was treated monthly during the field season with seaweed (Ascophyllum nodosum Jol.) extract (SWE) at 50 mg·m-2 or humic acid (HA) at 150 mg·m-2 or in combination with or without FeSO4 at 520 mg·m-2 and grown under a low or a high fertilization regime. Foliar application of SWE + Fe increased PA (14% to 15%), while applications of SWE + HA or SWE + HA + Fe increased SOD activity (49% to 114%) of creeping bentgrass in Summer 1997 and Summer 1998. There was no significant fertilization × NPGR interaction for PA and SOD activity. Bentgrass PA was increased by 13% to 46% when treated with NPGR with or without Fe compared to the control measured in May. The addition of Fe with each NPGR application improved fall and winter leaf color. All NPGR and Fe treatments increased root mass (17% to 29%) in Aug. 1997 and 1998, except HA alone in 1998. Under sustained low soil moisture (-0.5 MPa) conditions, application of NPGR with or without Fe increased PA and SOD activity. The data indicate that SWE and HA enhance the physiological function of `Southshore' creeping bentgrass, resulting in improved root growth regardless of low or high fertilization regime. However, addition of Fe to these NPGR served primarily to improve late season leaf color. The results suggest that, in addition to maintaining adequate plant-available nutrients, applications of natural PGRs, such as SWE and HA, prior to and during summer abiotic stresses would be beneficial.

Laboratory and field studies on the degradation of fipronil in a soil

Degradation of a new insecticide/termiticide, fipronil, in a soil was studied in the laboratory and field. Three metabolites of fipronil (desulfinyl, sulfide, and sulfone derivatives) were identified from soils after treatment. Laboratory studies showed that soil moisture content had a great effect on the degradation rate of fipronil and products formed. High soil moisture contents (>50%) favored the formation of a sulfide derivative of fipronil by reduction, whereas low soil moisture (<50%) and well-aerated conditions favored the formation of fipronil sulfone by oxidation. Microorganisms in soil accelerated the degradation of fipronil to sulfide and sulfone derivatives. The third transformation product, a desulfinyl derivative, was formed by photodecomposition of fipronil in water and on the soil surface under sunlight. The desulfinyl derivative degraded rapidly in field soils with a half-life of 41–55 days compared with an average half-life of 132 days for fipronil. The half-life of the 'total toxic component' (fipronil and its metabolites) in field soil was 188 days on average.

Differences in the Rate of Seedling Emergence among Rice Cultivars under Low Soil-Moisture Conditions

The objective of this study was to identify rice cultivars with high emergence ability under low soil-moisture conditions using a large number of rice cultivars, and to clarify the differences between the rates of emergence in lowland and upland, white- and red-kerneled, and non-glutinous and glutinous cultivars. First, 30 cultivars with a high emergence rate at 14 days after sowing (DAS) were selected at a soil water potential of -1.17 to -0.89 MPa from 382 cultivars through fourscreening experiments. In these experiments, the emergence rate was significantly higher in the upland cultivars than in the lowland cultivars. The red-kerneled cultivars also had a significantly higher emergence rate than the white-kerneled cultivars. However, no difference in emergence rate was observed between the non-glutinous and glutinous cultivars. Second, the emergence rates of various cultivars were examined at a soil water potential of -1.62, -1.23, and -1.07 MPa. The higher the soil water potential, the higher the emergence rate at 28 DAS and the shorter the time to the emergence. The order of cultivars in their emergence rate at 13 DAS at -1.07 MPa was similar to that at 28 DAS at -1.62 MPa. Therefore, the dataat 13 DAS at -1.07 MPa were used to compare the selected 30 cultivars for their emergence ability under low soil-moisture conditions. Moulla Topa showed the highest emergence rate (78.1%) and Gaiya Rate Bhasunamathe the shortest time to 50% emergence (11.1 d) under these conditions.

Effect of Seed Hardening, Wetting and Redryieg before Sowing, on Germination and Seedling Emergence of a Japanese Wheat Variety Norin 61 in Desiccated Soil

Seed hardening, wetting and redrying of the seed before sowing, promotes germination under low soil-moisture conditions in wheat varieties bred and grown in semi-arid areas. It is unknown, however, whether this is also the case in wheat varieties cultivated in a temperate humid zone. We examined the effect of the seed hardening on germination and seedling emergence under low soil-moisture conditions in a wheat variety, Norin 61, which is cultivated over a wide area of the temperate humid zone in Japan. We first determined the optimum temperature for germination (23° C) and the critical range of soil-moisture (GR) for germination (water-holding capacity of 24%; – 0.30 MPa). Then, we imbibed the seeds of Norin 61 for various periods followed by air-drying, and compared the germination of these seeds and their seedling emergence with those in non-treated seeds at 23°C under GR condition. Imbibition of the seeds for 24 h, which increased the water content to 64%, followed by redrying significantly accelerated the germination and seedling emergence under such conditions. Even in the field, the seed hardening treatment significantly accelerated germination and seedling emergence under both irrigated and non-irrigated conditions. We concluded that seed hardening treatment is available to accelerate the germination of a wheat variety of the temperate humid zone in Japan, Norin 61.

Bearing capacity of forest access roads built on peat soils

Significance of the thickness of peat substratum on the bearing capacity of forest access roads laid on peat soils in Ireland is evaluated. Bearing capacity of an experimental pavement was assessed on the basis of its surface deflection measured using a Benkelman beam. The mean deflections for winter, spring and summer seasons were 2.7, 5.1 and 5.4 mm, respectively, and the lower value for winter was attributed to the frozen pavement and lower soil moisture conditions. Pavement response in winter was a function of the interaction term of linear components of thickness of pavement layers and the peat substratum ( R 2=0.67), while in spring ( R 2=0.70) and summer ( R 2=0.72), it also included a moderating quadratic term of thickness of the peat substratum. Deflection generally increased with thickness of pavement and the peat substratum, and effect of pavement thickness was pronounced under peat layer greater than 1000 mm which was attributed to inherent weakness of the pavements over such areas. It is suggested that thickness of the peat substratum may be a basis for developing specifications for timber haulage vehicles, or routeing of such traffic for minimal environmental impact.

Effects of climate variability on the carbon dioxide, water, and sensible heat fluxes above a ponderosa pine plantation in the Sierra Nevada (CA)

Fluxes of CO 2, water vapor, and sensible heat were measured by the eddy covariance method above a young ponderosa pine plantation in the Sierra Nevada Mountains (CA) over two growing seasons (1 June–10 September 1997 and 1 May–30 October 1998). The Mediterranean-type climate of California is characterized by a protracted summer drought, with precipitation occurring mainly from October through May. While drought stress increased continuously over both summer growing seasons, 1998 was wetter and cooler than average due to El Niño climate patterns and 1997 was hotter and drier than average. One extreme 3-day heat wave in 1997 (Days 218–221) caused a step change in the relationship between H 2O flux and vapor pressure deficit, resulting in a change in canopy conductance, possibly due to cavitation of the tree xylem. This step change was also correlated with decreased rates of C sequestration and evapotranspiration; we estimate that this extreme climatic event decreased gross ecosystem production (GEP) by roughly 20% (4 μmol C m −2 s −1) for the rest of the growing season. In contrast, a cooler, wetter spring in 1998 delayed the onset of photosynthesis by about 3 weeks, resulting in roughly 20% lower GEP relative to the spring of 1997. We conclude that the net C balance of Mediterranean-climate pine ecosystems is sensitive to extreme events under low soil moisture conditions and could be altered by slight changes in the climate or hydrologic regime.

SEM Observations on the Root Hairs of Trifoliate Orange Grafted with Satsuma Mandarin under Low Soil Moisture and High Summer Temperature Condition

SEM Observations on the Root Hairs of Trifoliate Orange Grafted with Satsuma Mandarin under Low Soil Moisture and High Summer Temperature Condition

Does Wetting and Redrying the Seed before Sowing Improve Rice Germination and Emergence under Low Soil Moisture Conditions?

(2000). Does Wetting and Redrying the Seed before Sowing Improve Rice Germination and Emergence under Low Soil Moisture Conditions? Plant Production Science: Vol. 3, No. 2, pp. 161-163.

Soil Moisture, Relative Humidity, and Bentazon Affect Imazethapyr Absorption and Translocation in Common Ragweed (Ambrosia artemisiifolia)

Soil moisture, relative humidity (RH), and the addition of bentazon were examined for effects on absorption and translocation of14C-imazethapyr in common ragweed. When common ragweed was growing under conditions of low soil moisture (-300 kPa), absorption of14C-imazethapyr was reduced from 51 to 42%. Translocation of14C-imazethapyr was not affected by soil moisture. In the absence of bentazon, absorption and translocation of14C-imazethapyr was similar at 65 and 85% RH 48 and 168 h after treatment. Bentazon decreased absorption of14C-imazethapyr from 61 to 26% at 65% RH and from 65 to 57% at 85% RH 168 h after treatment. Bentazon decreased translocation of14C-imazethapyr from 35 to 9% at 65% RH and from 30 to 21% at 85% RH when averaged over time. This reduction in the absorption and translocation of14C-imazethapyr when bentazon was added may result in a reduction in common ragweed control compared to imazethapyr alone when RH is 65% or lower.

フィルムマルチ施用畑の雨水と土壌水分の挙動

Film mulch is being used in many farm lands because it improves the environment for cultivation by suppressing water evaporation from soil surface, maintaining a mild soil moisture condition, and maintaining the soil temperature higher than the bare soil surface, in addition to protecting against pests and diseases. Crop cultivation in cool high lands (such as the Shinshu Plateau) can be made possible with the introduction of film mulch. However, as the direct infiltration in the root zone are lower in fields where film mulch is used than in bare soil fields, and this raises fears that droughts would be exacerbated.Experimental comparisons of the soil moisture condition and flow between mulched bed and furrow space using the soil moisture measurement technique at many positions and many depths were carried out in the fall of 1995 in field planted with Chinese cabbage (Brassica pekinensis Rupr.), and in the spring of 1996 in field planted with cabbage (Brassica oleracea L.). The results are summarized as follows;(1) The shallow topsoil of the mulched beds had less soil moisture than furrow space and bare soil even after light rains at low soil moisture condition. The sowed areas (hold of the mulch film) in mulched beds, however, were moisture than the surrouding of sowed area. But one or two days after rainfall, soil moisture condition in mulched bed and furrow space were almost same.(2) As the crops grew, the soil moisture became lower than furrow space due to the water uptake by the crops' root system. In the soil layer below the root zone, i.e. at a depth of more than 0.3m, soil moisture is moved from the furrow space to the mulched bed by the gradient of soil moisture potential caused by the soil moisture uptake by the root system.These results propose that occasional plowing in the furrow space causes an increase in the infiltration rate of rain water, and facilitates the movement of moisture from the furrow space to root zone of the mulched beds.

Soil nitrogen dynamics in alley cropping and no-till systems on ultisols of the Georgia Piedmont, USA

On highly-weathered Ultisols of the Georgia (USA) Piedmont, a combination of no-till agriculture and alley cropping presents an option for rapidly increasing soil nitrogen availability while restoring long-term soil fertility. Three years after the establishment of Albizia julibrissin hedgerows and no-till agriculture trials, we measured inorganic soil nitrogen (NO3 -–N and NH4 -–N) and net nitrogen mineralization during a 4-month field study and a 14-day laboratory study . We also measured the influence of tree leaf amendments on grain sorghum production and N uptake. Soil nitrate increased four-fold within two weeks of adding Albizia leaf mulch. Soil ammonium did not increase as rapidly nor to the same extent after tree mulch addition. Averaged over the 4-month study, soil nitrate and ammonium were 2.8 and 1.4 times higher in the alley-cropped than in the treeless no-till plots. Net nitrification and mineralization were no higher in the alley cropping plots, during either field or laboratory incubations. Tree mulch additions enhanced crop biomass production and N uptake 2 to 3.5 times under both high and low soil moisture conditions. Our study demonstrates the dramatic short-term impacts of Albizia mulch addition on plant available nitrogen. Combined with no-till practices, alley cropping with Albizia hedges offers Piedmont farmers an option for reducing reliance upon chemical N fertilizer while improving soil organic matter levels.

Root and Shoot Development of Phaseolus vulgaris L. (French Beans) as Affected by Soil Moisture and Fertilizer Potassium

AbstractThe development of an extensive root system enables plants to overcome water stress. However, there is little information on the response of food legumes to soil moisture, especially during early growth, which determines crop establishment. Thus, an experiment was conducted under controlled conditions to identify the effect of soil moisture and fertilizer potassium on root and shoot growth of french beans (Phaseolus vulgaris L.) seedlings. The seedlings were grown in a sand medium under a high and low soil moisture regime and with 0.1, 0.8 or 3.0 mM potassium.Root lengths, dry weights and numbers of root hairs were greater under low soil moisture conditions. Potassium increased root growth irrespective of soil moisture regimes. The impact of potassium on root length was more pronounced under a high soil moisture regime. In contrast, potassium increased root dry weights and root hairs to a greater extent when plants were grown under dry conditions. The lack of adequate soil moisture increased specific leaf weights, and this phenomenon was reduced by the application of potassium. Shoot:root ratios also showed a similar phenomenon. The development of an extensive root system by french bean seedlings under dry conditions to extract a greater quantity of available soil moisture fur establishment and plant growth and the ability of potassium to promote this phenomenon is presented in this study.

The Effect of Elevated [CO2] on Growth and Photosynthesis of Two Eucalyptus Species Exposed to High Temperatures and Water Deficits.

Two species of eucalyptus (Eucalyptus macrorhyncha and Eucalyptus rossii) were grown for 8 weeks in either ambient (350 [mu]L L-1) or elevated (700 [mu]L L-1) CO2 concentrations, either well watered or without water additions, and subjected to a daily, 3-h high-temperature (45[deg]C, maximum) and high-light (1250 [mu]mol photons m-2 s-1, maximum) stress period. Water-stressed seedlings of E. macrorhyncha had higher leaf water potentials when grown in elevated [CO2]. Growth analysis indicated that increased [CO2] may allow eucalyptus species to perform better during conditions of low soil moisture. A down-regulation of photosynthetic capacity was observed for seedlings grown in elevated [CO2] when well watered but not when water stressed. Well-watered seedlings grown in elevated [CO2] had lower quantum efficiencies as measured by chlorophyll fluorescence (the ratio of variable to maximal chlorophyll fluorescence [Fv/Fm]) than seedlings grown in ambient [CO2] during the high-temperature stress period. However, no significant differences in Fv/Fm were observed between CO2 treatments when water was withheld. The reductions in dark-adapted Fv/Fm for plants grown in elevated [CO2] were not well correlated with increased xanthophyll cycle photoprotection. However, reductions in the Fv/Fm were correlated with increased levels of nonstructural carbohydrates. The reduction in quantum efficiencies for plants grown in elevated [CO2] is discussed in the context of feedback inhibition of electron transport associated with starch accumulation and variation in sink strength.

Soil water stress: Its effects on phenology, physiology, and morphology of containerized Douglas-fir seedlings

Containerized Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) seedlings were subjected to six moisture-stress treatments (ranging from 7 to 65% soil water content by volume) for 12 weeks. At the end of this period, there were significant differences in phenological, physiological, and morphological responses among the seedlings in the various moisture-stress treatments. In general, seedlings grown under very high or very low soil moisture conditions were adversely affected, while those grown under moderate conditions (29 to 53% soil water content) exhibited optimum growth, bud development, and nutrient and starch reserves. The use of vector analysis was found to be helpful in data interpretation. The results indicate the importance of closely monitoring nursery moisture regimes in order to achieve the best seedling quality.

Efficacy of Several Turf Insecticides Against Japanese Beetle Larvae, Home Lawn, 1995

Abstract Six turf insecticides were tested for efficacy against Japanese beetle larvae on a home lawn in Waltham, Mass. There were no Japanese beetle eggs or larvae present at the time of application, apparently because of low soil moisture conditions. The lawn consisted of 30% perennial ryegrass, 30% annual bluegrass, 30% crabgrass and 10% dandelion and was mowed at ca. 1.5 inches. Treatment plots were 8 ft by 8 ft, replicated 5 times, arranged in a RCB. All applications were made between 11:00 AM and 12:30 PM on 1 Aug 95. Liquid formulations were applied by hand with a watering can, 3 liters per plot. Granular formulations were applied using glass jars with perforated lids. Conditions at the time of application were as follows: air temp. 85° F, sunny and moderately humid with light SW wind (5-10 mph); soil type, silty loam; soil pH 6.6; water pH, 8.2. All plots were hand watered with 0.1 inch immediately after application, and an additional 0.2 inch was applied through overhead irrigation within 2 hr after application. No measurable rain fell in the area for 2 wk after application. Product efficacy was evaluated on 17 Oct (77 DAT) by removing 5 cupcutter plugs (4.25 inch diam) from near the center of each plot, dislodging soil with a hand trowel, and counting all grubs to a depth of 3 inches.

FLUOMETURON BEHAVIOR IN LONG-TERM TILLAGE PLOTS

Fluometuron (N, N-dimethyl-N'-[3-(trifluoromethyl) phenyl] urea) is a preemergence herbicide used widely for weed control in cotton (Gossypium hirsutum L.). Field research results suggest that many herbicides, including fluometuron, may be subject to preferential transport and leaching through the soil profile. The objectives of this study were to evaluate the distribution and leaching of fluometuron in a Lexington silt loam (Typic Paleudalf) through 3 years of study by analyzing depth incremented soil samples and tension-free pan lysimeter leachates collected at a soil depth of 90 cm under no-till (NT) and conventional tillage (CT, disc 2x - roller harrowed) management. Fluometuron depth distribution following application and subsequent rainfall was related to soil organic carbon content, with tillage effects restricted to the surface 2-cm. The amount of herbicide remaining in the soil profile after application decreased with increasing rainfall amounts. On average, 11% of applied herbicide in NT and 6% in CT remained in the surface 15 cm after 1 year. Fluometuron was detected in all lysimeter leachates during the 3-year period. Peak herbicide leachate concentrations ranged from 68 mg L -1 to 1700 mg L -1 , depending on herbicide application in relation to rainfall timing. Annual leaching losses ranged from 5 to 53% of applied fluometuron during the study. Of the amounts lost to leaching, 68 to 100% (averaging 87% of the total lost to leaching) were lost during the first two or three significant rainfall events after treatment. Rainfall timing in relation to herbicide application was the dominant effect in herbicide mobilization through the soil profile. Antecedent soil moisture content (predicted from rainfall amounts prior to fluometuron application) also influenced the appearance of leachate and herbicide in the lysimeters, with lower soil moisture conditions at application producing lower preferential flow. Depth-incremented soil sampling after initial rainfall events was a poor mechanism for detecting fluometuron mobility through the soil profile. The rapidity at which fluometuron was detected in the lysimeter leachates, the exceedingly high fluometuron concentrations, and the variability in leachate collection by the lysimeters, illustrated the significance of preferential flow. The influence of tillage practice on the volume of drainage collected by the lysimeters and on fluometuron leaching was of little significance when compared with the influence of natural infiltration heterogeneity.

Hydrological and hydrochemical response of a small canadian shield catchment to late winter rain‐on‐snow events

AbstractA study was undertaken during the winter of 1990–1991 in a small (3.7 ha) Canadian Shield catchment to examine the hydrological and hydrochemical response during rain‐on‐snow events. The results are presented of two large (37.9 and 34.6 mm) rain‐on‐snow events occurring in early and late March 1991. Peak and total runoff and the groundwater response from the two events are significantly different. Hydrological data indicate that these differences can be attributed to a combination of meteorological (temperature) and physical conditions (antecedent snowpack ripeness, soil moisture and groundwater levels). An immature snowpack (low temperature and density) combined with low antecedent soil moisture conditions significantly reduced the magnitude of the net hydrological input and runoff from the catchment during the early March event, whereas a more mature snowpack and high antecedent soil moisture conditions led to a large runoff event during late March.During both rain‐on‐snow events a significant portion of the pre‐event snowpack chemical load was lost. Based on the maximum snowpack chemical load measured before the events, the two large rain‐on‐snow events and a brief mid‐March warm period during which there were two much smaller rain‐on‐snow events removed 78% of the hydrogen ion and 63% of the sulphate and nitrate load from the snowpack, while only reducing snowpack water equivalence by 7%. A two‐component (rain and snowmelt) isotopic (δ18O SMOW %0) separation of snowmelt lysimeter water during the two events indicated that snowmelt was an important (50 and 65%, respectively) water source available for infiltration and runoff at the snow‐soil interface. Considering the high hydrogen ion loadings to the catchment during these two events (3.3 and 3.0 mequiv.m−2, respectively) streamflow pH was not significantly reduced due to an increase in the discharge of well‐buffered groundwater. A two‐component isotopic hydrograph separation of peak stream discharge during the 2–3 March event indicated that 75% of the total flow was groundwater. In mid‐latitude acid‐sensitive catchments, winter rain‐on‐snow events are an important hydrological occurrence due to their ability to elute much of the chemical load (H+, SO4, NO3) from the snowpack before the onset of spring melt when the maximum annual hydrological input typically occurs.

The Role of Phytophthora cryptogea and Waterlogging in Root Rot Kiwifruit

A 48 h or 96 h period of waterlogging induced a partial rotting of the root system of 18 month old potted kiwifruit cuttings. However, root regeneration compensated for the loss of damaged roots and the plants remained healthy. Inoculation with Phytophthora cryptogea under low soil moisture conditions caused a small amount of root rotting (11 %) and regeneration of the roots occurred. Root rot was significantly increased when inoculations were combined with extended periods of waterlogging. Root rot incidence was highest (89 %) in inoculated plants exposed to periods of 96 h waterlogging. Regeneration did not occur with any of these plants and consequently, the shoot systems were severely damaged.