Periods Of Waterlogging Research Articles

Seed germination and early establishment of 12 tree species from nutrient-rich and nutrient-poor Central Amazonian floodplains

Plants are subjected to extended periods of waterlogging and submersion in the floodplains of Central Amazonia. Several adaptations and growth strategies allow them to survive. In this study, germination and seedling growth of seeds of six tree species from nutrient-rich várzea and six from nutrient-poor igapó were analysed in the Amazon Research Institute (INPA) in Manaus, Brazil. Germination rates and duration were lower in species from várzea than from igapó. The cotyledons opened later and had lower longevity in várzea, where the environment provides sufficient nutrients to the establishing seedling and there is less need for nutrient supply by the mother plant. Species from várzea produced smaller seeds and the seedlings tended to grow less than in igapó where large-seeded species predominated. Mortality of waterlogged and submerged seedlings was low in all species, except in submerged seedlings of Senna reticulata. Leaf production and shedding was continuous in the várzea species, but in the species from igapó leaves had higher longevity. An explanation for the dynamic leaf phenology in várzea might be that this is an adaptation against the high sediment load which covers the leaves and impedes photosynthetic activity. Morphological adaptations to flooding (adventitious roots, lenticels, stem hypertrophy) occurred only in waterlogged seedlings from várzea species, maybe as a consequence of the oxygen deficiencies in the rhizosphere caused by the high plant productivity and decomposition in this ecosystem. The production of morphological adaptations might be limited by the low nutrient availability in igapó. The differences in germination and growth in várzea and igapó may be responses to the different nutrient availabilities in the two ecosystems and thus represent different survival strategies. In várzea, morphological adaptations which require high nutrient supply allow the plants to maintain growth and photosynthetic activity at high levels, even during waterlogging. Igapó species have a fast initial growth and constant leaf production, investing in high seed mass, leaf sclerophylly and reduced leaf loss. They tend to remain in a state of rest during flooding.

The Influence of Waterlogging on the Establishment of Four Australian Landscape Trees

An experiment was conducted to test the ability of recently planted trees to grow new roots under waterlogged conditions and to recover from waterlogging. Corymbia maculata (spotted gum, syn. Eucalyptus maculata), Lophostemon conjertus (brush box), Platanus orientalis (oriental plane), and Platanus x acerifolia (London plane) were subjected to a period of waterlogging and then to a recovery phase after waterlogging had ceased. Root length was measured at the end of both the waterlogging and recovery phases. The species were found to vary considerably in their ability to tolerate and recover from a period of waterlogging. Waterlogging suppressed root and shoot growth in all experimental species. Young spotted gum and oriental plane were able to initiate new roots under waterlogged conditions but London plane and brush box were not.

Yellow lupin (Lupinus luteus) tolerates waterlogging better than narrow-leafed lupin (L. angustifolius) II. Leaf gas exchange, plant water status, and nitrogen accumulation

Yellow lupin (Lupinus luteus) may have potential as a legume crop in waterlogging-prone areas of Western Australia. To elucidate the physiological response of yellow lupin and the widely grown narrow-leafed lupin (L. angustifolius) to transient waterlogging we conducted experiments in controlled environments. Narrow-leafed lupin and yellow lupin were grown in pots and waterlogged for 14 days from 28 to 42, or 56 to 70 days after sowing, each being followed by a 14-day recovery period. Root and shoot growth responses, leaf gas exchange, water relations, and N accumulation were assessed. During the period of waterlogging, net nitrogen accumulation ceased in both species at both ages. During recovery, yellow lupin accumulated more nitrogen than narrow-leafed lupin. Waterlogging reduced leaf gas exchange more with older plants than with younger plants, and more so with narrow-leafed lupin than yellow lupin. Some components of leaf gas exchange, particularly leaf conductance, were reduced by up to 80%. Waterlogging had no effect on leaf water potential of yellow lupin but reduced it in narrow-leafed lupin, from about –450 to –1100 kPa, especially during the recovery period. Yellow lupin was more adapted to transient waterlogging than narrow-leafed lupin because it maintained its leaf water status, it accumulated more nitrogen during recovery, and its photosynthetic activity recovered quickly afterremoval of waterlogging.

Microscopic observation of the decomposition process of leaf sheath of rice straw and colonizing microorganisms during the cultivation period of paddy rice

Microorganisms colonizing the leaf sheaths of rice plants placed in a waterlogged paddy field were studied using a scanning electron microscope. Decomposition was faster on the adaxial side than on the abaxial side of the leaf sheaths. The veins and trichomes were highly resistant to microbial decomposition throughout the waterlogged period of rice growth. The decomposition and disintegration of leaf sheaths markedly progressed from the third month (from July) after the placement in the paddy field. Microbial colonization was gradual in the first month after the placement of leaf sheaths in the field. One of the common first colonizers had a terminal endospore (Clostridium dissolvens-like microorganisms). Microbial colonization proceeded actively in the second month, and microbiota became diversified. Microbial colonization on the adaxial surface was more than that on the abaxial surface. Respective microorganisms colonized the surfaces separately from each others in this period. They grew mainly on the thin membrane that covered the epidermal layer. Microbial colonies spread all over the abaxial and adaxial surfaces, and there was no significant difference in the degree of colonization between the abaxial surface and the adaxial surface in the third month (in July). Although separate colonization of the respective microorganisms was common, the co-existence of different microorganisms within a colony was also observed. The thin membrane that covered the epidermal layer and the epidermis seemed to be the main substrate during this period. Co-existence of different microorganisms was a common occurrence in colony formation, and organic debris and remaining tissues of leaf sheaths were assumed to be the major substrates in August. These findings on microbial colonization were well correlated with the findings on the degree of decomposition.

Nitrogen availability and sorption under alternating waterlogged and drying conditions

The effect of alternating waterlogged and drying conditions on nitrogen (N) availability and sorption was studied in three soils of contrasting texture. Air‐dry samples of each soil were treated with three levels of nitrate (0, 30, and 300 mg kg‐1; N0, N30, and N300), waterlogged for 21 days, allowed to dry at room temperature for 21 days, and rewaterlogged for an additional 21 days. Ammonium (NH4) sorption isotherms were determined using the standard batch technique for air‐dry, waterlogged (with and without ponded water), and waterlogged/dried conditions. Waterlogging reduced the Eh and increased the pH of all soils. The magnitude of change in Eh and pH was related to soil organic carbon levels and nitrate (NO3) concentration as this chemical became the principal electron acceptor following depletion of dissolved O2. Ammonium concentrations generally increased over the waterlogged periods due to mineralization of organic nitrogen and its subsequent accumulation under O2‐deficient conditions. Where NH4 concentrations decreased, losses were attributed to nitrification and denitrification reactions in aerobic and anaerobic soil zones. Denitrification was assumed to have caused the loss in NO3 over the waterlogged period. Reoxidation caused only small changes in NH4 and NO3. Rewaterlogging increased NH4 concentrations, whereas further losses in NO3 were observed in N300 only. Waterlogging reduced NH4 sorption in the krasnozem A horizon soil, and increased sorption in the wetland soil. Waterlogging did not significantly affect NH4 sorption in the remaining soils. Ammonium sorption was greatest in soils which had been waterlogged then dried. The extent of sorption depended on CEC and the relative affinity of NH4 for the sorption sites. This study has provided further evidence that inclusion of alternating waterlogged and drying conditions in the management of constructed wetlands could represent an effective method of maximizing N removal from wastewaters. Furthermore, results suggest that maximum removal of N would be achieved by optimizing contact time between the wastewater and wetland soil materials, and avoiding overland flow as much as possible.

Phosphorus availability and sorption under alternating waterlogged and drying conditions

The effect of alternating waterlogged and drying conditions on phosphorus (P) availability and sorption was studied in three soils of contrasting chemical and physical properties. Soils were treated with two levels of P (0 and 50 mg kg‐1; P0 and P50), waterlogged for 21 days, then allowed to dry at room temperature for 14 days. The availability of P, iron (Fe), and manganese (Mn) over the waterlogged and drying periods was determined by shaking samples of each soil with 1M NaOAc (pH 3). Increasing concentrations of 1M NaOAc (pH 3) extractable P (Pac) over the waterlogged period was attributed to solubilization of Fe(OH)3 materials under reducing conditions with the release of sorbed and occluded P. The released P appeared to be resorbed by freshly precipitated amorphous Fe(OH)2 material since earlier studies showed that water soluble P concentrations in these soils were reduced to negligible levels under waterlogged conditions. The Fe(OH)2 material remained readily extractable with 1M NaOAc (pH 3) since Feac increased dramatically with waterlogging. Drying the waterlogged soils caused a rapid decrease in Pac, Feac and Mnac suggesting the Fe(OH)2 may have been transformed into more stable forms [e.g., Fe(OH)3]. Much of the changes in Pac appeared to be due to changes in Feac, with limited influence from Mnac. and mineralization of organic P. Phosphate sorption isotherms were determined using the standard batch technique for air‐dry, waterlogged (with and without ponded water), and waterlogged/dried conditions. Sorption isotherms were not affected by waterlogging and subsequent drying. Most soils sorbed all of the added phosphate irrespective of moisture treatment.

Residual effect of nitrogen fertilisation in a wheat–sunflower cropping sequence on a Vertisol under semi-arid Mediterranean conditions

The residual effect of the common N fertilisation (a three-split application of a total of 100 kg N ha −1) for winter wheat on the following sunflower crop was studied in a Vertisol under semi-arid Mediterranean growing conditions. For this study an experimental plot having a 15N labelled microplot was installed. Of the fertiliser N applied to the previous winter wheat crop, 69.2 and 0.8% was left at winter wheat harvest in the soil profile (up to 90 cm) and the wheat stubble, respectively. The recovery of the residual labelled fertiliser N by the subsequent sunflower crop ( Helianthus annuus, L.) was 3.6% of the fertiliser added to the previous winter wheat crop. The possible reasons for this low plant recovery were immobilisation of the fertiliser N and the limited N uptake by the drought affected sunflower crop. At harvest of the sunflower 49.7% of the added labelled fertiliser was still left in the soil profile up to 90 cm depth. The total recovery of fertiliser N over the two growing seasons was 83%. About 15% of the residual fertiliser N at wheat harvest was not recovered at sunflower harvest. Unrecovered 15N was presumably lost by denitrification during periods of temporary waterlogging of the surface soil during irrigation and due to leaching beyond 90 cm depth. It is concluded that, in spite of the carry-over effect of fertiliser N from one growing season to another under the given conditions, the immediate residual effect of fertiliser N on the following crop was low. This means that for optimal financial profit fertiliser N must be applied at rates on an annual basis, according to the crop needs.

Stability behavior of soil colloidal suspensions in relation to sequential reduction of soils

The cause of the decrease in the Fe2+ concentration of the soil solution in the later period of soil waterlogging was investigated. After 7-d incubation of the soil solutions separated from previously waterlogged soils (PWdS), a greyish precipitate (PPT) was observed in the soil solutions. The color of the PPT became reddish brown after separation from the solutions and freeze-drying. The PPT observed in 14-d-PWdS contained 352.6 g Fe kg-1, 62.5 g C kg-1, 22.6 g P kg-1, 11.3 g Si kg-1, 9.9 g N kg-1, 0.7 g Al kg-1 and a trace amount of Mn. However, Ca, Mg, K, and Na could not be detected. It was concluded that the separated PPT was dominated by amorphous ferric hydroxide based on the chemical analysis, broad IR absorption band at 585 cm-1 and exothermic peak at 301°C. The data of chemical analysis and the characteristic IR bands of the PPT suggested that organic substances and presumably aluminosilicate anion were adsorbed onto the freshly-formed ferric hydroxide. The dominant phase of the greyish PPT in the reductive soil solution was considered to be ferrous PPT and was assumed to consist mainly of carbonate and/or hydroxide, and concomitantly of phosphate. The formation of the ferrous PPT in the soil solution in the later period of soil waterlogging was considered to (i) cause the decrease of concentration of Fe2+ ion and of other divalent cations such as Ca2+ due to the re-adsorption of Ca2+ on soil clays through the cation exchange reaction with Fe2+ ion, and consequently (ii) enhance the dispersion of the soil colloidal suspension.

Tree rooting patterns and soil water relations of healthy and damaged stands of mature oak (Quercus robur L. and Quercus petraea (Matt.) Liebl.)

At three sites in northwestern Germany, which represent the centres of the present oak damage, root distribution and biomass beneath healthy and damaged trees of mature pedunculate oak (Quercus robur L.; Neuenburg site) and sessile oak (Q. petraea [Matt.] Liebl.; Lappwald and Sprakensehl sites) were investigated, and soil texture, bulk density, duration of waterlogging periods and the water available in the mineral soil were determined. For Neuenburg and Sprakensehl, the available soil water was related to leaf water parameters determined in a separate investigation. At the clayey and hydromorphic sites of Neuenburg and Lappwald, the measurements were performed in each one healthy and one damaged part of the site, which differed in the number of oaks with crown damage. In the damaged stand of Neuenburg, the clay content of the subsoil was higher than in the healthy stand, and the soil water availability was reduced especially in dry periods. Compared to healthy oaks of the healthy stand, the density of finest plus fine roots as well as the biomasses of finest roots were lower beneath damaged oaks of the damaged stand. With decreasing relative available soil water (actually available water in relation to water available at the saturation state), the relative leaf water content decreased in damaged, but not in healthy oaks. At Lappwald, similar differences in soil water availability between the healthy and the damaged stand were found, but had no effect on the distribution or biomass of the roots. At the sandy site (Sprakensehl), the available soil water decreased drastically during a dry period, and predawn leaf water potentials of both healthy and damaged oaks declined with decreasing relative available soil water. However, the damaged oaks were not inferior to the healthy ones with respect to root density and biomass. It is concluded that, in the damaged stand of Neuenburg, the high clay content of the subsoil, which results in prolonged periods of waterlogging, in sharp changes from waterlogging to drought and decreased water availability in dry periods, is the reason for the reduced biomass and density of roots of the pedunculate oak. Thus, in northwestern Germany, unfavourable soil water relations are considered as a factor contributing to crown damage of pedunculate oak at hydromorphic sites, but not to damage of sessile oak.

Stability behavior of soil colloidal suspensions in relation to sequential reduction of soils

The electrokinetic behavior of colloidal particles in three waterlogged soils at 38°C was investigated with reference to the stability changes of soil colloidal suspensions under reductive conditions. The dispersed clay particles of the three soils exhibited a negative zeta (ζ) potential. The absolute value of the ζ-potential, |-ζ|, of these soils in the earlier period of waterlogging decreased, which caused the flocculation of clay particles. The concentrations of divalent cations, i.e., Fe2+ and Ca2+ in the soil solutions were estimated to be higher than their critical flocculation concentrations (CFCs) on the basis of the observed CFCs of Fe2+ and Ca2+ for the clay suspension of halloysite as a reference. With the progression of the reduction process, clay particles of one soil still exhibited a low |- ζ| and flocculated. The concentrations of Fe2+ and Ca2+ in the soil solutions were estimated to be higher than their CFCs, respectively. The clay particles of two sandy soils, however, showed an increase in |- ζ| due to the increase in pH and dispersed. The concentrations of Fe2+ and Ca2+ in the soil solutions were estimated to be lower than their CFCs, respectively. The stability changes of the soil colloidal suspensions by these divalent cations under sequential soil-reduction can be explained by the alteration of the Stern potential (- ψ s ), which determines the repulsion energy related to the potential energy of interaction between two particles. The apparent decrease in the Ca2+ concentration of the soil solutions in the later period of waterlogging was explained largely by the re-adsorption of water-soluble Ca2+ on the exchange sites of soil clays with the decrease in the Fe2+ concentration in the soil solution.

Stability behavior of soil colloidal suspensions in relation to sequential reduction of soils

Flocculation and dispersion of colloidal particles of nine inorganic paddy soils were studied mainly based on turbidity measurements of the suspensions of soils which were previously incubated at 28°C under in vitro waterlogged conditions. After 1-week of incubation, the turbidity of the soils except for 1) two soils containing larger amounts of sodium salts and 2) one soil containing larger amounts of Fe and Al oxides, significantly decreased, and colloidal particles flocculated with 1) a decrease in soil Eh and 2) an increase in electric conductivity (EC). During the 3- to 4-week period of waterlogging, the turbidity of the three soils significantly increased with the 1) decrease in EC and 2) increase in pH of the soils although the Eh remained low. Infrared (IR) absorption analysis showed that the suspended colloidal particles consisted of layer silicates from respective soil clays. Oxidation of suspensions of waterlogged soils by air-bubbling led to an increase in turbidity with the 1) increase in Eh, and 2) decrease in pH, EC, and water-soluble Fe2+ concentration. It was suggested that the stability of the soil colloidal suspensions was affected by soil reduction with alterations in ionic species and their concentrations at clay surfaces and in soil solutions.

Reaction of root systems of grand fir ( Abies grandis Lindl.) and Norway spruce ( Picea abies Karst.) to seasonal waterlogging

Effects of seasonal waterlogging on rooting depth and rooting intensity (root counts per unit profile wall area) were analysed on profile walls in 14 stands of pure grand fir ( Abies grandis Lindl.) and pure Norway spruce ( Picea abies Karst.), varying from 20 to 31 years old, in a mountainous region in western Germany. The sites vary from non-waterlogged to strongly seasonally waterlogged. We found that seasonal waterlogging in compacted soils is a main stress factor that strongly influences the root distribution of both species. However, roots of grand fir were more tolerant, expanded to greater depths (in general more than 20 cm), and attained higher densities (more than 30%) than roots of Norway spruce. The roots of grand fir even penetrated into the compact Sd-horizon of pseudogleys, whereas the Sw-horizon (seasonally waterlogged horizon) prevented deeper rooting of spruce and contributed to its plate-shaped root system. In addition, a study on the dynamics of fine root biomass and chemistry from waterlogged and non-waterlogged periods was carried out by core sampling in a 25-year-old grand fir stand. During the waterlogged period, the fine roots had considerably greater dead (5558 kg ha −1) than live biomass (3594 kg ha −1). At the beginning of the non-waterlogged period, the total biomass of live fine roots increased by 50%, and the dead fine roots decreased by 27%. The influence of waterlogging on the vitality of the fine roots is recognizable in their chemical composition: under waterlogged condition, live fine roots contained distinctly less K, Mg and Zn, but more Mn, than during the non-waterlogged period.

Microbial role in immobilization of technetium in soil under waterlogged conditions

Technetium behaviour in soil depends upon its chemical forms. The nuclide is expected to be in a soluble form of pertechnetate (TcO 4 −) under an aerobic condition, however, this changes through a combination of factors such as a redox condition and microbial activity. In this study, a radiotracer experiment was carried out to clarify the influence of microbial activity on plant available Tc under waterlogged condition. Air-dried soil with 0, 0.05, 0.5% glucose contents and sterile soil were used to compare the effect of microbial activity. The soils were waterlogged with 95mTc or 95mTc solution and kept at room temperature. Relative activities of the bottom solutions which had collected 1 hour after waterlogging indicated high correlations with the amounts of total-C, total-N, active-Al. Relative activities of Tc in the surface solutions of the air-dried soils decreased with increasing glucose concentration, however, those of sterile soils were almost constant during the experiment. Our results showed Tc adsorption onto the soil is influenced by the activity of microorganisms, that is, the redox potential of the soil is lowered by their activity. Most of the Tc in the surface solution is sorbed on the surface soil strongly and this can be a cause of reduced Tc availability to rice plants during the waterlogged period.

Flood‐induced leaf elongation in Rumex species: effects of water depth and water movements

SUMMARYSeveral species from the genus Rumex are found in Dutch river forelands. Species such as R. palustris Sm. From the low, frequently flooded areas are well adapted to wet conditions, Rumex species from higher and less frequently flooded sites are poorly adapted and therefore sensitive to flooding. One of the adaptations to flooding is enhanced shoot elongation upon complete submergence, enabling plants to restore leaf‐air contact, provided that the water is not too deep. This paper demonstrates the strong variation in the absolute extent of flood‐induced leaf elongation among species of the genus Rumex. The effects of flooding on shoot dry and fresh weight and internal gas volumes of an elongating and a non‐elongating species, R. palustris and R. acetosella L., were compared. Net water uptake in response to complete submergence was observed in the shoots of both species. Based on results presented here, we conclude that in plants of R. palustris water enters the cells and is used for cell expansion leading to petiole elongation, whereas in plants of R. acetosella at least part of the water taken up fills the intercellular gas spaces. Elongation of completely submerged Rumex plants does not vary with different depths of submergence, This was concluded from the observation that there is little effect of either hydrostatic pressure or irradiance on leaf elongation during complete submergence. However, when R. palustris plants were subjected to a changing water depth, i.e. alternate periods of complete submergence and waterlogging, they elongated less strongly than under permanent complete submergence. Water movements did not affect leaf elongation induced by submergence.

Soil Carbon Storage and Turnover in Temperate Forests and Grasslands-A New Zealand Perspective

Carbon storage and turnover times of total soil C (up to 1 m depth) and topsoil C (to 23 cm depth of mineral soil) were compared at six sites in native tussock grasslands and three in old-growth forests in New Zealand. Annual C inputs to the topsoils were also determined. Most of the sites approached steady state, and covered a wide range of climoedaphic environments. Total soil C ranged from 44 to 268 t ha1 (to 1 m depth), and was highest in a Spodosol beneath a mixed podocarp-hardwood forest. Turnover times of total soil C, estimated from the radiocarbon content of soil organic matter, mostly ranged from 30 to 125 years. Anomolously slow turnover times for two grassland sites and one forest site were ascribed partly to an accumulation of Al-humus, and partly to intermittent periods of waterlogging. Annual inputs of C to the upper part of the soil profile averaged 7 and 3 t ha 1 for the forest and grassland soils, respectively. Turnover times for decomposable C [(total C inert C)/annual C input] in the topsoil ranged from 11 to 40 years, and were closely related to mean annual temperatures. Application of the approaches described for assessing soil C storage and turnover in a wider range of climates and vegetation types now seems warranted.

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.

Application of anhydrous ammonia or urea during the fallow period for winter cereals on the Darling Downs, Queensland .II. The recovery of 15N by wheat and sorghum in soil and plant at harvest

Three field experiments were conducted on the Darling Downs (Queensland) to evaluate fertilizer management practices such as application depth and addition of nitrification inhibitor (N-serve), for nitrogen (N) applied in the February-May fallow period for winter cereals. Anhydrous ammonia or urea was applied in February, March or May at two depths (7 or 17 cm), with or without N-serve. Soil fertilized in February generally had a lower mineral-N content at sowing than soil fertilized in May. Deeper application (17 cm) in February did not increase soil mineral-N content to 0.2 m depth in May but addition of N-serve did at one site where it appeared to slow the movement of mineral N into the subsoil (0.2-0.4 m). A companion experiment was conducted at each site in which 15N-enriched urea was applied to a small (1 m2) area at the centre of a 4 m2 fertilized plot. Effects of fertilizer placement and N-serve treatment, as were used in field experiments, were evaluated in terms of crop recovery of 15N and total 15N recovery in plant and soil at harvest. Recovery of 15N by wheat, sown at two sites in June, showed that neither fertilizer management practice, application depth nor N-serve affected 15N recovery. At only one site did wheat recover less February-applied N than May-applied N. N-serve had no effect on 15N recovery by sorghum sown in October, of N applied in February or May, but 15N recovery was increased by deeper fertilizer placement. Total recovery of 15N in soil and plant after wheat harvest was lower (-74%) for February-application than for May-application (>94%). Similarly, total 15N recovery after sorghum was lower the earlier the fertilizer was applied. Unrecovered 15N was presumed lost due to denitrification during periods of temporary waterlogging of surface soil. Use of N-serve with the fertilizer application had no effect in conserving 15N applied for wheat or sorghum. However, deeper (17 cm) placement of N than normal (7 cm) promoted higher total recoveries, and therefore reduced losses, of applied 15N at the three sites.

Effects of nitrogen fertilization on growth and yield of cassava in Hawaii: I dynamics of soil nitrogen

Abstract A field experiment was conducted in 1987 on a Vertic Haplustoll on the Island of Oahu (Hawaii) to monitor the dynamics of 1M KCl extractable NH4‐N and NO3‐N, and organic carbon (OC) and total nitrogen (N) contents following the application of increasing rates of N fertilizer as urea (0, 50, 100, and 150 kg N/ha) and subsequent cropping with irrigated cassava. Soil samples were taken at 0–15, 15–30, 30–45, and 45–60 cm soil depths at 60, 120, 180, 240, and 300 days after planting (DAP). Cumulative rainfall values for the periods 0–60, 60–120, 120–180, 180–240, and 240–300 DAP were 151, 0, 156, 142, and 1032 mm, respectively. Two waterlogged periods occurred, one just before 180 DAP and the other after 240 DAP. NH4‐N accumulated to high levels after the first waterlogged period but no NO3‐N was detected. NH4‐N declined sharply after the second waterlogged period. Both OC and total N contents decreased over time and were not affected significantly by N fertilization. Changes in OC and total N conten...

Seasonal Soil Waterlogging Influences Water Relations and Leaf Nutrient Content of Bearing Apple Trees

Abstract Bearing ‘Macspur’/M.26 apple trees (Malus domestica Borkh.) were grown in plastic-lined basins under orchard conditions. Four treatments were imposed in each of 3 years consisting of controls and 6-week periods of soil waterlogging in the spring, summer, or fall. Stomatal conductance (gs), transpiration rate (E), leaf water content (LWC), and stem water potential (ψstem) were measured at the end of each waterlogging period. Stomatal conductance was significantly reduced by spring and summer waterlogging, but not by fall waterlogging. Reduction in g, and E generally increased over years. Stem water potential after spring and fall waterlogging averaged 8% less negative than controls in all 3 years, with no trend over the 3 years. In contrast, of summer-waterlogged trees was unaffected, 45% was more negative, and 31% less negative than controls in the first, second, and third year of treatment, respectively. Annual reductions in growth and yield due to the waterlogging treatments were related to decreased gs and to both negative and postive changes in ψstem. Leaf levels of N, P, K, and Cu measured in July were reduced only by summer waterlogging, with no trend in reponse over years.

The influence of aggregate size and drannage potential on germination of barley seeds in flooded soil

Emergence and growth of barley was severely decreased by short periods (less than 24 hours) of pre-emergence waterlogging at 20°C. The extent of damage depended on a combination of duration of waterlogging, soil water potential and aggregate size. Potentials of less than—4kPa prevented loss of plants developing in aggregates of less than 2 mm diameter after a transitory period of waterlogging although some shoot and root damage occurred. By comparison seeds growing in soil consisting of aggregates greater than 2 mm in diameter were not damaged by transitory waterlogging even when drainage only occurred at−0.8kPa. The severity of damage increased with the period of waterlogging. A criterion obtained as the product of mean size grade and water potential gave a single value (−4NM−1) below which emergence was satisfactory. Waterlogging halfway through germination gave more severe damage than near sowing date or near emergence.