Soil Moisture Tension Research Articles

Facility for Hydraulic Tests of a Frozen Soil

Predicting erosion from previously frozen and thawing soils has been a problem for decades. To study the effect of freezing and thawing on erodibility, a tilting flume with a radiative freezing apparatus was designed and constructed. The test bed of the flume was designed to allow a soil mass to be frozen and thawed from the surface under controlled soil moisture tension. Loose soil placed in the test bed was consolidated by cyclical increase and decrease of soil moisture tension.

Interpreting Tension-infiltrometer Data for Quantifying Soil Macropores: Some Practical Considerations

A tension-infiltrometer offers a practical means for obtaining information on soil infiltration characteristics at low soil moisture tensions in the field. This study examines interpretation of tension-infiltrometer results. Saturated hydraulic conductivities (Ks) calculated from unconfined tension-infiltrometer measurements were not statistically different from conductivity measurements made with a velocity-head permeameter. Ks values determined with the tension-infiltrometer were greater than conductivities measured with a Guelph permeameter. Tension-infiltrometer measurements of infiltration made through a 20-mm layer of sand were an order of magnitude less than ponded infiltration measurements at the same location. Increases in antecedent soil moisture decreased infiltration values, but parameters for equations fitted to the hydraulic conductivity versus tension curve were similar. Unconfined infiltration rates when adjusted to give vertical conductivity did not change appreciably the values of parameters fitted to a hydraulic conductivity versus soil moisture tension curve.

Survival of clover rhizobia and their plasmid-cured derivatives in soil under heat and drought stress

Strains of Rhizobium leguminosarum by. trifolii often contain plasmids other than the symbiotic plasmid. The ecological function of these plasmids is not known. Three strains of R. leguminosarum bv. trifolii containing from 3 to 5 plasmids were used to obtain derivatives cured of individual plasmids and in some cases cured of more than one plasmid. The ability of the strains and their plasmid-cured derivatives to survive in soil under heat and moisture stress was tested. Resistance to heat stress was tested by incubating these bacteria in soil at 38 or 42°C and drought resistance was tested by subjecting them to a soil moisture tension of −1.5 MPa at 28°C. The results suggested an involvement of some plasmids in mediating the response to the stress conditions. Some cured derivatives survived better than the parent but for others the parent survived better than cured derivatives. Evidence for involvement of plasmids was stronger for resistance to heat stress than moisture stress.

Growth of Chrysanthemum at Low, Relatively Steady Nutrient Levels in a Commercial-style Substrate

Nutrient solution with a molar ratio of 10 N: 1 P: 3 K was applied in scheduled intervals at rates of 0.5, 1, 4, or 20 mm N (NO3 + NH4) to Dendranthema ×grandiflorum (Ramat.) Kitamura `Sunny Mandalay' plants seven (7/day) or 14 times/day (14/day). These plants were compared to a 20 mm N control in which nutrient solution was applied when the soil moisture tension reached 30 kPa. Plants with 7/day had significant quadratic relationships for height, width, and dry weight, with the lowest responses at the low nutrient concentration. With 14/day, height and dry weight did not differ, although width did increase linearly with nutrient solution concentration. However, linear regression slopes for all three variables were much lower with 1Vday than with 7/day. At midcrop in both experiments, significant regression curves indicated that the lower concentrations of nutrient solution resulted in lower tissue N and K levels; however, slopes of the linear regressions were lower with 14/day than with 7/day. With 7/day, the water content (percentage) of plants in the schedule-fertilized treatments was higher in plants receiving higher nutrient concentrations, as indicated by the significant linear and quadratic regression curves. With 14/day, the water content was linearly related to solution nutrient concentration, but with a lower slope than with 7/day. These three trends indicate that steady-state nutrition was more closely achieved in a commercial-style substrate with 14/day applications of nutrient solution. These results suggest that plant growth that meets commercial expectations can be achieved at lower soil solution nutrient concentrations than currently applied.

SEASONALLY SATURATED SOILS IN THE PUGET LOWLAND I. SATURATION, REDUCTION, AND COLOR PATTERNS

The depth and duration of seasonal saturation are important factors affecting land use and management decisions. Soil chromas ≤2 have been used to indicate the depth of seasonal saturation, but in many soils this relationship is not valid. This study was conducted to determine the relationships among seasonal saturation, soil color patterns, and soil redox in soils derived from glacial till, alluvium, and volcanic mudflow material in the Puget Sound Lowland of western Washington. Soil profiles were described at key positions on landscapes typical of each parent material. Water tables, soil redox potentials, ground water dissolved oxygen (DO), and soil moisture tensions were measured in selected soil horizons and the results compared with soil color patterns. Seasonal high water tables could be predicted using chroma 2 colors on the glacial till and volcanic mudflow landscapes. Soil colors did not appear to indicate current redox conditions in the alluvial sites, although they could be used to predict seasonal high water tables on the overwash plain landscape. The duration of DO levels <5 mg/L could be related to soil redox status. Soil horizons with DO <5 mg/L for more than 80% of the time they were saturated-had low soil redox potentials and were clearly reduced for at least part of the year. Soil horizons with DO <5 mg/L for 60–80% of the time were reduced only in microsites. Other soil horizons remained oxidized throughout the year.

EFFECT OF AN IRRIGATION SYSTEM CONTROLLED BY SOIL MOISTURE TENSION IN REDUCING WATER USAGE AND RUN-OFF IN POINSETTIA PRODUCTION

An irrigation system for monitoring and controlling soil moisture tension in the root zones of potted plants using computer and solid-state tensiometer technologies was evaluated in a commercial greenhouse on 'V-14 Glory' poinsettias over a 10 week period. Replicated benches with separate drip circuits controlled by the computer maintained the soil moisture tension of the potted poinsettia plants between 1 kPa and 5 kPa. The amount of water used by each bench and the amount leached was compared to benches with separate drip circuits that were manually operated by the grower according to standard commercial practice. There was a 65% savings in the total amount of water used for the computer-controlled system and an average weekly reduction of 98.6% in leachate. The differences were significant and there was no measurable reduction in plant quality, even though soil analyses showed slightly elevated EC levels.

Fruit Cracking in Tomato

The environmental and physiological causes of cracking or splitting of soft fruits and citrus as they ripen are not well understood. This paper explores factors contributing to radial cracking in tomatoes, gives suggestions for prevention of cracking, and suggests directions for future research. Fruit cracking occurs when there is a rapid net influx of water and solutes into the fruit at the same time that ripening or other factors reduce the strength and elasticity of the tomato skin. In the field, high soil moisture tensions suddenly lowered by irrigation or rains are the most frequent cause of fruit cracking. Low soil moisture tensions reduce the tensile strength of the skin and increase root pressure. In addition, during rain or overhead irrigation, water penetrates into the fruit through minute cracks or through the corky tissue around the stem scar. Increases in fruit temperature raise gas and hydrostatic pressures of the pulp on the skin, resulting in immediate cracking in ripe fruit or delayed cracking in green fruit. The delayed cracking occurs later in the ripening process when minute cracks expand to become visible. High light intensity may have a role in increasing cracking apart from its association with high temperatures. Under high light conditions, fruit soluble solids and fruit growth rates are higher. Both of these factors are sometimes associated with increased cracking. Anatomical characteristics of crack-susceptible cultivars are: 1) large fruit size, 2) low skin tensile strength and/or low skin extensibility at the turning to the pink stage of ripeness, 3) thin skin, 4) thin pericarp, 5) shallow cutin penetration, 6) few fruits per plant, and 7) fruit not shaded by foliage. Following cultural practices that result in uniform and relatively slow fruit growth offers some protection against fruit cracking. These practices include maintenance of constant soil moisture and good Ca nutrition, along with keeping irrigation on the low side. Cultural practices that reduce diurnal fruit temperature changes also may reduce cracking. In the field, these practices include maintaining vegetative cover. Greenhouse growers should maintain minimal day/night temperature differences and increase temperatures gradually from nighttime to daytime levels. For both field and greenhouse tomato growers, harvesting before the pink stage of ripeness and selection of crack-resistant cultivars probably offers the best protection against cracking. Areas for future research include developing environmental models to predict cracking and exploring the use of Ca and gibberellic acid (GA) sprays to prevent cracking.

モモ果実の渋味とポリフェノール含量に及ぼす土壌乾燥の影響

モモ果実の渋味とポリフェノール含量に及ぼす土壌乾燥の影響

Soil Moisture Uptake by Green Ash Trees After Transplanting

Abstract Forty-five Summit green ash trees (Fraxinus pennsylvanica Marsh. ‘Summit’) were planted on a compacted clay soil site. Unamended soil, amended soil, and friable topsoil were used as backfill, in combination with holes slightly larger than the root ball, twice, and 3 times the diameter of the root ball. Soil moisture tension (SMT) was monitored in the root ball, in the backfill, and outside of the planting hole. Soil moisture tension reached at least −50 KPa within the root ball in as little as two days. Improved backfill soil and large planting holes resulted in earlier significant uptake of soil moisture outside of the root ball compared to nearby soil where roots were excluded. SMT inside the root ball were significantly more negative than the surrounding soil for all treatments until twenty weeks after transplanting. At 68 weeks after transplanting, differences in SMT between the root ball, the backfill, and the soil outside the planting hole became insignificant for all treatments. Soil moisture tensions levels reported to inhibit root growth were frequently measured in the root zone throughout the first two growing seasons after transplanting.

A laboratory study of the residual influence of some amendments on the reconsolidation of disturbed Salisbury silt loam

The residual effect of various soil amendments on the reconsolidation of a strongly acidic Salisbury silt loam C horizon which contained 0.25% free aluminium was investigated in the laboratory. Limestone (CaCO 3), gypsum (CaSO 4) and peat moss were added at 0.5, 0.08 and 2.0% (w/w), respectively. In a fourth treatment, CaCO 3 (0.5%, w/w) was added 24 months previously. Results from these treatments were compared to those from an untreated control. All soils were redisturbed to simulate tillage. The soils were subjected to a standard Proctor test and a low-energy compaction test designed to simulate a 0.44 m soil overburden. Penetrometer studies were performed to examine soil strength. The mineralogy of the Salisbury C-horizon was dominated by illite, with lesser amounts of chlorite occurring; kaolinite and vermiculite were present only in small amounts. Application of peat lowered the maximum dry density of the Proctor test and increased the concomitant optimum moisture content. Soil chemical amendments had no effect on compaction as measured by the Proctor test, but significantly increased the dry bulk density in the low-energy compaction test. Hence volumetric moisture content, at a moisture tension of 101 kPa, was increased by the chemical amendments. Soil strength, as measured by the cone index at a constant soil moisture tension, was decreased by the chemical amendments; however, after correction for volumetric moisture content, no treatment effect occurred. The chemical amendments significantly decreased the concentrations of inorganic and organically bound Al and inorganically bound Fe. The results of the low-energy compaction test suggest that application of gypsum or limestone amendments to severely disturbed, highly acidic soils, which contain appreciable amounts of aluminium oxides and exchangeable aluminium, may increase the soil's propensity to reconsolidate. This was not revealed by the standard Proctor test.

Effects of conservation tillage on hydraulic properties of a Griswold silt loam soil

The effects of conservation tillage (CT) systems on crop production and erosion control have been well documented, but limited information is available concerning the effects of different CT systems on the hydraulic properties of layered soils. The effects of three CT treatments: chisel (CH), no-tillage (NT) and till-plant (TP) as compared with conventional modlboard plowing (CN) were investigated on a Griswold silt loam soil (Typic Argiudoll), formed in loess overlaying glacial till. Hydraulic properties were determined in situ. In addition, hydraulic conductivity was determined in the laboratory where more detailed hydraulic conductivity changes were monitored for the lower soil moisture tension range near soil saturation. At or near saturation, there was no difference in hydraulic properties for all four tillage treatments. For example, mean saturated hydraulic conductivities (from laboratory determination) were 25.5, 25.1, 24.2 and 22.8 cm day −1 for CN, CH, TP and NT, respectively. However under unsaturated conditions, tillage treatments and soil layering (discontinuity between surface loess and glacial till beneath) affected hydraulic properties. In situ hydraulic conductivity ( K) ranked CH>CN = NT = TP for the 0.32–0.33 m 3 m −3 moisture content range. There were no differences in K for all treatments at other moisture ranges considered and at moisture contents ⩽0.31 m 3 m −3, in situ specific moisture capacity was, however, significantly lower in NT than in the other three treatments. Throughout the 20-day free drainage period for in situ K determination, the effect of layering is exhibited by the mean K values at the 50-cm depth being higher than those at 25 cm. There were negligible treatment-block interaction effects on the hydraulic properties as the soil became drier. Spatial variability in hydraulic properties was also noted for all treatments and soil depths considered.

Effect of varying water regimes on soil physical properties and yield of rice in mollisols of Tarai region

Field experiments were conducted under shallow and medium water table soils in order to identify suitable water regime(s) for wetland rice cultivation. The physical properties such as the puddling index, bulk density, porosity, moisture retention, hydraulic conductivity and infiltration rates were studied to ascertain the changes brought about by puddling under six imposed soil-water regimes; ranging from continuous submergence of 5 ± 2 cm water (Ic) to completely rainfed (Io). In intermittent irrigation regimes (Ic 1, Ic 3, Ic 5 and Ic 7) irrigation was applied respectively 1, 3, 5 and 7 days after water vanished from the surface of the soil. The depth of the naturally occurring water table fluctuated during the rice season. Shallow water table varied from 0.7 to 92.3 cm and medium water table from 12.6 to 126.3 cm. A continuous rise in water table occurred from week 26 to week 32, between weeks 32 to 38 it was around 30 cm and thereafter a continuous decrease occurred. The puddling index was 80.4% for shallow and 80.6% for medium water-table soil. Under puddling conditions, bulk density increased by 16.9% under shallow- and 14% under medium-water table conditions. This increase in bulk density enhanced microporosity by 11.6% for shallow water table and 5.1% for medium water table soils, but reduced macroporosity, hydraulic conductivity and infiltration rates respectively by 51.1, 50.7, and 54.1% of shallow water table and 53.6, 54.7 and 51.3% of medium water table soils. Microporosity decreased by 13.5% and total porosity by 8% with increasing crop growth. The reductions were more pronounced under the rainfed as compared with the continuous submergence regime. Soil moisture tension remained zero under Ic but varied from zero to 15 bar under Io. In Ic 1 and Ic 3 conditions it ranged from zero to 0.05 bar and under Ic 5 and Ic 7 from 1.7 to 3.5 bar during the entire crop growing season. For Ic, grain yield was about 6300 kg ha −1, under Ic 1, Ic 3 and Ic 5 regimes 5800 kg ha −1, and under Ic 7 and Io, 5000 kg ha −1. In shallow water table grain yield was 200 to 300 kg ha − higher than medium water table in all the water regimes tested. Thus, it is apparent that in terms of net return, continuous submergence did not appear necessary under Tarai conditions, where water table remains shallow (< 30 cm) for most of the rice growing season. Intermittent irrigation, given at 3 to 5 days after water vanished from the surface of the soil under shallow and 1 to 3 days under medium water table conditions, appears to be as effective as continuous submergence.

SOIL MOISTURE TENSION-BASED IRRIGATION OF CONTAINER-GROWN PLANTS UNDER COMMERCIAL CONDITIONS.

An irrigation system was developed to water container-grown ornamental plants so that soil moisture tensions could be continuously monitored and controlled. Operation of such a system has been shown to significantly reduce the amount of water which must be applied to produce high-quality potted chrysanthemums. This presentation will focus on modification of drip irrigation systems in commercial production environments to irrigate based on soil moisture tension. High-quality plants were produced in commercial trials with such systems. In all cases significant economic savings due to reduced fertilizer and water application were observed. Furthermore, the amounts of irrigation water run-off were significantly lower than in systems where irrigation was controlled manually or with timers.

USE OF FIELD-LOCATED DRAINAGE LYSIMETERS FOR THE DETERMINATION OF STRAWBERRY WATER REQUIREMENTS

Sixteen field-located drainage lysimeters (each 60 cm wide, 2.44 m long, 60 cm deep) designed specifically for determination of water requirements for fruiting strawberry production (season - Oct to April) were installed in 1986. Each lysimeter was equipped with individual micro-irrigation and drainage collection systems automated for minimal management input. Initially, computer control (using a low-cost microcomputer) was used to continuously check switching-tensiometers located in each lysimeter and apply irrigation water as needed, A drainage suction (-10 MPa) was applied continuously to simulate field drainage conditions. Manually-installed lysimeter covers were used to protect the plots from interference from rainfall when needed, Initial irrigation application treatments were set at four levels of soil moisture tension controlled by tensiometers and were measured using flow meters for each lysimeter. This paper will discuss problems that were experienced with the initial setup (difficulty in measuring actual application amounts, tensiometer and computer control, elimination of rainfall interference, uniformity of irrigation application, and salinity in the rooting zone) and the modifications (pressurized reservoir tanks, construction of motorized rain-out shelter, micro-irrigation emitters used, and fertilization program) which have been made to overcome them,

The variability of nitrifying activity in field soils

The effect of pH on the activity of nitrifying organisms was examined in pasture soils ranging in pH from 4.9 to 7.3, using a short-term nitrification assay (SNA). The optimum pH for nitrifier activity (pHopt) was generally close to the soil pH, suggesting that the indigenous nitrifier populations adjusted to the prevailing soil pH. A consequence was that the SNA at the soil pH (SNApH) bore a near 1:1 relationship with the SNA at the pHopt (SNAopt) over a wide range of SNA values. The effect of soil moisture tension on the SNA was less pronounced than that of pH, but an optimum occurred around pF 3.4.

Growth analysis of responses by planted white pine and white spruce to changes in soil temperature, fertility, and brush competition

A factorial field experiment, located near Chalk River, Ontario, Canada, was used to test the effects of brush competition, fertility, and soil temperature on first and second-season growth of planted white pine and white spruce. Soil temperature, soil moisture tension, and photosynthetically active radiation were continuously monitored to quantify treatment effects. Foliar nutrition was assessed on nursery stock pre-planting and on current and previous foliage age classes after one growing-season. Measurement of biomass components and leaf surface area was carried out after one growing-season. Increasing soil temperature improved the net photosynthetic rate ( P n) of both species in the first growing-season. Relative growth rate ( G r) of both species was positively affected by the soil temperature treatments but, because of changes in carbon partitioning and foliage morphology, was not directly related to P n. Fertilization and brush control treatments caused compensating adjustments in morphology and biomass allocation that did not affect G r in the first season. In the second season, environmental conditions changed and brush competition increasingly influenced growth. Despite the changes in environmental conditions during the plantation establishment period, the ability of trees to successfully adjust to environmental stress increased from the first growing-season to the second.

モモ果実のポリフェノール含量に及ぼす土壌の乾燥ならびに気温の影響

The weight of harvested fruits, and the contents of total soluble solids and phenolic compounds were determined in four peach cultivars (Prunus persica BATSCH) planted in plastic containers grown under different conditions of soil moisture and air temperature.Using the peach trees, cv.‘Takei Hakuho’grafted on P. persica, and cv.‘Sanyo Suimitsu’grafted on P. persica or P. tomentosa THUNB., soil moisture tension (pF) was maintained for each stage of fruit growth such as an early period (Stage 1), a stone-hardening period (Stage 2), and a maturation period (Stage 3) at 2.3 to 2.7 by withdrawing water. Whereas in the control pF was maintained at 1.0 to 1.5 throughout experiments. Later time of the drought treatments resulted in later maturation of fruits in either cultivar. In both‘Takei Hakuho, ’and‘Sanyo Suimitsu’grafted on P. tomentosa, the smallest fruit and the highest content of phenolic compound in the fruit were observed in the drought plot during the Stage 3. In ‘anyo Suimitsu’grafted on P. persica, the content of phenolic compound was high not only in the drought plot during the Stage 3, but also in the control one.When peach trees, cv.‘Saotome’and‘Chikuma’grafted on P. persica were grown under four different air temperatures throughout Stages 2 and 3, the content of phenolic compound in the fruit was higher in the plots of 15°C and 20°C than in those of 30°C and the control, in which plants were grown outdoors throughout experiments. In‘Sanyo Suimitsu’ peach trees on P. persica grown at 20°C and 30°C of air temperatures during Stages 2 or 3, the content of phenolic compound was higher at 20°C than at 30°C in either stage, and it was also higher in the treatments of Stage 3 than in those of Stage 2 for both temperatures. Regardless of cultivar, at any plot treated with constant air temperatures of 15°C, 20°C, and 30°C, fruit weight was small, compared to the control. Average air temperature outdoors was 22.8°C or higher throughout the treatments.From these results, it is considered that soil drought and low air temperature during the Stage 3 of fruit growth is closely related to the occurrence of astringency in peach fruits.

Yield and Yield Component Response of Eight Potato Genotypes to Water Stress

The differential tolerance to moisture stress among potato (Solanum tuberosum L.) genotypes may be associated with differences in sensitivity during the ontogeny of yield development. This study was undertaken to determine the effect of a wide range of moisture stresses on the yield and components of yield of eight genotypes (‘Acadia Russet’, ‘Bintje’, ‘Jemseg’, ‘Kennebec’, ‘Raritan’, ‘Russet Burbank’, ‘Sable’, and ’Shepody’). The genotypes were subjected to three levels of soil moisture tension in 1983 (−30, −60, and −90 kPa) and four in 1984 (−30, −60, −90, and −120 kPa) at Vauxhall, Alberta on a Cavendish sandy loam (Brown Chernozemic) (fine‐loamy, mixed, frigid Ultic Haploxeralf). A mathematical model based on the method of path analysis was used to study the relationship between the components of yield and the overall response of the final tuber yield to moisture stress. Moisture stress treatments caused marked (P &lt; 0.01) reductions in marketable yield, tuber number per stem and average tuber weight. Mainstem number was not affected. The genotypes ✕ stress interaction was significant (P &lt; 0.05) in an analysis of variation (ANOVA) carried out over 2 yr. While analysis of the yield data using the model demonstrated that in general genotypes are very sensitive to moisture stress at both tuber initiation and at the tuber sizing growth stages, the greatest variability amongst genotypes in response to stress occurred at tuber sizing. Shepody, Russet Burbank, and Sable showed a strong sensitivity to stress in the tuber initiation phase while Jemseg, Acadia Russet, and Kennebec were more sensitive at tuber sizing. The study demonstrates differences in the structure of the response of the genotypes to moisture stress, measured in terms of the components of tuber yield, and indicates the importance of this information to ensure efficient moisture management.

Reaction of Peanut Genotypes under Drought Stress to Aspergillus flavus and A. parasiticus1

Abstract Seven peanut genotypes (Arachis hypogaea L.) were tested in greenhouse and microplot experiments during two consecutive years to determine peanut peg colonization by Aspergillus flavus and to determine the effect of two drought stress treatments on the susceptibility of peanut shells and kernels to Aspergillus colonization and aflatoxin contamination. Moisture tensions within the soil and temperatures of the soil and air were monitored during these experiments. Colonization of peanut pegs was inconsistent among genotypes and between years. In general, low soil moisture tension enhanced colonization of peanut shells and kernels. Shells of most genotypes were highly colonized after harvest from each moisture regime. Kernels of all genotypes were more susceptible to A. flavus and A. parasiticus colonization under both long and short drought stress conditions compared to non-stressed conditions. However, no significant differences were obtained in the degree of Aspergillus infestation of kernels from PI 337409, Starr, and J-11 in the greenhouse experiments. Under microplot conditions, acomparison of several genotypes revealed that kernels from plants of genotypes TX811956 and TX798736 (short stress treatments) contained significantly lower Aspergillus infestation and kernels from the genotypes PI 337409 and TX811956 and TX798736 contained significantly less aflatoxin.

Growth of Chrysanthemum Using an Irrigation System Controlled by Soil Moisture Tension

Abstract Chrysanthemum × morifolium Ramat. cv. Polaris plants were grown in containers using an irrigation system based either on time (5 min/day) or on soil moisture tensions of −1.5, −3.5, −7.5, and −15 kPa. Soil moisture tensions of −7.5 or −15 kPa caused significant reductions over the time-based treatment in fresh and dry weights of leaves, stems, and inflorescences and total leaf area, but had no influence on inflorescence diameter or cropping time. Stem length was reduced in those plants exposed to the two higher tensions; however, the resulting cut flowers were still long enough to satisfy commercial demands. The amount of water applied in tension-based treatments was 8% to 24% that applied in the time-based treatment. The −1.5- and −3.5-kPa treatments were best suited for minimizing water use while maintaining high crop productivity.