Low Soil Moisture Levels Research Articles

Enterovirus inactivation in soil.

The inactivation of radioactively labeled poliovirus type 1 and coxsackievirus B 1 in soils saturated with surface water, groundwater, and septic tank liquor was directly proportional to temperature. Virus persistence was also related to soil type and the liquid amendment in which viruses were suspended. At 37 degrees C, no infectivity was recovered from saturated soil after 12 days; at 4 degrees C, viruses persisted for at least 180 days. No infectivity was recovered from dried soil regardless of temperature, soil type, or liquid amendment. Additional experiments showed that evaporation of soil water was largely responsible for the decreased recovery of infectivity from drying soil. Increased rates of virus inactivation at low soil moisture levels were also demonstrated.

Moisture Conservation Potential with Conservation Tillage Treatments in the Thick Loess Area of Western Iowa1

AbstractMoisture is usually in short supply for production of corn (Zea mays L.) on thick loess derived soils in western Iowa. Practices that conserve moisture should increase crop yields but quantitative data is very scarse. The objectives were to develop a yield response curve for moisture applicable in western Iowa and evaluate the potential effect of conservation tillage systems on corn yields. Computerized modeling techniques were used to develop the yield response curve and to evaluate conservation practices.Moisture stress indices, which were highly correlated with measured corn yields, were used to evaluate the effectiveness of modeled tillage treatments in terms of corn yield. The model budgeted daily soil moisture use based on initial soil moisture measurements, actual weather data, and simulated hydrologic processes. The appropriate hydrologic processes were modified to approximate the tillage system under study. The hydrologic processes assumed most altered by conservation tillage management were surface runoff and surface evaporation in the spring fallow period.The modeled tillage practices were evaluated at three assumed spring soil moisture levels in combination with actual long term weather records. When spring soil moisture levels were at 100% of the plant‐available water capacity (PAWC), tillage practices had little effect on estimated corn yields. At the medium and low spring soil moisture levels, modeled conservation tillage was effective in increasing yield estimates over those obtained with conventional tillage.

The Effect of Moisture Stress on Infection ofTrifolium subterraneumL. byRhizobium trifoliiDang

Moisture stress and method of inoculation greatly affected the number and distribution of infected root hairs and nodules of young seedlings of Trifolium subterraneum. A reduction of soil moisture from 5·5 to 3·5% (−0·36 to −3·6 × 105 Pa) significantly decreased the number of infection threads and completely inhibited nodulation, although the number of rhizobia in the rhizosphere was unaffected. At low soil moisture levels the root hairs were abnormally short and swollen. Infection and nodulation were little affected between 5·5 and 9·5% moisture (−0·36 to −0·089 × 105 Pa). Distribution of infected root hairs depended on the initial placement of the inoculum; with the inoculum mixed evenly through the soil, infection threads occurred at discrete foci along the root. With seedlings inoculated at planting, infection threads were restricted to the top 1–2 cm of root, even at the highest soil moisture tested. Watering increased the number of infections in plants grown at 3·5% moisture; nodules were formed at a rate equivalent to non-stressed plants. Watering also enabled movement of the seedling-borne inocula; new infections were formed along the root surface bearing mature root hairs.

The effect of certain pre-sowing seed treatments and early phosphorus supplement on cell sap concentration and water fractions in leaves of maize (Zea mays L.) plants grown under soil moisture stress conditions

The exposure of maize plants to drought led in most cases to a decrease in both the total and free water percentages, but to an increase in cell sap concentration, bound water percentage and bound water/free water ratio, comparing with the case of normal water supply. The employment of any of the studied treatments at either the normal or low soil moisture levels led throughout the period of time preceding the milky stage to a decrease in the free water percentage in maize leaves, but to the reverse effect with respect to both the bound water percentage and the bound water/free water ratio. The determinations of water fractions in leaves (free, bound water % and the ratio between them) before or at the tasseling stage appeared to be more reliable, compared with osmotic pressure determinations, as indication for the effective use of a given treatment in increasing the drought resistance of maize plants.

Effects of air temperature, soil temperature and soil moisture on growth and development of tomato itself and grafted on its own and egg-plant rootstock

The problem was studied whether tomatoes, grown in a hot and arid climate, benefit from grafting on egg-plant, which is highly efficient in water uptake. Growth and development of tomato ( T), tomato grafted on its own rootstock ( T T ) and tomato grafted on egg-plant rootstock ( T E ) were compared at air temperatures of 28°C during the day and 18°C during the night ( 28 18 ) and at 28°C constantly ( 28 28 ), at soil temperatures of 14, 21 and 28°C with the following soil moisture regimes: wet ( W 1), medium ( W 2) and dry ( W 3). At 28 18 and 28 28 water consumption was about equal, but the transpiration ratio at 28 28 was twice as high as that at 28 18 . The latter conditions gave a much stronger plant with more fruits. At a soil temperature of 14°C water use was strongly reduced. The transpiration ratio increased with the soil temperature. Differences in plant type were small. At the highest soil temperature of 28°C fruit growth was strongly reduced. At lower soil moisture levels less water was used and the transpiration was lower. Plant type was correlated herewith. Vegetative growth of T T was weaker than of T, but generative growth was stimulated. The strong E rootstock stimulated vegetative growth at high air and soil temperature, but fruit growth was very poor under these conditions; at a low soil temperature of 14°C vegetative growth was also reduced. The hope that the E rootstock would be beneficial for fruit growth at high temperatures was not fulfilled. An additional experiment in a growth-room at 23°C showed that under conditions of moisture stress there was no difference in water potential between leaves of T T and T E .

THE BIOLOGY OF POLLENIA RUDIS, THE CLUSTER FLY (DIPTERA: CALLIPHORIDAE): III. THE EFFECT OF SOIL CONDITIONS ON THE HOST–PARASITE RELATIONSHIP

AbstractThe course of the host–parasite relationship between Pollenia rudis (Fabr.) and Eisenia rosea (Sav.) is determined largely by the behaviour of the earthworm host, which in turn depends on soil conditions. Encystment of the host, which occurs mainly at low levels of soil moisture and bulk density, increases the success rate of the infection. Autotomy of infected segments by the host occurs in a higher percentage of active than encysted worms.

Yield Response of Soybean Varieties Grown at Two Soil Moisture Stress Levels1

AbstractEight soybean [Glycine max (L.) Merrill] varieties in each of four maturity groups were grown to maturity at optimum and deficient soil moisture conditions to determine differences in varietal response to soil stress. A significant variety by stress level interaction on seed yield was detected among varieties in each of four maturity groups, indicating that the effect of soil moisture stress on yield varied among varieties.Under high moisture stress conditions, the yield of the most stress resistant varieties was reduced about 20%, while the yield of the least stress‐resistant varieties was reduced about 40%. The absolute reduction in yield for the most stress‐sensitive varieties was approximately 1000 kg/ha, while the yield of the least stress‐sensitive varieties was reduced about 200 to 400 kg/ha.Under conditions of optimum soil moisture, the difference in yield among varieties was large relative to the difference in yield produced under deficient moisture conditions. A low or nonstress soil moisture level permits greater genotypic expression, thereby increasing genotypic variance among varieties. A low soil moisture stress environment appears to be the optimum environment for selecting soybean yield attributes.

Effects of North‐ and South‐facing Slopes on Yield of Kentucky Bluegrass (Poa pratensis L.) with Variable Rate and Time of Nitrogen Application1

AbstractPlant responses to differences in slope orientation have been observed for many years, but attempts to identify and measure specific responses and microclimatic factors are limited. Field studies were conducted near Morgantown, W.Va, during the 1966 to 1969 growing seasons to determine the effect of slope orientation on the yield of Kentucky bluegrass (Poa pratensis L.) treated with 0, 112, 224, 448, and 672 kg/ha rates of N applied singly and in up to four split applications. Slopes were approximately 35%. Soil on both slopes was Gilpin silt loam. The rate of growth, total yield, seasonal distribution of yield, and N recovery in plants were influenced greatly by slope orientation. Production on the north facing slope was more than twice that on the south‐facing slope. Splitting the N applications tended to produce a higher yield and more uniform seasonal distribution. More than 11,000 kg/ha of bluegrass forage were produced on the north‐facing slope in 1967 as compared to 4,000 kg/ha on the south‐facing slope. A combination of high soil temperatures and low soil moisture levels appeared to limit growth on the south‐facing slope. Maximum soil temperature on the north‐facing slopes were from 8 to 10 C less than on the south‐facing slope. Temperatures were measured 2.5 cm (1 in) below the soil surface under the bluegrass sod. Yield differences due to slope orientation completely overshadowed any yield responses from specific fertility treatments.

Influence of Soil Class and Soil Moisture on Bioactivity of Carbofuran and Disulfoton in Corn in Greenhouse Tests: Relationship to Leafhopper Vector Control and Corn Stunt Disease Incidence12

Carbofuran and disulfoton applied to com at 1 Ib/acre in-furrow at planting killed 100% of the test leafhoppers, Dalbulus maidis (DeLong & Wolcott), confined for 24 hours on plants treated with insecticide up to day 27 after planting in sandy loam, silt loam, and silty clay soils at low, medium. and high levels of soil-moisture. The insecticides showed gradual reduction in performance after day 27 to day 62 when the test was concluded. Both insecticides performed best at the highest soil-moisture level and were less effective at the lower soil-moisture levels. Bioactivity of the toxicants was greater in corn planted in lighter soil than in the heavier soils, i.e., insect mortalities on insecticide-treated plants in the 3 soil classes were: sandy loam > silt loam > silty clay. Correspondingly, corn stunt disease incidence was correlated to the level of insect control.

Effects of Temperature and Soil Moisture on Single vs. Split Nitrogen Applications to Rye (Secale cereale L.) Forage1

AbstractNitrogen was applied in single and split applications at rates of 0, 300, and 600 mg per pot (equivalent to 0, 50, and 100 pp2m) to rye grown in a growth chamber at 10 and 21 C. Low and high soil moisture levels were maintained by watering to field capacity when soil moisture reached 15 and 60% of field capacity. Responses to these variables were measured by forage yields, total N uptake, and percent N in the plants.With either low temperature or low soil moisture, higher forage yields were obtained with single N applications. Only under both high temperature and high soil moisture was it advantageous to split N. With high soil moisture, split N improved yields in the second harvest. This would, in effect, extend the grazing period. Soil moisture was more limiting to growth in the first harvest, while temperature was more limiting in the second harvest.When N was applied in a single application, plant uptake (mg N per pot) was usually greater than or equal to treatments with split applications.Plant N content at 21 C was higher with single N applications but at 10 C was higher with split applications. Generally, low soil moisture increased N content of the forage compared with high soil moisture.The variable responses to N obtained under different temperatures and soil moisture levels will aid in interpreting field results.

THE FATE OF N‐(4‐CHLOROPHENOXY)‐PHENYL‐NN‐DIMETHYLUREA (C‐1983) IN SOILS AND PLANTS*

Summary. The adsorption of N'‐(4‐chlorophenoxy)‐phcnyl‐NN‐dimethylurea (C‐1983) and N‐butyl‐N‐(3,4‐dichlorophenyl)‐ N‐methylurea (ref. comp.) by different soils was investigated with a slurry‐type procedure. Freundlich isothermal equilibrium plots demonstrate that both herbicides, but especially C‐1983, were quite strongly adsorbed, on soil particles. The following concentrations of C‐1983 adsorbed were found to be in equilibrium with 1 ppm soil solutions: 14 γ/g (sandy loam), 40 γ/g (clay loam) and 110 γ/g (humus soil) The corresponding values for the ref. comp. were 6.3, 21 and 60 γ/g. Adsorption of C‐1983 was strong on bentonite (400 γ/g) and less pronounced on cellulose (48 γ/g). Soil pH had no significant effect on adsorption. Desorption equilibrium plots indicate that about 50% of C‐1983 adsorbed was released into solution according to adsorption equilibrium conditions. The remaining 50% came off at a much lower rate.Leaching of C‐1983 and the ref. comp. was studied with soil columns to which 200 mm of simulated rain was applied during a period of 45 hours. At a low soil moisture level (wilting capacity), the bulk of C‐1983 was not removed from the top 1 cm section of all three soils. Leaching was somewhat more pronounced in sandy loam (80% recovery in top 1 cm layer) than in clay loam (90%) or in humus soil (95%). Only traces of C‐1983 were recovered from depths below 10 cm and in water percolating from the columns. The ref. comp. leached more easily than C‐1983, especially in sandy loam (bulk of herbicide below 5 cm level). Leaching of both herbicides, but especially of the ref. comp., was less pronounced at the higher soil moisture level (field capacity wet) than at the lower one (wilting capacity).It is suggested that leaching is not a major factor in removing C‐1983 from the surface soil layers. On the other hand, its very strong adsorption seems to be a decisive factor in controlling its availability insoil solution and thus determining both the initial toxicity and and the residual activity in some types of soils. The practical implications for field use are discussed. Le comportement de la N'‐(4‐chllorophénoxy)‐phényl‐NN‐diméthylurée (C‐1983) dans les terres et dans les plantes 1. Adsorption et lessivage dans divers types de terres

Emergence of Phorate-Treated Cotton Seed as Affected by Substrate Moisture and Temperature

Deltapine-15 cotton seed with and without prorate were planted in washed river sand at two moisture levels and four temperatures. Regardless of treatment, seedling emergence was favored by It moisture level of 50% of field capacity as compared with one of 75%. The final stand counts at 86° and 77° F, were comparable for the prorate-treated and untreated seed. Prorate, however, caused a marked reduction in the rate and total emergence at both 72° and 67°. A similar experiment with another lot of seed of the same variety showed that seedling emergence with and without prorate seed treatment were comparable at 80° and 67°. It was concluded that reduction in emergence in prorate-treated seed often found may be due to inferior quality of seed as well as to low temperatures and high levels of soil moisture.

THE GROWTH, NICOTINE AND PHOSPHORUS CONTENT OF TOBACCO GROWN AT DIFFERENT SOIL TEMPERATURE, MOISTURE AND PHOSPHORUS LEVELS

Growth, nicotine and phosphorus content of tobacco, as influenced by soil temperature, soil moisture and soil phosphorus levels, were investigated by growing the flue-cured variety Hicks in a combination of three soil temperature, four soil moisture, and three soil phosphorus treatments.Soil temperature of 22 °C. and soil moisture of 75 per cent of available moisture appeared to be the best for the over-all growth of tobacco. The over-all growth was a little lower at the 30 °C. soil temperature than at the 22 °C. temperature while at the 14 °C temperature it was very poor. Nicotine and phosphorus content in leaf tissue decreased with decreasing soil temperature. A decrease in soil moisture decreased the growth but increased the nicotine content of tobacco. Phosphorus content was influenced little by soil moisture treatments. Low soil moisture treatments were more detrimental to growth of tobacco at the low soil temperature than at the higher ones. Phosphorus produced growth responses at the low soil temperature only. Nicotine content was not influenced by soil phosphorus treatments. Phosphorus applications increased the leaf phosphorus content. At the 14 °C. soil temperature there was an increase in leaf and stalk weight and leaf area with added phosphorus while at the 22° and 30 °C. increases with soil temperature were very small. Stalk weights increased with increasing phosphorus applications at the higher but not at the lower soil moisture levels. The growth was decreased more at the soil temperature of 14 °C. and soil moisture treatments of 25, and near 0 per cent of available moisture than at the soil temperature of 22° and 30 °C. At the low soil moisture phosphorus applications decreased root growth while at the higher soil moisture treatments this phosphorus effect was reversed.

SEEDLING BLIGHT, A FUSARIAL DISEASE OF ASPARAGUS

Incidence of seedling blight in Ontario can be correlated with proximity of mature plantations or with the presence of debris from a previous asparagus crop. As the disease was detected on seedlings grown in soil from "volunteer" plants growing in isolated habitats, the pathogen is considered to be indigenous. The pathogen penetrates directly into the embryonic region of the root tip, or through stomata on the hypocotyl, and colonizes the host both intercellularly and intracellularly. Its limitation to the cortex is regarded as unusual among the parasitic fusaria, which are mainly vascular. The fungus was identified as Fusarium oxysporum sensu Snyder & Hansen var. redolens (Wr.) Gordon. In comparison with F. moniliforme Sheldon, found to cause a root tip necrosis of asparagus seedlings, the cortical Fusarium produced less growth on basal medium plus cellulose but more growth on sucrose, and showed a greater ability to hydrolyze starch. Differing nutrient preferences are suggested as one explanation for the localized types of colonization exhibited by these two fusaria. The optimum soil temperature for disease incidence was established at 25°-30 °C. The effect of temperatures above 30 °C. is considered to be twofold: (1) inhibiting growth of the pathogen and (2) permitting the host to escape by inducing its more rapid emergence. Below 20 °C, the pre-emergence phase of the disease is favored by a retardation of the rate of emergence. Both low and high levels of soil moisture retard emergence and favor pre-emergence blight. Under greenhouse conditions, incidence of the disease usually increased more rapidly when leguminous rather than nonleguminous residues were present in the soil and there was some evidence that the saprophytic growth of the pathogen was more profuse on certain nonliving substrates.

Influence of High, Medium, and Low Soil Moisture on Growth and Alkaloid Content of Cinchona ledgeriana

Soil moisture in Cinchona growing regions may fluctuate greatly with seasonal changes in rainfall; prolonged droughts are experienced almost annually. On the other hand, during the peak of the rainy season the same soils may remain at or near saturation for extended periods. For example, at the Toro Negro National Forest in Puerto Rico, where Cinchona is being grown experimentally, the 23-year-average rainfall for two-week periods from January 1 to March 25 was 2.04 inches with frequent periods of drought. In the current year only 0.21 inch fell during January. From August 13 to November 18 rainfall averaged 5.69 inches for two-week periods. The average total annual rainfall for 23 years was 96.37 inches (4). The above extremes in soil moisture may be expected to exert marked influence on the growth and composition of Cinchona. Heinicke, Boynton and Reuther (3) demonstrated that a flooded (poorly aerated) soil produced symptoms in the apple typical of boron deficiency when the soil was not deficient in that element. It was also indicated that lack of oxygen in the soil interfered with the absorption of nitrogen and potassium. Wager (?) showed that avocado plants were more susceptible to disease if grown in a flooded soil than if watered normally. During the first year from seed, Cinchona plants are primarily herbaceous. It is during this tender stage that soil moisture is most likely to be a critical factor affecting growth. Since the plants are grown in palm-leafcovered nurseries during this stage it is fairly easy to correct a deficiency of soil water by irrigation, but more difficult to prevent an excess during the rainy season. Cinchona nursery plantings have been observed which were apparently healthy during three-fourths ?f the year, but with the advent of heavy daily rains during the peak of the rainy season the plants developed symptoms typical of nutrient deficiencies and many succumbed to fungus attack. The experiment reported here was designed to study the effect of low, medium, and high levels of soil moisture on growth and alkaloid content of young Cinchona ledgeriana seedlings under controlled conditions.