Percent Soil Moisture Research Articles

Effects of Soil Moisture, Texture, and Rate of Soil Drying on Egg and Larval Survival of the Southern Corn Rootworm (Coleoptera: Chrysomelidae)

Greenhouse studies were conducted to determine the effects of four soil textures and four soil drying periods on southern corn rootworm, Diabrotica undecimpunctata howardi Barber, egg and larval survival and maturation. Soil drying intervals had the most detrimental effect on survival. After 4 d of soil drying (no water added to pots), only 20% of larvae survived to pupation. Low clay or organic matter and low levels of soil moisture were not conducive to survival of southern corn rootworm. The interaction of soil texture and soil drying indicates that at 4 d of soil drying, larval survival decreased (70%) in all soils, except dark-textured soils (35% decrease) compared with 2 d of soil drying. Low levels of soil moisture slowed developmental time of larvae. Eggs and first instars were the stages most negatively affected by moisture stress and different soil textures. However, in quartz-sand, the more mobile stages had low survival, probably because of cuticle abrasion from soil particles. The results of these experiments demonstrate the importance of considering the effects of rapidly drying soil on survival of southern corn rootworm and not simply the percentage of soil moisture at any one time.

ニンジンの出芽に対する数種の播種前種子処理の効果

Seedling emergence of carrot was compared among four presowing seed treatments imbibition, priming, pregermination, and pregermination following priming. Five experiments in pots were carried out in plastic houses in seasons at lower and higher temperatures. The effects of seed treatments were evaluated under different daytime temperatures or under different soil moisture conditions.Percentage seedling emergence in the seasons at lower temperatures was improved with all tested seed treatments when daytime temperature was lower or soil moisture percentage decreased rapidly. Treatments of priming and/or pregermination following priming gave good results in percentage emergence. In the season at higher temperature, percentage emergence was improved similarly with treatments of priming, pregermination, and pregermination following priming.The start of emergence was advanced more with priming than with imbibition in both seasons, and more with pregermination following priming than with pregermination under the lower soil moisture conditions in a season at lower temperature. These effects of priming treatment suggested that growth of radicles and/or plumules was promoted during germination and emergence.Mean emergence time was shortened in all treatments, most remarkably with pregermination following priming, considerably with priming or pregermination, and to some degree with imbibition. Spread of emergence times was not reduced consistently with any presowing seed treatment.The results indicated that a most effective presowing seed treatment for improving seedling emergence of carrot was pregermination following priming, or priming only, in the seasons at lower or higher temperatures, respectively.

CALIBRATING RESISTANCE-TYPE SOIL MOISTURE UNITS IN A HIGH-CLAY-CONTENT SOIL

A calibration equation describing the relationship between electrical resistance and gravimetric soil moisture was generated for resistance-type soil-moisture-sensing units to be used in a high-clay-content soil. Soil moisture percentages measured gravimetrically and percentages predicted by entering resistance values from a validation set of moisture-sensing units into the equation did not differ. Subsequent analyses indicated that with a calibration set of five soil moisture units, a reliable equation could be generated with data from as few as three wetting-drying cycles in a high-clay-content soil.

Effects of root nodules and taproots on survival and abundance of Sitona hispidulus (Coleoptera: Curculionidae) on Medicago sativa

ABSTRACT. The effects of food resources on populations of larvae of Sitona hispidulus (F.), a root and nodule herbivore of Medicago sativa L., were investigated in 1983 and 1984. Density‐dependent mortality among first‐instar larvae indicated that a lack of available root nodules, the primary resource for first instars, contributed to the 66.2±5.2% and 80.7±4.1% mortalities of first‐instar larvae in 1983 and 1984, respectively. Initial densities of larvae entering the soil were 31.7±2.4 and 15.6±1.3 per soil sample (10.5 cm diam. ×15 cm deep) in 1983 and 1984, respectively (±SEM). Survivorship and number of first‐instar larvae per soil core sample were significantly related to number and biomass of nodules per soil sample. Percentage soil moisture was not consistently correlated with survivorship and number of larvae per soil sample. Numbers of second‐ and third‐instar larvae were not consistently correlated with either nodule or taproot biomass. Numbers of fourth‐instar larvae were associated with taproot biomass, suggesting that taproot surface area may also limit population levels of S.hispidulus. No correlations were found between taproot and nodule biomass on any sampling date indicating that high numbers of fourth‐instar larvae associated with larger taproots were not merely due to a greater survival of first instars associated with larger taproots. The study suggests that population levels of nodule‐herbivores are controlled by the availability of root nodules. A sparse distribution of nodules results in high levels of mortality among nodule‐herbivores of Medicago sativa.

Effects of laboratory germination, soil temperature and moisture content on the emergence of spring wheat

SummaryIn field investigations in a sandy-loam soil, probit percentage seedling emergence of commercial and aged seed lots of spring wheat (Triticum aestivum L., cv. Timmo) was a positive linear function of probit percentage laboratory germination and mean soil temperature and a negative linear function of percentage soil moisture content over the ranges 12·1–15·5% moisture content and 7·0–11·0 °C. In a laboratory investigation using the same soil a similar form of relationship was observed in six lots over a range of constant soil moisture contents between 10 and 18% and at constant soil temperatures of 8 and 20 °C. In all cases there was no interaction between any of these determinants of seedling emergence.Linear relationships between the mean rate of seedling emergence in the field (i.e. reciprocal of mean emergence time) and probit percentage laboratory germination and mean soil temperature were shown, but there was no obvious effect of mean scil moisture content between 12·1 and 15·5% on rate of field emergence. Seed lots of different percentage laboratory germination had the same base tsmperature for emergence (1·9 °C): differences between seed lots in mean emergence rate were due to different thermal time (day-degree) requirements for emergence; the thermal times required were a function of probit percentage germination in a standard laboratory test. The implications of these results in providing better advice on sowing rates are discussed.

Environmental factors affecting seed germination of gray birch (Betula populifolia) collected from abandoned anthracite coal mine spoils in northeast Pennsylvania

SUMMARYGermination of gray birch (Betula populifolia) seed collected from anthracite mine spoils in northeastern Pennsylvania was studied. Environmental conditions of the spoil banks are such that high mortality may occur at seed and germination stages because of low moisture availability and thermal stress. The mine spoil banks are harsh environments with respect to key seed germination factors: percent soil moisture as low as 1.8% and soil surface temperatures reaching 59°C. In the field, gray birch typically germinated in mid‐April prior to severe environmental stress. Trends in germination success were inversely related to rising soil temperature and decreasing soil moisture availability. Although seeds were capable of survival and germination under laboratory conditions of constant temperatures in excess of 55°C, dramatic decline in germination was observed under fluctuating temperature regimes likely to be experienced in the field. No germinations occurred under fluctuating temperatures in excess of 30°C. Germinations in the field were seen to end after mid‐June when substrate temperatures exceeded 30°C.

Herbicides and planting date affect early performance of container-grown and bare-root loblolly pine seedlings in Alabama

The survival of bare-root and container-grown loblolly pine (Pinus taeda L.) seedlings exceeded 90% when outplanted in March at two sites in Lee County, Alabama. At both sites, soil moisture and seedling survival were greater in March than in May. A March herbicide application reduced weed biomass by 75–80% at both sites. At the moist site, herbicide application did not affect survival. However, at the drier site, a reduction in weed biomass increased both the percent soil moisture and the survival of May-planted bare-root seedlings. When soil moisture at planting time was less than 13% on a dry weight basis container-grown seedlings survived better than bare-root seedlings. At both sites, reduced weed competition resulted in greater seedling heights and diameters.

Regional‐Scale Estimates of Surface Moisture Availability from GOES Infrared Satellite Measurements1

AbstractA method for obtaining remotely a measure of surface moisture, called moisture availability, is derived here using satellite infrared surface temperature measurements in conjunction with a numerical boundary layer model. Results are presented largely in the form of a statistical comparison between rainfall (antecedent precipitation index) and soil moisture patterns. Moisture availability patterns were determined from Geostationary Operational Environmental Satellite (GOES) thermal infrared temperature measurements for 12 days during the dry summers of 1978 and 1980 over eastern Kansas and southeastern Nebraska. Representative analyses of moisture availability are presented, along with a summary of results for all cases. A significant correlation was found between M and the antecedent precipitation (API) for virtually all 12 days analyzed. The relationship between M and API can be expressed as a log‐linear one: API (cm) = 0.32 (2a, where n = a + bM and a ∼ 0.9 and b ∼ 2.2. Agreement between M and API was poorest on the smallest scales, for reasons which are discussed in the text. The relatively narrow range of API values over which M is sensitive to changes in rainfall suggest that the infrared method is most suitable for deriving surface moisture availability over plains or semiarid vegetation and where there are large horizontal precipitation gradients. The accuracy of the method may permit inference of percent soil moisture over the rooting depth of plants to within plus or minus 10 to 20%, at least when averaged over a regional‐scale domain.

Temperature and Evapotranspiration Gradients of the White Mountains, New Hampshire, U.S.A.

Air temperatures and soil moisture percentages were measured below forest canopies along an environmental gradient in the White Mountains of New Hampshire, U.S.A. The following gradients of decline with altitude were estimated from these data: within-forest air temperature, growing degree-days (0?C base), and potential and actual evapotranspiration. These gradients provide a basis for the development of predictors for rates of ecologically significant phenomena such as water balance, net primary production, and decomposition rates.

Behaviour of leaf water potentials of wheat and mungbean under field conditions as a function of available soil moisture and relative humidity

AbstractField experiments were conducted with wheat and summer mungbean on an alluvial sandy loam soil (Typic Ustochrept). Data were obtained concurrently on soil moisture, leaf water potentials and relative humidity above crop canopy, in order to establish correlations between plant water status and soil moisture and aerial environment. In case of wheat, leaf water potentials correlated well with available soil moisture percentage remaining in the root zone as well as relative humidity above the crop canopy, only for the reproductive phase of crop growth. For the vegetative phase of crop growth, no relationships could be established, possibly because of high and non‐limiting soil moisture. For mungbean, which is capable of avoiding drought, only 0900 hours leaf water potential correlated with available moisture remaining the root zone. For adapting the regressions for scheduling irrigation, important growth phases have to be considered separately.

Agricultural droughts at Peddapuram, East Godavari district, Andhra Pradesh

This investigation is undertaken to study agricultural drought in relation to ragi (Finger Millet) grown under r1linfed conditions. Regression relationship is worked out between the yields of ragi and seasonal lma for forecasting of crop yield. To know the requirements of index of moisture adequacy and percentage of available soil moisture during crop growing phase, graphs are presented by taking above parameters as crop growing weeks for the years of lowest, 'average and highest yields. For these years weekly water balance patterns are also presented.

Use of pressure bomb in the determination of soil water potential

Pressure bomb apparatus was employed to determine the water potential values of fine sand and a loamy sand soil. Water potential equilibrium was obtained between potted plant (Sunflower,Helianthus annuus L.) and soil by precluding evapo-transpiration and allowing time to overcome potential gradient between the two. At this stage the plant was behaving as a “biological tensiometer” or a “living tensiometer” and a measure of the water potential in leaf by pressure bomb indicated soil water potential in the root zone. Calibration curves were prepared by determining concurrent soil moisture percentages. The results were found consistent with data obtained by thermocouple psychrometers. Besides, the method rendered more accurate estimates of total water potential as compared to pressure membrane apparatus.

Responses of Crested Wheatgrass and Russian Wildrye to Water Stress and Defoliation

Responses of Crested Wheatgrass and Russian Wildrye to Water Stress and Defoliation

Factors affecting the distribution of Scirpus nodosus plants in a dune slake community

A survey was undertaken to show the distribution of Scirpus nodosus plants in a dune slack community on the eastern Cape coast. Plants were recognized as belonging to three separate height classes and the position of the individuals was related to various environmental factors. Although soil pH, conductivity and percentage soil moisture are strongly interrelated it is suggested that soil moisture is the major controlling factor in the establishment of these plants. The effect of wind-borne salt spray may also limit the establishment of dune slack plants on the foredunes as field observations showed that although large amounts of salt spray reach the dunes, the amount deposited in the dune slacks is negligible.

Digestibility of Kleingrass Forage Grown Under Moisture Stress1

Low forage digestibility of warm‐season perennial grasses frequently limits performance of grazing animals. Digestible energy intake is of particular concern during hot, dry periods of mid‐summer. Although relationships between plant characteristics affecting digestibility and temperature, irradiance, and soil fertility have been reported, the relationship between forage digestibility and moisture stress has yet to be clearly determined. The purpose of this study was to determine the influence of moisture limitations on digestibility of kleingrass (Panicum coloratura L.) forage.Kleingrass plants cloned from a single parent were grown in pots under greenhouse conditions at five watering levels. Soil moisture ranged among watering levels from field capacity down to near the permanent wilting point. Four pots or replications for each of five watering levels were arranged in a randomized block design. Plants were harvested on four successive harvest dates after a 15‐day period of regrowth. In vitro digestible organic matter (IVDOM) of leaves and stems, gravimetric soil moisture, plant water status (leaf xylem pressure potential), forage yield, and plant leafiness were determined at each harvest date. Although percent soil moisture and leaf xylem pressure potential declined as a result of successively lower watering levels, yields per pot and IVDOM of both leaves and stems were not significantly reduced until reduced watering lowered soil moisture to 9.1% and leaf pressure potential to −7 bars. Only leaf growth occurred when soil moisture and leaf xylem pressure potential were reduced to 7% and −14 bars, respectively. Leaf and stem IVDOM ranged from 63.8% and 60.8% with non‐stressed material down to 33.6% and 42.8% at the most stressed level producing leaf or stem growth, respectively. The results indicate that low forage digestibility of warm‐season grasses in midsummer may be associated with moisture limitations.

The Influence of Soil Moisture on Macroscopic Sulfur Dioxide Injury to Pinto Bean Foliage

The influence of soil moisture stress on sulfur dioxide (SO/sub 2/) injury to pinto bean foliage was investigated in relation to stomatal conductance rate, soil moisture content, and plant water potential. Pinto bean plants were grown at four soil water potentials (-1/3, -1, -3, and -5 atm) and exposed to 5,720 ..mu..g/m/sup 3/ (2.2 ppm) SO/sub 2/ for 3 hr. Macroscopic injury was severe on plants grown at -1/3 and -1 atm soil water potential and negligible on plants grown at -3 and -5 atm water potential. Injury was highly correlated with percentage of soil moisture, and both injury and soil moisture were highly correlated with stomatal conductance rate and water potential of the plants. The duration of soil moisture stress (1, 2, or 3 days) did not affect the amount of macroscopic injury induced by SO/sub 2/, the stomatal conductance rate, or plant water potential. Stomatal conductance rates of plants grown at -1/3 and -1 atm soil water potential decreased when the plants were exposed to SO/sub 2/, while those of plants grown at -3 and -5 atm soil water potential were not affected by exposure to SO/sub 2/.

Distribution of Crumenulopsis sororia (Karst)

A study was made of the canker pathogen Crumenulopsis sororia in ten stands of Lodgepole pine (2825 trees) at Mearns Forest, Grampian Region, Scotland. The stands sampled were all of Alberta provenance and ranged from 46–50 years old. In heavily infected stands co- and subdominant trees were more extensively cankered than were dominant and suppressed trees, whereas the extent of cankering and resinosis was not related to stem girth-class. Significantly (p = 0.001) greater numbers of cankers occurred on north and east facing sides of tree stems as compared with south and west sides. The use of Weighting Coefficients to integrate severity of infection with stage of disease showed that suppressed trees scored highest disease indices and that there were significant (p = 0.01) differences in disease indices between the dominant, codominant and suppressed classes. Percentage infection of Lodgepole pine by Crumenulopsis sororia was correlated negatively with effective rooting depth (r=−0.66) and positively with percentage soil moisture (r=+0.91). These findings suggest that limited rooting volume and variations in the micro-climatic regime around individual stems may influence critically the success of infection.

PERCOLATE WATER AND BROMIDE MOVEMENT IN THE ROOT ZONE OF EFFLUENT IRRIGATION SITES1

ABSTRACT: A bromide tracer was used to evaluate percolate water and ion movement in the upper 1.2 m of soil at a proposed sewage effluent irrigation site located in the Missouri Ozarks. Two plots representing Doniphan silt loam and Crider silt loam soils were sprinkler irrigated with local ground water at a rate of 7.62 cm/week from June through August 1976. Soil water potential, percent soil moisture by volume, and background levels of bromide in soil water, ground water, and precipitation were measured at the study plots. Bromide exchange properties and saturated hydraulic conductivity of the soils were determined in the laboratory. During two selected time periods, irrigation water, was spiked with NaBr (5.0 mg/l Br). Bromide movement through the upper profile was quantified by soil water samples and post‐sampling neutron activation analysis. Soil moisture was near saturatin in both soils when the Br tracer was applied. Bromide concentrations above background levels (0.023 mg/l Br, Doniphan silt loam and 0.016 mg/l Br, Crider silt loam) were detected within 2.60 hours at 0.9 m in the Doniphan soil and within 3.75 hours at that depth in the Crider soil. The rate of Br movement in the profile was greater in both soils than the measured saturated hydraulic conductivity, Bromide concentrations above background levels were present in soil water from the study plots for a minimum of 21 days after irrigation with the Br tracer.

Legume Cover Crops, Organic Mulch and Associated Soil Conditions, and Plant Nutrient Content for Establishing Quillou Coffee1

Abstract Four cover crops, calopogonium (Calopogonium mucunoides Desv.), centrosema (Centrosema pubescens Benth.), pueraria (Pueraria phaseoloides (Roxb.) Benth.) and cowpea, (Vigna unguiculata Walp) and 2 types of organic mulch, grass and banana/plantain leaves were used in comparison with clean weeding as control in establishing Quillou coffee (Coffea canephora Pierre var canephora Haarer). Shade significantly affected the plant N, P, and K percent nutrient content but nonsignificant on Mg, Ca, and Na. Cover crop and mulch treatment effects were significant only with P and K while interactions between shade and these treatments were nonsignificant for any of the nutrients considered. Percent soil moisture content was influenced by both shade and treatments as well as their interactions in both June and January. Soil pH was significantly affected by both shade and other treatments in January but no significance was recorded in June.

Factors affecting the growth of Pennisetum purpureum in the wet tropics. I. Short-term growth and regrowth

Six plantings of elephant grass (Pennisetum purpureurn) were made at 2-monthly intervals in the wet tropics of north Queensland. Each crop was sampled for yield at monthly intervals. After 6 months' growth each crop was ratooned for a further 6 months' growth, with yield samples again being taken at monthly intervals. As well, stem elongation growth was measured twice weekly, together with various climatic parameters and soil moisture to 90 cm. Regrowths after each monthly harvest were sampled 1 month after cutting. Short-term growth, measured as elongation growth and averaged for the whole experimental period, was found to have a significant parabolic relationship with crop age and available soil moisture percentage, but not with average temperature or evaporation. Regrowth yields were found to be linearly and positively correlated with tiller density prior to ratooning and regrowth tiller density, with average regrowth temperature or regrowth degree days but linearly and negatively correlated with moisture regime, whether expressed as average parent-crop soil moisture prior to harvest, average regrowth soil moisture percentage or the summation of stress-free days. It was concluded that environmental limitations to growth in this environment, though relatively short lived, were significant in reducing long-term yields. Growth, however, was possible at all times.