Influence Of Soil Moisture Content Research Articles

Influence of soil moisture content on soil temperature and heat storage under greenhouse conditions

The effect of increasing soil moisture content on soil temperature, soil reflectance and soil heat storage is studied in this work. The results show that an increase in moisture content decreases the soil temperature differences between day-time and night-time, which provides protection to the plant root system against sharp and sudden changes of soil temperature. It is also found that the solar energy absorption increases as the moisture content increases, which results in a higher heat storage capacity at higher moisture content. Finally, plant growth rate and yield increased due to the modification of plant climate at higher moisture content.

Estimation of soil microbial C by A fumigation-extraction procedure: Influence of soil moisture content

The influence of the moisture content of field-moist samples on the estimation of extractable-C flush, and consequently microbial C, by the fumigation-extraction procedure was determined with five soils from pastures. Three aspects were investigated: (1) moisture content during fumigation; (2) the effect of initial partial drying; and (3) the most suitable extraction procedure for wet, compacted samples. Values of extractable-C flush were influenced by soil moisture content during fumigation, and were sometimes appreciably lower in drier samples. Maximum values were obtained with soils wetted to ca 50% or more of their water-holding capacity (WHC), corresponding to a water potential of ca −10 kPa or higher. For all field-moist samples, adjustment of soil moisture content immediately before fumigation to values between 50 and 60% of WHC, or − 5 and − 10kPa, is therefore recommended. Rapid, partial drying at room temperature had no detectable effect on extractable-C flush values, provided the samples were rewetted to ca 50% of WHC immediately before fumigation. For extraction of wet, compacted samples, shaking on a rotary shaker at increased speed, or preferably in an end-over-end shaker, generally gave satisfactory results. Preliminary partial drying of such samples and rewetting to 50% of WHC before fumigation resulted in accurate extractable-C flush values, but could be impractical for routine use.

Soil microbial biomass estimated by the fumigation-incubation procedure: Seasonal fluctuations and influence of soil moisture content

The effects of season and soil moisture content on fumigation flushes of CO 2-C and mineral-N. and the k c and k N values of five added organisms (three fungi and two bacteria), were determined by the fumigation-incubation procedure with four soils from introduced pastures. These properties all varied seasonally, with CO 2-C flush and k c values being negatively related to field-moisture content. Laboratory adjustment of soil moisture content (up to 60% of water-holding capacity) at the time of fumigation had generally no influence on flushes of CO 2-C and mineral-N, or k C and k N values. Values of these properties were. however, significantly lower in smeared and compacted wet soil. generally because of impeded mineralization in fumigated soil. Flushes ofCO 2-C and mineral-N, and k C and k N values, were also lowered by prior incubation of soil at 60% of water-holding capacity for 7 days at 25°C. “Fumigation” biomass C values, calculated with these seasonally determined k C factors, also varied seasonally, and were generally lowest in the wettest samples. The seasonal “fumigation” biomass C values were not related significantly to other concurrently-determined indices of microbial biomass and activity (viz. biomass C estimated by substrate-induced respiration, bacterial biomass C estimated by direct observation, and dehydrogenase activity), or to mineral-N flush values, which were all significantly inter-related. The fumigation-incubation procedure is, therefore, considered unreliable for determining microbial biomass C in wet compacted soils, and an alternative procedure is then needed.

Factors affecting nitrogenase activity associated with marsh grasses and their soils from eutrophic lakes

The acetylene reduction activity (ARA) of soil-plant cores and intact, soil-free plant-root systems was used to study the influence of soil moisture content, diurnal cycles of temperature and light, and inorganic N and P on the nitrogenase activity (AR) associated with Phalaris arundinacea L. and Phragmites australis (Cav.) Trin. from two eutrophic lakes (lochs), Balgavies and Forfar. A positive correlation ( r = 0.81, n = 26) was established between AR and soil moisture content in individual soil-plant cores of Phalaris from Forfar Loch. Nitrogenase activity, soil moisture and NO 2 −-N increased with decreasing distance from lake water in Balgavies Loch. Diurnal fluctuations in AR, probably attributable to a combined effect of soil temperature and illumination changes, were observed under field conditions for Phalaris and Phragmites. Under laboratory conditions, the shading and cutting of Phalaris shoots did not inhibit ARA, which suggested that new photosynthates did not necessarily supply substrate for activity in the short term. Partial and temporary inhibition of ARA was obtained in dissected soil-plant cores after a single application of NH 4 +-N and NO 3 −-N (350 μg N g −1 fresh weight). At concentrations equivalent to 300 μg P g −1 fresh weight of Phalaris cores, PO 4 3−-P also caused partial and temporary inhibition of ARA of soil-free plant-root systems, but stimulated activity in intact simulated in situ systems.

Numerical experiments on the inland penetration of the sea breeze

AbstractA two‐dimensional primitive‐equation model is used to investigate various aspects of the sea‐breeze phenomenon. The influence of soil moisture content is examined by varying the Bowen ratio of the underlying land surface. This is equivalent to controlling the magnitude of the sensible heat flux at the ground since the diurnal variation of net radiation minus ground heat flux is approximately the same in all cases. It is found that the inland penetration rate of the sea breeze varies significantly with the degree of soil moisture. The model predicts a significant slowing of the frontal advance around midday for the case of ‘relatively weak’ sensible heating over the land, as well as reproducing the frontal acceleration observed in late afternoon for all cases. The sea‐breeze circulation detaches itself from the coastline around sunset and moves rapidly inland with diminishing magnitude and this aspect is discussed in relation to observations in the south of England.An attempt is made to model the southern England sea breeze of 14 June 1973. Various experiments are discussed, including one in which different values of Bowen ratio are specified ahead of and behind the front. Fairly good agreement is found, although it is not possible to reproduce all features of the inland penetration curve for that day.Some implications of these experiments for the production of daily forecasts by mesoscale models are briefly discussed.

Fundamental characteristics of the cosmic-ray snow gauge

A new technique for the determination of the water-equivalent of snow using cosmic ray neutrons is described on the basis of a definite relation between snow-water depths and neutron fluxes measured under snow covers. Several environmental and geographical effects on cosmic ray neutrons, including galactic cosmic ray changes, are discussed quantitatively with respect to the experimental accuracy of water-equivalent snow-water depths determined by this technique. It is shown that most of these effects introduce no serious and fundamental errors on the water-equivalent determination, except for the possible influence of soil moisture content upon neutron fluxes on the ground level where the snow gauge sensor is installed.

The influence of soil moisture on water potential, transpiration and photosynthesis of conifer seedlings

The influence of soil moisture content and soil water potential on plant water potential, transpiration and net-photosynthesis of potted larch (Larix decidua), spruce (Picea abies) and pine (Pinus cembra) was studied under constant and close to optimum conditions in a laboratory.

Effects of water and heat on seedling emergence

The effects of soil temperature and soil moisture content on germination and seedling emergence as known from literature are reviewed. To relate temperature and emergence the heat sum concept can be used. This approach is frequently applied in practice to schedule plantings, to predict maturity, to select crop varieties appropriate to different areas, etc. In such type of studies mostly the environmental air temperature is used. In the case of emergence of seeds it is advisable, however, to register the temperature in the direct environment of the seed, c.q. to measure soil temperature at sowing depth. The results of investigations on the influence of soil moisture content on germination and emergence as reported from laboratory experiments in literature, generally differ widely, mainly because of differences in applied experimental conditions as for example the use of a solution instead of soil as a germination medium. The combined effect of soil temperature and moisture content on seedling emergence was studied with four different kinds of vegetable seeds in field experiments in a clay and a sandy loam profile, both with a shallow and a deep groundwater table. Various sowing dates were applied. From temperature measurements it appeared that the mean daily temperatures of the plots with the higher groundwater tables were 1 to 2 °C lower than the temperature of the plots with the deeper groundwater tables. With the same groundwater depth, clay proved to be warmer than sandy loam. It could be concluded that on the investigated soils the difference in groundwater level was playing a more important role than the difference in type of profile. The maxima and minima in the top soil were higher and the amplitudes decreased with depth faster in soils which had a deep groundwater table. The decrease was more marked in the clay than in the sandy loam soil. It appeared that emergence was highly correlated with rainfall, and that because of more favourable hydrological properties of the soil seeds emerged earlier in sandy loam than in clay. It was found that on all sowing dates the sandy loam plots with the shallow groundwater table showed the highest emergence rate as well as the highest total emergence percentage. The mean heat sums required for 50% emergence were lower on sandy loam than on clay, and the heat sums of the shallow groundwater plots were lower than those of the deep groundwater plots. The minimum temperatures for emergence of the various seeds were calculated using only those treatments in which no limitation of water could be expected. The effect of soil moisture on emergence could be evaluated by calculating the heat sums of all treatments, taking into account the minimum temperature for emergence. As indicator for the minimum moisture content required for emergence, the first five days after sowing were used, for which the average soil moisture content was calculated from sampling data and precipitation records.

Influence of Soil-Moisture Content on the Bioactivity of Picloram

A somewhat modified version of Lambert's quantitative treatment of the influence of soil-moisture content on herbicidal activity has been applied to 4-amino-3,5,6-trichloropicolinic acid (picloram) behavior in soil. The bioactivity of picloram decreased as the soil-moisture content was increased. This was due to the effect of varying soil-moisture levels on the concentration of picloram in the soil-water phase.

Greenhouse Evaluation of the Agronomic Efficiency of Anhydrous Ammonia1

AbstractThree greenhouse pot experiments were conducted with corn grown on Mountview loam and Hartsells fine sandy loam to (a) measure the relative agronomic effectiveness of direct applications of anhydrous NH3, as influenced by preplan incubation period and schedule of application, and (b) to determine the influence of soil moisture content at time of NH3 injection on crop response to anhydrous NH3.Response of corn to anhydrous NH3 tended to be less than to an ammonium N source with shorter incubation periods, but was generally as effective as a nitrate N source except when high N rates were applied at planting. In the latter case, yields were somewhat reduced.When anhydrous NH3 was injected into the soil‐root zone according to different application schedules, corn yields were considerably reduced at the higher N levels when compared to equivalent applications of urea and NH4NO3. Yield reduction in these cases was attributed in part to root damage due to NH3 toxicity, and possibly to temporary positional unavailability of the applied N. Soil‐cultured corn plants, however, appeared to be remarkably tolerant to high levels of anhydrous NH3 when applied directly into the root zone.A small but consistent decrease in yield was observed when high levels of anhydrous NH3 were applied to soils in an air‐dry rather than moist condition.

Studies on the Photosynthesis of Forage Crops. : V. The influence of soil moisture content on the photosynthesis and respiration of seedlings in various forage crops.

Studies on the Photosynthesis of Forage Crops. : V. The influence of soil moisture content on the photosynthesis and respiration of seedlings in various forage crops.

Studies on the Relationship between the Change of Growing Season and Irrigation in Upland Crops. : II. The relationships among planting time, plant population and irrigation in soybean culture.

The relations among planting time, plant population and irrigation in soybean culture were investigated in order to appraise the practicability of irrigation in an early and a late season culture, in 1962. The results may be summarized as follows: (1) The irrigation was able to keep living leaves at the position which perviousness of light is less than the case of non-irrigation. But irrigation increased height of yellowing leaf, because it makes the leaves large and in result lessened remarkably perviousness of light into plant community. However, the thickness of leaves layer was not different between irrigation and non -irrigation plots by the reason which plant height was increased by irrigation, and also was not so much different among plant populations. Number of living leaves was increased rather by irrigation, therefore it was deduced that total leaf area increased by irrigation, and then that the photosynthetic efficiency of leaf of irrigated plot was higher than that of non-irrigation plot during the drought period. (2) In early planting the weight of stem was increased little by irrigation, but in late planting it was increased strikingly by irrigation owing to the increase of stem diameter and length. The elongation of internode is phytosociological phenomenon which occures by the deficit of light perviousness into plant community in principle. But it was affected considerably by soil moisture content, and it was recognized that the influence of soil moisture content was larger in pod-setting period when amount of transpiration increased notably. (3) The irrigation heightened or maintained highly the rate of seed yield to stem weight (seed/stem ratio). Because irrigation mitigated remarkably deficit of soil moisture derived from the vigorous growth in the most important pod-setting period when transpiration showed the maximum amount and number of pods was determined. Therefore irrigation increased pod number per m2 and seed weight per 100 seeds in each cases, and heightened the limiting point of their increase according to the high plant population, and in consequence irrigation brought similar effects to seed yields. (4) In early planting, irrigation increased seed yislds by elevation of seed/stem ratio mainly, and in late planting, increased seed yields by increase of stem weight and maintenance of higher seed/stem ratio. The seed yields of late season culture (planting early in July) were approximated to those of early season culture by irrigation and considerable high population, therefore in the case of irrigation, it was made clear that the combination between wheat or barley and late season culture of soybean was profitable strikingly.

Influence of soil moisture content on germination and emergence of seeds

This study was designed to clarify the relations of germination and emergence of several kinds of seeds to moisture content of soils, with special reference to their moisture constants and moisture supplying capacities.Seeds were planted in the soils having different moisture contents in the depth of one cm from the surface, and numbers of emerged seeds were counted daily. After the final count, seeds remaining in the soil were exposed and number of germinated seeds were counted. Physical properties of soils used were shown in Table 1.1. Minimum moisture content allowing germination of radish, rape, and sunflower seeds was close to P. W. P. (permanent wilting percentage) in the fine sandy clay loam (alluvial soil) and the fine sandy loam (volcanic ash soil), but was higher than P. W. P. in the coarse sand (river sand). Minimum moisture content allowing emergence of these seeds was a little higher than that for germination (Fig. 1).Critical moisture levels for carrot seed were higher than those for other seeds (Fig. 1). This may be due to the lower moisture absorbing power of carrot seed than that of other seeds (Table 3).2. Average number of days required for emergence of each seed was found to be almost the same in the range down to a certain critical moisture content of the soil, below which number of days increased with the decrease of moisture content. This critical point was close to the minimum capillary moisture content in each soil (Fig. 4, Table 5).3. Pre-soaking treatment decreased minimum moisture content allowing germination and emergence of pea seed, but had little effect to tomato seed, which was much smaller in size than pea seed (Fig. 5).4. Basing on the above mentioned results, it may be concluded that minimum moisture content allowing germination or emergence of seeds are determined primarily by the moisture tension of the soil, but, at the same time, it is affected by the moisture absorbing power of seed, amount of moisture which should be absorbed by the seed for its germination or emergence, and moisture holding capacity or moisture supplying power of soil.

Influence of Soil Moisture Content and Manuring Condition on Exudation of Soybean.

Using soybean variety Norin No. 2 grown under light and heavy manuring condition by pot culture, exudation was investigated under three levels of soil moisture content (Fig. 1). Soybeans were planted on May 25, and these plants were treated with dry, medium and wet soil conditions from June 22 to July 6. Except the treatment periods, they were maintained under medium soil moisture condition. The exudates were taken from detopped plants at several growing stages, and determined their volume and several inorganic components. The results obtained were summarized as follows; 1) Concerning the exudation power of soybean varies at each growing stage. In early vegetative stage, it gradually increases, and in the flower initiation stage, it shows maximum value, but thereafter it gradually decreases (Fig. 3). 2) In plants treated with dry soil condition the exudating power shows remarkable small value, but it recovers in comparatively short period when the plants were return to the medium soil moisture condition. While in plants treated with wet soil condition it does not show and distinct change (Fig. 3). 3) The exudating power of soybean plants is approximately parallel with the function of the root respiration, if these plants were at the same growing stage, or were grown under the same soil moisture condition (Table 3 & Fig. 6). 4) The concentration of each inorganic component in exudate is higher in plants treated with dry soil condition, but it is somewhat lower in plants treated with wet soil condition than with medium soil moisture condition (Table 1 & 2). By reason of difference in amount of exudate between soil moisture treatments, it is considered that the whole quantities of each nutrient translocated to top are decreased by dry treatment, while no decrease is occurred in wet treatment. 5) In the plants grown in heavy manuring condition, the root contains more amount of protein-N (Fig. 5), the respiration of root is more active (Fig. 4), the amount of exudate is more abundant (Fig. 3), the concentration of NH4-N, P, K and Mg in exudate is higher (Table 1 & 2) and the growth of top and root is more vigorous than in the plants grown in light manuring condition. Such heavy manuring condition in soybean plant will be efficient to lighten the drought damage, to hasten the recovery from such damage, and moreover to change the weak growth brought by wet soil condition to vigorous growth.

Influence of Soil Moisture Content on the Growth and Yield of Soybean. : (V) Changes of carbohydrate and nitrogen in soybean plant as affected by deficient or excessive soil moisture contents at various growing periods.

The object of this study was to trace the changes of carbohydrates and nitregen in soybean plants grown under deficient or excessive soil moisture conditions during the early vegetative, flowering and ripening periods, respectively. During the other periods, the soil moisture for the experimental plants were maintained at the same level with those for the control plants. The results obtained are summarized as follows ; 1) The total sugar content in the leaves and the stems increased in the plants under deficient soil moisture conditions, while the starch content increased abnormally in the plants under excessive soil moisture conditions. The nitrogen content in each organ decreased in all the treated plants. 2) Absorption of nitrogen was inhibited both by deficient and by excessive soil moisture conditions, and the degree of inhibition was greater in the series treated during the flowering period than in that treated during earlier periods. Accumulation of carbohydrates in plants was reduced by deficient soil moisture conditions but remarkably higher amount of carbohydrates accumulated in the plants under excessive soil moisture conditions. The degrees of inhibitionor of accumulation were also higher in the series treated during the flowering period than in those treated at the other periods. 3) In the plants under deficient soil moisture conditions during each period and under excessive ones during the earlier period (plant about 20 days after the flowering time), the amounts of total sugar and starch in leaves and stems were smaller than those in the control plants. And, the amounts of those matters translocated from the leaves and the stems to the pods were also reduced in the treated series. On the contrary, in the plants grown under excessive soil moisture conditions during the flowering or ripening periods, the most part of carbohydrates in the pods appeared to have been translocated from the leaves and the stems. However, the accumulation of nitrogen in vegetative organs and the amount of nitrogen translocated to sexual organs reduced in every treated series. In the treated plants, in general, large parts of carbohydrates and nitrogen in the pods depended on assimilation and and absorption after the flowering period. 4) In the plants under deficient or excessive soil moisture conditions during the earlier periods, vegetative growth was retarded and consequently the number of flowers was very few ; but the percentages of flower- and pod-shedding were only little different compared with those in the control plants. In the plants treated with deficient or excessive soil moisture conditions during the flowering period, the number of flowers produced was almost the same as that in the control plants, but the shedding percentage of the former was much higher.