Soil Moisture Tension Research Articles

Thermal properties of two organic (peat, pine bark) and two inorganic (perlite, clay) horticultural substrates

Thermal properties such as thermal conductivity and heat capacity of two organic (peat, pine bark) and two inorganic (perlite, expanded clay) horticultural substrates are studied. The thermal conductivity is determined using the apparatus described by JANSE & BOREL (1965). The relation between moisture content and moisture tension and thermal conductivity is determined for these horticultural substrates. The heat capacity is calculated as a function of the moisture content for the four horticultural substrates. A very good relation is found between thermal conductivity and soil moisture tension which can be used as a characteristic for the heat economy of horticultural substrates.

The interactions of water and fertilizer nitrogen in effects on growth pattern and yield of potatoes

SummaryThree field experiments in 2 years were made in S.E. Scotland to investigate the effect of water (normal rainfall or irrigation to maintain soil moisture tension between pF 2·0 and 2·5) on the response of the potato crop to nitrogen fertilizer (0, 100, 200 or 300 kg N/ha).Final tuber yield was closely related to leaf area duration. Addition of water reduced the delay in early haulm growth resulting from fertilizer nitrogen application. The beneficial effect of reducing moisture tension could not be related to water per se, nitrate, ammonium or conductivity levels in the fertilizer band or nitrogen uptake. Accumulation of nitrate in the roots and stems + petioles early in the season indicated that the rate of protein synthesis was reduced at high soil moisture tension in the presence of fertilizer nitrogen.In a long growing season (1971, 153 days) there was a significant response of tuber yield to nitrogen, with an increase in yield even at the highest rate tested (300 kg N/ha) and irrigation enhanced this response.In a normal season (1970, ca.130 days) there was a significant irrigation x nitrogen interaction on tuber yield. Irrigation increased the optimum rate of nitrogen from 100 to 200 kg N/ha in one experiment and from nil to 200 kg N/ha in another.Addition of water increased the number of tubers at harvest but the effect of nitrogen was less consistent. Yield increases resulting from application of nitrogen or reduction in soil moisture tension were mainly due to increases in the proportion of large tubers.

Plant root distribution and water use patterns of some pasture and crop species

Abstract During a summer of lower-than-average rainfall, yield, root distribution, and soil moisture tension were measured for perennial ryegrass, white clover, ryegrass-clover mixture, cocksfoot, wheat, maize, and lucerne growng on a deep free-draining soil. In all species most roots occurred in the top 20 cm of soil, root numbers decreasing down to 100 cm, with smaller variable numbers at the maximum depth sampled. Cocksfoot and perennial ryegrass had the highest root numbers in the top 40 cm, cocksfoot roots continuing to be more numerous to 140 cm. The effective depth of the soil exploited for water by all species except lucerne was approximately 130 cm. Lucerne extracted water from at least 210 cm. Lucerne, maize, and cocksfoot produced at least twice as much dry matter as ryegrass and white clover, both of which had stopped growing by the final harvest. Maize which was not sown until late spring did not begin to deplete the soil water until the pasture species had used much of that which was available. Lucerne depleted the soil water uniformly at all levels of the profile to 150 cm, whereas all other plots showed depletion first near the surface and only later at greater depths This could be significant in maintaining nutrient availability under drying conditions.

Two pot techniques for controlled-environment cabinets

Abstract In one technique, water transpired by the crop is replenished with a dilute nutrient solution supplied through a nylon wick. Nutrients are supplied on demand, avoiding infrequent heavy applications, and soil air and moisture tension remain constant. In the second, test plant roots grow through a soil sample into a nutrient solution beneath. Nutrients can be applied through either the soil or the solution, and the sites of nutrient interactions identified. Both techniques are economical in materials, space, and operator time.

Automatic Feedback Control to Maintain Constant Soil Moisture Tension in the Study of Drought Tolerance in Rice

AbstractWe have developed a greenhouse technique by which a chosen soil moisture tension can be maintained continuously. The setup for supplying water at relatively constant soil moisture tension in pots includes five major components—water tank, W‐tube, water distribution system, soil moisture tension sensors, and pots. The W‐tube, which contains a predetermined amount of Hg, controls the soil moisture tension in the pots. Water can flow freely from the tank to the pots through the distribution system whenever the soil moisture tension exceeds that desired. Response to the sensors' demand for water is rapid.We have successfully used this setup to compare relative drought tolerance of rice (Oryza sativa L.) varieties and breeding lines. Another use of this setup might be to measure evapotranspiration (ET) almost instantaneously; the technique might be useful in some soil‐plant‐atmosphere‐water relationship studies.

Onion‐Seed Yield and Quality as Affected by Irrigation Management1

AbstractThe effects of soil moisture, sprinkler irrigation, and misting (5 min at 30‐min intervals) on hybrid onion‐seed (Allium cepa L.) production were evaluated at Kimberly, Idaho. Sprinkling and misting treatments were included to determine if sprinkler irrigation could be used for onion‐seed production, and if evaporative cooling (misting) would alleviate the scalding of umbels at excessively high temperatures. Results showed that reasonable onion‐seed yields could be obtained with sprinkler irrigation in spite of anticipated adverse effects on pollination. In areas with high daytime temperatures, misting could be used to cool the umbels, as much as 15 C for about 20 min, although it does not seem necessary for the low 32 to 35 C daytime temperatures at Kimberly. The highest onion‐seed yields were obtained with the furrow‐irrigation treatment where water was applied when tensiometers at 20‐cm depth read about 0.5 bar soil moisture tension (furrow adequate). The addition of misting to furrow irrigation decreased seed yields 19%. Furrow irrigating at 0.4 bar decreased yields 26% below those obtained with irrigation at 0.5 bar. While overirrigation adversely affected yield, irrigation treatment had only a slight effect on seed weight and vigor.

Induction of Frost Hardiness in Stem Cortical Tissues of Cornus stolonifera Michx. by Water Stress

Water supply and day length were varied in cold hardiness studies of red osier dogwood plants (Cornus stolonifera Michx.). The frost killing temperature, the content and freezing of stem cortical tissue water along with soil moisture content and tension were evaluated. Seven days of water stress in long and short day photoperiod regimes caused a rapid decrease in soil moisture content and plant water potential. During the same period, the frost hardiness increased from -3 to -11 C. Further water stress treatment had little effect. Control plants in short days showed only a gradual decrease in plant water potential and only gradually increased in frost hardiness while control plants in long days were unchanged. Freezing studies using nuclear magnetic resonance showed that increased hardiness in water-stressed plants resulted from both an increased tolerance of freezing and an increased avoidance of freezing, the latter resulting from higher solute concentration in the tissue solutions. The short day controls also showed similar changes; however, the changes were smaller over the 21 days of the study.

Geometrische Interpolation von Saugspannungsverteilungen

A procedure for interpolating the depth distribution of soil moisture tensionA programmable procedure is described to compute hydraulic gradients from soil moisture tensions non‐linearly distributed with depth.This interpolation‐technique is based upon a geometrical procedure. Compared with other curve smoothing techniques it is flexible with respect to the given data constellation and requires a relatively small computational effort.This method is compared with that of cubic splines.

Grapevine Response to Irrigation and Trellis Treatments in the Salinas Valley

Four irrigation treatments (nonirrigation, early cut off, early cut back and late cut off) each with three trellis types (2-wire vertical, 1.4 m high; 3-wire vertical, 1.7 m high; and 2-wire vertical, 1.7 m high with a 0.6-m cross-arm were tested to determine effects on the yield and growth of Cabernet Sauvignon and on the composition of the fruit. The split-split-plot experiment was conducted in a low rainfall Mediterranean climate near Soledad in the Salinas Valley of Monterey County, California. The soils were classified by the Soil Conservation Service as a Chualar loam. Topsoil and root depth was uniformly shallow, approximating 50 cm. Irrigations were scheduled primarily on the basis of tensiometer instruments 40 cm deep. Soil suctions in the irrigated plots were maintained between 10-30 cb during the early season until vine growth resulted in uniform canopy density down the vine row with some shoots trailing the ground. Irrigation then was discontinued for the early cut off treatment; soil suctions were allowed to approach or exceed 80 cb for the early cut back treatment before subsequent irrigations in order to retard further shoot growth; but suctions ranging between 10-50 cb were maintained for the late cut off treatment through mid-September. A soil moisture tension of 1-7 bars at harvest was the goal for the last two treatments. Statistical analysis showed significant differences in °Brix, total acidity, pH, yield of both grapes and fruit sugars, cluster numbers and weights, berry weights, bloom-time petiole percentages of Na, K, and Mg, harvest-time must levels of arginine, and pruning weights. The late cut off treatment showed delayed maturity and lower yields than the early cut back treatment. The non irrigated and early cut off treatment did not result in a more favorable sugar, acid and pH balance, and resulted in lower yields than the early cut back treatment. The 2 wire vertical trellis with a cross-arm resulted in higher yields than the other two trellises only for the early cut back and late cut off irrigation treatments receiving pre-harvest irrigations.

Soil and plant water status under sprinkling and trickling

In a comparison of methods of irrigating tomatoes on the sand dunes of northern Sinai (El-Arish region), yields obtained by trickling were higher than those by sprinkling. The present study attempts to explain these results from a physical point of view. Before each irrigation and during a complete irrigation cycle measurements were made of soil moisture content, moisture tension in the root zone, and plant water potential. The amount of water applied was based on Class A pan evaporation. At 24 h after the end of an irrigation the soil moisture content was 4% by weight, regardless of the quantity of water applied. The soil moisture tension and the plant water potential were similar for both methods during the first 24 h after irrigation, but the values rose gradually and were higher at the end of the sprinkle irrigation cycle which lasted 3 days, than at the end of the daily trickle irrigation cycle. These differences in soil moisture tension affected the plant water potential and in turn plant development and yield.

Effect of different soil moisture regimes and canopy wetting on ‘Baccara’ roses

The combined effect of different irrigation regimes and canopy wetting treatments on flower yield and flower quality was examined with ‘Baccara’ roses. Total yields of 390 flowers per m 2, of which 290 were of saleable quality for the period October–May, were obtained when the soil water tension at a depth of 15–20 cm was maintained below 4–6 centibar (cb). An increase in water tension up to 10–15 cb caused a 10 % decrease in yield. Wetting the canopy reduced the number of flowers and did not counteract the reduction in yield caused by the increase in soil water tension. Wetting the canopy slightly reduced plant surface temperature, mainly on dry and hot days. Wetting also increased the weight of flower buds obtained under irrigation treatments which maintained soil moisture tension below 5 cb (a low soil moisture treatment). The weight per unit length of flower stem increased when the canopy was wetted under all irrigation treatments. In spring, canopy wetting reduced the decrease in flower weight and in leaf area, and completely prevented the decrease in flower stem weight.

Aspect differences in an unimproved hill country pasture

Abstract A number of climatic variables were monitored on north, south, east, and west aspects of a hill in the foothills of the southern Ruahine Range, New Zealand, over a 12-month period. Wind speed values were consistently higher on the north aspect than on the west, east, and south aspects. Differences in net radiation between the north and south aspects were largest during the winter and smallest during the summer months. All evapotranspira-tion values calculated were larger for the north than for the south aspect. Soil moisture tension differences were not detected during winter, but during the remainder of the year soil of the north aspect had the highest moisture tension and that of the south aspect the lowest. Rainfall differences among aspects were difficult to detect because of the effects cf wind on rain gauge catch. Differences among aspects in average monthly 40 mm air temperature were not apparent. However, large differences in the average monthly 40 mm soil temperature of the various aspects were detected. During the January to August period the north aspect was warmest and the south aspect coolest, but for the remainder of the year the east aspect was warmest. The interrelationships of some of the above variables are discussed. It is suggested that the significance of wind in the hill pasture environment is underestimated.

Effect of Soil Moisture Tension and Amendments on Yields and on Herbage N, P, and S Concentrations of Alfalfa1

AbstractLow protein concentration has been observed in alfalfa herbage grown on Gray Wooded Luvisol soils, particularly in cool, wet years. Nutrient deficiencies of N, P, and S also occur on these soils. The objectives of this experiment were to determine how soil moisture and soil type interact with amendments to increase yield and change N, P, and S concentrations in alfalfa (Medicago media Pers.) herbage grown in the greenhouse.Three Gray Wooded Luvisols, Typic Cryoboralf (Arborfield clay, Garrick clay loam, Mollic Cryoboralf, and Waitville loam) and one Dark Gray Luvisol soil (Nipawin sandy clay loam) × two soil moisture tensions (100 and 151 millibars) were main treatments. Amendments of cattle manure, sedge peat, and wheat straw were applied on subplots at 2.5y0 of soil weight. Additional subplots of a control and nitrate (70 μg N/g soil before each crop) were added. Two crops of barley (Hordeum vulgare L.) and one of rape (Brassica napus L.) were grown before ‘Rambler’ alfalfa.Yield of alfalfa was significantly related to moisture use (r2 = 77% in cut 1; r2 = 78% in cut 2). Moisture use by alfalfa was higher with cattle manure incorporated in the heavier textured Garrick clay loam and Arborfield clay soils than for other amendments or soil types. The manure treatment applied to Garrick clay loam and Arborfield clay soils under low soil moisture tension (LSMT = 100 millibars) produced the highest herbage yields.In the first‐cut only, N concentration of alfalfa herbage was higher under high soil moisture tension (HSMT = 151 millibars) than LSMT (5.0 vs. 4.8% N) and was higher for ammonium nitrate than for manure or peat amended soils. Concentration of P in alfalfa herbage was significantly higher under LSMT than HSMT. Concentration of S in herbage was significantly lower under LSMT than under HSMT only for cut 1.In general, LSMT interacting with soil type and amendments markedly increased alfalfa yields, reduced N and S, and increased P concentration in herbage as compared with HSMT.

Título en español.

Se sembró un tipo de sorgo para la producción de grano, RS 671, a principios de enero de 1973 en Barranquitas (Oxisol) y en Corozal (Ultisol). Las parcelas se encalaron, se abonaron y se trataron con plaguicidas antes de la siembra. En ambos sitios, hubo que resembrar a mediados de marzo por la pobre germinación de las semillas. Durante el ciclo de desarrollo de la cosecha se tomaron datos meterológicos, de la humedad del suelo y la tensión a la que esta era retenida, del crecimiento y déficit hídrico de la planta y de la profundidad de penetración de las raíces. A cosechar, se tomaron datos de rendimiento en grano y rastrojo. En cada sitio, se regó una parcela cuantas veces fue necesario para mantener la tensión con la que el suelo retenía el agua a menos de 1 bar. Los resultados indican que, durante una sequía prolongada y al tiempo en que el grano se está llenando, el sorgo sembrado en el Oxisol extrajo agua a 120 cm. de profundidad; las plantas sufrieron por falta de agua después que la tensión con la que el suelo la retenía a 90 cm. de profundidad, llegó a 15 bares. En el Ultisol, las plantas de sorgo no pudieron extraer eficazmente la humedad disponible a profundidades mayores de 45 cm. El crecimiento de las plantas en el Oxisol fue mayor que en el Ultisol. La compactación relativa fue mayor en el Ultisol que en el Oxisol. Es evidente que el sorgo pudo utilizar mejor que el maíz el agua disponible en el suelo cuando ambos se sembraron en un Ultisol.

Growth and Mineral Composition of Rice at Various Soil Moisture Tensions and Oxygen Levels

AbstractThe better growth of rice in a flooded soil as compared to an upland soil has been attributed to the reducing conditions caused by submergence. No study has been carried out, however, in which the effects of the soil moisture status has been separated from the effect of the oxidation‐reduction conditions of the soil.In the study reported here, the effect of soil oxidation‐reduction conditions on early growth and mineral composition of lowland rice (Oryza sativa L. ‘Saturn’) was determined by growing plants in artificially packed soil columns maintained under different soil moisture tension and oxygen conditions. Since soil aeration is largely governed by the moisture status of the soil, this study was designed to separate these effects by subjecting the rice plant to different aeration conditions while at the same time attempting not to limit moisture supply. In one experiment different redox conditions were established by maintaining soil columns at soil moisture tensions ranging from 0 to 80 cm during growth of the plants. In a second experiment plants were grown at soil oxygen levels of 0, 3, 8, and 12% while soil moisture was maintained at 10 cm moisture tension. Vegetative growth of rice was greater under reduced conditions than under oxidized conditions in both experiments. The P concentration of the plant was much higher under reduced conditions than under oxidized conditions. Reduced conditions increased the solubility of P, Fe, and Mn in the soil although no consistent effect of reducing conditions on plant uptake of Fe and Mn was observed.

Effect of Bulk Density and Moisture Tension on Corn Shoot Growth

ABSTRACT SOIL bulk density and moisture tension influence soil resistance to penetration and also the shoot growth. Present studies on influence of crust strength on shoot growth or seedling emergence are limited, particularly for corn. The objectives of this study were to determine, (a) the effect of bulk density and moisture tension on soil resistance to penetration, and (b) the effect of bulk density and moisture tension on shoot growth. The empha-sis was given to find whether an inter-relationship between corn shoot growth and soil resistance might exist and that this interrelationship may be further influenced by moisture tension. The corn shoot growth be-haviour may be similar to root growth reported in the literature. Soil resis-tance to a penetrating probe and shoot growth were studied at different bulk density and moisture tension combinations produced by using a hy-draulic press and pressure membrane apparatus. Three-dimensional plots of generated soil resistance values and of generated shoot growth val-ues, as a function of bulk density and moisture tension, were constructed. A three-dimensional plot of generated shoot growth values as a function of soil resistance and moisture tension was also constructed. Soil resistance to penetration was observed to be influenced by both bulk density and moisture tension. At any bulk density, the soil resistance tends to increase, with increasing moisture tension, to a maximum and then level off. The above phenomena is more pronounced at the lower than at the higher bulk densities. Shoot growth was observed to be influenced by both bulk density and moisture tension. Soil resistance to penetration and moisture tension influenced the shoot growth. An inter-relationship between corn shoot growth and soil resistance exists and the lower the moisture tension, the lower the limiting soil resistance. The behaviour of corn shoot growth and root growth was observed to be similar. Analysis of the shoot growth data, as influenced by soil bulk density and moisture tension, indicated that till-age and soil management practices should be directed to maintaining a minimum soil resistance and a maxi-mum moisture content, below satur-ation, in the zone of seedling emergence.

Peanut Responses to Soil Water Variables in the Southeast1

Abstract Three peanut (Arachis hypogaea) varieties were maintained at soil water levels ranging from moderately wet to very dry. Pod yield and quality were significantly reduced in treatments receiving less than about 30 cm of water during the growing season. Although not statistically different, yield and quality tended to increase as irrigation amounts increased from 40 to about 60 cm. Average harvestable yields for 4 years were 4464, 5080 and 4543 kg/ha for Florigiant, Florunner and Tifspan, respectively, when irrigated to a profile depth of 60 cm when the soil moisture tension in the surface 30 cm reached 0.2 bar. This compares with yields of 2631, 3341 and 3125 kg/ha for Florigiant, Florunner and Tifspan, respectively, when the soil water tension in the surface 30 cm profile was allowed to reach 15.0 bars. Water extraction to a depth of 106 cm was recorded for all three varieties. Apparent plant use of water from profile depths greater than 60 cm was observed at about 75 days after planting. Evapotranspiration vs age relationships were developed from daily soil water measurements to a 1.2 m soil depth.

Irrigation Schedules for Sugarbeets on Medium and Coarse Textured Soils in the Northern Great Plains1

AbstractAn increase in the access to irrigation water in the Northern Great Plains is effecting large increases in the acreages of soils being irrigated. Much of this water is being applied to medium to coarse‐textured soils which hold a maximum of 7 to 12 cm of available water in a 152 cm deep profile. An investigation was conducted in the field to devise a system, using tensiometers, to schedule the application of irrigation water to sugarbeets growing on these soils. Tensiometers were installed at various soil depths, and irrigation water was applied with a small plot irrigator when soil moisture tension reached a predetermined level.One tensiometer located at the 45 cm depth was equally effective in scheduling as two tensiometers, one positioned at a depth of 30 and one at 61 cm. Maximum crude sugar yields of 8.4 to 8.8 metric tons/ha were obtained in 1971 and 1973, respectively. Total water use efficiency was 0.15 to 0.16 metric tons of crude sugar/ha per cm. The maximum irrigation water use efficiencies were 0.32 and 0.36 for 1971 and 1973, respectively. It is concluded that 56 to 62 cm of water, well distributed throughout the growing season, is sufficient for sugarbeet production is southeastern North Dakota in a year of normal growing season temperatures.

Fate of Nitrogen and Phosphorus in Soils Under Septic Tank Waste Disposal Fields

ABSTRACT PROBABLE nitrogen forms in soils under septic tank waste disposal fields are predicted by correlating observed soil moisture tensions with aeration status. The conditions beneath most waste disposal fields are sufficiently aerobic for nitrate to be the probably nitrogen form. The probable phosphorus form would depend upon many factors including mineral content and pH of the soil. Due to high P concentration in septic tank wastes, both sorption and decomposition-precipitation re-actions must be considered when determining P movement. Only in soils with little sorption capacity would the pollution potential of phosphorus from septic tank waste be considerable.

Root Regeneration of Fall-Lifted White Spruce Nursery Stock in Relation to Soil Moisture Content

The root regenerating potential of fall-lifted 2+0 white spruce nursery stock is described after transplanting into soil-maintained at 8, 10 and 15% soil moisture content (SMC) in glass fronted root boxes. At 15% SMC (0.1 bar soil moisture tension), which is close to field capacity, root regeneration began 10 days after transplanting and root elongation continued at a high rate for the remainder of a 40-day study period. At 10% SMC (0.6 bar SMT) root regeneration was delayed until 20 days after transplanting and root elongation was at a slower rate. At 8% SMC (1.5 bars) root regeneration and elongation was negligible. Plant moisture stress measured at 40 days was least when root regeneration was most and vice versa. The results suggest that field planting of white spruce in soils with moisture tensions of over 0.6 bar will be hazardous.