NITROGEN TRANSFORMATIONS NEAR UREA IN SOIL WITH DIFFERENT WATER POTENTIALS

1988 ◽  
Vol 68 (3) ◽  
pp. 569-576 ◽  
Author(s):  
YADVINDER SINGH ◽  
E. G. BEAUCHAMP
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Incubation Period ◽  
Relative Rate ◽  
Soil Water Potential ◽  
Nitrification Inhibitor ◽  
Silt Loam ◽  
Nitrogen Transformations ◽  
Water Potentials ◽  
Initial Soil

Two laboratory incubation experiments were conducted to determine the effect of initial soil water potential on the transformation of urea in large granules to nitrite and nitrate. In the first experiment two soils varying in initial soil water potentials (− 70 and − 140 kPa) were incubated with 2 g urea granules with and without a nitrification inhibitor (dicyandiamide) at 15 °C for 35 d. Only a trace of [Formula: see text] accumulated in a Brookston clay (pH 6.0) during the transformation of urea in 2 g granules. Accumulation of [Formula: see text] was also small (4–6 μg N g−1) in Conestogo silt loam (pH 7.6). Incorporation of dicyandiamide (DCD) into the urea granule at 50 g kg−1 urea significantly reduced the accumulation of [Formula: see text] in this soil. The relative rate of nitrification in the absence of DCD at −140 kPa water potential was 63.5% of that at −70 kPa (average of two soils). DCD reduced the nitrification of urea in 2 g granules by 85% during the 35-d period. In the second experiment a uniform layer of 2 g urea was placed in the center of 20-cm-long cores of Conestogo silt loam with three initial water potentials (−35, −60 and −120 kPa) and the soil was incubated at 15 °C for 45 d. The rate of urea hydrolysis was lowest at −120 kPa and greatest at −35 kPa. Soil pH in the vicinity of the urea layer increased from 7.6 to 9.1 and [Formula: see text] concentration was greater than 3000 μg g−1 soil. There were no significant differences in pH or [Formula: see text] concentration with the three soil water potential treatments at the 10th day of the incubation period. But, in the latter part of the incubation period, pH and [Formula: see text] concentration decreased with increasing soil water potential due to a higher rate of nitrification. Diffusion of various N species including [Formula: see text] was probably greater with the highest water potential treatment. Only small quantities of [Formula: see text] accumulated during nitrification of urea – N. Nitrification of urea increased with increasing water potential. After 35 d of incubation, 19.3, 15.4 and 8.9% of the applied urea had apparently nitrified at −35, −60 and −120 kPa, respectively. Nitrifier activity was completely inhibited in the 0- to 2-cm zone near the urea layer for 35 days. Nitrifier activity increased from an initial level of 8.5 to 73 μg [Formula: see text] in the 3- to 7-cm zone over the 35-d period. Nitrifier activity also increased with increasing soil water potential. Key words: Urea transformation, nitrification, water potential, large granules, nitrifier activity, [Formula: see text] production

scholarly journals 689 PB 239 SOIL WATER POTENTIAL IRRIGATION CRITERIA FOR ONION PRODUCTION

HortScience ◽  
1994 ◽  
Vol 29 (5) ◽  
pp. 531e-531
Author(s):  
Erik B. G. Feibert ◽  
Clint C. Shock ◽  
Monty Saunders
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Soil Water Potential ◽  
Furrow Irrigation ◽  
Silt Loam ◽  
Yield And Quality ◽  
Water Potentials ◽  
Granular Matrix ◽  
Irrigation Treatments

Onions were grown with different soil water potentials as irrigation criteria to determine the soil water potential at which optimum onion yield and quality occurs. Furrow irrigation treatments in 1992 and 1993 consisted of six soil water potential thresholds (-12.5 to -100 kPa). Soil water potential in the first foot of soil was measured by granular matrix sensors (Watermark Model 200SS, Irrometer Co., Riverside, CA) that had been previously calibrated to tensiometers on the same silt loam series. Both years, yield and market grade based on bulb size (more jumbo and colossal onions) increased with wetter treatments. In 1993, a relatively cool year, onion grade peaked at -37.5 kPa due to a significant increase in rot during storage following the wetter treatments. These results suggest the importance of using moisture criteria to schedule irrigations for onions.

Soil Water Potential and Bromacil Uptake by Wheat

Weed Science ◽  
1975 ◽  
Vol 23 (2) ◽  
pp. 127-130 ◽  
Author(s):  
J. D. Schreiber ◽  
V. V. Volk ◽  
L. Boersma
Keyword(s):  
Triticum Aestivum ◽  
Water Potential ◽  
Soil Water ◽  
Transpiration Rate ◽  
Soil Water Potential ◽  
Dry Weight ◽  
Silt Loam ◽  
High Concentration ◽  
Water Potentials ◽  
Application Rates

The uptake of14C labeled bromacil [5-bromo-3-sec-butyl-6-methyluracil] by wheat plants (Triticum aestivumL. ‘Gaines’) grown in a Woodburn silt loam was studied at soil water potentials of −0.35 and −2.50 bars, and in solutions containing 2.0 and 4.5μg/ml bromacil. Transpiration rate, shoot and root dry weight, and bromacil content were measured as a function of time. Bromacil uptake into the root and foliar portions of the wheat plants increased with time. At the low bromacil concentration, 70%, and at the high concentration, 42%, more bromacil was taken up by the plant at the higher soil water potential. Uptake of bromacil increased concurrently with increased transpiration of water. The bromacil concentration in the transpiration stream was greater at the −0.35 bar than at the −2.50 bar soil water potential at both bromacil application rates. Transpiration rates of the plants treated with bromacil were nearly the same after a 40-hr exposure at both soil water potentials. The rate of bromacil uptake and accumulation may be influenced by the effect of soil water potential on the apoplastic movement of water and solutes in the roots.

scholarly journals `Ben Lear' and `Stevens' Cranberry Root and Shoot Growth Response to Soil Water Potential

HortScience ◽  
2005 ◽  
Vol 40 (3) ◽  
pp. 795-798 ◽  
Author(s):  
Dana L. Baumann ◽  
Beth Ann Workmaster ◽  
Kevin R. Kosola
Keyword(s):  
Root Growth ◽  
Water Potential ◽  
Soil Water ◽  
Leaf Area ◽  
Growth Rates ◽  
Soil Water Potential ◽  
Relative Growth ◽  
Relative Growth Rates ◽  
Water Potentials ◽  
Whole Plant

Wisconsin cranberry growers report that fruit production by the cranberry cultivar `Ben Lear' (Vaccinium macrocarpon Ait.) is low in beds with poor drainage, while the cultivar `Stevens' is less sensitive to these conditions. We hypothesized that `Ben Lear' and `Stevens' would differ in their root growth and mortality response to variation in soil water potential. Rooted cuttings of each cultivar were grown in a green-house in sand-filled pots with three different soil water potentials which were regulated by a hanging water column below a fritted ceramic plate. A minirhizotron camera was used to record root growth and mortality weekly for five weeks. Root mortality was negligible (2% to 6%). Whole plant relative growth rates were greatest for both cultivars under the wettest conditions. Rooting depth was shallowest under the wettest conditions. Whole-plant relative growth rates of `Ben Lear' were higher than `Stevens' at all soil water potentials. `Stevens' plants had significantly higher root to shoot ratios and lower leaf area ratios than `Ben Lear' plants, and produced more total root length than `Ben Lear' at all soil water potentials. Shallow rooting, high leaf area ratio, and low allocation to root production by `Ben Lear' plants may lead to greater susceptibility to drought stress than `Stevens' plants in poorly drained cranberry beds.

THE EFFECT OF SOIL WATER POTENTIAL, TEMPERATURE AND SEEDING DEPTH ON SEEDLING EMERGENCE OF WHEAT

1979 ◽  
Vol 59 (3) ◽  
pp. 259-264 ◽  
Author(s):  
R. DE JONG ◽  
K. F. BEST
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Minimum Temperature ◽  
Seedling Emergence ◽  
Potential Temperature ◽  
Soil Water Potential ◽  
Triticum Aestivum L ◽  
Planting Dates ◽  
Water Potentials ◽  
Soil Temperatures

Daily emergence counts were made on Canthatch wheat (Triticum aestivum L.) grown in five soil types, at four soil temperatures and three water potentials and planted at five different depths. Regardless of soil type, soil water potential or depth of planting, 50% emergence generally occurred within a week at 19.4 and 26.7 °C, and within 2 wk at 12.2 °C, but it took up to 6 wk at 5 °C. The heat sum required to attain 50% seedling emergence did not increase significantly with decreasing soil water potentials, but the minimum temperature for emergence dropped from 1.3 to 0.2 °C as the water potential decreased from −⅓ to −10 bar. It was suggested that the seedlings compensated for the increased water stress by lowering their minimum temperature requirements. Increasing the planting depth not only increased the heat requirement for emergence, but it also increased the variability of emergence, especially at low temperatures. Practical aspects concerning planting dates and depths were considered.

Modifying sexual expression of containerized jack pine by topping, altering soil nitrogen and water, and applying gibberellins

1994 ◽  
Vol 24 (5) ◽  
pp. 869-877 ◽  
Author(s):  
W.H. Fogal ◽  
S.J. Coleman ◽  
M.S. Wolynetz ◽  
H.O. Schooley ◽  
S.M. Lopushanski ◽  
...  
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Soil Nitrogen ◽  
Soil Water Potential ◽  
Jack Pine ◽  
Sexual Expression ◽  
Growth Responses ◽  
Tree Crown ◽  
N Supply ◽  
Water Potentials

The numbers of seed strobili and pollen strobilus clusters and the extent of branch terminal growth were determined on 6-year-old containerized jack pine (Pinusbanksiana Lamb.) trees following modification of the soil nitrogen (N) supply (NH4NO3 at 3, 100, or 300 mg N/L; NO3− at 100 mg N/L; or NH4+ at 100 mg N/L in a nutrient solution), soil water supply (soil water potentials above −20 kPa compared with potentials near −70 kPa), and tree crown size (intact trees outside polythene shelters and lightly versus severely topped trees under polythene shelters). These factors were tested with or without biweekly foliar applications of spray solutions containing 400 mg/L of GA4/7. Intact trees outside polythene shelters did not display sexual or growth responses to N or GA4/7 treatments. Seed strobilus production on topped trees under shelters was not influenced by the level of topping or N supply, but it was depressed by low soil moisture potentials and stimulated by GA4/7 with high or low soil water potentials. Pollen strobilus production was depressed by severe topping and by low soil water potential; it was stimulated by GA4/7 on lightly topped trees but not on severely topped trees and by a low (3 mg N/L) N supply. In the year after treatment, terminal growth of a branch from the 2-year-old nodal whorl was not influenced by nitrogen supply or by light topping but it was increased by severe topping; it was increased by GA4/7 treatment if soil water potential was high but not with low water potential; it was depressed by low soil water potential.

Soil and plant resistance effects on transpirational and leaf water responses by groundnut to soil water potential

Soil Research ◽  
1981 ◽  
Vol 19 (1) ◽  
pp. 51 ◽  
Author(s):  
RP Samui ◽  
S Kar
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Water Uptake ◽  
Plant Resistance ◽  
Sandy Loam ◽  
Soil Water Potential ◽  
Leaf Water ◽  
Arachis Hypogea ◽  
Water Potentials ◽  
Soil Water Conditions

The phasic and diurnal leaf water potential (�L) and transpirational responses to soil water potential by groundnut (Arachis hypogea L.) were investigated under controlled soil water conditions in a glasshouse. Three different soil water potentials (�s) in the tensiometric ranges were maintained in a lateritic sandy loam soil (Oxisol) during the seedling (S1), branching (S2) and peg formation (S3) stages of groundnut. Measured values of �s, �L rooting density, soil capillary conductivity and transpiration rate were used to calculate the soil and plant resistances to water uptake by the plant. The soil and plant resistances to water uptake by the groundnut plant increased appreciably as the soil water potential decreased from -0.11 to -0.70 bar. Plant resistance (Rp) was two to three orders of magnitude higher than soil resistance (Rs). Rs decreased with growth of the plant, whereas Rp increased, especially at -0.7 bar �s, Decreases in transpiration at �s lower than -0.33 bar were closely associated with the increases in the plant and soil resistances, and with lower leaf water potentials.

The influence of temperature and soil water potential on the leaf extension rate of perennial ryegrass in Northern Ireland

1979 ◽  
Vol 92 (1) ◽  
pp. 175-183 ◽  
Author(s):  
J. D. H. Keatinge ◽  
R. H. Stewart ◽  
M. K. Garrett
Keyword(s):  
Northern Ireland ◽  
Water Potential ◽  
Soil Water ◽  
Perennial Ryegrass ◽  
Freezing Point ◽  
Soil Water Potential ◽  
Extension Rate ◽  
Water Potentials ◽  
Temperature Records ◽  
Leaf Extension

SummaryThe rate of leaf extension in swards of the perennial ryegrass cv. Perma was monitored continuously from March 1976 to September 1977 in Northern Ireland. In this period air temperature and soil water potential were shown to be closely correlated with leaf extension rate. Simple linear expressions are shown to adequately describe the relationship between temperature and leaf extension rate when the year is divided into a winter phase, in which sward growth is very slow, and the remainder of the year in which temperature is high enough to allow significant sward production. Leaf extension growth occurred at all temperatures above freezing point. Soil water potentials of 0·15 MPa are shown to be capable of significantly reducing leaf extension rate. However, the occurrence of such soil water potentials are sufficiently rare in Northern Ireland as to permit prediction of leaf extension rates in perennial ryegrass from simple daily temperature records.

Influence of soil water potential and mycorrhizal colonization on root growth of yellow-poplar and sweet gum seedlings grown in compacted soil

1988 ◽  
Vol 18 (11) ◽  
pp. 1392-1396 ◽  
Author(s):  
G. L. Simmons ◽  
P. E. Pope
Keyword(s):  
Root Growth ◽  
Water Potential ◽  
Bulk Density ◽  
Soil Water ◽  
Root Length ◽  
Soil Water Potential ◽  
Mechanical Resistance ◽  
Yellow Poplar ◽  
Greenhouse Study ◽  
Water Potentials

A greenhouse study was conducted to determine the influence of soil water potential and endomycorrhizal fungi on root growth of yellow-poplar (Liriodendrontulipifera L.) and sweet gum (Liquidambarstyraciflua L.) seedlings grown at three soil bulk densities. Silt loam soil was compacted in PVC pots to bulk densities of 1.25 (low), 1.40 (medium), or 1.55 (high) Mg • m−3, and equilibrated at −10 kPa soil water potential. Newly germinated seedlings were transplanted into the pots, inoculated with fungal chlamydospores of Glomusmacrocarpum or Glomusfasciculaturn, or distilled water (control), and grown for 3 months at −10 or −300 kPa soil water potential. Total porosity, air-filled porosity, water content, and mechanical resistance of the soil were determined for samples compacted to the same bulk densities and equilibrated at the same soil water potentials as were used in the greenhouse study. Root growth was reduced by the high mechanical resistance caused by bulk densities of 1.40 and 1.55 Mg • m−3 at −300 kPa water potential. At both water potentials, total length of lateral roots and fibrosity of the root system of both tree species decreased significantly when bulk density increased from 1.40 to 1.55 Mg • m−3. Air-filled porosity less than 0.12 m3 • m−3 limited root growth when water potential was −10 kPa, and mechanical resistance greater than 3438 kPa restricted growth at −300 kPa. At −10 kPa, root length and fibrosity were greatest for inoculated sweet gum seedlings at each bulk density. At −300 kPa, sweet gum seedlings inoculated with G. fasciculatum had the greatest root length and fibrosity at the low and medium bulk densities. Mycorrhizal effects on root length of yellow-poplar were variable, and fibrosity was not significantly affected by mycorrhizal treatment.

scholarly journals Onion Yield and Quality Affected by Soil Water Potential as Irrigation Threshold

HortScience ◽  
1998 ◽  
Vol 33 (7) ◽  
pp. 1188-1191 ◽  
Author(s):  
C.C. Shock ◽  
E.B.G. Feibert ◽  
L.D. Saunders
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Allium Cepa ◽  
Total Yield ◽  
Soil Water Potential ◽  
Silt Loam ◽  
Marketable Yield ◽  
Yield And Quality

Onion (Allium cepa L., `Great Scott') was grown on silt loam soils and submitted to four irrigation thresholds (-25, -50, -75, and -100 kPa) in 1992 and six irrigation thresholds (-12.5, -25, -37.5, -50, -75, and -100 kPa) in 1993 and 1994. Irrigation thresholds (soil water potential measured at 0.2-m depth) were used as criteria to initiate furrow irrigations. Onions were evaluated for yield and grade after 70 days of storage. In 1992 and 1994, total yield, marketable yield, and profit increased with increasing irrigation threshold. In 1993, total yield increased with increasing irrigation threshold, but marketable yield and profit were maximized by a calculated threshold of -27 kPa due to a substantial increase of decomposition during storage with increasing threshold.

Transpiration and leaf water potentials of wheat in relation to changing soil water potential

1977 ◽  
Vol 28 (3) ◽  
pp. 355 ◽  
Author(s):  
KA Seaton ◽  
JJ Landsberg ◽  
RH Sedgley
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Transpiration Rate ◽  
Water Conservation ◽  
Root Zone ◽  
Stomatal Closure ◽  
Soil Water Potential ◽  
Stomatal Resistance ◽  
Leaf Water ◽  
Water Potentials

Changes in the transpiration rate of wheat in drying soils were followed in experiments in which plants were grown in two small weighable lysimeters in a glasshouse. Hourly measurements of soil water potential (Ψs) were made at three depths in each lysimeter. The water potential of flag leaves was measured with a pressure chamber, and stomatal resistance with a pressure drop porometer. Data on root densities and distribution were also obtained. Transpiration rates fell below estimated potential levels when the average value of Ψs in the root zone was reduced to –1 to –5 bars, depending on soil storage, root distribution and potential transpiration rate. From this point Ψs fell rapidly in the surface layers, more slowly at depth. It was found that accurate calculations of daily water uptake could be made from changes in soil water content. The minimum value of leaf water potential (�1 )attained each day declined progressively through the drying cycle, but there was evidence that stomatal resistance (rs) is not uniquely related to Ψ1; initial stomatal closure occurred at Ψ1, values which decreased from –11 to –25 bars as drying progressed. This adaptive mechanism is related to changes in osmotic potential of the leaves. Whole plant resistances (Rp), derived from leaf water potentials and fluxes through individual stems, increased as stem populations increased. In the high population lysimeter Rp decreased from 300 to 100 bar sec mm-3 as canopy transpiration rates increased from 1.5 to 4.5 x 10-4 mm sec-1. In the low population lysimeter Rp decreased from 70 to 30 bar sec mm-3 as transpiration increased from about 2.2 to 4.5 x 10-4 mm sec-1. The higher resistances appear to confer significant advantages in terms of water conservation and adaptation to drought.

Sign in / Sign up

Export Citation Format

Share Document