Utility of a simple soil water budget model in agronomic research. 3. Estimation of the potential evapotranspiration function

1974 ◽  
Vol 14 (70) ◽  
pp. 684
Author(s):  
RG Fawcett ◽  
OG Carter
Keyword(s):  
Soil Water ◽  
Water Budget ◽  
Potential Evapotranspiration ◽  
Regression Equation ◽  
Wheat Crop ◽  
Budget Model ◽  
Plant Densities ◽  
Potential Transpiration

It has been shown that a regression equation relating the cumulative potential transpiration function (T/Eo) with the yield of tops, week of sowing and available fallow moisture, together with a simple budget model, can be used to estimate weekly changes in available soil water under a wheat crop. It is concluded from the data that use of the equation and budget model should be most suited to situations where plant densities are about 60 plants per m2 and the available fallow water is about 150 mm or less.

A SOIL WATER BUDGET MODEL WITH A NEARLY IMPERMEABLE LAYER

1981 ◽  
Vol 61 (2) ◽  
pp. 361-371 ◽  
Author(s):  
R. DE JONG ◽  
C. F. SHAYKEWICH
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Water Budget ◽  
Budget Model ◽  
Sink Term ◽  
Impermeable Layer ◽  
Homogeneous Soil ◽  
Potential Transpiration ◽  
System Water ◽  
Water Contents

A soil water budget model which accounted for a nearly impermeable layer in the profile was developed to describe the water content in a non-homogeneous soil-root system. Water uptake by the roots was represented by a sink term which was dependent upon the root distribution, the soil water content and the potential transpiration. The chosen boundary conditions, precipitation, evapotranspiration and a nearly impermeable layer at the bottom of the soil profile approximated those existing in the field. A submodel to calculate interception was included in the model. Data obtained from a field experiment on a clay soil were compared with calculated results for the period 1 May to 30 Sept. 1975. The overall agreement between daily measured and calculated soil water contents was excellent; all calculated values fell within 10% of the measured data. The model also yielded acceptable results in predicting the distribution of soil water through the profile.

Lupin as a biological plough: evidence for, and effects on wheat growth and yield

1989 ◽  
Vol 29 (1) ◽  
pp. 99 ◽  
Author(s):  
CWL Henderson
Keyword(s):  
Nitrogen Fixation ◽  
Soil Water ◽  
Plant Density ◽  
Crop Rotations ◽  
Growth And Yield ◽  
Wheat Crop ◽  
Sand Soil ◽  
Wheat Growth ◽  
Residual N ◽  
Plant Densities

The effects of the density of lupin (Lupinus angustifolius L. cv. Illyarrie) taproots on a following wheat crop (Tritium aestivum L. cv. Gutha) were investigated on a compacted, earthy sand soil near Geraldton, Western Australia. In 1985, plots were sown to lupins at densities ranging from 35 to 220 plants m-2. Because peak lupin biomass varied by less than 25%, and 100 kg N ha-1 of mineral fertiliser was supplied to the wheat, the effects of variation in residual N from the lupins were considered to be minimal. In 1986, all plots were split for shallow or deep tillage and wheat sown. There were no effects of tillage or lupin density on stored soil water at sowing. Growth and yield of wheat on the shallow tilled plots increased linearly with lupin plant density in the previous year, to equal or better wheat yields on the deep tilled plots, which were unaffected by lupin density. At normal farm lupin plant densities, the biological plough effect was estimated to improve wheat yields by 100 kg ha-1, substantially less than the benefits from nitrogen fixation and breaks in disease cycles. Nevertheless, it still suggests that lupin stand densities should be maintained or increased in crop rotations on compacted sands.

Utility of a simple soil water budget model in agronomic research. 2. Estimates of available soil water in relation to profile changes of soil water content and potential

1974 ◽  
Vol 14 (66) ◽  
pp. 80 ◽  
Author(s):  
RG Fawcett ◽  
OG Carter
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Water Budget ◽  
Plant Density ◽  
Budget Model ◽  
North West ◽  
The North ◽  
South Wales ◽  
Profile Changes

A study was made of the effects of plant density, time-of-sowing and level of fallow water on profile changes in soil water content and potential during the growing season of spring wheat. The pattern of soil moisture extraction was affected by all treatments although water depletion occurred chiefly in the 0-90 cm zone. The results are discussed in relation to limitations of a simple soil water budget model and to wheat cropping on the north-west slopes and plains of New South Wales.

Utility of a simple soil water budget model in agronomic research. 1. Effects of plant density, time of sowing and fallow water on available soil water under spring wheat

1973 ◽  
Vol 13 (65) ◽  
pp. 714 ◽  
Author(s):  
RG Fawcett ◽  
OG Carter
Keyword(s):  
Soil Water ◽  
Spring Wheat ◽  
Water Budget ◽  
Field Experiments ◽  
Plant Density ◽  
New South ◽  
Growing Season ◽  
Wheat Cultivars ◽  
Budget Model ◽  
South Wales

A simple soil water budget model was used to estimate weekly changes in available soil water as affected by plant density, time of sowing and level of available fallow water for spring wheat cultivars grown on a black earth in northern New South Wales. Estimated values of available water were mostly within �10 mm of observed values (ranging from 50-270 mm) obtained at four intervals during the growing season. The results are discussed in relation to both the interpretation of agronomic field experiments and use of the model in regions where conserved fallow water contributes significantly to cereal production.

FORMULE PERMETTANT D’INTEGRER L’EVAPOTRANSPIRATION ET LA PLUIE PAR UN INSTRUMENT

1962 ◽  
Vol 42 (4) ◽  
pp. 711-719
Author(s):  
C. E. Ouellet ◽  
G. Laporte
Keyword(s):  
Soil Water ◽  
Water Deficit ◽  
Water Budget ◽  
Meteorological Factors ◽  
Potential Evapotranspiration ◽  
Field Capacity ◽  
Soil Water Deficit ◽  
Cylinder Diameter ◽  
Overflow Pipe ◽  
New Formula

Irrigation needs have been estimated, in the last few years, by a method referred to as the "soil water budget" and based on meteorological factors such as evapotranspiration and rain. In order to eliminate the needs for daily recording and calculation of records, a new formula has been derived. An instrument capable of integrating both evapotranspiration and rain, and made up of an evaporimeter and an integrating cylinder, has been mounted according to it. The cylinder diameter (Dc) is determined by this formula Dc = De √K, when De is the diameter of the evaporimeter and K the ratio between evaporation and potential evapotranspiration of a crop.This instrument was made and tried in 1961. A Wright AP evaporimeter was used. The integrating cylinder, terminated by a funnel to collect rain, is equipped with a scale indicating the soil water deficit and an overflow pipe permitting the evacuation of water in excess of field capacity. The evaporation of a 4-foot sunken tank was taken as the basic value of potential evapotranspiration, since it is considered approximately equivalent to the evapotranspiration of a crop adequately provided with water.This instrument, after some minor corrections, will be an efficient means of predicting irrigation needs. A good correlation was established between this instrument and two other methods of estimating evapotranspiration. Its response to meteorological factors was good.

scholarly journals Integrating MODIS images in a water budget model for dynamic functioning and drought simulation of a Mediterranean forest in Tunisia

2012 ◽  
Vol 9 (5) ◽  
pp. 6251-6284 ◽  
Author(s):  
H. Chakroun ◽  
F. Mouillot ◽  
M. Nouri ◽  
Z. Nasr
Keyword(s):  
Soil Water ◽  
Water Budget ◽  
Regional Scale ◽  
Field Capacity ◽  
Stress Index ◽  
Climatic Data ◽  
Natural Ecosystem ◽  
Stress Monitoring ◽  
Budget Model ◽  
Vegetation Stress

Abstract. The use of remote sensing at different spatio-temporal resolutions is being common during the last decades since sensors offer many inputs to water budget estimation. Various water balance models use the LAI as a parameter for accounting water interception, evapotranspiration, runoff and available ground water. The objective of the present work is to improve vegetation stress monitoring at regional scale for a natural forested ecosystem. LAI-MODIS and spatialized vegetation, soil and climatic data have been integrated in a water budget model that simulates evapotranspiration and soil water content at daily step. We first explore LAI-MODIS in the specific context of Mediterranean natural ecosystem. Results showed that despite coarse resolution of LAI-MODIS product (1 km), it was possible to discriminate evergreen and coniferous vegetation and that LAI values are influenced by underlying soil capacity of water holding. The dynamic of vegetation has been integrated into the water budget model by weekly varying LAI-MODIS. Results of simulations were analysed in terms of actual evapotranspoiration, deficit of soil water to field capacity and vegetation stress index based on actual and potential evapotranspiration. Comparing dynamic LAI variation, afforded by MODIS, to a hypothetic constant LAI all over the year correspond to 30% of fAPAR increase. A sensitivity analysis of simulation outputs to this fAPAR variation reveals that increase of both deficit of soil water to field capacity and stress index are respectively 18% and 27%, (in terms of RMSE, these variations are respectively 1258 mm yr−1 and 11 days yr−1). These results are consistent with previous studies led at local scale showing that LAI increase is accompanied by stress conditions increase in Mediterranean natural ecosystems. In this study, we also showed that spatial modelisation of drought conditions based on water budget simulations is an adequate tool for quantifying expositions of different species to stress and for analysing most influent factors on ecosystem vulnerability to drought.

Estimating actual evapotranspiration using water budget and soil water reduction methods

2006 ◽  
Vol 86 (4) ◽  
pp. 757-766 ◽  
Author(s):  
David S Chanasyk ◽  
Emmanuel Mapfumo ◽  
Crystal L.A. Chaikowsky
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Water Budget ◽  
Potential Evapotranspiration ◽  
Field Capacity ◽  
Actual Evapotranspiration ◽  
Reclaimed Land ◽  
Water Reduction ◽  
Global Circulation Models ◽  
Reduction Methods

Studies on estimation of actual evapotranspiration on disturbed lands are scarce and yet such data are essential in hydrologic modeling. Our study compared the variability of estimates of actual evapotranspiration (AET) from a reclaimed site in northern Alberta using the simplified water budget (WB) and soil water reduction (SWR) methods. The AET estimates from the simplified water budget equation (AET1) required field soil water content, precipitation and runoff. The AET estimates from the soil water reduction method (AET2) required daily potential evapotranspiration (PET), field capacity (FC) water content, minimum field-measured water content, and field water content. Soil water was measured using neutron moisture gauge every 2 wk during the growing season for a 2-yr period. The average AET1 and AET2 estimates for 2001 were 1.9 and 1.4 mm per day, respectively, where as those for 2002 were 2.1 and 1.2 mm per day, respectively. The paired t-tests to compare AET1 against AET2 indicated significance differences (P ≤ 0.05) in 5 out of 11 measurement dates, especially during high rainfall periods. Overall AET2 estimates were more variable than AET1 estimates. Therefore, the larger variability of AET2 estimates imply less reliability of spatially averaged AET2 estimates for use in regional and global circulation models. Key words: Extractable water, reclaimed land, water budget, soil water reduction, potential evapotranspiration

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