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  • 1
    Electronic Resource
    Electronic Resource
    Irrigation for crops in a sub-humid environment (1981)
    Springer
    Irrigation science 2 (1981), S. 103-111 
    Details
    ISSN: 1432-1319
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In this paper the soil water balance model developed and tested in Part III (Mason and Smith, 1980) for soybeans grown in the variable rainfall environment of the Namoi Valley of New South Wales was used to investigate the potential advantages of a computer-based system of irrigation scheduling. The advantages were evaluated using historical rainfall data for the 25 seasons from 1953/54 to 1977/78. The effects on irrigation efficiency of soil water holding capacity, the allowable soil water deficit prior to irrigation, and ordering irrigation water in advance were evaluated with the model. Reducing the allowed deficit prior to irrigation by 20% compared to the recommended level increased the number of irrigations by an average of 2.8 per year and irrigation requirements by 0.73 X 103 m3 ha−1. The need to order water 6 days in advance because of delays in delivery also increased requirements by 1.46 X 103 m3 ha−1 due to a reduced ability to utilize natural rainfall. Average farm irrigation efficiencies calculated from actual pumping records were found to be low by world standards for the 3-year period 1975/76 to 1977/78. It was concluded that if increased production per unit of water became a high priority in the Namoi Valley, then irrigation efficiency for the three year period discussed could have been increased from 35 to 47%, a saving of 1.3 X 103 m3 ha−1 year−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00270753
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  • 2
    Electronic Resource
    Electronic Resource
    Irrigation for crops in a sub-humid environment (1981)
    Springer
    Irrigation science 2 (1981), S. 89-101 
    Details
    ISSN: 1432-1319
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A soil water use model was linked with a model of soybean growth and yield to simulate soybean production in an area of New South Wales, Australia. The model was developed and tested against results from a 3-year soybean irrigation experiment. Good agreement was obtained between measured and predicted water use and yield for two soybean cultivars (Ruse and Bragg). In the test region summer rainfall averages 300 mm but is highly variable. Therefore the model was used to simulate soybean production using 25 years of historic rainfall data to examine the amount of irrigation water necessary to produce high yields while using both irrigation water and rainfall efficiently. It was found that to obtain high yields for the 25 years, an average of 4.7 crop irrigations were required, using 4.04 X 103 m3 ha−1 of irrigation water. Because of variations in rainfall the number of crop irrigations varied between years from 2 to 6 and the amount of irrigation water required to supplement natural rainfall varied from 1.63 to 5.14 X 103 m3 ha−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00270752
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  • 3
    Electronic Resource
    Electronic Resource
    Irrigation scheduling of cotton in a climate with uncertain rainfall (1981)
    Springer
    Irrigation science 2 (1981), S. 127-140 
    Details
    ISSN: 1432-1319
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary An investigation was made of the irrigation requirements of cotton grown in a sub-humid environment with significant but highly variable rainfall. In the first year of the study, no additional yield benefits accrued to subsequent irrigations following a pre-emergent irrigation due to above average rainfall (550 mm) throughout the growing season. In the second year a similar rainfall amount (502 mm) fell but significant yield increases to irrigation resulted due to the uneven distribution of the rainfall. The main effect was associated with later rains which influenced the number of bolls set. The maximum amount of water extracted by cotton from a deep grey cracking clay was 178 mm. It was found that 70% of this amount could be depleted before irrigation without loss of yield. Crop evapotranspiration varied from 607 mm with no irrigation after emergence to 775 mm following three irrigations. Irrigation was associated with significant losses from rainfall runoff. Too frequent irrigation creates a risk that soil will be too wet to permit utilisation of natural rainfall. Therefore, the use of soil water information to maximise the interval between irrigation is proposed as a necessary basis for efficient irrigation management.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00257975
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of soil type on soybean crop water use in weighing lysimeters (1990)
    Springer
    Irrigation science 11 (1990), S. 69-75 
    Details
    ISSN: 1432-1319
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Accurate estimation of crop evaporation from a range of soil types is fundamental to the continued improvement of irrigation management. In this experiment soybean crop evaporation was measured using two weighing lysimeters, one with an undisturbed block of Hanwood loam (L1), the other with undisturbed Mundiwa clay loam (L2). Although both soils have clay profiles the Hanwood loam was much more freely draining. A fresh water-table (EC = 0.01 S m-1) was maintained 1 m below the soil surface of each lysimeter after 18 days from sowing (DFS). The crop (var. Chaffey) was sown on 18 November 1985 both in and around the lysimeters and was harvested 136 days later. Early crop growth was slower in L2 but growth stages after 60 DFS were similar to L1. Estimated leaf area indices exceeded 3 about 51 and 56 DFS for L1 and L2 respectively and were both greater than 9 at 90 DFS. The crop was well watered until at least 110 DFS. However daily rates of evaporation (E) from L1 noticeably exceeded those of L2 beginning around 50 DFS and increased to 30% greater for the period 70 to 115 DFS. This difference was not due to incorrect calibration. Plant water status measurements were generally similar although covered leaf water potential and foliage temperature values indicated that plants on L1 were less well hydrated than on L2. The causes of the E difference are not known, but it was observed that plants in L2 were about 0.1 m shorter than the surrounding plants which were similar in stature to those in L1. It was speculated that this difference in height created a shelter effect which reduced the net radiant energy absorbed by the canopy at low sun angles and reduced the wind speed controlling the turbulent exchange of water vapour. This study highlights the lack of under-standing that exists about the effect that small discontinuities in crop height can have on the spatial variability of evaporation within crops.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00188442
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  • 5
    Electronic Resource
    Electronic Resource
    Alternative models for predicting the foliage—Air temperature difference of well irrigated wheat under variable meteorological conditions. I. Derivation of parameters II. Accuracy of predictions (1986)
    Springer
    Irrigation science 7 (1986), S. 225-236 
    Details
    ISSN: 1432-1319
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary One means of using infrared measurements of foliage temperature (T f ) for scheduling irrigations requires the use of meteorological data to predict the foliage-air temperature difference for a comparable well-watered crop (T f * − T a ). To determine the best method for making this prediction, parameters for models of increasing complexity for predicting (T f * − T a ) were derived for wheat using two sets of field data collected in 1982 and 1983. The simplest model with vapor pressure deficit (VPD) as the sole predictor accounted for 64% of observed variance in (T f * − T a ). The next model with both VPD and net radiation (R n ) as predictors accounted for 74%. The most complex model predicted (T f * − T a ) from the crop energy balance. In addition to VPD and R n it included parameters for the effects of air temperature (T a ), aerodynamic resistance (r a ) and the canopy resistance of a well-watered crop (r cp ) and accounted for 70% of the variance. Accuracy of these alternative models was tested against an independent set of field data collected in 1984. The single variable model with VPD as sole predictor accounted for 17% of the variance in observed values of (T f * − T a ). This increased to 47% when the effect of R n was included by using the two variable model and was increased further to 65% when the additional variables of T a , r a and r cp were included by use of the energy balance model. When the complexity of the model was measured by its number of variables there was a close relationship between complexity and the accuracy of the predictions. Reasons for the residual variability are discussed. The need for improved instrumentation for meteorological measurements was indicated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00270432
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  • 6
    Electronic Resource
    Electronic Resource
    The effect of soil surface temperature on the crop water stress index (1991)
    Springer
    Irrigation science 12 (1991), S. 37-43 
    Details
    ISSN: 1432-1319
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A coupled soil-vegetation energy balance model which treats the canopy foliage as one layer and the soil surface as another layer was validated againt a set of field data and compared with a single-layer model of a vegetation canopy. The two-layer model was used to predict the effect of increases in soil surface temperature (T s ) due to the drying of the soil surface, on the vegetation temperature (T v ). In the absence of any change in stomatal resistance the impact of soil surface drying on the Crop Water Stress Index (CSWI) calculated from T v was predicted. Field data came from a wheat crop growing on a frequently irrigated plot (W) and a plot left un watered (D) until the soil water depletion reached 100 mm. Vegetation and soil surface temperatures were measured by infrared thermometers from tillering to physiological maturity, with meteorological variables recorded simultaneously. Stomatal resistances were measured with a diffusion porometer intensively over five days when the leaf area index was between 5 and 8. The T v predicted by the single-layer and the two-layer models accounted for 87% and 88% of the variance of measured values respectively, and both regression lines were close to the 1∶1 relationship. Study of the effect of T s on the CWSI with the two-layer model indicated that the CWSI was sensitive to changes in T s . The overestimation of crop water stress calculated from the CWSI was predicted to be greater at low leaf area indices and high levels of stomatal resistance. The implications for this bias when using the CWSI for irrigation scheduling are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00190707
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  • 7
    Electronic Resource
    Electronic Resource
    Irrigation for crops in a sub-humid environment (1980)
    Springer
    Irrigation science 2 (1980), S. 13-22 
    Details
    ISSN: 1432-1319
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The water use of two soybean cultivars (Bragg and Ruse) was measured for three seasons for a range of irrigation treatments. The seasonal totals of plant and soil evaporation ranged from 450 to 750 mm or from 36 to 64% of class A pan evaporation for the same period. Both cultivars extracted approximately 60% of the total extractable soil water in the top 1.2 m of soil before actual evaporation (Ea) dropped below potential evaporation (Eo). Up to this point the ratio between Ea and class A pan evaporation averaged 0.8. Ruse used water at a faster rate than Bragg but Ruse was not as effective in extracting the deep (below 1.0 m) soil water as Bragg. Water use efficiency (kg seed ha−1 mm−1 water) showed a small but general increase with decreasing irrigation water application. Runoff losses varied from zero for non-irrigated Ruse in 1977/78 to 352 mm for frequently-irrigated Bragg in 1976/77, generally increasing with the number of irrigations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00285426
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  • 8
    Electronic Resource
    Electronic Resource
    Influence of season to season variability in weather on irrigation scheduling of wheat: A simulation study (1985)
    Springer
    Irrigation science 6 (1985), S. 241-251 
    Details
    ISSN: 1432-1319
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary There is an increasing demand from farmers for irrigation scheduling advice. Where rainfall and evapotranspiration vary little from year to year, advice on a fixed irrigation schedule based on mean climatic data can be given. However where significant year to year variability in weather occurs a more flexible approach using actual weather data to predict the current level of soil water and mean climatic data to forecast the future rate of depletion and hence irrigation date may be needed. A technique for deciding the most appropriate scheduling approach was tested by using a simple model of crop growth combined with a soil water balance model to simulate year to year variability in scheduling advice. This technique was applied to irrigated wheat using a set of climatic data from 1968 to 1978 for Griffith in the Murrumbidgee Irrigation Area of New South Wales, Australia. A typical sowing date in early June was used and simulated irrigations were scheduled at an allowable soil water depletion (ASWD) of 62 mm for maximum yield and 93 mm for 80% of maximum. The analysis predicted that weather variability between years would cause the number of irrigations to vary from 2 to 7 for ASWD=62 mm and 1 to 4 for ASWD=93 mm. The interval between irrigations varied from 12 to 30 days, for ASWD=62 mm and from 16 to 28 days, for ASWD=93 mm. The first irrigation occurred between 76 and 131 days from sowing for ASWD=62 mm and from 100 to 140 days from sowing for ASWD=93 mm. The date of the last irrigation was similarly variable. This high degree of variability in the times and frequency of irrigations indicated that in south-eastern Australia accurate irrigation scheduling advice can only be given by using a flexible model using both actual and mean climatic data. A fixed schedule based on mean climatic data would lead to an inefficient use of water caused by the mistiming of irrigations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00262469
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  • 9
    Electronic Resource
    Electronic Resource
    Irrigation scheduling of cotton in a climate with uncertain rainfall (1981)
    Springer
    Irrigation science 2 (1981), S. 141-154 
    Details
    ISSN: 1432-1319
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00257976
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  • 10
    Electronic Resource
    Electronic Resource
    Physiological responses of cotton to a single waterlogging at high and low N-levels (1987)
    Springer
    Plant and soil 102 (1987), S. 161-170 
    Details
    ISSN: 1573-5036
    Keywords: aeration ; flooding ; Gossypium hirsutum L. ; root zone ; soil oxygen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Surface-irrigated cotton (Gossypium hirsutum L.) grown on slowly draining clay soil is subjected to short-term periods of waterlogging at each irrigation which generally results in reduced productivity. The sequence of above- and below-ground plant responses to transient waterlogging and the role of N availability in modifying the immediate responses were studied. Lysimeters of Marah clay loam (a Natrustalf) were instrumented to monitor soil and plant responses to a 7-day waterlogging event beginning 67 days after sowing. Cotton (‘Deltapine 61’) plants (8 per lysimeter) were grown with two levels of added N (300 kg ha−1 and 30 kg ha−1) and two irrigation treatments (flooded and control). Measured soil-O2 levels decreased rapidly upon surface flooding because water displaced air and root zone respiration consumed O2. The rate of O2 consumption was 2.7 times greater in the high-N treatment than the low-N treatment. This difference was associated with a 1.8 fold difference in numbers of observed roots. Root growth was only slightly affected by flooding. Leaf growth decreased by 28%, foliage temperature increased 2.3% and apparent photosynthesis decreased by 16%. It is suggested that flooding reduced photosynthetic activity within 2 days while other stress symptoms became apparent after about 6 days. Although this stress was reflected in a trend for decreased plant productivity, the effect of flooding on boll dry mass at harvest was not significant at the level of replication used. The single waterlogging did not cause yield reductions comparable to those observed elsewhere when several waterlogging events were imposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02370698
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