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1.
《Field Crops Research》1999,63(2):139-157
A model is presented of growth and partitioning to leaves, stems and roots in herbaceous, vegetative crops in response to atmospheric conditions and water supply. It comprises 12 state variables and 33 parameters (including four functional relationships), all of direct physiological significance. The important characteristic of the model is the simultaneous consideration of crop assimilate and water balances achieved by calculations made at short time steps (1 h or less) in order to capture the physiological responses of crop growth and water use as they respond to diurnal environmental patterns.In the model, root-zone water content decreases with transpiration and soil evaporation, and increases with rainfall, irrigation and deepening of the root zone as the crop develops. Photosynthesis depends upon intercepted radiation and temperature and also on canopy conductance determined from crop water status. Respiration of organs is calculated as separate requirements for maintenance and growth. Transpiration proceeds with photosynthesis but in response to evaporative demand, reducing crop water content, which is in turn replenished from the root zone based on its water content and the root length that explores it. Partitioning of assimilate to leaves, stems, and roots depends upon diurnal oscillations in assimilate supply, temperature, and crop water content within limits set by phenological development. Phenological development, here the initiation and expansion of leaves and the maturity and senescence of canopy and root systems, is determined by temperature. Examples, and trends, of model performance are compared with measured physiological and agronomic responses of sunflower to strategies of irrigation.  相似文献   

2.
Summary

The production of sunflower grains for roasting was investigated in two soil types under different quantities of applied saline and non-saline irrigation water, different irrigation managements, soil salinity due to previous use of saline water or due to a raised water table. It was shown in one experiment, conducted in a loess type soil, that sunflowers extracted water at least to a soil depth of 120 cm, when the available water from the top layers was used up. The crop in this soil consumed all the available soil water from nearly the entire root zone, while in the clay soil limited water was consumed from deep layers, due to the high salinity and lack of aeration.

No decrease in yield was found in the loess soil when 75% of the full amount of water (which was 0.8 of Class A pan evaporation rate) was applied. When only 50% was applied a significant decrease in yield was obtained. In contrast, in the clay soil even 75% of the full amount of water decreased the yield remarkably. Under dry-land conditions approximately 65% of maximum yield was found in the loess soil but only 45% in the clay soil. These differences are all attributed to a shallow active root system in the clay soil. Residual soil salinity from previously use of saline water had no effect on grain production in the loess soil, while saline irrigation water applied during the irrigation season decreased production, but only when water supply was not rate limiting. The combination of saline water and residual soil salinity had a marked effect on the decrease of grain yield under limited irrigation. In both soils a reduction in the amount of water applied per single irrigation and maintaining the entire irrigation period caused a significantly smaller decrease in yield than shortening the irrigation period and applying the full demand.  相似文献   

3.
In sprinkler irrigated fields, irrigation water is intercepted by crop leaves. This water can be separated into several categories depending on its movement. In this study, the categories are defined as crop stem flow water, leaf storage water, and drop water to the soil. Crop stem flow water is especially effective for crop growth because it reaches the soil surface near the root zone. The objective of this study is to develop a method for quantifying crop stem flow water. Field observation is conducted to observe the movement of irrigation water droplets and to quantify the varying amounts of crop stem flow water, leaf storage water, and drop water to the soil. The measurement of the amount of leaf storage water indicates that droplet movement on the leaf changes constantly. To quantify three components of irrigated water, considering the continuous change of droplet movement on the leaf surface, a simulation model is developed. The simulated amounts of crop stem flow water, leaf storage water, drop water to the soil successfully reproduce the observed result, and model accuracy can be verified.  相似文献   

4.
Optimization of irrigation water is an important issue in agricultural production for maximizing the return from the limited water availability. The current study proposes a simulation–optimization framework for developing optimal irrigation schedules for rice crop (Oryza sativa) under water deficit conditions. The framework utilizes a rice crop growth simulation model to identify the critical periods of growth that are highly sensitive to the reduction in final crop yield, and a genetic algorithm based optimizer develops the optimal water allocations during the crop growing period. The model ORYZA2000, which is employed as the crop growth simulation model, is calibrated and validated using field experimental data prior to incorporating in the proposed framework. The proposed framework was applied to a real world case study of a command area in southern India, and it was found that significant improvement in total yield can be achieved by the model compared to other water saving irrigation methods. The results of the study were highly encouraging and suggest that by employing a calibrated crop growth model combined with an optimization algorithm can lead to achieve maximum water use efficiency.  相似文献   

5.
通过对常规垄灌溉、固定隔沟灌溉和交替隔沟灌溉的试验对比,交替隔沟灌溉水量仅为常规沟灌的1/2,有一半左右的地表面处于相对干燥状态,水分渗入率较大,提高了土壤对灌溉水和自然降雨的储存与利用,有利于对有限的水资源进行合理分配和充分利用。运用交替隔沟灌溉技术能提高作物对垄两侧土壤中养料、水分等的利用效率,作物根系进行干湿交替锻炼后,刺激根系生长,提高根系活力,一定程度增强植株抵御干旱的能力,更利于作物健康生长,交替隔沟灌溉是具有较强实用性的大田节水灌溉方法。  相似文献   

6.
Summary

This is a review of water use by the olive tree, in which the most-relevant knowledge from the literature is combined with key results from experiments just finished or currently in progress. We describe the plant characteristics and mechanisms conferring drought tolerance on the olive tree. The root system functionality, hydraulic characteristics of the conductive system, leaf water relations, and transpiration behavior are considered. We explain the most-advanced techniques for optimizing irrigation, based on a more accurate calculation of the crop water needs. The crop responses to deficit irrigation strategies and to the use of wastewater for irrigation are also included.  相似文献   

7.
《Plant Production Science》2013,16(4):403-414
Abstract

Plants growing on soil with insufficient moisture need deep and dense roots to avoid water stress. In crop plants, the production of dry matter during ripening of grains is critically important for grain yield. We postulated that shoot growth would be suppressed but root growth would continue under an insufficient soil moisture condition before heading, while shoot growth would be more vigorous than root growth under a sufficient soil moisture condition. We anticipated that the plants growing under an insufficient soil moisture condition before heading would produce more dry matter and grain under an insufficient soil moisture condition during ripening. In order to examine our hypotheses and to determine the fundamental conditions for improving grain yield and efficient use of irrigated water under limited irrigation, we grew wheat plants (Triticum aestivum L., cv. Ayahikari) in pots (30 cm in diameter, 150 cm in height) with insufficient soil moisture (PD-D pots) or sufficient soil moisture (PW-D pots) for six weeks before heading followed by full irrigation, and then insufficient soil moisture condition during ripening. The growth of shoots was suppressed significantly but that of roots was not before heading in PD-D plants, with a higher resultant ratio of root to shoot than in PW-D plants. The former retained a high leaf water potential and, therefore, were able to produce more dry matter and grain during soil moisture depletion during ripening as compared with the latter plants. We also obtained similar results with field-grown plants.  相似文献   

8.
Abstract

Understanding the major limitations to root growth is very important if we are to maximize water and nutrient use and increase yields. Limitations may be insufficient rooting depth, root diseases, nutrient deficiencies, toxicities and soil hardness. An understanding of these limitations will lead to more precisely identifying traits for which to select and breed. Examples of successfully overcoming limiting factors to improve crop performance by breeding and selection are given for cereal cyst nematodes in wheat, soil acidity and salinity. The importance of altered crop management practices to reduce limitations is also stressed. These have resulted in a more effective and healthier root system, which results in more water use and greater yields. Opportunities to genetically increase the size of the root system in dryland systems where water and nutrients are not all used by the crop are given.  相似文献   

9.
Plant root architecture offers the potential for increasing soil water accessibility, particularly under water-limited conditions. The objectives of this study were to evaluate the root architecture in two genotypes of sorghum (Sorghum bicolor (L.) Moench) differing in root angles and to assess the influence of different deficit irrigation regimes on root architecture. The response of two sorghum genotypes, ‘Early Hegari-Sart’ (EH; steep root angle) and ‘Bk7’ (shallow root angle) to four irrigation treatments was investigated in two replicated outdoor studies using large pots. The results indicated that EH possessed steeper brace and crown root angles, fewer brace roots, greater root biomass, and root length density than Bk7 at deeper soil depths (i.e., 15–30 and 30–45 cm) compared with a shallower depth (i.e., 0–15 cm). Across the soil profile, EH had greater root length density and length of roots of small diameter (<1 mm) than Bk7. Accordingly, EH showed more rapid soil-water capture than Bk7. Different levels of irrigation input greatly affected root architecture. Severe deficit irrigation (25% of full crop transpiration throughout the season) increased the angle and number of crown roots, root biomass, and root length density compared with 75 and 100% of full crop transpiration treatments. Consequently, root system architecture can be effectively manipulated through both genotypic selection and irrigation management to ensure optimal performance under different levels of soil available water.  相似文献   

10.
《Field Crops Research》1995,41(2):109-121
In Senegal, rainfed millet production is influenced by the combination of scarce and unpredictable rains and falling soil fertility. In order to analyse the interaction between the water and fertility factors under conditions of low rainfall, the water use by a millet crop (Pennisetum glaucum L.) was studied under different organic matter input situations. Water balance was evaluated using a model and in situ soil moisture measurements.Application of manure raised the crop water requirements without substantially increasing the water supply of the soil. At the end of the crop cycle, the soil dried faster where manure was applied than without manure. The consequences of this on growth and production were studied: changes in the pattern of evolution of the soil water content induced by manuring limited the depth of root penetration, and promoted post-flowering water constraint that can cancel the positive effect of manure on growth and production. As a result, the use of manure increases the risks taken by the farmer and should therefore be taken into consideration for the analysis of existing cropping systems or the definition of possible new ones.  相似文献   

11.
Summary

Atmospheric carbon dioxide (CO2) concentration has risen from about 270 mmol (CO2) mol?1 (air) (i.e., mole fraction of dry atmospheric air basis) before 1700 to about 370 mmol mol ?1 currently. General Circulation Models (GCM) have predicted a global temperature rise of 2.8 to 5.2°C for a doubling of CO2. This review examines evapotranspiration and water-use efficiency responses of plants to rising CO2 and climatic changes, especially temperature. Doubling of CO2 will decrease leaf stomatal conductance to water vapor about 40%. However, water use by C3 crop plants under field conditions has usually been decreased only 12% or less for two reasons. Firstly, feedbacks in the energy balance of plant foliage cause leaf temperatures to rise as stomatal conductance is decreased. Increases of leaf temperature raise the vapor pressure of water inside the leaf, which increases the leaf-to-air vapor pressure difference. This increased driving force for transpiration offsets in large part the decreased leaf conductance caused by elevated CO2. Secondly, CO2 enrichment tends to cause leaf area to increase more rapidly in many crops. This increased leaf surface area for transpiration also offsets part of the decreased stomatal conductance per unit leaf area on the whole canopy evapotranspiration, but the energy budget feedbacks are more important.

Experiments point to a yield enhancement of 30 to 35% for C3 crops for the direct effects a doubling of CO2 (without ancillary climate change). If temperature rises, this yield enhancement may be greater for vegetative growth but less for seed grain yield. Experiments on both ambient and elevated CO2 treatments in sunlit growth chambers showed that transpiration rates increased 20% when air temperature was changed from 28 to 33 °C and increased 30% when temperature was increased from 28 to 35 °C. Thus, under well-watered conditions, evapotranspiration will increase about 4 to 5% per 1°C rise in temperature.

Crop model predictions of yields of soybean and maize showed a reduction due to temperature increases by two GCM models. Under Southeastern USA conditions, doubling CO2 in the Goddard Institute for Space Studies (GISS) climate change scenario resulted in an 12% increase in yields, but yields decreased 50% in the Geophysical Fluids Dynamics Laboratory (GFDL) climate change scenario. Optimum irrigation for both models gave yield increases of about 10%. These model results illustrate the critical requirement of water for production of crops. Under rainfed conditions, crop yields could suffer tremendously if growing season precipitation is decreased, but yields could increase moderately if growing season precipitation is increased. Under the high growing season rainfall scenario (GISS), irrigation requirements for optimum soil water were increased 22%, but under the low rainfall scenario (GFDL), irrigation requirements were increased 111%.

Without the effects of climate change, rising CO2 will cause an increase in crop water-use efficiency (WUE). Most of the increases in WUE will be due to increases in dry matter, with little or no contribution from decreases in water use per unit land area. Growers could produce higher yields per unit land area with higher total production, or maintain the same total production with less land and less total water use. However, if temperatures rise, transpirational water use will increase, and WUE will decline. Higher temperatures, and especially less rainfall, would raise the irrigation requirements of crops. Competition for water resources from other uses could result in less water available for irrigation.  相似文献   

12.
《Plant Production Science》2013,16(2):182-188
Abstract

No-tillage often affects crop root development due to the higher mechanical impedance to root elongation, resulting in yield reduction under an unfavorable rainfall pattern, such as drought. In this study, we analyzed the changes in water source of wheat and soybean under drought stress in a continuous no-tillage field. Deuterium-labeled irrigation water was applied at different growth stages of crops to analyze their water uptake pattern. Mechanical impedance of the surface soil was 3.5 and 4.4 times higher in the no-tillage than in the conventional tillage under wet and drought conditions, respectively. Root length density and root branching index (the length of lateral roots per unit axile root length) of soybean in the surface soil layer were higher in the no-tillage field. This indicates that the increased branching by the higher mechanical impedance of undisturbed surface soil causes roots to accumulate in the surface soil layer. The deuterium concentration in the xylem sap of both crops was significantly higher in the no-tillage than in the tillage under a drought condition. This indicates that the crops in the no-tillage field depend highly on the newly supplied easily accessible water (irrigation water and/or rainfall) as compared with those in the conventional tillage field under a limited water supply. In conclusion, enhanced surface root growth in the no-tillage condition would result in higher dependence on surface supplied irrigation water than in the conventional tillage under drought.  相似文献   

13.
《Plant Production Science》2013,16(4):355-363
abstract

The practice of intercropping pearl millet with cowpea is widespread among subsistence farmers in northern Namibia. In this region, the scarce and erratic rainfall may enhance competition for the limited soil water between intercropped plants. Trials were conducted on a field of the University of Namibia (on-station) and on a farmer’s field (off-station) to determine the effects of competition between pearl millet and cowpea on the water sources and plant growth of each crop. The deuterium analysis showed that pearl millet, intercropped with cowpea, significantly increased its dependence on the recently supplied labeled irrigation water. Intercropped cowpea also showed an increased trend of the dependence but it was not statistically significant. At the university field, intercropped pearl millet showed higher dependence on the irrigation water than monocropped pearl millet. At the farmer’s field, the dependence of intercropped pearl millet on the irrigation water was low in the pearl millet-dominant zone. In contrast, the dependence on the irrigation water was high in the cowpea-dominant zone, indicating that the dependence on the irrigation water changes according to the size of the pearl millet canopy. The water sources of cowpea did not show a significant difference at either pearl millet-dominant or cowpea-dominant zone, indicating a stable water uptake trend under competitive conditions. Competition with cowpea significantly increased the root-weight density of intercropped pearl millet in the deep soil layers, but decreased that in the shallow layers. The root-weight density of intercropped cowpea, however, was reduced in most of the soil layers. In conclusion, cowpea has a higher ability to acquire existing soil water, forcing pearl millet to develop deep roots and shift to the surface irrigation water.  相似文献   

14.
《Field Crops Research》2004,87(1):59-71
Soil water availability estimation is critical for assessing crop development and performance. During periods of soil water deficits, the capability of crop roots to extract soil water depends on the distribution and depth of its root system. Most water uptake models assume a relationship between root water extraction and root length density (RLD). However, models using RLD are difficult to test and several researchers have questioned the various proposed relationships between RLD and water uptake. A simplified water uptake model that does not use RLD was developed, but as an alternative, uses generalizations from measured soil water content changes to predict root water uptake. The daily incrementing model estimates a maximum water uptake rate by roots limited by soil water content that declines exponentially with the soil water content above the lower limit (LL) i.e., the remaining available soil water. The model assumes that: (i) the roots at a given layer have reached a minimum threshold of root density to extract water at a maximum rate; (ii) the transpiration demand is greater than the total root water uptake; and (iii) the water content at LL can be accurately measured or estimated. A critical constant (K) in the exponential model, representing the fraction of extractable water in a soil layer that can be taken up in 1 day, was found to be 0.096 for several species (cotton, maize, pearl millet, grain sorghum, soybean, sunflower and wheat), and different soil conditions. Values of K smaller than 0.096 were likely caused by root clumping in highly structured (cracking) or compacted soils, where root density was low in deeper soil layers when further downward root growth practically ceased, or by peanut whose K values was 0.064. This new empirical model should help to overcome several of the limitations of current models that rely on the use of measured or predicted RLD.  相似文献   

15.
A water balance model for paddy is developed primarily based on the principle of conservation of mass of soil–water within the root zone. The water balance for paddy is different from that of field crops because paddy requires standing water in the field during most of its growth period. This model requires soil, crop and meteorological data as inputs. This user friendly model was developed using computer programmes C and Visual Basic (VB) 6.0. It simulates various water balance components such as evapotranspiration, deep percolation, surface runoff and depth of irrigation water and ponding depth in the field on a daily basis. For estimation of deep percolation loss, physically based saturated and unsaturated flow processes are incorporated into the model to consider ponding (if there is standing water in the field), saturation (if moisture content of soil is in between field capacity and saturation) and depletion (if moisture content of soil is below field capacity) phases of paddy field. This article presents development of a user friendly water balance model for paddy and also its validation using published data.  相似文献   

16.
Increasing water scarcity has necessitated the development of irrigated rice systems that require less water than the traditional flooded rice. The cultivation of aerobic rice is an effort to save water in response to growing worldwide water scarcity with the pressure to reduce water use and increase water productivity. An accurate estimation of different water balance components at the aerobic rice fields is essential to achieve effective use of limited water supplies. Some field water balance components, such as percolation, capillary rise and evapotranspiration, can not be easily measured; therefore a soil water balance model is required to develop and to test water management strategies. This paper presents results of a study to quantify time varying water balance under a critical soil water tension based irrigation criteria for the cultivation of non-ponded “aerobic rice” fields along the lower parts of the Yellow River. Based on the analysis and integration of existing field information on the hydrologic processes in an aerobic rice field, this paper outlines the general components of the water balance using a conceptual model approach. The time varying water balance is then analyzed using the feedback relations among the hydrologic processes in a commercial dynamic modeling environment, Vensim. The model simulates various water balance components such as actual evapotranspiration, deep percolation, surface runoff, and capillary rise in the aerobic rice field on a daily basis. The model parameters are validated with the observed experimental field data from the Huibei Irrigation Experiment Station, Kaifeng, China. The validated model is used to analyze irrigation application soil water tension trigger under wet, dry and average climate conditions using daily time steps. The scenario analysis show that to conserve scarce water resources during the average climate years the irrigation scheduling criteria can be set as −30 kPa average root zone soil water tension; whereas it can be set at −70 kPa during the dry years, however, the associated yields may reduce. Compared with the flooded lowland rice and other upland crops, with these two alternatives irrigation event triggers, aerobic rice cultivation can lead to significant water savings.  相似文献   

17.
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18.
Rice is the main crop produced in the Senegal River Valley under the semiarid Sahelian climate where water resource management is critical for the resource use sustainability. However, very limited data exit on rice water use and irrigation water requirement in this water scarcity environment under climate change conditions. Understanding crop water requirements is essential for better irrigation practices, scheduling and efficient use of water. The objectives of this study were to estimate crop water use and irrigation water requirement of rice in the Senegal River Valley at Fanaye. Field experiments were conducted during the 2013 hot and dry season and wet season, and 2014 hot and dry season and wet seasons. Three nitrogen fertilizer treatments were applied to rice variety Sahel 108: 60, 120, and 180 kg N ha?1. Rice water use was estimated by the two-step approach. Results indicated that crop actual evapotranspiration (ETa) varied from 632 to 929 mm with the highest ETa obtained during the hot and dry seasons. Irrigation water requirement varied from 863 to 1198 mm per season. Rice grain yield was function of the growing season and varied from 4.1 to 10.7 tons ha?1 and increased with nitrogen fertilizer rate. Rice water use efficiency relative to ETa and irrigation requirements increased with nitrogen fertilizer rate while rice nitrogen use efficiency decreased with the nitrogen fertilizer rates. The results of this study can be used as a guideline for rice water use and irrigation water requirement for the irrigation design projects, consultants, universities, producers, and other operators within rice value chain in the Senegal River Valley.  相似文献   

19.
Organic tobacco consists of a new industrial crop product. Field experiments were conducted to determine the effects of irrigation system and fertilization on the growth (biomass and roots) of organic tobacco plants (Nicotiana tabaccum cv NC 71). The experiment was designed as a split plot design with four replicates, two main plots (drip and sprinkler irrigation) and three sub-plots (vetch as green manure, red clover as green manure and control; without fertilization). Drip irrigation was characterised by lower amount of water applied to the soil. Furthermore the tobacco yield was not affected by the reduced water application and the crops under drip irrigation were higher than those with sprinkler irrigation. Positive effect of green manure in the nicotine content of tobacco leaves was also observed, and that reported for first time under organic system. Equally the higher amount of nitrogen from green fertilization with vetch led to increase of nicotine concentration (0.91% max concentration). Agronomic water use efficiency (WUE) for drip irrigation was always higher than those for sprinkler irrigation. There were no significant differences between the drip and sprinkler irrigation concerning the root biomass. Moreover, green manures increased roots dry weight. Yield of tobacco crop was significantly increased by the green manures, with the lowest yield (1850 kg ha?1) to be found in the control plots. Finally, green manures increased the SPAD values and number of leaves, with most significant impact the time when vetch applied to soil.  相似文献   

20.
《Journal of Crop Improvement》2013,27(1-2):353-386
SUMMARY

Salinity in soil and water is irrevocably associated with irrigated agriculture throughout the world and as a result requires that salt management becomes an integral part of the production system. With careful water management, it is possible to sustain irrigated agriculture in areas with saline soil and saline groundwater with and without subsurface drainage. The results from two field projects conducted in an area with saline soils and saline groundwater demonstrated the type of irrigation systems and management needed to sustain production of moderately salt tolerant and tolerant crops. During the first study at Murrieta farms, yields of cotton and sugar beet were maintained using both saline and non-saline water for irrigation when pre-plant irrigation and rainfall were adequate to maintain soil salinity at a tolerable level. Wheat production was reduced in areas that used saline water for irrigation. Use of saline water containing toxic elements such as boron for irrigation poses a threat to the sustainability of the system. The second study evaluated the management of furrow and subsurface drip irrigation in the presence of shallow saline groundwater. Careful management of the furrow system during pre-plant irrigation and the first irrigation of the growing season was required to prevent waterlogging. It was possible to manage the subsurface drip system to induce significant crop water use from shallow groundwater. Rainfall and pre-plant irrigation were adequate at this site to manage soil salinity.  相似文献   

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