农业高效用水理论研究综述

农业高效用水包括节水灌溉和旱作农业 ,其核心是提高自然降水和灌溉水的利用效率和效益 .农田蒸散的测定方法各有利弊 .FAO先后建议用Penman修正式和Penman Monteith公式计算参考作物蒸散量 .Jensen乘法模型和Blank加法模型在作物水分生产函数研究中得到广泛应用 .土壤适宜含水量和土壤干旱下限指标的最新研究成果 ,为低定额的农业供水提供了土壤物理学的重要依据 .水分亏缺对与产量形成相关的各个生理过程影响的先后顺序为细胞扩张 >气孔运动 >蒸腾运动 >光合作用 >物质运输 .不很严重的干旱反而对物质运输有促进作用 .农田灌溉研究已由传统的充分灌溉 ,转向非充分灌溉、调亏灌溉和控制性分根交替灌溉 .未来农业高效用水理论将在界面、土壤水动力学、生物节水、缺水逆境等方面深入开展研究 .

不同光照条件下作物蒸腾量计算的研究

作物蒸腾量的计算是水资源开发利用和农业生产运筹的关键参数之一 .本文以彭曼 -蒙特斯方程为基础 ,通过引入临界阻力 ,根据实测资料建立冠层阻力和空气动力学阻力比值与临界阻力和空气动力学阻力比值二者之间的函数关系 ,得到一个只需气象参数就能计算作物蒸腾量的简单方法 .文章对该方法进行了理论分析 ,并用实例给予验证 .结果表明 ,该方法在理论上和实践上都是可行的 ,是一个值得研究和发展的新方法 .作物蒸腾量的日变化表明 ,炎热夏季晴天中午遮光处理后作物蒸腾量的增大是可能的

GIS环境下1999～2000年中国东北参考作物蒸散量时空变化特征分析

为了实现农业持续发展和保护生态环境,该文应用Penman-Monteith公式和GIS的空间分析功能,通过建立区域参考作物蒸散量的空间分布模型计算了中国东北地区自20世纪90年代以来参考作物蒸散量的时空变化特征。研究发现,20世纪90年代东北地区5～9月份日平均蒸散量呈逐年增大趋势,并以每年0.04mm的速度递增;其中5、6、7、8、9各月份绝大部分地区日均蒸散量年变化呈增加的趋势,东北平原年增长超过0.05mm,≥0.4mm蒸散地区年平均增长面积为248.73万hm2。5月份和8月份大部分地区日均蒸散量呈减少的趋势,6、7、9月份大部分地区日均蒸散量呈增加的趋势。5月和8月蒸散量的减少以及6月到9月蒸散量的增加都由东北(三江平原)向西南(辽河平原)迁移,并在空间范围上表现出一定的收缩趋势。日均蒸散量≥0.4mm蒸散地区的重心呈有规律的波动,5～9月份平均重心年际波动主要位于呼伦贝尔高原和西辽河平原两个地区,5、6、7、8、9月份重心的波动轨迹基本为由西北—东北—西南地区,空间上也逐渐由较集中变为较分散。

三江源区人工草地蒸散量与气候因子的相关分析

该研究以小型自动气象站观测资料为基础,采用FAO Penman-Monteith方法估算三江源区人工草地参考作物蒸散量,并结合FAO-56推荐的综合作物系数值进行草地实际蒸散量的计算,分析了三江源区人工草地实际蒸散量的变化及其与气象因子的关系。结果表明,草地实际蒸散量的季节变化为单峰曲线,夏季日蒸散量明显大于冬季,在8月中旬达到年度最高值。蒸散与空气温度、太阳辐射和相对湿度均显著相关,但与风速的相关性不显著。各气象因子对人工草地蒸散量影响的大小顺序为:空气温度(T)>太阳辐射(Ra)>空气相对湿度(RH)>风速(u2)。

祁连山北坡草地潜在蒸散量研究

采用FAO推荐的标准化、统一化后的Penman-Monteith公式计算植物生长季节祁连山北坡5种主要类型草地的潜在蒸散量,通过揭示植物生长季蒸散量季节变化特征,分析不同类型草地的蒸散特征以及蒸散量与土壤水分之间的关系.

祁连山北坡草地蒸散量及其与影响因子的关系

【目的】研究祁连山北坡草地蒸散与其环境因子的关系，为该牧区草场的科学经营、草地退化的防治以及区域草地生态环境建设等提供科学依据。【方法】以小型自动气象站（HOBO Weather Station，U．S．A）气象观测资料为基础，采用FAO Penman-Monteith方法估算了祁连山北坡草地参考作物蒸散量（ET_0），并结合FAO-56的推荐值，分析了草地实际蒸散量（ETc）的动态变化，同时模拟研究了相关环境因子对实际蒸散量的影响。【结果】夏季（7和8月）草地的实际蒸散量较大，冬季（12和1月）较小，在7月中旬达到年度最高值，平均为3．40mm／d；按相关系数的高低，环境因子对实际蒸散量的影响表现为空气温度〉空气相对湿度〉土壤含水量（0～40cm）〉太阳辐射〉风速；土壤水分对实际蒸散量的影响表现为土壤深度越大，土壤水分对实际蒸散量的影响越小；太阳辐射量与实际蒸散量呈线性关系。【结论】祁连山北坡草地实际蒸散量的年际变化符合当地环境的变化规律，环境因子对其不同程度的影响表明，在今后的草场管理、退化防止、生态建设中应采取适的措施，以确保草地的良性发展。

Novo método para estimativa da evapotranspiração de referência com base na temperatura do ar.

A região de Jales, localizada no noroeste de São Paulo, é uma importante área produtora de uvas de mesa do Estado, onde predominam pequenas propriedades com mão-de-obra familiar. Em todos os vinhedos da região são empregados sistemas de irrigação, para suprir a deficiência hídrica que ocorre durante o ciclo produtivo da cultura. Para um manejo adequado da irrigação, são necessárias informações sobre a necessidade hídrica da cultura. A evapotranspiração de referência (ETo) é um parâmetro fundamental para a determinação dessa necessidade, sendo desejável que se tenha um método que estime a ETo com boa precisão e a partir de dados meteorológicos fáceis de serem obtidos (VILLA NOVA; PEREIRA, 2006). O método de Penman-Monteith é considerado, atualmente, como padrão para a estimativa de ETo. Para seu uso, entretanto, são necessárias variáveis meteorológicas nem sempre disponíveis, principalmente aos pequenos produtores. Por essa razão, métodos que empregam um menor número de variáveis são também utilizados para estimar a ETo. No presente trabalho foram calculados valores diários de ETo pelo método de Hargreaves original; e por um novo método, em que se emprega a equação de Bristow-Campbell para a estimativa de Rs. Esses valores foram comparados aos obtidos pelo método padrão de Penman-Monteith, nas condições do noroeste paulista.

Operating water balance model for agriculture (OWBA)

p.31-47

Ajuste del cálculo de evapotranspiración del cultivo de crisantemo (Dendrathema x grandiflorum Ramat) en invernadero, para diferentes ciclos

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Irrigation scheduling for Sovereign Coronation grapevine based upon evapotranspiration calculations and crop coefficients /

Several irrigation treatments were evaluated on Sovereign Coronation table grapes at two sites over a 3-year period in the cool humid Niagara Peninsula of Ontario. Trials were conducted in the Hippie (Beamsville, ON) and the Lambert Vineyards (Niagara-on-the-Lake, ON) in 2003 to 2005 with the objective of assessing the usefulness of the modified Penman-Monteith equation to accurately schedule vine irrigation needs. Data (relative humidity, windspeed, solar radiation, and temperature) required to precisely calculate evapotranspiration (ETq) were downloaded from the Ontario Weather Network. One of two ETq values (either 100 or 150%) were used in combination with one of two crop coefficients (Kc; either fixed at 0.75 or 0.2 to 0.8 based upon increasing canopy volume) to calculate the amount of irrigation water required. Five irrigation treatments were: un irrigated control; (lOOET) X Kc =0.75; 150ET X Kc =0.75; lOOET X Kc =0.2-0.8; 150ET X Kc =0.2-0.8. Transpiration, water potential (v|/), and soil moisture data were collected each growing seasons. Yield component data was collected and berries from each treatment were analyzed for soluble solids (Brix), pH, titratable acidity (TA), anthocyanins, methyl anthranilate (MA), and total volatile esters (TVE). Irrigation showed a substantial positive effect on transpiration rate and soil moisture; the control treatment showed consistently lower transpiration and soil moisture over the 3 seasons. Transpiration appeared accurately reflect Sovereign Coronation grapevines water status. Soil moisture also accurately reflected level of irrigation. Moreover, irrigation showed impact of leaf \|/, which was more negative throughout the 3 seasons for vines that were not irrigated. Irrigation had a substantial positive effect on yield (kg/vine) and its various components (clusters/vine, cluster weight, and berries/cluster) in 2003 and 2005. Berry weights were higher under the irrigated treatments at both sites. Berry weight consistently appeared to be the main factor leading to these increased yields, as inconsistent responses were noted for some yield variables. Soluble solids was highest under the ET150 and ET100 treatments both with Kc at 0.75. Both pH and TA were highest under control treatments in 2003 and 2004, but highest under irrigated treatments in 2005. Anthocyanins and phenols were highest under the control treatments in 2003 and 2004, but highest under irrigated treatments in 2005. MA and TVE were highest under the ET150 treatments. Vine and soil water status measurements (soil moisture, leaf \|/, and transpiration) confirmed that irrigation was required for the summers of 2003 and 2005 due to dry weather in those years. They also partially supported the hypothesis that the Penman-Monteith equation is useful for calculating vineyard water needs. Both ET treatments gave clear evidence that irrigation could be effective in reducing water stress and for improving vine performance, yield and fruit composition. Use of properly scheduled irrigation was beneficial for Sovereign Coronation table grapes in the Niagara region. Findings herein should give growers some strong guidehnes on when, how and how much to irrigate their vineyards.

Assessing the influence of irrigation and fertigation on fruit composition, vine performance and wine quality in a cool, humid climate /

A study was devised to evaluate influences of irrigation and fertigation practices on Vitis vinifera and Vitis labruscana grapes in the Niagara Peninsula. A modified FAO Penman- Monteith evapotranspiration formula was used to calculate water budgets and schedule irrigations. Five deficit irrigation treatments (non-irrigated control; deficits imposed postbloom, lag phase, and veraison; fiiU season irrigation) were employed in a Chardonnay vineyard. Transpiration rate (4-7 /xg H20/cmVs) and soil moisture data demonstrated that the control and early deficit treatments were under water stress throughout the season. The fiiU season irrigation treatment showed an 18% (2001) and 19% (2002) increase in yield over control due to increased berry weight. Soluble solids and wine quality were not compromised, and the fiiU season treatment showed similar or higher °Brix than all other treatments. Berry titratable acidity andpH also fell within acceptable levels for all five treatments. Irrigation/fertigation timing trials were conducted on Concord and Niagara vines in 2001- 02. The six Concord treatments consisted of a non-irrigated control, irrigation fi^om Eichhom and Lorenz (EL) stage 12 to harvest, and four fertigation treatments which applied 70 kg/ha urea. The nine Niagara treatments included a non-irrigated control, two irrigated treatments (ceasing at veraison and harvest, respectively) and six fertigation treatments of various durations. Slight yield increases (ca. 10% in Concord; 29% in Niagara) were accompanied by small decreases in soluble solids (1.5°Brix), and methyl anthranilate concentrations. Transpiration rate and soil moisture (1 1.9-16.3%) data suggested that severe water stress was present in these Toledo clay based vineyards.

Comparison of different methods in estimating potential evapotranspiration at Muda Irrigation Scheme of Malaysia

Evapotranspiration (ET) is a complex process in the hydrological cycle that influences the quantity of runoff and thus the irrigation water requirements. Numerous methods have been developed to estimate potential evapotranspiration (PET). Unfortunately, most of the reliable PET methods are parameter rich models and therefore, not feasible for application in data scarce regions. On the other hand, accuracy and reliability of simple PET models vary widely according to regional climate conditions. The objective of the present study was to evaluate the performance of three temperature-based and three radiation-based simple ET methods in estimating historical ET and projecting future ET at Muda Irrigation Scheme at Kedah, Malaysia. The performance was measured by comparing those methods with the parameter intensive Penman-Monteith Method. It was found that radiation based methods gave better performance compared to temperature-based methods in estimation of ET in the study area. Future ET simulated from projected climate data obtained through statistical downscaling technique also showed that radiation-based methods can project closer ET values to that projected by Penman-Monteith Method. It is expected that the study will guide in selecting suitable methods for estimating and projecting ET in accordance to availability of meteorological data.

Estudo micrometeorológico de um cultivo de cana-de-açúcar em Alagoas

Este estudo foi desenvolvido dentro do projeto de pesquisa “Micrometeorologia da Mata Atlântica alagoana (MICROMA)” do Departamento de Meteorologia da Universidade Federal de Alagoas, que busca avaliar modificações no sistema solo-planta-atmosfera provocadas pela substituição da Mata Atlântica pela cultura da cana-de-açúcar, na Zona da Mata alagoana. O objetivo principal do presente estudo foi o ajuste do modelo de Penman-Monteith para o cálculo da evapotranspiração da cultura da cana-de-açúcar, na zona canavieira de Alagoas, a partir de determinações micrometeorológicas pelo método do balanço de energia, em diferentes estádios de desenvolvimento da cultura e em diferentes condições de demanda evaporativa atmosférica. A evapotranspiração foi estimada pelo método de Penman-Monteith e comparada com valores calculados através do balanço de energia, pela razão de Bowen, considerando este como método padrão. Medições micrometeorológicas foram feitas nos anos agrícolas de 1997/98 e 1998/99, em um área de 12,5ha de cultivo contínuo de cana-deaçúcar, cultivar SP 70-1143, sob condições de lavoura comercial, na Fazenda Vila Nova, município de Pilar, Alagoas (9o36´S, 35o53´W, 107m de altitude). Durante o período experimental, foram tomadas amostras quinzenais para determinar altura do dossel, comprimento de colmo, índice de área foliar e acúmulo de matéria seca (este apenas em 1998/99). Os parâmetros aerodinâmicos da cultura zo (comprimento de rugosidade) e d (deslocamento do plano zero) foram determinados a partir de perfis de vento, em condições de atmosfera neutra, e relacionados com a altura do dossel. Foram ajustados modelos para estimar o índice de área foliar e a altura do dossel da cultura em função do comprimento do colmo. O fracionamento do saldo de radiação no chamado “período potencial”, sem deficiência hídrica e com a cultura cobrindo completamente o solo, foi de 78% para o fluxo de calor latente de evaporação, 21% para o fluxo de calor sensível na atmosfera e aproximadamente 0,1% para o luxo de calor no solo. A estimativas pelo método de Penman-Monteith se ajustaram ao valores calculados pelo método do balanço de energia, tanto para médias qüinqüidiais (r = 0,93) como para valores diários (r = 0,91). Assim, dados confiáveis de evapotranspiração da cultura de cana-de-açúcar podem ser obtidos pelo método de Penman-Monteith ajustado neste trabalho, para a zona canavieira de Alagoas, em períodos sem deficiência hídrica e com cobertura completa do solo. O uso deste método apresenta a vantagem prática de requerer apenas dados meteorológicos, medidos em apenas um nível, em estações meteorológicas convencionais.

Coeficiente do tanque Classe A obtido por diferentes métodos em ambiente protegido e no campo

There are several methods for determining the Class-A pan coefficient (Kp) to estimate the reference evapotranspiration (ETo), which is of great importance to water management in agriculture. Most of these methods take into account the wind speed, relative humidity and the fetch area. This study was done in region of Botucatu, SP, in greenhouse and field in the months of July-August (dry) and September-October (rainy), used the methods of Doorenbos e Pruitt (1977), Cuenca (1989), Snyder (1992), Pereira et al. (1995), Allen et al. (1998) and correlation between ETo determined by Penman-Monteith (EToPM) and evaporation of the Class-A pan (ECA). The EToPM was used as standard for the correlations between the ETo determined by the Class-A pan (EToTCA) obtained by different methods of Kp. The Kp in greenhouse ranged between 0.51 and 0.85, and in the field from 0.33 to 0.85. The methods of Allen et al. (1998) and Snyder (1992) are the most recommended for dry months in greenhouse and rainy months the correlation between the ECA and EToPM e Cuenca (1989). In the field condition, the methods of Allen et al. (1998) and of correlation between the ECA and EToPM for dry months, and for rainy months of Allen et al. (1998) and Cuenca (1989). The method of Allen et al. (1998) was the most efficient, regardless of the environment and of months analyzed. The fixed value of Kp should only be used when it is not possible to determine from its more sophisticated methods.

Estimativa da evapotranspiração espacial em uma região semiárida utilizando sensoriamento remoto

With the need to deploy management and monitoring systems of natural resources in areas susceptible to environmental degradation, as is the case of semiarid regions, several works have been developed in order to find effective models and technically and economically viable. Therefore, this study aimed to estimate the daily actual evapotranspiration (ETr) through the application of the Surface Energy Balance Algorithm for Land (SEBAL), from remote sensing products, in a semiarid region, Seridó of the Rio Grande do Norte, and do the validation of these estimates using ETr values obtained by the Penman-Monteith (standard method of the Food and Agriculture Organization-FAO). The SEBAL is based on energy balance method, which allows obtaining the vertical latent heat flux (LE) with orbital images and, consequently, of the evapotranspiration through the difference of flows, also vertical, of heat in the soil (G), sensitive heat (H) and radiation balance (Rn). The study area includes the surrounding areas of the Dourado reservoir, located in the Currais Novos/RN city. For the implementation of the algorithm were used five images TM/Landsat-5. The work was divided in three chapters in order to facilitate a better discussion of each part of the SEBAL processing, distributed as follows: first chapter addressing the spatio-temporal variability of the biophysical variables; second chapter dealing with spatio-temporal distribution of instant and daily radiation balance; and the third chapter discussing the heart of the work, the daily actual evapotranspiration estimation and the validation than to the study area