Deficit irrigation is an optimum technique for producing products under drought stress conditions. The superabsorbent hydrogel is a hydrophilic polymer with cross-linked 3-D hydrophilic nets that can absorb and retain effective amounts of water and aquatic liquids. The objective of this study was to assess the superabsorbent polymer effect on water use efficiency (WUE) and grain yield of Vigna unguiculata L. under drought stress conditions. The experimental treatments included: Treatment I1S0, including 100% ETc demand as irrigation amount and with 0.0 g SAP (I1:100%; S0: without SAP); treatment I2S1, including 75% ETc demand as irrigation amount and with 7.0 g Super-AB-A300 polymer for plant (I2: 75%; S1: 7 g SAP); treatment I3S2, including 55% ETc demand as irrigation amount and with 14.0 g Super-AB-A300 polymer for plant (I3: 55%; S2: 14 g SAP). A drip irrigation system performed irrigation. According to the results, the soil treated with superabsorbent polymer, in mild deficit irrigation treatment (I2S1), made it possible to obtain the same grain yield as the complete irrigation treatment (I1S0) and there was no significant difference between them. Besides, IWUE was conversely depended on the entire water requirement all along the growing cycle, and for higher IWUE, the water would be decreased under the irrigation demand for the maximum grain yield. Thus, the mix of mild deficit irrigation and superabsorbent polymer (I2S1), that leads to increase the plant water productivity (AWP), was an acceptable policy to optimize cowpea grain yield and water utilization.

This paper offers an exploratory microeconomic analysis of water use in the cultivation of almonds orchards when water is considered as the limiting factor. When a crop is subjected to water limitation, the microeconomic principles behind irrigation decisions are based upon the water-yield relationship. The analysis is applied to an estimated water-yield response function for irrigated almond trees in Spain; our research focuses on determining the optimal irrigation dose when deficit irrigation is applied, as is usual in the context of water limitation. The situation in Spain is compared to that of other countries where water rights are less constrained. The economic analysis of the water production function is crucial, since it determines the farmers’ income and helps them make appropriate management decisions, such as the allocation of limited water to crops and the extension of the irrigated area. Furthermore, public institutions need this basic information in order to assign water allocation in the context of increasing demand and limited resources. | Este artículo ofrece un análisis microeconómico del uso del agua en el cultivo del almendro cuando el agua se considera el factor limitante. Cuando un cultivo está sujeto a limitación de agua, los principios microeconómicos detrás de las decisiones de riego se basan en la relación entre rendimiento y riego. El análisis se aplica a una función de respuesta agua-producción estimada para almendros de regadío en España. Nuestra investigación se centra en determinar la dosis óptima de riego cuando se aplica riego deficitario, como es habitual en contexto de escasez de agua. Finalmente, la situación en España se compara con la de otros países donde los derechos de agua están menos restringidos. El análisis económico de la función de producción de agua es crucial, ya que determina los ingresos de los agricultores y los ayuda a tomar decisiones de gestión adecuadas, como la asignación de agua limitada a los cultivos y la extensión del área regada. Además, las instituciones públicas necesitan esta información para garantizar una adecuada asignación de los recursos hídricos en un contexto de demanda creciente y recursos limitados.

In regions with temperate and humid climate such as Uruguay, irrigation stabilizes and increases the yields of summer crops by supplementing rainfall. Irrigation on demand generates higher water consumption, it affects production system sustainability due to inefficient use of resources and it is environmentally negative (excessive fresh water use and energy for its extraction). It is necessary to evaluate deficit irrigation alternatives that increase the productivity of irrigation water. Therefore, three maximum irrigation depths were evaluated: (T2) 3 mm day-1, (T3) 6 mm day-1, (T4) 9 mm day-1, and (T1) control without irrigation (only receives rainfall), on corn production, in order to define more efficient irrigation strategies. Results indicate responses to different levels of deficit irrigation. When rainfall was higher than average, its poor distribution during the crop cycle generated water deficit at specific times, affecting yield. T1 and T2 did not cover etc during the Critical Period and grain filling, which caused lower yields. The yields in T3 and T4 were higher and on the three-year average they were significantly different. T3 did not always cover etc, but the soil reserve and rainfall contributed to cover it, saving almost 20% of irrigation water compared to T4. However, the water productivity indicators (wue, iwue) show that T4 is the best irrigation strategy, although it uses less rainfall and soil water reserve. | En regiones de clima templado y húmedo como Uruguay el riego estabiliza y aumenta los rendimientos de los cultivos estivales, suplementando las precipitaciones. El riego a demanda tiene mayor consumo de agua, afectando la sostenibilidad del sistema de producción por el uso ineficiente de los recursos, y es ambientalmente negativo (uso excesivo de agua dulce y energía para su extracción). Es necesario evaluar alternativas de riego deficitario que aumenten la productividad del agua riego. Para ello se evaluaron tres láminas máximas de reposición: (T2) 3 mm día-1, (T3) 6 mm día-1, (T4) 9 mm día-1, y (T1) testigo sin riego, (solo agua de lluvia), sobre la producción de maíz, para definir estrategias de riego más eficientes. Los resultados indican que existe respuesta a diferentes niveles de riego deficitario. Cuando las precipitaciones fueron superiores al promedio, su mala distribución durante el ciclo del cultivo generó déficit hídrico en momentos puntuales, afectando el rendimiento. El T1 y T2 no cubrieron la etc durante el Periodo Crítico y llenado de grano, causando menores rendimientos. El T3 y T4 dieron rendimientos mayores y en el promedio de tres años fueron diferentes significativamente. El T3 no siempre cubrió la etc, pero la reserva del suelo y las precipitaciones contribuyeron para cubrirlo, ahorrando casi 20 % de agua de riego respecto a T4. Sin embargo, los indicadores de productividad del agua (eua, euar) muestran que T4 es mejor estrategia de riego, aunque realice menor aprovechamiento de las precipitaciones y del agua del suelo. | Em regiões climáticas temperadas e úmidas, como o Uruguai, a irrigação estabiliza e aumenta a produtividade nas culturas de verão, suplementando as chuvas. A irrigação sob demanda gera maior consumo de água, afeta a sustentabilidade dos sistemas de produção devido ao uso ineficiente dos recursos e é ambientalmente negativa (uso excessivo de água doce e energia para sua extração). É necessário avaliar alternativas de irrigação deficitária que aumentem a produtividade da água utilizada na irrigação. Para isso, três lâminas de irrigação máximas foram avaliadas: (T2) 3 mm dia-1, (T3) 6 mm dia-1, (T4) 9 mm dia-1 e (T1) controle sem irrigação, (apenas água da chuva), na produção de milho, para definir estratégias de irrigação mais eficientes. Os resultados indicam que há uma resposta a diferentes níveis de déficit de irrigação. Quando as chuvas eram superiores à média, sua má distribuição durante o ciclo da cultura gerava déficit hídrico em momentos específicos, afetando a produtividade. T1 e T2 não cobriram a ETc durante o período crítico e enchimento de grãos, causando menores rendimentos. T3 e T4 deram rendimentos mais elevados e na média de três anos foram significativamente diferentes. Nem sempre o T3 cobriu a ETc, mas a reserva de solo e a chuva contribuíram para cobri-la, economizando quase 20% da água de irrigação em relação ao T4. No entanto, os indicadores de produtividade da água (EUA, EUAR) mostram que o T4 é a melhor estratégia de irrigação, embora faça menos uso da chuva e da água do solo.

In regions with temperate and humid climate such as Uruguay, irrigation stabilizes and increases the yields of summer crops by supplementing rainfall. Irrigation on demand generates higher water consumption, it affects production system sustainability due to inefficient use of resources and it is environmentally negative (excessive fresh water use and energy for its extraction). It is necessary to evaluate deficit irrigation alternatives that increase the productivity of irrigation water. Therefore, three maximum irrigation depths were evaluated: (T2) 3 mm day-1, (T3) 6 mm day-1, (T4) 9 mm day-1, and (T1) control without irrigation (only receives rainfall), on corn production, in order to define more efficient irrigation strategies. Results indicate responses to different levels of deficit irrigation. When rainfall was higher than average, its poor distribution during the crop cycle generated water deficit at specific times, affecting yield. T1 and T2 did not cover etc during the Critical Period and grain filling, which caused lower yields. The yields in T3 and T4 were higher and on the three-year average they were significantly different. T3 did not always cover etc, but the soil reserve and rainfall contributed to cover it, saving almost 20% of irrigation water compared to T4. However, the water productivity indicators (wue, iwue) show that T4 is the best irrigation strategy, although it uses less rainfall and soil water reserve. | En regiones de clima templado y húmedo como Uruguay el riego estabiliza y aumenta los rendimientos de los cultivos estivales, suplementando las precipitaciones. El riego a demanda tiene mayor consumo de agua, afectando la sostenibilidad del sistema de producción por el uso ineficiente de los recursos, y es ambientalmente negativo (uso excesivo de agua dulce y energía para su extracción). Es necesario evaluar alternativas de riego deficitario que aumenten la productividad del agua riego. Para ello se evaluaron tres láminas máximas de reposición: (T2) 3 mm día-1, (T3) 6 mm día-1, (T4) 9 mm día-1, y (T1) testigo sin riego, (solo agua de lluvia), sobre la producción de maíz, para definir estrategias de riego más eficientes. Los resultados indican que existe respuesta a diferentes niveles de riego deficitario. Cuando las precipitaciones fueron superiores al promedio, su mala distribución durante el ciclo del cultivo generó déficit hídrico en momentos puntuales, afectando el rendimiento. El T1 y T2 no cubrieron la etc durante el Periodo Crítico y llenado de grano, causando menores rendimientos.  El T3 y T4 dieron rendimientos mayores y en el promedio de tres años fueron diferentes significativamente. El T3 no siempre cubrió la etc, pero la reserva del suelo y las precipitaciones contribuyeron para cubrirlo, ahorrando casi 20 % de agua de riego respecto a T4. Sin embargo, los indicadores de productividad del agua (eua, euar) muestran que T4 es mejor estrategia de riego, aunque realice menor aprovechamiento de las precipitaciones y del agua del suelo. | Em regiões climáticas temperadas e úmidas, como o Uruguai, a irrigação estabiliza e aumenta a produtividade nas culturas de verão, suplementando as chuvas. A irrigação sob demanda gera maior consumo de água, afeta a sustentabilidade dos sistemas de produção devido ao uso ineficiente dos recursos e é ambientalmente negativa (uso excessivo de água doce e energia para sua extração). É necessário avaliar alternativas de irrigação deficitária que aumentem a produtividade da água utilizada na irrigação. Para isso, três lâminas de irrigação máximas foram avaliadas: (T2) 3 mm dia-1, (T3) 6 mm dia-1, (T4) 9 mm dia-1 e (T1) controle sem irrigação, (apenas água da chuva), na produção de milho, para definir estratégias de irrigação mais eficientes. Os resultados indicam que há uma resposta a diferentes níveis de déficit de irrigação. Quando as chuvas eram superiores à média, sua má distribuição durante o ciclo da cultura gerava déficit hídrico em momentos específicos, afetando a produtividade. T1 e T2 não cobriram a ETc durante o período crítico e enchimento de grãos, causando menores rendimentos. T3 e T4 deram rendimentos mais elevados e na média de três anos foram significativamente diferentes. Nem sempre o T3 cobriu a ETc, mas a reserva de solo e a chuva contribuíram para cobri-la, economizando quase 20% da água de irrigação em relação ao T4. No entanto, os indicadores de produtividade da água (EUA, EUAR) mostram que o T4 é a melhor estratégia de irrigação, embora faça menos uso da chuva e da água do solo.

La disponibilidad del agua para la agricultura está disminuyendo rápidamente, lo que impone una utilización más eficiente de este recurso. Para lograr el incremento de la productividad del agua es imprescindible el estudio de las funciones agua rendimiento. Utilizando datos de dos experimentos realizados en la Estación de Alquízar en el sur de La Habana (suelo ferralítico rojo) y con ayuda de herramientas de análisis de regresión en este trabajo se calculan las distintas formas de expresión de la función de producción (CWPF), así como la productividad del agua (WP) para el sorgo. El modelo lineal fue el de mejor ajuste para la relación entre el rendimiento del grano de sorgo y la evapotranspiración, con un coeficiente de determinación de 0,81 y una eficiencia del agua evapotranspirada de alrededor de 6 kg de grano de sorgo por cada milímetro adicional de agua. Mientras que la función rendimiento versus agua total es de naturaleza curvilínea y se calcula usando un polinomio de segundo orden. Si se logra satisfacer en más del 80% las necesidades hídricas de este cultivo los rendimientos podrían superar los 4 000 kg/ha. Al relacionar los valores relativos de rendimiento y evapotranspiración se obtuvo una pendiente igual a 0,59, resultado que clasifica al sorgo como un cultivo de respuesta al agua entre débil y media. El factor de respuesta del rendimiento Ky para el sorgo en las condiciones de este estudio resultó igual a 0,62 e inferior al 0,9 reportado en la literatura. Por cada metro cubico de agua consumida y agua total el sorgo produce como promedio 1,15 y 0,73 kg, respectivamente. La productividad máxima se obtuvo con 3620 m³/ha de agua total en la época de invierno. | The study of the crop water production function is an important strategy to increase water productivity. Using a data base of two experiments carried out at the Station located in Alquizar at south of Havana Province (red ferralitic soils), with the help of regression tools, the different expression of the crop water production function and the water productivity (WP) of the sorghum was estimated . The lineal model was better adjustment for the relationship between evapotranspiration and grain yield for sorghum, with a coefficient of determination of 0,81 and an efficiency of 6 kg of sorghum grain for every additional millimeter of water . While the function yield versus total water is of curvilinear nature, using a polynomial of second order is calculated . If it is achieved the goal of satisfying in more than 80% water requirement of this cultivation, yields could overcome 4 000 kg/ha. When relating, relative value yields and evapotranspiration a slope equal to 0,59 was obtained, which classifies as a crop of weak and average response to water . The yield response factor of the sorghum in this study was 0,62 lower than 0,9 reported in the literature . Every cubic meter of consumed and total water used in sorghum produce as average 1,15 and 0,73 kg, respectively. The maximum productivity was obtained with 3620 m³/ha of total water in winter.

[ES] El cambio climático que se observa con el paso de los años plantea restricciones en la utilización de agua y obliga al desarrollo de nuevas formas y técnicas de utilización de los recursos. Los retos más inminentes que debe afrontar la industria vinícola, sobre todo en las regiones áridas y semiáridas, son el aumento de la sequía y la salinidad debido a la mayor evaporación y la disminución de la disponibilidad de agua. Por tanto, el objetivo del trabajo es estudiar el efecto de la utilización de aguas provenientes de la depuración de los vertidos municipales para reducir el déficit hídrico del suelo al que se ven sometidos los viñedos en secano, sobre la composición aromática de la uva en el momento de la vendimia. Para ello se han aplicado diferentes estrategias en cuanto al aporte de agua (secano y riego deficitario). Por otra parte, se ha utilizado agua de buena calidad y agua salina con diferente conductividad eléctrica. Se ha realizado un total de 4 tratamientos de riego con distintas características, un total de 3456 cepas. Los resultados muestran diferencias significativas en cuanto a la concentración de los precursores aromáticos de los diferentes tratamientos, sin observarse efectos negativos con respecto a un tratamiento en específico. Por tanto, en base a los resultados de este estudio sería posible la reutilización de aguas salinas, consolidándose como alternativa sostenible para el riego en la agricultura. | [EN] The climate change observed over the years poses restrictions on the use of water and forces the development of new forms and techniques for using resources. The most imminent challenges the wine industry needs to face, especially in arid and semi-arid regions, are the rise of drought and salinity due to increased evaporation and decreased water availability. Hence, the objective of the work is to study the effect of the use of water coming from the purification of municipal discharges to reduce the water deficit of the soil to which dry vineyards are subjected, on the aromatic composition of the grape in the harvest time. For this, different strategies have been applied in terms of water supply (rainfed and deficit irrigation). In addition to this, good quality water and saline water with different electrical conductivity have been used. A total of 4 irrigation treatments with different characteristics have been carried out, a total of 1152 strains. The results show significant differences regarding the concentration of the aromatic precursors of the different treatments, without observing negative effects with respect to a specific treatment. Therefore, based on the results of this study, it would be possible to reuse saline water, consolidating itself as a sustainable alternative for irrigation in agriculture. | Valero Asensio, M. (2020). Efecto de las características del agua de riego sobre la composición aromática de uvas Monastrell. Universitat Politècnica de València. http://hdl.handle.net/10251/157903

Doutoramento em Engenharia dos Biossistemas - Instituto Superior de Agronomia | Improving crop water productivity requires new approaches to economic modelling, considering alternative irrigation scheduling and irrigation systems performance. The present study aims at applying an economic modelling to water use and productivity in irrigated areas. It intends to determine the potential of irrigation systems at field scale to achieve an efficient water use, giving particular attention to maximizing the beneficial water use and the physical and economic water productivities. Thus several water-saving scenarios were developed taking into account alternative solutions to the irrigation practices adopted at the selected fields. Economic analysis and multicriteria analysis methodologies have been developed, implemented, evaluated, and incorporated in system design models (MIRRIG, PROASPER, DEPIVOT). It was possible to identify the best strategies to achieve improved water productivities using the economic modelling coupled with multicriteria analysis modules. The benefits and costs related to irrigation systems and management, through managed water demand, using deficit irrigation, and through the improvement of irrigation systems performance were also considered. The methodology developed proves to be a useful tool to support decision making at the field level, aiming at the sustainability of agricultural systems.

El estudio de las funciones agua rendimiento y su uso dentro de la planificación del agua es una vía estratégica importante para lograr el incremento de la productividad. Utilizando datos de 25 experimentos realizados en la Estación Experimental del Instituto de Investigaciones de Riego y Drenaje (IIRD) y con ayuda de herramientas de análisis de regresión en este trabajo se calcula l a productividad del agua aplicada por riego (WP I) y agua total (WP T) y el factor de respuesta del rendimiento (Kr) en los cultivos maíz, soya y sorgo para las condiciones de la región occidental de Cuba. En el maíz la WP I fue superior al resto de los cultivos, de 16,43 kg/m³ para un agua aplicada de 266,8 m³, para la soya fue de 2,96 kg/m³ con 600 m³ y el sorgo 4,23 kg/m³ con 800 m³. El intervalo para la productividad del agua total WP T del maíz varió entre 0,86 y 2,9 kg/m³, para la soya entre 0,28 y 0,81 kg/m³, mientras que para el sorgo entre 0,49 y 0,96 kg/m³. La pendiente Kr en la función de producción encontrada para el maíz en el invierno fue de 1,67 y en verano de 2,31, mientras que los valores de Kr calculados para el sorgo en las dos épocas estudiadas se ubicaron en el grupo I. El maíz fue el único cultivo que en las dos épocas la pérdida relativa de rendimiento resultó más que proporcional al déficit hídrico. Para u n déficit hídrico planificado de un 20% en el maíz en invierno se puede esperar una pérdida relativa de rendimiento de un 33,4%, mientras que en verano será de 46,2%. | The study of the crop water production function is an important strategy to increase the water productivity. Using a data base of 25 experiments carried out at the Irrigation and Draining Research Station located in Alquizar at south of Havana Province (red ferralitic soils), and with the help of regression tools, it was estimated the crop water productivity (WP) (based on irrigation water applied and total water) and crop yield response factor (Kr) for corn, soybean and sorghum. The corn, soybean and sorghum WP I was 16,43; 2,96 y 4,23 kg/m³ when were applied 266,8; 600 y 800 m³/ha irrigation water, respectively. The range 0,86 to 2,9 kg/m³ of WP T obtained for maize, was in a wider range than the range reported by FAO for this crop. The soybean WP T varied between 0,28 and 0,81 kg/m³, while sorghum varied between 0,49 and 0,96 kg/m³. Every cubic meter of total water used in maize yield 1,93 kg, while in soybean and sorghum it was 0,49 y 0,68 kg/m³ respectively. The slope (Kr) of the maize water productivity function was 1,67 in winter and 2,31 in summer. Soybean and sorghum showed similar response to water deficit in winter. Maize was the only crop where the relative loss of yield was proportional to deficit irrigation. For a planned irrigation deficit of 20% for maize it will expect a relative loss of 33,4% and 46,2% of yield, in winter and summer respectively.

Doutoramento em Engenharia dos Biossistemas - Instituto Superior de Agronomia | Climatic, hydrologic and soil characteristics were determined for the watersheds of São Domingos and Ribeira Seca, Santiago’s island, Cape Verde. In the following, pedo-transfer functions (PTFs) for the agricultural soils of Santiago’s island were developed and applied for modelling. Several models of irrigation and water balance – WINISAREG, SIMDualKc, MIRRIG and Temez – were combined in terms of application to enable a detailed study of water management in agriculture focusing the study area. The evaluation of net irrigation requirements (NIR) was performed for the nine main crops practiced in the area. NIR were related with estimated water availability. An analysis of irrigation water demand to cope with severe and extreme droughts was performed considering various levels of satisfaction of crop water requirements. Several strategies/scenarios of irrigation were simulated for each of the nine selected crops comparing the field observed irrigation management practices with various improved ones. Attention was paid to yields through comparing the observed crop yields with the estimated potential (maximum) crop yield. This estimation was performed using the Stewart model combined with the Agro-Ecological Zones model. Information and data gathered through the field evaluation of micro-irrigation systems were used to develop improved solutions through the model MIRRIG. Using observed and simulated data on crop yields and irrigation and production costs an economic analysis was performed focusing water productivity and economic water productivity of the considered crops subject to alternative water management strategies. This allowed to assess different deficit irrigation schedules and their economic impacts in terms of farmers revenue and the associated risk relative to droughts. Results have shown that the adoption of the deficit irrigation together with improved micro-irrigation systems can lead to minimizing non-beneficial water uses in irrigation and to consequent water savings. Results also enabled a more realistic perception of the levels of production in relation to restrictions on water availability, particularly aiming at coping with water scarcity and drought.