The increasing population demands a greater quantity of food. In order to satisfy the world’s demand, one of the main challenges worldwide consists of modernizing the current irrigation systems. This research shows an experience carried out in a modernized irrigation module in Central-North Mexico following these objectives: to evaluate the impact of the modernization of the irrigation module, to analyze the agricultural productivity, and to assess a group of parameters related with the agricultural production (system conduction and distribution efficiencies, water productivity, among others) and the water volumes after and before the modernization. After a drought period, a methodology was performed in commercial parcels in 2013 to increase the yield of different crops. Some of the activities were: soil leveling, estimation of the soil properties (field capacity, wilting point, bulk density, pH, and organic matter), optimum fertilization applications, use of a model to scheduling irrigation, measure volumes extracted at the parcel level. With the modernization and the method used, around 1800 and 2000 m³ ha⁻¹ were saved with respect to the initial granted volume by the Comisión Nacional del Agua and increase in the global efficiency was also achieved (from 55% to 85%). All crop yields increased, i.e., for corn from 2.5 kg/m³ to 3.8 kg/m³. The impact of modernization accompanied with an effective operation allowed a significant increase of the crop yield and water productivity. Despite a controlled distribution of water being carried out, future research should contemplate free water demand scenarios and automation irrigation for improving the module operation.

After several decades, the incorporation of desalinated seawater into agricultural areas with scarce water resources has become one of the main water supply strategies. Compared to the several currently available desalination techniques, reverse osmosis (RO) is now the reference technology because it lowers energy uses and production costs. Nevertheless, its main limiting factor lies in the membranes used for this system not efficiently retaining boron, which is a problem because the concentration of this element in seawater is high. For 3 years, the present work analysed the impact of seawater temperature on the kinetic parameters of boron rejection in an RO system to establish their annual behaviour and the existing correlation between both parameters. A comparison was made using the values simulated in the projection software provided by the manufacturer of the membranes. The obtained results indicated a high correlation, and the R² correlation coefficients came very close to the unity. Nonetheless, this correlation lowered with time due to typical membrane ageing and compaction because of the system’s continuous operation. Under the tested working conditions and by applying analysed temperature intervals, it was impossible to reach the 0.3 mg·L⁻¹ boron concentration value that ensures lack of crop toxicity. Thus, incorporating other boron reduction techniques is necessary.

Infiltration estimation is made by tests such as concentric cylinders, which are prone to errors, such as the lateral movement under the ring. Several possibilities have been developed over the last decades to compensate these errors, which are based on physical, electronic, and mathematical principles. In this research, two approaches are proposed to measure the water infiltration rate in a silty loam soil by means of the mass values of a lysimeter weighing under rainfall conditions and different moisture contents. Based on the fact that with the lysimeter it is possible to determine acting soil flows very precisely, then with the help of mass conservation and assuming a downward vertical movement, 12 rain events were analyzed. In addition, it was possible to monitor the behavior of soil moisture and to establish the content at field capacity from the values of the weighing lysimeter, from which both approach are based. The infiltration rate of these events showed a variable rate at the beginning of the rainfall until reaching a maximum, to descend to a stable or basic rate. This basic infiltration rate was 1.49 ± 0.36 mm/h, and this is because soils with fine textures have reported low infiltration capacity. Four empirical or semi-empirical models of infiltration were calibrated with the values obtained with our approaches, showing a better fit with the Horton’s model.

Water use efficiency is essential in semiarid regions of Spain, and it can be achieved through a precise knowledge of the real crop water requirements (CWR). The Food and Agriculture Organization of the United Nations (FAO) offers standardized crop coefficients to establish the CWR. However, these coefficients can change due to different conditions, such as climatic variations and cultivation practices. In this work, the evapotranspiration ($E{T}_{C_{lys}}$) and crop coefficients ($K_{C_{lys}}$) of bell pepper were obtained with a compact removable weighing lysimeter between February and August for two crop seasons (2019 and 2020). $E{T}_{C_{lys}}$ was determined from the water balance, and the $K_{C_{lys}}$ values were determined as the ratio of the crop evapotranspiration, measured on the removable weighing lysimeter, and the reference evapotranspiration. The $K_{C_{lys}}$ average values for the bell pepper in the initial, middle, and final stages were 0.57, 1.06, and 0.80, respectively. $K_C$ regression models were obtained as a function of the fraction thermal units, achieving a maximum correlation of 0.67 ($R^2$). In general, the $K_C$ values obtained in this research work were lower in the initial and in the final stages and larger in the middle stage in comparison with the FAO-56 values and other research works values in semiarid conditions. The bell pepper yield increased by 7.72% in 2019 and by 3.49% in 2020 compared to the yield reported by the Ministry of the Environment and Rural and Marine Areas of the Spanish Government in 2019 and with a minimum water loss through drainage. The results in this work can help farmers to determine the crop water requirements and to improve the system efficiency in semiarid locations with similar conditions to those in the study.

La velocidad de infiltración permite estimar la penetración del agua en el suelo, se puede medir como una lámina en función de la profundidad y el tiempo. Existen algunos métodos para medir el comportamiento de la lámina de agua en el suelo. En esta investigación se empleó un lisímetro compacto desarrollado por el grupo de investigación Ingeniería Agromótica y del Mar de la Universidad Politécnica de Cartagena. Se instaló en una finca con suelo de textura franco- limosa, y se registraron los valores minutales del peso del recipiente de cultivo y del depósito de drenaje. Los resultados obtenidos permitieron conocer la evolución de la velocidad de infiltración a lo largo del tiempo. La máxima velocidad de infiltración fue de 0,093 mm/minuto, en el suelo saturado. Con los datos obtenidos en campo se calibró el modelo empírico de Kostiakov, con un error cuadrático medio de 0,00024. Se concluyó que con el empleo de los nuevos lisímetros de pesada que permiten conocer, en tiempo real, la velocidad de infiltración del agua en suelos saturados, es posible calibrar modelos matemáticos empíricos para su empleo cuando no se dispone de esta nueva tecnología. En el suelo franco-limoso estudiado, el comportamiento fue similar al descrito por Kostiakow, para el cual se obtuvo una ecuación exponencial calibrada. Ávila-Dávila, Laura; Soler-Méndez, Manuel; Madrona-Sánchez, Pablo; Ruiz-Canales, Antonio; Bautista-Capetillo, Carlos Francisco; González-Trinidad, Julian; Molina-Martínez, José Miguel

Los lisímetros de pesada son los equipos más precisos que existen en la actualidad para conocer el consumo de agua de los cultivos. Hasta el momento, estos equipos solo han estado disponibles en centros de investigación, ya que eran muy costosos y requerían de una gran infraestructura. Mediante modelos matemáticos y sensores calibrados a partir de los datos proporcionados por estos equipos, se ha intentado extrapolar los datos para ayudar a los agricultores a estimar las necesidades de agua de sus cultivos, aunque en la mayoría de los casos suelen diferir de las necesidades reales. En los últimos años, se han realizado enormes avances que están permitiendo incorporar esta tecnología en parcelas comerciales. Para ello, ha sido necesario reducir el tamaño de los equipos, además de abaratar enormemente los costes para que se amortice en poco tiempo. La medida del peso se lleva a cabo con células de carga. Cuando se pretende compensar la temperatura, las células de carga emplean cuatro galgas extensiométricas, las cuales se ubican a ambos lados del bloque metálico para conocer su deformación. La deformación producida es proporcional al peso aplicado, la cual se transforma en una señal eléctrica medible, conectando las galgas dentro de un puente de Wheatstone. Los cuatro hilos obtenidos del puente, dos de alimentación y dos de señal de salida, pueden conectarse directamente a un datalogger con suficiente resolución o a un indicador de pesada. El recipiente donde se aloja el cultivo, se apoya sobre 4 células de cargas, lo que implica disponer de: a) varios datalogger, b) un datalogger con multiplexor o c) 4 indicadores de pesada conectados a un datalogger. En los tres casos se realizaría la medida de forma individual y la suma por software. Otra forma de conocer el peso global del cultivo, utilizando un único datalogger o indicador de pesada, es mediante el empleo de un sumador electrónico. En los sumadores electrónicos se conectan todas las células de carga en paralelo y se regulan mediante potenciómetros de precisión. De esta forma conseguimos sumar todos los pesos y utilizar un único canal para la medida global del recipiente de cultivo (RC). Este sistema ha permitido resolver de una forma más económica y con la misma precisión, la medida del peso del RC. Ávila-Dávila, Laura; Soler-Méndez, Manuel; Ruiz-Peñalver, Leandro; Bautista-Capetillo, Carlos F.; Molina-Martínez, José Miguel