Irrigation Application Depths Research Articles

Modeling the Impact of Deficit Irrigation on Corn Production

Deficit irrigation or intentional under-irrigation offers the potential for sustainable water resources management. The DSSAT CERES-Maize and AquaCrop models were coupled to simulate the effects of deficit irrigation on corn yield and water productivity. The models were calibrated and validated using observed values of crop and biomass yield under 40%, 50%, 60%, 70%, and 80% depletion of the available soil water. Model simulation results showed that a 15% level of deficit irrigation results in maximum yield while a 60% level of deficit irrigation leads to maximum water productivity. Results suggest that it is not necessary to use large amounts of water in order to obtain high crop yield. The net irrigation application depths ranged from 60 mm to 134 mm, with a depth of 77 mm as optimum under 60% deficit irrigation when applied at the start of tasseling to grain filling. This study demonstrated the applicability of deficit irrigation as a water-saving management strategy for corn production systems. Crop models such as DSSAT CERES-Maize and AquaCrop proved to be viable tools to support decision making in corn production systems in the Philippines, especially when employing deficit irrigation.

How Surface Irrigation Contributes to Climate Change Resilience—A Case Study of Practices in Mexico

Climate change has brought increased temperatures and decreased rainfall on a global scale; however, population growth requires greater volumes of water and food each year that must be supplied in one way or another. In Mexico, application efficiencies in gravity irrigation are below 50%. Although in recent years the decision has been made to change to pressurized irrigation systems to increase the efficiency of water use, border or furrow irrigation is still the most widely used in agriculture. In this work, we show that with a methodology developed and applied in these systems, application efficiencies greater than 90% were obtained, while the Water Use Efficiency (WUE) increased by 27, 38 and 47% for the three crops where it was applied: sorghum, barley, and corn, respectively. Irrigation times per hectare and applied irrigation depths decreased by more than 30%, representing increased irrigation efficiencies and WUE. Finally, the water savings obtained can mitigate water scarcity in cities.

Forecasting of applied irrigation depths at farm level for energy tariff periods using Coactive neuro-genetic fuzzy system

Nowadays, water scarcity and the increase in energy demand and their associated costs in pressurized irrigation systems are causing serious challenges. In addition, most of these pressurized irrigation systems has been designed to be operated on-demand where irrigation water is continuously available to farmers complexing the daily decision-making process of the water user association’ managers. Know in advance how much water will be applied by each farmer and its distribution during the day would facilitate the management of the system and would help to optimize the water use and energy costs. In this work, a new hybrid methodology (CANGENFIS) combining Multiple input -Multiple output, fuzzy logic, artificial neural networks and multiobjective genetic algorithms was developed to model farmer behaviour and short-term forecasting the distribution by tariff period of the irrigation depth applied at farm level. CANGENFIS which was developed in Matlab was applied to a real water user association located in Southwest Spain. Three optimal models for the main crops in the water user association were obtained. The average for all tariff periods of the representability (R2) and accuracy of the forecasts (standard error prediction, SEP) were 0.70, 0.76% and 0.85% and 19.9%, 22.9% and 19.5%, for rice, maize and tomato crops models, respectively.

DEVELOPMENT OF A LOW-COST OPEN-SOURCE PLATFORM CONNECTED TO THE INTERNET FOR ACQUISITION OF ENVIRONMENTAL PARAMETERS AND SOIL MOISTURE

The development of the Internet and the technologies associated with it has allowed disseminating and cheapening of communication equipment, prototyping services, electronic sensors, and all types of devices. Agriculture has benefited from these technological advances to boost its productivity and profitability. This study presents the development of a data acquisition and device control platform to obtain, in real-time and remotely, information from the field for decision-making and process automation. All electronic components are low-cost and “open hardware”, and the software is “open-source”. The developed platform was validated during a development cycle of two lettuce varieties (Japanese and crisp), in which the soil water matric potential was monitored at two depths (10 and 25 cm), while solar irradiation, air temperature, and soil temperature were evaluated only to monitor the cycle. The platform automatically and satisfactorily controlled the applied irrigation depths using only the data of matric potential by activating a solenoid valve and made the information from the sensors available on the ThingSpeak Internet of Things (IoT) platform.

Simulating the effects of agricultural production practices on water conservation and crop yields using an improved SWAT model in the Texas High Plains, USA

A calibrated SWAT model equipped with an improved auto-irrigation function was used to evaluate the impacts of agricultural production practices on water balances and crop yields of corn, sorghum, and winter wheat for the Palo Duro watershed located in the Texas High Plains (THP). Fourteen scenarios were simulated including alternative irrigation application depths of 12.7 mm and 38.1 mm for irrigated corn, sorghum, and wheat and with different planting dates for irrigated corn, sorghum, wheat, and dryland wheat. Results indicated the greater irrigation depth (38.1 mm) led to reductions in seasonal irrigation requirements and crop evapotranspiration (ETc) when compared to the baseline scenarios using an irrigation depth of 25.4 mm for corn, sorghum, and wheat. However, soil water content, surface runoff, and percolation were increased. The opposite was observed for simulations of the same hydrologic variables but with an irrigation depth of 12.7 mm. Crop yields associated with the alternative irrigation depths were similar to those achieved with the baseline. Delayed planting of corn and sorghum resulted in the decrease of all the studied hydrologic parameters relative to the baseline. By contrast, the early planting scenarios showed the increase in those variables generally. Simulated corn yields were relatively stable, but a 3.7% reduction in irrigated sorghum yield was found with late planting. Notably, the early planting of wheat resulted in a clear increase in both irrigated and dryland yields of 11.2% and 13.5%, respectively. However, the yields of irrigated and dryland wheat were reduced by 28.8% and 2.7%, respectively, for the late planting. These findings suggest the greater irrigation application depth is promising for maintaining crop yields and reducing groundwater use from the Ogallala Aquifer. Also, the late planting of corn may benefit water conservation. Nevertheless, the early planting of wheat might be warranted to enhance yield in the THP.

IrrigaSys: A web-based irrigation decision support system based on open source data and technology

IrrigaSys is a decision support system (DSS) for irrigation water management based on online, open source tools. The aim of this paper is to describe the structure of IrrigaSys and how it is implementation at the plot scale. The DSS includes remote access to local meteorological stations for weather conditions, a meteorological model for weather forecast, the MOHID-Land model for the computation of the soil water balance and irrigation scheduling, and a database for data repository. Despite its complexity, the data necessary to run IrrigaSys is minimal, and include as mandatory input information on the location of field plots, crop type, sowing and harvest dates, soil texture, irrigation method, and daily/weekly applied irrigation depths. Based on this information, the system automatically downloads the weather data from the meteorological station located closest to the agricultural plot, as well as the weather forecast for the seven incoming days. The soil water balance is then computed from sowing to the present date (updating always the system with newly acquired information) as well as the recommended irrigation schedule for the incoming week. Results are made available via a web interface, a mobile app, a SMS, and email. The IrrigaSys further provides the Normalized Difference Vegetation Index (NDVI) computed from the most recent Sentinel-2 imagery available with a resolution of 10 m. The IrrigaSys was developed in close cooperation with the Water Board from the Sorraia Valley irrigation district, southern Portugal, supporting 103 plots of 30 farmers over the last 5 years. This stakeholder has been fundamental for successfully running the system. This paper further discusses the main strengths and limitations of IrrigaSys, with the latter being naturally associated to difficulties in providing reliable estimates for all field plots based on limited data.

Alternative low-cost precipitation kit for assessing irrigation systems

Irrigation systems must be assessed periodically to verify equipment quality and the need for adjustments. For this, precipitation test kits are necessary. However, commercially available kits have as their main disadvantage the high cost. Therefore, this study aimed to develop an alternative low-cost precipitation kit and verify its efficiency compared to an available commercial brand. The validation test was carried out at the Laboratory of Hydraulics of the Federal University of Vicosa (UFV) using a conventional sprinkler system organized in a quadrangular arrangement. Water collections were carried out within two hours using a grid of plastic collectors spaced at 3 × 3 m and installed at 0.7 m above the ground. The coefficient of determination (R2), uniformity coefficients, application efficiency, and thematic maps of the spatial variability of the applied irrigation depth were compared between kits and used for the validation of measurements. The results showed a high agreement between the developed (GESAI) and a commercial kit (Trademark) (R2 = 0.9849), and a high spatial agreement between the collected water depths. Therefore, the GESAI kit is a low-cost alternative for the assessment of irrigation systems.

Physiological and productive characteristics of the banana 'Prata-Anã' subjected to different irrigation intervals and emitter heights

This study aimed to evaluate the productive characteristics, gas exchange and water use efficiency of the banana 'Prata-Anã' clone Gorutuba under different irrigation intervals associated with different emitter heights. Therefore, a field experiment was conducted in a 2 x 4 factorial scheme: two irrigation intervals (daily and every two days) and four emitter heights (50, 70, 90, and 110 cm) in a completely randomized design with four replicates. The irrigation depths applied by the microsprinkler irrigation system were calculated as a function of crop evapotranspiration. The gas exchanges were evaluated during the period of greatest climatic stress, and the productive characteristics were evaluated at harvest. The economic water use efficiency was determined indirectly by considering the production divided by the applied irrigation depth, which was the same in all the treatments. The instantaneous water use efficiency was estimated with an infrared gas analyzer in the critical climatic period. There was no interaction between the irrigation intervals and emitter heights. The two-day irrigation interval resulted in lower values of leaf temperature and photosynthetically active radiation incident on the leaves, resulting in a higher fruit weight and, consequently, higher yields and a higher water use efficiency. The highest fruit weights were obtained at heights of 70 and 90 cm.

Crescimento e produção do jambu submetido a lâminas de irrigação

This study evaluated the effect that different irrigation depths have on the growth and crop production of jambu plants. The treatments consisted of five irrigation depths corresponding to 40%, 70%, 100%, 130% and 160% of field capacity. We used randomized blocks with four replications for the experimental design. The plot consisted of four plants in separate pots. For comparison of treatments, at 27 days after transplantation, the following variables were analyzed: plant height, stem diameter, leaf fresh matter, stalk fresh matter, root fresh matter, inflorescence fresh matter, leaf dry matter, stalk dry matter, root dry matter, inflorescence dry matter and water use efficiency. The effect of irrigation depth was significant for the analyzed variables, except for stem diameter and inflorescence dry matter. There was a quadratic behavior of the variables regarding the applied irrigation depths. The maximum values of each parameter were obtained with irrigation depths close to 100% field capacity. Although the efficiency of water use was higher for the irrigation depth of 40% field capacity, the use of irrigation depth at 100% field capacity is recommended since it provided the best answers of the variables analyzed.

Economic Viability of Conventional Sprinkler Irrigation in Sudan Grass Production for Beef Cattle

The supplementary irrigation is an alternative to ensure forage production and quality in periods with irregular rainfall, however, is necessary to know the irrigation economic viability in order to maximize profits. The study was performed in Santa Maria, Rio Grande do Sul State in southern Brazil, during 2015/2016 and 2016/2017 agricultural years, aiming to evaluate the sudan grass economic viability under different irrigation depths, in order to define which irrigation depth (0, 25, 50, 75, 100 and 125% of the reference evapotranspiration-ETo) has the highest net revenue. Forage production functions were generated and allowed to establish the carrying capacity and production costs related to each applied irrigation depth. The forage supply was 4% of the liveweight, animals with 300 kg were considered, and average daily liveweight (LW) gains of 0.5, 1.0 and 1.5 kg LW day-1 were simulated for the conversion of dry mass production in liveweight gain per hectare. Gross revenue was determined considering the price of R$ 6.50 per kilogram of liveweight. The production costs were divided into fixed and variable, related and not related to irrigation. The conventional sprinkler irrigation was economically viable for the sudan grass cultivation for beef cattle production, with the highest net revenue for the irrigation depth of 100% of ETo, in both years. However, the animals feed conversion is the determinant factor in net revenue because it represents the greatest profits variation source.

Potential Water Conservation Using Site-Specific Variable Rate Irrigation

Abstract. Site-specific variable-rate irrigation (VRI) systems can be used to spatially manage irrigation within sub-field-sized zones and optimize spatial water use efficiency. The goal of the research is to provide farmers and consultants a tool to evaluate the potential benefits of implementing VRI. The specific objective of this research is to evaluate the potential water savings using VRI management compared with uniform irrigation management to maintain soil water holding capacity above 50% depletion using two irrigation scenarios: 1) a standard 12.5 mm irrigation per application; and 2) an application to refill the soil profile to field capacity. A 21-year simulation study was carried out on a selected field with varying degrees of soil and topographic variability. The simulated field had 12 soil mapping units with water holding capacities in the top 0.30-m ranging from 42 to 70 mm. The 21-year simulation covering all weather conditions for each soil produced only two significantly different irrigation management zones for scenario 1, and for scenario 2 only one management zone. However, when the 21-year period was divided into periods with different ratios of rainfall to reference evapotranspiration, the simulations identified 1 to 5 management zones with significantly different irrigation requirements. These results indicate that variable rate irrigation system design and management should not be solely based on long term average weather conditions. Years with differing weather conditions should be used for potentially identifying management zones for VRI systems. Irrigation application depths between management zones ranged from 17 to 38 mm. However, when the actual soil areas of the study field were utilized to calculate the total volume of irrigation water applied, it resulted in an increase in water usage in the 2 and 4 management zones ranging from -1.2% to 5.8%. Water usage with VRI over uniform irrigation was greater by -1.6% to 6.8% in the 12.5 mm irrigations and by -1.2% to 2.2% for the field capacity irrigations Keywords: Management zones, Precision farming, Variable-rate irrigation, Water conservation.

Effect of Collector Size on Center Pivot Water Depth Catch

Abstract. The ASABE standard on uniformity testing of a center pivot system contains specifications on the collector size to measure the applied water depth. The standard was developed before many of the current sprinkler application devices were developed. A study was conducted to compare the catch depths of five collector sizes (opening diameters of 5.5, 10, 14.8, 20, and 27.4 cm, referenced as C2, C4, C6, C8, and C10) for three types of sprinkler application devices: spinning plate, fixed plate, and wobbling plate sprinkler systems using four 5x5 Latin squares. Each collector’s water depth was measured and statistically analyzed. Two analysis of variance (ANOVA) tests of the collector size effect were reported. Past experimental results were also compared to this experiment’s results, which generally reaffirms the difficulty of consistently measuring irrigation application depth within the practical range of collector sizes. Based on sprinkler application devices, fixed plate tends to have a more consistent depth caught compared to wobbling plate and spinning plate. If the ideal collector size selection was based on minimum variability of depth measurements, then either C6 or C4 collectors could be used. This study showed that within the range of sizes used, collector size does not substantially affect measurement of application depths for center pivot sprinkler systems. Despite the challenging task, measurement is probably within 5% if an appropriate number of collectors are used. Keywords: Catch can collector size, Center pivot irrigation, Sprinkler packages, Uniformity.

Prediction of applied irrigation depths at farm level using artificial intelligence techniques

Irrigation water demand is highly variable and depends on farmer behaviour, which affects the performance of irrigation networks. The irrigation depth applied to each farm also depends on farmer behaviour and is affected by precise and imprecise variables. In this work, a hybrid methodology combining artificial neural networks, fuzzy logic and genetic algorithms was developed to model farmer behaviour and forecast the daily irrigation depth used by each farmer. The models were tested in a real irrigation district located in southwest Spain. Three optimal models for the main crops in the irrigation district were obtained. The representability (R2) and accuracy of the predictions (standard error prediction, SEP) were 0.72, 0.87 and 0.72; and 22.20%, 9.80% and 23.42%, for rice, maize and tomato crop models, respectively.

Irrigation and organic and mineral fertilization in sunflower crop

The amount of available water to certain crops can play a direct influence on the expected effect of the application of fertilizers, whether mineral or organic origin. Thus, this work was performed in order to evaluate the effects of the application of different irrigation depths and organic and mineral fertilizers in the development and production of sunflower plants in Ceará state, Brazil. The experiment was carried out in full sun in pots containing Alfisol, in a completely randomized experimental design with a 5 x 3 factorial, five irrigation depths (L1 = 50%, L2 = 75%, L3 = 100%, L4 and L5 = 125% = 150% of the Class-A Tank evaporation ECA) and three fertilizations (F1 = organic, using aerobic fermentation of Bovine biofertilizer, F2 = mineral fertilizers, NPK-based and F3 = control without an addition of fertilizers with five replications. At 65 days after sowing (DAS), the following characteristics were analyzed: number of leaves, stem diameter, and plant height. In the maximum development of achenes (about 90 DAS), the plants were harvested to determine the head diameter, dry mass of 1000 seeds, dry mass of sunflower head, seed dry mass and crop yield. The different depths applied causing a significant effect in all the sunflower crop yield parameters being as low as the effect of the applied lower depth. The application of biofertilizers in plants provided increments similar to those provided by the application of mineral fertilizers in stem diameter, dry mass of the sunflower head, the head diameter and seed dry mass under different irrigation depths. Since most applied irrigation depth (150% of the ECA), combined with the mineral fertilizer and bovine biofertilizer provided higher results in sunflower production.

A Subsurface Drip Irrigation System for Weighing Lysimetry

Abstract. Large, precision weighing lysimeters can have accuracies as good as 0.04 mm equivalent depth of water, adequate for hourly and even half-hourly determinations of evapotranspiration (ET) rate from crops. Such data are important for testing and improving simulation models of the complex interactions of surface water and energy balances, soil physics, plant growth, and biophysics that determine crop ET in response to rapid microclimate dynamics. When crops are irrigated with sprinkler systems or other rapid additions of water, the irrigation event is typically short enough that not much ET data are compromised by the lysimeter mass change due to irrigation. In contrast, subsurface drip irrigation (SDI) systems may take many hours to apply an irrigation, during which time the lysimeter mass change is affected by both ET rate and irrigation application rate. Given that irrigation application rate can be affected by pressure dynamics of the irrigation system, emitter clogging and water viscosity changes with temperature over several-hour periods, it can be difficult to impossible to separate the ET signal from the interference of the irrigation application. The inaccuracies in the data can be important, particularly for comparisons of sprinkler and SDI systems, since they are of the order of 8 to 10% of daily ET. We developed an SDI irrigation system to apply irrigations of up to 50 mm to large weighing lysimeters while limiting the period of lysimeter mass change due to irrigation delivery to approximately ten minutes by storing the water needed for irrigation in tanks suspended from the lysimeter weighing system. The system applied water at the same rate as the SDI system in the surrounding field, allowed irrigation over periods of any duration, but often exceeding 12 h, without directly affecting lysimeter mass change and the accuracy of ET rate determinations, and allowed irrigation overnight without compromising lysimeter daily ET measurements. Errors in lysimeter ET measurements using the previous SDI system, which was directly connected to the field irrigation system, were up to 10% of daily ET compared with negligible error using the new system. Errors using the previous, directly connected, SDI system varied over time due to variable system pressure, and possibly due to water temperature (viscosity) changes and emitter clogging. With the new system, all of the water transferred to the lysimeter weighing system was eventually applied by the SDI system regardless of temperature, pressure, or emitter clogging. Differences between planned and applied irrigation depth were less than 2% over the irrigation season. Keywords: Evapotranspiration, ET, Subsurface drip irrigation, SDI, Weighing lysimeter.

Absorption of nutrients by cowpea irrigated with saline water under different leaching fractions

ABSTRACT Salinity is one of the main environmental problems that negatively affect plant growth and metabolism, besides being one of the factors responsible for the decrease in the yield of crops, especially in arid and semiarid regions. Thus, the aim of this study was to evaluate the effects of soil salinity on the mineral nutrition of irrigated cowpea. The experiment was conducted in drainage lysimeters in a greenhouse, in a completely randomized design with seven treatments, one irrigated with freshwater (control) and six irrigated with saline water with different leaching fractions (5, 10, 15, 20, 30 and 40%) of the applied irrigation depth, with three replicates. The irrigation with saline water treatments did not affect significantly the contents of macronutrients and Na in the cowpea leaves, while the opposite behavior occurred with the micronutrients.

Design and evaluation of check basin irrigation system using SURDEV software model

For efficient and judicious use of water resources, an accurate design and high quality optimization of the check basin irrigation system is necessary. BASDEV of SURDEV model was used to evaluate the check basin irrigation system of size 30 m × 45 m for medium soils in Bapatla, Guntur District, Andhra Pradesh, India, for an irrigation application depth of 75 mm with a stream size of 10, 20, 30, 40, 50, 60, 70, 80 and 90 lps. To optimize the efficiency of the design, the model was run varying the basin design dimensions and cutoff times. The outputs of BASDEV, is intended to improve the overall efficiency of basin irrigation system, provided optimum field dimensions for border irrigation in medium textured soils.

Irrigation management strategy for Prata-type banana

ABSTRACT This study aimed to analyze different irrigation strategies in two cultivars of the banana crop. The study was conducted in four production cycles of ‘Prata-Anã’ and ‘BRS Platina’ bananas. The applied irrigation depths (ID) were obtained by the model ID = K x LA x ETo, where K is an empirical transpiration constant of 0.20; 0.35; 0.50 and 0.65 for the strategies 1, 2, 3 and 4, respectively; LA is the leaf area of mother and daughter plants of ‘Prata-Anã’ and ETo is the reference evapotranspiration. The strategy 5 was obtained according to the crop evapotranspiration, ETc = ETo x Kc, where Kc is the crop coefficient. Drip irrigation system was used, with two laterals per plant row and emitters with flow rate of 8 L h-1, spaced at 0.50 m. It was found that ‘Prata-Anã’ is more efficient than ‘BRS Platina’ in terms of water use and the model for irrigation management, ID = 0.35 x LA x ETo, is recommended to optimize water use by ‘Prata-Anã’ and ‘BRS Platina’ bananas, with increase in water use efficiency and maintenance of yield. The same model, with K coefficient equal to 0.50, makes it possible to obtain yield and water use efficiency equal to those obtained with irrigation management based on the ETc.

Determining Optimal Seasonal Irrigation Depth Based on Field Irrigation Uniformity and Economic Evaluations: Application for Onion Crop

The crop water production function (WPF), representing the relationship between crop yield and seasonal irrigation water, is a useful tool for irrigation planning purposes. The objective of the paper is to propose a methodology to evaluate the optimal seasonal irrigation depth based on the crop production function, the field distribution uniformity, and economic considerations. An extended unpublished database experimentally obtained on the onion crop on the island of Kula, Hawaii, was initially used to assess the crop WPF. The combination between the crop WPF and the model representing the field distribution uniformity allowed determining the area subjected to underirrigation and overirrigation, as well as the corresponding yield, that were finally averaged across the field. An economic comparison was also carried out in order to evaluate the optimal seasonal water depth aimed at maximizing the farmer’s gross margin under different irrigation system distribution uniformities and water prices. According to the experimental data, it was observed that the onion crop is more sensitive to deficit than overirrigation, as well as that a quadratic model, valid for the entire range of the seasonal applied irrigation depths fitted better than a two-slope linear model, representing separately the conditions of deficit and over-irrigation. Moreover, the maximum yield, as well as maximum gross margin, can be obtained by applying average irrigation depths lower than those which correspond to the maximum yield, with percentages that declined at decreasing of water distribution coefficient and at increasing of water price. The proposed methodology can be applied even for other crops once the corresponding WPFs aree known, thus providing interesting evaluations that are useful for irrigation planning.

Response to the Suplementary Irrigation of Pasture in Uruguay

Pasture irrigation in Uruguay is used supplementary and strategically in long periods of lack of rainfall between the months of October to March. There are a few studies published nationally on the response of conventional pastures dry matter to the addition of water.This study aimed to know the response to irrigate pasture of white clover, lotus and ryegrass.The experiment was conducted for three consecutive years in the period from October to March of the years 2010-11 , 2011-12 and 2012-13, in a commercial property in "Colonia Rubio", Salto , on a Argiudull soil.The experimental design was random plots with three replications where the treatments were different water depths (surface irrigation) to be applied according to the estimated demand by the Penman - Monteith equation, where it is watered whenever the evapotranspiration of reference reached 20, 40 and 60 mm; plus a rainfed treatment. Determinations of the total dry matter production were done. Irrigation determinations were: applied irrigation depth , soil moisture content in a soil profile up to 80 cm, inflow in each plot, infiltrated depth and uniformity of water application in each treatment. Rainfall occurred during the months of October and March were highly variable among the three years of study, being in some period much higher than the water demand of the pasture so the soil profile had a moisture level throughout the month near the upper limit of water in the soil. Total irrigation depth applied ranged from 508 mm (season 2010-11) to 180 mm in the 2012-13 growing season. The results showed that irrigation applied from October to March caused a significant increase in dry matter of the pasture, this meant an increase in forage production caused by irrigation of almost 3 times more than in some dry periods. Among the different irrigation treatments no significant differences in forage production were observed. The dry matter production when irrigation was applied every 60 mm of evapotranspiration did not differ significantly among treatments with more frequent irrigation.