Center Pivot System Research Articles

Cotton Development and Yield Response to Irrigation, Planting Date, and Cultivar in North Carolina

In 2012, only 2.7% of North Carolina’s cotton (Gossypium hirsutum L.) was irrigated compared to the national average of 39%. The small size and nonuniform shape of most North Carolina fields are not conducive for a center pivot system. However, benefits to yield due to irrigation in North Carolina have been reported, specifically in years receiving below average or sporadic rainfall. The objective of this research was to investigate the impact of subsurface drip irrigation (SDI) on growth and yield of early- and late-maturing cotton cultivars at varying planting dates in eastern North Carolina. In 2014, the site received more than 750 mm of rainfall and no differences were observed for any parameters between irrigated and non-irrigated plots. Total rainfall in 2015 and 2016 was lower with several extended periods without rain events. There was a greater plant height increase and dry weight accumulation throughout the growing season in response to SDI. Cotton yields were increased by SDI in 2015 and 2016. Cultivar only influenced lint yield in 2016 with the earlier-maturing ‘PHY 333 WRF’ having greater lint yield than ‘PHY 499 WRF’. Planting date did not influence yield under irrigated conditions, and the timing of rainfall played a role similar to previous reports in North Carolina. Irrigation applied via SDI will increase cotton plant stature, fruit retention, and yield in response to deficit moisture conditions, independent of planting date or cultivar.

Energy Conservation Using Variable Frequency Drives for Center-Pivot Irrigation Systems Equipped with Corner Watering Attachments

Abstract. Corner watering attachments, specifically end guns and corner extensions, attached to center-pivot systems are a common means to irrigate the corners of square fields. The pumping plant is designed to supply water to all sprinklers when the center pivot is irrigating the point of maximum elevation. Most designs include powering the irrigation pump at a fixed speed, which can lead to excessive energy use. Variable-frequency drives (VFDs) were introduced to adjust the pump speed in response to changes in pressure requirements. In this study, three scenarios were analyzed: scenario 1, end gun attached at end of center-pivot lateral; scenario 2, corner extension attached at end of center-pivot lateral; and scenario 3, corner extension attached at end of center-pivot lateral and end gun attached at the end of the corner extension. This study was conducted on 1000 randomly selected center-pivot irrigation systems located in ten counties of Nebraska using GIS-based tools. High-resolution digital elevation maps were used to investigate the impact of flow rate changes and topographical variations on energy requirements. Reductions in the energy required, obtained through varying the pump speed, and annual monetary savings were calculated for each scenario. Average payback periods for VFDs were calculated for each county. The major factors contributing to energy savings and annual returns include large topographical changes, duration of corner attachment operation, hours of operation, and electricity cost. Scenario 3 resulted in the maximum energy reduction, maximum annual monetary savings, and minimum payback period compared to the other scenarios. This approach allows investigation of the potential savings associated with installation of a VFD for center pivots equipped with end guns and corner arm extensions. Keywords: Center-pivot irrigation systems, Corner watering attachments, End gun, Energy savings, GIS, Pumping, Topography, Variable-frequency drive.

CubeSats Enable High Spatiotemporal Retrievals of Crop-Water Use for Precision Agriculture

Remote sensing based estimation of evapotranspiration (ET) provides a direct accounting of the crop water use. However, the use of satellite data has generally required that a compromise between spatial and temporal resolution is made, i.e., one could obtain low spatial resolution data regularly, or high spatial resolution occasionally. As a consequence, this spatiotemporal trade-off has tended to limit the impact of remote sensing for precision agricultural applications. With the recent emergence of constellations of small CubeSat-based satellite systems, these constraints are rapidly being removed, such that daily 3 m resolution optical data are now a reality for earth observation. Such advances provide an opportunity to develop new earth system monitoring and assessment tools. In this manuscript we evaluate the capacity of CubeSats to advance the estimation of ET via application of the Priestley-Taylor Jet Propulsion Laboratory (PT-JPL) retrieval model. To take advantage of the high-spatiotemporal resolution afforded by these systems, we have integrated a CubeSat derived leaf area index as a forcing variable into PT-JPL, as well as modified key biophysical model parameters. We evaluate model performance over an irrigated farmland in Saudi Arabia using observations from an eddy covariance tower. Crop water use retrievals were also compared against measured irrigation from an in-line flow meter installed within a center-pivot system. To leverage the high spatial resolution of the CubeSat imagery, PT-JPL retrievals were integrated over the source area of the eddy covariance footprint, to allow an equivalent intercomparison. Apart from offering new precision agricultural insights into farm operations and management, the 3 m resolution ET retrievals were shown to explain 86% of the observed variability and provide a relative RMSE of 32.9% for irrigated maize, comparable to previously reported satellite-based retrievals. An observed underestimation was diagnosed as a possible misrepresentation of the local surface moisture status, highlighting the challenge of high-resolution modeling applications for precision agriculture and informing future research directions.

Automatic Identification of Center Pivot Irrigation Systems from Landsat Images Using Convolutional Neural Networks

Being hailed as the greatest mechanical innovation in agriculture since the replacement of draft animals by the tractor, center pivot irrigation systems irrigate crops with a significant reduction in both labor and water needs compared to traditional irrigation methods, such as flood irrigation. In the last few decades, the deployment of center pivot irrigation systems has increased dramatically throughout the United States. Monitoring the installment and operation of the center pivot systems can help: (i) Water resource management agencies to objectively assess water consumption and properly allocate water resources, (ii) Agro-businesses to locate potential customers, and (iii) Researchers to investigate land use change. However, few studies have been carried out on the automatic identification and location of center pivot irrigation systems from satellite images. Growing rapidly in recent years, machine learning techniques have been widely applied on image recognition, and they provide a possible solution for identification of center pivot systems. In this study, a Convolutional Neural Networks (CNNs) approach was proposed for identification of center pivot irrigation systems. CNNs with different structures were constructed and compared for the task. A sampling approach was presented for training data augmentation. The CNN with the best performance and less training time was used in the testing area. A variance-based approach was proposed to further locate the center of each center pivot system. The experiment was applied to a 30-m resolution Landsat image, covering an area of 20,000 km2 in North Colorado. A precision of 95.85% and a recall of 93.33% of the identification results indicated that the proposed approach performed well in the center pivot irrigation systems identification task.

Clock Hand Lateral, A New Layout for Semi-Permanent Sprinkler Irrigation System

The experiment was done based on a new layout for a semi-permanent set-move sprinkler irrigation system with a lower capital and annual cost requirement. In this work, a center-pivot system layout was applied to set up a semi-permanent system with a hand-move lateral. The clock hand lateral (CHL) sprinkler irrigation system was implemented using a shorter mainline length with a smaller diameter, lesser number of lateral pipes, minimum number of fittings and a single valve outlet. This combination offers an affordable irrigation system with minimizing the required components. The new irrigation system design was examined at the Agricultural Academy of Science experiment farm at Guangxi, China. The sprinkler system mainline pipe directly extended from the water resource to the center of the plot to feed a single lateral, connected through a pivot elbow. The lateral was rotating around the plot manually, the same way as clock hands do. An ordinary set-move split lateral for the same plot was designed for comparison and control. Based on results, a 37.5% capital cost reduction with an 11.2% annual cost decrement was obtained for CHL compared to the set-move semi-permanent. Water application depth was measured via distribution uniformity coefficient (DU) examination, using a catch can method. The low quarter DU for CHL was counted for 86%.

ENERGY EFFICIENCY OF A CENTER PIVOT IRRIGATION SYSTEM

ABSTRACT This study aimed to evaluate the energy efficiency of a center pivot irrigation system operating in a terrain of variable topography. Values of Pumping Energy Efficiency (PEE), Supply Energy Efficiency (SEE), Global Energy Efficiency (GEE) and Specific Energy (Es in kWh m-3) computed at 18 different angular positions of the lateral line were used as energy efficiency indicators. An ultrasonic flow meter, digital pressure transducers and a power quality analyzer were used in order to evaluate hydraulic (total system flow-Q and total dynamic head-TDH) and electrical parameters (active electrical power - AEP) of the center pivot pumping unit that were required for evaluating the selected energy efficiency indictors. Topographic elevations of the water source, the pumping unit and of the center lateral line were also determined. For the center pivot lateral line, it was necessary to determine, at the 18 angular positions considered, the altitude of the track of each center pivot support tower. Results indicated that currently, even after more than 10000h of use, the center pivot system operates with satisfactory energy efficiency, as indicated by an average GEE value equal to 42.5%, that is classified as “good”. Statistical analysis indicated that the topographic disposition of the center pivot lateral line, as characterized by a uphill or downhill disposition, resulted on different PEE, SEE and GEE values, while the average Es value (0.42 kWh m-3) was not affected by the lateral line disposition.

Parametrization of Cropsyst model for the simulation of a potato crop in a Mediterranean environment

Data from a two-year field experiment were used to calibrate (2011) and validate (2012) the parameters required by the CropSyst model for simulating the growth of a potato crop (Agria cultivar) in a semiarid area of Spain. The primary variables analysed during the parameterization model were leaf area index, canopy cover, total dry matter, total biomass at harvest, soil moisture balance, and evapotranspiration, being the potato crop subjected to four irrigation treatments (120%, 100%, 80%, and 60% of the crop water requirements “CWR”) under a center pivot system. The results showed that the CropSyst model attained a suitable goodness of fit with regards to the simulated and observed values (Willmott’s index close to 1 and errors around ±10%). Although the model includes a reduction coefficient for taking into account the effect of both water and temperature stress on the reference harvest index, yields at harvest were not properly simulated by the model. According to the results, the calibrated and validated CropSyst model showed that the 100% and the 80% CWR treatments are the most interesting ones for the farmers in the study area (both reached a suitable rate between high yield and high efficiency in the use of water).

FIELD ASSESSMENT OF PERFORMANCE WATER LOSSES OF CENTER PIVOT IRRIGATION SYSTEMS UNDER ARID CLIMATE CONDITIONS

the centre pivot system is one of the most appropriate sprinkler systems for arid or semi-arid areas where a great deal of irrigating water. The system is used widely in Saudi Arabia, and there were more than 20,000 centre pivot systems in the country. To know the reality of water application, water losses and distribution uniformity by this type of irrigation system in this country, a study was conducted in Riyadh region to evaluate 8 centres pivot systems with different ages and made of various companies and consisted of the different number of towers ranged from 4 to 10. The results showed that most of the centre pivot systems gave low distribution uniformity during water application in the irrigated areas. The values of coefficient of uniformity (Cu) were ranged between 69.2% and 89.2%, while the values of the distribution of uniformity of low quarter (Du) were between 54.1% and 81.6%, and water losses from these systems were ranged between 7.83% and 13.57%. The study also investigated the effect of main factors on water distribution and water losses in arid areas by developing a statistical model in order to determine the relationship between the losses and the factors affecting them under operating field conditions. The results of this study could assist the farmers to identify the irrigation and how to improve the system performance and the developed regression model could provide valuable information for the water application and water losses with centre pivot irrigation system in the region facing aridity and water scarcity.

Effects of Irrigation Amount on Alfalfa Yield and Quality with a Center-Pivot System

Abstract. Irrigation amount is one of the most important factors that need to be considered in the management of center-pivot irrigation systems for alfalfa producers. In 2014 and 2015, a field study was conducted at Saiwusu, Inner Mongolia, China. Three irrigation levels (100%, 80%, 60% ET) were used to evaluate the effects of irrigation amount on alfalfa yield and quality. For assessing the effects of water distribution variation of center-pivot systems on alfalfa yield and quality, the water application depth, alfalfa yield, and quality between the first span, second span, overhang, and end gun were also compared. The results showed no significant difference in annual yield between the 100% and 80% ET irrigation levels. Compared to irrigation at 100% and 80% ET, irrigation at 60% ET caused significant reductions in yield of 10% and 11%, respectively. As the irrigation amount decreased, total crop water use significantly declined from 617 to 405 mm, and water use efficiency (WUE) increased from 21.8 to 29.8 kg ha-1 mm-1. The water production functions of alfalfa were parabolic for each harvest. The proportions of seasonal actual water applied to each cutting were approximately 25%, 32%, and 43%, with contributions to annual yield accounting for 54%, 30%, and 16%, respectively, indicating that the third harvest of alfalfa had great potential for improving WUE and saving water. Irrigation level had a noticeable effect on the relative feed value (RFV) but no effect on crude protein (CP) concentration. The 60% ET irrigation level was conductive to increased CP concentration and RFV of alfalfa but was of no help to improve alfalfa quality grade. The spatial distributions of annual yield and quality were highly related to the spatial distribution of water for the center-pivot system. The coefficients of variation (CVs) for annual yield, RFV, and CP of the whole system were 5% to 12%, 2% to 8%, and 1% to 8%, respectively, while the CVs for actual irrigation amount ranged from 11% to 13%. Over-irrigation caused by the end gun slightly increased alfalfa annual yield, but it reduced the quality and WUE. Therefore, the end gun in a center-pivot irrigation system should be carefully selected for improving the uniformity of water application. The 80% ET irrigation level in the first and second cuttings and the 60% ET irrigation level in the third cutting are recommended for alfalfa production in semi-arid regions, such as western Inner Mongolia in China. Keywords: Alfalfa, Center-pivot irrigation, Quality, Water management, Yield.

Factors that Influence the Rate and Intensity of Adoption of Improved Irrigation Technologies in Alberta, Canada

Despite the importance of adopting improved irrigation technologies to increase on-farm irrigation efficiency, our understanding of what determines farmers’ adoption decisions in southern Alberta remains relatively poor. The overall goals of this study are to examine the extent of adoption (proportion of all irrigators that have started the adoption process), how far along they are in the adoption process, and the intensity of adoption (percentage of irrigated land on which the technology is adopted) of improved irrigation technologies in southern Alberta, and to assess the major factors that influenced farmers’ adoption decisions. The data were collected in a farm-household survey conducted in the 12 largest irrigation districts (IDs) as well as among private irrigators in southern Alberta. Results show that adoption of improved irrigation technologies is widespread at various levels of intensity. By 2011, 81.3% of farmers had started the adoption process, are now using some kind of improved technology to apply water to their crops, and used it on 76.8% of all irrigated land. The most commonly used irrigation technology is a low pressure center pivot system. Receiving support services following the adoption decision played an important role in increasing the intensity of adoption. Obtaining information on irrigation technologies from individual farmers or farmers’ associations, and extension agencies significantly influenced farmers’ decisions to adopt. Farmers who increased their social capital through attending meetings related to agricultural production practices were more likely to adopt while farmers who participated in recreational or social organizations were less likely to adopt. Finally, the extent and intensity of adoption are higher for those with corporate farm structure, larger families, more generations of ownership and higher education.

Effect of intra-irrigation meteorological variability on seasonal center-pivot irrigation performance and corn yield

Water application depth of a center-pivot (CP) irrigation system is not uniformly distributed across a field due to emitter package design, tower dynamics, and meteorological variability. The objective of this research was to measure and model the effect of the intra-irrigation meteorological variabilities on CP seasonal water distribution pattern and corn yield. The 2013 irrigation season of a commercial CP cropped with corn was analyzed. From 60 irrigation events applied to the corn, 10 were evaluated using radial catch cans. The mechanical movement of CP towers for the sixty irrigation events was characterized using Global Navigation Satellite System-Real Time Kinematic (GNSS-RTK) monitoring. Meteorological variables at 1s frequency were measured with an automatic weather station installed in the farm. The ballistic model calibrated and validated for rotating spray plate sprinklers under different nozzle sizes and wind conditions was mounted on the CP lateral, following the correspondent sprinkler package. The CP lateral was moved following the measured or simulated tower dynamic, and the current or averaged meteorological conditions of each irrigation event were applied to the corn. Crop yield was simulated by coupling the water distribution pattern simulated under the different cases with the Ador-crop model. Differences were observed for simulated seasonal water distribution pattern of the CP under homogeneous wind conditions (averaged for each irrigation event) or under variable of time wind conditions (measures). Simulated yield considering discontinuous tower dynamics and intra-irrigation meteorological variability has the largest correlation coefficient with the measured corn yield. Other factors were not considered in the yield simulation as variability in nutrient availability, emergence problems, and diseases and soil variability could explain the differences between the simulated and measured corn yield. The intra-irrigation meteorological variability has an important effect on the water distribution pattern of windy irrigation events of CP systems. Depending on the wind speed along the crop season, the intra-irrigation variability will have a major or minor effect on seasonal water distribution pattern and crop yield variability.

Strip tillage improves soil biological activity, fruit yield and sugar content of triploid watermelon

Tillage practices are critical for sustaining soil quality necessary for successful crop growth and productivity. A three-year study (2012–2014) was carried out to evaluate the influence of strip and conventional tillage practices and three water status levels [T1=100% of evapotranspiration (ET) demands, T2=0.75T1and T3=0.5T1] on plant morphology, physiology, yield and quality of triploid (seedless) watermelon (Citrullus lanatus cv. Magestic). Soil chemical and biological properties were also assessed at the end of the experimental study. Tillage practices (strip or ST and conventional or CT) started in 2009 and are being carried out to the present date of 2016. Irrigation was established using a center pivot system. Photosynthesis rate (Pn), stomatal conductance (gs), and chlorophyll content index (SPAD) were measured at flowering, fruit development and harvest stage and vine length measured at the harvest stage. Total marketable yield and fruit quality (firmness and sugar content) were determined during the harvest period. Soil chemical and microbial analysis were conducted at the end of the experimental period (March 2015). No significant differences (P=0.05) were found between water deficit treatments in vine length, SPAD, Pn, gs, fruit firmness, and sugar content during the three-year study, except for vine length in 2013. But, marketable yield from T1 treatment was significantly higher (P=0.03) than T3 in 2013. Vine length and SPAD measured from the ST plots were higher than CT, especially in 2012. Interestingly, marketable yield from ST was 8.6, 9.7 and 14.9tha−1 higher than CT in 2012, 2013 and 2014, respectively. Additionally, fruit sugar content under ST was statistically higher (P=0.05) than those from CT. After 6 years of tillage practices (2009–2015) in the same site, ST increased total bacteria by 49%, active bacteria by 27%, active and total fungi by 37%, nematodes by 275%, and electrical conductivity by 14% compared to CT. However, ST significantly increased root-feeding nematodes (harmful to plant roots) and reduced phosphorus and nitrate-N compared to CT. Although long-term studies aimed at assessing soil quality and cumulative yield are required to further validate our results, yield and fruit quality (sugar content) responses were consistent across three years and with promising abundance of soil microbial activities.

CHARACTERIZATION OF WATER APPLICATION UNIFORMITY, RUNOFF AND WIND DRIFT EVAPORATION LOSSES UNDER CENTER PIVOT IRRIGATION SYSTEM

The effect of water distribution uniformity (CU) on crop yield uniformity (CU yield) from a center pivot irrigation system operating under field conditions was analyzed. A field experiment was performed during two seasons (2015), located in Elmina, Alexandria and Ismailia (Egypt), in 31.3, 30.7 and 63ha. respectively plot irrigated with a center pivot system. The objectives of this paper are to study water application uniformity (CU) , run off and wind drift evaporation losses (WDEL) with two types of fixed spray plate sprinklers (FSPS): Senninger (LND-UP3-Inv. wobbler) and Nelson (D3000) both installed at the same height (1.5 m above the ground). Different predictive equations of WDEL were proposed for combinations of the two irrigation systems and the two operation times. Most equations use wind speed alone as an independent variable, although some use relative humidity or combinations of both variables plus air temperature. The results show that For two season, Senninger had higher values of CU (80–85%) than the nelson (75–80%). In sprinkler irrigation, a CU value of around 80% for each types of sprinklers can be sufficient to provide good crop yield uniformity, the mean value of run off 29% from water applied, WDEL were significantly higher with nelson (D3000) than with Senninger (LND-UP3-Inv. wobbler). The lowest WDEL values were registered with ranging from 14 to 19% under winter and summer operation conditions, respectively and mean yield for potato and sugar beet 32.7 and 91.2 ton/ha., respectively. These results were obtained for an average wind speed of 4.4 m/s at summer and 3.5 m/s during the winter and were normally below 5 m/s.

Studying uniform and variable rate center pivot irrigation strategies with the aid of site-specific water production functions

Irrigation management has evolved into a top priority issue since available fresh water resources are limited. Water production functions (WPFs), mathematical relationships between applied water and crop yield, are useful tools for irrigation management and economic analysis of yield reduction due to deficit irrigation. This study aimed at (i) designing and evaluating site-specific WPFs (using k nearest neighbors (k-NN), multiple linear regression, and neural networks), (ii) simulating yield maps for uniform, sector control VRI, and zone control VRI center pivot systems using the site-specific WPFs, (iii) using the best WPF to investigate different cotton irrigation and zoning strategies using integer linear programming, and (iv) comparing soil-based and WPF-based zones for sector control VRI systems. A two-year cotton irrigation experiment (2013–2014) was implemented to study irrigation-cotton lint yield relationship across different soil types. The site-specific k-NN WPFs showed the highest performance with root mean square error equal to 0.131Mgha−1 and 0.194Mgha−1 in 2013 and 2014, respectively. The result indicated that variable rate irrigation with limited sector control capability could enhance cotton lint yield under supplemental irrigation when field-level spatial soil heterogeneity is significant. The temporal changes in climate and rainfall patterns, however, had a great impact on cotton response to irrigation in west Tennessee, a moderately humid region with short season environment. We believe site-specific WPFs are useful empirical tools for on-farm irrigation research.

Irrigation management with remote sensing: Evaluating irrigation requirement for maize under Mediterranean climate condition

Water use control methods and water resources planning are of high priority. In irrigated agriculture, the right way to save water is to increase water use efficiency through better management. The present work validates procedures and methodologies using remote sensing to determine the water availability in the soil at each moment, giving the opportunity for the application of the water depth strictly necessary to optimise crop growth (optimum irrigation timing and irrigation amount). The analysis is applied to the Irrigation District of Divor, Évora, using 7 experimental plots, which are areas irrigated by centre-pivot systems, cultivated to maize. Data were determined from images of the cultivated surface obtained by satellite and integrated with atmosphere and crop parameters to calculate biophysical indicators and indices of water stress in the vegetation—Normalized Difference Vegetation Index (NDVI), Kc, and Kcb. Therefore, evapotranspiration (ETc) was estimated and used to calculate crop water requirement, together with the opportunity and the amount of irrigation water to allocate. Although remote sensing data available from satellite imagery presented some practical constraints, the study could contribute to the validation of a new methodology that can be used for irrigation management of a large irrigated area, easier and at lower costs than the traditional FAO recommended crop coefficients method. The remote sensing based methodology can also contribute to significant saves of irrigation water.

Effect of Three Tillage Implements on Potato Yield and Water Use Efficiency

The objective of this study was to evaluate the effect of tillage implements on potato yield and water use efficiency. The study was conducted at a private farm at Al-Kharj Governorate, Saudi Arabia during 2015 in randomize complete block design with three replications. Three primary tillage implements commonly used in Saudi Arabia for seedbed preparation with different configurations: disk harrow, chisel plow and moldboard plow were used. The potato variety used was Spunta. Centre pivot system was used to provide irrigation water. The statistical analysis indicated that tillage implement had significant effect on yield and water use efficiency. The highest yield of 37.19 t/ha was observed during plowing with moldboard plow and the lowest (32.33 t/ha) was observed during plowing with disk harrow. The highest water use efficiency of 7.91 kg/m was observed during plowing with moldboard plow and the lowest (6.88 kg/m) was observed during plowing with disk harrow. The results could be helpful to develop comprehensive technology to increase potato yield and water use efficiency in semi-arid region like Saudi Arabia. Original Research Article Al-Hamed et al.; AJEA, 12(3): 1-6, 2016; Article no.AJEA.24950 2

Rendimiento y calidad de praderas de Lolium perenne L. bajo riego en la Zona Sur de Chile

The objective of this work was to study the effect of irrigation on yield and quality of Lolium perenne L. pastures at Southern Chile. The trial was carried out at Cocule, Rio Bueno, Los Rios Region, between November 1st 2012 and April 30Th 2013. Measurements were taken at two sectors, A and B. The unirrigated treatments (control) received water from precipitation (475 mm), and the irrigated treatments received water from precipitation and a central pivot system (895 and 920 mm for sector A and B, respectively). Irrigated treatments were located under the pivot, whereas unirrigated treatments were located 40 m from the pivot. Three sample plots of 10 x 10 m were established at each treatment. Pastures were grazed by dairy cows and dry matter production was estimated by a pasture plate meter with 100 observations per plot. Nine grazing events were conducted during the study period and before each grazing forage samples were taken from the plots to determine dry matter (DM), crude protein, metabolizable energy, neutral detergent fiber and in vitro digestibility. Tiller density was measured on April, at the end of the sampling period. Results showed significant differences on dry matter production with an increment of 3 to 4 ton DM ha-1, as effect of irrigation. Tiller density and nutritive value increased significantly in irrigated pastures.

The Modernization of a Large Irrigation Perimeter to Support Rural Sustainable Development - study Case of Matala (South of Angola)

Matala Irrigation Perimeter (MIP), located in the Cunene river basin, Huíla Province, South of Angola, is under a modernization process, managed by the Angola government. It aims a sustainable rural development, focusing on the socioeconomically aspects and the reduction of poverty of the local populations. This paper describes the MIP and presents the main results of a research study carried out to evaluate this process to establish actions for its improvement. It includes procedures for better water use at conveyance network and on-farm levels, and for higher land productivity through the improvement of crop systems. MIP has an area of 10,732 ha, being the water diverted from the Matala dam, in Cunene River. The irrigated perimeter was built in the 1960s, with a gravity canal distribution system, designed for traditional surface irrigation methods. Since 2002, the MIP was deeply rehabilitated, through the recovery of the main canal and water control structures, the enlargement of the irrigated area and the implementation of agro industrial and animal production units. MIP has several constraints, related with the maintenance of hydraulic structures, the effectiveness of water distribution, and shortage water supply. The main crops grown are potato, tomato, maize, pasture, horticultural and fruit trees, being their irrigation scheduling analysed. The development of on-farm irrigation has been set as an important priority, because the majority of the area applies low effective traditional methods. The modernization of the surface irrigation is a key crucial option, particularly in the flat soils with topographic conditions for gravity supply. The micro irrigation, particularly the drip irrigation, is applied in tomato crop and fruit tree, and the fixed or centre pivot systems used for maize and pastures. The research presented in this paper evaluated those systems, the performance indicators and the main difficulties found, including the requirements of farmer's technical support.

Uniformity Assessment of Irrigation with Centre Pivots in Uruguay

Irrigation with centre pivots has increased exponentially under the last decade in Uruguay; starting with a few sets, now there are more than 350 sets which cover 30.000 ha. To conduct performance evaluations of the centre pivots we selected a representative sample of the sets used in Uruguay: 20 sets in three different regions in the country, whose lateral longitude ranged from 398 to 802 m. Uniformity tests of the equipments were conducted according to the methodology proposed by the international standards: ANSI/ASAE S436.1 (JUN 1996). The uniformity coefficient of Hermann and Hein (CUh) of 16 sets reached acceptable values (80 to 87 %), while the rest obtained very low coefficient values (54 to 71%). Distribution Uniformity values (UD) followed the same tendency as CUh values. The 16 sets with high CUh, obtained high UD values (71 to 85%), whereas the rest got lower UD values (26 to 70%). Centre pivots may attain high application uniformity in Uruguayan agrosystems, given an adequate combination of system design and operation. An inaccurate management of centre pivots due to operation below required pressures and to poor maintenance of sprinklers will directly impact the sheets applied, and the application uniformity and efficiency of the centre pivot system.

Potato Yield and Water Use Efficiency Responses to Irrigation in Semiarid Conditions

Potato (Solanum tuberosum L.) yield is sensitive to water stress in the semiarid regions of Spain. This study was conducted to determine the effect of four irrigation treatments on potato tuber yield under one‐quarter (4.9 ha) of the total irrigation area (18.4 ha) of a center pivot system in Albacete, Spain, during 2011 and 2012. Four irrigation treatments were applied, representing 60, 80, 100, and 120% of potato crop water requirement (CWR). In 2011, crop yield differed between the 60% irrigation treatment and the other treatments, whereas in 2012, yield differed between irrigation treatments with high (100 and 120%) and low (60 and 80%) water supply. Water use efficiency (WUE) ranged from 8.6 to 11.6 kg m−3 in 2011 and 7.1 to 8.4 kg m−3 in 2012, with significant differences among treatments in 2011. Differences in harvest index (HI) were observed between the irrigation seasons due to weather conditions of the second year. The 80% treatment was more efficient or equally efficient compared with the unstressed treatments and therefore represents a viable option when there are limited water supplies or high water costs.