Irrigation Season Research Articles

Determination of Optimal Irrigation Using Soil Moisture Depletion on Yield and Water Productivity of Onion at Odo Shakiso District, Southern Ethiopia

Irrigation scheduling is the use of water management strategies to prevent over-application of water while minimizing yield losses due to water scarcity or drought stress. The experiment was conducted in Odo Shakiso district at a farm during the 2020/21 and 2021/22 irrigation seasons with the aim of determining the optimal irrigation schedule for yield, yield component and water productivity of onions based on the available soil moisture depletion levels. The experiment was performed in RCBD with three replicates randomly assigned to experimental plots with treatments. Five available soil moisture depletion levels (20% ASMDL, 40% ASMDL, 60% ASMDL, 80% ASMDL and FAO recommended ASMDL) were used for treatment. Results from two years of research showed that different levels of available soil moisture had a significant impact (P<0.05) on bulb diameter, bulb weight, unmarketable onion yield, marketable onion yield, and water productivity. However, different soil moisture depletion did not show a significant difference in plant height. The highest onion diameter (4.25 cm) and marketable onion yield (363.9 qt/ha) was recorded at 60% ASMDL. The highest water use efficiency at marketable onion yield (9.487 kg/m³) was also achieved at 60% ASMDL, which was statistically comparable to the FAO-recommended ASMDL treatment. On the other hand, the minimum water use efficiency (6.234 kg/m³) was recorded at 40 percent ASMDL. Therefore, based on the results of the current experiment, it is recommended to use 60% ASMDL under a furrow irrigation system for onion cultivation in areas around Shakiso and similar agro ecologies as it is the best option to increase yield and water use efficiency for onion production.

Access to Dry Season Agricultural Content in the Broadcast Media and Dry Season Irrigation Farming among Smallholder Farmers in Nigeria

Inaccessibility to information could hinder the adoption of dry season agriculture which is very significant to ending the spate of food insecurity in Nigeria. This cross-sectional survey examined access to broadcast media agricultural content and the effect of such information on dry season agriculture practice among smallholder farmers in Nigeria’s Federal Capital Territory (FCT). Participants consisted of 381 smallholder farmers selected from rural settlements in Kuje and Kwali Area councils, through a multi-stage sampling procedure. Data for the study was generated via a self-designed questionnaire. The findings of this study show that access to the broadcast media agricultural content is high (94.2%) in the FCT and the majority (83.1%) of the farmers are particularly exposed to agricultural programmes on dry season farming. However, the regularity of exposure to such programmes is considered rare/occasional by a sizable proportion (44.8%) of the selected farmers. The research further confirms the general acceptability of the broadcast programmes on dry season agriculture but the major snag is that the majority (&gt;50%) of the farmers think that the time at which the information is broadcast is inappropriate. In terms of the practical implications of the programmes, findings also revealed that &lt;50% of the respondents believe that exposure to broadcast media content on dry season farming has helped them to improve their knowledge of dry season farming practices. Nonetheless, most respondents (&gt;50%) remain adamant that dry-season farming is not achievable and productive; therefore, they have not engaged in dry season irrigation agriculture. We concluded that the knowledge gained from the dry season agricultural programmes in the broadcast media is not sufficient for farmers to successfully engage in dry season irrigation farming. The study recommends a long-term and sustained media campaign on dry season farming, the use of interactive programme content, and rescheduling agricultural programmes to farmers’ preferred time could yield the desired impact on dry season irrigation farming and food security in Nigeria.

Water-soluble organic carbon release from mineral soils and sediments in an irrigated agricultural system

Water interactions with soil and vegetation are greatly altered in agricultural watersheds compared to natural landscapes, which impacts sources and fates of organic carbon (OC). While mineral soil horizons in natural ecosystems primarily act as filters for dissolved organic carbon (DOC) leached from organic surface horizons, tilled soils largely lack an organic horizon and their mineral horizons therefore act as a source for both DOC and sediment to surface waters. Irrigated watersheds highlight this difference, as DOC and total suspended sediment (TSS) concentrations simultaneously increase during the low-discharge irrigation season, suggesting that sediment-associated OC may constitute a significant source of DOC. While water-soluble OC (WSOC) from sediments and soils has been found to be compositionally similar to stream DOC, these contributions remain poorly quantified in agricultural streams. To address this, we conducted abiotic solubilization experiments using sediments (suspended and bed) and soils from an irrigated agricultural watershed in northern California, USA. Sediments (R2 > 0.99) and soils (0.74 < R2 < 0.89) displayed linear solubilization behaviors over the range of concentrations tested. Suspended sediment from the irrigation season exhibited the largest solubilization efficiency (10.9 ± 1.6% TOCsediment solubilized) and potential (1.79 ± 0.26 mg WSOC g−1 dry sediment), followed by suspended sediment from a winter storm, then bed sediment and soils. Successive solubilization experiments increased the total release of WSOC by ∼50%, but most (88–97%) of the solid-phase OC remained insoluble in water. Using these solubilization potential estimates and measured TSS concentrations, we estimated that WSOC from suspended sediment in streams represented 4–7% of the annual DOC export from the watershed. However, field sediment export is much higher than what is represented by suspended sediment in the water column, therefore field-scale contributions from sediments could be much higher than estimated.

A social system to disperse the irrigation start date based on the spatial public goods game.

In paddy rice cultivation, the amount of water used during the beginning of the irrigation season is the highest. However, there is a possibility of a water shortage at this season as climate change decreases snowfall. In this study, we propose new schemes based on the public goods game to reduce peak water volume during this season by dispersing the irrigation start dates. In our agent-based model, agents determine the irrigation start date based on the evolutionary game theory. This model considers the economic variables of individual farmers (e.g., gross cultivation profit and cultivation cost), the cost and subsidy for cooperation for the dispersion of the irrigation start dates, and the information-sharing network between farmers. Individual farmers update the cooperation/defection strategy at each time step based on their payoffs. Using this agent-based model simulation, we investigate a scheme that maximizes the dispersion of irrigation start dates among multiple scheme candidates. The results of the simulation show that, under the schemes in which one farmer belongs to a group and the groups do not overlap, the number of cooperating farmers did not increase, and the dispersion of irrigation start dates barely increased. By adopting a scheme in which one farmer belongs to multiple groups and the groups overlap, the number of cooperating farmers increased, while the dispersion of irrigation start dates maximized. Furthermore, the proposed schemes require the government to obtain information about the number of cooperators in each group to determine the subsidy amount. Therefore, we also proposed the method which allows estimating the number of cooperators in each group through the dispersion of irrigation start dates. This significantly reduces the cost of running the schemes and provides subsidization and policy evaluations unaffected by false declarations of farmers.

Spatial-temporal distribution, source identification, risk assessment and water quality assessment of trace elements in the surface water of typical tributary in Yangtze River delta, China

As China's first cross-province ecological compensation mechanism pilot area in the hinterland of the Yangtze River Delta, Xin'an River has been hotspot in the study of rational utilization of ecological resources, and the functional value of its ecosystem services has been widely concerned. As an important tributary of the upper reaches of Xin'an River, Fengle River may affect the whole basin. The spatial-temporal distributions, occurrence, water quality and risk assessment of trace elements were studied in Fengle River in three seasons. High element concentrations were found in the downstream. Traceability models results showed that the major sources of trace elements were related to different human activities. The water quality was worse downstream in the wet season, and was more suitable for irrigation in the dry season. Risk assessment results showed that Zn, Cu, Mn, Co, and As were able to pose the risk to the ecological environment and human.

Effects of nitrogen application and intra-row spacing on growth and yield of baby corn in north-west Ethiopia

Baby corn production is relatively a new venture in Ethiopia including in north-west part of the country. Accordingly, the agronomic practices including rate of nitrogen and intra-row spacing specific to the area is not well known, which obviously influence the productivity of the crop. Therefore, the present study was conducted with the aim of identifying the optimum rate of nitrogen and intra row spacing for enhanced growth and yield responses of the crop in the study area. Field experiment was conducted during 2020/2021 irrigation season where baby corn variety SG-17 was used as test crop. The experiment consisted of factorial combination of five nitrogen levels (0, 80, 120, 160 and 200 kg ha−1 N) and three intra row spacing (15, 25 and 35 cm). The results of the study had shown that intra row spacing and nitrogen fertilizer influenced most of the tested parameters. Treatment combination of 200 kg ha−1 nitrogen and 15 cm intra row spacing recorded tallest plants, thickest stems, highest leaf area index, ear weight and length and highest baby corn and stover yields which could be proposed for the production of baby corn in the study area and areas with similar agro-ecologies. Introduction and adaptation trails on different baby corn varieties could be also considered in the future line of work.

Participatory Evaluation of Tomato (Lycopersicon esculentum Mill.) Varieties Under Irrigation Condition at Abergelle Woreda, Ethiopia

Participatory on-farm evaluation of improved tomato varieties namely;‘Melka salsa, 'Roma VF' and 'Kochero’ against the local variety was carried out in the 2019/20 irrigation season. The trial was laid on unreplicated simple plots using six farmers as replication at irrigation scheme of Saka kebele in Abergelle woreda. The experiment was intended to evaluate and demonstrate the performances of different tomato varieties for farmers, then to collect and assess their feedback. Based on the actual biological and farmers’ preference data, the analysis result underscores the better performance of improved tomato varieties over the local variety by the most yield-related attributes. The average marketable fruit yields of ‘Melka salsa, 'Roma VF', 'Kochero’, and the local variety were 4.62, 3.88, 3.64, and 3.10 ton.ha-1, respectively. The improved varieties had thus yielded an advantage of 72.38%, 37.14%, and 25.72% over the local variety in the given order. Among the improved tomato varieties, ‘Melka salsa' provided the highest fruit yield, and owing the highest score of overall preference attributes rank. The medium-sized, oval-shaped, and tasty flashed ‘Melka salsa’ tomato fruit is most liked by farmers for its less perishability, better market demand and good taste. The ‘Melka salsa’ tomato variety is therefore suggested for up-scaling for similar agro-ecologies that have irrigation schemes and production potential. The biological scientists were also advised to consider the farmers’ preference attributes and feedback as a backup for future tomato breeding studies.

Trakya Bölgesi Koşullarında Kısıntılı Sulama Programlarının Darıda (Panicum miliaceum L.) Verim Üzerine Etkileri

Millets are indigenous to many parts of the world and are more widely grown, especially in areas where water is limited. The most widely grown millet type is sorghum (Sorghum bicolor L.). A field study was carried out to determine the effect of deficit irrigation regimes on grain yield and seasonal evapotranspiration of proso millet (Panicum miliaceum L.) in the Thrace Region of Turkey. The field trials were conducted on a loam Entisol soil, on Öğretmenoğlu and Beydarı, the most popular varieties in the research area. In the study, the split plots experimental design with three replications was used. Eight different irrigation issues are considered, including combinations of the vegetative (V), flowering (F) and grain formation (Y) phases of the plant (including dry conditions, NoI). Results showed that proso millet was significantly affected by water stress during the sensitive flowering stage. The highest grain yield was obtained with 4.09 t ha-1 from Öğretmenoğlu and 4.03 t ha-1 from Beydarı, which was rinsed (VFY) in all development periods. Seasonal irrigation water use and evapotranspiration of the irrigated (VFY) in all development periods were 318 and 579 mm, respectively, for the non-stressed treatment. The seasonal water yield function was calculated as Y = 0.4087 ET + 144.03, and the seasonal yield-water response factor value was calculated as 0.57'.

Spatial Analysis of Soil Moisture and Turfgrass Health to Determine Zones for Spatially Variable Irrigation Management

Irrigated turfgrass is a major crop in urban areas of the drought-stricken Western United States. A considerable proportion of irrigation water is wasted through the use of conventional sprinkler systems. While smart sprinkler systems have made progress in reducing temporal mis-applications, more research is needed to determine the most appropriate variables for accurately and cost-effectively determining spatial zones for irrigation application. This research uses data from ground and drone surveys of two large sports fields. Surveys were conducted pre-, within and towards the end of the irrigation season to determine spatial irrigation zones. Principal components analysis and k-means classification were used to develop zones using several variables individually and combined. The errors associated with uniform irrigation and different configurations of spatial zones are assessed to determine comparative improvements in irrigation efficiency afforded by spatial irrigation zones. A determination is also made as to whether the spatial zones can be temporally static or need to be re-determined periodically. Results suggest that zones based on spatial soil moisture surveys and simple observations of whether the grass felt wet or dry are better than those based on NDVI, other variables and several variables in combination. In addition, due to the temporal variations observed in spatial patterns, ideally zones should be re-evaluated periodically. However, a less labor-intensive solution is to determine temporally static zones based on patterns in soil moisture averaged from several surveys. Of particular importance are the spatial patterns observed prior to the start of the irrigation season as they reflect more temporally stable variation that relates to soil texture and topography rather than irrigation management.

Geoelectric Monitoring of the Electric Potential Field of the Lower Rio Grande before, during, and after Intermittent Streamflow, May–October, 2022

Understanding the intermittent hydraulic connectivity between ephemeral streams and alluvial aquifers is a key challenge for managing water resources in arid environments. The lower Rio Grande flows for short, discontinuous periods during the irrigation season through the Mesilla Basin in southeastern New Mexico and southwestern Texas. Hydraulic connections between the Rio Grande and the Rio Grande alluvial aquifer in the Mesilla Basin vary spatially and temporally and are not well understood. Self-potential (SP) monitoring and time-lapse electric resistivity tomography (ERT) were therefore performed along linear cross-sections spanning the riverbed and flood plain for more than 4 months to monitor the transient hydraulic connection between the river and the alluvial aquifer by measuring time-lapse changes in the electric potential field in the riverbed and flood plain. The monitoring period began on 21 May 2022, when the riverbed was completely dry, continued through the irrigation season while streamflow was provided by reservoir releases from upstream dams, and ended on 4 October 2022, when the riverbed was again dry. SP monitoring data show (1) a background condition in the dry riverbed consisting of (a) a positive electric potential anomaly with a maximum amplitude of about +100 mV attributed predominantly to a subsurface vertical salt concentration gradient and (b) diurnal electric potential fluctuations with amplitudes of 40,000–90,000 mV attributed to near-surface heat conduction driven by weather variability, in addition to (2) a streaming potential anomaly during the irrigation season with a maximum amplitude of about −3500 mV whose transient behavior clearly exhibited a change from the background anomaly to depict exclusively losing streamflow conditions that persisted through the irrigation season. Time-lapse ERT monitoring results depict rapid infiltration of streamflow into the subsurface and imply the river and Rio Grande alluvial aquifer established a full hydraulic connection within a few hours after streamflow arrival at the monitoring site. SP monitoring data show an apparent transition from hydraulic connection to disconnection at the end of the irrigation season and indicate that the transitional phase between connection and disconnection may last substantially longer than the transition from disconnection to connection. The combination of SP and ERT monitoring demonstrated herein shows the potential for broader applications of time-lapse monitoring of hydraulic intermittency and near-surface heat fluxes in different rivers.

Influences of Seedling Age and Variety on the Growth and Bulb Yield of Onion in Northwest Ethiopia

Onion is one of the major cash crops and helps improve the livelihoods of smallholder farmers. Although genetically and morphologically different, seedlings of all released onion varieties are transplanted at the ages ranging from 40 to 50 days, which contributes to the low level of productivity in Ethiopia. Therefore, a field experiment was conducted at the research site of Fogera National Research and Training Center during the 2019/20 irrigation season with the objective of identifying the optimum seedling age for improved onion productivity in Northwest Ethiopia. The treatments consisted of three varieties (Adama red, Bombay red, and Nasik red) and four seedling ages (30, 40, 50, and 60 days) of onion, which were laid down in 3 × 4 factorial arrangement using randomized complete block design with three replications. Growth and yield parameters of onion were collected based on the standard procedures and analyzed using SAS version 9.6. The results revealed that both variety and seedling age significantly ( P &lt; 0.001 ) influenced plant height, leaf number, bulb diameter, fresh bulb weight, and marketable bulb yield, while their interaction effect did not influence these parameters. Days to maturity was significantly ( P &lt; 0.001 ) affected by main as well as by the interaction effects of variety and seedling age. Younger seedling took longer time to mature, while older seedlings matured relatively early. The seedlings of Bombay red variety at 60 days age gave the earliest maturity days (105.33 days) compared to the other combinations. The highest plant height (50.18 cm), leaf number (12.00), bulb diameter (53.47 mm), bulb weight (84.39 g), and marketable bulb yield (29.97 t/ha) were recorded from Bombay red variety where the marketable yield recorded from Nasik red was statistically similar with that of Bombay red variety. Seedlings with 60 days old performed best in terms of all the tested growth and yield parameters including the highest marketability (32.03 t/ha). Accordingly, 60 days old seedlings and Bombay red and Nasik red varieties can be used to increase the productivity of onion in the study area and areas with similar agroecology.

Evaluation of pollution indicators and transported sediment content in agricultural drainage waters for reuse as irrigation, Harran Plain, Turkey.

The aim of this study is to determine the variation of certain pollution indicators and the level of sediment carried within drainage channel discharge waters following irrigation of fields on the Harfran Plain during the irrigation season. In this context, water samples were taken from 27 stations in total, including 26 drainage channels and 1 irrigation water channel (reference point), for 6months between May 2020 and October 2020, and determined parameters were measured. Areal distribution maps were prepared with the ArcGIS program in order to better visually present the pollution level across the plain with the obtained data. The monthly changes of the analysis parameters and the significance level of the differences between the stations were determined using ANOVA analysis and the correlations between the measured parameters were determined using the Pearson correlation matrix SPSS package program. Evaluated on the basis of these areal distribution maps, it can be seen that the agricultural drainage waters of the Harran Plain are not suitable for irrigation in terms of five pollution indicators (pH, conductivity (EC), turbidity (Turb), sodium (Na+), and nitrate (NO3-)). Some sampling points in terms of pH (D9, R), conductivity (D10, D20), turbidity (all points) and Na + (as sodium adsorption rate) (D20) are in the "high usage restriction" category. In terms of conductivity, five points (D12, D13, D14, D15, D18); all points in terms of bicarbonate (HCO3-); and three points (D10, D12, D18) in terms of Na+ (as SAR) are classified as "low-medium usage restriction". According to the One-way ANOVA test performed to determine the differences between the points, there is a significant difference (p < 0.05) between the sampling points for all the following values: EC, dissolved oxygen (DO), Turb, Na+, HCO3-, chloride (Cl-), sulphate (SO42-), NO3-, pH, and transported sediment (TS), within the 95% confidence interval. In the test performed to determine the differences between the months, at the 95% confidence interval there is a significant difference (p < 0.05) between the months for parameters such as water temperature (WT), pH, DO, Turb, HCO3-, NO3-, and TS. There is a strong positive correlation between EC and Na+, Cl-, and NO3- (r = 0.785-0.915) and Turb and TS (r = 0.725). With regard to sustainable agricultural practice for the plain, it is thought that the obtained results will contribute to administrative decision-making at a variety of management levels.

Abrupt Change of the Generalized Complementary Relationship of Evaporation Over Irrigated Double Cropping North China Plain With East Asian Monsoon

AbstractThe generalized complementary relationship (CR) of evaporation was investigated in the irrigated winter wheat/summer maize double‐cropping sites in North China Plain (NCP), a region influenced by the East Asian dry winter and wet summer monsoon. Different generalized CRs exist in the winter wheat (dry) and summer maize (wet) seasons with abrupt changes in June and October. The seasonal abrupt change in the CR is attributed to the sudden reversed water vapor transport with the winter and summer monsoon and the wheat/maize rotation with irrigation in the winter wheat season. The separation and abrupt change in the complementary behavior require that two‐stage phased parameters corresponding to the wheat (dry) and maize (wet) seasons should be adopted by the generalized complementary functions for operational evaporation estimation in the irrigated double cropping NCP.

Estimation of shallow groundwater abstraction for irrigation and its impact on groundwater availability in the Lake Tana sub-basin, Ethiopia

Study regionLake Tana sub-basin of the Upper Blue Nile River Basin, Ethiopia Study focusGroundwater use for small-scale irrigation is increasing in the Lake Tana sub-basin. However, the abstraction amount and its impact are not well understood. In this study, a new methodological approach was utilized to estimate the irrigation water abstraction amount, which is based on groundwater level monitoring before, during, and at the end of the irrigation season (2021/2022). The monitoring was conducted on 361 hand-dug wells distributed throughout the sub-basin, which is subdivided into East, Southwest, and North zones. New hydrological insights for the regionGroundwater abstraction for irrigation and associated groundwater level decline estimates are 10.6 × 106 m3 and 2.43 m in the East, 4.2 × 106 m3 and 3.23 m in the Southwest, and 0.6 × 106 m3 and 1.32 m in the North. These abstractions account for 103%, 97%, and 62% of the mean annual groundwater recharge in the East, Southwest, and North zones, respectively. Groundwater is overexploited in the East and Southwest zones although, at the sub-basin scale, the amount of groundwater used for irrigation is small compared to the renewable groundwater resource. However, if groundwater-based irrigation continues to expand especially in the East and Southwest zones, groundwater scarcity at the local scales will worsen. Adaptive management strategies are required to minimize the potential adverse effects on groundwater resources.

A QUANTITATIVE ANALYSIS AND COMPARISON OF NITROGEN, PHOSPHORUS AND POTASSIUM IN SOIL AND WATER OF THE WUKARI MUNICIPAL SOLID WASTES NATURAL DRAINAGE

Preliminary investigation of Municipal Solid Waste Natural (MSW) drainage for dry season irrigation farming of Amaranths at Angwan Mission Quarters – a densely populated locality known for cultivation of Amaranths due to availability of water and its accessibility to markets was conducted. Amaranths, soil and water samples from three drainage or sampling points was collected (December 2019 - March 2020) to ascertain suitability of drainage soils and water for irrigation of Amaranths. Visual observation and analysis of selected morphological traits (plant colour, plant height (cm), plant girth, leaf area (cm2) and number of leaves) for market value was conducted. Physic-chemical analyses of pH, total organic carbon (C), total organic matter (OM), exchangeable bases (K, Na, Ca, Mg), cation exchange capacity (ECEC), moisture content, total nitrogen (N), phosphorus (P),potassium(K) concentrations of the MSW drainage soils and water were determined according to Standard laboratory procedures. Results reveal chlorosis of Amaranths at sampling point 1(Up-Stream) and sampling point 2(Mid-Stream) indicating specific mineral deficiency (such as Iron, magnesium, nitrogen) usually associated with MSW dumpsites. Significant difference (p&lt;0.05) in whole plant height, leaf area, number of leaves and % nitrogen (Up-Stream - 0.11 ± 0.00a; Mid-Stream - 0.14 ± 0.01a : Low-Stream - 0.16 ± 0.15) reflects abundance water and inadequate nitrogen levels respectively. This study remarked that the drainage points are suitable for dry season vegetable farming and the transition from rural to peri-urban settlement has potentials for continuous utilization of drainage soil and water for large-scale vegetable farming and income generation by the

Irrigation Timing Retrieval at the Plot Scale Using Surface Soil Moisture Derived from Sentinel Time Series in Europe

The difficulty of calculating the daily water budget of irrigated fields is often due to the uncertainty surrounding irrigation amounts and timing. The automated detection of irrigation events has the potential to greatly simplify this process, and the combination of high-resolution SAR (Sentinel-1) and optical satellite observations (Sentinel-2) makes the detection of irrigation events feasible through the use of a surface soil moisture (SSM) product. The motivation behind this study is to utilize a large irrigation dataset (collected during the ESA Irrigation + project over five sites in three countries over three years) to analyze the performance of an established algorithm and to test potential improvements. The study’s main findings are (1) the scores decrease with SSM observation frequency; (2) scores decrease as irrigation frequency increases, which was supported by better scores in France (more sprinkler irrigation) than in Germany (more localized irrigation); (3) replacing the original SSM model with the force-restore model resulted in an improvement of about 6% in the F-score and narrowed the error on cumulative seasonal irrigation; (4) the Sentinel-1 configuration (incidence angle, trajectory) did not show a significant impact on the retrieval of irrigation, which supposes that the SSM is not affected by these changes. Other aspects did not allow a definitive conclusion on the irrigation retrieval algorithm: (1) the lower scores obtained with small NDVI compared to large NDVI were counter-intuitive but may have been due to the larger number of irrigation events during high vegetation periods; (2) merging different runs and interpolating all SSM data for one run produced comparable F-scores, but the estimated cumulative sum of irrigation was around −20% lower compared to the reference dataset in the best cases.

Exploring the Optimal Location of Pumps as Turbines Within Branched Irrigation Networks by Global Optimization

AbstractIn this study a new procedure to address the optimization of the location and selection of pumps as turbines (PATs) within irrigation networks is presented in order to reduce network pressure and recover energy. The proposed procedure consists of two steps: in the first step the optimization of the location of devices is performed, then the optimal selection and regulation is investigated in the second step. Two new mixed integer non‐linear models have been developed and a global optimization solver has been employed to perform both optimization procedures. The procedure has been tested on a real irrigation network in Spain. The entire 2015 irrigation season has been used to properly model the water demand within the system. According to the results, the optimal solution consists of 5 PATs, installed in the middle region of the system. The investment cost has been estimated as 169,278 € with a payback period of almost 4.2 irrigation seasons. According to the solution, the effective amount of produced energy is equal to 289 MWh if the system is properly regulated and the pressure exceeding the minimum requirements is exploited to produce energy. Compared to other studies in literature focused on irrigated agriculture, the number of PATs is not fixed but rather it results from the maximization of the energy recovery and the minimization of capital costs, simultaneously. Moreover, the proposed procedure relies on a deterministic approach, achieving promising results in terms of accuracy.

Growth and tuber yield responses of potato (Solanum tuberosum L.) varieties to seed tuber size in northwest highlands of Ethiopia

Field experiment was conducted during the 2019 irrigation season to evaluate the growth and tuber yield responses of potato varieties in the highlands of Ethiopia. The treatments consisted of four potato varieties (Belete, Shonkolla, Gudanie and Local) and three seed tuber sizes (small (31.5 ± 2.5 g), medium (57 ± 2.5 g) and large (77.5 ± 2.5 g). The experiment was laid out in factorial arrangement using randomized complete block design with three replications in factorial arrangement. The results showed that, variety and seed tuber size in their main effects significantly influenced almost all the tested parameters of potato. Tuber size and variety also interact to influence days to 90% maturity, plant height, large-sized tuber yield, marketable and total tuber yields. Large-sized seed tubers of Belete and Gudanie varieties recorded the highest marketable tuber yields of 39.13 t ha−1 and 38.63 t ha−1, respectively while the lowest (12.12 t h−1) was recorded from local variety planted using small-sized seed tubers. Large-sized seed tubers of Gudanie variety gave the highest net benefit (131,376.50 ETB ha−1) with unacceptable marginal rate of return (<100%) while Belete variety with small-sized seed tubers recorded the highest marginal rate of return (1657.14%) with relatively lower net benefit. Optimizing the seed tuber size is therefore necessary to increase productivity and profitability of potato production. In this regard, Gudanie variety combined with medium-sized seed tuber recorded relatively higher net benefit (123,410.80 ETB ha−1) with acceptable marginal rate of return (100.9%). Accordingly, production of Gudanie variety using medium-sized seed tubers (57 ± 2.5 g) could be recommended for the economical production of potato and improvement of the income and food security of the smallholder farmers in the study area and areas with similar agro-ecologies.

Effect of irrigation procedures on yield and oil concentration of peanut

Peanut grasses are less demanding to moisture from formation to flowering and therefore one watering is sufficient during this period. Soil moisture LFMC from flowering to ripening should not be less than 70% and the rate of irrigation should be 700-1000 m3/ha. The seasonal irrigation norm is 4000-5000 m3/ha. The number of irrigations during the growing season is 4-5. During the growing season of peanuts, the crop is kept free from weeds, weeding, loosening of row spacing and formation of soil around the bush when gynophores are formed. The purpose of the study was to select fast-ripening, high-yielding foreign peanut varieties and samples suitable for the conditions of typical gray soils of Tashkent province in Uzbekistan, optimal planting times of local varieties, feeding standards with mineral fertilizers, irrigation regime and biostimulator application technology and scientifically substantiate its impact on the level of fatness. The increase in the number and rate of irrigation of peanuts has a positive effect on the acceleration of its physiological processes and the prolongation of the growing season. When the irrigation of the “Salomat” variety was carried out in the order of 70-75-65% compared to the LFMC, the ripening period was extended by 7-10 days and amounted to 165-167 days. Irrigation of “Salomat” variety was carried out in the order of 70-75-65% compared to LFMC, with the application of mineral fertilizers in the amount of N200P150K100 kg/ha, the yield of legumes was 29.6 q/ha, in “Mumtoz” variety - 34.0 q/ha.

Effects of seasonal irrigation subsidies on the dietary components of estuarine detritus feeders: stable isotopic analysis focusing on nereidid polychaetes

To assess the effects of seasonal irrigation subsidies from paddy fields, spatiotemporal changes in diets of detritus feeders including nereidid polychaetes Hediste diadroma and H. atoka (facultative suspension feeders) and Tylorrhynchus osawai (surface-deposit feeder) were examined in Idoura Lagoon, Sendai Bay, Japan, using carbon and nitrogen stable isotope ratios (δ13C and δ15N). δ13C ratios of Hediste species were much lower near a freshwater input (St. IB; −25.6 to −18.2‰) than in a seaward area (St. IA; −17.9 to −14.3‰), highlighting the assimilation of river subsidies in river-affected habitats. A δ13C-based isotopic mixing model showed that riverine phytoplankton and detrital matters became the major diet of Hediste species in August and December at St. IB (60 to 72%), which corresponded to the supply of irrigation drainage to the area. Contrastingly the contribution of microphytobenthos increased sharply in March at both stations (55 to 83%) because of benthic diatom blooms. These emphasize that the Hediste species can change their feeding modes (i.e., suspension- and deposit-feeding) depending on food availability in the habitat. In winter and/or spring, δ13C of H. diadroma negatively correlated with their body size, suggesting size-dependent variation in food utilization. δ13C ratios of the sympatric deposit-feeders and suspension-feeding bivalves were seasonally more stable, depending mainly on microphytobenthos and river derived materials, respectively. These suggest that a certain group of estuarine consumers including Hediste species act as significant links between terrestrial and estuarine food webs by incorporating riverine terrestrial subsidies to benthic secondary production in estuaries.