Koga Irrigation Research Articles

Farmers' Perceptions and Practices in Managing Vegetable Pests and Pesticide Use in the Upper Blue Nile Basin, Ethiopia: In the Case of the Koga Irrigation System

This experiment was carried out to assessment of farmers’ perceptions, knowledge, and current management practices on the major pests among vegetable growers in the Koga irrigation system, Ethiopia. Understanding the farmers’ awareness and pest management is essential for designing a research agenda, and awareness creation. The survey was carried out from November 2020 to March 2021 in Koga irrigation, with a total of 63 vegetable growers. A semi-structured questionnaire was used. Almost all farmers in the study area overwhelmingly depend on pesticides to control the pests on their vegetable crops. Profenofos, Dimethoate, and Lambda-cyhalothrin were dominantly and commonly used insecticides in the study area with different trade names for more than two vegetables. There are two common and widely used fungicides named Metalaxyl-M 68 %WG and Mancozeb regarding disease control. The farmers used wrong application techniques, inappropriate spraying, wrong storage practices, and protective measure of pesticides. This wrong perception and practice could be associated with their limited knowledge about pesticides and related activities. Hence, it is recommended that government or non-governmental organizations should focus to improve the misuse and misperception of farmers in pesticide use, including personal and environmental protection through education and community intervention.

Assessment of irrigation performance trends using selected comparative indicators over consecutive periods: A case study of the Koga Irrigation Scheme in the Amhara region, Ethiopia

AbstractThe Koga Irrigation Scheme is a modern irrigation scheme in Ethiopia, and furrow irrigation is a common water application method. The main purpose of this study is to show in which year it performed well and what the problems were and to identify the best alternatives that may be essential for managing the scheme effectively and efficiently. The performance trends of the Koga Irrigation Scheme were evaluated using four selected performance indicators, namely, physical, agricultural, water use and economic performance indicators. Primary and secondary data, including geographic locations, water supply, harvested yield, market prices, irrigated crops, actual irrigated area, planned irrigable area, total management and operation cost, water fees and historical climate data, were collected. Land use performance analysis indicates that the scheme operates below its potential. The maximum irrigated area was 6,327.7 ha less than the designed 7,000 ha in 2015 and 3,619.9 ha in 2016. Water consumption peaked in 2015 and decreased in 2016. The dominant crops were wheat (55%), potato (19%), barley (7.6%), onion (7.4%), maize (5.6%) and other crops (5.4%). This suggests a preference for low‐value, water‐intensive crops. Water use by crops is lower than reservoir release, indicating significant water loss. Economic water productivity is low, primarily due to the dominance of low‐value, water‐intensive crops. To enhance scheme performance, the study recommends adjusting cropping patterns, estimating actual water demand for the respective crops and irrigation scheduling, adopting efficient water application methods and strengthening the market chain.

Economic productivity of irrigation water in large-scale irrigation schemes with different typologies: the case of Fincha’a and Koga irrigation schemes in the Abbay River Basin, Ethiopia

Economic productivity of irrigation water in large-scale irrigation schemes with different typologies: the case of Fincha’a and Koga irrigation schemes in the Abbay River Basin, Ethiopia

Comparative Analysis of Precast and In situ Concrete and Their Effectiveness on Koga Irrigation Structures

Most construction projects in Ethiopia are built by using conventional cast in situ concrete. However, the latest technology reveals various priorities of the precast construction method over the cast in situ concrete. The main aim of this study is to analyze better irrigation lining concrete among two types of casting by conducting visual inspection methods and non-destructive tests to characterize defects. Koga irrigation main canal, which is found in Northwest Ethiopia, was used as a study area because it is made of both in situ and precast concrete linings. The study reveals that the lower strength, severe defects, and lower uniformity due to the high level of difficulty in pouring and vibrating the concrete on the side slopes of the canal were observed in the in situ lined canal. However, the growth of grass in the joints, and sealing of closely spaced and less water-tight joints are observed at the precast part of the canal lining. Providing reinforcement bars on the in situ canals and providing water-tight joints for the precast concrete part are viable solutions.

Satellite and Model-based Estimation of Crop Water Requirement of Major Irrigated Crops in the Koga Irrigation Scheme, Ethiopia

Satellite and Model-based Estimation of Crop Water Requirement of Major Irrigated Crops in the Koga Irrigation Scheme, Ethiopia

Yield and lodging response of tef [Eragrostis tef (Zucc) trotter] varieties to nitrogen and silicon application rates

Lodging, poor crop varieties and nitrogen management are among the main tef cultivation problems in acidic soils of northwestern Ethiopia. Though Si has been shown to improve crop yield and lodging resistance, knowledge of its effect on tef, along genotypes and nitrogen, is yet to be uncovered. Therefore, a 4 × 2 × 2 factorial field experiment was conducted on fixed experimental plot at the Koga irrigation scheme to assess yield and lodging responses of tef varieties to nitrogen and silicon fertilizer rates during two consecutive years of 2021 and 2022. The experiment comprised four nitrogen levels: 0 (N1), 23 (N2), 46 (N3), and 92 kg N ha−1(N4), two Si levels: 0 (Si1) and 485 (Si2) kg ha−1, and two improved varieties: Hiber-1 (V1) and Quncho (V2) treatment combinations, which were replicated four times. Results showed that regardless of silicon supply and variety, nitrogen had a significant effect (p < .0001) on agronomic attributes of tef grain yield, biomass yield, harvest index, chlorophyll content, plant height, panicle length, leaf area index, and the number of plants m−2 over the two years. Application of N4, N3, and N2 improved grain yield by 166.9, 126.2, and 75.2 % over N1, respectively. The harvest index showed a declining trend with nitrogen rates, which ranged from 36.1 to 26.5 %. Hiber-1 showed a significantly (p < .01) higher panicle length than Quncho. The interaction of nitrogen, silicon, and variety significantly (p < .001) affected lodging index, with a minimum lodging index of 0 % from V1Si1N1 and a maximum lodging index (71.9 %) from V2Si1N4. Maximum net return (2552.6 USD) was obtained from V1Si1N4, while the marginal rate of return (6961.7 %) from V1Si1N3. Therefore, it can be concluded that genotype and optimum nitrogen can maximize yield and lodging resistance of tef, while silicon in the form of carbonized rice husk results no significant effect on tef lodging.

Evaluation of Koga irrigation water in Mecha district, Amhara Region, as an example of irrigation water quality in Northwestern Ethiopia

Irrigation water quality impacts plant growth, crop production, and public health. Thus, understanding the trends in irrigation water quality is important to manage public health, and optimize crop production. The Koga region in Ethiopia is a developing area where crops are an important food source for a growing population, and irrigation is critical to supply additional food crops and secure food insecurity issues. This study measures physiochemical and biological parameters to assess the suitability of Koga irrigation water for crops intended for human consumption. In March 2022, irrigation water samples were collected and analyzed for physicochemical and biological qualities. Kelley’s ratio, magnesium danger, and sodium absorption ratio were calculated from the data obtained. Results showed that the turbidity (174.33–259.00 NTU), total suspended solids (80.33–175.00 mg/L), total alkalinity (143.33–195.33 mg/L), total hardness (150.67–224.6 mg/L), SO42−(43.96–73.00 mg/L), PO43−(56.27–87.43 mg/L), and BOD5 (63.23–95.40 mg/L) levels surpassed the recommended limit of FAO(35 NTU,50 mg/L,100 mg/L,100–150 mg/L,20 mg/L,3 mg/L and 30 mg/L, respectively). BOD5 levels of the tested water samples exceeded the permissible limit set by the EU (10 mg/L). The coliform and fecal coliform levels in all sampled waters were higher than the zero/100 mL limits of the EU and WHO set for irrigation water. The studied water samples were found to be unsuitable for the cultivation of crops and vegetables since TA, PO4−3, and NO3− levels exceeded the tolerance limit of the crops and vegetables cultivated in the site, while the coliform and BOD5 levels surpassed their tolerable limits. Consequently, it is not recommended to eat crops and vegetables without first properly preparing them. The results showed improper ratio of Mg2+:Ca2+ and Na+:Ca+2, and a magnesium hazard was foreseen. This study showed that the turbidity, total suspended solids, total alkalinity, total hardness, SO42−, PO43−, BOD5, and the coliform levels of the studied irrigation water samples of the Koga irrigation project were not found within the safe limits of FAO, WHO, EU, and irrigation water quality limits of different nations, even though additional samples evaluating seasonal fluctuations are needed to fully assess the water quality.

Effects of irrigation scheduling methods and blended NPS fertilizer on tuber yield and water productivity of potato (Solanum tuberosum L.) in northwest Ethiopia

Irrigation water scheduling methods influence the growth, yield, and water productivity of crops including potatoes. Therefore, a study was conducted to evaluate the effects of irrigation frequency determination methods on tuber yield, irrigation water productivity and fertilizer use efficiency of potatoes at Koga irrigation scheme, in Northwest Ethiopia. The treatments were consisted of two irrigation frequency determination methods (wetting front detector and crop water requirement) and six NPS fertilizer rates (0, 90.8, 136.2, 181.6, 227.4 and 272.0 kg ha−1, which were factorial combined in a randomized complete block design with three replications. Growth and tuber yield data of potato were collected based on the standard procedure. Irrigation water productivity, partial factor productivity, and agronomic efficiency were calculated using their respective models. The collected data were analyzed using SAS version 9.4. The results revealed that the wetting front detector method recorded the highest tuber weight (79.5 g), tuber yield (41.9 t ha−1), and irrigation water productivity (9.1 kg potato m−3 water) compared to crop water requirement method. NPS fertilizer at the rate of 272 kg ha−1 also produced the highest tuber weight (86.5), tuber yield (58.1 t ha−1) and irrigation water productivity (12.4 kg potato m−3 water). Treatment combination of wetting front detector and 272 kg ha−1 NPS recorded the highest plant height (64.m cm) and stem number (10.4). Wetting front detector method recorded the highest partial factor productivity (275.2 kg potato per kg NPS) compared to crop water requirement. Wetting front detector combined with NPS rates generally recorded higher partial factor productivity compared to the respective NPS rates combined with crop water requirement. NPS fertilizer at 272 kg ha−1 combined with wetting front detector gave the highest net benefit (236,591.7 ETB ha−1) with acceptable marginal rate of return (248.9%), which is recommended for economical production of potato in the area.

A remote sensing approach to estimate variable crop coefficient and evapotranspiration for improved water productivity in the Ethiopian highlands

Proper and reasonable estimation of actual evapotranspiration is critical for the design, operation, and management of irrigation systems. However, the density of climatic stations is low in many parts of Ethiopia to estimate spatially reasonable reference evapotranspiration (ETo), and the lack of spatial variability of crop coefficient (Kc) is clear barrier to the proper management of irrigation water. Therefore, the main objective of this study was to estimate reasonable crop evapotranspiration (ETc) by deriving spatially and temporally varying crop coefficients using remote sensing products in 10 wheat plots at the Koga irrigation scheme. The moderate-resolution imaging spectroradiometer (MODIS) potential evapotranspiration was calibrated at two class-I climate stations (Bahir Dar and Dangila) based on Penman–Monteith estimates and Normalized Difference Vegetation Index (NDVI) was derived from Sentinel 2B, which was later used to derive Kc. The correlation between reference evapotranspiration from MODIS Penman Monteith was acceptable for both Dangila (R2 = 0.64) and Bahir Dar (R2 = 0.74) stations. The MODIS calibration constant for Koga irrigation schemes was 0.27 and 1.99 (regression slope and constant) on an 8-day basis. Similarly, a strong correlation (R2 = 0.95) was found between Sentinel-based NDVI and FAO crop coefficient, which indicated an alternative pathway for estimating crop coefficient. The value of Kc varies in space (across the 10 plots) from 0.16 to 0.42 at the initial stage and from 1.20 to 1.32 at the mid-stage. Similarly, the mean value of Kc varies in time from 0.29 at the initial stage to 1.26 at the mid-stage. On the other hand, evaluation of MODIS and WaPOR ETc found a significant difference (p < 0.05) with the calibrated MODIS-Sentinel 2B derived ETc. This indicated the need to calibrate both MODIS and WaPOR for the proper estimation of crop water needs. Underestimation of ET was observed from MODIS, and the reverse is true for WaPOR. Our findings showed that calibrating and integrating MODIS with Sentinel 2B would be a feasible approach to estimate Kc and hence ETc that varies in time and space. This would assist water managers in estimating crop water needs for better productivity in the region.

The Efficacy of Selected Insecticides Against Wheat Aphids on Irrigated Wheat in North Western Amhara, Ethiopia

Aphid infestations cause significant losses in wheat production. The experiment was conducted at the Koga irrigation site during 2021 to evaluate the efficacy of commercial insecticides for the management of wheat aphids. Seven types of insecticides with unsprayed control were laid in a completely randomized block design with three replications. The result showed a reduced aphid infestation with maximum grain yield were from dimethoate, imidacloprid, lambda-cyhalotrin, profenfos + lambda-cyhalothrin, imidacloprid + lambda-cyhalothrin, and profenofos-sprayed plots. However, the greater net benefit and marginal rate of return were provided by the applications of imidacloprid and dimethoate insecticides. The economically feasible insecticide application can be considered as an effective aphid management practice in wheat production.

Assessment of a Smartphone App for Open Channel Flow Measurement in Data Scarce Irrigation Schemes

Accurate water flow measurement ensures proper irrigation water management by allocating the desired amount of water to the irrigation fields. The present study evaluated whether the non-intrusive smartphone application “DischargeApp” could be applicable and precise to measure small canal flow rates in the Koga irrigation Scheme. The app was tested in unlined canals with flow rates ranging from 15 to 65 l/s using a 90° V-notch weir. The app is found to overestimate high flow rates. Another source of uncertainty is that the app employed a constant surface velocity conversion factor (C = 0.8) to compute discharge. The accuracy was enhanced by recalculating the measured discharge using a new surface velocity conversion factor that depends on depths. The new conversion factor decreased the errors of MAE and RMSE by 47% and 52%, respectively. Where channel and other optional measuring techniques are not available without interfering with the flow operation conditions in place, the DischargeApp devices can be used to measure flows. The DischargeApp could be used to collect data using local citizens in data-scarce areas. This study suggested reconfiguring the DischargeApp with a new surface velocity conversion coefficient based on flow depths in field conditions for better performance.

Effect of deficit irrigation and soil fertility management on wheat production and water productivity in the Upper Blue Nile Basin, Ethiopia

In the Ethiopian Upper Blue Nile Basin, like in other regions in the world, agricultural productivity is declining due to water scarcity owing to longer dry seasons coupled with soil acidity−induced fertility problems. Wheat is one of the major food security crops in Ethiopia but its productivity is reduced due to water scarcity, especially during the irrigation season. Addressing these problems might be essential to increase productivity. This study explores the effect of deficit irrigation (DI) combined with lime, manure and inorganic fertilizer on wheat production and water productivity (WP) in the Koga irrigation scheme, Ethiopia. Four levels of DI strategies (100% ETc or 0% deficit as a control, 80%, 60% and 50% ETc) were applied for two irrigated seasons. Five levels of soil fertility management were applied for four consecutive cropping seasons: (i) 0.86 t ha−1 lime combined with 3 t ha−1 manure and full dose urea and NPS−B (hereafter referred to as inorganic fertilizer) (L3); (ii) 1.15 t ha−1 lime combined with 3 t ha−1 manure and full-dose inorganic fertilizer (L2); (iii) 1.43 t ha−1 lime combined with 3 t ha−1 manure and full dose inorganic fertilizer (L1); (iv) 3 t ha−1 manure combined with full dose inorganic fertilizer (M); and (v) full dose inorganic fertilizer alone (C). The grain yield and biomass data were collected at harvest from a sample area of 2 m × 3 m from each plot with three replicates. The effect of DI and liming, as well as manuring on average grain yield and biomass, were highly significant. Under all irrigation scenarios, higher grain yield and biomass were found at L1, L2, L3 and M (in that order), compared with C. The highest WP was obtained at 50% ETc irrigation dose, compared with 60%, 80% and 100% ETc (in that order). Yet, the lowest WP was found at C under all irrigation scenarios compared with L1, L2, L3 and M. The WP increased when the amount of water supply decreased and liming doses increased. The application of full dose lime and manure combined with 50% ETc DI resulted in comparable grain yield, biomass and WP as 100% ETc full irrigation at L3 and M. It could be concluded that liming and manuring could be used to mitigate the yield penalty effect of DI in the study area. In scenarios where farmers have to pay for water, profitability rises as the irrigation water supply reduces. Thus, under such conditions, a 50% ETc irrigation scenario is more profitable than scenarios with 60%, 80% and 100% ETc irrigation.

Yield, water productivity and nutrient balances under different water management technologies of irrigated wheat in Ethiopia

Development of irrigation technologies and agricultural water management systems holds significant potential to improve productivity and reduce vulnerability to climate change. Our study dealt with the behavior of irrigation water productivity, partial nutrient balance and grain yield of wheat under the application of different irrigation water management technologies in the Koga irrigation scheme in Ethiopia. For our analysis, we considered three nutrient fluxes entering and leaving farmers’ fields. Our experimental design had three irrigation blocks with three different irrigation water management practices (wetting front detector, Chameleon soil moisture sensor and farmers’ practice as control) on three farm plots replicated in each block. To calculate irrigation water productivity and grain yield of wheat, the amount of irrigation water applied and the agronomic attributes of wheat yield were recorded during the irrigation period. Further, three input and output variables were considered to determine the partial nutrient balances of nitrogen (N), phosphorus (P) and potassium (K). The results showed that the amount of irrigation water used was 33% and 22% less with a wetting front detector and Chameleon sensors, respectively, compared to the farmers’ practice. The wetting front detector (WFD) and Chameleon sensor (CHS) treatments gave a 20% and 15.8% grain yield increment, respectively, compared to the farmers’ practice plot. The partial nutrient balances of N and K were negative for the wetting front detector and chameleon sensor practices while it was positive for P in the control (farmers’ practice) treatment. We conclude that irrigation water management with appropriate technologies can improve yield, water productivity and the nutrient utilization. However, further research needs to be conducted on the suitability of irrigation management technologies to achieve full nutrient balance.

Assessing Farm Water Management and Performance of Koga Irrigation Scheme: a Case Study of Inguti Unit, Amhara Regional State, Ethiopia

Assessing Farm Water Management and Performance of Koga Irrigation Scheme: a Case Study of Inguti Unit, Amhara Regional State, Ethiopia

Relatives, neighbors, or friends: Information exchanges among irrigators on new on-farm water management tools

CONTEXTOn-farm water application in Ethiopia, as in much of Sub-Saharan Africa, is dominated by furrow irrigation, which resulted in inefficient water uses and related economic and environmental problems. A recent project introduced two on-farm water management tools, called wetting front detectors and Chameleon sensors, to some farmers in Koga irrigation scheme and facilitated for other farmers in the quaternary canal, who did not receive the technology, to learn from farmers who installed the tools on their plots. OBJECTIVESThe objective of this study is to investigate the role of different social ties on information exchanges among farmers when some farmers have the signal on how long to irrigate a field during an irrigation event from on-farm water management tools. The study explored the relative importance of being neighbors, friends, spatial proximity of farms, and project induced pairings. METHODSThe study used a household survey data from all members of quaternary canals in the project that were in the technology, information, and control groups, as well as detailed network modules on how farmers with plots in the quaternary canal are associated with each other. A fixed effects econometric approach is used to control for time invariant household level and quaternary canal characteristics, while teasing out how the different social ties affect the information flow. RESULTS AND CONCLUSIONSThe results show that being in purposeful friendships as indicated by knowing each other's decision on the use of agricultural inputs and its outcome, as well as being spatially proximate as indicated by having farm plots next to each other or usually passing by each other's plots play a significant role in determining whether information-recipient farmers received information from the technology-recipient farmers as expected. Being relatives or neighbors played a minor role to facilitate information exchanges on how long to irrigate. In addition, ad-hoc pairs of farmers between technology-recipient and information-recipient created through the project within the quaternary canal did not play a significant role above and beyond the existing social ties of friendships and spatial proximity. SIGNIFICANCEThe findings have implications for effective ways of targeting in future scale up of such technologies as it informs that the roll out of such type of technologies and the extension services around it can better help technology diffusion and learning if they use friends and spatial proximates as anchors of information. That is, at times of over-subscription to such on-farm water management tools, information about the technology and the recommended duration of one irrigation turn can diffuse faster if the limited number of tools are distributed in such a way that friends and spatial proximates have access to a tool, rather than distributing the tools based on being neighbors or relatives.

Intestinal helminthiasis survey withemphasison schistosomiasis in Koga irrigation scheme environs, northwest Ethiopia.

BackgroundDistribution of schistosomiasis is more focal due to spatial heterogeneities in intermediate host snail dynamics and water contact behavior of humans. This makes the search for new transmission foci of schistosomiasis and its connection with malacologically receptive water bodies essential for effective control of its transmission. This study was intended to assess the prevalence of intestinal helminth infections among schoolchildren and Schistosoma mansoni transmission in Koga irrigation scheme surroundings, northwest Ethiopia.Materials and methodsCross-sectional parasitological and malacological surveys were conducted in three schools and nearby water bodies, respectively around Koga irrigation scheme. Stool specimens were collected from 421 randomly selected schoolchildren and microscopically examined using Kato-Katz and formol-ether concentration methods. Malacological surveys were carried out and the identified Biomphalaria pfeifferi snails were screened for schistosome infection. Swiss albino mice were exposed to schistosome cercariae shed by Biomphalaria pfeifferi for definite identification of Schistosoma species.ResultsAmong the examined schoolchildren, 22.6% (95% CI: 18.7%-26.9%) were positive for at least one intestinal helminths species. Ascaris lumbricoides was the most frequent intestinal helminth detected among forty (9.5%) children. Schistosoma mansoni was detected among 4.8% (95% CI: 2.9%-7.2%) of children and its prevalence was significantly higher among male children (p = 0.038) and those attending in Mengesha Jemberie Primary School (p = 0.044). Biomphalaria pfeifferi snails were identified in water bodies in close proximity to Mengesha Jemberie and Wotete Abay Primay schools. Schistosoma mansoni adult worms were harvested after exposure of mice to cercariae shed from Biomphalaria pfeifferi snails collected from water bodies nearby Mengesha Jemberie Primary School.ConclusionsSchistosoma mansoni infection of schoolchildren, findings of schistosome infected snails and establishment of mice infection confirm that transmission is taking place in the study areas. Hence, snail control and other measures such as provision of sanitary facilities and health education are recommended.

Determination of Crop Water Requirements and Irrigation Scheduling of Wheat Using Cropwat at Koga and Rib Irrigation Scheme, Ethiopia

: Population growth, high water competition, and the effect of climate change have caused water shortage problems in the Nile basin, Ethiopia. Proper water management improves water efficiency and determining the water requirement of field crops are options for improving water productivity. In this study, the CROPWAT 8.0 model, local climate, and soil data were used to determine crop water requirement (CWR) and irrigation scheduling of wheat at Koga and Rib irrigation scheme, Nile basin. The Penman-Monteith and United States Department of Agriculture (USDA) soil conservation service methods were used to compute the reference evapotranspiration (ETo) and effective rainfall. Five levels of water depth (50%, 75%, 100%, 125%, and 150%) of the model and two irrigation intervals (14 and 21 days) were arranged in a Randomized Completely Block Design. The Koga, irrigating 75% of CROPWAT simulated water depth (9.3 , 22.9 , 44.1 and 25.8 mm at initial, development, middle and late-stage respectively) gave 3.37 t ha wheat yield and 1.01 kg m water productivity. The result at Rib showed that -1 -3 irrigating 75% of the model (9.1, 23.6, 47.2, and 34.2 mm at initial, development, middle, late-stage, respectively) gave 4.27 t ha yield and 1.81 -1kg m water productivity of wheat. The reference evapotranspiration varied from 4.86 to 3.14 mm day at Koga and from 4.67 to 2.36 mm day -3 -1 -1at Rib scheme. The irrigation requirement of wheat at Koga was 376.9 mm dec while at Rib was 379.9 mm dec . The CROPWAT model is an -1 -1important tool to compute the crop water requirement of field crops in irrigated agriculture.

Technical efficiency indicator for economic sustainability in Koga Irrigation and Watershed Project: Ethiopia

ABSTRACT Economic sustainability is particularly important in agriculture. It is related to the basic economic goal of farmers and the reason for their economic activities. Household-level adaptation and mitigation measures reflect the relative importance of economic goals for sustainability. Researchers collected data via a questionnaire designed to include household demographics, farm-specific variables, inputs, and outputs. The empirical model uses stochastic frontier and technical inefficiency models to analyze economic sustainability. Bered and Teleta were the two most economically sustainable and unsustainable regions. Differences in levels of economic sustainability have been attributed to characteristics that are expected to vary from household to household and from region to region. Output-oriented and input-oriented measures of inefficiency loss show that agriculture can be more economically sustainable as long as it is less efficient. Farmers could expand production with existing inputs, or they could reduce their inputs without lowering production levels. In addition, the return to scale was compared with the growth potential in each region. The political decision makers, therefore, seem to emphasize efforts to improve efficiency instead of investing in new technologies and inputs for the greater economic sustainability of the Koga Irrigation and Watershed Project.

Effect of integrated soil fertility management on hydrophysical soil properties and irrigated wheat production in the upper Blue Nile Basin, Ethiopia

In Ethiopia, soil fertility problem caused by acidity substantially limits agricultural productivity, necessitating sustainable integrated nutrient management. This study assessed the effect of combined application of lime, manure and inorganic fertilizer on selected hydrophysical properties of an acid clay Nitisols in the Koga irrigation scheme, Ethiopia. Five levels of integrated soil fertility management treatments were tested for four consecutive cropping seasons: (i) 0.86 t ha−1 lime combined with 3 t ha−1 manure and full−dose inorganic (urea and NPS−B) fertilizer (L3); (ii) 1.15 t ha−1 lime combined with 3 t ha−1 manure and full−dose inorganic fertilizer (L2); (iii) 1.43 t ha−1 lime combined with 3 t ha−1 manure and full−dose inorganic fertilizer (L1); (iv) 3 t ha−1 manure combined with full−dose inorganic fertilizer (M); and (v) full−dose inorganic fertilizer alone (C) as a control. Undisturbed soil samples were collected at 0–10 and 10–20 cm soil depths and analyzed to determine saturated hydraulic conductivity (Ks), soil−water retention characteristics, total porosity and bulk density. Disturbed soil samples were collected at the same depths to analyze soil organic carbon and texture. Infiltration capacity measurements and visual evaluation of soil structural quality were done in the field. Significantly higher (P < 0.05) soil organic carbon was found at L1, L2, L3 and M compared with C. The application of L1, L2, L3 and M reduced bulk density compared with the C. The amount of water retained at field capacity (FC) was significantly (P < 0.05) affected by the treatments in the order of L1 > L2 > M > L3 > and C for both soil depths 0–10 and 10–20 cm. The Ks under plots treated with L1 was 64% and 37% higher than that of C for the 0–10 and 10–20 soil depths, respectively. Significantly (P < 0.05) higher infiltration capacity was found at L1 (0.007 cm min−1) followed by L2, L3 and M (0.006 cm min−1, 0.006 cm min−1, and 0.005 cm min−1) compared with C (0.004 cm min−1), respectively. Good soil structural quality (Sq) score was identified in L1, L2, L3 and M, whereas in C poor Sq score was found. As compared with C, grain yield was improved by 69% at L1, 59% at L2, 53% at L3, and 44% at M during 2018 and by 70% at L1, 58% at L2, 55% at L3 and 46% at M in 2019. In conclusion, the application of organic manure combined with lime and inorganic fertilizer enhanced the infiltration rate, water holding capacity and grain yield more than the inorganic fertilizer application alone. There was also a significant effect of liming as such, with the highest doses showing the best results.

The dual impact of climate change on irrigation water demand and reservoir performance: a case study of Koga irrigation scheme, Ethiopia

The dual impact of climate change on irrigation water demand and reservoir performance: a case study of Koga irrigation scheme, Ethiopia