The benefits of water-saving techniques such as alternate furrow and deficit irrigations need to be explored to ensure food security for the ever-increasing population within the context of declining availability of irrigation water. In this regard, field experiments were conducted for 2 consecutive dry seasons in the semiarid region of southwestern Ethiopia and investigated the influence of alternate furrow irrigation method with different irrigation levels on the yield, yield components, water use efficiency, and profitability of potato production. The experiment comprised of 3 irrigation methods: (i) conventional furrow irrigation (CFI), (ii) alternate furrow irrigation (AFI), and (iii) fixed furrow irrigation (FFI) combined factorially with 3 irrigation regimes: (i) 100%, (ii) 75%, and (iii) 50% of the potato water requirement (ETC). The experiment was laid out in randomized complete block design replicated thrice. Results revealed that seasonal irrigation water applied in alternate furrows was nearly half (170 mm) of the amount supplied in every furrow (331 mm). Despite the half reduction in the total amount of water, tuber (35.68 t ha−1) and total biomass (44.37 t ha−1) yields of potato in AFI did not significantly differ from CFI (34.84 and 45.35 t ha−1, respectively). Thus, AFI improved WUE by 49% compared to CFI. Irrigating potato using 75% of ETC produced tuber yield of 35.01 t ha−1, which was equivalent with 100% of ETC (35.18 t ha−1). Irrigating alternate furrows using 25% less ETC provided the highest net return of US$74.72 for every unit investment on labor for irrigating potato. In conclusion, irrigating alternate furrows using up to 25% less ETC saved water, provided comparable yield, and enhanced WUE and economic benefit. Therefore, farmers and experts are recommended to make change to AFI with 25% deficit irrigation in the study area and other regions with limited water for potato production to improve economic, environmental, and social performance of their irrigated systems.
Ethiopian farming is mainly dependent on rain-fed smallholder agricultural system. In the absence of sufficient rainfall, there is always low agricultural production, thereby creating food shortage and food insecurity [
Despite the alarmingly increasing population and the great desire to boost production, scarcity of irrigation water has now become the main constraint for crop production particularly in arid and semiarid areas, where evapotranspiration is very high, but the seasonal rainfall is low, erratic, and unreliable for crop production [
Nearly 90% of the irrigated land of the world is watered using the least efficient traditional methods of irrigation [
The water use efficiency (WUE) of CFI could significantly be improved and substantial amount of water saved without significant yield reduction by renovating to alternate furrow irrigation (AFI) technique [
Deficit irrigation (DI) is a practice of water supply by reducing the amount below the optimal level of crop evapotranspiration [
Potato (
In this regard, we hypothesized that the adoption of AFI along with regulated DI techniques would maintain tuber yield, reduce water use, and enhance the WUE of potato production in semiarid areas of Ethiopia, where water resources are scarce. However, the feasibility of both AFI and DI techniques has not yet been well investigated for potato production in the southwestern part of Ethiopia, and the available reports are still limited. In response to this research gap, we conducted field experiments and compared potato grown in AFI with conventional (CFI) and fixed furrow irrigation (FFI) each with 3 levels of irrigation. Thus, the objective of this study was to evaluate the influence of AFI with different irrigation levels on the growth, yield, yield components, water use efficiency, and profitability of potato production in contrast to the conventional (CFI) and fixed furrow irrigation (CFI) methods under the semiarid areas of southwest Ethiopia with limited water resources.
This study was conducted at the farmer’s field in the district of Ziway Dugeda, Arsi Zone (08°00′13.6″ N and 39°01′7.3″ E), which is located in the semiarid climatic region of southwest Ethiopia. The experiment was undertaken during the dry season (December–April) in 2013 and 2014. The elevation at the site was 1689 m above sea level. The major soil type of the study area was classified as Andosol [
There were no weather stations at the study sites. Thus, the New_Loclim: Local Climate Estimator, a public domain software program and database, developed by FAO [
The treatments comprised of 9 combinations of 3 furrow irrigation methods and 3 irrigation levels. The 3 irrigation methods were (i) conventional furrow irrigation, (ii) alternate furrow irrigation, and (iii) fixed furrow irrigation. In CFI, water was supplied to every furrow in every irrigation events. In AFI, water was applied to alternate furrows. However, during the subsequent event, irrigation water was applied to the alternate furrows that had been kept dry during the previous time while leaving previously wet furrows not irrigated. In FFI, irrigation water was supplied to the fixed furrows while the adjacent furrows kept dry from first to last irrigation events. The 3 irrigation levels were (i) 100%, (ii) 75%, and (iii) 50% of the potato water demand. The 3 irrigation methods were combined with the other 3 irrigation levels factorially comprising of a total of 9 treatments as shown in Table
Treatments setting for the field experiment.
Irrigation system | Amount of irrigation water (% ETc) |
---|---|
Alternate furrow irrigation (AFI) | 50 |
Alternate furrow irrigation (AFI) | 75 |
Alternate furrow irrigation (AFI) | 100 |
Fixed furrow irrigation (FFI) | 50 |
Fixed furrow irrigation (FFI) | 75 |
Fixed furrow irrigation (FFI) | 100 |
Conventional furrow irrigation (CFI) | 50 |
Conventional furrow irrigation (CFI) | 75 |
Conventional furrow irrigation (CFI) | 100 |
Note: ETc is the potato seasonal water requirement.
The reference evapotranspiration (ETO) from the potato field was computed employing FAO Penman–Monteith equation [
The total length of the test crop’s growing period in the study area ranged from 120–130 days. The growing period of potato was divided into initial, development, middle, and late stages [
The optimal or “no stress” or 100% ETC treatment was computed using Equation
The experimental sites were properly ploughed, and the clods were pulverized with ox-driven local plough called “
The recommended rates of N (110 kg N ha−1) and P (40 kg P ha−1) for potato in the study area were uniformly applied to all plots from Urea and DAP fertilizers, respectively. All P and half dose of N fertilizers were applied at sowing as basal placement while the remaining half of N was side dressed 1 month later during hilling (earthing up) operation. The experimental plots were always kept free from weeds by manual clearing and hoeing. The Ridomil gold® fungicide was applied against late blight disease of potato. All other agronomic practices were carried out as per the recommendation for potato crop. The potato was manually harvested after physiological maturity on 24 April in 2013 and 12 April in 2014. Thus, the total length of growing period in 2013 and 2014 were 123 and 131 days, respectively, indicating that the later year was a bit longer compared to the former one.
The plots were irrigated through a field canal that conveyed water from the nearby Ketar River through the main canal. The amount of irrigation water supplied to the plots was measured using a 2-inch partial flume. The parshal flume was installed at a levelled surface few meters before the experimental site. The fixed partial flume was aligned straight with the field canal and levelled laterally and longitudinally to allow free flow of water. The water supply to each furrow within each plot was switched off when the time allotted to each furrow ended indicating the delivery of the calculated amount irrigation water to each plot.
The same amount of irrigation water was uniformly supplied to every furrow of each plot regardless of treatment setup few days prior to sowing to establish a favorable seedbed for sowing potato seeds and their germination. Irrigation water was supplied just after sowing to all plots. Another round of irrigation water was also applied 5 days after sowing to make sure that all potato tuber seeds germinated. Thereafter, the irrigation water was applied according to the treatment setup.
Based on the treatments setup, predetermined amounts of irrigation water were usually discharged to each furrow per each crop development stage and irrigation event for predefined periods of time measured through the parshal flume. The flow rate of the parshal flume, which was usually controlled at the outlet of the field canal, was known. Thus, for the CFI, a furrow was irrigated with known volume of water for the duration of predefined period. When the predefined period ended, the inlet of a furrow was closed and irrigation continued until all furrows within the plot were irrigated for the same duration with similar volume of water. However, for the same level of irrigation treatment (e.g., 100% ETC), only half of the available furrows within the plot in FFI and AFI methods were irrigated with half volume of water relative to CFI per irrigation event.
The data collected (computed) during the experimental period were number of tuber per plant, weight of tuber per plant, plant height, total biomass yield, marketable tuber yield, and water use efficiency. The plant height was measured from 10 plant samples from the soil surface to the plant apex at the end of the growing season. Potato tubers were dug out from 5 plant samples, counted, and recorded from each of the sampled potato plants for number and weight of tubers per plant. Just after full physiological maturity and five days prior to harvesting, the haulm of potato was cut and recorded for aboveground biomass yield determination. The marketable potato tubers from the central 2 rows of each plot (7.5 m2; 1.5 m by 5.1 m) were harvested manually, the fresh weight was measured for tuber yield determination and the values were converted to t ha−1 for statistical analysis. The field water use efficiency was calculated by dividing the marketable (economic) potato tuber yield with the total amount of irrigation water applied per treatment and per period as shown in the following equation [
The irrigation water saved with AFI or FFI relative to CFI was calculated using the following equation [
In order to evaluate the comparative advantages of the alternate furrow irrigation method and irrigation levels for potato production, economic analysis was conducted following the procedure of partial budget analysis set by CIMMYT [
The analysis of variance was carried out for all of the measured (computed) parameters following the method described by Gomez and Gomez [
The irrigation methods significantly influenced the entire variables measured for potato except for plant height. The level of irrigation water applied during the cropping season also significantly affected the measured parameters except for the number of tubers per plant and plant height (Table
Combined analysis of variance of potato tuber yield, yield components and water use efficiency for tuber yield as affected by year, irrigation methods (IMs), and irrigation levels (IAs).
Source of variation | No. of tubers plant−1 | Weight of tubers plant−1 (g) | Plant height (cm) | Total biomass yield (t ha−1) | Tuber yield (t ha−1) | WUE (kg m−3) |
---|---|---|---|---|---|---|
Replication | 0.0437 | 0.705 | 0.3183 | 0.6244 | 0.5327 | 0.3355 |
Irrigationmethod (IM) | 0.0075 | 0.0175 | 0.3363 | 0.0114 | 0.0392 | <0.0001 |
Irrigation level (IA) | 0.187 | 0.0251 | 0.4826 | 0.058 | 0.059 | <0.0001 |
IM | 0.7638 | <0.0001 | 0.0347 | 0.9545 | 0.8735 | 0.2976 |
Year | 0.1572 | <0.0001 | 0.0155 | 0.1337 | 0.3262 | 0.1257 |
CV | 20.57 | 22.85 | 5.29 | 21.56 | 26.48 | 25.49 |
Mean | 9.81 | 1000.61 | 59.19 | 42.08 | 33.02 | 173.39 |
LSD | 1.3679 | 155.18 | 2.1207 | 6.1449 | 5.9228 | 24.447 |
Note: WUE is water use efficiency.
The tuber and total biomass yields of potato as well as the weight of tubers per plant were significantly (
Means for the main effects of methods and amount of irrigation water on the yield, yield attributes, and water use efficiency of potato.
Treatments | No. of tubers plant−1 | Total biomass yield (t ha−1) | Tuber yield (t ha−1) | WUE (kg m−3) |
---|---|---|---|---|
Year | ||||
2013 | 7.4b | 31.85b | 27.84b | 141b |
2014 | 12.3a | 52.30a | 38.20a | 206a |
Significance | <0.0001 | <0.0001 | <0.0001 | <0.0001 |
Irrigation methods | ||||
AFI | 9.6b | 44.37a | 35.68a | 224a |
FFI | 8.8b | 36.52b | 28.55b | 186b |
CFI | 11.1a | 45.34a | 34.84a | 110c |
Significance | 0.0075 | 0.0114 | 0.0392 | <0.0001 |
Irrigation levels | ||||
50% | 9.1 | 37.64b | 28.85b | 218a |
75% | 10.3 | 43.67ab | 35.03a | 173b |
100% | 10 | 44.93a | 35.18a | 130c |
Significance | 0.187 | 0.058 | 0.059 | <0.0001 |
Note: AFI, FFI, CFI, and WUE are alternate furrow irrigation, fixed furrow irrigation, conventional furrow irrigation, and water use efficiency, respectively.
Irrigating alternate furrows through partial root drying technique was likely to reduce tuber yield of potato compared to irrigating every furrow [
The nonsignificant tuber and biomass yields difference between AFI and CFI could ascribe to the physiological changes that take place during water stress condition. The plant root system was partially wetted under the AFI and FFI methods, which could reduce plant transpiration because of reduced stomatal conductance [
The maximum number of tubers per potato plant (11) was attained from the CFI, which was superior compared to the other two irrigation methods. Irrigating either fixed or alternate furrows brought statistically similar number of tubers per plant (Table
The effect of the level of irrigation water applied was not significant on the tuber (
When potato, which is among the sensitive crops to drought, is exposed to water stress, it undergoes physiological changes, partially closes its stomata, and suppresses transpiration [
The interaction effect of irrigation methods by level of irrigation water was significant (
Weight of potato tubers (a) and plant height of potato (b) as affected by the interaction effect of irrigation method by water level.
The measured yield and yield attributes of potato were highly significant (
Owing to variations in the applied irrigation water, the seasonal crop water use differed among treatment means. The total depth of irrigation water supplied to each plot treated with CFI, AFI, and FFI was 331.3, 169.5, and 165.1 mm, respectively. This indicated that the plots treated with AFI consumed approximately half the volume of irrigation water, which saved irrigation water by 49% without significant yield loss compared to the plots under CFI. Although the highest volume of reduction in irrigation water (50%) was achieved with FFI, the tuber yield reduction was significant (23%) (Table
The amount of irrigation water saved, tuber yield reduction, and relative water use efficiency with different irrigation methods and amounts.
Treatments | Irrigation amount (mm ha−1) | Tuber yield (t ha−1) | WUE (kg m−3) | Water saved (%) | Yield reduction (%) | Relative WUE | |
---|---|---|---|---|---|---|---|
Irrigation method | Irrigation level (%) | ||||||
AFI | 50 | 113.03 | 31.65 | 28.06 | 74 | 18 | 3.2 |
75 | 169.54 | 37.96 | 22.49 | 62 | 1 | 2.6 | |
100 | 226.06 | 37.42 | 16.58 | 49 | 3 | 1.9 | |
FFI | 50 | 110.08 | 26.54 | 24.31 | 75 | 31 | 2.8 |
75 | 165.12 | 29.39 | 17.99 | 63 | 23 | 2.1 | |
100 | 220.17 | 29.72 | 13.59 | 50 | 23 | 1.6 | |
CFI | 50 | 220.85 | 28.35 | 12.9 | 50 | 26 | 1.5 |
75 | 331.28 | 37.75 | 11.41 | 25 | 2 | 1.3 | |
100 | 441.71 | 38.41 | 8.73 | 0 | 0 | 1.0 | |
The irrigation methods brought highly significant (
The increased WUE of potato with AFI ascribed to the reduced amount of irrigation water without significant reduction in potato tuber yield. The current result is in agreement with Khalili et al. [
The amount of irrigation water applied during the cropping season highly significantly (
The WUE of potato was significantly (
The methods and levels of irrigation water had great influence on profitability of potato production (Table
Economic analysis based on mean values for potato production for the use of different irrigation methods and levels of irrigation water on potato production.
Treatments | Adjusted tuber yield (kg ha−1) | Gross field benefits (US$ ha−1) | Variable cost (US$ ha−1) | Net benefit (US$ ha−1) | Marginal rate of return | |
---|---|---|---|---|---|---|
Irrigation method | Irrigation level (%) | |||||
AFI | 50 | 28485 | 12947.73 | 68.18 | 12879.55 | — |
FFI | 50 | 23886 | 10857.27 | 68.18 | 10789.09 | D |
AFI | 75 | 34164 | 15529.09 | 102.27 | 15426.82 | 74.72 |
FFI | 75 | 26451 | 12023.18 | 102.27 | 11920.91 | D |
AFI | 100 | 33678 | 15308.18 | 136.36 | 15171.82 | D |
FFI | 100 | 26748 | 12158.18 | 136.36 | 12021.82 | D |
CFI | 50 | 25515 | 11597.73 | 136.36 | 11461.36 | D |
CFI | 75 | 33975 | 15443.18 | 204.55 | 15238.64 | D |
CFI | 100 | 34569 | 15713.18 | 272.73 | 15440.45 | 0.2 |
Note: D means dominated due the greater variable cost but lower net benefit.
In line with this study, Sarker et al. [
The sensitivity analysis with the possible higher price for the labor cost confirmed that the MRR was above 100% suggesting that the same recommendation could still work well. If the price of labor cost increase by 30% within the coming 3 years, farmers who can alternately irrigate furrows using 75% of the potato water requirement earn additional US$57.25 for every US$1.0 investment on labor for irrigation.
Results of our field study demonstrated that potato yield, yield attributes, and water use efficiency (WUE) were significantly influenced by irrigation method and level. Irrigating alternate furrows (AFI) consumed approximately half the volume of irrigation water relative to conventional furrow irrigation (CFI). AFI provided the highest tuber yield regardless of the reduction in the total volume of irrigation water, which was found statistically equivalent to the tuber yield harvested from irrigating every furrow techniques. Thus, irrigating alternate furrows resulted in 49% higher WUE without significant yield decline. Reducing the potato water demand by 25% enhanced the WUE by 33% with equivalent tuber yield to the application of 100% of the potato water requirement. Furthermore, irrigating alternate furrows with 25% reduced potato water requirement gave the highest net return of US$74.72 for every US$1.0 investment on labor for irrigating the potato plant. The authors of this study, therefore, concluded that irrigating alternate furrows in conjunction with 25% less the potato water demand saved irrigation water, increased water use efficiency without compromising tuber yield, and enhanced economic return for farmers in semiarid areas. Adoption of this technique suggests the great potential of doubling the cultivable land and production using the existing irrigation water resource by shifting from the conventional to water-saving irrigation method. Adoption of the water-saving irrigation methods further helps to minimize the adverse effects of excess irrigation to the environments and the conflicts among the community for the limited water resource.
The data used to support the findings of this study are available from the corresponding author upon request.
The authors declare that they have no conflicts of interest regarding the publication of this paper.
The authors would like to thank the Kulumsa Agricultural Research Center for the provision of logistics for the execution of this research activity. The authors would like to acknowledge all members of the Land and Water Resources research division for their efforts in land, crop, and data management during the conduct of this study. This research was financially supported by the Ethiopian Institute of Agricultural Research.