Experimental Evaluations of CROPWAT8 Irrigation Scheduling for Hot Pepper and WUE Through on-Farm Participatory Approaches, Northwest Ethiopia

Irrigation scheduling is a critical management input to ensure adequate soil moisture for optimum plant growth, yield, quality, water use efficiency, and economic return. Besides farmer irrigation practice including irrigation scheduling in Northwest Ethiopia is cultural. The objective of this study was to evaluate CROPWAT irrigation scheduling for hot pepper and water use efficiency through on-farm participatory approaches Northwest Ethiopia. The experiment was conducted at two sites in Awi Zone, Dangela district (Ligaba) and Jawe district (Wobomariam), Northwest Ethiopia for two consecutive years 2017 and 2018. The experimental design was used a paired ‘t’ design it compares the effects of CROPWAT8 irrigation scheduling versus farmer's irrigation practice under both the furrow irrigation system. From January to May irrigation season gross irrigation depth for hot pepper considering field irrigation application efficiency of 60% was 466.4 and 720.2 for Ligaba and Wobomariam site respectively. The paired ‘t’ analysis revealed that water use efficiency and hot pepper fresh yield were significantly increased under the CROPWAT8 irrigation scheduling practice as compared with farmers irrigation practice. Hot pepper water use efficiency was improved by 43.7% and 9%%, and hot pepper fresh yield was improved by 12% and 31.4% for Ligaba (high land) and Wobomariam (low Land) areas of Northwest Ethiopia. In addition to this participant farmers and stakeholders also evaluate CROPWAT irrigation scheduling positively it could be used locality conditions. This shows the CROPWAT8 irrigation scheduling has increased significant benefits (proper water usage and hot pepper fresh yield increment). We conclude that the CROPWAT irrigation scheduling system is a promising technology to estimate crop water and irrigation water requirements with when and how much irrigate to corresponding growth stage. And also, that can improve hot pepper fresh yield of small-scale irrigation in Northwest Ethiopia.


Introduction
Small-scale irrigation is recognized as a policy priority in Ethiopia for the reduction of poverty [1] and climate adaptation [2]. Irrigated agriculture is becoming increasingly important in meeting the demands of food security, employment, and poverty reduction [3]. Irrigation scheduling is a critical management input to ensure adequate soil moisture for optimum plant growth, yield, quality, water use efficiency, and economic return [4]. The irrigation schedule which determines the timing and amount of irrigation water is governed by many complex factors, but microclimate plays the most vital role [5][6][7]. Therefore, it is important to develop irrigation scheduling techniques under prevailing vital conditions to utilize scarce and expensive water efficiently and effectively for crop production. Irrigation scheduling is planning when and how much water to apply to maintain healthy plant growth during the growing season [8,9]. Proper irrigation scheduling is a means for optimizing agricultural production and conserving water [10]. The goal of irrigation scheduling is to control the water status of the crop to achieve a targeted level of agronomic performance. The performance level can vary from optimizing irrigation input to optimizing the output where crop yield is maximized [11]. Irrigation scheduling is the use of water management strategies to prevent over-application of water while minimizing yield loss due to water shortage or drought stress. The efficiency of water use in agriculture is low with poor management and improper designs of water application systems [12]. High water loss results in lesser yield and reduced irrigated areas that are linked to ineffective water use. But the improved irrigation practices lead to more uniform water distribution, minimize water application, irrigation costs, nutrient leaching, and result in the economic viability of irrigated agriculture [13,14]. However, in Ethiopia traditionally anyone understood that irrigating more water for the crops means getting more yield. Although that is true for some water-loving crops, like rice, that is not good for most crops, where the root zone is found at a certain depth under the soil. The water below the root zone of the plant is not available. If it happened, causes the leaching of an essential nutrient, increasing in the groundwater table (cause water lodging), and increase in salt content over the land surface [15]. Several studies were carried out in the past on the development and evaluation of irrigation scheduling techniques under a wide range of irrigation systems and management, soil crop and climate conditions. Among those, FAO-CROPWAT (version 8.0) irrigation water management computer simulation model was selected because of previous tests and satisfactory performance in number of worldwide locations under varying climate circumstances [16].
Hot pepper is among the most susceptible horticultural plants to drought stress because of the wide range of transpiring leaf surface and high stomatal conductance [17] and having a shallow root system [18]. For high yields, and adequate water supply relatively moist soils are required during each growing season [13,19]. Hot pepper cultivation is known in warm and semi-arid countries including Ethiopia. In Ethiopia hot pepper is a high-value cash crop that is used in many ways as well as food [20]. However, farmers still practice traditional irrigation in Northwest Ethiopia's high land and low land areas Such as Dangela and Jawe districts is low productivity. For such condition, well managed and scheduled irrigation practice with respective crop stage is very necessary. The irrigator needs knowledge of the efficient use of water resources through different crop management practices and irrigation scheduling techniques. These farmers traditional irrigation practice needs improved technology with a demonstration for farmer's participatory approach. So, the objectives of this study were (1) To determine hot pepper crop water, irrigation requirement and irrigation scheduling, (2) To evaluate the experimental effects of CROPWAT irrigation scheduling compared to farmer's practice on crop and water productivity in Northwest Ethiopia.

Study Area
The field experiment was conducted at two sites in Awi Zone, Amhara region, Northwest Ethiopia. Ligaba Keble small scale irrigation scheme, Awi zone, high lands of Ethiopia, and Wobomariam Keble small scale irrigation scheme, Awi zone, law lands of Ethiopia ( Figure 1). The area locates 2014 m and 1120 m above mean sea for Ligaba and Wobomariam irrigation scheme respectively. The areas where there is unlimited water resource through smallholder farmers (the communities) to maximize production and intensity by growing crops during dry seasons.

Experimental Design and Setup
A series of discussions were made with the local government, water users association leaders and agricultural development agents. The discussion aimed to locate the sites and select participant farmers. From discussions based on their interest, five farmers were selected to set the experiment and 50 farmers also to see each activity selected for each site. The experimental design was used a paired 't' design it compares the effects of CROPWAT 8 irrigation scheduling versus farmer's irrigation practice under both the furrow irrigation system (Figure 2). The Paired 't' test, a parametric procedure, is useful for testing whether the means of two groups are different, where the samples were drawn in pairs. The test is testing whether the mean of the differences of the pairs is different from zero. Paired 't' is mathematically powerful to compare two paired measurements, which have intrinsic relationships, and do not require a large sample size which allows good control of individual differences [21]. De Winter [22] proved the applicability of paired t-test as low as two replicates. Several studies including. Yimam, Assefa [23], Belay, Assefa [24], and Assefa, Jha [25] have used paired-t design for similar purposes. In this experiment, irrigation scheduling with CROPWAT is the treatment and farmers' irrigation practice is the control (Figure 2). Experimental plots were assigned randomly for each management (i.e., Irrigation scheduling versus farmers watering practice).
The experimental setup was conducted in two consecutive years of 2017 and 2018 on a 200 m 2 plot; where half of this size was assigned to irrigation scheduling (100 m 2 ) and another half to farmers irrigation scheduling practice (100 m 2 ) randomly.

Climate Data
Long term climatic data (maximum and minimum temperature, wind speed, sunshine hour, relative humidity) were collected from the nearby meteorological station, Dangela for the Ligaba site, and Pawe for Wobomariam site. The CROPWAT 8 model was used to estimate the reference evapotranspiration (ETo) using the Penman-Monteith method [26] (Table 1) and (Table 2) respectively. Mean monthly ETo reaches its maximum value in April (137.44 mm/month in Dangela Ligaba site and 161 mm/month in Jawe wobomariam site) and mean monthly minimum evapotranspiration reaches in July (91.15 mm/month in Dangela Ligaba keble and 106.23 mm/month in Jawe Wobomariam) as shown in (Figure 3).

Rainfall Data
The same to climate data for both site's long-term monthly rainfall data 16 years for Ligaba site and 29 years for Wobomariam site were collected. Effective rainfall (Pe) was determined using the United States Department of Agriculture Soil Conservation Service (USDA-SCS) method [27] and [16] as shown in (Equation 1). The effective rainfall was used later to determine water productivity for each crop under both irrigated and rainfed systems.
Mean monthly rainfall reaches its maximum value in August (390.5 mm in Dangela Ligaba site and 396.3 mm in Jawe Wobomariam site), and monthly effective rainfall starts April to November for Ligaba site and April to October for Wobomariam site ( Figure 3) Where Pe and P are effective rainfall and precipitation in mm/month, respectively.

Soil Data
In both experimental sites, randomly three sampling plots were selected. For each sampling plot three samples from 0 to 30 cm, 30 to 60 cm, and 60 to 90 cm total of 15 samples were taken. The samples were analyzed for different soil physical properties like field capacity, permanent wilting point and soil texture in the Pawe agricultural research soil laboratory.

Crop Water Determination
Crop water requirement refers to the amount of water that needs to be supplied, while crop evapotranspiration refers to the amount of water that is lost through evapotranspiration [16]. For the determination of crop water requirement, the effect of climate on crop water requirement, which is the reference crop evapotranspiration (ETo) and the effect of crop characteristics (Kc) are important [28]. Maximum effective root zone depth (Rz) of hot pepper ranges between 0.5-1 m and has allowable soil water depletion fraction (P) of 0.25 [29]. Hot Pepper average Kc would be taken after adjustments have been made for initial, mid and late season stage to be 0.6, 1.05 and 0.95, respectively [16] The long term and daily climate data such as maximum and minimum air temperature, relative humidity, wind speed, sunshine hours, and rainfall data of the study area were collected to determine reference evapotranspiration, crop data like crop coefficient, growing season and development stage, effective root depth, critical depletion factor of hot pepper and maximum infiltration rate and total available water of the soil was determined to calculate crop water requirement using CROPWAT model Where: ETc, ETo and Kc are crop evapotranspiration, reference evapotranspiration and crop coefficient respectively.

Irrigation Water Requirements
Water requirement of hot pepper was determined from climate data acquired from the regional metrological station by using CROPWAT 8.0 model. Gross irrigation depth was estimated considering field irrigation application efficiency of 60%. Accordingly, net irrigation depths, gross irrigation depth and time of watering based on fixed irrigation intervals for each growth stages.
The total available water (TAW), stored in a unit volume of soil was determined by the expression Hot Pepper and WUE Through on-Farm Participatory Approaches, Northwest Ethiopia The depth of irrigation supplied at any time can be obtained from the equation The gross irrigation requirement also obtained from the expression 6778 = 9:; <= (5) Where: Irrg, IRn and Ea are gross depth of water applied (mm), Net irrigation depth and Water application efficiency of the furrows (60%) respectively.
Water use efficiency The water use efficiency was calculated by dividing harvested yield in kg per unit volume of water used in mm [13]. Water use efficiency (WUE): The crop water use efficiency is the yield harvested in kg per ha-mm of total water used.
Where: WUE, Y and Etc. are crop water uses efficiency (kg/ha-mm), Yield in kg ha-1 and Crop evapotranspiration (mm) respectively.

Farmers Perception About Experiment
Field day was implemented with farmers and stakeholders' farmers were evaluating the experiment, farmers irrigation scheduling practice versus CROPWAT irrigation scheduling. The farmers compare the experiment for their own perception at different aspects i.e amounts of watering with crop growth stage, when and how much irrigate and obtained yield farmers irrigation practice compared to irrigation scheduling.

Irrigation and Water Application System
Furrow irrigation system was used for both irrigation scheduling versus farmers irrigation scheduling practice. In farmer's irrigation scheduling practice, the farmers use a traditional irrigation scheduling system underwater management to plant or transplant the hot pepper. Whereas in irrigation scheduling practice, we use the CROPWAT version 8 model to calculate irrigation water requirement and irrigation scheduling for hot pepper. According to Smith [8] crop growing stage with criterion classifications of hot pepper has four stages (Table 3). For each stage crop water requirement and irrigation scheduling were done. Parshall flume two-inch throat width was used to measuring irrigation water for both irrigation scheduling and farmers' irrigation scheduling practice. The water discharge measured with partial flume. For each irrigation, the amounts of watering date and amount of watering were recorded in both farmer's irrigation practice and technology irrigation scheduling practice.

Crop Parameter Data
A data collection system was developed for appropriate data analysis using paired 't' statistics. For both sites, Pepper (marko fan) variety was cultivated two consecutive years in the 2017 and 2018 dry season. For pepper production recommended spacing is 30 cm between plants and 70 cm between row was used [30,31]. Farmers applied Urea (46: N) fertilizer at a rate of 100 kg ha-1 for irrigated pepper. Crop characteristics such as plant height and crop yield were recorded. Plant height was monitored at harvesting. The measuring tape was used to measure plant height. The digital balance was used to determine the weight of the fresh yield of pepper.

Reference Evapotranspiration, Effective Rainfall and Irrigation Seasons for Study Area
The CROPWAT was used to inputs of long-term climate and rainfall monthly data the simulation were reference evapotranspiration and effective rainfall ( Table 1, Table 2 and  Table 3). Each month ET o values differences is reflect the variation in weather parameters in the study area. The low relative humidity, high temperatures, and high wind increased the evapotranspiration during the dry seasons [32,33]. The distributions of each month reference evapotranspiration and effective rainfall was used to separate rainfall cropping season and irrigation cropping seasons. So, from the obtained result in both sites showed that rainfall cropping season partially high effective rainfall and low ET o were observed. and also, in irrigation season showed reverse of rainfall cropping season (Figure 3). From this obtained result we suggested that in both sites May end to October first is fully rain fall cropping season and October end to May first is irrigation cropping season. Based on this this experiment was starting from January to ending in May for both sites were implemented.

Soil Properties in Experimental Site
At the surface average composition of sand, silt and clay percentages were 19%, 35.5% and 45.5%, respectively for ligaba and 42%, 20% and 38 % respectively for Wobomariam site (Table 4). Thus, according to the USDA soil textural classification the experimental site soil was classified as clay and clay loam for ligaba site and Wobomariam experimental site respectively. From 0 to 90 cm soil depth water holding capacity of Ligaba soil experimental area showed between 0.13 to 0.15 cm/cm whereas in wobomariam site water holding capacity is 0.12 cm/cm of soil with depth is similar. And also, the average soil bulk density (1.28 g/cm 3 ) is below the critical threshold level (1.4 g/cm 3 ) and was suitable for crop root growth [34].

Crop Water Requirement, Irrigation Water Requirement and Irrigation Scheduling for Hot Pepper
Crop water requirements (CWR) encompass the total amount of water used in evapotranspiration [35]. Water requirement of hot pepper was determined from climate data acquired from the regional metrological station Dangela and Pawe by using CROPWAT 8.0 model (equation 2). The ETc values were observed to be low at initial stage and high at mid stage that showed Kc value is increase with growth stages and back to at late stage. The CWR for hot pepper was higher during the mid and late season growth stages and lower during the initial and developmental stages. Studies the Kc varied little, it was not constant in any growth stage; this also expresses the seasonal crop water needs [32,36]. The seasonal water requirements of hot pepper for each study area shows 462.7 mm and 532.2 for Dangela ligaba and Jawe Wobomariam site respectively. Effective rainfall is the part of rainfall which is effectively used by the crop after losses by surface runoff and deep filtration; it is used to evaluate the CWR [32]. The observed effective rainfall was 70.  Once the crop water and irrigation requirements have been calculated, the next step is the preparation of field irrigation schedules [35]. Gross irrigation depth was estimated considering field irrigation application efficiency of 60% were 466.4 and 720.2 for Ligaba and Wobomariam site respectively. As Shown (Table 7), for both sites at initial stage irrigation interval was short with little amount of irrigation water was applied. The rest stage development, mid and late stage were long irrigation interval with high amounts of water was observed. For Ligaba site the observed irrigation interval was (4, 5, 5, 6, 6), (7,7,8,8), (8,9,9,9,9) and (0) with respective gross irrigation water requirements for initial, development, mid and late season stage respectively. Similarly, for Wobomariam site the irrigation interval was (4,4,5,5,5), (6,6,6,7,7), (7,7,7,7,7,8) and (12) with respective gross irrigation water requirements for initial, development, mid and late season stage respectively. In other words, 5, 4, 5 and 0 times have been irrigated for initial, development, mid and late season stage respectively for Ligaba site and 5, 5, 6 and 1 times were irrigated for initial, development, mid and late season stage respectively for Wobomariam site. In this study similar crops but different gross irrigation water requirement, irrigation interval and irrigation frequency were observed. The difference might be different agroclimatic condition and different soil type. Agroclimatic conditions of Ligaba site is located high land area, relatively low temperature, minimum sunshine hour, high humidity and better effective rainfall was showed. Whereas in wobomariam located in low land parts, high temperature area, high sunshine hour, low humidity and low effective rainfall was showed. In addition to this soil class of ligaba was heavy clay and wobomariam was clay loam. Those reason is coming different gross water requirements. Studies for similar crop has at different climate condition and soil type different water requirement and gross irrigation water requirement [13,14], Allen, Pereira [16], [29,32]. Not, Net Irr and Gr. Irr are net irrigation and gross irrigation respectively.

Effects of Irrigation Scheduling Versus Farmers Irrigation Practice for Each Growth Stage
In these two consecutive irrigation seasons study, each applied water was recorded in both farmers irrigation scheduling practice and CROPWAT irrigation scheduling practices. As shown Table 8 Whereas, Farmers given water to crops only accomplishment of water it also almost similar amount of water from initial stage to late stage. Farmers was applied minimum and maximum irrigation water respectively were 25 mm at initial stage and 43 mm at development stage for 2017 and 32 mm at initial stage and 47 mm at mid stage for 2018 under Ligaba conditions. For wobomariam minimum and maximum water applied respectively 19 mm at mid stage and 58 mm at initial stage for 2017 and also 2018, 17.8 mm and 41.9 mm at initial stage were applied. Those applied water tells us farmers not know when and how much irrigate to crops. This undulating water application system affects the yield of hot pepper.

Effects of Applied Irrigation Water Between Farmers Versus CROPWAT Irrigation Scheduling
The mean total applied water to hot pepper were CROPWAT irrigation practice was lower than farmers irrigation practice at Ligaba site. Whereas in Wobomariam site CROPWAT irrigation scheduling was more than farmers irrigation practice ( Figure 5) (Table 9). In the case of Ligaba the total applied water was 503.6, 642 and 466.2 mm for 2017 farmers irrigation practice, 2018 farmers irrigation practice and CROPWAT irrigation scheduling respectively. Whereas in the case of wobomariam site 612, 528 and 720.2 mm for 2017 farmers irrigation practice, 2018 farmers irrigation practice and CROPWAT irrigation scheduling respectively.
The mean water uses of 2017 and 2018 farmers practice were used additional, respectively, by 8% and 37.7%, when compared to CROPWAT irrigation scheduling at ligaba site. Whereas in Wobomariam site farmers irrigation practice 2017 and 2018 respectively withhold 17.6% and 36.4% when compared to CROPWAT irrigation. This study shown that farmers for different location have different indigenous knowledge. This study agrees with studies for farmer-tofarmer irrigation trend is not similar [24].

Effects of CROPWAT Irrigation Scheduling on Crop Water Use Efficiency and Yield
For Ligaba site analyzed result shows that the highest WUE was obtained in 2017 (34 kg/ha mm, 28 kg/ha mm) and in 2018 (33 kg/ha mm, 23 kg/ha mm) were CROPWAT irrigation scheduling and farmers irrigation practice respectively. Whereas, for Wobomariam site the result revealed that (24 kg/ha mm, 22 kg/ha mm) and in 2018 (25 kg/ha mm, 27 kg/ha mm) were CROPWAT irrigation scheduling and farmers irrigation practice respectively (Table  9). This result improves CROPWAT8 irrigation scheduling for hot pepper WUE increasing to 43.7% and 9% for Ligaba site and Wobomariam site respectively as compared with wfarmers irrigation practice. It is commonly said that improving irrigation efficiencies is of paramount importance under water scarce situations because high efficiency would represent conditions of near-optimal use of the water. This is generally true when the idea behind is that less water should be abstracted from surface or ground waters to produce a certain yield. Nevertheless, in an area where water is fully available, it is important to consider the deep percolation and runoff loss. The results of this research are in agreement with GENÇOĞLAN and YAZAR [37], [38] who reported that WUE values decreased with increasing irrigation level. A one-tailed paired t-test was used to analyze the impacts of fresh hot pepper yield for CROPWAT irrigation scheduling system to farmers irrigation practice. From this the obtained result shows that there was a significant different in 2017 for both sites and in 2018 for wobomariam site. Whereas in Ligaba site non-significant in 2018 between irrigation scheduling and farmers irrigation practice ( Table 9).
The mean crop yields of the fresh hot pepper were increased by 12% and 3.4% for 2017 and 2018 respectively at Ligaba site and 31.4 %, and 25.8% at Wobomariam site respectively under irrigation scheduling when compared with farmers irrigation practice. According to Dorji, Behboudian [20] who reports hot pepper yield affected by deficit irrigation level. So, this study shows similar yield effects. Note. WUE, CV, NS, * and ** are water use efficiency, coefficients of variation, non-significance difference, significance difference and highly significance difference respectively.

Comparative Evaluations of CROPWAT Irrigation Scheduling Versus Farmers Practice on Field by Participants
For both sites field day was implemented with farmers and stakeholders' farmers were evaluating the experiment, farmers irrigation practice versus CROPWAT irrigation scheduling. According to focus group discussions farmers feedback were thoughtful about cultivated crops for irrigation needs simple technical knowledge. This technical system was amounts of irrigation water depends on crop growth stage and when and how much irrigate is used to obtained optimum crop yield. In addition to this participant researcher and Development agriculture (DA) also evaluates simple computer programming CROPWAT irrigation scheduling system is important for locality climate conditions crop water requirements and irrigation water requirements.

Conclusion and Recommendation
This research showed the potential benefits of CROPWAT irrigation scheduling simple computer program compared to farmers irrigation practice on farm conditions under small scale irrigation system in Northwest Ethiopia. The applicability of CROPWAT irrigation scheduling system was experimentally demonstrated to estimate hot pepper irrigation water requirement with when and how much irrigating as well as growth stage. From January to May irrigation season gross irrigation depth for hot pepper considering field irrigation application efficiency of 60% was 466.4 and 720.2 for Ligaba and Wobomariam site respectively.
Water use efficiency and hot pepper fresh yield were significantly increased under the CROPWAT8 irrigation scheduling as compared with farmers irrigation practice. Hot pepper water use efficiency was improved by 43.7% and 9% and hot pepper fresh yield was improved by 12% and 31.4% for Ligaba (high land) and Wobomariam (low Land) North west Ethiopia respectively. In addition to this participant farmers and stakeholders also evaluate CROPWAT irrigation scheduling positively it could be used locality conditions. This shows the CROPWAT irrigation scheduling has increased significant benefits (proper water usage and hot pepper yield increment). We conclude that the CROPWAT irrigation scheduling system is a promising technology to estimate crop water and irrigation water requirements with when and how much irrigate to corresponding growth stage. And also, that can improve hot pepper fresh yield of smallscale irrigation in Northwest Ethiopia.

Conflicts of Interest
The authors declare no conflict of interest.