Irrigation Schedules and Crop Water Requirements for Some Main Crops in Saudi Arabia

: The Food and Agriculture Organization (FAO) CROPWAT 8.0 standard software and the CLIMWAT 2.0 tool affixed to it have been utilized in this study for Qassim Region of Saudi Arabia to find CWRs and irrigation plans for numerous extremely valuable crops of KSA. We were used CROPWAT P. M. method for find out the ETo and (USAD) S. C. method utilized to determine roughly effective rainfall. The analysis demonstrated that ETo change over from 2.84 mm/day in January to reach maximum 9.61 mm/day in July due to high temperature in summer with annual mean was 6.33 mm/day, effective rainfall changes from 0 mm to 53.4 mm. The total IWRs were 308.3 mm/dec, 335.9 mm/dec, 343.6 mm/dec, 853 mm/dec and 1479.6 mm/dec for Barley, Wheat, Maize, Rice and Citrus, respectively. Due to low demand in winter and high demand in summer, the total net irrigation and total gross irrigations are 210.6 mm and 147.4 mm, 176.6 mm and 123.6 mm, 204.5 mm and 143.2 mm, 163.9 mm and 114.7mm for Wheat, Barley, Citrus, and Maize respectively except rice crop. These results showed that Wheat, Barley, Citrus, Maize and Rice crops have 4, 4, 12, 4 and 12 irrigation schedules respectively in a year.


Introduction
The agricultural development of Wheat, Rice, Maize, Citrus and Barley in Saudi Arabia stand facing enormous challenges, which are average of arid areas described with water shortage, low precipitation, and above average evapotranspiration requirement. Greatest of irrigation water is acquired from groundwater storage capacity. The farming segment expended more than 85% of water ingesting, which achieved more than 23 billion m 3 in 2012 see [1]. An efficient and precise assessment of CWR is necessary for preparing, constructing, operational, controlling farm systems due to rise the demand of water with time. Precise assessment of CWR can assist to sustain costeffective utilization of water reserves for irrigation. Evapotranspiration (ET) performs a most important part in sustainability of irrigation water [2].
CROPWAT model can perform a valuable part in improving useful suggestions for enhancing yield production beneath circumstances of sparse water resource [3]. It permits the expansion of suggestions for improved irrigation practices, the planning of irrigation timetables beneath differing water allocation requirements, and the estimation of production under rainfed circumstances or shortfall irrigation. The approximately the yield decline triggered by water pressure and climatical effects. The simulation results study recommends that in both situation rainfed and watered, the major yield decline happened in the developmental stage [4].
CROPWAT and CLIMWAT software's are used by many researchers for the estimation of CWR, and irrigation pattern and preparation. These tools were built by the Food and Agriculture Organization (FAO) for assistance researchers in water irrigation investigations and irrigation sustainability [7]. In the current analysis, the irrigation water requirements and irrigation scheduling of a few chosen crops (Rice, Maize, Citrus and Barley, Wheat) in Qassim region, Saudi Arabia were investigated using the CLIMWAT and CROPWAT models.

Materials and Methodology 2.1.Study Area
The Al -Qassim Province (Region) is located at the heart of the Saudi Arabia, geographically center of Arabian Peninsula. The total population of this region is 1370727 and total area of this region is 58046Km 2 . This region is an agricultural asset of Saudi Arabia. The average Maximum and Minimum temperature of this region is 31.4 °C and 16.5°C in 2019. The average humidity, wind and sunshine of this region are 30 %, 238 Km/day and 8.1 per hour, respectively. The latitude and longitude of Qassim region are 26°30'N and 43°76'E with altitude is 650m. The average rainfall of Qassim region is 183 mm [5,15,16].

Reference Evapotranspiration (ETo)
The ETo gradually increase from nearly 2.84 mm/day in January to the highest worth of approximately 9.61 mm/day in Jul. Then it again declines steadily to 2.97 mm/day in December as shown in table 1 and 3D figure 1. The maximum ETo rises from 5.26 to 6.98 mm/day in April. The average yearly ETo was 6.33mm/day in 2019. The effective rainfall as shown in table 1 and figure 2. The maximum effective rainfall was 53.4 mm in November 2019, although it was zero in June to September and between 4mm -37 mm in the other months of year 2019. The total twelve-monthly effective rainfall was expected to be 172.3 mm. There are many methods to calculate the effective rainfall but in this study, we use USAD S. C. method.

Crop Water Requirement (CWR) of Rice, Wheat, Citrus, Maize (Grain) and Barley
The crop water essential is the quantity (or depth) of water that equals the water loss by ET. Crops have distinct water needs varying on the agriculture technique, effective rain, location, atmosphere, land type, etc., and the overall water necessary for crop development is not equally disseminated over its entire life span [6].
Evaluation of CWRs is obtained from crop evapotranspiration ( ) and reference evapotranspiration ( ) which can be analyzed by the following relation [7]: where called crop, coefficient introduced by [8]is the ratio of the and . This coefficient incorporates the impacts of four necessary measures that distinguish the crop from reference grass, and it covers reflectance of the soil surface, height evaporation from soil and resistance canopy.
The crop coefficient will vary due to effect at different stages of growth: initial, development, mid-season, and late see [2,9].
The values of different months by using CROPWAT software as shown in table 1 and figure2.

Results and Discussion
The data entered CROPWET and CLIMWAT software included the country (Saudi Arabia), Climatic station (Al-Qassim region), name of crop, sowing and harvesting time, soil information (Black Clay Soil). Once all data entered in system, we calculate ETo by using Penman-Monteith method [11,12] and effective rainfall by using USDA S. C. method. Details results as shown in

3.1.Corp Pattern/Schedule and Net Irrigation Requirement (NIR)
Understanding of crop IWRs and ITS enhances IM in the ground. Irrigation water management is about optimize the rate of irrigation, amount and timing and rate of irrigation in an cost-effective and organized manner. Mathematically NIR is define as:

= −
This sort of assessment facilitates the agriculturalists to prefer the type of crops for growing on the based of availability of water [13] The          In figure 3 to figure 7, the total water available to the crop is denoted by (TAM) and RAM is the part of the water available to the crop that plant can get from the root zone and red line in graph shows the depletion. [14] The production of these four crops in the province represents an insignificant percentage of the total KSA production and, consequently, there is an important requirement to modernize agricultural and irrigation practices for the intention of boosting production. Irrigation structure transformation supports innovative practices such as spraying and trickle irrigation with prominence on essential yields, water accessibility and topsoil value. An essential component is to increase understanding amongst agriculturalists about the necessity to protect water and use of innovative practices.  Table 17 shows the total area and total production see [17].

Conclusion
The