Impact of Evaluation of Different Irrigation Methods with Sensor System on Water Consumptive Use and Water Use Efficiency for Maize Yield

The sensor system is one of the modern and important methods of irrigation management in arid and semi-arid areas, which is water as the limiting factor for crop production. The study was applied for 2016 and 2017 seasons out in Al-Yousifya, 15 km Southwest of Baghdad. A study was conducted to evaluate coefficient uniformity, uniformity distribution and application efficiency for furrow, surface drip and subsurface drip irrigation methods and it was (98, 97 and 89)% and (97, 96 and 88)% for 2016 and 2017 seasons; respectively. And control the volumetric moisture content according to the rhizosphere depth for depths of 10, 20 and 30 cm by means of the sensor system. The results indicated that the height consumptive water use of furrow 707.91 and 689.69 mm∙season and the lowest for subsurface drip with emitter deep at 20 cm 313.93 and 293.50 mm∙season for 2016 and 2017 seasons; respectively. As well, the highest value of water use efficiency for subsurface in drip irrigation at a depth of 20 cm, was 2.71 and 2.99 kg∙m and the lowest value for furrow irrigation was 1.12 and 1.20 kg∙m for the 2016 and 2017 seasons; respectively.


Introduction
In recent years, farmers in developed countries have tended to use modern irrigation methods, and these methods have become widely used in arid and semi-arid areas where water is a limiting factor due to a water deficit. And those modern methods of irrigating crops can increase the soil's water-holding capacity, increase its permeability, reduce water lost to surface runoff and secure the water needs of plants [1]. Sub-surface drip irrigation is a method suitable for irrigation frequently in arid and semi-arid soils because it provides the best control of irrigation water and prepares the water near the rhizosphere of the plant if it is well managed and it is at a high level of control and leads to high crop productivity [2] and [3].
Irrigation efficiency is used to evaluate the application of the irrigation system and measure the efficiency of the water applied to the field in the root zone, which is used by the plant, and it indicates the suitability of the irrigation method used. And the irrigation efficiency was defined from [4] as the ratio of the water stored in the rhizosphere to the water applied to the field Amounts of water are greater than the soil's ability to hold, which causes water losses through deep permeation and runoff.
In general, irrigation efficiency for most well designed surface irrigation methods reaches 60%, while in sprinkler irrigation it reaches 75%, and it may reach 95% in surface and subsurface drip irrigation. Raising the irrigation efficiency is related to reducing water losses and increasing the amount of water stored in the rhizosphere, and this is related to achieving a balance between all the variables affecting the irrigation system (settlement and good management of the field and determining the appropriate slope and drainage and the appropriate field area) [5].
Also an appropriate amount of water sufficient to fill the rhizosphere with water to the limits of its field capacity greatly affects the efficiency of irrigation.
Water must be added at a rate commensurate with the rate of infiltration into the soil. In general, the efficiency of irrigation decreases by increasing the amount of water applied during the irrigation. low irrigation (little amounts of water) are not enough to fill the rhizosphere, which makes the irrigation process not good, despite the high irrigation efficiency, and this may be reflected in production.
The irrigation efficiency is affected by the type of soil, the irrigation method used, the amount of water applied, the porosity of the soil, and the time of irrigation [6] and [7]. Nowadays it has become necessary to use modern technologies in agriculture, management and scheduling of the irrigation process, the most important of these techniques is the sensor system that facilitates the monitoring and determination of the appropriate quantity and timing of irrigation, and that increase water productivity and crop productivity [8]. This study aims to evaluate irrigation methods using standards (application efficiency, uniformity distribution, coefficient uniformity and the lowest proportion of variance ) using several pressures, determine the best pressure in irrigation, control volumetric T. Thamer et al. Journal of Water Resource and Protection moisture content by using the sensor system, and determine the best irrigation method for water productivity and maize crop productivity in the central region of Iraq.

Material and Methods
The study was conducted in 2016 and 2017 at al-Yousifya, 15 km southwest of Baghdad-Iraq (44˚18'75"E and 33˚07'84"N, 34 m elevation above sea level Figure   1 on a silt clay (classified as Typic-Torriflovent). The climate in the middle Iraq is arid-semi arid. It is characterized by warm weather and minimal rainfall during the summer (the crop growing season). The weather data of Al-Yousifya Region is taken from Al-Raeed weather station which is located 5 km away from the experimental site. Typical measurements are illustrated in Figure 2.

Soil Sampling Analysis
The soil moisture release curve was estimated at, 33, 100, 500, 1000 and 1500 kPa for samples taken from depths of (0 -30 cm) and (30 -60 cm). Soil available water content was calculated from differences in moisture content at 33 and 1500 kPa according to [9] Table 1.

Experimental Design and Treatments
The experiment was laid out according to a Completely Randomized Block     2) Surface drip irrigation (I 1 ).

5) Sub-surface drip emitters at 30 cm depth (I 4 ).
The experimental design and treatments were illustrated in Figure 4.
Evaluation of Drip Irrigation System Calibration of drip system emitter discharge was done every 20 minute period by placing four cylinders (1000 ml) in any experimental unit distributed in four locations, one for any quarter. The evaluation of the system was done under three pressures 100, 150 and 200 kPa. The following calibration parameters were measured: a) Emitters Coefficient uniformity. b) Emitters Distribution uniformity. c) Proportion of Variance conjugations emitters. d) Application Efficiency.
The second parameter was distribution uniformity using the following equation [11]: where: Du(1/4) = Uniformity Distribution for the lowest quarter (%). Diq = Average water depths for the lowest quarter. Dac = Average total water depths.
The proportion of variance conjugations emitters also measured using following equation [12]: q Net = proportion of variance conjugations emitters (%). q max = highest discharge (h /L). q min = less discharge (h /L).
The application efficiency for drip irrigation methods measured using following equation [13]: where: Ea = application efficiency (%). e = the total numbers of emitters. q min = minimum emitter flow rate. T = total irrigation time. V = total amount of water applied.
The application efficiency for furrow irrigation method measured using following equation [14]: where: NDI = Net depth of irrigation (mm). GDI = Gross depth of irrigation (mm).

Sensor System
The Sensor System Decagon devices were installed in the field are consisted of two data loggers type Em 50, the data was recorded by the computer, each of data loggers connected to five sensors type 5TE and GS3. The sensors were installed at three depths, (10, 20 and 30 cm) for two replicates. Data loggers record volumetric moisture content, temperature and EC of soil every one hour and then the data is saved onto a computer. Data Trac3 program was used to identify and sensors data graph, as it connects the computer with the Em50 Data Logger. Then the program transfers and converts the data format stored in the Em50 Data Logger's memory to another format that Data Trac3 deals with. The ports of sensors were distributed according to irrigation treatments as follows: 1) Furrow irrigation (I 0 ) = P1.

Irrigation Treatments and Management
Irrigation treatments consisted mainly of furrow irrigation. The plots of this treatment were initially irrigated by surface irrigation because they were planted in rows in flat plots. Thirty days after sowing, the furrows were done between plant rows using a furrowing machine. The irrigation was applied by tube system with valves and flow meter to measure the amount of water applied to each experimental unit of this treatment. The surface and subsurface drip irrigation were done using drip irrigation system (Ro-drip). Irrigation scheduling was done according to the depletion of soil moisture content at three soil depths (0 -10, 10 -20 and 20 -30 cm) depending on the sensor system. Thus, when 50% of the available water was depleted, irrigation was done. Soil moisture content was calculated according to the following equation [15]: where: d = depth of water applied (mm). fc θ = Volumetric water content at field capacity (cm 3 •cm −3 ). w θ = Volumetric water content before irrigation (cm 3 •cm −3 ). D = Soil depth to be wetted at irrigation.
The water amount which was applied to experimental treatments by drip irrigation system calculated according to the following equation [14]: where: NDI = Net Irrigation Depth. RZD = Rhizosphere Depth. WHC = Water bearing Capacity (mm of water•cm −1 ). Pd = Percent of depletion. Pw = Percent of wetting.
Water consumptive use (evaporation) of the crop was measured by using the following water balance equation [16]: I = irrigation (mm). P = precipitation (mm). C = capillaries (mm). ET a = actual evapotranspiration (mm). D = deep percolation (mm). R = rune off (mm). Δs = changes in the water storage during soil profile.

Results and Discussion
Evaluation of irrigation methods As well as for the subsurface drip irrigation Figure 6 the highest values were   so it is necessary to provide suitable moisture at this stage, these results was consistent with [24].
The lowest moisture content in surface drip irrigation I 1 treatment P2 were    the sunlight radiation increases accordingly as evaporation; and hence, water losses resulting from surface run-off and deep percolation, as well as due to the low efficiency of the addition, and then it was reported between 67% and 65% for furrow irrigation treatment and between 96% and 95% for the subsurface drip irrigation treatments and between 89% and 88% for surface drip irrigation for the 2016 and 2017 seasons; respectively. This has been shown in Figure 8 and Figure 9. This reveals the demand to add more water to reach the soil moisture to the field capacity and requirements of plant. Previous studies have indicated that subsurface drip irrigation reduces the amount of water applied Journal of Water Resource and Protection between 30% and 60% compared with traditional methods.
Subsurface drip irrigation is characterized by direct contact with the rhizosphere and its distribution of water has two directions, vertically and horizontally by capillary action, which gives a more possibility for water to spread through the rhizosphere in addition to its advantage in that it is not directly exposed to sunlight radiation. This in turn reduces evaporation process and its impact. Also, soil particles and the different pores have an effect on consumptive use that enhanced by high temperatures in the growing months. This also led to an increase in water evaporation from the soil surface shown in Figure 2, as indicated by the results in the different values of consumptive use for the 2016 season; it was higher than that of 2017 season in all treatments. These results were agreed by [29] [30] and [31].
Grain Yield and Water Use Efficiency WUE: The increase in Water Use Efficiency (WUE ) for I 3 treatment as shown in Figure 12) was due to the increase in the grain yield, which reached to 8.   yield to increase water use efficiency. Such results have been agreed by [32] and [33].
The lack of sufficient moisture content in roots' area and the exposure of the plant to water stress, is reflected in the processes of cell expansion and division, and in the processes of decrease length stem and leaf growth, and the area of carbon assimilation as well as leaf area and leaf area index decrease. There is also the ability of the plant to transfer the products of assimilation among parts of the plant, where it has been noticed a decrease grain yield with low amounts of irrigation water and different treatments, which resulted in decrease in water use efficiency. These results have been agreed with [34] and [35].
The decrease in WUE for the I 0 irrigation treatment, which amounted between 1.12 and 1.20 kg•m −3 for the two seasons 2016 and 2017; respectively, was attributed to the increase in consumptive use of this treatment compared to other treatments, as shown in Figure 10 and Figure 11 for the 2016 and 2017 seasons; respectively. This caused a decrease in the WUE, although the result was close to the treatment of subsurface drip irrigation I 3 , as it was shown in Figure   12 for the 2016 and 2017 seasons; respectively.
The increasing in WUE depends on what can be reduced from the amount of water given to the crop without affecting the amount of yield produced. These results were agreed by [36] [37] and [38].

Conclusions
1) It is necessary to evaluate the irrigation methods used in irrigating crops to know the efficiency of the coefficient uniformity (%) of water, uniformity Distribution (%), proportion of variance and the application efficiency (%) of applied water for different irrigation methods, where it was found that the subsurface drip irrigation gave the highest application efficiency, uniformity distribution and coefficient uniformity were 97%, 99% and 96% and 98%, 98% and 95%; respectively and the lowest proportion of variance were 8.8% and 9.8% for 2016 and 2017 seasons; respectively.
2) Observation of the volumetric moisture content of different irrigation methods through the sensing system, placing the sensors in the rhizosphere, and scheduling irrigation by knowing the time and quantity of irrigation according to the needs of the plant throughout the growing season.
3) Popularization of the subsurface drip irrigation system and adopting a depth of 20 cm, which gave the least amount of applied water and water consumption Journal of Water Resource and Protection and the highest productivity and efficiency in water use compared to furrow irrigation and surface drip irrigation, which are affected by climatic conditions from high temperatures and low humidity during the maize growing season in central regions of Iraq.