Triq H Karim’s scientific contributions

Water is one of the most precious and heavily scrutinized natural resources on the global scale, particularly in Iraqi Kurdistan region with limited water resources. Innovative irrigation solutions must tackle the water shortage problems affecting these regions. Drip irrigation plays a major role in reducing the water losses, expanding the irrigated area, and improving crop productivity. Designing an efficient drip irrigation system requires detailed information on wetting patterns under a single emitter. The wetting pattern dimensions should be well- defined in order to attain good matching between these dimensions and the spacing between emitters and laterals as well as the rooting depth. Accordingly, the current study was initiated with the main objectives of identifying the dynamics and distribution of wetting pattern under drip irrigation, predicting wetting area dimensions from soil properties, as well as the system hydraulic properties besides conducting a field experiment to evaluate different emitter spacing in term of Zucchini productivity. Before initiating field tests, several tours were made in the outskirts of Erbil city to select 24 sites to cover a wide spectrum of soil properties. Three laterals were installed at each site and provisions were made to install three emitters at a spacing of 2 m on each lateral. Prior to large scale field testing, three additional sites have been utilized for determining the time required for the wetted diameter to reach the equilibrium state. Thereafter, field tests were conducted at the remaining sites for measuring the ultimate dimensions of the wetting volume. Three discharge rates were applied such that each line represented a discharge level. To monitor soil moisture distribution in horizontal and vertical directions, soil samples were also obtained on two orthogonal lines passing through the center VII of the wetting area at 5 positions on each line and at several depths below each position using a small auger for water content determination. After termination of the experiment, composite disturbed soil samples were obtained from different depths for performing some selected soil physical and chemical analysis. The shape of wetting pattern was also captured under different discharges from a tank filled with the soil of Girdarasha site. Following the study of wetting pattern at different site, a factorial experiment was conducted at Girdarasha site using three replicates to evaluate three emitter spacing (50, 60 and 70 cm) and three emitter discharges ( 1.9, 3 and 4 l hr-1) and the interaction between them in term of marketable yield, dry matter yield and water use efficiency of Zucchini. The main results can be summarized as follows: A- Surface Wetting Pattern 1. It was observed that the values of wetted diameter tend to increase rapidly with time initially then increased at a decreasing rate to limit the diameter to nearly a constant value. 2. For a fixed time of application, there is a steady increase in wetted diameter with an increase in emitter discharge. 3. The effect of increasing time on increasing the wetted radius vanishes after about 25 to 45 hours. 4. In most of the cases, the growth model attributed more than 92% of variation in wetted diameter to variation in time. VIII B. Water Distribution around Emitters 5. The water content contour and the wetting pattern are nearly ellipsoidal in shape around the emitters. 6. The soil water content, around the emitter tended to increase in both vertical and horizontal directions with the increasing emitter discharge at the equilibrium state. 7. As opposed to the author expectation the coarser textured soils gave rise to a wider wetting area compared with finer textured soils. C. Wetted Pattern Modeling 8. It also observed that the emitter discharge offered the highest correlation coefficient with wetted diameter (r = 0.547) followed by clay content and saturated hydraulic conductivity. 9. Among the three variable models, the model with emitter discharge (Q), clay content (C) and saturated hydraulic conductivity as regressors offered the highest performance for predicting the surface wetted diameter (D). 10. Among the non- linear models, the model with emitter discharge (Q), clay content (C) and saturated hydraulic conductivity (Ks), bulk density (BD) and initial water content (i) as input variables offered the highest performance for predicting the surface wetted diameter (D). 11. The input variables of the Schwartzman and Zur (1986) model, which included emitter discharge, wetted depth and saturated hydraulic conductivity explained only 40% of variation in D. The mean absolute percentage of error of prediction of the wetted diameter from this model exceeded 30%. IX D. Field (Biological) Experiment 12. The highest Zucchini fruit yield was recorded at a spacing of 60 cm with a discharge of 3 l hr-1. By contrast, the treatment combination of L3 = 70 cm and Q = 3 l hr1 offered the lowest yield. 13. With no exception, under any of the applied discharges, the spacing of 60 cm offered the highest marketable yield. Also, like the fruit yield, the highest dry matter yield was recorded under the emitter spacing of 60 cm under all applied discharges. 14. The highest irrigation water use efficiency of 10.63 k gm-3 for Zucchini was obtained from a spacing of 60 cm with an emitter discharge of 3 l hr-1. 15. Zucchini fruit yield and the irrigation water use efficiency were very high significantly (P  0.01) affected by the emitter spacing and the interaction between spacing and discharge. Conversely, it was observed that none of fruit yield and dry matter yield and water use efficiency was affected statistically by the emitter discharge.

Water shortage has been and will continue to be a key global-scale threat to agricultural production. One approach to mitigate the intensity this problem is the efficient use of water and this necessitates introduction of high efficient irrigation systems like drip irrigation. Reliable information about the dimensions of wetted soil under drip irrigation enables designers to find out optimal emitter flow rates and spacing to offer efficient use of irrigation water. Accordingly, the current study was initiated and the main objectives were to predict the ultimate diameter of wetting area under emitters from dripper discharge and other properties of the dominant soils in Erbil plain. To achieve the above objective 24 sites were selected over the indicated plain keeping in mind covering a wide spectrum of soil properties. At each site the soil moisture distribution in horizontal and vertical directions were monitored under three drip discharges of 1.2, 2.5 and 3.5 l hr-1 such that each line represented a discharge level. The results indicated that among a host of input variable, emitter discharge, soil clay content and saturated hydraulic conductivity were the most influential factor affecting the maximal diameter of the wetted area (D). A linear and a nonlinear model were also derived for predicting the maximal diameter of the wetted area (D). The mean absolute percentage errors were 10.37 and 8.57 % respectively. Similarly, a linear model was proposed for predicting the wetting depth with a reasonable accuracy. Additionally, the results also confirmed that the model proposed by Schwartzman and Zur, (1986) had poor predictability for estimating D in the area under study.