Modeling of capillary wick irrigation system for potted plant and small scale plantation

Limited availability of fresh water supplies worldwide demonstrates the urgent need to develop and adopt efficient irrigation methods and proper irrigation management strategies. The relatively high performance of drip irrigation is no doubt. It saves a substantial amount of water and labor, increases yields, and often also improves the quality of the produce. However, the higher investment and energy cost limit the development of the low-cost irrigation system for subsistence farmers. There has been an immense interest in developing and promoting the low-cost drip irrigation system appropriate for small-scale crop growers and greenhouse crop production. This study, by conducting laboratory experiments,investigated hydraulic characteristics and performance of cotton-bonded non-woven material to be used as the wick emitter. Furthermore, greenhouse experiments were carried out to simulate water movement and solute dynamics under root water uptake for potted eggplant crops. To determine proper water application strategies, three irrigation schedules were evaluated. The wick emitter provided the uniformity coefficient of 95.65% and distribution uniformity of 92.67% in applying irrigation in two growing media: peatgro (peat), coconut coir dust and sandy clay loam soil. The growing media and the soil were wetted in an axially symmetric pattern under the wick emitter; in traditional and modern watering methods,growing media are wetted in one-dimensional pattern. HYDRUS simulation of water distribution revealed the dependency of the spatial extent of the wetted zone in the growing media on water application period and hydraulic properties of the media. Furthermore, the results demonstrated that the solutes are transported very slowly, and most of the nutrient solution remains within the middle and bottom of the pots. The results from this study revealed that the eggplant growth showed insignificant differences for the three irrigation schedules when fresh water was used because all the three irrigation schedules provided with enough water content for the crop. In contrast, the eggplant growth showed differences between the treatments relatively when nutrient solutions were used. In terms of wick water application strategies, although 202 ml/day of nutrient solution was applied for the Management Allowed Deficit (MAD) treatment and 155 ml/day was applied for Evapotranspiration (ET) treatment. The total leaf area of the ET schedule (1252.9 cm2) was higher than the total leaf area of the MAD (1007.8 cm2). The result suggests that the ET schedule is the best under wick irrigation. Discharge of the wick emitter followed an inverse linear relation with a capillary height of water in the wick. This relation led to the development of an equation for compensating wick emitter discharge by replacing the pressure head of a drip emitter with capillary height of the wick emitter. The measured water volume found the close match with the simulated water and solute movement using HYDRUS 2D/3D in a container planted with brinjal plant and for various porous mediums. The findings from this study invoke opportunities to develop an effective Capillary Wick Irrigation System (CWS) for small-scale crop production. Further investigation would provide generalized broader evidence on CWS performance based on techno-economical performance of the wick under diverse conditions.

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