English abstract
In Oman, like other arid-zone countries, there is a growing need for a thrifty and efficient usage of water resources for agriculture due to water scarcity. One of the approaches to achieve such a goal in saving water is to use capillary barriers (CB), CB occurs at the interface of two soil layers having distinct textural and hydraulic characteristic. In this study, a "nature-inspired capillary barrier design" called hereafter as Smart Capillary Barrier (SCB) was mimicked in a soil column. Specific objectives of this study were to investigate the effect of (i) changing sand to silt loam ratio of the SCB to enhance water storage capacity of the surrounding fine textured (silt loam) soil of the blocks and (ii) using different sand to silt loam proportions of the SCB on the growth of an okra [Abelmoschus esculentus (L.) Moench) and the soil microbial count under deficit irrigation conditions. Three proportions of sand to silt loam soil on a volume basis were used in this study including 25:75%, 50:50% and 75:25%. Soil column experiments were conducted using okra plant at the Agriculture Experimental Station (AES), Sultan Qaboos University, Oman, during the period from October 2016 to March 2017 in an open field. Furthermore, the efficiency of SCB in conserving water was validated by pot experiments that were conducted on June 2017. The results of both column and pot experiments showed that the SCB treatments conserve more water than the control treatments (i.e, without SCB). In addition, the water storage of the blocks varied greatly depending on the different sand to silt loam soil ratios used in SCB. Columns with SCB stored 10 to 14% more water compared to those without SCB having the same sand to silt loam soil proportion. SCB having 75:25% of sand to silt loam soil proportion was more efficient in conserving water inside the blocks even under deficit irrigation conditions. Results showed that SCB with 75:25% sand to silt loam soil had up to 11% and 16% more soil moisture content than 25:75% sand to silt loam soil in both column and pot experiments, respectively. However, using SCB with different sand to silt loam soil proportions had no significant effect on plant growth and soil microbial counts over the experimental period, in spite of the variation in soil moisture content. The results of this study concluded that SCB is a promising technique that has great potential to save irrigation water in arid areas.
