Wind Drift Evaporation Loss and Soil Moisture Distribution under Sprinkler Irrigated Blackgram (Vigna mungo L.)

An experiment was conducted during March–June 2018 with the sprinkler irrigation system covered in an area of 39×42 m2. Proper design and management of sprinkler irrigation systems improves the uniformity of moisture distribution and reduces wind drift and evaporation losses (WDEL) for effective crop growth. Uniformity coefficient, wind drift and evaporation loss of the sprinkler system at a different pressure head of 2 kg cm-2, 2.5 kg cm-2 and 3 kg cm-2 were studied. Wind speed was observed by using handheld anemometer. The wind speed ranged between 0.9 to 4.5 m s-1. The highest uniformity coefficient of 88.19% and wind drift and evaporation loss of 3.5% were obtained at the pressure head of 3 kg cm-2 and the wind speed of 0.9 m s-1. Soil samples were collected at different depths of 0–10 cm, 10–20 cm, 20–30 cm and at a radial distance from 0 m, 3 m, 6 m, 9 m, 12 m respectively to determine the soil moisture distribution pattern. The soil moisture content values were plotted by using the computer software, surfer 10 of the windows version and contour maps were drawn. The moisture content was found to be more at 0–10 cm depth, as compared to 10–20 cm and 20–30 cm depth. The percentage of moisture was found to be highest at a 6 m distance, which was due to overlapping of the sprinkler system.

Soil Water Stable Isotopes Reveal Surface Soil Evaporation Loss Dynamics in a Subtropical Forest Plantation

Line-conditioned excess (lc-excess), the deviation of the relationship between δD and δ18O in soil water from that of precipitation, is often used to indicate soil evaporation loss, but the conditions of using lc-excess under the influences of precipitation infiltration or percolation had not been identified. The interaction effects of climate, soil and vegetation on soil evaporation in forests are not well known. We collected soil water at 0–5, 15–20 and 40–45 cm depths and event-based precipitation from 2011 to 2015 in a subtropical forest plantation and calculated the lc-excess. Precipitation on the sampling day and percolation of upper soil water with low lc-excess affected the capacity of the lc-excess to indicate the soil evaporation fractionation signals. Lc-excess of soil water at 0–5 cm depth indicated a reliable soil evaporation loss estimate over 30 days prior to the sampling day. Soil evaporation loss was dominated by the cumulative soil temperature (Tss) during drought periods and was dominated by the relative soil water content (RSWC) during non-drought periods. High Tss decreased soil evaporation loss by increasing transpiration and relative humidity. Our results emphasize the importance of sampling the upper-most soil layer when there is no rain and vegetation during drought periods in forests when studying soil evaporation loss dynamics.

DESIGN, CONSTRUCTION AND EVALUATION OF RUNOFF WATER HARVESTING POND FOR SMALLHOLDER FARMING

Rainfall shortage and variability constrain crop production of smallholder farmers in Ethiopia is the main problem. For this supplementary irrigation by run off harvesting is strategic pathway to reduce poverty in rural drought prone areas for enhancing agricultural productivity and boosting farm income. For this, this study is conducted to Design, construction and evaluation of runoff water harvesting Pond for supplementary irrigation to addressing inherent crop failures under the rain fed agriculture due to mainly erratic rainfall. For this design climatic and soil data were input to determine seasonal crop water requirement (CWR) of onion and evaporation loss of water from water surface. Then the performances of water harvested verses area irrigate were evaluated. To make this study more economical the water harvester capacity decreed by two fold and water harvesting made at two times. Seasonal volume crop water requirement (CWR) of onion for farm area 2500 m2 and evaporation loss of water from water surface of 121 m2 and total volume of seasonal water need were 382.05,53.38 and 435.43 m3 respectively. The geo-membrane laminated water harvester that has capacity of 223 m3 was designed and constructed. From on field performance shows, this volume of water harvested twice can irrigate 0.25ha by supplementary irrigation using water saving irrigation technology (treadle pump) by over showering and was produced 4.2 tone/ha. The investment, operation and production costs were 63116, 1125 and 6675 ETH birr respectively. The total cost was 70,916 birr and The growth return of 0.25ha was 15,750 birr/year (1050kg*15 birr/kg). This show the farmer can return 22.21% of their investment cost. So it is recommended to the government and non-government to initiate the farmers at lower stream of the catchment to harvest run off water and use for supplementary irrigation to increase their income.

Superhydrophobic Sands for the Preservation and Purification of Water

Sand, a cheap and naturally abundant particulate material, was modified with photocatalytic and hydrophobic coatings to reduce evaporation loss and facilitate the purification of water. The first-level photocatalytic coatings (TiO2 or ZnO nanocrystals) rendered nanoscale roughness on the surface of the sand. The additional second-level hydrophobic coating of a self-assembled monolayer of octyltrimethoxysilane (OTS) made the sand particles superhydrophobic because of the nanoscale roughness imposed by the nanocrystals. The superhydrophobic sand particles, floating on the free surface of water due to their superhydrophobicity, significantly reduced the evaporation loss of water by 60%–90% in comparison to an uncovered water surface. When the outer hydrophobic coatings are weathered or disengaged, the inner photocatalytic coatings become exposed to water. Then, the sand particles act as photocatalysts to degrade the contaminants in water under solar radiation.