A. M. Abu-Awwad

Infiltration rate measurements in arid soils with surface crust

Abstract The effects of infiltrometer type and water application rate on infiltration were studied for a crust-forming soil at the University of Jordan Research Station near Al-Muwaqqar village. The total amount of water applied in all cases was 38 mm. The highest infiltration rate values occurred in basin infiltrometers followed by sprinkler and furrow infiltrometers. The infiltration rate at the end of water application decreased significantly by 41–57% with decreasing application rate from 28.4 to 6.2 mm/h regardless of infiltrometer type. Increasing the initial soil moisture content decreased the infiltration rate by about 4–11% in all infiltrometer types and application rates. In the basin infiltrometer, lateral water movement occurred all around the basin borders, thus increasing the measured basic infiltration rate. In the furrow infiltrometer, the formation of a sedimentary crust on the furrow bottom reduced the basic water infiltration rate to 3.6 mm/h. The wetted zone formed with the sprinkler infiltrometer reduced lateral water movement, and the measured basic infiltration rate was close to the basic infiltration rate measured by the double-ring infiltrometer. The measurements were used to establish infiltration rate curves and equations. In a second experiment, the Stirk correction significantly reduced the water lateral divergence factor by 27.1% in single-ring infiltrometers. The Stirk correction factor was different in single- and double-ring infiltrometers. Thus, the basic infiltration rate was 4.8 and 3.5 mm/h using the single and the double infiltrometers, respectively, while the corresponding correction factors were 0.67 and 0.91, respectively. The corrected infiltration rate was only 3.2 mm/h, which confirms the tendency of these crusted soils to generate huge runoff at even small application rates.

Influence of different water quantities and qualities on lemon trees and soil salt distribution at the Jordan Valley

Abstract The influences of water quantity and quality on young lemon trees (Eureka) were studied at the University of Jordan Research Station at the Jordan Valley for 5 years (1996–2000). Five water levels and three water qualities were imposed via trickle irrigation system on clay loam soil. The primary effect of excess salinity is that it renders less water available to plants although some is still present in the root zone. Lemon trees water requirements should be modified year by year since planting according to the percentage shaded area, and this will lead into substantial water saving. Both evaporation from class A pan and the percentage shaded area can be used to give a satisfactory estimate of the lemon trees water requirement at the different growth stages. The highest lemon fruit yield was at irrigation water depth equal to evaporation depth from class A pan when corrected for tree canopy percentage area. Increasing irrigation water salinity 3.7 times increased average crop root zone salinity by about 3.8–4.1 times. The high salt concentration at the soil surface is due to high evaporation rate from wetted areas and the nature of soil water distribution associated with drip irrigation system. Then, the salt concentration decreased until the second depth, thereafter, salt concentration followed the bulb shape of the wetted soil volume under trickle irrigation. Irrigation water salinity is very important factor that should be managed with limited (deficit) irrigation. But increasing amount of applied saline water could result in a negative effect on crop yield and environment such as increasing average crop root zone salinity, nutrient leaching, water logging, increasing the drainage water load of salinity which might pollute ground water and other water sources.

Effects of sand column, furrow and supplemental irrigation on agricultural production in an arid environment

Abstract The effects of supplemental irrigation, sand columns and blocked furrows on soil water distribution and barley yield were studied on arid soils affected by surface crusts. The sand columns were 50 mm diameter, 600 mm deep, and filled with sand of 0.375 mm mean diameter. The blocked furrows were trenches about 250 mm deep, 300 mm wide, and 6 m long established perpendicular to the slope direction. Sand column and furrow treatments significantly increased soil water storage compared with natural or control treatments. Soil water storage significantly increased by about 210% and 230% near the center of the sand column and the furrow treatments, respectively, relative to the control treatment. For sand column treatments, soil water storage decreased linearly with distance from the center of the sand column to about 2.5 m, while for the furrow treatment soil water storage decreased logarithmically to a distance of about 1.0 m, beyond which the soil water storage was not significantly different from the natural or control treatments. The furrow and sand column treatments significantly increased the water application efficiency, seasonal consumptive use and barley grain and straw yields compared with natural and control treatments. Increasing furrow spacing increased the catchment area and consequently crop production per furrow, but decreased crop production per unit total (cultivated and catchment) area. Decreasing sand column spacing reduced surface runoff and increased soil water storage and consequently barley grain and straw yields. Supplemental irrigation is essential for grain production in limited rainfall areas. Soil management is also required to overcome the problems of the soil surface crusting and the low permeability of subsurface soil layers for maximum rainwater efficiency, and for optimal crop production with minimum supplemental irrigation water. Where agricultural land is not limited, furrowed soil surfaces appear to be the most suitable technique for barley grain production. Sand columns with sprinkler irrigation might be more suitable for growing barley as forage crop where agricultural land is limited.

Influence of vertical sand column and supplemental irrigation on barley yield in arid soils affected by surface crust

Abstract A field experiment was conducted during the 1996/1997 season at the University of Jordan Research Station near Al-Muwaqqar village to investigate the effects of sand columns, sand column spacing, soil ridges, and supplemental irrigation on soil water storage, redistribution, and barley yields. The experimental site represents a typical Jordanian arid environmental soil suffering from surface crust formation overlaying impermeable material. In the 600-mm-depth soil profile, soil water storage was improved significantly by 59%, 45%, and 38% in the 1-m, 2-m, and 3-m sand column spacing treatments, respectively, compared with soil water storage in the control treatment (no sand columns). Sand columns increased the moisture stored in all four soil layers (0–150, 150–300, 300–450, and 450–600 mm). Moisture stored in the 450–600 mm soil layer increased significantly by about 188%, 147%, 88%, and 29% in the 1-m, 2-m, 3-m, and 4-m sand column spacing treatments, respectively, compared with moisture stored in the same soil layer of the control treatment. Increasing soil water storage also increased barley consumptive use significantly from 130 mm in the control treatment to an average of about 185 mm in sand column treatments. Without supplemental irrigation, barley grain and straw yields were negligible and almost zero. Barley yields in the control treatment, with 167 mm supplemental irrigation were low, being 0.19 ton/ha and 1.09 ton/ha of barley grain and straw, respectively. Sand columns increased barley grain and straw yields significantly compared with the control treatment to a maximum of 0.68 ton/ha and 3.97 ton/ha, respectively, with the 1-m sand column spacing. Soil ridges perpendicular to the land slope had no significant effect on increasing soil water storage due to lateral runoff and loss along the ridge. In general, sand columns minimize surface runoff and evaporation by allowing water to infiltration through the strong surface crust. Sand columns act as a sink for surface water, enhance subsurface lateral water movement, and reduce the possibility of surface crust formation in the vicinity of the sand column opening by preventing surface ponding.

Soil Surface Wetting Pattern under Trickle Source in Arid Lands: Badia Regions

Arid regions are characterized by fragile soils that differ in behavior according to their physical and chemical compositions. In this study, the wetted soil surface area was measured for four different soil types to assess the impact of the individual soil particles (silt, sand and clay separates) on soil surface wetting area, under different application rates using point source trickle irrigation. Three flow rates were tested 4, 8 and 12 liters per hour (Lph) on four different soil types (silt loam, loam, sandy loam58sand and sandy loam77sand). Soil surface wetted area increases as emitter flow rate increases. The results showed that increasing emitter flow rate from 4 to 8 and to 12 Lph, increased soil surface wetted area by about 60 and 160%, respectively. Soil surface wetted areas in loam soil and silt loam soils were 1.5 and 2.8 times that in sandy loam soils, respectively. Soil surface wetted area increases rapidly with time initially, but then increases at a decreasing rate, until the application rate became in equilibrium with soil infiltration rate. The surface wetted area had good correlation with the percentages of silt, sand and clay soil particles, with regression correlation ranging from 0.90 to 0.97. The trends were increased wetting with clay and silt and decreased wetting with sand. The expected losses on the form of evaporation in arid soils suffering from surface crust, therefore, would increase in soils dominated by silt or clay when compared with sand, indicating that cropping pattern in arid environments should be carefully selected in areas with scarce water resources.

Reuse of Treated Municipal Wastewater with Drip Irrigation in Jordan

Water resources in The Hashemite Kingdom of Jordan are limited in both quantity and quality. As such the Government of Jordan in cooperation with USAID and CDM International has been exploring the potential of reusing water for industrial, agricultural and landscaping purposes. The project is called “Reuse in Industry, Agriculture and Landscape (RIAL). This paper presents findings on the four sites currently operating that are all in agricultural and/or landscaping projects. All sites use treated municipal wastewater for irrigation, and have a demonstration component. The current focus is on the sustainability of these projects when sponsorship of these projects ceases. Due to water reuse regulations in Jordan that strictly limit sprinkler irrigation, drip and subsurface irrigation systems were installed. Drip tubing and fittings are manufactured domestically and local contractors installed the systems. The reuse water receives secondary treatment and chlorination, and is filtered with sand and disk filtration prior to distribution. A wide variety of crops-including fodder and grain crops and fruit trees – as well as landscape plants and turf are irrigated with the treated wastewater. Sites are located in both rural and urban areas, and one is located at the Jordan University of Science and Technology (JUST). Filtration system maintenance varies with treated wastewater quality and filtration design, and emitter clogging has been a problem at one site due initially to improper system operation and poor treated water quality; planned treatment plant upgrade should remedy this. Part of the RIAL project has included the development of sustainability plans, addressing financial, marketing, environmental and technical aspects of the reuse sites in the future. The project is also working with stakeholders and government to address and formulate national policy on the role of reuse in Jordan.