Polyacrylamide polymer (PAM) effect on the propagation of the wetting front on a Jordanian soil under trickle irrigation system

Numerous studies have been conducted to examine the efficiency of PAM in controlling soil erosion under surface irrigation; however, there are fewer studies that have examined the effect of PAM on soil-water relations. This trickle irrigation laboratory study on a Jordanian clay loam soil addressed the effect of PAM on the spreading of the wetting front. PAM was added to the irrigation water under a trickle irrigation experiment where we irrigated the soil for 30 min. Four PAM concentrations (0.0, 5.0, 10.0, and 20.0 mg l^?1) were used to examine its effect on the wetting front propagation in the soil. We also examined the effect of PAM on the soil water content, where we irrigated for 45 min, using two concentrations of PAM, 0.0 and 20.0 mg l^?1. The soil water content was measured at depths of 0.0, 5.0, 10.0, 15.0, and 20.0 cm, 4 h, 24 h, and one week after completion of irrigation. PAM's effect on the soil water characteristic curve was studied using PAM concentrations of 0.0, 25, 50, and 100 mg l^?1. In this study the spread of the wetting front on the soil surface and in the vertical and horizontal directions inside the soil profile increased when PAM was added to the irrigation water. As the PAM concentration increased the spreading of the wetting front increased. The average wetting front spreading increased in the vertical direction from 7.8 cm when PAM was not used to 8.3, 9.6, and 12.1 cm, for PAM concentrations of 5.0, 10.0, and 20.0 mg l^?1, respectively. At the same time the average increase in the horizontal direction was from 18.4 to 18.5, 18.6, and 21.7 cm for PAM concentrations of 0.0, 5.0, 10.0, and 20.0 mg l^?1, respectively. The second experiment showed that at a soil depth of 20 cm, volumetric soil water content (θv) was 15.2% when the irrigation water contained 20.0 mg l^?1 of PAM compared to 13.9% when no PAM was added to the irrigation water. PAM did not have a significant effect on soil moisture characteristic curve.     

The Effect of Late-terminal Drought Stress on Yield Components of Four Barley Cultivars

Barley (Hordeum vulgare L.) is an important winter cereal crop grown in the semiarid Mediterranean, where late‐terminal drought stress during grain filling has recently become more common. The objectives of this study were to investigate the growth performance and grain yield of four barley cultivars under late‐terminal drought stress under both glasshouse and field conditions. At grain filling, four barley cultivars (Rum, ACSAD176, Athroh and Yarmouk) were exposed to three watering treatments: (1) well‐watered [soil maintained at 75 % field capacity (FC)], (2) mild drought stress at 50 % FC, (3) severe drought stress at 25 % FC in the glasshouse experiment and (1) well‐watered (irrigated once a week), (2) mild drought (irrigated once every 2 weeks), (3) severe drought (non‐irrigated; rainfed) in the field. As drought stress severity increased, gross photosynthetic rate, water potential, plant height, grain filling duration, spike number per plant, grain number per spike, 1000‐grain weight, straw yield, grain yield and harvest index decreased. In the glasshouse experiment, the six‐row barley cultivars (Rum, ACSAD176, and Athroh) had higher grain yield than the two‐row barley cultivar (Yarmouk), but the difference was not significant among the six‐row cultivars under all treatments. In the field experiment, Rum had the highest grain yield among all cultivars under the mild drought stress treatment. The two‐row cultivar (Yarmouk) had the lowest grain yield. In general, the traditional cultivar Rum had either similar or higher grain yield than the other three cultivars under all treatments. However, the yield response to drought differed between the cultivars. Those, Rum and ACSAD176, that were capable of maintaining a higher proportion of their spikes and grains per spike during drought also maintained a higher proportion of their yield compared with those in well‐watered treatment. In conclusion, cultivar differences in grain yield were related to spike number per plant and grain number per spike, but not days to heading or grain filling duration.     

Determination of actual evapotranspiration and crop coefficients of broad bean (Vicia Faba L.) grown under field conditions in the jordan valley,jordan: Bestimmung der aktuellen evapotranspiration und pflanzenbestandskoeffizienten von bohnen (Vicia Faba L.) unter feldbedingungen im jordantal,jordanien

This study was conducted to determine actual evapotranspiration and crop coefficients at different growth stages of broad bean (Vicia faba L.) grown in an open field in the Jordan Valley, Jordan using a precise and accurate approach. The study involved 30-min fluxes measurements of energy budget components over broad bean crop using a complete setup of an Eddy Correlation (EC) system. The measurements were conducted during the three main crop growth stages namely initial, development, and midseason growth stages following the Food and Agriculture Organization of the United Nations (FAO) crop coefficient model for green harvested broad bean crop. The average crop coefficients during the initial (K_{C ini}), development (K_{C dev}) and midseason (K_{C mid}) growth stages were 0.37, 0.8 and 1.05, respectively. The measured weighted average crop coefficient over the entire growing season K_{C GS} was 9.5% lower than the FAO corresponding value.

Results showed that there was a clear decrease of (bulk) surface resistance (r_s) as crop canopy developed. Daily average r_s values were 855, 337, and 166?s/m for initial, development, and midseason growth stages, respectively. Moreover, r_s was found to be highly correlated to crop height (h_c). A simple linear relation between r_s and h_c with R² of 0.91 was found. This relation will enable future direct determination of crop evapotranspiration (ET_C) using Penman-Monteith equation without the need to calculate both grass reference evapotranspiration (ET_O) and crop coefficient (K_C) values.     

Polyacrylamide (PAM) effect on irrigation induced soil erosion and infiltration

Surface irrigation is the oldest and the most widely used method of irrigation. One disadvantage of surface irrigation is soil erosion. New technology employing water-soluble polymers may provide a technique that is effective and affordable to control soil erosion. Water-soluble anionic organic compound known as polyacrylamide polymer (PAM) is the most successful polymer in controlling soil erosion. This study investigated the effect of spraying PAM on the soil surface to control soil erosion and to increase soil infiltration on a Jordanian clay loam soil. Different PAM concentrations, namely 5, 10, and 20 mg/l in addition to the control (0 mg/l) were used in this study. The highest effect of PAM on the measured properties was attained at 20 mg/l. We noticed that PAM's efficiency was decreased with subsequent irrigations. The reduction in soil erosion was 72 and 47.6%, the reduction in runoff water turbidity was 83 and 35%, the increase in water advance time was 6 and 0.9% and the increase in soil infiltration was 36 and 20.8% for the first and fourth irrigation, respectively. PAM's efficiency in flocculating soil particles was studied in the lab where we noticed that its efficiency in sedimentation was increased as its concentration increased.     

Impact of different water price levels on irrigated agriculture in Northern Jordan Valley

A linear programming model was developed to assess the impact of different water prices on cultivated areas, irrigation water demand, net income and optimal cropping pattern in the Northern Jordan Valley (NJV). The results reveal that the price for irrigation water does not reflect any elasticity in the range of water prices between 0.01 and 0.06 JD/M³ indicating constant real economic water price of 0.06 JD/M³. The change in cultivated areas as well as water demand (reduction) starts at water price 0.07 JD/M³. The expected reductions under optimal cropping patterns are 5%, 24%, and 60% for cultivated area and 4.7%, 18.9%, and 31% for water demand with water prices at 0.07, 0.1, and 0.16 JD/M³, respectively. Significant reductions in net incomes are resulted with increasing water prices over current average water price of 0.025 JD/M³. The expected reductions in net incomes are 33.6%, 53.8%, and 81.4% at water prices 0.07, 0.1, and 0.16 JD/M³, respectively. This result reflects the low land profitability as a result of low land productivity and/or low farm gate sale prices for most crops grown in NJV. The study also shows the inconsistency in quantity of water supplied and water demanded, leading to unbalanced water budget on monthly level and inconsequence, a noticeable waste in the quantity of available water during winter months, although there is a net surplus of water over the year. While the findings of this research reveal that a water price in the range of 0.07?C0.1 JD/M³ does not significantly influence the farmers' socio-economic parameters in the NJV, it may help reach the stated goal of saving water especially when monthly distributions of irrigation water are based on real crops water demands and actual cropping patterns.     

Adjusting the irrigation water demand projection module to be viable in central Jordan Valley

In 2004, the Jordan National Water Master Plan (NWMP) was developed, which includes a number of water demand projection modules for assessing the existing water resources, and predicting demands on water for all uses; municipal, industrial, tourist and irrigation. The Irrigation Demand Module was tested with historical data and comparisons were made between the predicted demands as obtained by the module, and the recorded water use provided by relevant institutions. Serious imbalances appeared, totaling the irrigation water demands of more than 1.5 times the recorded irrigation water use. The purpose of this study was to verify the viability of the functional part of the Irrigation Demand Module, namely the Net Irrigation Requirements Calculator (NIR-Calculator) in terms of functions, factors, and data used for the calculations. Results show that the original NIR-Calculator overestimated the values of NIR in the initial growth stage, Kc_i, by almost 55 %, because Cuenca Formula is used in the original version to calculate the initial crop coefficient, while FAO-56 Formula is used in the modified version. When taking the Jordan climatic characteristic into consideration, the original NIR-Calculator underestimated the values of the mid growth stage crop coefficient, Kc_m, by 1.7?C3.5 %, as well as the values of the end growth stage crop coefficient, Kc_e, by 2.2?C8.0 %. The original NIR-Calculator overestimated the effective rainfall by 66.5, 44.8 and 34 % for dry, medium and wet scenarios, respectively. The NIR values obtained by the original NIR-Calculator differed than the modified NIR-Calculator by 5.2, 6.2 and 8.6 % for dry, medium and wet scenarios respectively. Finally, the irrigation demand volume for Deir Ala area obtained by the original NIR-Calculator differed than the modified NIR-Calculator by 2.0, 3.5 and 9.3 % for dry, medium and wet scenarios respectively. In conclusion, although there is a difference between these two versions of the NIR-Calculator, this difference is not enough to cause the 1.5 imbalance in the Irrigation Demand Module. This imbalance can??t be attributed only to the NIR-Calculator and further investigation is required to determine why the imbalance exists.     

Modeling a Rotation Supply System in a Pilot Pressurized Irrigation Network in the Jordan Valley, Jordan

Many farmers in the Jordan Valley have switchedfrom traditional surface irrigationto pressurized irrigation systems. Inorder for these pressurized irrigationmethods to be effective, farmers must have adequate flow andpressure at each FarmTurnout Assembly (FTA). No on-demandirrigation concept has yet been implemented inthe Jordan Valley, and the rotation concept is still in use today. The JordanValley Authority (JVA) is the agency responsiblefor the distribution of water to farmers in the Valley. JVA engineers wereused to implement the irrigation rotationschedule, without any attention being paid to itseffect on the pressure in the network. Using MS Excel, a computer spreadsheet model was createdto examine the effect of selected rotation on thepressure in the network. This model was called theTurnout Pressure Simulation Program (TPSP).The TPSP model was used to map and identifyfarms that will incur pressure problems with any of the selected rotation schedules. This modelwas tested in the northern part of a pilotpressurized irrigation network known as TO2,and included 131 irrigated farm units (400 ha)located in Adassiyeh at the northern end of the Jordan Valley. The TPSP model was also usedto study illegal openings and the effect of these on the pressure in the network. The effect of four, eight, and 12 illegal openings was studied for a selectedrotation schedule, and an average reduction in pressure of 12%, 30%, and 44% was noted compared to when there were no illegal openings.