Field experiment was conducted for one growing season (2012) in clay loam soil at the Experimental Farm of Faculty of Agriculture, Southern Illinois University at Carbondale (SIUC), USA on soybean crop to study the effect of: 1) the closed drip irrigation system: closed circuits with one and two a manifolds for lateral lines (CM1DIS; CM2DIS) and traditional drip irrigation system (TDIS) as a control; and 2) lateral lines length (LLL): LLL1, LLL2 and LLL3 (40, 60,80 m) on soybean growth, yield, oil, protein content and water use efficiency. Plants were drip irrigated every 4 days. N, K2O and P2O5 fertilizers were added via irrigation water. Data obtained could be outlined as follows: 1) According to the mean values of soybean crop growth (leaf area; plant height), yield (grain and straw), both oil and protein content and water use efficiency, the treatment used could be ranked in the following ascending orders: TDIS < CM1DIS < CM2DIS and LLL3 < LLL2 < LLL1; 2) Differences in the means of the studied data among treatments used were significant at the 1% level; 3) The effects of the DIC × LLL on the data obtained were significant at the 1 % level; And 4) the highest values of the obtained data and the lowest ones were achieved in the following interactions: CM2DIS × LLL1; TDIS × LLL3, respectively.
Soybean is one of the most important world crops. It is grown for oil and protein [
Closed drip irrigation circuits have used in attempts to overcome the drop in pressure at the end of the lateral line of drip irrigation system. [8-13] carried out laboratory and field experiments to study the effects of: Closed drip irrigation circuit with one manifold for lateral lines (CM1DIS), with two manifolds for lateral lines (CM2- DIS); traditional drip irrigation system as a control (TDIS) and lateral lines and length (LLL) of 40, 60, 80 m (LLL1, LLL2, LLL3) and their interactions on some hydraulic characteristics of the irrigation system, corn yield, water, fertilizer use efficiency per unit of irrigation water and fertilizer used. Their data could be summarized in the following: 1) Relative to TDIS, both CM2DIS and CM1DIS improved the studied hydraulic characteristics (pressure head, friction loss, flow velocity, lateral discharge, uniformity coefficient; coefficient of variation), corn yield and use efficiency of both water and fertilizer; 2) The mean effects of both DIC and LLL treatments on the studied parameters were significant at the 1%; 3) The effect of DIC × LLL on the parameters under investigation were significant at the 1% level; and 4) concerning the improving effect on the investigated parameters, the treatments could be stated in the following increasing orders: TDIS < CM1DIS < CM2DIS and LLL3 < LLL2 < LLL1.
The field experiments design was split in randomized complete block design with three replicates. Laboratory tests carried out using three irrigation lateral lines L1, L2; L3 (40, 60, 80 m) and the following three drip irrigation circuits (DIC): 1) One manifold for lateral lines or closed circuits with one manifold of drip irrigation system (CM1DIS); 2) Closed circuits with two manifolds for lateral lines (CM2DIS); and 3) traditional drip irrigation system (TDIS) as a control.
Tables 1-3 indicated there some (physical and chemical) characteristics of there the location and irrigation water, respectively.
Irrigation networks include the following components are: 1) Control head: It was located at the water source supply. It consists of centrifugal pump 3"/3", driven by electric engine (pump discharge of 80 m3/h and 40 m lift), sand media filter 48" (two tanks), screen filter 2" (120 mesh), back flow prevention device, pressure regulator, pressure gauges, flow-meter, control valves and chemical Injection; 2) Main line: PVC pipes of 75mm in (ID) Ø to convey the water from the source to the main control points in the field; 3) Sub-main lines: PVC pipes of 75 mm in (ID) Ø were connected to with the main line through a control unit consists of a 2" ball valve and pressure gauges; 4) Manifold lines: PVC pipes of 50 mm in (ID) Ø were connected to the sub main line through control valves 1.5"; 5) Lateral lines: PE tubes of 16 mm in (ID) Ø were connected to the manifolds through beginnings stalled on manifolds lines; 6) Emitters: These emitters (GR) built in PE tubes 16 mm in (ID) Ø, emitter discharge of 4 lh-1 at 1 atm, Operating pressure and 30 cm spacing in-between. The components of closed circuits of the drip system include, supply lines, control valves, supply and return manifolds, drip lateral lines, emitters, check valves and air relief valves/vacuum breakers.
Intervals of irrigation (I) in day were calculated using the following equations:
where: d = net water depth applied per each irrigation (mm), and ETc = crop evapotranspiration (mm/day).
*Particle size distribution after [
*Chemical properties after [
where: AMD = allowable soil moisture depletion (%), ASW = available soil water, (mm water/m depth), Rd = effective root zone depth (m), or irrigation depth (m), and p = percentage of soil area wetted (%).
where: B.D. = soil bulk density (gm∙cm−3).
Irrigation Intervals used was 4 days under both closed circuits and traditional drip irrigation systems.
The (ETc) was computed using the Class Pan evaporation method for estimating (ETo) on daily basis was taken from nearest meteorological station as showing in
The modified pan evaporation equation to be used:
ETo = KpEp (4)
where: ETo = reference evapotranspiration [mm∙day−1], Kp = pan coefficient of 0.76 for Class A pan placed in short green cropped and medium wind area. Ep = daily pan evaporation (mm∙day−1), seasonal average is [7.5 mm∙day−1] [
The reference evapotranspiration (ETo) is then multiplied by a crop coefficient Kc at particular growth stage to determine crop consumptive use at that particular stage of maize growth.
Etc = EToKc (5)
The reduction factor (Kr) was calculated using Eq.6.
where: GC = ground cover percentage.
Irrigation efficiency (Ea) was calculated by Ea = Ks∙Eu (7)
where: Ea = irrigation efficiency (%), Eu = emission uniformity (%) and Ks = reduction factor of soil wetted.
The gross irrigation water requirements IWRg (mm depth) were calculated according to:
IWRg = IWRn∙Ea + Lr (8)
where: IWRg = the gross irrigation water requirements, IWRn = the net irrigation water requirements and Lr = the extra amount of water needed for leaching.
Soybean seeds were (Glycine max-L, Rils-75) Varity was cultivated on April 15th. The distance between rows was 0.7 m and 0.15 m between plants in the row. Plants densities were 55,500 plants per fed according to (ISU). Each row was irrigated by a single straight lateral line in the closed circuits and traditional drip irrigation plots.
Plant measurements and observations were started 21 days after planting, and were terminated on the harvest date. Yield and components including leaf area (cm2) by Plano meter, plant height (cm) by meter measuring, total grain and straw (Kg/fed) by balance; oil and protein (g/kg). Oil and protein determined in Grain Quality Laboratory using near-infrared analysis. All plant samples were dried at 65˚C until constant weight. Grain yield was determined by hand harvesting the 8 m sections of three adjacent center rows in each plot and was adjusted to 15.5% water content. In all treatments plots, the grain yields of individual rows were determined in order to evaluate the yield uniformity among the rows.
MSTATC program (Michigan State University) was used to carry out statistical analysis. Treatments mean were compared using the technique of analysis of variance (ANOVA) and the least significant difference (L.S.D.) between systems at 1% [
Data in
DIC: Irrigation circuit design; L.L.L.: Lateral line length; CM2DIS: Closed circuits with tow manifolds separately; CM1DIS: Closed circuits with one manifold; TDIS: Traditional drip irrigation system.
tively.
Data on hand could be stated in the following:
1) According to the mean values of soybean crop growth (leaf area; plant height), yield (grain and straw), both oil and protein content and water use efficiency, the treatment used could be ranked in the following ascending orders: TDIS < CM1DIS < CM2DIS and LLL3 < LLL2 < LLL1;
2) Differences in the means of the studied data among treatments used were significant at the 1% level;
3) The effects of the DIC × LLL on the data obtained were significant at the 1% level;
4) The highest values of the obtained data and the lowest ones were achieved in the following interactions: CM2DIS × LLL1; TDIS × LLL3, respectively.