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Abstract
SUMMARY
In the Egyptian agricultural sector, water is the major constraint to expand the total agricultural area which could contribute to tighten the country’s food gap. Therefore, there is an urgent need to use dwindling water resources efficiently and raising the efficiency of water use and maximize yield produced per unit of water under deficit irrigation conditions.
This study was conducted to quantify the response of drip-irrigated maize crop grown in calcareous soil under arid conditions to deficit irrigation and the effect of potassium and nitrogen rates in alleviating water stress on the:
1- Amount of applied irrigation water (AIW).
2- Amount of water consumptive use (CU).
3- Water use efficiency (WUE).
4- Irrigation water use efficiency (IWUE).
5- Yield response factor (Ky).
6- Effect of irrigation regimes and K and N doses on yield and yield components of maize crop.
Field experiments were conducted at the experimental farm of Nubaria Horticulture Research Station, Agriculture Research Center during the summer seasons of 2005 and 2006. A split split-plot experimental design with four replicates was used. Three irrigation treatments (I1 = 100% of ETc, I2 = 75% of ETc and I3 = 50% of ETc) represented the main plots, three potassium rates (K0 = Zero, K24 = 24 and K48 = 48 kg K2O/fed) represented the sub-plots and two nitrogen rates (N90 = 90 and N120 = 120 kg N/fed) represented the sub sub-plots.
Field and Laboratory Measurements:
Soil physical characteristics:
- Particle size distribution and soil texture class.
- Soil moisture characteristic curve.
- Soil bulk density.
- Saturated hydraulic conductivity.
- Infiltration rate and cumulative infiltration.
Soil chemical characteristics:
- Electrical conductivity (EC).
- pH.
- Cations and anions concentrations.
- Organic matter (OM).
- Cation exchange capacity (CEC).
- Calcium carbonate contents.
Crop Water-Use Parameters:
- Epan : Daily measured pan evaporation.
- θ : Gravimetric soil samples.
- ETo : Reference evapotranspiration.
- AIW : Applied irrigation water.
Collected Data for Crop and Yield Parameters:
- Leaf area (cm2)
- Plant height (cm)
- Ear height (cm)
- Number of rows per ear
- Number of kernels per row
- Number of kernels per ear
- One hundred-kernels weight (gm)
- Number of ears per plant
- Ear weight (g)
- Grain yield (kg/fed)
The Main Results Can be Summarized as Follows:
1- Soil physical characteristics:
- The textural class of the soil is sandy loam,
- The average bulk density 1.28 Mg m-3,
- The average saturated hydraulic conductivity was 5.3X10-6m s-1,
- The available water of 60 cm soil depth was 136 mm,
2- Soil chemical characteristics:
- The average pH 8.4,
- Average EC 2.7 dS m-1,
- The average CEC 39.9 cmol kg-1,
- High in CaCO3 contents (average 25.7%),
- Highly calcareous,
- low in OM contents (average 0.22 %),
- The most soluble ions were Na+ and Cl- and the lowest soluble ions were K+
3- Maize water use parameters:
- The average of daily ETo was 4.98 and 5.26 mm d-1 in 1st and 2nd growing seasons, respectively.
- Seasonal ETo values were 508.3 and 531.3 mm in 1st and 2nd growing seasons, respectively.
- The average of ETc (mm d-1) in initial, development, mid-season and late season stage was 1.4, 4.0, 6.2 and 3.4, and 1.9, 4.2, 5.4 and 3.4 mm d-1 in 1st and 2nd growing seasons, respectively.
- the amounts of AIW increased with the advance in growth stages to reach the peak at mid-season stage and then decreased towards the last stage at late season stage.
- The total AIW for I3, and I2 were 53.5, and 76.7 % in 1st season and 54.8, and 77.5 % in 2nd season, respectively of I1.
- As plants developed, gradual increase in water consumption was observed, at mid-season stage the CU reached its peak after this period the rates of CU decreased.
- The average cumulative CU value at development, mid-season and late season stage for I1, I2 and I3 were 394.2, 320.2, and 230.3, and 364.7, 293.3, and 212.7 mm in 1st and 2nd growing seasons.
- The seasonal CU or actual evapotranspiration (ETa) values were influenced by the moisture regimes.
- A positive linear relationship between AIW (mm) and CU (mm) over the two growing season was obtained (CU = - 0.77 + 0.79 AIW, R2 = 0.96).
The highest CU found under K48 treatmen