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Applied Ocean Research
MDPI
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Abstract: |
Shallow groundwater contamination by nitrate is frequent in agricultural lands in Egypt
because of the use of urea fertilizers. The urea transformation process in the vadose zone was
simulated using a HYDRUS-2D model, Software package for simulations of 2D movement of water,
heat, and multiple solutes in variably saturated media, for subsurface drip irrigation. The root
water and nutrient uptake were assessed for three soil types (sandy loam, loam, and silty loam)
with three emitter discharge levels (1.0 L h1, 1.50 L h1, and 2.0 L h1), for a comparison of three
fertigation strategies (A) at the beginning, (B) at the end, and (C) at the middle of the irrigation cycle.
The extension of the wetted area mainly depends on soil hydraulic conductivity. The high emitter
discharge with a short irrigation time is suitable for shallow-rooted crops. The cumulative flux was
highest for silty loam soil and the lowest was for the sandy loam soil (1891, and 1824 cm3) for the
2 L h1 emitter discharge within the 35 days simulation. The cumulative drainage significantly diers
among soil types with little eect of emitter discharge. It recorded 1213, 295, 11.9 cm3 for sandy loam,
loam, silty loam, respectively. Urea transformation is controlled by hydrolysis and nitrification as
well as the adsorption coecient of ammonium. Nitrate distribution is mainly governed by soil type
rather than the emitter discharge where the sandy loam soil is more highly susceptible to nitrate
leaching than to silty loam. Nitrate concentration has recorded the minimum possible level when
applying the urea fertilizer at the beginning of the irrigation event for sandy loam and loam soil
while for the silty loam soil, urea application at the middle of the irrigation event is more eective.
Urea application at the end of the irrigation event gives the highest accumulated leached nitrate
concentration below the root zone and should be avoided (the worst strategy).
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