Agriculture Reference
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(8) Write down the governing equations for solute transport under the following
conditions:
(a) Two-dimensional transport through homogeneous media
(b) One-dimensional transport through homogeneous media
(c) One-dimensional transport with nitrification chain
(d) Dual porosity flow in heterogeneous media
(9) Define convection-dispersion equation (CDE) for reactive solute through a
uniform soil.
(10) Define the following: Dispersivity, Retardation factor, First-order rate con-
stant, Zero-order rate constant, Hydrodynamic dispersion, Dispersivity length.
(11) What is a breakthrough curve? Draw a typical breakthrough curve.
(12) Explain the procedure for estimating solute load from agricultural fields.
(13) Write down the guiding principles for minimizing nitrate leaching from
agricultural fields.
(14) Describe the procedures/measures for minimizing nitrate leaching from agri-
cultural fields.
(15) Name some models for solute transport study along with their salient features.
(16) In a lysimeter (8m
4m), wheat crop was grown. The leaching amount was
collected, and the concentration of NO
3
-N of the respective leachate for the
growing season and the fallow period are given below. Find out the total
amount of NO
3
-N leached down during the period.
×
DAE
20
40
60
80
100
120
140
160
180
200
Drainage (l)
1.0
2.9
3.8
1.6
1.0
2.5
3.5
1.5
4.0
5.0
Conc. of NO
3
-N
in drainage
water (mg/l)
3.0
4.5
3.5
2.8
2.9
3.0
4.0
4.5
5.5
3.0
DAE
=
days after seedling emergence.
(17) In an experimental field of rice crop, nitrogenous fertilizer was applied in
two splits. Water sampler was installed at 150 cm depth to collect the deep
drainage. Water samples were collected at 15-day interval and the collected
samples were analyzed at laboratory for NO
3
-N concentration. Deep drainage
was estimated using field water balance approach. The sampling was done
during the crop season and continued for a month after the crop harvest.
The following data were gathered:
DAT
15
30
45
60
75
90
105
120
135
150
Estimated drainage (mm)
25
35
30
28
32
27
19
21
25
29
Conc. of NO
3
-N in water (mg/l)
3.5
3.5
3.2
2.0
4.0
3.3
2.9
4.1
4.0
3.5
Determine the amount of NO
3
-N leached per hectare during the period
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