Modeling temporal distribution of water, ammonium-N and nitrate-N in root zone of wheat using HYDRUS 2D under conservation agriculture
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Date
2018
Authors
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Journal ISSN
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DIVISION OF AGRICULTURAL PHYSICS ICAR-INDIAN AGRICULTURAL RESEARCH INSTITUTE NEW DELHI -
Abstract
The studies on effect of conservation agricultural practices in improving the soil
water and soil nitrogen distribution in root zone during crop growth need special
attention as these are crucial components of irrigation and fertilizer management
programmes. In current study, temporal distribution of both soil water and soil NO3-N
under different conservation agriculture (CA) practices were analyzed using the
Hydrus-2D model during the wheat growth. The treatments were: conventional tillage
(CT), zero tillage (ZT), permanent broad beds (PBB), ZT with residue (ZT+R), and
PBB with residue (PBB+R). Results on soil physical environment changes after 8 years
of continuous adoption of these practices showed that permanent broad bed with and
without residue retention and zero tillage with residue retention reduced subsurface
bulk density (BD), increased field saturated hydraulic conductivity (Kfs) and improved
soil water retention significantly over CT.
Measured value of Kfs and Į and n parameter obtained as output of Rosetta
Lite model were optimized through inverse modeling and were used as hydraulic
inputs of the model which predicted daily change in SWC of profile with reasonable
accuracy (R2
= 0.75; RMSE= 0.038). Soil water balance simulated during 62-91 DAS
from the model showed 50% higher cumulative transpiration and 50% lower
cumulative drainage and higher soil water retention in PBB+R as compared to CT.
Reported values of first-order rate constants representing nitrification of urea
to NH4(ȝa )(dѸ1
)and representing nitrification of NH4-N to NO3-N (ȝn) (dѸ1
) and the
distribution coefficient of urea (Kd - in cm3 mgí1
) were optimized through inverse
modeling and were used as solute transport and reaction input parameters of the
model which predicted daily change in NO3-N of profile with reasonable accuracy
(R2
= 0.83; RMSE= 4.62). Since NH4-N disappeared fast, hence it could not be
measured frequently and therefore not enough data set could be generated for their use
in calibration and validation of model.
Description
t-9974
Keywords
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