Modeling soil water dynamics, root water uptake and water use in soybean-wheat system under different time lags after chiselling
Loading...
Date
2015
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
DIVISION OF AGRICULTURAL PHYSICS INDIAN AGRICULTURAL RESEARCH INSTITUTE NEW DELHI
Abstract
In the present investigation, the effects of chiselling on soil water dynamics, root
water uptake and water balance components were evaluated using Hydrus-2D model.
The input parameters were collected from field experiments conducted for 2 years
(2013-14 and 2014-15) with soybean-wheat crops in rotation on a sandy loam soil in
the experimental farm of the ICAR-Indian Agricultural Research Institute, New Delhi.
The time variable changes in soil hydro-mechanical regime and root growth in a
soybean-wheat system through deep tillage (chiseling) of the compact sub-surface
layers. Hydrus-2D model was applied to evaluate the effect of chiseling in soil water
dynamics vis-à-vis crop water uptake. The chisel treatments were RS; Residual
(Chiseling on June, 2011), RC; Repeated (Chiseling on June 2011 and again on June
2013), FC; Fresh (Chiseling once in June 2013) and NC; No chiseling (Control). The
hydro-mechanical properties of soil viz., bulk density (b), penetration resistance
(PR), field-saturated hydraulic conductivity (Kfs), and steady state infiltration rate (i)
were monitored initially and at harvest of the crops. Soil water content at 15 cm depth
interval (up to 120 cm) was recorded periodically.
Effect of chiseling was evident in reducing the sub-surface compaction, although the
benefits were short-lived, and the residual effect was much less at the 2nd year of crop
rotation. A very high rainfall of 1182 mm following chiseling resulted in soil
reconsolidation and the benefits of chiseling could not be realized in the FC plots. In
soybean 2013, 3-5% lower soil bulk density was observed in RS and RC plots as
compared to NC plots particularly in 15-30 cm soil layer. The RC and RS treatments
also showed 35 and 14.7 % lower values of penetration resistance in soybean crop as
compared to NC in 15-30 cm soil layer. The Kfs and i values are higher (25-30 % in
15-30 cm soil layer and 30-36 % respectively) in first year of soybean in NC plots,
however the effect of chiseling reduced thereafter and the residual effect on b, PR,
Kfs and i was marginal at harvest of the wheat crop and thereafter no prominent effect
was seen in both wheat and soybean crop during 2014-15. The profile soil water
content was distinctly higher in RC and RS plots as compared to NC and FC. In 2
nd
year of rotation, differences reduced and became marginal. Larger root length density
was recorded at chiseled 15-30 cm layer in both soybean and wheat crop in the 1st
year, and no such effect was identified thereafter.
Simulation results showed larger daily actual and cumulative root water uptake in RS
and RC compared to the NC treatment and could be attributed to marginally higher
LAI and fIPAR in chiseled plots along with greater depth and spread of roots. Model
simulated soil water content matched with observed data with good agreement
[R2>0.60, p <0.01; RMSE = 0.04-0.08% and nRMSE = 16.2-28.4%] in the 1st year of
rotation. The model was further validated by comparing the simulated and observed
values of crop transpiration with R2=0.88 and 0.83 in soybean wheat crop during
2013-14 (p<0.01). Simulated field water balance components indicated 5-7 cm higher
soil water storage in 0-75 soil profile in RC, which had 3-4 cm higher seasonal
transpiration by the crops.
Chiseled plots (RC and RS) had significantly higher yield and water use in 1st year
soybean-wheat rotation, and yield difference was marginal in 2nd year rotation. In
view of cost of chiseling and the marginal benefits obtained till 2ndyear of crop
rotation, chiseling once in 2-3 years may be recommended for the sandy loam to
sandy clay loam soils under the semi-arid climate of Delhi.
Description
t-9307
Keywords
null