Abstract:
To know available water holding capacity of soil, knowledge of
soil water retention limits is essential. This is useful in irrigation
scheduling, water balance simulation and land use planning. The
measured soil water limits: upper limit at field capacity (-33 kPa
pressure) and lower limit at permanent wilting point (-1500 kPa
pressure) was available for 67 established soil series of
Chattisgarh state. In the present paper, a simple generic power
equation has been developed to estimate the soil water limits
based on soil survey data such as texture and bulk density.
Linear regression was used to estimate the gravimetric soil water
limits from sand and clay percentages. The volumetric soil water
limits is estimated by multiplying gravimetric soil water limits
with bulk density. The predictions were adjusted for coarse
fragments and organic carbon present in the soil matrix.The standard error (SE) of the measured water content at field
capacity (Wfc) and at permanent wilting point (Wpwp) are 0.98
and 0.54 respectively whereas the SE of the estimated water
contents by the developed models are less, 0.89 and 0.51. The
percentage error between the estimated and measured Wfc and
Wpwp found to be 10.1 and 5.8 respectively Comparison made
through graphical representation of error bars also shows
satisfactory result at (i) ±1.96 (SE) and (ii) ±10% error criteria.
Coefficient of variation (CV) also indicates improvements. The
goodness of fit (R2) value between the estimated Wfc with
measured Wfc, is 0.85, which shows model estimation is
reasonable. Similarly, for values of Wpwp by model estimation R2
is 0.81. Paired „t‟ test for comparison shows that model is
estimating well at 95% confidence level.
