Estimation of amaranthus (a. cruentus) crop evapotranspiration under drip irrigation in Omu-Aran, Kwara state

The crop evapotranspiration and crop coefficient (K
c
) of Amaranthus cruentus cultivated in a drainage lysimeter were calculated. The drainage lysimeter was composed of a plastic bucket with a 0.15m diameter and a circular cross-sectional area of 0.0176 m
²
. For the estimate of reference evapotranspiration (ET
o
) using the FAO-Penman Monteith model, climate variables including solar radiation, relative humidity, air temperature, and wind speed were remotely collected. Crop evapotranspiration (ET
c
) was calculated using the water budget method. Using the numerical determination method, the crop factor (K
c
) was calculated. The obtained K
c
was used to multiply the ET
o
to obtain the ET
c
which is the water requirement for Amaranthus. The crop's ET
c
increased progressively from its emergence period (4mm week-
¹
) during the first week after planting (WAP), decreased at 2 WAP, and increased again to its peak value of 5.18 mm week-
¹
at the 4 WAP. K
c
was 0.6 and 1.02, respectively, for the emergence and maturity stages of Amaranthus cruentus. The coefficient of determination (R
²
) is 0.9235, which showed a good relationship and prediction between the numerical approach and the lysimetric ET
c.
This suggests that the model or method of numerical estimation utilized to predict crop ET
c
is quite precise and offers a trustworthy estimate of the crop ET
c
values. The statistical indicators gave a range of 1.272-0.76 mm d−
¹
for mean absolute error (MAE) and 1.32–0.85 mm d−
¹
for root mean square error (RMSE) which is in line with the values as predicted. The results of this study present helpful information for farmers producing vegetables (amaranthus) for increased agricultural productivity and judicious crop water management.