Abstract:
The APSIM (Agriculture Productions Systems
SImulator)–Maize & Groundnut model has been utilized on a
global scale to assess the effects of various farming practices on
the growth of maize and groundnut intercropping. However,
limited attention has been given to modeling the crop productivity
(t/ha) and water productivity (t/ha/m3
) of maize and groundnut
intercropping under conditions such as rainfed or rainfed with
supplementary irrigation, in tropical SouthAsia. To address this
gap, we tailored and assessed the APSIM–Maize & Groundnut
intercropping model for two widely cultivated Sri Lankan
varieties: Pacific (Maize) and Lanka Jumbo (Groundnut). The
APSIM model was introduced to simulate the growth,
development, and yields of maize-groundnut intercropping in the
Dry Zone of Sri Lanka, utilizing field experimental data. The
model calibration process involved utilizing the first set of data to
determine varietal parameters. The simulation results
demonstrated a high level of agreement between the simulated
values and the actual measurements during the growing periods
as RMSE and RRMSE values for maize yield were 0.89 t/ha and
11.37% while that for groundnut was 0.108 t/ha and 7.7%. RMSE
(Root Mean Square Error) quantifies the average prediction error
in the same units as the target variable. RRMSE (Relative RMSE)
normalizes RMSE by the range of observed values, providing a
percentage-based measure for better comparison across datasets
with different scales. The model accurately predicted grain yield
for maize and groundnut under moisture-limited field conditions,
showcasing a strong fit with the observed data. This fit was
consistent across various factors, including cultivation year,
season, time of planting (i.e., with rainfall or based on specific
planting dates), variety, and water management practice (e.g.,
completely rainfed or rainfed with supplementary irrigation).
Traditionally, many maize farmers grow this crop as a standalone
crop. However, introducing groundnut as a secondary crop
alongside maize offers advantages such as additional income and
enhanced soil fertility. It was evident from the results that maizegroundnut intercropping can be used to get a high yield with a
limited amount of water during periods of low rainfall such as the
yala season and it is a very good solution to water scarcity. In
situations where rainfall or other essential factors are delayed,
employing crop modeling with APSIM becomes crucial to
augment reliance on supplemental water resources and meet the
specific requirements for maize and groundnut crops
