CSM-IXIM or simply IXIM (pronounced e-sheem), the Maya word for maize, is a more mechanistic maize model available in DSSAT since v4.5.  The model IXIM (Lizaso et al., 2011) was developed by accumulating and testing together a number of CERES-Maize model (Jones and Kiniry, 1986) improvements. The modular version of CERES-Maize, (CSM; Jones et al., 2003) was used for that purpose.

IXIM simulates expansion and senescence of individual leaves using a thermal time framework (Lizaso et al., 2003a) and for each leaf, estimates instantaneous C assimilation as limited by temperature, leaf age and leaf position (Lizaso et al., 2005). Canopy respiration is next estimated, based on organ composition, and the resulting potential crop growth rate calculated. Compared to CERES-Maize, IXIM also includes differences in the simulation of assimilate partitioning, ear growth, kernel number, grain yield, and plant N acquisition and partitioning (Lizaso et al., 2011). The model includes new algorithms to estimate PAR from solar radiation (Lizaso et al., 2003b), and light absorption by individual leaves through the canopy (Lizaso et al., 2005).

More recently, the simulation of additional processes have been improved and/or added. This includes crop N demand and partitioning, as well as N remobilization and allocation into the grain (Yakoub et al., 2017). Concerns derived from climate change projections and elevated temperatures have been addressed. Lizaso et al. (2017) incorporated new thermal time calculation, and the simulation of the anthesis-silking interval. Also based on previous work (Lizaso et al., 2003c; Lizaso et al., 2007), the explicit and distinct impact of heat on pollen and silks was described together with the overall impact on grain yield (Lizaso et al., 2017).

 References

Jones, C.A., and J.R. Kiniry (Eds.). 1986. CERES-Maize: A simulation model of maize growth and development. Texas A&M Univ. Press, College Station.

Jones, J.W., G. Hoogenboom, C.H. Porter, K.J. Boote, W.D. Batchelor, L.A. Hunt, P.W. Wilkens, U. Singh, A.J. Gijsman, and J.T. Ritchie. 2003. The DSSAT cropping system model. Eur. J. Agron. 18:235–265.

Lizaso, J.I., W.D. Batchelor and M.E. Westgate. 2003a. A leaf area model to simulate cultivar-specific expansion and senescence of maize leaves. Field Crops Research 80(1):1-17.

Lizaso, J.I., W.D. Batchelor, M.E. Westgate and L. Echarte. 2003b. Enhancing the ability of CERES-Maize to compute light capture. Agricultural Systems 76(1):293-311.

Lizaso, J.I., M.E. Westgate, W.D. Batchelor and A. Fonseca. 2003c. Predicting potential kernel set in maize from simple flowering characteristics. Crop Science 43(3):892-903.

Lizaso, J.I., W.D. Batchelor, K.J. Boote, and M.E. Westgate. 2005. Development of a leaf level canopy assimilation model in CERES-Maize. Agronomy Journal 97:722-733.

Lizaso, J.I., A.E. Fonseca and M.E. Westgate. 2007. Source-limited and sink-limited kernel set: Two complementary approaches to simulate kernel number with CERES-Maize. Crop Science 47(5):2078-2088.

Lizaso, J.I., K.J. Boote, J.W. Jones, C.H. Porter, L. Echarte, M.E. Westgate, G. Sonohat. 2011. CSM-IXIM: A New Maize Simulation Model for DSSAT version 4.5. Agronomy Journal 103:766-779.

Yakoub, A., A.J. Lloveras, A. Biau, J.L. Lindquist, J.I. Lizaso. 2017. Testing and improving the maize models in DSSAT: Development, growth, yield, and N uptake. 2017. Field Crops Research 212:95-106.