Genotypic and environmental variation in water soluble carbohydrate content of silage maize

The concentration of water soluble carbohydrates (WSC) is a main determinant of the ensiling potential of forages and the aerobic stability of silages. The aims of the present study were to assess the impact of genotype on the seasonal changes of WSC concentration, to adapt and calibrate the FONSCH (FOrage NonStructural CarboHydrates) model – originally developed for forage grasses – for silage maize, and finally to conduct a long-term simulation study for quantifying weather-related variability of WSC content. A 3-year field experiment (2001–2003) was conducted in northern Germany to evaluate differences in WSC content among commercial silage maize varieties and to provide calibration data for modelling. Eight varieties covering three maturity groups (early, mid-early and mid-late) were investigated. On six dates throughout the vegetation period the plants were harvested, separated into ear and stover, and freeze–dried for subsequent determination of WSC. Ear, stover, and whole crop WSC content was influenced by genotype and environmental conditions. Genotypic effects were most pronounced in the early grain filling period. At silage maturity, an effect of variety on whole crop WSC content was found in the mid-early group only, accounting for a difference of 44.8 g WSC kg⁻¹ DM. FONSCH model calibration showed good agreement between observed and calculated WSC contents, with RMSE below 27.6 g WSC kg⁻¹ DM and r² above 0.84. Parameter estimates revealed a substantial influence of temperature and solar radiation on WSC content, while plant available soil water had minimal impact. Successful model validation with an independent data set allowed us to perform a 30-year simulation study, where variation among varieties and years of up to 68.8 and 186.5 g WSC kg⁻¹ DM, respectively, demonstrated a larger impact of environmental conditions compared to genotype.