Modeling sugar content of farmer-managed sugar beets (Beta vulgaris L.).

We measured or estimated leaf and root physical and chemical traits of spatio-temporally heterogeneousfield-grown sugar beet throughout its ontogeny during three growing seasons. The objective was toquantify the impact of temporal changes in these traits on root sugar content [S(R); g 100 g-1 root dryweight]. Artificial Neural Network (ANN), in conjunction with thermal time (oCd), adequately delineatedthe boundaries (mean ± standard deviation, S.D.) between S(R) during early (41.6 ± 6.2), med (54.5 ± 3.0),and late ontogeny (63.4 ± 2.4), corresponding, respectively to low, medium, and high S(R). Calibrationand validation Partial Least Squares (PLS) regression models, using plant physical and chemical traits,predicted and validated sugar content of sugar beet leaves [S(L)] and roots [S(R)] throughout its ontogenywith significant probabilities. Most physical and all chemical traits exhibited dynamic changesthroughout plant ontogeny and, consequently, negatively or positively impacted S(R). The positiveimpact of S(L) and root volume (RV) on S(R) diminished towards the end of the growing season;whereas, the positive impact of root density (RD) and carbon:nitrogen (C:N) ratio in leaves [C:N(L)] androots [C:N(R)] persisted throughout plant ontogeny. Specific leaf area (SLA), in particular, exhibitednegative, then positive impact on S(R). The utility of physical and chemical traits of field-grown sugarbeets in building reliable PLS models was confirmed using multivariate analysis on secondary statistics(residual mean square errors, RMSE and validation coefficients of determination, Q2) whichdiscriminated between and correctly classified low (100%), medium (95%) and high (97%) S(R) groups.The findings may have implications to design management practices that can enhance C:N ratio and Csequestrationin roots, maintain optimum, but not excessive, N level in developing leaves and roots,optimize root sugar content and minimize its variation under field conditions