Abstract: A new method for tree stem analysis by digital photogrammetry was introduced in this paper. By direct quadrature, the section area of a definite tree ring was measured, and the theoretical diameter was then derived, instead of measuring the so-called average diameter, a traditional method applied for timber volume estimation. Comparing with manual survey, the accuracy of this method was significantly improved, especially when the trunk form is irregular. In our case study, the accuracy for the measurement of ring width was 10% higher than that by single-direction measure. This method could be more accurabe for bark measurement, because the gear-formed section could cause larger errors in biomass or volume estimation with conventional method. Also, digital photogrammetry could be an ideal way to archive information on disks and to use it whenever necessary.

Key words: Deep fertilization in autumn, Straw return to field, Efficiency of water and fertilizer, Dryland corn