Fig. 1

Example spectra from cropping systems from various locations. The rice and tea spectra are from Liu et al. [30], the corn soil, no till, fertilized with poultry litter, is from Georgia, USA [31], and the corn/soybean sample is from Quebec, Canada [32]. DNA deoxyribonucleic acid; Oth Di1, Oth Di 2 orthophosphate diesters other than DNA. Spectra were analyzed without proton decoupling and processed with 7 Hz line-broadening. The full spectra are scaled to the height of the orthophosphate peak; the insets were enlarged by different factors, to best show the indicated regions