Techniques to diagnose plow and disk pans

Chen, Y. and Tessier, S. 1997. Techniques to diagnose plow and disk pans. Can. Agric. Eng. 39: 143-147. The phenomena of plow or disk pan formation have recently been given considerable attention, as it is associated with important agronomic consequences. However, most reports only describe such phenomena on a qualitative basis. This note describes and validates the use of a new procedure to objectively diagnose the occurrence of mechanically induced hard pans. Data from experiments carried out at three locations, featuring tillage management systems based on mouldboard plow and heavy disk harrows, were reviewed to illustrate the use of this procedure. A plow pan was assumed responsible for differences in soil bulk density (Ph) or cone index (CI) at two reference depths, one above and the other below the bottom of the tilled layer. The occurrence of a plow pan was diagnosed based on statistical confidence interval comparisons of Ph or CI values between these two depths. However, CI profiles seem less reliable to diagnose plow pans. Based on the same principle, a disk pan could be diagnosed on the account of differences in micro-cone index (MCI) at two reference depths. Vne grande emphase a ete placee aI'identification du phenomene qu'est la formation de couches indurees comme les semelles de labour ou de disques. Cependant, la plupart des etudes rapportant ce phenomene ne concluent souvent que sur des bases qualitatives quant a la presence ou non de couches indurees. Vne nouvelle methode d'etude a ete elaborce pour diagnostiquer objectivement I'apparition d'une couche induree. Des essais ont ete effectucs a trois sites en comparant des systemes de travail du sol comportant la charrue a versoirs et la herse a disque. Vne semelle de labour semble responsable de differences de masse volumique apparente (Ph) et de resistance a I'enfoncement (CI) entre deux profondeurs de difference, I'une au dessus et I'autre sous I'interface entre la zone influencee et non-influencee par Ie travail du sol. La presence d 'une semelle de labour a ete verifiee par des comparaisons statistiques (intervalle de confidence) des valeurs de Ph ou CI entre ces deux profondeurs. Cependant, les mesures de CI semblent mains conc1uantes pour Ie diagnostic de semelles de labour. Avee Ie mcme principe, on peut conclure sur I'apparition d'une semelle lissage sous les disques de herses lourdes avec des mesures de la resistance a I'enfoncement (MCI) avec un micro-penetrometre.