Figure 1. Penetration resistance at Foulum for loosened/non-loosened half-plots. Half-plots loosened September 2000. Measurements carried out 6 months (a) and 3½ years after loosening. Vertical broken line indicate critical limit for root growth (1.5 MPa).
The subsoil loosening was carried out without significant visual damage to the young grass-clover crop. However, reduced growth of the grass-clover crop was found in the following growing season. Especially the white clover appeared to be sensitive to soil loosening. Apparently, this unintended effect of the soil loosening had marked effects on the growth of the succeeding winter wheat crop. In winter wheat following grass-clover there was a tendency towards yield reduction in loosened and unmanured soil in 2002 and 2004 (Table 1). In contrast, there was a tendency to increased yield in loosened soil at Flakkebjerg in 2003 (with and without manure) and in 2004 (with manure).