Soil properties under different orchard floor management systems for organic apple production

Summary

Orchard floor management impacts soil conditions and thus tree performance. This research was initiated to investigate the effects of alternative orchard floor management systems compatible with organic production on soil parameters using the“Pacific Gala” apple cultivar (Malus × domestica Borkh.) on three rootstocks of varying vigor. Alfalfa hay mulch, propane flame burner, and Swiss sandwich system(combination of resident vegetation and tilled strips)were compared from 2001 to 2005. These treatments were applied to tree rows which provided different vegetation-free areas. Contrasting additions of organic matter were evaluated for their effect on soil organic matter (SOM), C content, nitrate and ammonium availability, moisture, and soil food web through nematode
populations. Laboratory incubations to determine C and N mineralization potentials were performed. During this time period, SOM increased under the mulched soil and slightly less under the Swiss sandwich system (SSS) but in this last case without external inputs. Carbon and N pools were not impacted by flame burning (FL) but were enhanced by alfalfa hay mulch (MU) and to a lesser extent by SSS. Nitrate-N content in soil under MU increased between five and ten times compared to SSS and FL. Total number of nematodes was
higher for SSS and MU compared with FL treatment; however, SSS had the most structured soil food web, an important sustainability trait, while MU had the least