BioCycle October 2005, Vol. 46, No. 10, p. 59
Researchers measure water infiltration, microbial activity and organic matter content – finding that organic methods bring higher macroporosity within the row and wheel-track.
Iris Vogeler, Siva Sivakumaran and Rogerio Cichota

HERE at the HortResearch center in Palmerston North, New Zealand, we have recently begun a compaction study – just getting our first results from transport in the two different orchards. Penetrometer measurements will be taken in springtime (soon) when the roots are taking off. This data will show if roots can penetrate into compacted regions, and how cover crops might reduce compaction. Results can then be used to determine best management practices.
Intensive cultivation of orchards with heavy machinery can cause soil compaction, which changes the soil structure and pore system, with respect to both pore size distribution and the connectivity of the pore network. These changes affect the flow processes of water, nutrients and gas in the soil, and their availability to plants and microorganisms, and thus the quality of a soil for production. Decreased permeabilities of the pore system to air and water also result in decreased soil aeration and infiltration rates, resulting in decreased microbial activity and breakdown of organic matter, and thus the fertility of the soil.
To determine the effect of two different management practices on soil compaction and its consequences, we measured water infiltration, chemical mobility, microbial activity, and organic matter content in a conventionally and organic-managed apple orchard. Measurements included soil compaction using a compaction meter, water infiltration and chemical mobility using the disc permeameter technique, macroporosity, bulk density and microbial activity.
Measurements were taken both within the tree row and the wheel-track, and down to a depth of 35 cm. In both, the row and interrow of the organic orchard, grass was growing. In the conventional orchard, only in the interrow grass was growing, whereas the row was sprayed and thus bare.
The results indicate that organic management results in a higher macroporosity in both the row and the wheel-track compared to conventional management. The close to saturation hydraulic conductivity was also significantly higher within the row of the organic orchard compared to the conventional orchard, and compared to the wheel-track. Compaction in the wheel-track was higher under organic than conventional management.
Iris Vogeler, Siva Sivakumaran and Rogerio Cichota are at the HortResearch in Palmerston North, New Zealand, Authors can be e-mailed at: ivogeler@hortresearch.co.nz.