Ruts and the Orchard Floor

After one of the wettest harvests in living memory there are lots of ruts, holes and packed areas out in orchards, particularly any of the later harvested varieties. Visible rutting seems to be in three main areas – usually moderate soil packing to rutting in the inter row area, moderate to extensive soil disturbance at row entrances or wherever there is turning with a load and finally access roads or lanes, especially the grassed ones are really chewed up. The problem is not so much the weight and axles under any one load. It is the sheer number of trips under wet soil conditions that eventually causes the soil structure to fail (Figure 1).

Figure 1 – Continuous rainfall in October, 2006 created extremely difficult conditions in which to carry out harvest operations.

Common knowledge suggests that once you get a rut in an orchard there will always be a rut. Lets take a look at the options.

To start there is little in the scientific literature concerning remediation or getting rid of ruts in orchards. The impact of compaction has been measured and we are just cautioned to avoid rutting and compaction. Several studies have measured the soil density in the trafficked inter-row areas. Not surprisingly, orchards do have denser soils over the tractor path - usually 2-4 times the width of the tractor tires - no matter how straight you drive. This soil density is something that accumulates over time with repeated trips to spray and harvest. See Figure 2.

Figure 2 - Flag height reveals the depth to which a wire rod can be pushed into the soil in the space between tree rows. The higher the flag, the more compact the soil is.

For now though:

• For badly packed and rutted areas – check your tile maps and take a look at your tile outlets to ensure that the tile are still running well. Rutting and compaction in lanes crossing tile runs may have compressed the tile.
• Scraping down packed lanes if soil moisture conditions allow, helps to level the lane and redirect surface water. Puddles and holes just get worse if you continue driving through them.
• Shallowly rutted areas of the orchard will level out with time and some scraping/leveling will happen during mowing. Freeze-thaw and winter rains will also help to break down the edges and fill in shallow ruts.
• Deeply rutted areas may need more extensive grading or tillage to make the area passable.
• Take a critical look at surface water flow in your orchard, some of the worst ruts are in areas that have some side hill seep or tend to accumulate water from adjacent rows – this may be a good spot for some gravel or even a French drain.
• For areas where ruts have formed on hills, some tillage may be needed to cover in the ruts and prevent the channeling of winter rains and spring melt water.

The best strategy will vary with each location based upon soil type, topography and a number of other factors. Keep in mind that we can expect soil conditions to continue to be wet with little real chance of drying at this point.

A final note:

In order to get a better handle on the impact of this years harvest conditions I have started to look at soil density in a few area orchards. The areas affected by rutting in the orchards measured to date vary greatly often being just a bit wider than the tires but may cover 30 cm+ where the track has not been followed completely. The depth of the ruts also varies widely from barely noticeable to more than 15 cm.

I hope to continue to measure a few more orchard ruts yet this winter and spring and then follow the soil conditions in the rutted areas for a few years. If you have a rutted or marked up orchard and are thinking of trying some different remediation strategies – please let me know.