Light Management Using Reflected Light

It was great to see the good turn out at Simcoe in late June to look at the various research projects underway at the station. For many Ontario growers, it was the first opportunity to see the reflective ground cover technology that is gaining a lot of attention worldwide in temperate tree crop culture and in particular where apples are grown.

One of the continuing interests I have is that of light management. If we look at the limiting factors for total yield and recoverable yield of high quality fruit, light interception and distribution can make or break a planting. Under average conditions in Ontario, we normally underutilize the incoming light and have traditionally been unable to capture and use light that ends up going to the ground.

The different fruit production areas of the Northern Hemisphere are now familiar with the use of reflective blankets between tree rows. Jonathan Toye of Extenday mentioned that approximately 30% of the tree fruit acreage in the Hawke's Bay area of New Zealand now see treatment by these fabrics compared to almost none only a few years ago. On any given farm the grower will move the material from crop to crop and cultivar to cultivar depending on the wanted effect.

In Ontario, we have some experience with this type of technology, in our use of reflective mulches. Some Ontario growers have shown the effects of these types of treatments for several years now.

A lot of the orchards in New Zealand are very high yielding and report a rate of return on investment using the fabric shown in Simcoe of over 100% based on the usable life of the fabric. Under high light conditions these re-usable materials will last 30 months of in-orchard use.

The fabrics are normally handled mechanically as far as application and recovery at the end of the growing season. They are spooled out and retrieved by various motorized pieces of equipment. They can be easily moved from block to block using something as simple as a four wheeler.

A fastening system using bungee cords holds the fabric in place. The fabric is suspended over the sod and loose enough to allow air movement and wind action to throw dirt and debris off the surface of the material. Both air and rain water can move freely downwards into the soil.

This fabric comes in various widths, lengths and reflective properties to allow for custom fit into any planting. Some growers in the U.S. and elsewhere have opted for alternate row application, which drops the cost in half while maintaining the bulk of the benefits that arise from its usage on a per acre basis. Estimated costs range from about $500.00 - 3000.00 U.S. per acre depending on the width of the fabric and where it is used (one side, both sides of the row, fully covered or alternate rows only).

Figure 1 - Light reflective blanket manufactured by ExtendayŽ. The blanket has the ability to control light distribution in the tree canopy as well as helping to control evaporative water losses from the orchard ecosystem.

Benefits can vary from enhanced fruit bud development, fruit colour, sugars, recoverable yield, and water conservation. The attached figure (Figure 1.) shows the sod under the end of the blanket on July 19^th. The arrow indicates the line of division between treatments. The sod and soil under the blanket remain cool and moist while the control sod is more or less dormant and the soil would be considered to be hot and very dry. There is enough light going through the blanket material to allow the sod to live and yet not enough to have it overly vigorous and unmanageable. The fabric is tough enough to drive over. The sod is left unmowed for the time that it is covered.