Integrated Fruit Production, or IFP, is a production system well known to tree fruit growers in Europe. Orchardists in the Pacific Northwest are currently adopting this production system, particularly in the Dalles and Hood River areas of Oregon. The program gives priority to environmental and human health safety in the production of high-quality tree fruits.
IFP is more than just integrated pest management with a new name. It takes into consideration all aspects of tree fruit production, not just pest control. For example, in an IFP program, guidelines are established to assure that only prime orchard sites are chosen for tree fruit production; soil is prepared properly for planting; trees are appropriately fertilized; “soft” pesticides are given preference over broad-spectrum chemicals; and fruit is harvested in the proper manner, harvested at the proper time, and stored to maintain the highest quality possible.
In recent years, more domestic and international markets have started requiring producers and processors to certify their operation through one or more of the Good Agricultural Practices (GAP) programs that are currently available. These programs focus on food and worker safety as well as environmentally benign production practices. The most internationally recognized of these is Global GAP, a European program that provides member growers with access to many European markets. In the United States, USDA GAP is required for produce sales to the U.S. government. Others include SQF (Safety Quality Foods) and US GAP. In all, there are more than 35 of these programs available to producers in the United States. It is important for producers to work with their processors and marketers to determine if certification in any of these programs is currently required or if it will soon be required for market access.
Part of a good IFP program is proper ground cover management. Once again, European scientists and orchardists have taken the lead in determining proper management techniques for orchard cover crops in an IFP system. They use several techniques to reduce soil erosion and limit the use of residual herbicides, while still maintaining high-quality fruit production.
In mature European orchards, it is common to find a solid cover crop growing up to the trunk. It is important that young trees, up to the fourth leaf, become established with a weed-free zone around the trunk. However, European scientists believe that fruit size and quality are not reduced by a solid cover crop if it is mowed regularly to reduce competition for water, nutrients, and light. Although mouse damage is a potential problem, mowing the cover just before winter reduces or eliminates this concern.
Herbicide strips, when present, are small, constituting no more than 20% of the total orchard floor. Some IFP orchardists establish herbicide strips with herbicides in early spring. Because of the extended activity of residual herbicides, this class of herbicides is restricted in use or totally eliminated from the system. The continual use of glyphosate, however, is also not recommended due to herbicide resistance among weeds and the potential for tree damage. Strips vary in width depending on tree size but are always small. For dwarf trees, strips are typically 3 ft wide. Two applications of herbicide keep weeds away until late spring. After that, weeds are allowed to compete with the tree for nitrogen and, therefore, encourage better color on apples. In a well-maintained high density orchard, summer weeds are naturally suppressed by the trees’ shade. Occasionally, a postharvest application of a herbicide at half rate is made in the fall.
Research by Swiss scientists suggests the best treatment for fruit quality is a weed-free program only in early summer. Weeds are sprayed in mid-April with glyphosate. By mid- to late-summer, weeds begin to return. Weeds present in fall and winter help to reduce erosion and minimize nitrogen leaching. When weeds are killed the following spring, the nitrogen is released back into the soil for the tree’s use. To reduce the potential for herbicide resistance, a rotation or a mixture with another herbicide family is advised at some point during the year.
Swiss scientists also looked at the weed control potential of different mulches. At the research farm in Guttengin, where annual precipitation is 32 inches, fruit quality and quantity were best when a fabric row cover was placed under the trees. Tarp edges were buried 2 inches in the ground to hold it in place. Scientists found that plastic provided higher temperatures, more moisture, and better nitrification than other products. However, in Wadenswil, Switzerland, with annual precipitation of 48 inches, results were negative: Roots were asphyxiated because too much water was held in the soil around the tree.
Research at the OSU Mid-Columbia Agricultural Research and Extension Center in Hood River, Oregon, has found that woven fabric ground covers installed under cherry trees significantly reduced the need for herbicides and improved horticultural attributes. Fifth-leaf ‘Regina’ trees on Gisela 6 rootstock had greater vigor, branching, and canopy spread and higher foliar nitrogen content compared with trees growing without row cover. In addition, water usage was reduced by 30% while yields were increased by 48% with no difference in fruit quality (Roberto Núñez-Elisea, personal communication). These benefits rapidly help pay for the cost of the material and installation.
In areas where tree fruit production is limited by irrigation needs, such as Australia, growers often apply straw mulch around their trees. Applications of 4 to 6 inches of wheat straw are made in the spring in the herbicide strip area. The straw reduces weed growth, reduces water needs by 20%, and adds organic matter to the soil as it decomposes. One application can last several years. Rodent control must be actively pursued with this system to prevent tree damage. When using any of these mulches, it is important to closely monitor irrigation levels to prevent root asphyxiation from overirrigation.
A recent study conducted by OSU scientists near The Dalles, Oregon, compared straw mulch with black and white woven fabric ground covers in a cherry orchard. The research identified a trend in yield increase over 3 years with straw mulch and fabric covers relative to no cover, but not to the level of statistical significance. In addition, straw mulch, black fabric, and white fabric cover increased the percentage of marketable fruit in some years. In this same study, straw mulch reduced annual water use by 4.6% and 15.8% over a period of 2 years. Even in low-precipitation areas, such as The Dalles, Oregon, growers using textile groundcovers under their trees find it necessary to reduce irrigation to prevent tree damage.
Scientists working in Hood River, Oregon, have found that black textile groundcovers increase tree size and precocity in young trees. Mid-Columbia area growers have found that textile groundcovers significantly reduce herbicide and water use, as well as labor needs.