Finding cost-effective weed and nutrient management practices in organic pear orchards


Investigator: Chuck Ingels, University of California Cooperative Extension, Sacramento County, Sacramento, California
Project location: Joe Green Ranch, Courtland, California (certified organic in 2009)

Photo of wood mulch treatment at Chris Frieder's organic Bosc pear orchardWeed control and nutrient management continue to be serious challenges in organic orchards, and the two are highly interrelated. Some weed control practices like mulching are more expensive, but they can have other benefits, such as improved fruit size or yield, that could more than pay for the practice. If it can be shown that mulching is cost-effective in a well-managed orchard, it is likely to be adopted by many growers. In-row mowing, although inexpensive, still leaves weeds that compete with trees for water and nutrients, but it could be the most cost-effective strategy. Knowing what fertilizer produces the best results and at what rate would also yield important information that will likely be adopted by growers. The results of this project will help growers make informed decisions based on the costs and benefits of these cultural practices.

This project compares in-row weed control and fertilization practices in an organic pear orchard in Sacramento County. The project originated with the grower cooperator inquiring about what practices to use. He is a third-generation pear grower, and his orchards are highly uniform and productive. It was initiated in fall 2008 in a uniform Golden Russet Bosc pear block, planted in 2001.

Specific objectives are:

  1. To compare the effects of in-row mowing, landscape fabric mulch, wood chip mulch, and organic herbicide on long-term suppression of weeds on the leaf water potential of trees.
  2. Measurable outcome: Increased yield and/or fruit size by the use of mulch or herbicide compared to mowing alone as a result of reduced competition for water and nutrients.
  3. To determine the effects of feather meal vs. two rates of chicken manure on leaf and soil nutrient content.
  4. Measurable outcome: Increased yield and/or fruit size as a result of improved tree nutrition.
  5. To determine the interactions of in-row weed management and fertilizer techniques on tree growth and reproduction.
  6. Measurable outcome: One particular combination is determined to produce the best balance of tree growth, yield and fruit size.
  7. To compare costs and evaluate cost effectiveness of various weed and nutrient management practices.
  8. Measurable outcome: Spending money on optimal weed control and fertilization practices leads to more profitable fruit production.