June 20, 2014
7 Organic Fertilizers for a Fruitful Orchard - Photo courtesy Morgan Paul/Flickr (HobbyFarms.com)
Courtesy Morgan Paul/Flickr

Improving productivity and tree health in an organic orchard is more than taking a soil sample and trying to add what the trees lack. While a soil sample is a good place to begin, understanding the nuances of the life of an orchard is different than growing annual vegetable crops.

“The goal at the farm is to see worms in every scoop of soil I take,” says John Kinsley of Alternative Roots Farm in Madelia, Minn.

He’s certainly on to something.

Orchard soil rich in worms means it’s also rich in nutrients and organic matter. If you’re not seeing worms in your orchard, it could be an indication of a bigger problem that will affect the quality of your orchard harvest. Here are seven ways to give deprived orchard land the nutritional boost it needs to keep you swimming in fruit and nuts all summer long.

1. Mulch
Mulch is an important tool in weed suppression, but it also offers an impressive nutritional benefit to the orchard.

“It looks like there is a much bigger benefit when we [apply] mulch on the surface versus compost in the soil,” says David Granatstein, sustainable agriculture specialist at Washington State University. “If you think about it, a forest typically has a little layer on the surface. Maybe that’s what we’re recreating.”

Granatstein recommends using wood chips that are big and chunky to provide a physical covering of the soil. Kinsley, on the other hand, applies ramial wood chips, made from the tips and smaller pieces (less than 4 inches in diameter) of tree and shrub branches, which contain more nutrients than the heartwood. By supplying the orchard soil’s microbes the nutrients they need to thrive, they, in turn, make the nutrients available to the trees.

Add a 2- to 3- inch layer about 2 feet wide along the drip line of your trees, allowing the grass to come through the chips. The chips will break down over the course of the growing summer, and you shouldn’t see any evidence of mulch the following spring. Don’t worry about the decaying wood chips tying up nitrogen in the soil because they will remain on the surface.

2. Compost
Around the base of young trees, Kinsley uses composted straw to suppress grass and provide nutrients to soil microbes. However, adding 1 to 2 inches of compost at any stage in a tree’s life adds organic matter, which is the key to healthy soil.

Composted manures from rabbit, poultry or steer can also organic matter to the soil, as well as nitrogen. According to the UC Davis Home Orchardist, an application in late August to mid-September is more effective than the more traditional application in late winter.

3. Cover Crops
Although it’s not a simple amendment solution, cover cropping in the orchard is worth the effort and has shown to increase fruit production. Perennial legumes are one of the most promising cover crops because they increase nitrogen availability in the soil.

Plant cover crops in the orchard’s drive alley so they don’t compete with the trees’ root systems. Mow the crop before it goes to seed, and leave the clippings in place.

A significant drawback to utilizing cover crops is that it provides an ideal habitat for voles. Granatstein is looking at more ways to dissuade the voles while maintaining the drive-alley cover crop system, including planting sweet woodruff (Galium odoratum), which has shown to help minimize vole pressure.

4. Fish Emulsion
Fish emulsion can be used as a general NPK fertilizer. It provides plenty of nutrients, has some minerals and won’t burn the trees in the process. Kinsley sprays fish emulsion on the foliage twice a season and only during fruit production, when trees are expending the most energy.

5. Bone Meal
Use bone meal to give newly planted trees a phosphorus boost. Add 3½ pounds around the tree or in the hole at planting time without concern of burning the roots.

6. Comfrey
Apples that lack access to calcium often get a disease called cork spot. Mineral sprays can sometimes damage trees, so only apply a calcium supplement if there is a known deficiency.

A way to ensure your orchard trees receive the calcium they need without the risk, companion plant with comfrey, which will pull calcium from the soil and make it available to the tree. Plant comfrey along the drip line, and as it reaches maturity in early to mid-summer, cut the plants and leave the cuttings in place. They release the calcium back into the ground where the tree can utilize it.
 
If you must use a calcium supplement, apply a foliar spray using food-grade calcium carbonate every couple weeks starting three weeks after the petals fall until the apples are ready.

7. Sulfur or Lime
Applying sulfur or lime to the orchard will help you adjust the soil pH. Sulfur decreases the pH (creating a more acidic soil), while the lime increases it. How much you apply depends on the pH of your soil, the desired pH level and the soil texture. Sandy soils, for example, require less of the amendment than clay soils.

Getting a good soil test will tell you exactly how much to use, but don’t apply if rain is in the forecast.

“Elemental sulfur in the presence of water makes a weak sulfuric acid that can burn roots if plants are present,” says Guy Ames, horticulturist with the National Center for Appropriate Technology. “This is possible, but not common, because once in the soil solution, the sulfur is recombining with other elements and becomes neutralized. Lime generally doesn’t cause any such problem, but hydrated lime can easily burn plants at a high application rate; however, the most common agricultural liming materials (like simple crushed limestone, calcium carbonate) are very safe to use.”

There are myriad minerals and other amendments you can use on your home orchard in an attempt to improve the health of your trees and increase production. The first step is to create a healthy soil, and then fine-tune what your trees need.

Continue building healthy farm soil with these tips:

About the Author: Freelance writer Amy Grisak relies on her pressure canner to put up much of the food from her garden. You can follow her endeavors on www.thebackyardbounty.com.

 



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