Best management practices for organic orchard nutrition

Best management practices for organic orchard nutrition

Summary

In the first year of this three-year project achievement towards projects goals were accomplished. In 2006, an organic producer survey was conducted to determine organic management practices, collaboration was established with producers for on-farm nutrient status studies, and a controlled study orchard infrastructure was installed and trees were planted in the UA organic research orchard following orchard protocols. The producer survey indicated that most producers test their soil on a regular basis for nutrient status, although foliar analysis was infrequent. Common nutrient sources applied in organic orchards were composted manures and mulches. Soil and foliar samples were collected from cooperating producers and recommendations were developed and given to the producers at the end of the season. The UA organic research orchard was established to evaluate the interaction of ground cover management system (municipal green compost, wood chips, recycled shredded paper, and a mow-and-blow grass mulch) and nutrient source (control, composted poultry litter, and formulated palletized poultry based fertilizer). During the establishment year, soil, leaf and tree growth variables were measured and treatment effects observed. However, because this was the first growth season, the importance of the effects is yet to be conclusive, but will become evident in future seasons.

Objectives/Performance Targets

The goal of this project was to develop an understanding of nutrient management practices among organic and ecologically based Southern apple producers, and to develop organic nutrient management recommendations through the evaluation of seasonal soil and foliage nutrient content and of the ground cover management and organic fertilizer treatment interactions. The specific objectives are listed below.

1) Identify successful nutrient management practices currently being used by organic fruit growers in the South.

Results from a survey of ecologically based apple producers in the Southern region have been collected and analyzed. Survey results include information on groundcover, fertilizers, weeds, mulches and orchard productivity.

2) Work with Southern region organic tree fruit growers to assess the impact of their nutrient management practices.
Soil and foliar samples were collected from 2 ecologically based apple producers to determine the nutrient status of their orchards.

3) Conduct a controlled, replicated study to further evaluate ground cover and nutrient management practices and develop locally-appropriate recommendations for organic fruit tree growers in the South.
An organic apple orchard has been planted at the University of Arkansas to examine the effects of 3 nutrient source treatments and 4 groundcover treatments in a replicated study. Soil and foliar samples are being collected monthly for chemical, physical and biological effects of treatments.

Accomplishments/Milestones

A. Producer survey.
A survey was developed to determine organic nutrition management practices, including testing practices among organic apple producers in the southern region. A mailing list of 41 organic apple producers in AL, AR, GA, FL, MO, NC, OK, SC, TX, and VA was developed from information from private and state certification agencies, word of mouth, the certified naturally grown website, and other websites such as localharvest.org.

The surveys were sent to the list in March, 2006, and followed-up with reminder emails and postcards sent in April and May. Despite these efforts, only 7 (17%) completed, useable surveys were returned. An additional 5 producers responded saying they were no longer in business. Of the returned surveys, 2 producers agreed to participation in the soil and foliar testing program during the summer of 2006. None of the survey respondents were certified organic but all used organic practices. Most of the producers (85%) indicated orchard size was increasing and 3 indicated their orchards were new and not producing. All of the producers stated that nutrition was important to orchard productivity and 85% conducted bi-annual or annual soil testing. Few producers, however, used foliar nutrient analyses on a regular basis. The most common symptom of nutrient deficiency reported was small fruit size (42%). The most common types of nutrients applied included composted mulches (71%), composted manures (43%), rock minerals of phosphate (43%) and calcium (43%), boron (43%) and magnesium sulfate (43%).

B. Producer soil and foliar nutrition survey.
As a result of the apple producer survey, 2 apple producers, employing organic practices, were identified and agreed to monitor soil and foliar nutrients in their orchards. The plan to receive monthly samples was too ambitious goal, as producers were only able to submit 2 samples during the season. Greater efforts will be taken to target additional cooperating producers willing to participate in the project and to collect a greater number of samples for the coming seasons.

C. Organic apple research orchard.
In early spring 2006, trellising (modified vertical axis training) and irrigation (micro sprinkler) infrastructure was installed to support 450 apple trees in an organic production system. Trees of ‘Enterprise’, ‘Freedom’, ‘William’s Pride’, ‘Galarina’, and ‘Goldrush’ were planted March 15, 2006. Enterprise (M26) is the experimental cultivar, while the remaining cultivars compose the guard rows and provide both buffers and opportunity to evaluate disease resistant cultivars in an organic production system. Trees were fertilized with the 3 nutrient source treatments: 1) control – no fertilizer, 2) commercial organic fertilizer (Organic-gro, Springdale, AR) and 3) 1 yr composted poultry litter (Poultry Science Department, Fayetteville AR). After fertilizer application, 4 ground cover management treatments were applied: a 10cm layer: 1) wood chip mulch, 2) municipal compost, 3) paper mulch and 4) a mow-and-blow grass mulch system where the under-story biomass is mowed and then blown into the tree row. A sorghum sudangrass cover crop over K-31 fescue was planted in the mow-blow plots on May 20 at a rate of 40lb/ac. Soil samples for baseline analysis was collected prior to orchard establishment on August 15, 2005. The following data were collected throughout the first growing season.

TREE GROWTH VARIABLES: Tree height and height increment (monthly from April to Oct.); TCA (trunk cross sectional area), shoot extension and root weight (each, annual measurements)
LEAF VARIABLES: Leaf nutrient concentrations, leaf characteristics (leaf area, leaf specific weight, etc), and leaf chlorophyll (each, annual mid-summer measurements)
SOIL VARIABLES: Soil nutrient concentrations, soil ph, EC, organic matter (measured monthly from April to Oct); soil solutions (measured every other month from June to Oct), soil PRS probe (from Sept 7 – Oct 6), soil infiltration, soil bulk density and soil water content (each Oct measurements), weed density (monthly from April to Oct), soil water tension (weekly from May to Aug).

Since this was the establishment growing season of a perennial system, no conclusions can be determined at this time. Some trends have been identified however future years will determine the strength of these first year results.

Impacts and Contributions/Outcomes

In the first year of this project several outcomes and impacts have been made. Through this project:
1)The organic orchard practices used by growers in the Southern U.S. were identified
2)Organic producers were supported and provided guidance and consultation for their nutrition management decisions through nutrient analyses and recommendations.
3)A new organic research orchard was planted for long-term study and the soil content, nutrient flux, and plant nutrient uptake, as affected by ground cover management system and nutrient source, evaluated.
4)The organic research orchard soil and plant nutrient contents, and plant growth and development were studied and are continuing to be studied through the transition phase to an equilibrium in a perennial organic production system.

Collaborators: