Application of Brassica Meal for Disease Control and Improved Nitrogen Fertility in
Organic Farming Systems
Notes:
This site is constantly being update as research results become available. Please check back from time to time for updates.
The authors of this website would like to acknowledge the Organic Farming Research Foundation for supporting this research. More information about the OFRF can be found at: http://www.ofrf.org/
Investigators and cooperators:
Jodi Johnson-Maynard, Matthew Morra, Louise-Marie Danurand, Mary Jane Butters, Cinda Williams
Project summary:
Organic farming represents a major challenge to growers who need to control plant pathogens and manage nutrients without the use of synthetic chemicals and inorganic nitrogen (N) fertilizers. New methods of biologically based pest control are needed to improve the economic sustainability of organic farming. It has long been recognized that plants in the Brassicaceae family (canola, mustards, broccoli, etc.) produce chemicals called glucosinolates that form isothiocyanates (ITCs) in soil. Isothiocyanates are biologically active compounds that have been used to help control pathogenic fungi, nematodes, and insects in agricultural systems. The use of Brassica green manures is one approach to control pests while adding N to the soil, however green manures are not applicable in areas with short growing seasons. Current research at the University of Idaho is concentrating on all aspects of Brassica crops, from breeding to the production of biofuels. To produce biofuel, oil is extracted from the seed in a press. The byproduct of this extraction is a meal that contains high glucosinolate concentrations and more N than most traditional organic soil amendments. We propose to apply meal from two Brassica species, B. juncea (a high glucosinolate containing mustard) and B. napus (a low glucosinolate containing canola because it has a similar N content) to test efficiencies in controlling plant disease and improving N fertility on a certified organic farm. Specifically we will:
- Determine the influence of this material on N cycling processes in organic systems.
Methods:
The experimental design is a randomized complete block with
five blocks. Each block contains the following treatments: B.
napus (BN) at 1%, BN at 3%, B. Juncea (BJ) at 1%, BJ at 3%, and a
control (no meal). The meal used is shown in Figure 1. Each plot is
surrounded by a buffer strip and is 4' by 4.5' (Figure 2). Plots were
established in April 2002. Prior to the application of meal, three soil
samples were taken from each plot and will be analyzed for total carbon (C) and
nitrogen (N) as well as mineral or plant available N (ammonium and
nitrate). The meal was incorporated to a depth of 2 cm using a
rototiller. Lettuce and beets were seeded in the plots 13 days after the
application of meal.
Figure 1. B. juncea and B napus meal. Figure 2. Meal before incorporation.
Preliminary Results:
Lettuce germination was extremely poor in the meal amended plots. Figure 3 shows the lack of lettuce and weed growth in the plots as compared to the buffer zone. The lack of lettuce growth and weeds suggested that the lettuce was planted too soon following meal application and that residual isothiocynates were present in the soil. Weed biomass was measured in each plot to determine the effectiveness of meal in controlling weeds. Due to the poor germination rates, existing lettuce and beets were removed by hand and all plots were replanted 40 days after the meal was applied.
Figure 3. Lack of germination in meal amended plots. Note differences between the distribution of weeds in the meal-amended and non meal amended plots.
Measurements of weed biomass on June 25, 2002 indicate that treatments of 3% B. napus and B. juncea at 1 or 3% inhibited the growth of weeds compared to the standard treatment. By the July 15th sampling there seems to be no significant influence of meal application at any rate on weed biomass. This preliminary data suggests that applications of meal in organic systems may be an effective tool for controlling early season weeds. Future work conducted at the University of Idaho will concentrate on finding the most efficient application rate of meal for weed control purposes.
Figure 4. Total weed biomass in plots treated with B. napus or B. juncea at 1% (1%BN, 1%BJ) and B. napus or B. juncea at 3% (3%BN, 3%BJ) as compared to the weed biomass in the standard treatment (no meal). Measurements were made on A) June 25 and B) July 15, 2002.
Last updated: July 18, 2002
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