Kale leaf nutrient density response to various mulches

View the project final report

• 2016 annual report

Commodities

• Vegetables: greens (leafy)

Practices

• Crop Production: conservation tillage
• Education and Training: on-farm/ranch research
• Natural Resources/Environment: soil stabilization
• Pest Management: mulches - killed, mulching - plastic
• Production Systems: general crop production
• Soil Management: organic matter, soil analysis, soil chemistry, soil quality/health

Applying a sheet of black plastic mulch is a common method of weed control when vegetable farming. However, this method of mulching is costly, relies on petro-chemicals for production, generates a significant volume of garbage, and does not contribute to improving the soil. The purpose of this study is to determine the impact of various mulches on kale plant nutrient content and to resolve key practical questions involved with using chipped slash as a crop mulch, specifically, analyzing a methodology to minimize the nutrient leaching effect of decomposition. Three types of mulch will be applied; light chipped slash mulch (2-3”), heavy chipped slash mulch (4-5”), and black plastic mulch. The timing of the chipped slash mulch application will be varied to observe the impact on soil nitrogen. For the Spring and Fall 2016 plots, half of the light and heavy chipped slash mulch will be applied several months prior to transplanting, and half will be applied days prior to transplanting. A Brix meter will measure the percent sugar by mass of one kale leaf every 20’ on three occasions in both the Spring and Fall plots, and a soil meter will determine the soil pH adjacent to each plant sampled. Particulate organic matter, soil organic matter, and soil carbon and nitrogen will be measured on three occasions in both the Spring and Fall plots. Outreach will include hosting a WAgN workshop at the farm, giving a talk at the PASA conference in February, pursuing being published in a peer-reviewed journal, and disseminating a press release on social networking platforms, in a professional organization newsletter, and on a local organic gardening radio show.

In effort to eliminate black plastic from our crops’ lifecycle, yet continue growing nutrient dense crops, we will investigate chipped slash as a mulch alternative. Chipped slash mulch without surface tilling will remove the need for cultivation with tractors and allow for more bio-intensive planting. With the current system of tractor cultivation on our farm, there are only two rows for planting. Not using a tractor for cultivation would allow for planting between the rows to occur as well, increasing production per area by a factor of 1.5. Furthermore, this will decrease diesel fuel usage, soil disturbance and compaction.

The purpose of this study is to 1) determine the impact of black plastic mulch and various chipped slash mulch treatments on kale plant nutrient content, and 2) resolve key practical questions involved with using chipped slash as a mulch, specifically, analyzing a methodology to minimize the nutrient leaching effect of decomposition.

Methods

All kale used in these experiments will be germinated in a greenhouse, four to six weeks prior to transplanting, as weather allows. There will be three types of mulch; light chipped slash mulch (2-3”), heavy chipped slash mulch (4-5”), and black plastic mulch. There will be 960’ of light chipped slash mulch, 960’ of heavy chipped slash mulch, and 640’ of black plastic mulch serving as the control, as this has historically been the chosen method of mulching kale on our farm. We will make note of weather conditions and collect data at the same time of day throughout the study.

A BRIX meter will be used to assess the percent sugar by mass for one kale leaf from a plant every 20’ in every row on three occasions in the Spring and Fall plots. Picking a leaf for measurement will occur approximately 80 days after sowing, 110 days after sowing, and 140 days days after sowing.  Thus, 128 measurements will be taken on three occasions for both the Spring and Fall crop. Each kale leaf will be folded and crushed, extracting the two drops of juice necessary to perform refractometry with a BRIX meter. BRIX is an inexpensive quantitative test indicative of taste and nutrition, which we have chosen to use for these experiments due to our farm owning a BRIX meter and our experience using it for previous studies.

To determine nutrient uptake ability we will measure the soil pH with a soil meter probe inserted into the soil directly adjacent to a kale plant. This measurement will be performed adjacent to one kale plant every 20’ at the time of transplanting, and, next to every kale plant a leaf is taken from for testing throughout the duration of the study. The location of these plants and their corresponding data points will be tracked to allow for comparison.

The timing of the wood chip application will be varied to observe the impact on the nutrient leaching effect of decomposition, specifically focusing on testing for nitrogen. For the Spring 2016 plot, 960’ of light chipped slash mulch and 960’ of heavy chipped slash mulch will be applied in the first week of May 2016, just prior to transplanting. All of the black plastic mulch will be applied in the first week of May. For the Fall 2016 plot, 480’ of light chipped slash mulch and 480’ of heavy chipped slash mulch will be applied in the first week of May 2016, and 480’ of light chipped slash mulch and 480’ of heavy chipped slash mulch will be applied in the first week of July 2016. Soil samples will be collected in May, July, and October from random locations within each individual mulch treatment, and tested for particulate organic matter, soil organic matter, and soil carbon and nitrogen.

After each session of data collection, the data will be analyzed and subsequently discussed with our technical advisor. As patterns emerge from the data enabling conclusions to be drawn, we will initiate targeted collection of soil and tissue samples for in-depth analysis to confirm trends or provide greater insight. Additional tests will be initiated as phenomena in the data are noted. Furthermore, close visual inspection of particular areas in the plots where data anomalies occur will be scrutinized to better understand site conditions.

Timeline

Third week of November 2015:

-Apply chipped slash; Spring plot

First week of March 2016:

-Sow kale seeds in greenhouse; farm apprentice;

First week of May 2016

-Apply chipped slash; Spring plot. -Apply chipped slash; Fall plot

-Apply black plastic; Spring plot; farm apprentice;-Transplant kale seedlings; Spring plot; farm apprentice;

-Measure pH; Spring plot;  -Collect soil samples; Spring and Fall plots;-Analyze data;

-Plant health inspections;

First week of June 2016:

-Plant health inspections;  -Sow kale seeds in greenhouse; farm apprentice;

First week of July 2016:

-Apply chipped slash; Fall plot; -Apply black plastic; Fall plot; farm apprentice;

-Transplant kale seedlings; Fall plot; farm apprentice;-Measure pH; Fall plot;  

-Measure Brix and pH; Spring plot; -Collect soil samples; Spring and Fall plots; ;

-Analyze data; -Data discussion;  -Plant health inspections;  

First week of August 2016:

-Measure Brix and pH; Spring plot; -Analyze data; -Data discussion;  -Plant health inspections;  

Third week of August 2016:

-Measure Brix and pH; Fall plot; -Analyze data; -Data discussion;  -Plant health inspections;  

-Host WAgN workshop

First week of September 2016:

-Measure Brix and pH; Spring plot; -Analyze data; -Data discussion;   -Plant health inspections;  

Third week of September 2016:

-Measure Brix and pH; Fall plot; -Analyze data; -Data discussion;   -Plant health inspections;  

Third week of October 2016:

-Measure Brix and pH; Fall plot; -Analyze data; -Data discussion;  -Plant health inspections;  

-Collect soil samples; Spring and Fall plots; -Prepare report

November 2016

-Send out press release for publishing

February 2017

-Talk at the PASA conference

Outreach plan

-Host a workshop with WAgN on the farm in August. Events for WAgN are advertised on their Facebook page, in the email newsletter, and verbally at prior events. Anticipated attendance is 20 individuals.

-Give a talk at the PASA conference during the first weekend in February. Anticipated attendance is 50-75individuals.

-Share the report on the Blackberry Meadows Farm website.

-Follow up with all of the research teams in our bibliography and share our work