Brassica nitrogen dynamics: Fertility planning and seasonal N carryover

As this season is winding down and planning for next year begins, it’s a great time to consider nitrogen applications for your brassica crops as well as what nitrogen credits are made available to the crop following your brassicas.

There’s tremendous variability in the rates and application methods that growers use. Many fail to maximize the efficiency of their fertilizer by applying it at times when the crop doesn’t need it but weeds will hungrily accept it.

Most brassicas have similar seasonal N uptake demands, as depicted in the graph below (fig 1.), which plots nitrogen uptake over a typical cauliflower growth cycle. You can see that N demand dramatically increases around 25 days after transplanting, and 75% of the plant’s nitrogen needs are during the last half of its lifecycle.

Fig 1. Cauliflower seasonal N uptake [1]

Recent research from Cornell shows that when growers apply the same rate of fertilizer but choose to split-apply their nitrogen instead of only applying pre-plant, average yields increased by close to 5% representing an increase from 32.8 ton/A to 34.2 ton/A ^[2]. Across multiple farms and three years of study, the researchers found a 50:50 ratio of fertilizer application (at-planting : side-dress) produced the greatest yields when the side-dress application was banded at 30 days after planting.

By split-applying your nitrogen, not only are you matching your fertility to the demands of the crop, you are also minimizing the fertility available to your weed bank and reducing losses through leaching. And, by banding your fertilizer, the nutrients in the areas between rows are minimized whilst your brassica crop has maximum availability.

Brassicas, especially cabbage, are excellent N scavengers. This coupled with the fact that much of the plant is left in the field after harvest means that you can expect residual N the following year of up to 10 lb/A. A typical cabbage crop requires 200 lb/A of N over a growing season. After harvest, there is roughly 100 lb/A in the leaves, stump, and roots left on the field. This residue breaks down and is mineralized, ready for plant uptake the following season. Plant available N levels the season following cabbage averaged 8-10 lb/A ^[3]. This might not seem like much, it’s clearly no legume—but it’s definitely worth considering as fertilizer costs steadily climb. 

 

Tim Morcom

 

  

References:

[1] UC Davis, Cauliflower uptake and partitioning, http://geisseler.ucdavis.edu/Guidelines/N_Cauliflower.html#References

[2] Hoepting. C, Understanding Nitrogen Use In Cabbage: New York Study, CCX Cornell Vegetable program, https://rvpadmin.cce.cornell.edu/uploads/doc_857.pdf

[3] Hoepting. C, Understanding Nitrogen Use In Cabbage: New York Study, CCX Cornell Vegetable program, https://rvpadmin.cce.cornell.edu/uploads/doc_857.pdf

 

Protected culture fertility survey!

Growing crops under cover is a separate skillset compared to growing under the open sky.  Fertility management, integrated pest management, environmental management are all very different.  Last year a survey went out to find out more about the protected culture industry in Nova Scotia.  To drill deeper on the learnings from that survey, Rosalie Gillis-Madden, Perennia's Vegetable Specialist, Talia Plaskett, Perennia's Protected Crop Specialist, and Caitlin McCavour, Perennia's new Soil Specialist would like to identify where there are knowledge gaps and pain points in protected crop production, specifically targeting fertility management.  Our goal is to determine where outreach and support might help the industry move forward and how we might serve you better.  This applies to growers who grow in soil or in substrate, who use conventional fertility or organic nutrient sources (composts, manures, organic fertilizer, etc.)  Please take the time to complete this survey to help us determine how we might best support growers, it should take you about 10 minutes to complete.

The mission of Perennia is to help farmers, fishers, and food processors be prosperous and profitable.

Soil salinity in Nova Scotia high tunnels

When evaporation from the soil surface and transpiration from plants exceeds water input, salts can start to accumulate at the soil surface. This is because when water from the soil surface evaporates, it wicks salts that are suspended in the soil solution to  the soil surface.  This is particularly a problem in high-tunnels that are in production year-round.  

Accumulating salts are not just sodium (Na⁺) and chloride (Cl^-) ions, but are also essential plant nutrients... calcium (Ca²⁺), magnesium (Mg²⁺), potassium (K⁺), ammonium (NH₄⁺), hydrogen (H⁺), phosphate (HPO₄^2-), sulfate (SO₄^2-), and nitrate (NO₃^-) are all salts. Nitrate accumulation is particularly frequent in high tunnels as high-value crops are well fertilized, and since there is no rainfall to leach the nutrients, they accumulate year after year.

To learn more about soil salinity, how it happens, and what you can do about it, please read Perennia’s factsheet: http://www.perennia.ca/wp-content/uploads/2015/12/Soil-Salinity-NS-Hi-Tunnels.pdf 

Building Agriculture Resiliency from the Ground Up! - March 16, 2017 - Yarmouth, NS

Join Perennia specialist Rosalie Madden for this free workshop on building agriculture resilience from the ground up! Topics discussed will be soil health, cover crops, soil management, maximizing fertility, and the importance of organic matter.

Building Agriculture Resiliency from the Ground Up!

Thursday March 16, 2017

Rudders

96 Water Street, Yarmouth, NS

11:00 a.m. - 3:00 p.m.

Don’t be late, because we plan to cover a lot of ground!

Please contact Terry McKay at 902-638-2396 or Terry.McKay@novascotia. ca, or Gail Walsh 1-877-710-5210 (toll-free) to register by March 13, 2017.

Lunch is not included in the workshop but can be purchased on site.

Compost Tea

Perennia hosted a workshop on Tuesday, May 17^th, 2016 at the Wolfville Farmer’s Market.  In attendance were some of Perennia’s summer students.  Jonathan Bent, Tamara Dondi, and Jessica MacDonald have written up a brief overview of the morning’s discussion.

Dale Overton, President of Overton Environmental Enterprises Inc. (OEE) situated in Manitoba, held a talk in Wolfville, NS outlining the science behind Eco-Tea. Eco Tea is actively aerated compost tea, infused with an organic blend of humic and fulvic acids, Atlantic kelp extract, complex carbohydrates and enzymes.  Humic acid can be found in compost and acts as a chelating agent, which increases the availability of nutrients to plants and prevents nutrients from leaching.

Eco-Tea is made from four different types of compost. To reduce the number of pathogens, the compost goes through a thermophilic stage where it is heated enough to work against the growth of pathogens.  When making the compost it is essential that air (oxygen) is allowed to move through the pile because anaerobic conditions (no oxygen) favour the development of disease. The compost aims to support the growth of a complex microbial community which will outnumber pathogenic organisms.

A broad definition of compost tea is that it is a liquid extract of compost. In general, compost tea contains nearly 20,000 different species of microorganisms. Similar to when making compost, the goal when brewing compost tea is to produce conditions in which beneficial microbes can grow.
Other things can be added to the tea as well, such as grain meals (food for the microbes), minerals, and bio-stimulants.  Bio-stimulants are not added to the compost until the end to allow enough time for the beneficial organisms to build a complex community. 

If a fungicide is being applied, Dale recommends waiting to spray the tea for 5 to 7 days to limit the detrimental effect of the fungicide on the beneficial microbes in the compost tea.  Sprays should go on either before 10:00 am or after 6:00 pm using a field-jet nozzle, with no filters. For transplants, he recommends a 50:50 dilution in water.

For more information about compost tea, please check out this eXtension webinar: http://articles.extension.org/pages/73211/making-and-using-compost-teas

*** Note that compost teas can pose a food safety risk. To minimize the food safety risk, only use compost tea produced under conditions that are not a source of biological (e.g., pathogens), chemical (e.g., heavy metals) or physical (glass) contamination, and with a documented composting procedure.  Compost teas are approved for use under the CanadaGAP Food Safety Program but their use does require that a letter of assurance from the supplier be filed with the CanadaGap records. For additional information refer to Section 4 and Appendix C of your CanadaGap Manual. ***

Under the Covers: Enhancing Profitability and Resiliency with Cover Crops

Cover crops are going to become increasingly important in the face of our changing climate.  Predictions for our region are that we are going to be facing more intense rainstorms with longer dry spells in between, something that we have certainly seen this year.

Intense rainstorms after a prolonged dry period often results in what is called overland flow; basically the water runs off the field in sheets and doesn't infiltrate the soil.  When this happens, soil often gets taken with the flow of water, causing erosion and exporting nutrients, resulting in economic loses to the farmer, and nutrient loading of our waterways.  Cover crops improve soil health and one of the ways that they do this is by increasing the permeability of the soil: instead of the water sheeting off the field, it infiltrates.  Cover cropping and good soil health will also help a crop withstand prolonged dry periods by improving moisture retention.

Please join us to learn more at Under the Covers: Enhancing Profitability and Resiliency with Cover Crops, a workshop for farms of all types and sizes, on Tuesday, September 15th in Room 214 at 90 Research Drive in Bible Hill, Nova Scotia.

9:00 AM     Registration/Coffee
9:15 AM     Welcome
9:30 AM     Why Cover Crops - David Blanchard
10:15 AM   Meet the Cover Crops - David Blanchard
10:45 AM   Online Decision Making Tool - David Blanchard
11:15 AM   Cover Crop Economics - David Blanchard
11:45 AM   Nitrogen Mineralization of Cover Crops - Rosalie Madden
12:15 PM   Lunch Provided
1:15 PM     Alternative Cover Crops for Strawberry Rotations - Dr. Nancy McLean
1:45 PM     Novel Cover Crops and Root Morphology - Amy Sangster
2:30 PM     Soil Health, Structure, and Aggregate Stability - Jason Stuka
3:15 PM     Green Manures and No-till - Carolyn Marshall
4:00 PM     Wrap up

To register please call Gail at 1-877-710-5210 (toll-free) or 902-678-7722 (local) by Wednesday, September 9, 2015.

 
A portion of the day will be in the field; please dress accordingly.