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Graduate Student Tests Organic Chile Fertility

Laura Johnson of New Mexico State University is studying plant growth, fruit yield, and quality

by New Mexico State University
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New Mexico State University horticulture graduate student Laura JohnsonNew Mexico State University horticulture graduate student Laura Johnson looks over her chile plot at the Fabian Garcia Science Center. Johnson is studying three types of organic fertilizer.Photo credit: Kristie Garcia, NMSUThe aroma of freshly roasted green chile will soon be in the air. It’s that time of year when you see plump, green chiles in nearby fields. But which type of organic fertilizer will produce the best green chile?

You may soon know the answer from a graduate student at New Mexico State University.

Laura Johnson is in the horticulture program at NMSU. She is researching the effects of organic fertilizers on two hybrid long green chile varieties. Specifically, she is studying plant growth, fruit yield, and quality.

Her project includes both a plot in the field and plants in the greenhouse at NMSU’s Fabian Garcia Science Center not far from campus. She is experimenting with three types of fertilizers: compost, processed chicken manure, and compost tea.

Yes, tea.

To make the tea, Johnson first dries the compost in an oven. She then places the compost in a mesh container and soaks it in water. The water is in a container with a bubbler that aerates the compost and the water mixture for 24 hours. The result is a liquid nutrient extract. She filters the liquid twice and applies it to the chile plants through a drip irrigation line.

This process is known as fertigation, in which fertilizer is added to a water supply and applied through an irrigation system.

Related Article: New Chile Pathogens Discovered in Australia

Another fertilizer method she’s testing is heat-treated chicken manure pellets. The manufacturer dries the manure until it reaches a powdered form. It’s then compressed into small pellets so that it may easily be distributed by various machines.

“My inspiration for this project came from time I spent in the Peace Corps in Paraguay,” Johnson said. “I worked with small-scale farmers, and some of the work that we did together was using compost teas.”

Green chilesGreen chilesNMSU courtesy photoShe also went to Costa Rica last year, where she toured projects related to compost tea that’s being used for various crops. While there is some research on liquid extract and teas as organic fertilizers, Johnson hopes to add to that literature.

In the long run, she wants to help farmers by determining what the best fertilizer is for green chile.

“There are not many options right now for organic green chile producers and types of fertilizers they can use,” she said. “And there are even fewer options for liquid fertilizer.

“Green chile production requires a little bit more nitrogen throughout the season to ensure robust second harvest fruit development. So being able to apply it in liquid form allows farmers to provide more nutrients throughout the season in an easier way.”

Johnson is working under NMSU Extension Vegetable Specialist Stephanie Walker. Walker said this project is important because of the increase in demand for organic produce.

“Demand for organic produce continues to rise, and that includes a desire for organic New Mexican green chile,” Walker said. “One of the challenges for producers is providing optimum fertility for a green chile crop in an organic system, especially if the grower fertigates through drip irrigation.

“This project was an initial step in investigating the feasibility of using compost tea, brewed from locally sourced, organic compost, for green chile fertigation.”

Related Article: Using Fungi to Decrease Need for Chemical Fertilizers

While Johnson emphasized that she’s not growing the plants on certified organic land for her study, she’s following requirements of the United States Department of Agriculture National Organic Program.

“The findings from my project may be used by certified organic growers; I just can’t label these chiles USDA organic,” she said.

Growers have another tool they may find useful. NMSU recently published the Field Production of Organic Chile bulletin. Authors include NMSU senior research assistant Chuck Havlik, assistant Professor Kulbhushan Grover, regents professor Paul Bosland, and Walker.

Intended primarily for producers, the publication is available at county extension offices and on-line at

Following are some tips for growing organic chile, according to Grover:

  • Only growers certified through the USDA organic certification process may legally advertise as organic
  • Select an appropriate site that is free of prohibited materials
  • Use a level field
  • Build up soil fertility
  • Use a layer of mulch
  • Avoid chemicals, except those approved by the Organic Materials Review Institute
  • Have a good crop rotation plan
  • Choose a field with fewer weeds to begin with and/or use organic herbicides

This is the second chile season of Johnson’s study. She will receive her master’s degree in December.