Maintaining nutrient levels for optimal yield in high tunnel growing

by Noah Berliner
Seth Jacobs’ 130-acre farm in Argyle, NY takes advantage of the watershed that offers a natural resilience to flooding. Seth has been certified organic throughout his farming career. Among his most economically viable crops are tomatoes. With the northeast area offering only a short-season for outdoor tomato crops, the use of high tunnel systems has allowed him to expand his season as well as offering a variety of other benefits to production and sustainability. For the past four years, a collaboration between NOFA-NY and the Cornell Cooperative Extension has collected samples from over 40 farms utilizing high tunnels through a New York Farm Viability Institute funded project to gather data on soil and nutrient levels to balance nutrients for optimal yield and performance.
Use of high tunnel has doubled in the past years with the National Resource Conservation Service offering options to subsidize construction. Seth finds that his highest value crop — tomatoes — yield better inside, and he gets an average of a 40 percent increase in gross sales per square foot using high tunnels.
Tunnels provide a variety of benefits that go along with the amount of automation and input put into the system. They offer a pest management solution as well as some protection from the elements. Seth’s system includes the placement of HAF fans for circulation rather than exhaust as well as nutrient injection through his irrigation system and heating pipes beneath the tunnel to extend the season further.
High tunnels, in order to remain sustainable, require a stricter nutrient management solution than outside crops. The combination of a lack of rotation and high output requires a higher input of nutrients to maintain the desired yield. NOFA-NY and the Cornell Cooperative Extension have been collecting data to show the benefits to soil testing and foliar testing crops in high tunnels to maintain nutrient levels for optimal yields.
Even when nutrients are available, the competition over intake might cause problems for flowering. While many farms using high tunnels, especially those using organic methods, should prepare for an early spike in nitrogen, an overabundance in the beginning of the season might lead to reduced flowers. Potassium as well should be monitored as too much often leads to uptake competition that, without attention to soil and foliar tests, can lead into a nutrient spiral.
While foliar testing allows a more accurate analysis of the needs of a specific crop, maintaining soil health is necessary for optimal yield. The “nutrient spiral” is a problem found in high tunnel crops caused by a competition over uptake between nutrients. For example, while viable short-term, use of traditional dairy compost in a tunnel can cause an abundance of phosphorous. Phosphorous when over abundant in the plant can cause a difficulty in potassium intake. If more potassium is added to the soil, creating an overabundance, it will cause problems with the intake of other nutrients. Instead of solely relying on soil testing, foliar testing provides data on the nutrients already taken in by the plant, preventing a situation of over enrichment in the soil when the issue is intake rather than availability.
Mineral soil tests are still utilized often. Influences such as the high pH and calcium bicarbonate content of well water can restrict uptake of nutrients as well. NOFA-NY has approved online sources for organic solutions, such as citric acid that keeps the pH lower by breaking up excess calcium bicarbonate. Cornell Cooperative Extension offers services to test the pH of your well water or other irrigation source. Contact Amy Ivy at Adi2@cornell.edu for more information and to provide a sample.
Foliar testing should begin at 10 days after transplant and continue every two weeks after that. The first fully mature leaf, generally about five rows from the top, should be snapped off as a whole leaf, gathering about five from the row. At a cost of about $15, foliar testing allows detailed micro- and macro-nutrient testing for what is in the plant rather than just the soil. This data allows for a comparison of nutrients and the ability to identify between a lack of availability, a competition over intake and the specific needs of a crop.

2017-09-01T12:21:50+00:00September 1st, 2017|Grower East|0 Comments

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