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Identifying the SIX Critical Control Points in High Tunnel

Production Terrance T. Nennich, Extension Professor Emeritus

Vegetable and Small Fruit Production University of Minnesota Extension

[email protected]

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© 2012 Regents of the University of Minnesota. All rights reserved.

High Tunnel Research Sites in Minnesota

Experiment Stations Grower Cooperators


"It's probably more appropriate to look at high tunnels as creating a system, rather

than being an individual technique, because of what they do. They're simple

structures but they create a different farming system. Fertilizer use, crop

protection use, water, equipment use -- they all change.”


What are Critical Control Points

• Critical control points are areas of

management that can lead to serious and drastic consequences if not recognized and properly regulated.


SIX Critical Control Points

1. Soil texture and soil structure 2. Soil Fertility 3. Water management 4. Temperature management 5. Humidity control 6. Daily Insect and Disease Monitoring


Critical Control Point 1

Soil Texture and Soil Structure


Soil Texture

• Simply put – Size of the soil particles

– Defined from sand to clay.

– Some effect on nutrient exchange and growth

– Not gravel


Soil Texture

• Right amount of Sand and Clay • Soil particle size

– Heavy soils can lead to compaction – Heavy soils lead to soil water lodging

– Lighter soils cause difficult water management

– Lighter soils make fertility management harder to

management


Test the Sand

Test for Basics - pH - Other nutrients are ok but not as important


Soil Structure

• Soil structure is the way in which the individual particles—sand, silt, and clay—are arranged into larger distinct aggregates.

• Structure is the major factor determining how fast air and water enter and move through the soil.

• Structure is a major factor with root growth and plant nutrient uptake = yield/quality


Importance of Organic Matter

• Improves soil physical properties Drainage – Aeration – Easier to work

• Increases moisture holding capacity – Especially in sands

• Improves soil fertility – Source of nutrients – Increased ability of soil to hold and release nutrients

• Promotes soil microbes and earthworms • Reduces soil crusting


Soil Structure

• Improved by – Addition of organic matter – Managing compaction – Proper tillage – Deep tillage


Soil Structure

• The examination of the soil profile it 7 different high tunnels that have been planted for three years or more indicated a formation of a hardpan at 8-10 inches even under the bed. – Yield and or quality in these tunnels were

drastically being reduced.


Soil Structure

• Managing soil structure is a constant process. 1. Add sufficient organic matter annually 2. Monitor possibility of hardpan 3. Consider deep rooted cover crops 4. Use deep tillage 5. Use common sense



• High Tunnel Soil and Plant Nutrition


High Tunnel Soil/Plant Fertility

• Simply Put – How are you going to supply enough nutrients

to produce the yield and quality at a very high level.


Fertility

• Must be – Ample supply – Constant supply – Balanced – Supplied to the end of harvest


Soil Nutrient Research • Before planting soil was tested at

0-6 inches 6-12 inches 12-24 inches Soil was retested for each crop after season

production. All plots were fertilized equally


Soil Nutrient Research

Cobra Tomatoes 0-6 inch soil depth

N P K Before Season 335 330 1050 After Harvest 11 215 235



Water Management


Water Management

• High tunnels receive no external rainfall

– Drip tape system supplies all the water needs.

A few minor exceptions


Water Management

• Overwatering – Very critical with young plants

– Especially in cooler weather – Root rots – Slow growth – Reduced season long yield


Water management

• Soil Nutrients – Leaching – Unavailability


Water Management

• Why water is important – Keeps plant cells turgid – Helps control plant temperature – Uptake of nutrients – Keeps plant metabolism even – Completes pollination


Water Yield Data

• Cucumber plants without water going in peak production

No break in watering 32 pounds plant 24 hours with out water 28 pounds plant 48 hours with out water 23 pounds plant 72 hours with out water 16 pounds plant 96 hours with out water 3 pounds plant.


Drip Irrigation System Requires !!! Daily Management !!!

• Irrigation system – Application

Rate – Uniformity

• Plant needs – Rooting depth – Daily “ET”

• Soil water status


High Tunnel Vegetable Production System



Temperature Management


Temperature

The ability of high tunnels to capture solar

heat is the main reason for their success Your ability to monitor that solar heat is the

key to your success.


Growing Degree Comparison Inside and Outside Tunnel

• Inside Tunnel • March 281 GDU • April 435 GDU • May 502 GDU • June 570 GDU • July 624 GDU • Aug 544 GDU • Sept 570 GDU • Oct 303 GDU

• Outside Tunnel • March 5 GDU • April 99 GDU • May 183 GDU • June 366 GDU • July 505 GDU • Aug 374 GDU • Sept 396 GDU • Oct 101 GDU


Temperature • Inside the High Tunnel = 3500 GDU

• Outside tunnel = 1650 GDU

• Our greatest advantage can easily become our enemy if not monitored and controlled on a hourly basis


Temperature

• Temperature must be monitored and kept in the range for the crops being grown

• Warm season crops 80 – 90 degrees.


Low Production often due to high temperatures

• Temperatures greater than 95 F will lower

yields in many crops by causing pollen sterilization and or fruit abortion

Cucumbers setting flowers will see production decline 12-15 days later.

Tomatoes flowering during high temp will see fruit production decline 40-45 days later.


Temperature

• One of the basic rules of management is that - you can not control that which you

can not measure. - the more detailed that some thing can

be measures the closer in can be managed


Temperature

• Consider shade cloth

• Consider shade paint.



• Humidity and Ventilation


Ridge Vent


Humidity

High humidity can be a major problem with high tunnel production

Disease control Plant growth Working conditions Tunnel deterioration


Humidity

• There is no more explosive problem in a

high tunnel then high humidity to the extent of free water for over 12 hours, combined with high temperatures.


Plant Disease Triangle

Environment Environment

Presenter

Presentation Notes

Many growers are well aware of the need for a susceptible host and a pathogen, the environment is the aspect most comonly forgotten about Some pathogens are always with us, others are brought in on seed, plants, soil, wind and water Need to know what pathogen you are dealing with, host resistance is specific Available for many diseases


Humidity

To remove humidity quickly you must create

continual air flow not just open the roll up sides



• Daily Insect and Disease Management


SIX Critical Control Points

1. Soil texture and soil structure 2. Soil Fertility 3. Water management 4. Temperature management 5. Humidity control 6. Daily Insect and Disease Monitoring


Other Control Points

• Variety Selection • Row spacing • Plant density • Crop selection • Crop mix • Harvest efficiency


Questions

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