Organic Crop Production - University of Tennessee

1. Organic Crop Production:
Well‐thought‐out crop rotation is
worth 75% of everything else that
Crop Rotation might be done, including
fertilization, tillage and pest
control.
‐Firmin Bear
Annette Wszelaki
Vegetable Specialist
Why rotate?
What is crop rotation? Maintains good soil health and quality
Fosters the most effective use of soil fertility
Crop rotation is selecting a sequence Helps control weeds, some diseases and insects
of crops for a field that improves soil Reduces need for off‐farm inputs
quality while it sustains the farmer. Enhances moisture management
Promotes income diversity and stability
Improves crop quality and yields
Reduces soil erosion
Increases biodiversity
Improves water quality
Reduces drought impact
Decisions, decisions… Why bother?
With a 3 crop, 4
A good rotational sequence can accentuate
year rotation, there
every possible advantage
are 6 possible
sequences Different crops use soil nutrients differently
With a 3 crop, 8 All may alter or be altered by the succeeding or
year rotation, there preceding crop
are 5,040 Time spent planning a rotation is never wasted!
sequences! THINK IT THROUGH!

2. Rotation Lengths to Reduce Soilborne Pathogens
Insect, Disease and Weed Control Vegetable Disease Yrs w/o Susceptible Crop
Asparagus Fusarium rot 8
Monoculture encourages pest problems Cabbage Clubroot 7
A good rotation can prevent the build‐up of Cabbage Blackleg 3‐4
Cabbage Black rot 2‐3
specific pests and weeds
Muskmelon Fusarium wilt 5
Parsnip Root canker 2
Peas Root rots 3‐4
Peas Fusarium wilt 5
Pumpkin Black rot 2
Radish Clubroot 7
Source: S.A. Johnson & P.J. Nitzche, USDA
Plant Nutrition Soil Structure
Rotations can make nutrients more available Rotations preserve and improve soil structure
Plants of a lower order of evolution better Maximize benefits of crops with different
feeders on less soluble sources of nutrients rooting depths
i.e., alfalfa, clovers and cabbage versus lettuce and
cucumbers
Yields Things to consider:
Some crops helped, others hindered by preceding crop
How they help: How they hinder: Number of blocks or sections
Increase soil N Deplete soil nutrients Rotation works best if sections are all the same size
Improve soil condition Excrete toxic substances Number of years in rotation cycle
Increase microbial activity Increase soil acidity 10 sections does not necessarily = 10 year rotation
Excrete beneficial Make soil condition Do what makes sense for your operation!
substances unfavorable
Number of crops in rotation
Control pests Lack of proper aeration
Most small growers have many diversified crops
Remove moisture
Crops must be further divided based on botanical
Vector disease classification, plant part consumed or space utilized

3. Crop Families Crop Families
Brassicaceae (Cabbage Family) Fabaceae (Bean Family)
Cabbages, cauliflowers, kale, broccoli, turnips, Snapbeans, lima beans, broad beans, half‐
radishes, mustard, Brussels sprouts runners, field peas, English peas
Can have allelopathic effect on subsequent crops Fix nitrogen from the air for their own fertilizer
Solanaceae (Tomato Family) and for subsequent crop
Tomatoes, potatoes, peppers, eggplant (okra) Alliaceae (Onion Family)
Need fairly high level of nitrogen Onions, leeks, shallots, garlic
Potato prefers soil slightly more acidic Monocot
Crop Families Crop Families
Cucurbitaceae (Squash Family) Chenipodiaceae (Chard Family)
Squash, cucumber, melons, pumpkins, gourds Beet, spinach, Swiss chard, lambsquarters
Long growing season Mycorrhizae will not associate
Apiaceae (Carrot Family) Asteraceae (Lettuce Family)
Carrots, parsnips, parsley, celery, celeriac, dill Lettuce, salsify, Jerusalem artichoke
Dill enhances cabbage family, onion and lettuce Poaceae (Grass Family)
Corn
Crop Space Requirements Nutrient Feeding
Some crops are heavy feeders that deplete soils,
More Space Less Space
6 5 4 3 2 1
while other crops are light feeders that build soils.
Corn Potato Tomato Lettuce Onion
Pea Cauliflower Pepper Beet Soil Depleting Crops
Winter Broccoli Carrot Chard Row crops‐ corn, soybeans, vegetables, potatoes
squash Summer Parsley
squash Celery Soil Neutral or Soil Conserving Crops
Bean Parsnip
Cabbage Rutabaga Cereal crops‐ wheat, barley, oats
Spinach Kale
Radish
Soil Building Crops
Brussels Legume sods‐ alfalfa, clover
sprouts
Cucumber Grass sods‐ prairie grass, meadows, pastures

4. Year 1 Year 2
Year 3
Coleman’s 8‐year Vegetable Crop Rotation
Cover Crop/Green
Manures Used
Coleman’s 8‐year Vegetable Crop Rotation Coleman’s 8‐year Vegetable Crop Rotation
Potatoes follow sweet corn because research has Sweet corn follows the cabbage family because, in
shown corn to be one of the preceding crops that contrast to other crops, corn shows no yield decline
most benefit the yield of potatoes. when following brassicas.
Also, the cabbage family can be undersown to a
leguminous green manure, which, when turned
under the following spring, provides the most ideal
growing conditions for sweet corn.

5. Coleman’s 8‐year Vegetable Crop Rotation Coleman’s 8‐year Vegetable Crop Rotation
Peas follow tomatoes because they need an early
seedbed, and tomatoes can be undersown to a non‐
The cabbage family follows peas because the pea winter‐hardy green manure crop that provides soil
crop is finished and the ground is cleared (early) protection over winter with no decomposition and
allowing a vigorous green manure crop to be regrowth problems in the spring.
established.
Coleman’s 8‐year Vegetable Crop Rotation Coleman’s 8‐year Vegetable Crop Rotation
Beans follow root crops because they are not known
to be subject to the detrimental effect of certain root
Tomatoes follow beans because this places them 4 crops, such as carrots and beets, may exert in the
years away from their close cousin, the potato. following year.
Coleman’s 8‐year Vegetable Crop Rotation Ogden’s 4‐year Rotation Cycle
leaf crops fruit crops
Squash is grown after potatoes in order to have
two “cleaning” crops back to back prior to the
root crops, thus reducing weed problems in the
root crops.
legumes root crops

6. Don’t forget cover crops or green
Companion Planting
manures in your rotation!
Investment in weed and pest control Mix it up!
Vegetable systems have many windows to
include cover crops or green manures All of one crop or crop family does not have to
Example: Between harvest of early planted spring
go in the same block!
crop and planting of fall crops Three Sisters
Buckwheat, cowpeas, sorghum‐sudan
Herb‐Vegetable Combinations
Plant winter annual on fields that would lie fallow
Many veg crops can be overseeded with cover
Select crops that can tolerate shade and traffic
UT Organic Crops Field Tour
Future Workshops
Planting: Seed Sources & Transplants (May 11)
Identifying and Managing Weeds (June 8)
Identifying and Managing Pests (July 13)
High Tunnel Production (August 10)
Identifying and Managing Diseases (September 14)
•May 15, 8 AM – 11:15 AM
Developing an Organic System Plan (October 12)
•Pre‐register with ETREC by calling 865.974.7201
•Visit http://organics.tennessee.edu for more info Marketing Organic (November 9)
Questions?
Annette Wszelaki
annettew@utk.edu
(865) 974‐8332
http://organics.tennessee.edu
Organic Crops Field Tour: May 15