Agronomy III - Root Crops

Learn how to grow root vegetables, some of the world's most vital crops!

Add to what you are already growing on your farm or start a new enterprise with this comprehensive course in root crop growing.

Root crops include:

• potatoes
• sweet potatoes
• yams
• turnips
• carrots
• swedes

In developing countries, some types of root crops (for example yams and cassava) which are relatively high in protein (about 6%), contribute to the diet as a substitute for other, less obtainable, protein foods such as fish or meat; root crops are also becoming very popular in the developed world as people begin to understand the benefits to their health and to the environment by growing and eating root vegetables.

This course will help you discover different varieties of root vegetables, learn best growing practices and understand different harvesting techniques.

This is an experiential learning-based course. Throughout your studies you will have the opportunity to network with and learn from a variety of industry professionals. Establishing real-world relationships and confidence is key to career success. 

Lesson Structure

There are 10 lessons in this course:

1. Scope and Nature of Root Cropping and the Botany of Roots
   • What are root vegetables?
   • Human nutrition and root vegetables
   • Botany of roots
2. Cultural Practices A: Soil Management, Crop Scheduling and Soil Water
   • General guide to growing root vegetables
   • Improving soils
   • Sampling soils
   • Cover crops
   • Cultivation techniques
   • Soil fertility and plant growth
   • Plant nutrition
   • Fertiliser
   • Soil and water
3. Cultural Practices B: Weed control, Pest Management
   • Weed and weed management
   • Methods of weed control
   • Pest and disease management
   • Toxicity
   • Diseases
   • Common environmental problems
4. Potatoes
   • Growing conditions
   • Nutrient requirements
   • Planting
   • Care
   • Watering
   • Problems
   • Harvest and post-harvest
5. Carrots and their Relatives
   • Carrots
   • Parsnips
   • Bulb fennel
   • Turnip rooted chervil
   • Skirret
   • Celeriac
6. Turnips and their Relatives
   • Turnips
   • Rutabaga (swede)
   • Radish
   • Horseradish
   • Daikon
   • Kohlrabi
7. Beets
   • Growing conditions
   • Nutrient requirements
   • Planting
   • Care
   • Watering
   • Problems
   • Harvest and post-harvest
8. Taro, Yams and Sweet Potato
   • Growing conditions
   • Nutrient requirements
   • Planting
   • Care
   • Watering
   • Problems
   • Harvest and post-harvest
9. Other Root Crops
   • Salsify
   • Scoronera
   • Scolymus
   • Mashua
   • Jerusalem artichoke
   • Potato bean
   • Arrowroot
   • Oca
   • Dandelion
   • Chinese artichoke
   • Water chestnuts
   • Yacon or jicama
   • Root chicory
   • Ullico
   • American groundnut
10. Harvest and Post-Harvest Management
    • Harvesting root vegetables
    • Cooling methods
    • Storage

Each lesson culminates in an assignment which is submitted to the school, marked by the school's tutors and returned to you with any relevant suggestions, comments, and if necessary, extra reading.

Aims

• Describe root vegetables, their variations and nutritional value and the morphological internal and external structures of roots.
• Outline the cultural practices needed to produce vegetable crops.
• Outline methods of weed and pest management and the use and range of specialised machinery used in root crop production.
• Outline the cultural requirements and growing techniques for potatoes.
• Outline the cultural requirements and growing techniques for carrots and their relatives.
• Outline the cultural requirements and growing techniques for turnips and their relatives.
• Outline the cultural requirements and growing techniques for beets and their relatives.
• Outline the cultural requirements and growing techniques for Yams, Taro and Sweet Potato
• Outline the cultural requirements and growing techniques for a range of other root crops not studied earlier this course.
• Describe the harvest and post-harvest requirements of root vegetable crops.

What You Will Do

• Cultivate a root vegetable bed
• Create and update a log book recording your bed's details
• Conduct experiments to determine moisture range
• Discuss ways to improve soil for a set of root crops
• Discuss crop rotation systems
• Discuss seed treatments and planting techniques
• Prepare a weed collection
• Develop pest and disease control programs from planting through to harvest
• Write a crop production schedule
• Discuss timing of varieties and harvest

Botany of Roots

What are True Roots? 

To be classified as ‘true roots’, in botanical terms, roots must have the ability to:

• Secure the plant in the soil.

• Physically support the stems.

• Absorb water and nutrients and move them around in the plant through their conductive tissues (scientifically referred to as the xylem and phloem).

• Store nutrients.

The internal anatomy of a ‘true root’ consists of a central core (xylem) around which other tissue is arranged: the endodermis (the inner layer which forms a ring around the central vascular cylinder i.e. the xylem and phloem); the pericycle (the outer layer of cells that surround the vascular cylinder) and the epidermis (the outermost layer of cells that surrounds the root).

True roots also lack the types of buds from which leaves, flowers, cones and other plant structures develop.

True roots from other plants including as angelica, horseradish, sassafras, sarsaparilla and liquorice are used for the extraction of flavours or spices. The plant roots of many plants are also used to make herbal medicines - for example ginseng roots.

The Function of Roots 

The Soil provides the plant with the following things:

1. Nutrients

2. Water

3. Air

4. Support

Roots absorb nutrients, water and gasses, transmitting these ‘chemicals’ to feed other parts of the plant. Roots hold the plant in position and stop it from falling over or blowing away.

Plant nutrients can be supplied, broadly speaking, in three different forms:

1. Water soluble simple chemical compounds.  Nutrients in these compounds are readily available to plants (i.e. the plant can absorb them quickly and easily)

2. Less soluble simple chemical compounds.  The nutrients in these compounds can be used by plants without needing to undergo any chemical change, but because they don't dissolve so easily in water, they aren't as readily useable as the more soluble compounds. The diminished solubility may be because of the nature of the compound (e.g., superphosphate) or may be due to something else (e.g., slow-release fertilisers such Osmocote™, which is made by incorporating the simple chemicals inside a semi-permeable bubble - thus nutrients move slowly out of the bubble). This second group of nutrients when placed in soil will last longer than the first group of water-soluble nutrients.

3. Complex chemical compounds. These require chemical changes to occur before the nutrients can be absorbed by plants. They include organic manures and fertilisers which need to be broken down by soil micro-organisms into a form which the plant can use. They also include other complex fertilisers which need to be affected by natural acids in the soil, or heat from the sun, to become simple compounds which the plant roots can use. Complex chemicals release their nutrients gradually over a long period of time, depending on the range of chemical changes needed to take place before the plant can use them.  Plants grown in a soil derive their nutrients from all three types of compounds. The availability of these compounds varies according to not only the group they come from but also according to factors such as heat, water, soil acids and micro-organisms present. As such, it is impossible to control the availability of nutrients in soil to any great degree.

Root Structure

Looking at the internal structure of a root system reveals that it is very much like the structure of a stem. The older roots of trees and shrubs, like the stem, also have phloem, xylem and cambium layers. The phloem is the cork-like bark on the outside, the xylem is the wood inside, and the cambium is a layer in-between the two. The xylem transports water and minerals to the stem and the phloem transports the food manufactured in the plant to the roots for storage.

The growth zones of both the root and shoot are almost identical. The root cap situated on the end of the root initiates new growth through cell division in the meristematic zone at the tip - as does the growing tip of a shoot. As the new cells grow in size - the root increases in length; once the cells reach full size they differentiate to form the various parts of the root system. The constant productions of new cells (that rub off as the root passes through the soil) help to protect the root cap and newly developed roots. As the root ages side roots form that become increasingly larger.  

Minerals and water are absorbed from the soil into the root system through root hairs. Root hairs are projections from some of the epidermal cells and they substantially increase the surface area of the root.  Because of this, they also increase the plant’s ability to uptake minerals and water from the soil. These hairs are fine, easily damaged and occur on young actively growing roots. Some plants cannot survive without them. Root hairs are found just behind the growing region of the root cap (zone of elongation) in an area called the zone of differentiation. 

Who can Benefit from this Course?

• Farmers and farm workers
• Farm equipment and service suppliers
• Agriculture students and professionals
• Small farm or hobby farm owners considering new 'niche' crops
• Livestock owners/managers, wanting to produce animal feeds

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