PRACTICAL HORTICULTURE 2

Course CodeBHT323
Fee CodeS3
Duration (approx)100 hours
QualificationStatement of Attainment

Expand your Practical Skills in Horticulture

Work planning and project management is an important aspect of the type of work that would be generally carried out by the professional horticulturist. It may be in diverse areas within the horticulture industry i.e. a planting program, plant sales program, landscape project, re-vegetation project, sports or turf management, irrigation and drainage systems implementation, production planning (crops and nursery), conservation of natural resource areas, conserve a heritage area and so on. Project management may be under the broad direction of superiors in certain situations however self directed application of knowledge that has substantial depth is expected at this level.

Lesson Structure

  1. Materials and Equipment
  2. Horticultural Calculations
  3. Practical Risk Management
  4. Machinery and Equipment Assessment and Maintenance
  5. Propagation Management
  6. Hard Landscape Maintenance
  7. Soft Landscape Maintenance
  8. Practical Plant Identification Techniques
  9. Pest, Disease and Weed Control
  10. Identifying plant tissues
  11. Planning -identifying needs for management of horticultural sites.

Aims

  • Identify a range of horticultural materials and equipment and sundries
  • Specify assessments necessary to perform horticultural operations, and carry out calculations for these assessments
  • Assess horticultural situations for risks and hazards, and demonstrate methods and procedures to minimise risk
  • Assess the state of repair of a powered implement and carry out routine maintenance or calibration.
  • Organise the propagation of a range of plants
  • Carry out routine maintenance on a variety of hard landscape features.
  • Demonstrate and determine the routine maintenance and future management for production and amenity situations of a variety of soft landscape features.
  • Identify a range of seeds and plants
  • Identify a range of weeds, plant pests, diseases and disorders, and state methods of their prevention and control.
  • Identify plant tissues and state their functions
  • Carry out a planning exercise to determine future management of a given area of plants, and all hard or soft landscape features

TIPS FOR IMPROVING SOILS from our Horticulture Experts

The type or proportions of soil components can often be readily adjusted, particularly on a small scale (e.g. in a home garden), to improve the soil.  This usually involves adding something to the soil. The following are common ways of improving soils using natural materials:

Add Organic Matter
Most soils will benefit from the addition of organic matter, except those that are already high in organic matter such as peaty soils. Soils with good levels of organic matter are generally easily worked (we say they have a good tilth if they are easily worked). If you squeeze a handful of soil into a ball in your hand and it remains in a hard lump, then it has a poor tilth - hard clods will result when it is ploughed. If it crumbles, then it is well granulated; organic matter promotes granulation. Cultivated soils with good tilth are less subject to wind and water erosion.

Organic matter will improve the soil by:

  • Helping to improve soil structure; this will also improve water penetration and drainage, as well as improving aeration. Adding organic matter is particularly valuable for poorly structured clay soils.
  • Adding valuable nutrients to the soil.
  • Helping to retain moisture in well drained soils e.g. sandy ones.
  • Acting as a buffer against sudden temperature or chemical changes which may affect plant growth.
  • Encouraging the activity of beneficial soil organisms e.g. earthworms

It is difficult to increase the percentage of organic matter in a soil - but it is important to try to maintain that percentage. The average mineral soil contains around 2 to 5% organic matter. Organic content will drop if you remove plants from a soil and don't return organic material to the soil. Organic matter can be added in the following ways:

  • The roots of plants should be cultivated back into the soil when the plant has finished growing.
  • Compost should be added regularly.
  • Organic mulches should be regularly applied to the surface of the soil.
  • Feeding plants with manure (preferably well-decomposed), and other organic fertilisers.

Problems with Organic Materials

Soils containing high levels of materials such as peat, bark and sawdust may become hydrophobic and these soils can be very hard to re wet if they are allowed to dry out. Organic materials can coat soil particles with a greasy layer (particularly in sandy soils) this inhibits water absorption and in severe cases water droplets don’t infiltrate but sit on the soil surface. To improve this with this problem you can do several things but firstly you will need to remove the greasy layer on the soil peds - this can be done with a soil wetting agent. However many wetting agents are petroleum or chemically based so unsuitable for an organic garden. There are a few certified wetting agents that are approved for use in organic gardens and farms but you could try making your own by using agar agar (which is actually align - a food grade thickener that derives from seaweed). 

An Organic Wetting Agent
To boiling water slowly add the agar agar until it forms a thick paste (like wall paper paste)
Slowly add boiling water to agar agar and stir to make a paste about the same consistency Then use 4.5l of water to dilute 250ml of the paste and spray or water onto the affected areas. You may need to repeat this process until the soil is moist.

Once you have moistened the soil keep it moist and also healthy by adding well-decomposed compost and lots of mulch. Make sure that the soil never dries out fully, if possible.

Increasing the clay content in sandy soils so the soil becomes sandy loam or loam is a good long term cure.

Phytotoxicity
Phytotoxicity is where `poisonous' parts of organic matter cause harm or even death to living plants.  Phytotoxins can come from residue decomposing microorganisms, fresh plant residues dug into the soil, and even from the plants themselves. The older the plant is when it is incorporated into the soil, the more likely it is to be toxic, so avoid planting in that area for a while. Young green crops generally have only a low level of toxicity when incorporated into soil. These problems can be avoided to a degree if the residues are not dug in, but left on the surface as a mulch, or composted.

  • Common phytotoxicity problems can also occur with mulches of fresh shredded or chipped pine-bark or eucalyptus. These materials should be composted for 6 8 weeks before being used.   
  • Carbon dioxide releases - decomposing fresh material releases carbon dioxide which can damage roots; don't put anything too fresh on plants
  • Ammonia release - fresh organic matter, particularly animal wastes, will often release levels of ammonia gas that can cause burning to plant roots and foliage. Such wastes should be composted for a few weeks prior to being used, or used only in small amounts at a time.

Low Organic Content in Warm humid Climates
In warm, wet climates, organic content of the soil can be low (under 0.5%), because organic material breaks down faster in these areas. This is particularly a problem in sandy soils.
In these areas, add 4% compost (or organic material) or higher to a bed when you prepare it, and top up annually with the same amount.

Adding Non-Organic Materials
Light sandy soils can often be improved by the addition of finer particle material such as clay and silt. This will help improve moisture and nutrient retention. The addition of coarse material (such as sand) to a heavy clay soils can help improve drainage and water penetration. Generally fairly high amounts need to be added to be effective. Any added material should be thoroughly mixed in. Be careful also to avoid adding material that may be contaminated in some way (e.g. with lots of weed seeds, pollutants, pests or diseases, or salts).

Add Lime
This is the main way to raise the soil pH if it is too acid. Soils can be naturally acid, or may become too acidic when fertilisers such as sulphate of ammonia have been extensively used, or where excessive manures or mulches are applied. Lime might also be used if you are growing lime loving plants such as cabbage, cauliflower and broccoli.

The main liming materials are: 

  • Crushed limestone (calcium carbonate) - the most commonly used and least expensive form of lime.
  • Dolomite   a mixture of calcium and magnesium carbonates is commonly used, especially in pine bark based potting mixes.
  • Quicklime   calcium oxide and builder’s lime, also known as 'Limil' - more concentrated and expensive than limestone or dolomite, and can be easily over used raising the pH to a much higher level than desired. If a quick result is needed for small areas, then builders lime is quite useful.

The amount of lime to be applied will depend on a number of factors:

  • How acid the soil is.
  • The buffering capacity of the soil - or how resistant it is to a change of pH.
  • How acid the subsoil is.
  • The quality or purity of the liming material to be used (i.e. how much calcium carbonate it contains).
  • How often the lime is to be applied
  • What you want to grow (each plant having its own preferred pH range).

Anything from 80 to 800 gm of calcium carbonate is needed to raise the pH in 1 sq metre in the top 10cm of soils, in different soil texture types ad starting from different pH's.

The percentage of Calcium carbonate in the liming material used will generally stated on the packaging or for large lots provided by the supplier.

 
Add Acidic Materials to lower soil pH
Sometimes it is necessary to lower the soil pH to provide the ideal growing conditions for plants or an area that is going to be planted. To try and alter soils with a higher pH than 7.5 can become quite expensive, and it is often best to simply grow plants that suit the alkaline conditions, or to slightly reduce the pH, rather than to try for major reductions in pH. This can be achieved by:

  • The addition of sulphur - sulphur is oxidised into sulphuric acid by soil microorganisms. This acid reacts with calcium carbonate in the soil to form gypsum, which has a pH close to neutral. The conversion of the alkaline calcium carbonate to gypsum therefore reduces soil pH. For soils that are neutral to slightly alkaline use from 25 grams for sands, to 100 grams for clays of sulphur per m2 to lower the pH in the top 10cm of soil to around pH 6.0-6.5. To achieve greater reductions would necessitate quite extensive applications of sulphur, which could be very expensive. For quickest results mix the sulphur into the soil rather than spreading it on the soil surface.
  • Adding material such as peat which has considerable acidifying abilities - one cubic metre of peat has an equivalent acidifying effect to about 320-640 grams of sulphur. To lower the pH one point in the top 10cm of soil, one cubic metre of peat, incorporated into the soil will be effective over an area of about 3.25 m2 for clay soils ranging up to about 13 m2 for sandy soils. However there are environmental issues with the use of peat as it not a renewable resource and peat bogs are environmentally complex and vulnerable areas, (peat mining is being banned in some countries).
  • Ferrous sulphate can be used at a rate of around 50-150gm per m2. Diluted solutions of Iron sulphate or phosphoric acid can also be used.          

Adding Gypsum
Gypsum is applied to hard packed or poorly structured clay soils. It has the ability to cause clay particles to aggregate together in small crumbs (or peds), thereby improving structure.
Gypsum contains around 23-25% Calcium and about 15% sulphur. It will not affect soil pH to any great extent. Gypsum however is only useful on sodic clay soils. The use of gypsum on non-sodic clays can permanently compromise its structural qualities. Test for sodicity before application.

NOTE: The previous three treatments require moist soil conditions over several months to have a noticeable effect. It is important not to expect immediate results.


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