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RHS Level 2CertificateWeek 5: Mulches and composting
Quiz on weeks 3 and 4 7 questions – 15 minutes Test conditions Better than 3 or 4 right and you are doing well at this stage.
Quiz answers1. (c)2. (a), (c) and (d)3. Benefit: prevents run off; levels soil; provides fine structure for seeds; incorporates dry fertilizers etc Limitation: Can lead to capping; does not improve structure overall; risk of wind erosion if over-raked.4. capillary5. (b), (c) and (d)
Quiz answers continued6.Sandy7.Anyfrom: garden compost; farm yardmanure; mushroom compost; leafmould.More than 3 or 4 right and you are doingwell. Less than that and you need toreview your notes.
Learning objectives 5.5 List FOUR bulky organic materials used as organic soil mulches, including chipped bark products, leaf mould, composted straw products, cocoa shell. 5.6 Compare the benefits and limitations of each of the materials listed in 5.5 for use as a mulch. 5.7 Describe FOUR methods of composting garden waste, including aerobic and anaerobic methods, production of leaf mould and the use of wormeries. 5.8 Describe the contribution made by earthworms, bacteria and fungi to the organic matter content of the soil. 5.9 State the importance of the ratio of ‘green’ to ‘woody’ material in the breakdown of organic matter, and the importance of lime to the composting process.
Advantages and limitations ofadding organic matter to thesoilAdvantages LimitationsImproves drainage and Needs to be regularlywater holding capacity applied in bulk – especially intensively cultivated soilsEncourages formation of Breaks down more‘crumb’ structure quickly in well aerated, well drained soilsDarkens soil so it warms Can acidify the soil as itmore quickly decomposesImproves CEC Likely to need to import material
Organic Mulches - benefits Applied to the soil to reduce weed growth and retain water. Can prevent soil capping on silty soils Retains warmth in the soil, producing a more steady temperature Can be used to protect more tender herbaceous perennials from frost. Can be decorative and protect plants from splashes of soil
Organic mulches -limitations Slow to break down so do not significantly increase soil organic matter on their own. Need to be thick to suppress weeds – 10cm at least. Can rob the soil of nitrogen whilst decomposing Must not touch the stems of woody plants or fungal diseases will enter.
Types of Organic Mulch -Bark Chipped bark – forestry by-product. Comes in a number of different grades Easily available and a good weed suppressant However it can rob the soil of nitrogen and can be easily blown about. Some risk of introduction of honey fungus in wood chip products.
Types of organic mulch –Leaf mould Essentially free if you make your own; recycles waste. A good soil improver if dug in before being replaced. Difficult to obtain in any quantity. Composted pine needles produce acidic leaf mould that is good for acid loving plants.
Types of organic mulch –composted straw Either produced in the garden or purchased as mineralised composted straw (‘Strulch’). If mineralised, long lasting and a good soil improver. However, expensive to buy. Home made will need storage space (takes up to two years); can rob the soil of nitrogen and can be messy.
Types of organic mulch –cocoa shell By-product of the chocolate industry so recycles waste. Benefits – long life; pleasant smell; easy to handle; Contains nitrogen so does not rob the soil; good weed suppressant. Limitations – toxic to dogs when fresh; shipped to the UK so not necessarily ‘green’. Forms a hard crust which may reduce water penetration.
Composting – garden compost Hot Heap method (aerobic composting)– careful balance of carbon and nitrogen and regular aeration. Benefits– kills weed seeds and (some) fungal spores; quick method (3-6 months). Limitation – need to store materials (browns and greens) to get the right mix; effort of turning; volume needed.
Composting – garden compost Cool Heap method (anaerobic composting)- less care with carbon – nitrogen balance, no turning. Benefits – less effort than a Hot Heap; requires less volume of material. Limitations – much slower than aerobic composting (at least a year); does not kill weed seeds or fungal spores; can produce smelly, slimy compost if too wet/too much nitrogen.
Composting – leaf mould Fallen autumn leaves are allowed to rot in either a chicken wire frame or punctured plastic bags. Benefits – produces an excellent soil conditioner. Limitations – hard to get enough leaves to make a significant amount; slow process (1- 2 years).
Composting - Wormeries A small scale method for composting kitchen scraps and some card or paper using brandling worms. Benefits – Wormeries can be used inside the house in the kitchen or garage etc. Produces a high nutrient compost and a liquid feed (must be diluted) Limitations – care needed to keep the conditions right (not too wet or too acidic); regular care and inspection required. Small scale only for domestic use.
Learning outcomes 5.5 List FOUR bulky organic materials used as organic soil mulches, including chipped bark products, leaf mould, composted straw products, cocoa shell. 5.6 Compare the benefits and limitations of each of the materials listed in 5.5 for use as a mulch. 5.7 Describe FOUR methods of composting garden waste, including aerobic and anaerobic methods, production of leaf mould and the use of wormeries. 5.8 Describe the contribution made by earthworms, bacteria and fungi to the organic matter content of the soil. 5.9 State the importance of the ratio of ‘green’ to ‘woody’ material in the breakdown of organic matter, and the importance of lime to the composting process.