Improving Your Soil
From: DK Books - Herbs
Once you have explored the quality of your soil, you may need to improve it. The soil in your garden or community plot is your most valuable resource, but without feeding, the quality of your harvests will deteriorate.
Add Organic Matter to Improve Soil Structure
Organic matter is a vital part of your soil’s structure, providing food and nutrients for the essential microorganisms and your crops. Each season that passes and each leaf removed further depletes the soil’s resources and ability to produce healthy crops. Moisture is retained in the minute cavities between soil particles, and organic matter improves the water retention for when the plant really needs it. Digging in well-rotted farmyard manure or homemade compost will work wonders for the leafier herbs, but do not apply in bulk to your Mediterranean herb bed as plants such as rosemary and lavender really dislike a moist and nutrient-rich environment.
Double Dig to Remove a Compact Layer
Double digging is hard work and should not be undertaken lightly, but its effects can last for several years. Mark out the area to be dug (don’t be too ambitious) and dig a trench one shovel’s depth and two or three wide, carrying the spoil to the far end of the area to be dug in a wheelbarrow. Using a fork, break up the base of the trench to 4–6 in (10–15 cm) and incorporate plenty of sand and organic matter. Dig over a further two or three shovels' widths of fresh topsoil and place on top of the freshly improved lower level, adding more organic matter and sand. Soil from the first trench will fill the last one and any surplus can be scattered over the entire area.
Add Coarse Sand to Improve Drainage
If you have soggy or clay soil, adding coarse sand will increase the drainage by decreasing the moisture-holding capacity of your soil. This will dramatically improve the range of herbs that you can grow. Incorporate the sand to a shovel’s depth and in large quantities. Experiment on a small scale, starting with a depth of 3 1/4 in (8 cm) over 3 sq ft (1 sq m) before committing to the entire site. Gravel is not expensive, but is very heavy, so calculate how much you need and remember it is easy to add more at a later date. A coarse sand of about 1/2 in (10 mm) diameter is ideal, but ensure only clean horticultural sand is used as saline contamination can be difficult to remedy.
Making Your Own Compost
Everything your garden produces as crop residues, spoiled vegetables, weeds, and prunings can, in theory, be composted and reincorporated into your soil forming part of a virtuous circle of cultivation, production, and recycling.
Choose ready built or made-to-measure composters and ideally they should be big enough to hold all garden waste for at least a year. Space for a composter in a small herb garden can be difficult to find, but if there is only room for a small 3 ft (1 m) square container, it can produce usable compost if fed with the right materials and treated correctly.
Woody and Excess Material
Woody material takes longer to break down, as does dry bracken or straw, but both are valuable additions to the compost bin, helping to aerate the heap. Cut woody stems into pieces the size of a finger and mix in well. Chop up surpluses of any one type of material and store in punctured garbage bags until it can be added in proportion.
Diseased plants and roots of perennial weeds should not be added as they are likely to reinfect plants or regenerate in subsequent seasons.
Filling Your Composter
Any organic matter can be added and it will rot if kept moist, so cover the heap with old carpet. Avoid cooked or processed food waste, which will rot quickly but is likely to attract rats and other pests.
In addition, layer green leaves, grass cuttings, vegetable remnants, woody chips, and straw in roughly equal quantities, ensuring that no single component dominates. In smaller composters, add a compost activator.