Supplementary organic nutrition Whatever your particular interest, a plot full of healthy plants must be a prime objective. That doesn’t necessarily mean bigger more perfect vegetables and ornamentals. But healthy plants radiate health, we can sense it. So how do we help achieve this state? Build up your soil, prepare your beds so that nutrients can be easily absorbed, and feed the plants if necessary. Feeding the soil has several benefits. The microorganisms (the bacteria, fungi, viruses etc) and other soil beasties are fed. They break down compost and reconstitute the composts’ chemicals into a form that the plants can take up. The beasties form an incredibly complex web of interactions within the soil. Some are also a source of food for birds, hedgehogs, voles, and other small animals.Feeding the plants may have a direct benefit. Many commercial growers depend on bagged fertilizers (NPK) encouraged by manufacturers and agribusiness. There is no doubt these produce results in terms of crop yield. But there is plenty of evidence to suggest that only using NPK is bad news for the microorganisms of the soil. The chemical salts in the artificial fertilizers can also scorch young plants when added at the wrong time. And the strong interaction between microorganisms and plants can be badly affected. Commercial agribusiness creates NPK using fossil fuels. The type of nitrogen it provides isn’t always in the best form for maximum benefit. Fortunately other fertilizers are available. NPK is shorthand for nitrogen, phosphorous, and potassium. These are called macronutrients, the nutrients plants need in large amounts. Plants also need calcium, magnesium and sulphur in smaller amounts. There are lots of micronutrients, also called trace elements. These are needed in tiny amounts, but they are still crucial to a balanced diet (both for plants and humans). Good compost supplies these trace elements and to some degree the macronutrients. It provides a balance of nutrients and organic matter. Some soils will have been cropped year on year and if there have been few inputs the soil will be “exhausted.” This term refers to a collapse in the soil structure, leading to compacted soil which may become waterlogged. These soils will have nutrient deficiencies. There are various reasons nutrients can become unavailable. Soil structure is one reason and locked up nutrients is another. Sandy soils drain well and so tend to leach nutrients quickly unless compost is added regularly. Clay soils are much more retentive but can get compacted; compost helps increase air flow at the root level. Loams have a balance between the two.Plants take up most nutrients through their roots. These soil-based nutrients are dissolved in the soil water. The soil water is held in the pores. A soil with organic matter has a good system of pores, and roots extend easily and access the nutrient-filled water within the pores. Gardeners aim to provide a balanced soil environment with a good pore structure so strong roots can grow and absorb these nutrients. We dig or fork soil to loosen it in to help the roots to develop and access the organic matter. Raised beds can also assist drainage on heavy soils. Nutrients cling chemically and physically to the decomposing organic matter of compost. They will dissolve in the soil water slowly and be sucked up by plant roots as needed. Slow release is good because nitrogen doesn’t get wasted (it’s expensive!) by being washed away (leached). If nutrients are leached, they can also become a source of water pollution. Leaching happens especially when artificial fertilizers, which dissolve quickly, are added in greater amounts than the plants can absorb them. Slower uptake can be due to cold weather, to overly-wet soils, or to soil acidity. Locked up nutrients is also a cause of nutrient deficiencies in plants. Some chemicals are locked up when the soil is too acid or alkaline. The acidity of the soil can cause problems because it changes the chemical forms of nutrients. The chemical form changes to one that the plants can’t easily absorb. The scale of soil acidity is called the “soil pH” and runs from 1 – 14. Below 7 is acid, above is alkaline. A level of 5.5 to 7 is best for most plants, though some thrive at other levels. Garden lime raises the pH of acid soil. A soil test kit helps you know how acid/alkaline your soil is. This measure can differ in various areas of the garden, so the pH near conifers may be very different from that of beds next to the house.In very wet areas, soils become increasingly acid because of leaching. Occasional checks are good to see if your soil shows excessive acidity. Always use garden lime, as builders’ lime can scorch your plants. Adding lime changes the chemical form of the nutrients, which means plants can absorb these nutrients more easily. But some plants, like rhododendrons and heathers, take up lime too easily and are damaged. They are said to be lime-haters. Lime takes time to break down, so if you are about to sow or plant, apply the lime to your compost rather than to the soil. Add a good sprinkling once you have generously covered the last layer in the compost heap. If you use it directly on the garden, use several lighter doses of lime rather than one heavy one. And leave some days or (ideally) a few weeks before sowing/planting. Never apply lime at the same time as artificial fertilizers. There are organic options which are better suited to both soil health and plant health. You can readily buy these. Below are listed some that we currently use, but others are available. Nitrogen is the foundation of proteins and commonly in short supply. Gardens where heavy nitrogen users like brassicas (cabbages and family) and green leafy veg are grown are particularly needful. It helps to have peas and beans in the rotation. Peas and beans are legumes, like clover. They can all take nitrogen from the air, whereas most plants depend on soil nitrogen. The legumes leave some nitrogen behind in the soil for the next crop. So including legumes in your crop rotation is important. One fertilizer contains three elements: fish, blood, and bone. These elements release/dissolve nitrogen at different speeds. This means an ongoing and more gradual supply, benefiting plants over a longer period. So, add it at the start of the growing season so that the quick-released nitrogen isn’t leached before it can be taken up. Bone meal is high in slowly released nitrogen. Apply it in late winter when the soil is damp.We are big believers in using seaweed in various forms. We use a liquid form, and water it or spray it on as recommended. It supplies the micronutrients. It is also available in powdered form. When applying chemicals of any kind, whether organic or inorganic, whether they fertilize, deter pests, kill insects or fungi, be careful not to exceed the recommended dose. Too much can scorch or kill plants and non-target organisms, damage micro-organisms and pollute the soil or nearby water courses. Don’t be tempted when measuring out to ‘add one for Granny’. She would tell you off in no uncertain terms. She is fierce for a good reason. Granny always follows the directions and wears her PPE as required. And she never tries to push her young plants on too fast, as she knows it will make their transition to outdoor growing harder. Next, to keep her happy, we’ll get down to some hands-on gardening and talk about that transition.