When we go in search of fertilizer, every bag we see will have some numbers on it. These refer to the N-P-K ratio for that fertilizer. They are the chemical symbols for nitrogen (N), phosphorus (P), and potassium (K), three of the macro-nutrients that plants need. There are a large number of other chemical elements that plants need such as calcium, magnesium and sulphur. A balanced fertilizer will be 6-8-6, 10-10-10 or 4-4-4. If it is an organic sourced fertilizer then it will also contain essential micronutrients. You will see these numbers on both chemical and organic fertilizers. Which fertiliser you use really depends on what you are growing. A general balanced organic fertilizer (example Gaia All Purpose) can be used for everything but if you want to get more selective as to the fertilizer you use for each specific crop, then you may want to consider what each of these elements does for the plant. Nitrogen is necessary for the production of any protein. It is particularly important for production of green crops such as lettuce, spinach, etc. Lack of protein will result in stunted growth and yellowing of older leaves. The nitrogen source in the fertilizer will be utilized by soil micro-organisms which will release nitrate ions for plant uptake. Phosphorus is essential for photosynthesis whereby plants use carbon dioxide from the air, water, chlorophyll (green pigment in leaves) and sunlight to produce sugars and oxygen which is released into the atmosphere. All oxygen you breathe has come originally from this chemical process. It is also necessary for the development of flowers and fruits as is potassium. Potassium promotes strong stems and roots, helps in maintaining the correct water balance and helps plants resist disease. It can be easily leached out of the soil by over watering. The old gardeners used to tell us that we needed to grow our plants ‘hard’. This means we need to avoid over fertilising which will result in soft growth which is pale green, lanky and susceptible to disease. If all this is beginning to look very complicated, just remember that a general organic fertilizer will do the job. If you have added some seaweed and manure, you basically have all bases covered. Carrots will do better with less nitrogen and more phosphorus but they do OK with a general fertilizer. I have found that what works for me is the following formula: 4 parts alfalfa meal, 4 parts fish meal, 1 part dolomite lime, 1 part rock phosphate and 1 part kelp meal. Occasionally I will add some greensand ( 0-0-3) especially after a very wet winter. I also add chicken manure (higher in nitrogen than other manures) to feed the soil microorganisms and I mulch with hay which also breaks down to feed the soil. As we all need to lime the soil at this time of year, add your dolomite lime about 3 weeks before you start working the soil and adding your organic fertilizers. I add mine just before planting and work it in to the top few inches of the soil.