Having the right balance of plant nutrients is essential to the production of vegetables and flowers.There are several main nutrients. Carbon is provided through CO2 and water goes with it as the two interact with sunlight to drive photosynthesis. But there are three big ones: nitrogen, potassium and phosphorus, known as NPK. When you see the NPK rating on the side of a fertilizer packetyou know the relative amounts of these three essentials. Nitrogen is vital for green growth and deficiency results in reddish leaves. Potassium is good for fruit and phosphorus for roots and general plant health. An excess of nitrogen produces abundance of green growth, but deficiency of fruit, as the excessive foliage places demands on the plant's resources. For this reason you should not allow excessively lush growth on tomato plants, as this may be at the expense of the fruit.
But there are other less important nutrients.Magnesium and manganese are important for leaf growth, and their deficiency produces yellowing between leaf veins and in the case of manganese patches of dead tissue. This sort of deficiency is common on sandy soil, which can also be a cause of calcium deficiency, which often is recognized by black or brown spots.Bitter pit is seen on fruits, and some plants, notably Bramleys, are susceptible. Iron deficiency is found most commonly on limestone soils. Its symptoms are bleaching or yellowing.
Some minor nutrients are born, copper and molybdenum. Molybdenum is rarely deficient in British soils, but it is seen mainly in cauliflower and broccoli, where the leaf blade can either die or shrivel to a thin whiptail. The remedy is to lime the soil. Boron deficiency is similar to calcium deficiency, but is commonest on soils derived from granite parent rocks. Copper deficiency occurs on a range of soils and is hard to identify .
Prevention is better than cure. Applying a rich variety of soil enhancers will help. Seaweed, be it raw, seaweed meal or liquid, is a rich source of nutrients. Rock dust helps, especially if it is derived from a variety of rock types to ensure that there is as wide a nutrient range as possible. Compost and manure always help.
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