pH pH is the scientific measurement of acidity or alkalinity. The pH of your soil has some profound effects on your plants health by affecting the availability of plant nutrients by more than one mechanism. Soils across the world vary vastly in their pH. Some plants like blueberries and Rhododendrons have evolved to be best suited to an acid soil. Chalk heathlands are alkaline and the impoverished soil grows an abundance of chalk loving Flowers which support many butterflies and insects. Our vegetables and fruit that we grow have adapted to grow well at a specific pH range. Water without carbon dioxide dissolved in it has a neutral pH. It is neither acidic or alkaline. Its pH is 7. Acids have a pH below 7. They are acid because they can release hydrogen ions which make them so active. pH is a measure of the amount of hydrogen ions present. Due to mathematical manipulation the more hydrogen ions present the more acidic things become but the pH value gets smaller! pH values above 7 are alkaline due to the presence of chemical bases. The more base the more alkaline something is and the pH increases. When a base (which will be alkaline) is mixed with an acid they both react and tend to neutralise each other so that the pH moves closer to 7. Soil at Halls farm tends to be acidic and we use lime to raise the pH to a value more suitable for vegetables to grow. Overdo the lime and plants may not grow so well. So what is happening? Firstly there are essential elements in the soil that the plants need for healthy growth. Some of the elements dissolve in ground water much better if the soil is acidic whilst other elements dissolve much better if the soil is alkaline. The plant can only uptake these elements if they are dissolved in water. This means that if the pH is wrong for your plants needs it can be deficient of some nutrients even when there is lots of the nutrients present! All because the pH value makes most of the nutrient insoluble and not available. The reason why you get yellow leaves on blue berries if the soil is alkaline, is because most of the iron is bound to the soil and not available to the acid loving blueberry. As soil becomes more acidic nitrogen, phospherous, potassium, sulpher, calcium, manganese, molybdenum become less available compared to a soil with a neutral pH. As soil becomes more alkaline phosphorous becomes more available but nitrogen, iron and manganese become less available. Copper, Zinc and Boron are a bit more complex in their availability but are most available around a neutral pH. The pH also affects bacteria in the soil. Some bacteria like acidic conditions, some neutral and some alkaline conditions. If the acidity is not favourable then there will be fewer soil bacteria in the soil capturing nitrogen from the air, breaking down organic matter releasing nutrients or releasing nutrients from rock in the soil. Another role of bacteria is to inhibit some plant pathogens. The range of pH values which favour the most diverse types of bacteria is 6.7 to 7.5. In a previous email I mentioned the cation exchange capacity a measurement of the total capacity of certain nutrients like potassium, calcium etc to be stored on organic matter in the soil. When plants use some of these nutrients they swap the nutrient that was bound to the organic matter for a hydrogen ion. This makes the soil more acidic and as the hydrogen ion is occupying the site which held the nutrient the cation exchange capacity decreases. So making the soil more acidic reduces the soils capacity to store certain nutrients like potassium, calcium, magnesium. As stated before the pH scale is a measure of the acidity or alkalinity of the soil. A pH of 7 being neutral. Most of your vegetables are happy with a pH near this value. The scale is a logarithmic scale, pH is defined as the negative log (base 10) of the hydrogen ion concentration. This means that a pH of 6 has 10 times as much hydrogen ions as present when the pH is 7 because it's a log scale not a linear scale. A pH of 5 has 10 times as much hydrogen ions again as present at pH 6. So a pH of 5 has 10 times 10 as many hydrogen ions present as present at pH of 7 I.e 100 times as much. A pH of 1 has a million times as much hydrogen ions as present at pH 7. Which explains why when I opened a bottle of fuming sulphuric acid in a room rather than a fume cupboard it felt like it was going to burn a hole in my nose and lungs. I did not make the same mistake a second time!
At this time of year we are all busy watering and harvesting. The harvesting marks the end of a season for a plant. After harvest you have bare soil, not working for you. Hopefully some of you have planned a second crop to be harvested sometime between autumn and spring. Planting out potted vegetable plants last month or about now that you have grown from seed pays dividends. The head start in pots allow you to get a few weeks head start to early spring sowing and mid summer sowings to give you time for two crops. This year I have started my second and third crops. I grew calabrese with lettuce together to get two crops at once. There are peas and carrots growing in their place at the moment. One row of the peas are in pod at the moment. The other row was sowed a couple of weeks later to allow me a succession of peas. I was not too sure if I could fit a row of carrots alongside the peas. Now they are full grown I know that I can sow the carrots and they will be too small to affect the peas and the peas will not affect them as they will all be harvested within a month. The carrots will probably be baby carrots for the late autumn, early winter. Elsewhere I have replaced the broad beans with beetroot, swede and carrots My spring cabbage has been replaced by peas hopefully ready in September. Also possibly the best crop of carrots that I have grown on this plot. I sowed my cobra climbing beans amongst my early carrots about a month before they were due to be harvested. I have my first flowers on the beans so hopefully two crops this year from that piece of ground. I hope that this gives you some ideas about getting more from you plot. You can garden and harvest most months of the year, not just the summer. Give it a go! seeds are cheap if you buy them from the right source. I get mine from premierseedsdirect and pay less than a pound a generous sized packet for seeds for the price. There are other websites that offer good value.
Things to sow in August Spring Cabbage Carrots Kohl Rabi Onions Oriental leaves Winter radishes Spinach Swiss Chard Turnips
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