February weather can swing from one extreme to another, grey and overcast, persistent rain and even snow and with our ever-increasing climate crisis who knows what will come next. Whatever the conditions, there is a limit to what one can do usefully in the allotment. Providing the ground is not frozen, and if one is into digging one can complete the task and improve the structure and composition of your soil by incorporating as much manure or compost as one can. Either dig or leave it on top of the surface for it to be dragged down underground by earthworms.
As long as the soil is not waterlogged or frozen, February is a good time to take a look at your soil and see if it needs any attention before the growing season begins.
So, what sort of questions are necessary to ask about one’s soil? These questions include what type of soil do I have, heavy or light, in our allotment it is mainly light, and, what chemistry is it acid, alkaline or neutral – this is the Ph of a soil. Whatever the answer is one can make it fertile and well-structured all ready for a great growing season.
So, let’s look at Ph
Soil pH is the measure of acidity (sourness) or alkalinity (sweetness) of a soil. The pH scale goes from 0.0 to 14.0. The most acid soil is 0.0 and the most alkaline is 14.0. Halfway along the scale, 7.0, is neutral, neither acid nor alkaline. A soil gets more acid as the pH values decrease from 7.0 to 0.0 and is more alkaline as pH values increase from 7.0 to 14.0.
Soil pH can affect plant growth in several ways. Bacteria that change and release nitrogen from organic matter and some fertilizers operate best in the pH range of 5.5 to 7.0 making this the optimum pH range. Plant nutrients leach from the soil much faster at pH values below 5.5 than from soils within the 5.5 to 7.0 range. PH is not an indication of fertility, but it does affect the availability of fertilizer nutrients. The soil may contain adequate nutrients yet plant health may be limited by an unfavourable pH level.
Although the optimum range is 5.5 to 7.0 some plants will grow in a more acid soil and some at a more alkaline level. Vegetables grow best in a slightly acid soil with a PH of 6.5 although pH 7-7.5 helps to reduce club root diseases in the cabbage family
To correct the pH of or “sweeten” an acid soil (5.5 to 0.0) use lime or dolomite. Lime contains mainly calcium carbonate and dolomite contains both calcium carbonate and magnesium carbonate. Ground limestone and dolomite are less likely to burn plant roots than hydrated lime and is therefore recommended for home use. The greater the amount of organic matter or clay in a soil, the more lime or dolomite required to change a pH level. The best results will be achieved if you incorporate the lime uniformly at least six inches into the soil.
If soil is too alkaline you should determine if it is due to the soil characteristics or an over dose of lime at some stage. It is very difficult, if not impossible, to change appreciably the pH of naturally alkaline soils however you might be able to by using sulphur, ammonium sulphate, or a similar acid forming material. If this high pH is due to applied lime or dolomite, acid forming materials like sulphur or ammonium sulphate can also be applied. To decrease the soil pH, use superfine dusting or water-soluble sulphur. Repeat applications of sulphur should not be made more often than once every two months because soil sulphur oxidizes and mixes with water to form a strong acid that can burn the plant roots — so use it with caution.
A pH soil test will tell you whether your soil is within the optimum range or whether it will need to be treated to adjust the pH level. These acid testing kits can be purchased quite cheaply typically £10-£20 on the internet and come in two types of testing. There is the chemical-based tests or the electronic testing devices. The latter contain one or two electronic probes that may not only measure Ph but temperature of the soil and water content.
Depending upon what one wants to grow one needs to ensure the soil has the correct Ph and I have listed a number of plants below that relate to Ph. Acidic plants tend to need a soil pH of around 5.5. Some acid lovers may do well all the way down to a pH of 4.5. The lower pH of 4.5 to 5.5 allows the acid loving plants to better absorb the nutrients from the soil. Slightly acidic soil improves nutrient access!
Generally speaking, soil with a pH below 7 is considered acidic. For soil that is too alkaline, plants may have a hard time absorbing nutrient. This ultimately may result in poor growth or less than optimal growth.
Depending on the pH and a plant’s soil requirements, plants may develop a nutrient deficiency as well.
Types of test methodologies
Here are some acid loving plants that need optimal levels of Ph below 7 although some as you can see are alkaline tolerant with a Ph value just above 7 :-
- Asparagus– Alkaline Tolerant
- Beans-Pole – Alkaline Tolerant
- Broccoli – Alkaline Tolerant - Best pH 6.5-7.5
- Brussel Spout – Alkaline Tolerant – Best pH 6-7.5
- Cabbage– Alkaline Tolerant – Best pH 6-7.5
- Carrots – Alkaline Tolerant
- Cauliflower– Alkaline Tolerant– Best pH 6-7.5
- Cucumber – Alkaline Tolerant
- Garlic– Alkaline Tolerant
- Kale – Alkaline Tolerant
- Lettice– Alkaline Tolerant
- Spinach– Alkaline Tolerant
- Swiss Chard– Alkaline Tolerant
- Turnip – Alkaline Tolerant
Alkaline Loving Plants
- Bay Laurel
- Lily of the Valley