The Science of Fertilisers
This is the time of the year when soil temperatures are great for plant growth. Roots work over-time to extract minerals, dissolve them in water and transport them through the phloem bundles to the leaves of plants. The photosynthesis puts it all together and creates carbohydrates and chemicals that allow cell-elongation (growth).
Plants use three main elements are bulk growth “food”: Nitrogen, Phosphorous and potassium (K), which are generally known as NPK (their chemical symbols).
N is used to make green stuff: leaves and Chlorophyll (LAWNS, LETTUCE, SPINACH, HEDGES)
P is good for root development and plant health (CARROTS, PARSNIPS, POTATOES, etc)
K (potash) is for sex: flowers and fruits (TOMATOES, APPLES, STRAWBERRIES, FLOWERING PLANTS)
Other elements needed for plant functioning are needed in much smaller quantities: Mg (Magnesium) S (Sulphur) Ca (Calcium) Cu (Copper) Fe (Iron) Zn (Zinc) Mn (Manganese) and a heap more of those minor “trace elements”.
There are a few different types of fertiliser:
1) “General” Fertiliser – for general growth: usually something like N-P-K 7-3-6 or 12-4-13 (note how Phosphorus is usually less than the N and K
2) Potato fertiliser: N-P-K 3-9-6 also good for carrots and parsnips
3) Tomato or rose fertiliser usually higher in potash (K): N-P-K 3-4-9 This helps to stimulate flower and fruit growth
Of course you can always use the general fertiliser (which tends to be highest in Nitrogen) and simply add a few hand-fulls of Superphosphate (P) if you grow root crop, or hand-fulls of Sulphate of Potash (K) if you want to up the dose of K (potash) for flowers and fruit.
Organic fertilisers usually have lower concentrations of elements and they are often less prone to fertiliser run-off.
These are very general comments on how to use fertilisers; some plants require a bit more detailed knowledge or would benefit from changing fertiliser regimes in different times of the year (Cymbidium orchids have a green-growth phase to make leaves in spring and summer – followed by a flower bud initiation in autumn and flowering in winter…)
Dog Pee and Lawns
Most homeowners let their dogs use the backyard as their own personal toilet. Urine is very high in Nitrogen. Too much nitrogen will burn the grass and create yellow patches after sensational, dark green growth. A dog will usually come back to the same patch – territorial “marking”.
The concentration of nitrogen in the dog’s urine depends on the type of dog, its sex, and what the animal eats. Larger dogs will pee more and cause more damage. Female dogs also tend to cause more damage than males because they squat and urinate in one concentrated patch whereas the males spray their urine over a larger area and in much smaller doses each time. Finally, diets high in protein can increase the concentration of nitrogen in the urine since protein breaks down to release nitrogen compounds.
There are two ways to combat the pee damage: change the nitrogen concentration of your dog’s urine or focus on the lawn.
1) Feed your dog with lower protein content so there is less protein, and subsequently less nitrogen, in the urine. You can also train your dog to pee elsewhere!!
2) you can deal with the lawn directly by spraying the patches with water or treating them with gypsum pellets (made up of calcium sulphate hydrate);
In any case: hen a dog kills grass or small shrubs by frequently spraying it with nitrogenous urine, you can be assured that your plants are not killed by N-P-K, but by K-9-P.
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