HOME GARDENS

Bay of Plenty Beacon, Volume 14, Issue 99, 17 February 1950, Page 6

HOME GARDENS

(By J. S. Yeates, Massey Agricultural College) FERTILISERS In order to get the best out of any garden fertilisers are necessary. We have already considered some of the sources of bulky organic manure. They are essential to maintain humus in the soil, but the socalled artificial fertilisers are also necessary to get the full benefit from our efforts. All plants need several minerals from the soil, including nitrates, phosphates, potash, calcium, sulphates and compounds of iron and magnesium. Minute traces of other chemical elements are also needed .—including boron, manganese, copper, cobalt, and molybdenum. The first four on the list are those most often lacking in soils because the plant uses relatively large quantities of them; but some of the others can be in short supply and if so, various “diseases” show up. Boron is a case in point. In New Zealand lack of it causes the “mottled heart” disease of turnips and swedes, and “corky core” of apples. A pound or two of ordinary borax to the acre will prevent these troubles, and that is why superphosphate mixed with borax can be bought as “borated super.” Copper is often lacking on peaty soils, and a pound or two of bluestone to the acre will overcome the difficulty. The marshlands district near 'Christchurch is one place in New Zealand where copper has been found to give good results in growing onions, and I believe that one of the “secrets” of onion growers in the Opiki district of the Manawatu lies in using small quantities of bluestone in the soil.

When the question of large dressings of fertilisers is concerned there are only four types to be considered, nitrates, phosphates, potash, and lime. I have already dealt with lime a few weeks ago, emphasising that it should be used with care, witholding unless you are qertain that the crop needs it. That leaves nitrates, phosphates and potash as the main fertilisers to be used in quantity. Phosphates are undoubtedly the most important of these three, simply because they are relatively in shortest** supply in most of our soils. They are used in very large quantities in agriculture and arfe certainly the first type of fertiliser to merit attention. Superphosphate (“super” for short) is comparatively cheap and it is a good policy to buy it by the bag or the hundredweight. Superphosphate, however, is not the only source of phosphate. It contains a high percentage of water-soluble phosphate which is quick acting but for that very reason is not always favoured by experienced gardeners. They prefer relatively insoluable and slow-act-ing phosphate manures • such as bone meal of finely ground North African rock phosphate. The bone which should be in blood-and-bone manure, is of course equivalent to bone meal. Basic slag, when available is a good source of phosphate,

Nitrates are of very great im-) portance to plants, and especially in the growth of leafy crops, such as the greens—lettuce, cabbage and the like. Too much nitrate, in proportion to phosphate can lead to unbalanced growth, resulting in a great deal of soft tops but a tendency to diseases. A properly “balanced” mixture of manure aims at' preventing this sort of trouble. The term “nitrates” is used because most nitrogenous manure (but not all) is taken up by the roots after soil organisms have changed it to nitrate. The simplest source of nitrate is sodium nitrate. This is a readily soluble, very quick-acting fertiliser and as a rule is all used up or washed out of the soil a very few weeks after applying it. It tends to make the soil alkaline. Ammonium sulphate is about equally soluble but is rather slow-acting than nitrate. Dried blood whether used by itself or as blood-and-bone, is a slow-acting form of nitrogenous fertiliser which is in very great de* mand by market gardeners, so that the average gardener finds it difficult to buy.

The use of potash as a fertiliser has not been very prevalent in this country in the past, but lack of potash is now becoming evident in many districts. The action of potash on plants is to balance the effects of phosphate and nitrate and to produce; some people maintain, better “quality” in crops like potatoes. It appears also to render plants less liable to attack by disease. The main forms of potash are sulphate of potash, muriate of potash, potash salts and kainit. They contain approximately 50 per cent, 60 per cent, 30 per cent and 12 per cent of potash respectively. When applying al three fertilisers, phosphate, nitrogen and potash, a good general proportion to use is six parts of super, two of ammonium sulphate, and one of potassium sulphate. Two ounces per square yard is the generally advised amount.