Maintaining Soil Fertility In The Home Garden

Press, Volume CVIII, Issue 31658, 19 April 1968, Page 6

Maintaining Soil Fertility In The Home Garden

Ths Horticulture Division, Department <rf Agriculture, issues many pamphlets and bulletins of value to horticulturists be they home gardeners or conunerlcal growers. One such leaflet is entitled “Soil Fertility in the Home Garden”—Canterbury district, and this has been adapted for this page. Organic matter and plant food elements supply the soil and plant respectively, to the benefit <A the latter. Organic matter is readily exhausted and must be continually replaced. However, its functions are riot always fully understood and is generally thought to be solely a plant food and its addition to the soil is often regarded, as sufficient to ensure all requirements of the plant Thia is not so. Organic matter serves as a storehouse or supply of plant nutrient elements; It improves soil aeration, soil structure and tilth and soil warmth; it increases the moisture-holding capacity of soils; it decreases water run-off loss: it encourages the growth of soil microorganisms: and helps drainage in clayey or heavy >aoils. There are several methods by which an increase of organic matter in the soil can be accomplished. Composting The compost heap la the best means of utilising erop residues, lawn and hedge clippings, household refuse, animal manures, etc. Diseased material should not be used for composting as very many diseases are persistent and such material can prove a source of re-infection later.

Green Manuring Utilising a crop such as blue lupins, field peas, oats, barley or mustard (which however should only be used if the area is completely free, of the disorder known as club root of brassicas). This provides an excellent means of building up soil fertility as there is seldom enough compost for complete coverage of the vegetable garden. In digging in this green crop or any form of partially rotted material always leave them close to the surface (not trenched in) where they decompose more rapidly. Decay can be speeded up by adding 1 to 2 ounces per square yard of a nitrogenous fertiliser such as sulphate of ammonia or dried blood. Digging in of materials In preference to composting is still far more desirable than wasting it all by dumping it. During the process of burial a nitrogenous fertiliser should be added to speed up decomposition by encouraging bacterial activity. Supplementary Fertiliser It is seldom that sufficient compost or other organic material is available to provide enough for all the

ground and only rarely does it contain sufficient plant food to supply the full requirements of the crop; It is also only available at slow rate. It becomes necessary to supplement the compost dressing by adding fertiliser* to obtain maximum results. The major element* required by all plants are nitrogen, phosphorus and potassium and these are required in different amounts for different kinds of plants. The most important thing to observe in their application is not to do so indiscriminately, which can be not only wasteful but also harmful, A balanced mixture is preferable rather than one containing only one element if the exact rates of the various elements tor various crops cannot be followed. Nitrogen promotes leaf growth and is of special importance in the production of leafy vegetables such as lettuce, diver beet and cabbage. It is soon leached from the soil and a deficiency is marked by poor colour and stunted growth. Phosphorus in the form of phosphates greatly stimulates root activity which hastens plant growth particularly in the early stages. It is generally lacking or insufficient in many soils. Lack shows as purpling of foliage. Potassium is supplied in toe form of potash and assists in the formation of sturdier plants which are more resistant to disease and improves the development and colour of flowers. Where It is in short supply the margins of foliage in autumn often

appear scorched. Calcium added by means of lime is necessary to decrease the degree of soil acidity which promotes the availability of all necessary nutrients and greatly facilitates management of heavy or clay soils by causing floculation of the soil particles, thus improving drainage. General purpose mixture* (1) Sulphate of ammonia 1: Blood and bone 5: Superphosphate 2: Sulphate of potash 1. (Parts by weight). This mixture should be used at the rate of }lb per square yard several days before sowing or planting and raked in, and is particularly suitable for leaf crops. Mixtures more suitable for specific crops are as follows and can be used at up to 4 ounces per square yard. (2) Legumes (peas, beans): Sulphate of Ammonia 1: Superphosphate 2. (3) Root crops: Sulphate of ammonia 1: superphosphate 3: sulphate of potash 1. (2 for carrots and tomatoes). The use of lime must be discretionary as excess not only results in alkalinity but leads to plant disorders due to the locking up or unavail-

ability of soma trace elements. Generally, however, an annual topdressing in most gardens is behefltdsl—2-3 ounce* per square yard, preferably in late autumn or winter. Compound fertiliser mixtures no* available provide an excellent substitute for the above mixtures'. They normally comprise the three major element* nitrogen, phoeptaoru* and potassium—and trace element* also in tome case*. Different manufacturer* bring out various mixture* and it is advisable to ascertain the composition

first As they contain a higher percentage of available soluble fertiliser* they can be used more sparingly -2-3 ounces per square yard being a suitable dressing* Leaching during heavy rain is quite common with mineral fertilisers, especially those containing nitrogen and potash- In areas subject to heavy rain—and particularly on lighter soils—fertiliser dressings could well be split half in spring or at the time of sowing pt planting and half in mid«eason to get 1 the maximum benefit from them.