THE VEGETABLE GARDEN.

New Zealand Herald, Volume LXVII, Issue 20628, 29 July 1930, Page 14

THE VEGETABLE GARDEN.

USE OF FERTILISERS.

BY ff.S.R

The chief foods required by tho various crops grown in the garden aro obtained from tho soil, tho atmosphcro and moisture. At present we aro more or less concerned with tho9Q obtained from the soil, as tho gardener has very littlo control over the others. There aro a certain number of persons who think that all that is necessary to grow crops successfully is to put them in their respective plots and watch their development. How wrong this treatment is does not always become apparent until several have passed. It is only when the ground becomes impoverished that these persons realise that they have made a big misTlie duration of the period before tho awakening will depend on whether tho soil was rich or poor at the beginning. Tbo difference between a poor soil and rich ground is that tho latter contains a much greater store of plant food in an available or easily convertible state than the other. Even a rich soil can become " played out," however, if nothing is done to replenish the stores of food to compensate for tho quantities used up by the crops. Vegetable growing takes far more out of the soil than is used when the ground is not cultivated, but is under grass, for instance. Tho reason for this is that the crops are growing up to the limit of the food available, whereas tho grass at its most rampant rate of development is not capable of using np tho total amount that, is mado available by the soil processes. Moreover, the grass has slack periods of growth, but with tho intensive cropping that is common nowadays, the soil gets no opportunity for retrenchment. Three Important Elements.

Most soils contain a fair quantity of the three most important foods that aro derived from this source, i.e., nitrogen, phosphorus and potash, but theso aie rendered available at a fairly slow rato. If the crops aro to make a more rapid development than the supplies provided by the soil permit, it will be necessary to supplement the quantities by artificial means. ... . , It is essential that fertilisers be used judiciously, though, or the maximum benefit will not be obtained from their use. It is not much good, for instance, applying nitrogen to a crop that uses a lot of phosphorus and potash, as it will be wasted, besides which one runs the risk of upsetting the habit of the plants and cause them to make an undesirably vigorous growth. What one has to consider beforo applying any fertiliser is what kind of food the plants will require. When this is decided on the gardener may apply tho fertiliser or mixture of fertilisers that is deemed most suitable. As far as the quantity of tho manure to be upplied is concerned, ono must be guided chiefly by the estimated contents of the soil. One should really provide sufficient to carry the crop through without having to draw on the supplies in the soil at all, so that this can be kept as a reserve. When starting to make a garden in new ground that is known to be rich, ono is tempted to bo rather mean in the matter of fertilisers, but this is a mistake. If ono is generous in this matter right from the start, it will be found that the ground will not require to be renovated nearly as often as would bo necessary otherwise.

Pree Use of Fertilisers. There are no harmful results to be feared from the generous uso of fertilisers if one uses one's discretion in their application. For instance, one should not apply them dry, or in liquid form, when the soil is parched, unless the crops are given a good watering 24 hours beforehand. Otherwise, one is liable to induce reverse osmoeis in the roots, through having the soil solution too strong. This means that the roots will allow the sap to flow out into the soil, instead of taking in some of the soil solution. The* net results of this is that tho plants will wilt and eventually die. Had the soil solution been diluted by tho presence of more moisturo in the ground the reversal of tho process of osmosis would not have occurred.

The soil solution may be made too strong in another way also. Instead of there being too little moisturo, there can be too much fertiliser. Excessive applications of manure aro most undesirable, but at tho same time it is dosirablo that tho crops be supplied with plenty of food to make their growth. Rather than run the risk of giving tho plants an overdose, the gardener should split his application up into two or three portions, to bo applied at intervals during the development of the plants.