MOST VITAL

Hauraki Plains Gazette, Volume 51, Issue 3111, 27 April 1942, Page 6

MOST VITAL

VALUE OF GOOD WATER BETTER THAN FERTILISER HIGHER CITRUS PRODUCTION (By A. M. W. Greig, Instructor in Agriculture, Auckland). As I gazed, out of the railway carriage window upon the burnt hill slopes of ti-tree and! bracken fern, I heard the man in the seat behind turn to his wife and! say: “Poor country here, but I suppose it could be brought in with super and lime. ’ ’ That set me thinking, and I nearly turned) to him and said: “I’m afraid I don’t agree.” Here was a piece of land, originally in bush, now steadily deteriorating through annual burning of the scrub. The wider question is: “Hasn’t the average man on the land, citrus grower included, been inclined to place too much emphasis on artificial fertilisers and manures?”

During the summer months the practical citrus grower must consider the question of water supply. A soil which can use rainfall to maintain the

optimum supply of moisture to the tree generally repays the costs of cultivation and manuring, whereas soils which suffer from an excess or a deficiency of moisture, or an alternation between these two, are generally waste lands. They do no.t repay generous treatment, and therefore usually have a low plant nutrient status. Fortuity Of The Soil

Soil fertility is not merely a matter of abundant supplies of nitrogen, phosphorus, and potassium; nor can infertility be cured Simply by loading farmyard manure and artificial fertilisers into the soil. Rather does soil fertility consist in the favourable operation of a number of factors, and of. all these factors affecting plant growth, water supply probably has the greatest weight in deciding the differences in the cropproducimg abolity between one soil and another. In any scheme for the purchase and sale of citrus fruits founded on a uniform price per case the key to success is crop per tree. If, then, available water is the determining factor in yield per tree, this factor must be given very serious consi dieration. Water is absolutely essential to successful citrus production, but it is especially necessary as the young fruits set. A citrus tree needs as much water as it can get, provided the soil is not so saturated with water that the air supply is deficient. Rain On The Orchard It is not so much the total rainfall per. annum that is important, but rather its equitable distribution throughout the year. No grower, however, can control rainfall, but, given a suitable soil, he can conserve the rainfall by certain cultural prac-

— • • - I • . tiees, such as mulching, hoeing, discing and cover cropping.

Of the rain that falls on a citrus orchard, part evaporates, part runs (ff the surface, often carrying soil particles with it, which results in soil erosion, and part enters the soil. Only that water which enters the soil and is retained there until required is of value to the citrus tree. The degree to which a soil is able to conserve moisture depends very largely upon its humus-content, humus being that portion of the organic matter of the soil which has become structurally unrecognisable. It is important because of its waterholding properties, and also because it is the seat of activities of the soil micro-organisms.

This important soil constituent will be discussed later, but during the summer months remember that over-culti-vation and the fetish for a weedless orchard or destruction of humus is a mistake. As they transpire large quantities of water, weeds require to be suppressed by mowing or light discing rather than by too much harrowing.