Vízügyi Közlemények, 1962 (44. évfolyam)

4. füzet - IX. Könyvismertetés

IV ORCHARD IRRIGATION BASED OX THE GROWTH-CURVE, WITH SPECIAL REGARD TO THE WINTER APPLE TREE By B. Sulyok No definite answer can be found in the literature to the problem of the practicable time for orchard irrigation. Starting from the assumption that a close relationship is bound to exist during the growing season between growth and moisture consumption, the author observed and measured the longitudinal growth during the growing season of the so-called master branch point-bud of fruit trees. Measurements were carried out for 5 years on four kinds of winter apple tree, eight of each kind being irrigated and eight of each kind were not. The Lotal number of trees observed was thus 64. The measurements resulted eventually in 229 growth curves which were essentially of the same shape (Fig. 1 ). Using Gauss' so-called deviation integral, growth could be expressed also in a mathematical form as: where h is the total growth during the period 2 r from springing to the end of growth, e is the base of the natural logarithm, ar = 3,00 and y is the growth at any arbitrary time t. The momentary growth is The growth curve has the shape of an S, while that of the momentary growth is bell-like (Fig. 2). By evaluating the experiments of Penman it could be established that the curve of potential transpiration is also bell-shaped, and consequently the masscurve thereof, i. е., the curve of moisture consumption is similarly S-shaped (Fig. 3). Thus the pair of curves describing transpiration, respectively moisture consumption, are essentially of the same shape as the pair of curves characterizing growth. It is thus corroborated that growth is directly proportionate to moisture consumption. Actually this is but approximately valid, since a moisture demand, however little, continues to exist also in the stagnant period of the plant, contrary to the mathematical approach, where this is neglected. The irrigation period is between the end points of rapid growth (moisture consumption) which are at 36 and 64 per cent of the growing period (Fig. 5 ). Thus for identical growing periods the irrigation period remains unchanged (Fig. 8), but varies for others (Fig. 9). The accumulation of soil moisture may be regarded approximately to follow a linear trend (Fig. 4) and thus the abscissae of the coordinate system indicate not only time, but also moisture, while the ordinatae represent not only growth, but also a quantity proportionate to Lhe crop, since under balanced growing cir(For the Hungarian text see pp. 74) ч