•34 1 —!—I—1—r I il I—t—1—t—l—I—I—l—I—i—l—t—i—i__J—i—|—I—t—i—I—i—i—I—i—i—I—i—i—1 4 4 |—i—,—[__!—i—!—i—i—L_)—)—I—i—i—!—i—i—!—(—i—I—i—h-J—i_i—L_H—i—I—i—i—I—i—i—
I II 21 31 I0 20'30 9 19 29 9 19 29 8 18 28 8 18 28 7 17 27 6 16 26 8 18 28 7 17 27 7 17 27 6 16 2E I II 21 31 10 20 30 9 19 29 9 19 29 8 18 28 8 18 28 7 17 27 6 16 26 8 18 28 7 17 27 7 17 27 6 16 26 D A T E S |' J m * | AUG. | SEP. | OCT, | NOV. | DEC. | JAN. | FEB- | M A D | APR | MAY | JUNE | D A T E S | "J U L Y | t u g- | sm- | 0<:T- | "0 V' I P i C- I M>l- I f E S- I M A B- I * " * • I M A Y I J U N E I
FIG. 6 (a). Annual movement of soil moisture, General Pico. FIG. 6 (b). Annual movement of soil moisture, Guatraché.
Upper: isopleths of per cent moisture content; lower: total Upper: isopleths of per cent moisture content; lower: total water storage. water storage.
saturation of the soil during the winter months: from
M a y to July at ' Trenque Lauquen, from March to It will also be noted that the annual water storage September at General Pico, and in September only at variation is 102, 76, and 58 m m . at Trenque Lauquen, Guatraché. Whilst this characteristic could be changed General Pico, and Guatraché. The available soil water if truer constants than those obtained by laboratory is 57, 58, and 26 m m . respectively. Total water storage, methods were available, it shows a different peculiarity in accordance with the texture and depth of these in these western soils, which would appear to confirm soils, is 156,114, and 80 m m . , which values, compared to the assumption that climatic conditions in the western the relatively low values for m a x i m u m water-holding pampean steppes resemble rather those that contribute capacity, give high relative moisture values, always to the formation of chernozem-type soils in the northern above 50 per cent,
hemisphere.
Climatology and microclimatology / Climatologie et microclimatologie Available soil water (mm.) Water accumulated ill m .
T A B L E 17. Water balance of Guatraché (Record: 1949-51; equivalent moisture: 99 m m . per 1 m . ) Available soil water (mm.) Water accumulated in 1 m .
1. Knowledge of soil water storage is of the utmost importance in studying the hydric balance, and the relative ease with which it m a y be measured warrants its adoption as a routine practice by the agricultural meteorological services, in accordance with the recommendations repeatedly m a d e by the World Meteorological Organization.
2. Knowledge of the hydric balance of the soil in the agricultural process should be extended to the various aspects of land management, to the different crops, and to the complete rotation cycles.
3. The agricultural process tends to increase the water-holding capacity of the soil and to reduce the losses by surface and deep run-off. It also contributes to increase the losses due to local évapotranspiration during cultivation.
4. T h e northern hemisphere's steppes develop in climates with a lower precipitation than in the southern hemisphere, owing to the fact that they
consume practically no water during the cold half of the year.
The pampean steppes consume water during the cold half of the year, consequently they require higher precipitation values in order to maintain herbaceous vegetation, and the soils, especially the chernozem type, do not follow the yearly over-saturation rate of the Russian steppes. This also causes leaching and degradation of this type of soil.
The determination of hydric constants under field conditions and b y physiological experiments, as well as the study of records covering a greater number of years, would give more validity to the hydric values dependent on them.
This difference and the difference in vegetation would appear to warrant a n e w designation—that of pampa—for this type of vegetation characteristic of the southern hemisphere (temperate latitudes of Argentina, Australia, and South Africa) and high plateaux of the equatorial regions where évapo-transpiration is approximately equal to precipitation.
Water storage in semi-arid soils A C K N O W L E D G E M E N T S
Acknowledgement is due to the authorities of the Institute of Soils and Agrotechnics of the National Meteorological Service of Argentina w h o facilitated the work carried out; to M r . Enzo 0 . Mauri, Miss Edith
Emmagasinage de Veau dans les sols semi-arides (Juan J. Burgos et Marcos Tschapek).
1. L a connaissance de la quantité d'eau emmagasinée dans le sol est d'une importance capitale pour l'étude du bilan hydrique, et, c o m m e les mesures sont à cet égard relativement faciles, les services de météorologie agricole pourraient y procéder de façon suivie conformément aux recommandations répétées de l'Organisation météorologique mondiale.
2. Les recherches sur le rôle du bilan hydrique du sol en agriculture devraient être étendues aux divers aspects de l'utilisation rationnelle des terres, aux différentes espèces cultivées et à la totalité des cycles d'assolement.
3. L a culture d'un sol tend à en accroître la capacité de rétention de l'eau et à réduire les pertes par ruissellement superficiel et profond. Elle contribue également à augmenter les pertes dues à l'évapo-transpiration locale au cours des opérations de culture.
4. Les steppes de l'hémisphère boréal se développent dans des climats où la pluviosité est plus faible que dans l'hémisphère austral parce qu'elles ne
1. A L B R E C H T , F. "Der jetzige Stand der Wârmehaus-haltsforschung", Met. Z., 1943, p. 43-56.
2. . "Die Méthode zur Bestimmung der Verdunstung der naturlichen Erdoberflache", Arch. Met., Wien, (1-2) Heft.
1950, 38 p.
3. B O L S H A K O V , A . F. Pochvovedenie no. 1, 1951, Moscow.
4. B R O W N I N G , G . M . Soil Sci.,vol. 52, 1941, p. 445.
5. B U R G O S , J. J. "Project of technical regulation", Com-mission de météorologie agricole, World Meteorological Organization. 1953. (Document no. 3.)
6. D O U G H T Y , J. L.; B U R G O S , J. J. "Soil moisture", Com-mission de météorologie agricole, World Meteorological
di Neubourg, Miss Maria C a m p m a n y , and the staffs of the Geohydrometry Laboratory of the National Meteorological Service and of the Soil Physics Labo-ratory of the Institute of Soils Science and Agrotechnics, w h o , in one w a y or another, co-operated in the prepa-ration of this paper.
consomment presque pas d'eau pendant le semestre froid de l'année.
5. Les steppes du type p a m p a consomment de l'eau pendant la moitié froide de l'année ; aussi faut-il des précipitations plus abondantes pour qu'une végétation herbacée puisse subsister et les sols, particulièrement ceux du type tchernozem, ne suivent pas le rythme annuel de sursaturation des steppes russes. C'est là une cause de lixiviation et de dégradation de ce type de sol.
6. L a détermination des constantes hydriques dans les conditions naturelles et au m o y e n d'expériences physiologiques ainsi que l'étude d'observations accu-mulées pendant de longues années renforceraient la validité des grandeurs hydriques qui en dépendent.
7. Cette différence et la différence de végétation semblent légitimer l'emploi d'une désignation nouvelle — celle de p a m p a — pour ce type de végétation caractéristique de l'hémisphère méridional (latitudes tempérées de l'Argentine, de l'Australie et de l'Afrique du Sud) et des hauts plateaux des régions ecuatoriales où l'évapotranspiration est à peu près égale aux précipitations.
Organization. 1949. (Document no. 15 CIR/IMO/T/263.) 7. E M B E R G E R , L . " U n projet d'une classification des climats
du point de vue phytogéographique", Bull. Soc. Hist, not. Toulouse, vol. 77, 1942, p. 97-124.
8. F I N A , A . L . D E ; S O R D E L L I , D . A . " U n año (1937) de determinaciones semanales de la humedad del suelo y subsuelo en Buenos Aires", Rev. Agron., Lisboa, vol. 31, 1943, p. 127-60.
9. F R E N G U E L L I , J. "Rasgos principales de fitogeografia argentina", Rev. Mus. La Plata (nueva serie), vol. 3, 1941, p. 65-181.
10. H A R R I S , F. S. Utah Agrie. Exp. Sta. Bull. no. 173, 1920.
R E S U M E
BIBLIOGRAPHY/BIBLIOGRAPHIE
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