Vízügyi Közlemények, 1956 (38. évfolyam)

2. füzet - VII. Kisebb közlemények

(28) These proportions have to be verified by further investigations. Surface waters originate a

) from precipitations or i) from groundwater. Oit irrigated land and around it the latter have to be taken into particular consideration, because they may cause secondary alkalinity. Overirrigation and the application of high irrigation norms are particularly harmful. Material features of the soil affect strongly the resistance of crumbs, thus its water absorbing and storage capacity, as well as the irrigation system to be applied. To preserve the structure of alkali soils of low crumbling capacity spray irrigation appears most suitable in which the application of water can be controlled. If the water allotted to the soil cannot infiltrate into it, having got in touch with the surface, it dissolves salts from the soil and reflects the quality of the latter. In practical rice growing the mutual behaviour of soil and of water has been checked. According to the data ( Table I.) the composition of irrigation water changes during its stay on the field. The change is the greater, the worse is the quality of the soil, and the longer the water remains in contact with the soil. Testing the water of ricefields affected with the disease Brusone and that of healthy ricefields [1] s ows that routine water analysis methods allow 110 conclusions to be drawn relative to the dises se from thj composition of the water. The surface waters investigated (Fig. 1. and 2.) show that the water that was in contact with the soil for a considerable time well indicates the quality of the soil : Surface waters from good soils are not alkaline, such from alkali soils are so. This is beyond doubt ascertainable from the .»alkalinity ratio" (Q). The higher that value, the more is the water alkaline. Waters in the irrigation system are mostly alkaline and the amount of magnesium is also high in them. This is revealed by the value of the „magnesium ratio" (M). Magnesium acts as an „alkali forming" ion; its presence is therefore permissible only in limited quantities. Alkaline waters drained from irrigated fields may be re-used for irrigation, if they are much diluted. Water drained from irrigated land and discharged into the Hortobágy River did not deteriorate the water of the river (Table 11. whose columns are analogous to those of Table I.). Further observations are required in this line too. Alkaline waters can be improved by the increase of the calcium ion concentration. A basis for augmentation is yielded by the so-called soda equivalent (s) which is the difference between the alkalinity of the water (L) and of the calcium-magnesium equivalent (Si). If this is multiplied by 86,1 the necessary amount of gypsum required for adjusting the calcium equilibrium is obtained. The adjusting material has to be admixed to the irrigation water directlv at the place where it is turned on the field. E. g. data of a water to be improved : From this the amount of gypsum required for the improvement of the water, which can be read off Fig. 3. as well : The described method of water improvement has proved effective in practice. In 1954 it was successfully applied to about 330 hectares at Hajdúnánás. The composition of the water of the East Main Canal has been examined at different times and has been found according to data (Fig. 4.) fit for irrigation and of practically uniform composition. Solid residue Alkalinity (L) Ca + Mg equivalent (S^ Soda equivalent (s) .... 300 mg/1 13,6 8,8 4,8 X = 86,1 x 4,8 = 413 mg/1