Fjölrit RALA - 15.06.2004, Síða 136

Log (remaining / supplying)
Fig. 1 Elutions of Li/Br through an undisturbed column of andosol (layers A and B)
The lysimeter outflow clearly showed the impact of the stemflow on over-supplied
drainage bellow the pseudo-stems (a) and on their downstream neighbourings (b), and the
umbrella effect of leave covers (c). Under a banana cover which LAI was 4, the resulting
apparent drainage / incident rainfall volume ratio were respectively 1.2, 1.6, and 0.3, while the
bare soil (d) exhibited a ratio of 0.5. The associated solute leachings were consistent with a
high sorptivity of NO3" and a low sorptivity of K+ (fig. 2) : for NO3", immediate moderate
leaching during the three first rainfall events after supply was followed by a low leaching ;
finally, the total leaching reached 30 % of the input. For K+, a strong leaching occured until
200 mm of drainage, followed by a desorption phase whose slope was moderate. The total
leaching of K+ reached 80% of the input.
Fig. 2 Water and solute leaching under banana tree after application of KNO3.
Five replicates of four positions in respect to the stem positions were set up(a, b, c, d).
Finaly, localised over-supplied drainage downstream to the banana stemflow result in high
losses of K+, whose supply have to be sustained, avoiding the bottom of banana. On the
contrary, despite this strong local drainage, nitrate sorption allows only small losses. Further
research have to integrate distributed flows and coupling solute transports, taking into account
variable charges status.
References
Godefroy J., Roose E. J., Muller M. 1975. Estimation of fertilizer losses by run-off and drainage in a banana soil
in the south of the Ivory Coast. Fruits. 30(4):223-235.
Godefroy J., Dormoy M. 1988. Mineral fertilizer element dynamics in the “soil-banana-climate” complex.
Application to the programming of fertilization. III. The case of andosols. 43(5):263-267.
Wada K., Okamura Y. 1980. Electric charge characteristics of Ando A, and buried A horizon soils. J. Soil Sci.
31:307-314.
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