J. Rikanova et R. Rozsypal, THE DYNAMICS OF SOIL PHOSPHATES AND THEIR CHANGES IN CONDITIONS UNDERIRRIGATION, Rostlinna vyroba, 39(9), 1993, pp. 845-850
In field trials performed in the years 1984 to 1987, in maize growing
region, established on chernozem, soil phosphate regime under irrigati
on and without it was studied with three variants of fertilizing, untr
eated variant, variant treated with fertilizers and manure and the var
iant fertilized solely with industrial fertilizers, in crop rotations
with lucerne arid liming, and without liming and lucerne. The studies
were carried out to the depth of 0 to 60 cm, with 15 cm layers. Fracti
ons of inorganic phosphorus were determined by the method after Chang-
Jackson (first fractions of L - P, Al - P, Fe - P, Ca - P and residual
phosphorus as fraction V) in soil samples. Exchangeable pH/KCl was de
termined as well. Irrigation reduced significantly pH compared with un
irrigated variant, in particular in interaction with fertilizing. This
unfavourable effect was eliminated by organic manuring. Long-term irr
igation resulted usually in significant reduction of the content of al
l phosphorus fractions, except for Fe - P. The most significant change
s were recorded with the fraction Ca - P and residual phosphorus (frac
tion V). These differences were caused by more intensive formation of
organic phosphorus and increased crop yield.