Field experiments were set up during nine years, in a low fertility, very a
cid Cambisol, with the objective of evaluating the response to lime and pho
sphorus of four wheat genotypes differing in tolerance to soil acidity. The
experiments were carried out without irrigation, in randomized blocks with
a split-split plot design, with four replications. The plots contained the
three rates of limestone (0, 6.5, and 13 ton ha(-1)); the split-plots the
rates of phosphorus (0, 30, and 90 kg ha(-1) of P2O5), and the split-split
plots the wheat varieties (IAC-5, IAC-24, IAC-60 and Anahuac). Lime was app
lied in the first year (1987) and reapplied in 1991; phosphorus was applied
yearly. Wheat varieties tolerant to soil acidity(IAC-5 and IAC-60) were mo
re responsive to limestone and phosphorus application and, even in soils wi
th acidity partially neutralized, showed higher grain yields than the acid
sensitive variety (Anahuac). Limestone and phosphorus caused a decrease in
the straw:grain ratio because they increased the grain yield more than the
vegetative growth. This ratio was lower and more stable with IAC-60. Genoty
pes IAC-5 and IAC-60 were the most efficient to use the applied phosphorus
to produce grain. Yields of grain and straw,and plant size were usually mor
e affected by phosphorus than by limestone application.