A field experiment was conducted, to evaluate the effect of applying a liquid lime amendment  on  rice  yield  and  soil  fertility,  in an Ultisol at Los Chiles, Alajuela. The liquid amendment contains 40% of Ca in form of CaCO<span name="style_sub">3</span> and 6.9% of N as urea (Cal 56®). The treatments were: control without lime; Cal 56 8 l.ha<span name="style_sup">-1</span>; Cal 56 10 l.ha<span name="style_sup">-1</span>; and Cal 56 6 l.ha<span name="style_sup">-1</span> + Nitro LL 4 l.ha<span name="style_sup">-1</span>. Nitro LL is a controlled-release liquid  fertilizer that contains 33% of N. The products were applied in water with a back pump, using  a volume of mixture of 200 l.ha<span name="style_sup">-1</span>, spraying on  the ground 8 days after rice germination. Plots 10x10 m were used, with an experimental design of randomized complete block with 4 treatments and 4 replicates. There were no significant differences in panicle size (cm), number of  spikelets per panicle, total number of grains per  panicle, number of grains filled,  empty  grains,   and  1000-grain  weight, although most of  these variables showed higher values than the  control with the application of the  liquid  amendment.  There  were  significant differences (p&lt;0.01) in rice grain yield. The dose of 8 l.ha<span name="style_sup">-1</span>  of Cal 56 showed the best agronomic yield. The dose of 10 l.ha<span name="style_sup">-1</span>  of Cal 56 increased slightly the content of Ca and ECEC in the soil.  of Cal 56 increased slightly the content of Ca and ECEC in the soil.

Acid soils; liming; liquid lime; ultisols; rice Oryza sativa