In the north area of Costa Rica two plots were sown: one

of minimum tillage (3 ha), and another of conventional tillage

(0,80 ha). Both tillage systems were planted with a hydraulic

sower fertilizer. The variety of rice used was the CR 2515. In

minimum tillage the sow work was conducted under conditions

of high humidity, job that is practically impossible under

conventional tillage. Under this same tillage system, there was

a lower germination and population of rice plants, mainly in the

areas where there was more stubble. In the planting cycle

2001, the minimum tillage had larger density of Murdania

nudiflora, Echinocloa colonum and Digitaria sp. In

conventional tillage the most prevailing weed was Cyperus

rotundus. The plagues and diseases were not a limiting factor

in the handling of the crop in both tillage systems, however, in

the minimum tillage there were a largger incidence of ants, of

the genus Solenopsis. In the sow 2001 cycle, in conventional

tillage had larger number of panicles /m2> to 20 cm that in

minimum tillage, while in the 2000 cycle in minimum tillage

the quantity of panicles /m2 >20cm was very low. Like wise,

the number of grains per panicle was larger for minimum

tillage in all the panicles lengths, and the weight of 1000 grains

was similar to minimum tillage in all the panicles lengths. The

estimated yield was higher in the system of conventional tillage

with 6.74 t/ha, while in minimum tillage it was of 5.91 t/ha.