A field experiment was laid out in a quartz sandy soil (Quartzipsamment) in Assis, State of São Paulo, Brazil, having cation exchange capacity of 35 mmol c.dm-3 and 9% base saturation. The differential response of the upland rice cultivars IAC 25, IAC 47, IAC 165 and Araguaia to the rates of 0, 2, 4 e 6 t.ha-1 of dolomitic and 2 t.ha-1 of calcitic limestone as additional treatment was evaluated. The limestone was applied in October of 1991 and the evaluations were carried out during the 1992-93 growth period. Twenty days after the plant emergence, the shoots were sampled for nutrient chemical analysis and twenty days later roots were sampled for anatomical studies. Two years after liming the largest base saturation was only 55%. The root structure remained unaltered with the liming treatments; some differences occurred only on the cortex central vascular ratio. The IAC 165 cultivar was the only one that did not respond to the limestone rates and that decreased the cortex/central vascular ratio. The liming decreased the plant manganese contents associated with the temporary soil flooding. There was also a decrease in phosphorus, potassium and zinc contents, but the nitrogen, calcium, magnesium, and iron contents increased. Shoot fresh matter yield was larger with dolomitic than with calcitic limestone for all cultivars, except IAC 47. All the cultivars showed higher magnesium and lower calcium contents in the shoots with dolomitic than with calcitic limestone. Although a positive yield response could not be obtained in the present study, it can be inferred that when upland rice is used in these soils for crop pasture renewals, dolomitic limestone might be recommended to correct acidity and magnesium deficiency in plant.
upland rice; Oryza sativa L.; root anatomy; calcium; magnesium
