Resumen

SEQUERA, Omaira  y  RAMIREZ, Ricardo. Fósforo, calcio y azufre disponibles de la roca fosfórica acidulada con ácido sulfúrico y tiosulfato de amonio. INCI [online]. 2003, vol.28, n.10, pp.604-610. ISSN 0378-1844.

N, P, Ca and possibly S are critical in maize and sorghum production in acidic soils. The use of phosphate rock (RF) acidulated with sulfuric acid (AS) as source of these elements in short term crops is possible. The use of ammonium thiosulfate (TSA) for RF acidulation combined with sulfuric acid (SA) is feasible. An acidic soil low in P and Ca was used to test the efficiency of RF acidulated with SA and TSA. Field and incubation experiments were conducted on limed (SE) and non-limed soil (SSE). Fertilizer treatments were: RF acidulated with AS (RA), RF acidulated with 70% AS and 30% TSA, (R30T); RF acidulated with TSA (R100T), triple super-phosphate (SP) and 0P. The P dosis applied to the soil was 400mg·kg^-1. Released P in SSE with RA and R30T was higher than with RF and R100T, but P released from R30T in SE was lower than that from RA in the first 21 days. In SSE there were no differences in maize dry matter (MS) where SFT, RA or R30T were used, but MS was higher than where RF or R100T were applied. In SE there were no MS differences between R30T, RF and R100T. In SSE maize P uptake was higher when RA and R30T were used but in SE, P uptake was higher in R30T. A significant negative relationship was found between root length and P uptake in SE, while in SSE they were not related. Partial acidulation of RF, substituting 30% AS by TSA, does not change the efficiency of RF as a P source.

Palabras clave : Fertilizantes ; Longitud Radical ; Maíz ; Absorción .