CHANGES OF pH AND AVAILABLE PHOSPHORUS AND CALCIUM IN RHIZOSPHERE OF ALUMINUM-TOLERANT MAIZE GERMPLASM FERTILIZED WITH PHOSPHATE ROCK

Abstract

Availability of phosphorus (P) and calcium (Ca) is a common constraint in tropical acidic soils limiting the potential of those soils for crop production. Under such conditions, phosphate rock (PR) could become a cheap source of P and Ca for crops. The dissolution of PR, however, is a slow process that has limited its use for annual crops requiring ready-available nutrients. This study was conducted to examine the effect of aluminum-tolerant maize genotypes on the rhizosphere pH and the consequent release of P and Ca from PR. Six aluminum-tolerant maize inbreds from CIMMYT and one from the local program of FONAIAP-CENIAP were used. Sources of P were Riecito PR (PR) and commercial triple super phosphate (TSP), applied at a dose of 400 mg kg¹. Individual pregerminated seeds were placed in small glass boxes 16×14×1 Cm filled with 200 g of a plinthic paleustult soil, with pH of 4.4 and very low P and Ca. Where PR was applied, rhizosphere pH increased between 0.14 and 0.38 pH units as a consequence of the increase in Ca concentration from the dissolution of PR. Differences among genotypes in P and Ca uptake were associated with soil pH and characteristics of the root system, especially total root surface. Inbreds 4, 5, and 17 were more efficient using PR than using TSP, suggesting the possibility of breeding maize for an efficient use of field applied PR.

ACKNOWLEDGMENTS

This research was supported by CONICIT and FONAIAP.