DYNAMICS OF LIQUID AND GRANULAR PHOSPHORUS FERTILZERS IN SOILS OF THE SEMIARID PAMPAS

Abstract

The objective of this work was to evaluate the effect of the application of a liquid and a granulated phosphorous (P) fertilizer on the availability of P under two conditions of soil moisture, in soils of different positions in the Calcareous Plain landscape of the Central Semiarid Region. Incubation tests were carried out with liquid polyphosphate (PL) and with triple superphosphate (SPT) in soil from top-slope, mid-slope (Petrocalcic Paleustoll) and foot-slope (Typic Haplustoll) environments, finding an advantage of PL only on the top-slope, which presented a higher level of organic carbon (CO) and a lower content of exchangeable calcium compared to the foot-slope where no differences were observed between sources. In the greenhouse tests with wheat (Triticum aestivum L.), soil from the same environments was used, with (H2) and without limitation (H1) of soil moisture, fertilizing with PL and SPT. In H1, a clear advantage of PL was not observed, while when moisture was limiting, PL favoured the production of dry matter only in top-slope and mid-slope soil. The use of PL would be recommended in calcareous soils with a low level of CO, in conditions where edaphic moisture is limiting. An adequate level of CO could contribute to improve the efficiency in the use of phosphorous fertilizers.