NITROGÊNIO RESIDUAL EM SOLO ADUBADO COM DIFERENTES FONTES E INTERVALOS DE APLICAÇÃO DE NITROGÊNIO

Abstract

The objective of this work was to evaluate the residual nitrogen contents behavior in a soil fertilized with four different nitrogen sources (ammonium sulfate, calcium nitrate, urea and monoamonium phosphate) at dosage of 80 kg.ha-1, divided in 2, 3, 4 and 5 parcels, applied through drip irrigation on the melon production, in field conditions, at the Fazenda Cajazeiras, located in Tibau, RN, Brazil. A 4 x 4 factorial, completely randomized block split-plot design, with four replications was used. Soil samples were collected before planting and 40 days after the first nitrogen use to the depth intervals of 0-15, 15-30, 30-45 and 45-60 cm, on which total mineral nitrogen, NH4 +, NO3 - e NO2- was determined. A differentiated behavior of the nitrogen sources regarding the ammonium furnishing to the soil was observed, existing a decreasing tendency of the ammonium contents with the increase of the fertilization partitioning and soil depth. For nitrate the highest concentrations were found on the surface interval and no effect of the fertilizer partitioning was observed. The highest concentrations of nitrite were found on the 30 - 45 cm depth interval and the total mineral nitrogen was concentrated mainly on the root absorption region. The biggest accumulation of total mineral nitrogen in the soil was originated from employment of MAP and ammonium sulfate and the lesser accumulation was due to urea use.