Interaction between nitrogen and potassium in fertilization of the piat? grass (Urochloa brizantha): productive and phytometric characteristics

摘要

In this study, the aim was to determine the phytometric and productive features of Urochloa brizantha cv. BRS Piat? cultivated in Oxisol under the influence of the nitrogen and potassium doses applied. The completely randomized experimental design was adopted in a 5x5 factorial scheme, supplying five doses of nitrogen (0, 100, 200, 300 and 400 mg dm~(-3) ) and five doses of potassium (0, 90, 180, 270 and 360 mg dm~(-3) ), with four replications. Three shoots were cut at 30-day intervals. Plant height, number of leaves, number of tillers, leaf dry mass, stem dry mass and leaf /stem ratio were assessed. The leaf dry mass at the 370, 287 and 259 mg dm~(-3) doses of nitrogen in combination with the 360 mg dm~(-3) potassium doses revealed the biggest yields (7.8, 16.9 and 11.5 g pot~(-1) ) for the first, second and third cuts, respectively. Therefore, it was revealed that nitrogen and potassium affected the phytometric characteristics in this grass in an isolated manner by doses of nitrogen potassium. The nitrogen and potassium doses interacted positively to present significantly productive characteristics at all the three cutting procedures performed in the Piat? grass when the nitrogen to potassium ratio was maintained at about 1: 1.