Top-dressing fertilization with nitrogen, potassium and calcium in the root yield of carrots

The carrot is included among the ten most economically important vegetables in Brazil. We evaluated the root yield, number and quality of commercial carrots, cultivar Brasilia-RL, under different top-dressing fertilizations. The experiment was carried out on a Latosol, at Fazenda Olhos D'Agua, in Sao Gotardo, Minas Gerais State, from January to April 2006. The experiment was set up in randomized blocks with nine treatments (T0= no top-dressing control; T1= 100 kg ha(-1) 20-00-20 at 30 and 45 days after sowing; T2= 200 kg ha(-1) 20-00-20 at 30 and 45 days after sowing; T3= 300 kg ha(-1) 20-00-20 at 30 and 45 days after sowing; T4= 200 kg ha(-1) 20-00-20 at 30 days after sowing; T5= 200 kg ha(-1) 20-00-20 at 45 days after sowing; T6= 300 kg ha(-1) 20-00-20 at 45 days after sowing; T7= 130 kg ha(-1) nitrocalcium at 30 and 45 days after sowing; T8= 130 kg ha(-1) nitrocalcium at 30 days after sowing and T9= 133 kg ha(-1) 15-00-14 at 45 days after sowing) and five replications. The root number and weight in each commercial class were evaluated: C-10 (>10<14 cm), C-14 (>14<18 cm), C-18 (>18<22 cm), C-22 (>22<26 cm), C-26 (>26 cm), the commercial (C), the non commercial (NC) and total (T) root number and weight were also evaluated. The total number of carrot roots (T) did not present significant differences with the top-dressing fertilizations. Maximum root yield (27.5 t ha(-1)) using 20-00-20 was obtained with the fertilization with 229.1 kg ha(-1). However the joint application of nitrogen, potassium and calcium sources increased commercial root yield, especially of those classified as C-18, which is the major commercial class.