Accumulation of dry mass in onion depending on nitrogen, potassium and plant population in direct sowing

The effects of nitrogen and potassium fertilizer doses were evaluated on the growth of two onion cultivars, grown in different plant populations. The experiment was carried out in Sao Jose do Rio Pardo in an onion production area in Sao Paulo State, Brazil. from 03/07 to 08/08/04. The experimental design was of blocks with four replications in a 2x4x4x4 factorial cheme: cultivars (Hybrids Optima and Superex), nitrogen (0; 50; 100 and 150 kg ha(-1) N), potassium (0; 75; 150 and 225 kg ha(-1) K2O) and plant populations (60; 76: 92 and 108 plants m(2)). There was significant effect on the factors separately. At the end of the cycle. the cv. Optima presented larger quantities of dry matter in file aerial parts (APDM) and in the bulbs (BDM). The application of nitrogen promoted significant increments in APDM and BDM. The influence of K on APDM was not as expressive as ill relation to that observed for the nitrogen, but similarly to this, it increased the accumulation of BDM. The increase of file population of plants reduced file APDM and consequently the BDM. The equations of accumulation of APDM and of BDM. of both cultivars, obtained as the response to the closes of N and K and population of plants, didn't differ from each other.