MINI-TUBER YIELD OF SPROUT PROPAGATED POTATO, AS FUNCTION OF NITROGEN RATES IN THE SUBSTRATE

The objective of the experiment was to evaluate the effects of nitrogen (N) rates applied in the substrate on SPAD index values and mini-tuber yield of sprouted propagated 'Monalisa' potato (Solanum tuberosum L.). The experiment was set in greenhouse, at Universidade Federal de Vicosa. Two sprouts were planted in 3 dm(-3) pots with substrate. The influence of five N rates, 0; 50; 100; 200 and 400 mg m(-3) of N, as NH4NO3, in seven phases of plant development. Plants were arranged in randomized complete block design with six repetitions. The SPAD index in the fourth leaf (LQ) increased with the increase in N rates and decreased with the plant age. Associated with the maximum mini-tuber yield, SPAD index at 37 days after planting and N-NO3 in the LQ dry matter were 49.37 and 1.36 dag kg(-1), respectively. The maximum mini-tuber yield was 177.97 g pot(-1) with 176.5 mg dm(-3) of N.