Nitrogênio no crescimento e produtividade de plantas de alface cultivadas em confinamento radicular

Abstract

The objective of this research was to test the hypothesis that under confinement of roots in a limited volume, the negative effects on growth and yield of lettuce plants can be compensated by increasing the availability of N in the root media. The experiment was conducted between Augut 11th and September 23th 2011. Lettuce transplants, cv. Stella, bearing five leaves were planted in pots using sand as substrate. Treatments were three root confinement levels and five N concentrations in the nutrient solution, in a 3 x 5 factorial randomized experimental design. Root confinements were simulated by pots sizes of 2.5 dm³ (no confinement, the control); 1.0 dm³ (moderate) and 0.4 dm³ (severe). Nitrogen concentrations were: 5.55 (T1), 8.05 (T2), 10.55 (T3), 13.05 (T4) and 15.55 (T5) mmol L-1. There were interactions among treatments and plants grown under severe root confinement supplied by the nutrient solution at the N concentration of 10.55 mmol L-1 N reached similar leaf growth than those under no root confinement at 5.55mmol L-1 N. Increasing the N concentration in the nutrient solution enhanced shoot growth but decreased root growth. The severe root confinement did not affect root growth but reduced shoot growth. It was concluded that shoot growth of plants under root confinement is only partially compensate by increasing the availability of N in the root media.