Baby leaf market and production systems are beginning in Brazil. Some of the few hydroponically growers are adapting the nutrient film technique (NFT) system in their farms, however without the necessary knowledge, provided by research, for that. Thus, the aim of this research work was to evaluate the effect of electrical conductivity of nutrient solution and space between plants on table beet and lettuce for baby leaf production in NFT hydroponic system. Two independent experiments were carried out, from December 2011 to March 2012, with table beet and lettuce in a greenhouse of 126 m 2 , at Northeast Paulista field station of Paulista Agency of Agribusiness Technology in Mococa, São Paulo state, Brazil. The experimental design was a split plot with randomized blocks replicated four times. The main treatment was composed of different electrical conductivities of the nutrient solution (0.4, 0.8, 1.2 and 1.6 dS/m) and the secondary treatment consisted of different spacings between plants (2.5, 5.0 and 10.0 cm) for both species. Harvest was carried out when leaves of each specie reached length of approximate 15.0 cm. Higher yields of 5.5 and 3.1 kg/m 2 were obtained with 1.6 and 1.4 dS/m for table beet and lettuce, respectively. The space between plants of 2.5 cm promoted greater yields of 4.2 and 4.9 kg/m 2 for table beet and lettuce, respectively.

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Concerning the baby leaf production in trays, substrate can be reused for a certain number of times depending on its chemical and physical characteristics, but populations of pathogens such as Pythium aphanidermatum and Rhizoctonia solani that can cause damping off of lettuce, can build up during the reuse of this substrate. Solar treatment in a solar collector can be an alternative for the disinfestation of these substrates. Thus, the objective of this research was to study the reuse of coconut fiber substrate and its solar treatment in solar collector on baby leaf lettuce production. The experimental design was randomized blocks, in a factorial scheme 4 (first-use substrate, reused once, reused twice and reused three times) x 2 (with and without solar treatment), with four replications. The substrate reused 3 times provided the highest yield, 7.4 kg/m2, 14.8 cm plant height, 7.8 leaves, length and width of the largest leaf 13.9 and 4.8 cm, respectively; 3.4 and 0.21 g/plant fresh and dry mass, respectively; pH 6.8, 0.34 and 0.35 dS/m electrical conductivity, 25.1 and 30.2 mg/L NH4 + and 16.8 and 14.6 mg/L NO3 -, dry density 169 and 177 kg/m3 and water holding capacity 53 and 57% for substrates with and without solar treatment, respectively. There was an increase in the population of P. aphanidermatum, but the solar treatment was effective to eliminate this pathogen, and R. solani was not detected in the substrates. This study showed that the reuse of a coconut fiber substrate for one to three times could enhance the yield of lettuce baby leaf and promote the chemical and physical characteristics of the substrate.

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