This study had as objective to evaluate the effect of the substrate on the yield of lettuce grown in aquaponic and hydroponic systems. The study was conducted at the Federal University of Grande Dourados, located in Dourados, MS. A randomized complete block design was used, with three treatments and 16 replicates. The cultivation systems were analyzed independently. The substrates analyzed were: coconut shell fiber, phenolic foam and expanded vermiculite. The plants were grown in two systems (aquaponic and hydroponic), using the NFT (Nutrient Film Technique) system. The crop used was lettuce cv. ‘Alcione’. The parameters analyzed were: crop yield and percentage of roots per plant. In addition, macronutrient contents were analyzed in the leaves. The substrate composed of coconut shell fiber was more suitable for lettuce production, since it led to higher yields for both aquaponic (2.88 kg m-2) and hydroponic (2.58 kg m-2) systems. The use of phenolic foam as growing substrate led to lower mean crop yields in both production systems analyzed, 1.94 and 2.15 kg m-2 for aquaponic and hydroponic systems, respectively.
The objective of this study was to evaluate the effect of an early application of potassium (K) fertilizer on pearl millet (Pennisetum glaucum L.) grown during fall/winter on the performance of maize (Zea mays L.) silage grown in succession. Using a randomized block design, in the fall/winter harvest, the plots were composed of millet and six doses of K (0, 30, 60, 90, 120 and 150 kg K2O ha-1) as muriate of potash (57% K2O) in addition to fallow. In the summer harvest, during the cultivation of maize, six doses of K2O were applied complementary to the doses applied in the autumn/winter harvest to total 120 kg K2O ha-1 (120, 90, 60, 30, 0) and 0 kg K2O ha-1 for the no cover treatment. An additional treatment that was planted to received the recommended fertilization amount (60 and 90 kg ha-1 of K2O for planting and broadcasting, respectively). For the millet, was evaluated plant height, green and dry biomass yields, and soil cover at 30, 60, 90 and 120 days after harvest . For maize, agronomic traits, leaf nutrient content and green and dry biomass yields were evaluated. The early application of K fertilizer did not alter the yield components of millet and silage maize. However, the straw produced by the millet was efficient at promoting soil cover in the off-season.
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