Crescimento, teor e acúmulo de nutrientes em alface americana (Lactuca sativa L.) sob doses de nitrogênio aplicadas no solo e níveis de cálcio aplicados via foliar

Abstract

The objective ofthis trial was to evaluate the efíects ofleveis of soil-applied Nitrogen and foliar-sprayed Calcium on the yield components ofthe crisphead lettuce cultivar Ryder. The treatments were fectorial combinations of3 Nitrogen leveis (120, 180 and 240 kg/ha), 4 Calcium leveis (0.0, 0.5, 1.0 and 1.5% in solution) and 7 evaluation dates, used in a randomized complete block design with 4 replications. Nitrogen rate of 120 kg/ha was applied via drip fertirrigation in ali plots, and additional rates were applied via soil in the plots corresponding to the 180 kg/ha and 240 kg/ha total rate. Calcium was applied using a CO 2back-pack sprayer. Evaluations were made in plants sampled at 7- day intervals, starting 14 days after transplanting (d.a.t) and ending 56 d.a.t., totalizing to 7 evaluation dates. The field trial was located in "Refiicom Mercantil Ltda" Experimental Área, in city ofSanto Antônio do Amparo, State of Minas Gerais, Brazil. Foliar application ofCalcium had no effect on any macronutrient (Calcium included) uptake or content in the aerial part ofthe plant; foliar application ofCa was therefore consideredunnecessary. Nitrogen in the aerial parts decreased with increased leveis offoliar-sprayed Calcium, but remained within the range considered normal. Tipburn symptoms were not detected in any ofthe treatments, includingthose with no foliar Calcium applied. Significant treatment efíects and interactions were not considered important, because the traits evaluated remainedwithin the ranges considered normal for the crop. Macronutrientuptake was more intense in the period immediately prior to harvest. Copper leveis were not influencedby either N or Ca, but decreasedwith plant age; its accumulatíon was influenced by Ca x evaluation date interaction, and increased with increasing Ca leveis. Copper accumulatíon was lower than, but contents were within the normal range. Uptake and accumulatíon ofBoron was signifícantly afíected by ali sources ofvariation. Boron leveis in the aerial parts decreasedwith increasing Ca leveis. B content was considered normal, but was higher than those reported by other authors. The interaction N x Ca x evaluation date signifícantly afíected Zinc content, which decreased with increasing Ca leveis. Even though Zn leveis were considered to be within the normal range, they were much lower than those reported by other authors. Manganese contents were influenced by evaluation dates only, but Manganese evaluation date signifícantly afíected Zinc content, which decreased with increasing Ca leveis. Even though Zn leveis were considered to be within the normal range, they were much lower than those reported by other authors. Manganese contents were influenced by evaluation dates onry, but Manganese uptake was signifícantly afíected by ali sources ofvariation, and decreased with increasing Ca leveis; even thougfa Mn contents were considered normal, they were much lower than those reported by other authors. Uptake of ali micronutnents under study was concentrated in the latter phase of plant development There were significant 3-way interactions between N x Ca x evaluation date for both dry weigjit and fresh weigíit Ali NxCa combinations promoted normal plant development up to 42 d.a.1, after which períod some treatments promoted superior performance just before harvest Increasing Ca concentrations inthe solution reduced both fresh and dry matter weigfat Number ofleaves and dry matter content were afíected by evaluation dates and Ca leveis onry, and no interaction between sources ofvariation was observed.