Crescimento, produtividade e nitrato em frutos de pepino submetidos a fontes de adubos nitrogenados

Abstract

Há carência de informações sobre a utilização de fontes de fertilizantes nitrogenados na cultura do pepino. Embora fundamental para a obtenção de elevada produtividade, o N pode promover acúmulo de nitrato nas porções comestíveis que, reduzido a nitrito, se constitui em fator de risco à saúde humana. O trabalho teve como objetivo avaliar o efeito de fontes de N sobre o crescimento da planta, concentração e fluorescência da clorofila, produção e acúmulo de nitrato em frutos de pepino. O experimento foi conduzido em casa de vegetação, em vasos de 10 L preenchidos com solo. As fontes de N foram: 1-sulfato de amônio (100% amoniacal); 2-nitrato de amônio (50% amoniacal e 50% nítrica); 3-nitrato de sódio (100% nítrica) e 4ureia (100% amídica). Foi utilizada a dose de 160 mg de N kg-1 de solo, para todas as fontes. Esse total foi parcelado em oito aplicações semanais, iniciando uma semana após o transplante das mudas. Não houve diferença significativa entre fontes de N para todas as características avaliadas. Todas as fontes apresentaram a mesma eficiência quanto a produção de frutos e baixo acúmulo de nitrato nos frutos (0,193 mg kg-1 de matéria fresca). Conclui-se que, para a cultura do pepino, o produtor deve utilizar a fonte de adubo nitrogenado que apresentar menor custo por kg de N que, no caso, foi a uréia. Palavras-chave: Cucumis sativus; nutrição nitrogenada; produção; teor de nitrato Growth, yield and nitrate accumulation in fruits of cucumber fertilized with sources of nitrogen fertilizers

N Sources and Doses on Japonese Cucumber Yield and Nitrate Accumulation in Fruits in Greenhouse

“…The appropriate N dose is variable according to several factors, including the expected yield, cultivar, management practices and soil and climate conditions (Pôrto et al, 2012b). Another aspect that should be considered in the management of N fertilization to crops is related to N source used, because it influences the uptake and metabolism of N by plants, there is a need to determine the best N source as a function of the plant species and the quality of the product to be used in the human consumption (Silva et al, 2017). The N source used plays an important role in regulating N transformations, changing N loss patterns and influencing N use efficiency by plants (Abbasi et al, 2013).…”

“…The N source used plays an important role in regulating N transformations, changing N loss patterns and influencing N use efficiency by plants (Abbasi et al, 2013). In general, the N fertilizer sources have one of the following N forms: amide (CO(NH 2 ) 2 ), ammonium (NH 4 + ) and nitrate (NO 3 -), being the N-amide and N-ammoniacal sources the most used in agricultural crops in the world (Silva et al, 2017). NO 3 is the main form of N uptaken by plants, but they can also uptake this nutrient in the form of NH 4 + or both.…”

“…NO 3 is the main form of N uptaken by plants, but they can also uptake this nutrient in the form of NH 4 + or both. The most crops grow best with a mixture of NO 3 and NH 4 + sources, although many studies present inconsistent responses (Abbasi et al, 2013;Silva et al, 2017). Currently, information on the use of N sources and the definition of adequate N dose for the Japanese cucumber cultivated in greenhouses are very scarce in the literature for the Brazilian conditions, being this definition of extreme importance to contribute to a better exploitation of the productive potential of the crop in this cultivation system.…”

“…Despite the importance of N fertilization for the vegetables yield, this practice is currently a controversial issue, because when applied in excess can result in the reduction of nutritional quality and security due to the NO 3 accumulation (Pôrto et al, 2012b(Pôrto et al, , 2014b. NO 3 when ingested in large amounts by humans can cause serious health consequences, such as formation of nitrosamines, a potentially carcinogenic substance, as well as methemoglobinemia or blue blood that reduces the oxygen transportation in the blood (Santamaria, 2006;Pôrto et al, 2012a;Silva et al, 2017).…”

“…In general, leafy vegetables such as lettuce, spinach, cabbage, arugula, among others, have tendency to accumulate high NO 3 concentration in their leaves (Pôrto et al, 2008;Ohse et al, 2012), existing a great interest in monitoring the NO 3 concentration in these plants. Flower and fruit vegetables, such as cauliflower, tomato, squash, zucchini, usually show less tendency to NO 3 accumulation (Santamaria, 2006;Pôrto et al, 2014b, Silva et al, 2017. Concerning Japanese cucumber crop, information on the NO 3 accumulation in the fruits, as well the influence of N sources and doses on this accumulation, is very scarce in the literature, especially in greenhouse conditions.…”