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Abstract(s)
A cultura do castanheiro (Castanea sativa Mill.) apresenta grande importância econômica na região Norte de Portugal. A redução da produção nos principais países produtores, devido a problemas fitossanitários, tem impulsionado os preços da castanha e estimulado os produtores a fertilizarem os seus pomares. Neste cenário, empresas de fertilizantes estão propondo soluções de fertilização aos produtores sem devido respaldo da investigação. O objetivo do estudo foi avaliar o efeito da aplicação de fertilizantes comerciais com mecanismos de liberação gradual de nutrientes propostos por uma empresa para a cultura do castanheiro. Foram conduzidos ensaios em dois locais no distrito de Bragança, com delineamento experimental em blocos casualizados e três repetições. Os tratamentos fertilizantes utilizados foram: orgânico de origem vegetal (13:03:05); organo-mineral de longa duração (06:15:08); organo-mineral com ácidos húmicos e fúlvicos (05:14:07); mineral de liberação controlada (18:05:13); e controle sem fertilização. Foram aplicados 3 kg de fertilizante por árvore nos anos 2015, 2016 e 2017 no mês de fevereiro. Avaliou-se o estado nutricional das árvores (mês de julho) e a produtividade em 2015, 2016 e 2017. As características químicas do solo e a atividade da fosfatase ácida foram avaliadas em amostras de solo coletadas em 3 profundidades (0-10 cm, 10-20 cm, e 20-30 cm) após três anos de aplicação dos fertilizantes. O adubo orgânico de origem vegetal (13:03:05) estimulou a atividade da fosfatase ácida na camada 0-10 cm. O estado nutricional das árvores comparado com o limite inferior do intervalo de suficiência, demonstrou que os elementos N e B foram os mais limitantes à cultura do castanheiro. Em rigor, não houve efeito dos fertilizantes sobre a produção acumulada de castanha, uma vez que as diferenças não tiveram significado estatístico, atribuído a elevada variabilidade experimental. No entanto, todos os fertilizantes começaram a destacar-se do controle sem fertilização. Os resultados das características químicas do solo foram pouco relevantes. O estado nutricional e produtividade das árvores indicam que o fertilizante mineral (18:05:13) de liberação controlada revestido por polímeros apresentou tendência de ser o mais adequado à cultura do castanheiro, possivelmente por ser mais concentrado nos elementos mais limitantes detectados pelas análises foliares. Os mecanismos de liberação gradual dos nutrientes não exerceram um efeito relevante no estado nutricional e na produtividade do castanheiro.
Chestnut tree (Castanea sativa Mill.) plays an importante role in the economy of the Northern region of Portugal. The reduction of production in the main producing countries due to phytosanitary problems has increased the prices of the nuts and stimulated the producers to fertilize their orchards. Without previous studies on tree response to fertilization, fertilizer companies are proposing fertilizer solutions with poor research support. The aim of the study was to evaluate the effect of fertilizer with mechanisms of slow and controlled release of nutrients in chestnut orchards. Two experiments were conducted in the district of Bragança arranged as randomized complete block designs and three replicates. The fertilizer treatments were: organic of vegetal origin (13:03:05); controlled release, organo-mineral (06:15:08); organo-mineral with humic and fulvic acids (05:14:07); controlled release, mineral (18:05:13); and control without fertilization. Each fertilizer was aplied at the rate of 3 kg per tree in 2015, 2016 and 2017 by late in winter. The nutritional status of the trees and chestnut yields were assessed in 2015, 2016 and 2017. Several soil chemical properties, including acid phosphatase activity, were evaluated from soil samples collected at 3 depths (0-10 cm, 10-20 cm, and 20-30 cm) after three years of fertilizer application. The organic fertilizer of vegetable origin (13:03:05) stimulated the activity of acid phosphatase in the 0-10 cm layer. N and B were the elements that most limit the chestnut crop if they were compared to the sufficieny ranges established for this species. In fact, there was not found a significant effect of the fertilizer treatments on the accumulated chestnut yield, in spite of the huge differences among average values, as a result of the high experimental variability. The fertilizer treatments had a poor effect on the main soil properties. The nutritional status of the trees and chestnut yields indicate that the mineral (18:05:13) polymer-coated controlled-release fertilizer tended to be the most adequate for these chestnut orchards, possibly because it is more concentrated in the more limiting elements detected by foliar analysis. The mechanisms of slow and controlled release of nutrients did not have a relevant effect on the nutritional status and productivity of the chestnut tree.
Chestnut tree (Castanea sativa Mill.) plays an importante role in the economy of the Northern region of Portugal. The reduction of production in the main producing countries due to phytosanitary problems has increased the prices of the nuts and stimulated the producers to fertilize their orchards. Without previous studies on tree response to fertilization, fertilizer companies are proposing fertilizer solutions with poor research support. The aim of the study was to evaluate the effect of fertilizer with mechanisms of slow and controlled release of nutrients in chestnut orchards. Two experiments were conducted in the district of Bragança arranged as randomized complete block designs and three replicates. The fertilizer treatments were: organic of vegetal origin (13:03:05); controlled release, organo-mineral (06:15:08); organo-mineral with humic and fulvic acids (05:14:07); controlled release, mineral (18:05:13); and control without fertilization. Each fertilizer was aplied at the rate of 3 kg per tree in 2015, 2016 and 2017 by late in winter. The nutritional status of the trees and chestnut yields were assessed in 2015, 2016 and 2017. Several soil chemical properties, including acid phosphatase activity, were evaluated from soil samples collected at 3 depths (0-10 cm, 10-20 cm, and 20-30 cm) after three years of fertilizer application. The organic fertilizer of vegetable origin (13:03:05) stimulated the activity of acid phosphatase in the 0-10 cm layer. N and B were the elements that most limit the chestnut crop if they were compared to the sufficieny ranges established for this species. In fact, there was not found a significant effect of the fertilizer treatments on the accumulated chestnut yield, in spite of the huge differences among average values, as a result of the high experimental variability. The fertilizer treatments had a poor effect on the main soil properties. The nutritional status of the trees and chestnut yields indicate that the mineral (18:05:13) polymer-coated controlled-release fertilizer tended to be the most adequate for these chestnut orchards, possibly because it is more concentrated in the more limiting elements detected by foliar analysis. The mechanisms of slow and controlled release of nutrients did not have a relevant effect on the nutritional status and productivity of the chestnut tree.
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Keywords
Fertilizantes de liberação lenta Fertilizantes de liberação controlada Adubos orgânicos Fosfatase ácida Análise foliar Fertilidade do solo