Gradual correction of phosphorus availability in the no-tillage system

Abstract

Em áreas cultivadas no Sistema Plantio Direto, pode-se elevar a disponibilidade de fósforo por meio da adubação corretiva gradual, aplicando-se, no sulco de semeadura, quantidade de P superior à requerida pela cultura. Este trabalho foi realizado com o objetivo de se estabelecer a quantidade de P a ser aplicada no cultivo de soja, visando a elevação do teor de P para valores pré-estabelecidos, na camada de 0 a 0,10 m de profundidade. Conduziu-se um experimento em Latossolo Vermelho distroférrico típico, textura muito argilosa, com delineamento experimental de blocos ao acaso, distribuído em parcelas sub-subdivididas, com quatro repetições. Foram avaliadas duas formas de cultivo de soja (solteiro e consorciado com Panicum maximum cv. Aruana) nas parcelas; quatro doses de P (0, 60, 120 e 180 kg ha -1 de P 2 O 5 ) aplicadas no primeiro ano, nas subparcelas; e quatro doses de P (0, 30, 60 e 90 kg ha -1 de P 2 O 5 ) aplicadas em dois cultivos subsequentes, nas sub-subparcelas. Efetuou-se a extração dos teores de P por Mehlich-1 e Resina de Troca Aniônica em amostras de solo coletadas nas sub-subparcelas. Verificou-se que há necessidade da aplicação de 19,4 ou 11,1 kg ha -1 de P 2 O 5 na semeadura da soja, usando-se superfosfato triplo como fonte, para a elevação de 1 mg dm -3 de P extraído por Mehlich-1 ou Resina, respectivamente, na camada de 0,0 a 0,10 m de profundidade. Há diminuição do caráter dreno de P do solo, a medida em que se aumenta a quantidade do nutriente fornecida no cultivo anterior. Palavras ABSTRACTIn areas cultivated under no-tillage system, the availability of phosphorus (P) can be raised by means of the gradual corrective fertilization, applying phosphorus into sowing furrows at doses higher than those required by the crops. The objective of this work was to establish the amount of P to be applied in soybean crop to increase content of P to preestablished values at the depth of 0.0 to 0.10 m. An experiment was carried out on a clayey Haplorthox soil with a randomized block experimental design distributed in split-split plot, with four replications. Two soybean crop systems (single or intercropped with Panicum maximum Jacq cv. Aruana) were evaluated in the plots. In addition, it was evaluated four P levels (0, 60, 120 and 180 kg ha -1 P 2 O 5 ) applied in the first year in the split plots; and four P levels (0, 30, 60 and 90 kg ha -1 P 2 O 5 ) applied in the two subsequent crops in the split-split plot. Contents of P were extracted by Mehlich-1 and Anion Exchange Resin methods from soil samples collected in the split-split plot. It was found that it is necessary to apply 19.4 or 11.1 kg ha -1 of P 2 O 5 , via triple superphosphate as source, to increase 1 mg dm -3 of P extracted by Mehlich-1 or Resin, respectively, in the 0.0 to 0.10 m layer of depth. The soil drain P character decreases as the amount of this nutrient supplied in the previous crops is increased.

Distribution of Soil Phosphorus Fractions as a Function of Long-Term Soil Tillage and Phosphate Fertilization Management

“…Brazilian Cerrado (savanna) soils originally present low phosphorus (P) availability for cropping, making the addition of phosphate fertilizers mandatory, firstly to build up P availability to acceptable levels before cropping and secondly to maintain the available levels during subsequent growing seasons, through periodic fertilization to replace the P exported by harvesting (Kurihara et al, 2016). The reason is that Cerrado soils have a high solid phase P retention capacity, due to their high Fe and Al sesquioxide constitution, capable of retaining phosphate ions in less labile forms (Fink et al, 2014(Fink et al, , 2016a.…”