Phosphate fertilization and phosphorus forms in an Oxisol under no-till

Abstract

Under no-till phosphorus (P) accumulates in a few centimeters of the topsoil layer. Plant residues left on the soil surface release P and organic acids, which may improve P availability and fertilizer efficiency, including both soluble (such as triple super phosphate) and less soluble sources (such as reactive natural phosphates). In this study, soybean response to P fertilizer and P forms in the top 40 cm of an Oxisol were evaluated after surface application of different phosphates in a 5-year-old no-till system. Treatments consisted of 0 or 80 kg ha -1 of total P 2 O 5 applied on the soil surface, both as natural reactive phosphate (NRP) or triple super phosphate (TSP). In addition, 80 kg ha -1 of P 2 O 5 were applied to subplots, in furrows below and beside the soybean (Glycine max L.) seeds, in different combinations of NRP and TSP. Soil samples were taken before and after the soybean growth, down to 0.40 m and soil phosphorus was chemically fractionated. The responses to NRP were similar to TSP, with an increase in P reserves at greater depths, even in non-available forms, such as P-occluded. After the soybean harvest, P-occluded levels were lower at the surface layer, but an increase was observed in the soluble, organic and total P down to 40 cm. An improved P distribution in soil depth, especially regarding the soluble and organic forms, resulted in higher soybean yields, even when the phosphates were applied to the soil surface. Key words: reactive phosphate, superphosphate, phosphorus fractions, conservation tillageAdubação fosfatada e formas de fósforo num Latossolo sob sistema de semeadura direta RESUMO: Em semeadura direta o fósforo (P) acumula-se na camada mais superficial do solo, mas os resíduos deixados na superfície liberam P e ácidos orgânicos, que podem melhorar a disponibilidade e a eficiência de fertilizantes como o superfosfato triplo e fosfatos naturais reativos. Neste estudo, a resposta da soja à adubação com P e as formas de P até 40 cm de profundidade do solo foram avaliadas após a aplicação de fosfatos em um sistema conduzido em semeadura direta há cinco anos. Os tratamentos consistiram de 0 ou 80 kg ha -1 P 2 O 5 total, aplicados na superfície do solo como fosfato natural reativo (FNR) ou superfosfato triplo (SFT). Nas subparcelas foram aplicados, no sulco de semeadura, 80 kg ha -1 de P 2 O 5 , em diferentes combinações de FNR e SFT. Amostras de solo foram coletadas até 0.4 m, antes e depois do cultivo da soja (Glycine max L.), para fracionamento do P. As respostas ao FNR foram semelhantes às do SFT, com aumento das reservas de P em profundidade, mesmo em formas não-disponíveis como P-ocluso. Após a colheita da soja, os teores de P-ocluso diminuíram na camada mais superficial, mas foi observado um aumento nas formas solúvel, orgânica e P -total em toda a espessura de solo estudada. A melhor distribuição do P no solo, principalmente em formas solúvel e orgânica, resultou em maior produtividade da soja, mesmo quando o fertilizante foi aplicado na superfície do solo. Palavras-c...

Phosphorus fractions and correlation with soil attributes in a chronosequence of agricultural under no-tillage

“…This may also be related to decomposition of the different root systems of the adopted crops during NT establishment. Olibone and Rosolem (2010) analyzed different P fractions following phosphate application to soya crops in a system incorporating five years of NT, and also observed increased Po concentrations following the soya harvest. The authors related this to root decomposition.…”

“…Some studies have investigated P fractionation in highly weathered soils under NT (SILVA et al, 2003;GALVANI et al, 2008;OLIBONE;ROSOLEM, 2010;CARNEIRO et al, 2011;BEUTLER, 2012). However, the results are conflicting.…”

“…However, the results are conflicting. Studies of the effect of different P sources, and modes of application in NT areas, have observed that P application (independent of the source and mode of application) increased soil Po concentrations (GALVANI et al, 2008;OLIBONE;ROSOLEM, 2010). However, when soils under NT and native Cerrado were compared, P fertilization was observed to result in decreased Po and increased Pi concentrations in NT areas when compared to untreated soils from Cerrado (SILVA et al, 2003;CARNEIRO et al, 2011;BEUTLER, 2012;RODRIGUES, 2013).…”

Influence of Phosphorus Application With Avail on Following Soybeans in Southeastern Coastal Plains

“…Phosphorus in plant residues from previous crop may be utilized by following crops (Noack et al, 2012). Under no-till system, P released from plant residues and concentrated in the soil surface helps to improve nutrient availability of following crops (Olibone and Rosolem, 2010). Hassan et al (2012) noted that P uptake improved in cereal crops following legumes.…”

Soil phosphorus dynamics as affected by Congo grass and P fertilizer

“…Inorganic phosphorus (P) in the soil occurs mainly as H 2 PO 4 -and HPO 4 2-adsorbed to the surface of oxides and hydroxides and to organic matter or bound to Ca (Olibone and Rosolem, 2010), depending on acidity and minerals in the clay (Duputel et al, 2013). Hence, soils can be considered a source or sink for phosphorus depending on their characteristics (Pavinato et al, 2009).…”