Cerrado soils generally have low levels of exchangeable bases and high aluminum toxicity. These conditions can limit crop development. In view of the expansion of sugarcane cultivation in the Cerrado region, technologies that allow higher yields are required. Therefore, the objective of this study was to evaluate the influence of gypsum on sugarcane yield and soil chemical properties. The experiment was carried out in a randomized block design with four replications and two treatments: control without gypsum (0 Mg ha -1 ) and application of the recommended dose (5 Mg ha -1 ) for sugarcane. Cane and sugar yield were evaluated in four cuts. Seven soil layers (0-5; 5-10; 10-20; 20-40; 40-60; 60-80, and 80-100 cm) were sampled after harvesting the third ratoon crop, 50 months after gypsum application, to determine pH in H 2 O and CaCl 2 ; aluminum (Al , Mg 2+ and SO 4 2-levels and lower aluminum saturation in the 20-100, 40-100, 0-100, and 40-100 cm layers, respectively. In addition, the application of gypsum provided an increase in cation exchange capacity in the 40-100 cm layer. Therefore, gypsum application is recommended to improve the chemical conditions of the soil and to increase sugarcane productivity in the Cerrado.

Gypsum is widely used in agriculture in the Cerrado region of Brazil to increase root volume and distribution in the profile of predominantly acidic soils with high aluminium toxicity. The gypsum-induced increase in the root system may be an effective strategy to increase sequestration of atmospheric CO2. However, few studies have investigated the relationship between the use of gypsum and carbon accumulation in the soil under sugar cane. In the present study, total carbon stock (TC) in the soil and its fractions were estimated after four growing seasons of sugar cane under gypsum application. The experiment was arranged in a randomised block design with four replicates and two treatments: control (0Mgha–1) and the technically recommended rate of gypsum application (5Mgha–1). Sugarcane stalk biomass and straw production were evaluated in plant cane and three ratoon crops. Soil samples were taken after evaluation of the third ratoon from seven layers (0–5, 5–10, 10–20, 20–40, 40–60, 60–80 and 80–100cm) to determine organic carbon, TC, particulate carbon (PC) and bulk density. Gypsum increased TC by 5.4 and 4.4Mgha–1 in the 0–100 and 40–100cm layers respectively. The PC pool in the 40–100cm layer was increased by 18.4%, whereas the carbon stock associated with mineral increased by 6.8% with gypsum application. Of the total increase in C stocks resulting from gypsum application, 80% occurred in the 40–100cm layer.

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Phosphorus fertilization and irrigation management are essential practices to increase coffee yields, though information is scarce about the effect of these practices on organic matter fractions of soils of the ‘Cerrado’ (savanna-like vegetation). The purpose of this study was to evaluate organic matter fractions of a clayey Oxisol under coffee with split applications of phosphorus (P) and water regimes. The experimental design was a randomized block with 3 x 2 factorial arrangement with three split applications of P (P1: 300 kg ha-1 P2O5 applied annually of which 2/3 applied in September and 1/3 in December; P2: 600 kg ha-1 P2O5 applied at planting and every two years, and P3: 1800 kg ha-1 of P2O5 applied only at planting, corresponding to a 6-year requirement), two water regimes (with and without irrigation) and three replications. Soil from the 0-5 and 5-10 cm layers was sampled. The total organic carbon (TOC), labile carbon (LC), microbial carbon (Cmic), and carbon fractions of fulvic acid (FA), humic acid (HA) and humin (HU) were determined. The irrigation regime of coffee increased the TOC, LC and Cmic levels and the humified fractions of soil organic matter. In general, the form of P splitting had little influence on the fractions of soil organic matter.

RESUMO: A classificação pedológica e a sua relação com a geologia e geomorfologia em estudos de topossequência são essenciais para a compreensão do processo evolutivo e distribuição espacial das classes de solo na paisagem. O presente trabalho objetivou estudar as relações solo-paisagem em uma topossequência no Distrito Federal, Centro-Oeste do Brasil. Para isso, o método de prospecção adotado foi o estudo das topossequências. Na área avaliada foram verificadas três superfícies geomorfológicas (SG): SG1-Chapadas Elevadas, SG2-Planos Intermediários e Rebordos, e SG3-Planícies. Foram abertas cinco trincheiras em topossequência e realizou-se descrição morfológica e procedeu a classificação segundo o Sistema Brasileiro de Classificação de Solos (SiBCS). Amostras indeformadas foram coletadas para realizar análises físicas, tais como: textura, umidade na base de volume (θ), umidade gravimétrica (U), densidade do solo (Ds), densidade de partículas (Dp), argila dispersa em água (ADA), porosidade total (Pt) e grau de floculação (GF); e químicas, que foram utilizadas as amostras soltas de solo coletadas no campo. Determinou-se: o pH em H 2 O e KCl, Ca +2 + Mg +2 e Al +3 , K + , H + Al e o P 2 O 5 , matéria orgânica do solo (MOS) e o carbono orgânico total (COT), Com os resultados das análises químicas e descrição física e morfológica, foi possível classificar os solos conforme o SiBCS. Os tipos de solos encontrados na topossequência da Fazenda Água Limpa foram:

Although the benefits of gypsum for subsoil conditioning are known, there is still a lack of information regarding the duration of its effects on soil chemical attributes and sugarcane productivity. Therefore, the objective of this work was to evaluate the residual effect of gypsum doses on soil chemical attributes, root density and productivity in seven sugarcane crops (ratoon). The experiment was conducted in an experimental area located at Embrapa Cerrados, in Planaltina, DF, Brazil. The experimental design consisted of four gypsum doses (0, 0.5, 5 and 10 t ha-1) distributed in randomized blocks with four replications. Gypsum was applied only one time to the soil surface after sugarcane planting in July 2009. After 13 and 87 months of gypsum application under sugarcane cultivation, the soil was collected from layers up to 120 and 200 cm deep, respectively. For evaluation of the soil chemical attributes: sulfate (S-SO 4 2-), calcium (Ca 2+), magnesium (Mg 2+) and aluminum saturation (m) were assessed. Also, the root dry mass density was evaluated after the first and seventh sugarcane crops, in September 2010 and 2016, respectively. Furthermore, the variables leaf macronutrient concentrations (N, P, K, S, Ca and Mg), stalk yield and total reducing sugars (TRS) were analyzed in all seven crops/ratoons (first is the main crop and other six are ratoons). The application of 5 t ha-1 gypsum increased SO 4 2and Ca 2+ and reduced the aluminum saturation after 13 and 87 months, with higher intensities in the subsurface layers of the soil. As a consequence of this chemical conditioning of the subsurface soil layers, the root dry mass density was increased by 18 and 37% in the 0-120 and 0-200 layers, respectively, after the first (main) and seventh sugarcane crops (ratoons) in relation to the absence of gypsum application. Furthermore, treatments with 5 and 10 t ha-1 of gypsum increased the leaf contents of S, Ca and N in relation to treatments with 0 and 0.5 t ha-1 of gypsum. As a consequence of the increased root growth and better nutrition of sugarcane, the use of gypsum provided a long residual effect, observed in the increase of stalk and sugar yields.