Nitrogen dynamics in a soil-sugar cane system

Nitrogen (N) leaching below the crop-rooting zone represents not only a valuable loss of nutrients for the plant, but also a potential pollution source of groundwater. The objective of this work was to quantify leaching losses of native N and that derived from fertilizer in an Oxisol that was cultivated with sugarcane (Saccharum officinarum) during the crop plant cycle. The sugarcane was planted and fertilized with urea in the planting furrow, with 120 kg ha -1 of N. In order to determine the fate of the fertilizer -N, four microplots with 15 N enriched fertilizer were installed. Input and output of N at the depth of 0.9 m were quantified from the flux density of water and the N concentration in soil solution. During the evaluation period the rainfall was 141 mm less than the historical average (1,315 mm), and the climate was drier than normal in January. The average concentration of mineral N in soil solution was 1.8 mg L -1 . The abundance of 15 N was very high at the beginning (first week) of the assessment period and remained approximately constant (0.453 atom% of 15 N) until the end of the period. The internal drainage was 91 mm of water and the N leaching loss was 1.1 kg ha -1 of N, with only 54 g ha -1 derived from fertilizer. Therefore, under high demand of N by the crop in a system without burning before planting, the leaching of N was not considerable, mainly because the surplus of water between the months of December and March was lower than expected and also because the extraction of nitrogen by the crop was high. Key words: Saccharum spp., sustainability, solute transport, environmental quality, pollution Nitrogênio lixiviado num Latossolo cultivado com cana-de-açúcarRESUMO: A lixiviação de nitrogênio (N) abaixo da zona radicular representa uma valiosa perda do nutriente para as plantas e uma fonte potencial de poluição do lençol freático. Quantificaram-se as perdas de N por lixiviação num Latossolo Vermelho Amarelo cultivado com cana-de-açúcar (Saccharum officinarum) durante o ciclo agrícola de cana-planta. A cultura foi implantada e fertilizada no sulco com 120 kg ha -1 de N-uréia. Para conhecer o destino do fertilizante, foram instaladas quatro microparcelas onde o fertilizante era marcado com o isótopo 15 N. As entradas e saídas de N a 0,9 m de profundidade foram quantificadas diariamente pela densidade de fluxo de água e a concentração de N da solução no solo. No período de avaliação, a precipitação pluvial foi 141 mm menor que a média histórica (1.315 mm) sendo janeiro mais seco que o normal. A concentração de N mineral média foi 1,8 mg L -1 . A abundância de 15 N foi superior à abundância natural do isótopo, especialmente no início do período de avaliação, permanecendo logo constante (0,453% de 15 N). A drenagem interna foi de 91 mm de água e a perda por lixiviação foi 1,1 kg ha -1 de N com apenas 54 g ha -1 derivados do fertilizante. Portanto, com elevada demanda de nutrientes e elevada incorporação de restos culturais, não foram registradas perdas apreciáveis de N por lixiviação d...

Section: Resultssupporting

confidence: 76%

Nitrogen fertilizer leaching in an Oxisol cultivated with sugarcane

Ghiberto¹,

Libardi

Brito

et al. 2011

“…Total available nitrogen in soil after harvesting eucalyptus is five times higher than the total nitrogen derived from natural process such as litterfall decomposition (Câmara et al, 2000). Sugar cane crops in Brazil are fertilized with nitrogen in rates from 60 to 120 kg N ha -1 , from different fertilizers sources, depending on the region and economic aspects (Oliveira et al, 2000). Thus, the application of nitrogen based fertilizer could favor an increase of the net mineralization and nitrification rates, enhancing the nitrate concentration in the streamwater, as observed in the data here collected.…”

Section: Resultsmentioning

confidence: 69%

“…The change of natural vegetation in the Brazilian cerrado for agricultural use is associated to the increasing production of grain crops, sugar cane and eucalyptus (Klink & Machado, 2005). Among this, sugar cane is one of the most important agricultural commodities in Brazil and covers 5 million hectares, 50% of them located in the state of São Paulo (Oliveira et al, 2000). On top of this, the intense displacement of the cerrado natural vegetation by forestry activities has called attention of the general public, increasing pressure over paper and cellulose companies concerning the impacts on water resources (Espirito Santo, 1995;Vital et al, 1999;Câmara et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

Can land use changes alter carbon, nitrogen and major ion transport in subtropical brazilian streams?

Silva

Ometto

Lobo

et al. 2007

Several studies in tropical watersheds have evaluated the impact of urbanization and agricultural practices on water quality. In Brazil, savannas (known regionally as Cerrados) represent 23% of the country's surface, representing an important share to the national primary growth product, especially due to intense agriculture. The purpose of this study is to present a comprehensive evaluation, on a yearly basis, of carbon, nitrogen and major ion fluxes in streams crossing areas under different land use (natural vegetation, sugar cane and eucalyptus) in a savanna region of SE Brazil. Eucalyptus and sugar cane alter the transport of the investigated elements in small watersheds. The highest concentration of all parameters (abiotic parameters, ions, dissolved organic carbon -DOC -and dissolved inorganic carbon -DIC) were found in Sugar Cane Watersheds (SCW). The observed concentrations of major cations in Eucalyptus Watersheds (EW) (Mg, Ca, K, Na), as well as DIN and DOC, were found frequently to be intermediate values between those of Savanna Watersheds (SW) and SCW, suggesting a moderate impact of eucalyptus plantations on the streamwater. Same trends were found in relation to ion and nutrient fluxes, where the higher values corresponded to SCW. It is suggested that sugar cane plantations might be playing an important role in altering the chemistry of water bodies.

“…The main fate of N fertilizer (about 20 to 40 %) applied to sugarcane is to remain in the soil, where the N immobilized by microorganisms resides in the organic fraction and is temporarily unavailable to the crop (Gava et al, 2005;Oliveira et al, 2000). N Fertilizer is also subject to loss through leaching, denitrification or NH 3 volatilization, which can occur from senescing plant leaves as well as from soils amended with alkalizing fertilizers.…”

Section: Discussionmentioning

confidence: 99%

Residual recovery and yield performance of nitrogen fertilizer applied at sugarcane planting

Franco¹,

Otto

Vitti

et al. 2015

The low effectiveness of nitrogen fertilizer (N) is a substantial concern that threatens global sugarcane production. The aim of the research reported in this paper was to assess the residual effect of N-fertilizer applied at sugarcane planting over four crop seasons in relation to sugarcane crop yield. Toward this end three field experiments were established in the state content at the other, whereas the only residual effect was higher sucrose content in one of the following ratoons. The combined effect was an increase in sugar yield for three of the 11 crop seasons evaluated. Over the crop cycle of a plant cane and three ratoon crops, only 35 % of the applied N was recovered, split 75, 13, 7 and 5 % in the plant cane, first, second and third ratoons, respectively. These findings document the low efficiency of N recovery by sugarcane, which increases the risk that excessive N fertilization will reduce profitability and have an adverse effect on the environment.