Potential for biological denitrification of fertilizer nitrogen in sugarcane soils

Abstract

Nitrogen (N) fertilizer is being lost from sugarcane soils following application to the crop. This study was conducted to estimate the quantity of N being lost from the soil through biological denitrification and to determine the proportion of gaseous N being emitted either as N2O or as N2. Field studies were conducted on four different soils (humic gley, alluvial massive earth, red earth and gleyed podzolic), and on different crop management systems, by installing plastic (PVC) cylinders (23.5 cm diam., 25 cm long) in the soil to a depth of 20 cm beside the plant row in a ratoon sugarcane crop. 15N-labelled KNO3 was applied as a band across each cylinder to a depth of 2.5 cm at a rate of 160 kg N/ha. After rainfall or irrigation, the cylinders were capped for 3 h intervals and gas in the headspace sampled in the morning and afternoon, for up to 4 days. Denitrification losses from the humic gley ranged from 247 g N/ha.day for cultivated plots to 1673 g N/ha.day for no-till plots. Over the sampling period, this was equivalent to 3.2% and 19.7% of the N applied, respectively. Nitrous oxide accounted for 46% to 78% of the total N lost. For the alluvial, massive earth and the red earth and gleyed podzolic, losses over the sampling period ranged from 25 to 117 g N/h.day and represented <1% of the N applied. Recovery of 15N in the soil ranged from 67% at the first sampling on the red earth soil to 4.9% at the third sampling on the alluvial, massive earth soil. In a glasshouse study, intact soil cores (23.5 cm diam., 20 cm long), taken from the humic gley and the alluvial, massive earth, were waterlogged after band application of 15N-labelled KNO3 at a rate of 160 kg N/ha. Gas samples from the headspace were taken after 3 h, and then morning and afternoon for the next 14 days. Denitrification losses ranged from 13.2 to 38.6% of N applied with the majority of gaseous N loss occurring as N2. Total recoveries after 14 days, including the evolved gases, ranged from 68.7 to 88.2%. We conclude that denitrification is a major cause of fertilizer N loss from fine-textured soils, with nitrous oxide the major gaseous N product when soil nitrate concentrations are high.

Processos hidrológicos e transporte de nitrogênio e carbono em bacias hidrográficas com cobertura de cana-de-açúcar

“…Quanto à saída de N de um agroecossistema, esta pode ocorrer via volatilização do fertilizante (FRENEY et al, 1981;, desnitrificação (WEIER et al, 2006;THORBURN et al, 2003), emissões de gases devido à queima (KAUFFMAN et al, 1995(KAUFFMAN et al, ,1998, pelo deflúvio da bacia (MORENO et al, 1996;BIGGS et al, 2004;DAVIDSON et al, 2004) e pela colheita do produto (CORDOVA et al, 2006). No presente trabalho foi determinada a saída de N apenas pelo deflúvio, adicionalmente, Salemi (2012) mediu a saída de N-N 2 O (desnitrificação) para as áreas de estudo.…”

Soil active carbon as an indicator of nitrous oxide loss potential

“…A later study by Weier (1996) also highlighted the significant influence of structure and texture on the magnitude of N losses from denitrification in sugarcane soils.…”

“…The Childers soil, with the highest percentage clay content (73%), also displayed small denitrification losses, due to the structure of the soil being composed of large particles of colloidal iron and aluminium oxi des. The degree of aggregation of soil particles resulted in the soil being well drained and therefore denitrification losses were small (Weier et al 1996).…”

“…A model proposed by Davidson (1991) suggested that N 2 O emissions should peak at 60% WFPS under soil moisture conditions which favour both nitrification and denitrification. A later model developed by Bouwman (1998) The relationship between increased soil moisture and higher rates of denitrification is well documented in laboratory incubation experiments (Mcgarity 1961;Linn & Doran 1984;Weier et al 1993;Weier et al 1996;Abbasi & Adams 2000;Azam et al 2002;Pihlatie et al 2004;Bateman & Baggs 2005;Ruser et al 2006;Liu et al 2007;Sánchez-Martín et al 2008;Van Zwieten et al 2010) and numerous field studies have shown WFPS to be a good predictor of N 2 O production in tropical soils (Davidson et al 2000). However, whilst it is clear that denitrification increases with higher levels of soil moisture, there is a lack of consensus regarding the WFPS l evel which is optimal for the production of N 2 O.…”

“…In addition to soil moisture, texture and substrate availability play an important role in both regulating denitrification rates and on the ratio of the final products (N 2 O:N 2 ). Previous research has demonstrated the significant impact texture has on the magnitude of denitrification losses (Weier et al 1996). Texture influences water holding capacity and gas diffusivity, or the transport of NO, N 2 O and N 2 out of soil (Davidson et al 2000).…”