CARBON AND NUTRIENT LOSSES THROUGH BIOMASS BURNING, AND LINKS WITH SOIL FERTILITY AND YAM (DIOSCOREA ALATA) PRODUCTION

Abstract

SUMMARYBiomass burning has links with a number of global concerns including soil health, food security and climate change. In central Côte d'Ivoire (West Africa), we conducted a field study to compare nutrient losses, soil fertility and yam yield in slash-and-burn versus slash-and-mulch agriculture. Trials involved five sites established in the dominant Chromolaena odorata fallows of the region, each consisting of paired plots: slash and burnt biomass (SB) versus slashed and unburnt biomass, but left to serve as mulch (SM). Carbon and five elemental nutrients were assessed in the aboveground biomass prior to burning and in ash after fires; losses were assessed by subtraction. The greatest proportions of loss occurred with C (95%), N (95%) and K (74%), corresponding to losses into the atmosphere of 3532 ± 408, 200 ± 36, 132 ± 36 kg ha−1. Six weeks after the fire, soil properties were assessed: soil organic C, total N and Mg2+ were higher in SM than in SB sites. At final harvest, yam tuber yield was twice as large in SM as in SB (18 ± 4 vs. 9 ± 2 Mg ha−1) with soil C, total N and K+ as the main influential soil parameters. The key finding was that the elements lost in greatest proportion during burning were those mostly influencing yam yields. Because a clear negative relationship between biomass burning and yam production has been established the promotion of the more productive, alternate slash-and-mulch system compared to slash-and-burn system, is warranted. The findings of our research can be used in support of developing a sustainable yam production system in the region and in West Africa more generally.

Emissions of non-methane volatile organic compounds from combustion of domestic fuels in Delhi, India

“…Nitrogen-containing NMVOCs are formed from the volatilisation and decomposition of nitrogen-containing compounds within the fuel, mainly from free amino acids but can also be from pyrroline, pyridine and chlorophyll (Leppalahti and Koljonen, 1995;Burling et al, 2010;Ren and Zhao, 2015). Nitrogen-containing NMVOCs are of interest because nitrogen may be important in the development of new particles (Smith et al, 2008;Kirkby et al, 2011;Yu and Luo, 2014), which act as cloud condensation nuclei (Kerminen et al, 2005;Laaksonen et al, 2005;Sotiropoulou et al, 2006) and alter the hydrological cycle by forming new clouds and precipitation (Novakov and Penner, 1993). They can also contribute to light-absorbing brown carbon (BrC) aerosol formation, effecting climate (Laskin et al, 2015).…”

“…A wide range of trace gases are released from biomass burning, in different amounts depending on the fuel type and the combustion conditions, meaning that detailed studies at the point of emission are required to accurately characterise emissions. The gases released lead to soil-nutrient redistribution (Ponette-Gonzalez et al, 2016;N'Dri et al, 2019); can themselves be toxic (Naeher et al, 2007); and can significantly degrade local, regional, and global air quality through the photochemical formation of secondary pollutants such as ozone (O 3 ) (Pfister et al, 2008;Jaffe and Wigder, 2012) and secondary organic aerosol (SOA) (Alvarado et al, 2015;Kroll and Seinfeld, 2008). They can also lead to indoor air quality issues (Fullerton et al, 2008).…”

Effect of fire regimes on the demographic parameters of the perennial tussock grasses of a humid savanna

“…According to them, the late fire should rather stimulate tussock growth by reducing aboveground biomass, subsequently reducing competition and increasing light availability (Zimmermann et al., ). The stronger negative impact of the late fire, which does not have a higher intensity than the other fire regimes in Lamto savanna (N'Dri, Kone, Loukou, Barot, & Gignoux, ; N'Dri, Soro, et al., ), is likely explained by the fact that grass tussocks have resumed their growth at the moment of late fire, so that late fire has a stronger negative impact on growth (and other demographic parameters, see above).…”

“…More seeds per tussock were produced in the no fire than in the early and mid‐season fire treatments. This could be due to the return of more dead biomass and mineral nutrients to the soil in the absence of fire, because fires lead to the loss of the aboveground biomass and an important fraction of the mineral nutrients it contains (N'Dri, Kone, Loukou, Barot, & Gignoux, ). This is in agreement with Crowley and Garnett ().…”

“…Three separate blocks of 3.72 ha each were identified in the shrubby savanna zone. In each block, four plots were established in September 2013 to implement four fire treatments (N'Dri, Kone, Loukou, Barot, & Gignoux, ; N'Dri, Soro, et al., ): early fire (in November), mid‐season fire (in January), late fire (in March) and no fire (unburned plot). In each of these plots, a plot was delimited to monitor grass demography.…”