Soil respiration in Amazonian plantations treated with charcoal, and mineral or organic fertilisers
Christoph Steiner, Murilo Rodrigues de Arruda, Wenceslau G. Teixeira, and Wolfgang Zech. 2008. Soil respiration curves as soil fertility indicators in perennial central Amazonian plantations treated with charcoal, and mineral or organic fertilisers. Trop. Sci. (2008)
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Abstract:
We assessed substrate-induced respiration and soil chemical properties in order to study the influence of charcoal, nitrogen and phosphorus fertilisation on two different perennial crops in a confounded factorial design on a highly weathered Amazonian upland soil. Each plantation tested three different factors in three different levels making up 27 treatment combinations. Whereas the banana plantation received mineral fertilisation in addition to charcoal applications (3rd factor), the guarana (Paullinia cupana) plantation was fertilised organically using chicken manure and bone meal as the corresponding factors.
Charcoal increased pH, total nitrogen, availability of sodium, zinc, manganese, copper and soil humidity, and decreased aluminium availability and acidity in the mineral-fertilised plantation only. This caused a signifi cant increase in basal respiration and microbial efficiency in terms of carbon dioxide release per microbial carbon in the soil. The microbial biomass, efficiency and population growth after substrate addition was significantly increased with increasing levels of organic fertiliser amendments. We conclude that charcoal is a valuable component especially in inorganic-fertilised agricultural systems.
Introduction:
Without continuous fertilisation, the extremely nutrient-poor Amazonian upland soils show no potential for agriculture beyond a tree-year lifespan of the forest litter mat, once biological nutrient cycles are interrupted by slash-and-burn (Tiessen et al. 1994). Slash-and-burn agriculture is a common practice in the tropics (Giardina et al. 2000; Goldammer 1993) and is considered to be sustainable if adequate (up to 20 years) fallow periods follow a short period of cultivation (Kleinman et al. 1995). Fertilisation is necessary for continuous cropping, but the strongly weathered soils of the tropics have a low nutrient-retention capacity and the intense tropical rains wash easily available and mobile nutrients rapidly into deep soil layers unavailable to most crop plants (Giardina et al. 2000; Hölscher et al. 1997; Renck and Lehmann 2004). …
The widespread existence of an anthropogenic fertile dark soil in the Amazon proves that human soil-manipulation can create permanently fertile soil (Woods and McCann 1999). The Amazonian dark earths (or ‘Terra Preta de Índio’) are found at pre-Columbian settlements throughout Amazonia in patches ranging in size from less than a hectare to many square kilometres (McCann et al. 2001). Today, and as assumed in the past, those soils are and were intensively cultivated by the native population. Their fertility is most likely to be linked to an anthropogenic accumulation of P and calcium (Ca) from bones (Lima et al. 2002), depositions of these and many other nutrients from a variety of human habitation activities (Woods 2003), and black carbon (C) as charcoal (Glaser et al. 2001b; Lima et al. 2002). Amazonian dark earths contain significantly more C, N, Ca and potassium (K) and up to 13.9 g kg-1 phosphorus (P2O Pentoxide 5) (almost 4 g kg-1 available P) (Lima et al. 2002), and cation exchange capacity, pH value and base saturation are signifi cantly higher than in the surrounding Oxisols (Glaser et al. 2000; Zech et al. 1990). Charcoal persists in the environment over centuries and is responsible for the stability of the Amazonian dark earth’s SOM (Glaser et al. 2001a).
