Agricultural Systems Located in the Forest-Savanna Ecotone of the Venezuelan Amazonian. Are Organic Agroforestry Farms Sustainable?

Abstract

Abstract:The savannas located in the forest-savanna ecotone in the Venezuelan Amazon have unfertile sandy ultisols and entisols which show a very low crop production unless they are supplemented with large amounts of fertiliser. In spite of this restriction, local farmers have established long-term production systems by using low input doses of organic manure. The use of organic waste in unfertile ultisols and entisols typical of savannas have resulted in increases in organic matter content and biological activities in soils with respect to inorganic fertilised or non-fertilised natural savanna, which, in turn, may be related to increases in crop productivity. These results could be a successful and reliable soil management technique for rehabilitation of the South American savannas.

Impact of land protection in soil quality properties and in earthworm biomass in Venezuelan savannas

“…Preliminary results presented by López- showed that protection has also improved soil fertility, because of a reduction of compaction, an increase in the water holding capacity, organic matter, pH, exchangeable bases, organic phosphorus and total phosphorus and nitrogen. Microbial C-biomass for the EBLL savannas were higher than the values presented by Gómez et al (2008) and López-Hernández et al (2009) in Trachypogon savannas of Eastern Llanos and Venezuelan Amazonia, respectively. On the contrary, the dehydrogenase values although greater in PS respect NS were lower than the information reported by López-Gutiérrez et al (2004) and Gómez and Paolini (2011) in savannas of Eastern Llanos, Venezuela.…”

“…Moreover, earthworms are ascribed to affect soil fertility and plant growth through the production of casts which affects the availability and nature of both the spatial and trophic resource in soil. The beneficial effects of the earthworm activities include: i) improvement of soil physical properties which affect soil water retention capacity, drainage, and the formation and degradation of aggregates (Blanchart et al, 1999); ii) chemical and biological effects on the rate of organic matter degradation and nutrient cycling (Chapuis-Lardy et al, 2011;Lavelle et al, 1994;López-Hernández et al, 2004, 2009, and iii) alteration of the composition and activity of microorganisms and soil invertebrates (Lavelle and Spain, 2001). All these processes significantly impact the soil fertility primarily through the release of available forms of nitrogen (N) and phosphorus (P) (Baker, 2007;Chapuis-Lardy et al, 2011;Chaoui et al, 2003;Jiménez et al, 2003;López-Hernández et al, 1993) once the soil passes through the gut of the individual earthworm.…”

Earthworm Populations in Savannas of the Orinoco Basin. A Review of Studies in Long-Term Agricultural-Managed and Protected Ecosystems

“…Microbial and enzymatic activities in the organic agricultural forestry system (OAFS) and the natural savanna (NS) in Amazonas State, Venezuela. Modified from López-Hernández [33]. Microbial N-biomass also significantly increased after compost amendment, since both increment were of a similar magnitude the C-microbial biomass/N-microbial biomass was similar in NS and OAFS (Table 3).…”

“…Methodological aspects concerning earthworm collection and other soil quality indices of the Case Studies of the present revision have been already presented by López-Hernández and collaborators [5,6,12,13,33].…”

“…Amazonia represents one-fifth of the Venezuelan territory (approximately 180,000 km 2 ); most of this surface is covered by pristine primary forests where, due to the lack of accessible roads, human activity is of minor importance. An important piece of savanna land, however, extends in the northern and southern part of Puerto Ayacucho, the capital of Amazonas State [33]. Nonetheless, a problem of sustainability derived from the potential use of Puerto Ayacucho´s savannas is that they are located on very sandy soils (over 90%) and consequently they are nutrient limited.…”