Fragmentation, fiber separation, decomposition, and nutrient release of secondary-forest biomass, mechanically chopped-and-mulched, and cassava production in the Amazon

Abstract

No-tillage planting in mechanically-chopped secondary-forest seeks to replace slash-and-burning agriculture. We evaluated the effect of horizontal (HC) and vertical (VC) chopping-and-mulching mechanisms on vegetation fragmentation and decomposition rate and nutrient release from chopped residue, and on cassava production in eastern Amazon. Chopped-and-mulched residue was classified into four residue-size (Fs 1 = 1-7, Fs 2 = 7-25, Fs 3 = 25-35, and Fs 4 = >35 mm) and six residue-type (with husk/ bark -WB, partially chopped -PC, compact -C, partially shredded into fibers -PS, completely shredded into fibers -CS, and formless residue -F) classes. In litter-bags, residual dry matter (DM) was determined at five different days after chopping-and-mulching and residue distribution on soil surface (DAD), whereas release of N, P, K, Ca, and Mg was evaluated at four days. Residues-size and -type classes showed similar decomposition behavior, with a reduction of approximately 60% of initial DM at 90 DAD. Nevertheless, reduction in DM was slow, where 52 days are necessary for half of labile residue to be decomposed, with part of labile and recalcitrant residue remaining on soil surface. DM and nutrients in residue reduced over time. DM was 25% for residues-size classes for HC, 20% for VC, and 26% for residuetype classes, on average, at 300 DAD. Nutrients remaining in residues at 300 DAD were 26% and 27% of N, 26% and 22% of P, 29% and 22% of K, 16% and 15% of Ca, and 17% and 23% of Mg, respectively for HC and VC. Release of nutrients was, generally, greater for smaller residue-size classes, similar between choppingand-mulching mechanisms, and did not affect cassava yield.2015 Elsevier B.V. All rights reserved.

ALTERAÇÕES QUÍMICAS DE UM CAMBISSOLO HÚMICO CAUSADAS POR FLORESTAMENTO COM Pinus taeda EM ÁREA DE CAMPO NATURAL

“…Nesse caso, os autores também associaram a redução do N à absorção desse elemento e imobilização na biomassa acima do solo, já que o N é um dos macronutrientes que concentram maiores teores nas acículas em distintos estádios fenológicos (VIERA; SCHUMACHER, 2009). Logo, a manutenção de resíduos vegetais tem uma contribuição fundamental para a ciclagem de nutrientes e manutenção da fertilidade do solo em sistemas florestais ou agroflorestais (REICHERT et al, 2015). 462 FLORESTA,Curitiba,PR,v.…”

Phosphorus Fertilization Increases Biomass and Nutrient Accumulation Under Improved Fallow Management in a Slash-and-Mulch System in Eastern Amazonia, Brazil

“…Chop-and-mulch, a fire-free technique for land preparation (Denich et al, 2004), conserves nutrients, improves soil quality, and reduces carbon dioxide-equivalent emissions from the soil to the atmosphere in comparison to slash-and-burn, as shown by studies conducted in eastern Amazonia (Sommer et al, 2004;Davidson et al, 2008;Comte et al, 2012;Reichert et al, 2015Reichert et al, , 2016). However, chop-and-mulch has not always increased soil carbon stocks (Perrin et al, 2014).…”

Phosphorus Forms in Ultisol Submitted to Burning and Trituration of Vegetation in Eastern Amazon

“…The experimental design was completely randomized, with three treatments and five replications, with the following management systems: traditional area of management "slash-and-burn" (SB); alternative management "slash-and-mulch" (SM); and adjacent secondary vegetation as a reference area (SV (Reichert et al, 2015b).…”

“…In tropical conditions, Po is of great importance to P conservation in soils (Cunha et al, 2007). In a study that assessed the fragmentation, decomposition and nutrient release of biomass from shredded secondary forest in the Amazon, Reichert et al (2015b) observed a reduction in residual P in the crushed plant material and their release in soil solution, probably because the P concentration in plant tissue primarily occurred in cell vacuoles as inorganic P and monoesters (Giacomini et al, 2003), which are highly soluble forms. (Bowman and Cole, 1978a;Bowman, 1989).…”