Abstract
The research compared biomass production and nutrient release in an alley cropping system in two collection methods, the litterbag method and the direct collection method (Morley, Bennett, & Clark, 1964). The system was implemented in 2015 at 2017, at the Maranhão Federal University, Maranhão, Brazil. The experiment was a randomized block design with four treatments, consisting of leucaena+sombreiro (Leucaena leucocephala and Clitoria fairchildiana), leucena+acacia (Leucaena leucocephala and Acacia mangium), gliricidia+sombreiro (Gliricidia sepium and Clitoria fairchildiana) and gliricidia+acacia (Gliricidia sepium and Acacia mangium). In order to determine the remaining dry matter, nutrient release (N, P, K, Ca, Mg and Mn), the decomposition constants and the half-lives times of plant residues, 100 g of fresh material were conditioned in litterbags (50 g of each species), arranged on the soil surface. The second method was done by randomly throwing a collector on each plot in the same dimensions of the litterbags (0.40 x 0.40 m) and collecting the litter. For the two methods samples were collected at 0, 30, 60, 90 and 120 days after the start of the experiment. The litterbags method showed a higher C/N ratio at day 30 up to 120 days, which implies that this method is providing a different environment from the litter, where it would be overestimating the C/N ratio and retarding the decomposition. The G+S and G+A combinations were more rapidly decomposed than the combinations of L+S and L+A. The following order of release was established for the litterbags method: P > N > K > Ca > Mn > Mg, and for the method of collecting the litter: N > P > Ca > Mg > K > Mn.
Highlights
The litterbags method is the most used to determine the rates of decomposition of biomass applied in an agroforestry system, which allows experimental decomposition tests under field conditions
The litterbags presented high levels of N and Ca, the combination of G+A presented the highest N content (45.3 g kg-1) in relation to the other combinations, and the combination of L+S presented the highest levels of Ca (10.78 g kg-1) and Mg (7.71 g kg-1) (Table 1)
This study shows that the C/N ratio of the two collection methods varied over the experimental period (120 days)
Summary
The litterbags method is the most used to determine the rates of decomposition of biomass applied in an agroforestry system, which allows experimental decomposition tests under field conditions. Litterbags with mesh containing large holes can promote large losses of the contents, besides allowing the entrance of materials that were not considered in the installation of the experiment (Andrade, Caballero, & Faria, 1999), such as leaflets, weeds or small particles of ground. Another technical and methodological impasse related to the use of litterbags consists in the quantification of the decomposition constant (k), which only takes into account the leaf fraction and fine branches to the detriment of the other fractions that compose the vegetal biomass deposited in the soil
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