Abstract
Large quantities of poultry litter are being produced in Brazil, which contain appreciable amounts of phosphorus (P) that could be of environmental concern. To assess the immediate environmental threat, five poultry litters composed of diverse bedding material were incubated for 43 days under greenhouse conditions. The litters consisted of: coffee bean husk (CH); wood chips (WC); rice husk (RH); ground corn cobs (CC) and ground napier grass (NG) (Pennisetum purpureum Schum.), in which the change in forms of soluble P was evaluated using 31P NMR spectroscopy. On average, 80.2 and 19.8 % of the total P in the extract, respectively, accounted for the inorganic and organic forms before incubation and 48 % of the organic P was mineralized to inorganic P in 43 days of incubation. Wide variation in the organic P mineralization rate (from 82 % -WC to 4 % - NG) was observed among litters. Inorganic orthophosphate (99.9 %) and pyrophosphate (0.1 %) were the only inorganic P forms, whereas the organic P forms orthophosphate monoesters (76.3 %) and diester (23.7 %) were detected. Diester P compounds were mineralized almost completely in all litters, except in the CH litter, within the incubation period. Pyrophosphates contributed with less than 0.5% and remained unaltered during the incubation period. Wood-chip litter had a higher organic P (40 %) content and a higher diester: monoester ratio; it was therefore mineralized rapidly, within the first 15 days, achieving steady state by the 29th day. Distinct mineralization patterns were observed in the litter when incubated with a clayey Oxisol. The substantial decrease observed in the organic P fraction (Po) of the litter types followed the order: CH (45 %) > CC (25 %) > RH (13 %) ≈ NG (12 %) > WC (5 %), whereas the Pi fraction increased. Incubation of RH litter in soil slowed down the mineralization of organic P.
Highlights
Brazil is the 3rd world leading producer of chicken meat, exporting 3.65 million tons in 2008 (ABEF, 2008)
Results of this study indicate that poultry litter contains a considerable amount of soluble P inorgânico (Pi), which increases during incubation
The results found here show that a substantial proportion (39 %) of P present in the poultry litters is in organic forms, which is higher than the 21% P fraction (Po) reported by Peperzak et al (1959) and 25 % reported by Cassol et al (2001) in Southern Brazil, based on Hedley‘s fractionation scheme (Hedley et al, 1982)
Summary
Brazil is the 3rd world leading producer of chicken meat, exporting 3.65 million tons in 2008 (ABEF, 2008). The total production of swine and poultry manure in Brazil was estimated at 65 million tons, based on the number of swine and poultry animals in 2003 (IBGE, 2003), and since this number has increased tremendously. This material generally contains high levels of plant macronutrients, ranging from 39 to 49 g kg-1 N, 3.6 to 9.9 g kg-1 P, and 10 to 20 g kg-1 K (Kingery et al, 1994; Williams et al, 1999; Sauer et al, 2000). Poultry litters in the Zona da Mata in Minas Gerais contain on average 34 g kg-1 N, 16 g kg-1
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