Year-round poultry litter decomposition and N, P, K and Ca release

Poultry litter is an important nutrient source in agriculture, although little information is available regarding its decomposition rate and nutrient release. To evaluate these processes, poultry litter (PL) was applied to the soil to supply 100, 200 and 300 kg ha-1 N contained in 4,953, 9,907 and 14,860 kg ha-1 PL, respectively. The litter bag technique was used to monitor the process of decomposition and nutrient release from the litter. These bags were left on the soil surface and collected periodically (after 15, 30, 60, 90, 120, 150, 180, 210, 240, 270, 300, 330, and 365 days). The dry matter (DM) loss was highest (35 %) after the first 30 days of field incubation. The highest nutrient release occurred in the first 60 days on the field, when 40, 34, 91, and 39 %, respectively, of N, P, K, and Ca of the initial PL dry matter (4,860 kg ha-1) was already released to the soil. In absolute terms, these percentages represent 40, 23, 134, and 69 kg ha-1 of N, P, K, and Ca and these values doubled and tripled as the PL fertilization rates increased to 9,907 and 14,860 kg ha-1, respectively. After one year of field incubation, the residual contents in the litter were 27, 15, 18 and 30 % of the initial DM , and N, P and Ca, respectively. The release rate of K was the fastest and 91 % of the K had been released from the PL after 30 days of field incubation. Cama de aviário é uma importante fonte de nutrientes para a agricultura, porém existem poucas informações em relação à sua taxa de decomposição e liberação de nutrientes. O objetivo deste trabalho foi avaliar a taxa de decomposição e liberação de nutrientes da cama de aviário. A adubação foi realizada a fim de suprir 100, 200 e 300 kg ha-1 de N; para isso, foram aplicados ao solo 4.953, 9.907 e 14.860 kg ha-1 de cama. Para monitorar o processo de decomposição e liberação de nutrientes da cama, utilizou-se a técnica dos sacos de decomposição, os quais foram deixados na superfície do solo e recolhidos após 15, 30, 60, 90, 120, 150, 180, 210, 240, 270, 300, 330 e 365 dias. As maiores perdas de matéria seca (MS) (35 %) foram verificadas nos primeiros 30 dias de incubação em campo. As maiores taxas de liberação de nutrientes ocorreram nos primeiros 60 dias de incubação em campo. Nesse período, 40, 34, 91 e 39 % do N, P, K e Ca encontrados na matéria seca inicial da cama (4.860 kg ha-1) já haviam sido liberados ao solo. Em valores absolutos, essas porcentagens representam 40, 23, 134 e 69 kg ha-1 de N, P, K e Ca, q