RESUMO A elucidação do processo de mineralização de compostos orgânicos permite entender a liberação de nutrientes para as plantas. Objetivou-se com este trabalho avaliar a mineralização de nitrogênio e carbono de composto orgânico proveniente de resíduos da produção e abate de pequenos ruminantes, aplicados sobre um Neossolo Flúvico. O composto consiste de restos de capim (forrageiras), estercos e resíduos do abate como sangue, vísceras e a carcaça de caprinos e ovinos. Em condições de laboratório, dois experimentos foram conduzidos em um delineamento inteiramente casualizado, considerando-se as doses de composto orgânico nos seguintes níveis: zero; 3,75; 7,5; 15 e 30 Mg ha-1. Para o ensaio de mineralização de nitrogênio e carbono foram avaliados 11 e 32 tempos de coletas (épocas de amostragem), respectivamente. No ensaio de mineralização de nitrogênio foi medido o teor de nitrogênio inorgânico (amônio e nitrato) e no experimento de carbono foi quantificado a concentração de C-CO2. O maior incremento entre as doses aplicadas de composto orgânico proveniente de resíduos da produção e abate de pequenos ruminantes foi de 70% e 69% para o nitrogênio e o carbono potencialmente mineralizável com as quantidades de 7,5 e 30 Mg ha-1, em relação as doses de 3,75 e 7,5 Mg ha-1, respectivamente. O carbono e o nitrogênio orgânico provenientes com composto de resíduos da produção e do abate de pequenos ruminantes são rapidamente mineralizados no solo (até 45 dias) devido à sua baixa relação C/N.

ABSTRACT Elucidating the mineralization of organic composts makes it possible to understand the release of nutrients to plants. The objective of this study was to evaluate the mineralization of nitrogen (N) and carbon (C) from organic compost from residues of the production and slaughter of small ruminants, applied on a Neossolo Flúvico (Fluvents). The compost consists of remains of grass (forage), manure and slaughter residues such as blood, viscera and the carcass of goats and sheep. Under laboratory conditions, two experiments were conducted in a completely randomized design, considering the doses of organic compost at the following levels: zero; 3.75, 7.5, 15 and 30 Mg ha-1. For the N and C mineralization tests, 11 and 32 collection times (sampling periods) were evaluated, respectively. Inorganic N content (ammonium and nitrate) was measured in the N mineralization test, and CO2-C concentration was quantified in the C mineralization test. The largest increments between the applied doses of organic compost from residues of the production and slaughter of small ruminants were 70% and 69% for potentially mineralizable N and C, with amounts of 7.5 and 30 Mg ha-1 at doses of 3.75 and 7.5 Mg ha-1, respectively. Organic C and N from residues of the production and slaughter of small ruminants are rapidly mineralized in the soil (up to 45 days) due to their low C/N ratio.

ABSTRACT The application of organic composts derived from animal husbandry or agro-industry is a promising option to improve nutrient cycling and supply of soils and, consequently, forage production. The objective of this study was to evaluate the soil chemical properties and the nutritional state of elephant grass in response to rates of organic fertilizer composted from the waste of small ruminant production and slaughter systems. The experiment was conducted on a Fluvisol of a forage field with elephant grass var. Cameroon, and was arranged in a randomized block design with split-plots with repeated measures over time. Six rates of organic compost (0, 13.3, 26.6, 39.9, 52.3, and 79.8 t ha-1, in plots) and an additional treatment with mineral fertilizers were evaluated in four growth periods (60, 120, 180, and 240 days, in subplots) with four replications, resulting in a total of 28 plots. Soil fertility was evaluated after the fourth growth period, while leaf analysis was determined in every 60-day period. The increasing rates of organic compost increased the concentrations of OM, NH4+, NO3–, NH4+ + NO3–, P and base saturation, while the H+Al values decreased and the N and P contents increased in the plants. Compared with mineral fertilization, soil inorganic nitrogen and phosphorus increased by 34 and 97 % in response to the application of organic compost. In response to the application of organic compost, the leaf contents of all studied nutrients remained adequate in all studied periods, except for the macronutrient N and micronutrient Mn.