RESUMO O estudo foi desenvolvido para avaliar o fornecimento de nitrogênio (N) à rúcula através de compostos obtidos por compostagem automatizada de dejetos líquidos de suínos (DLS). Durante a compostagem, xisto retortado (XR) e dicianodiamida (DCD) foram adicionados aos DLS para mitigar as perdas gasosas de N. O estudo foi realizado em casa de vegetação, com quatro tratamentos, sendo três com aplicação dos compostos (composto DLS, composto DLS + XR e composto DLS + XR + DCD) e um sem aplicação de composto (testemunha), em dois solos contrastantes . O melhor resultado foi obtido com o composto sem aditivos (composto DLS), o qual aumentou a produção de matéria seca da rúcula em 2,2 vezes no Latossolo e 6,1 vezes no Argissolo, comparado ao tratamento testemunha. A presença do XR nos compostos reduziu a produção de rúcula em 27% no Latossolo e em 35% no Argissolo, enquanto a presença de DCD não afetou a produção de matéria seca da rúcula. Os resultados deste estudo indicam que a adição de XR aos DLS durante a compostagem diminui o fornecimento de N à rúcula, tanto no efeito imediato (1º corte) quanto residual (2º corte).

ABSTRACT This study was developed to evaluate nitrogen (N) supply to arugula from composts produced by automated composting of pig slurry (PS). During the composting process, retorted oil shale (ROS) and dicyandiamide (DCD) were added to PS to mitigate gaseous N losses. The study was developed in a greenhouse where four treatments were evaluated, three with compost addition (PS compost, PS compost + ROS, and PS compost + ROS + DCD) and one without compost (control) in two contrasting soils (clayey and sandy-loam). The best result was obtained with the compost without additives (PS compost), which increased the arugula dry matter yield 2.2 times in clayey soil and 6.1 times in sandy-loam soil compared to the control treatment. The presence of ROS in composts reduced arugula dry matter yield in 27% in clayey soil and 35% in sandy-loam, while DCD did not affect arugula dry matter yield. The results of this study show that the addition of ROS to PS during composting reduces N supply to arugula, both in the immediate (first cut) and residual effect (second cut).

ABSTRACT: The impact on nitrous oxide (N2O) emissions caused by combining dairy slurry (DS) and urea to supply crops with nitrogen (N) is still not well characterized. The main objective of this study was to compare the differences between N2O emissions in the cases of exclusive use of urea and the combined use of DS and urea as N sources to no-tillage wheat and corn. We also compared N2O emissions between two DS application methods (surface-broadcast vs. injection), as well as the addition of dicyandiamide (DCD) to DS. The experiment was conducted under no-tillage and six treatments were applied at sowing as follows: no fertilization (control), surface-broadcast urea (urea-N), surface-broadcast DS (DSs), surface-broadcast DS with DCD (DSs + DCD), shallow-injected DS (DSi), and shallow-injected DS with DCD (DSi + DCD). Urea was applied at side-dressing in all treatments with DS and urea-N. The N2O emissions were evaluated from the application of the treatments to wheat until 22 days after corn harvest, resulting in a total of 364 days. The partial supply of the N demand of wheat and corn, by DS application at sowing, and the posterior complement of N demand by side-dressing urea increased the annual N2O emissions only when DS was shallow-injected without DCD (DSi). Although the amount of N2O-N emitted from the DSi treatment was 1.04 kg ha-1 (91.2 %) higher than from DSs in corn, the annual N2O-N emissions did not differ between the two methods of DS application to the soil. The emission factors of N2O-N were low, ranging from 0.49 % (DSi + DCD) to 1.27 % (DSi). The results of this study suggest that the combined use of DS with urea in N fertilization of no-tillage wheat and corn (DS applied at sowing and urea at side-dressing) caused no changes in the annual N2O-N emissions compared to crops fertilized exclusively with urea (1/3 at sowing + 2/3 at side-dressing). However, DCD should be added if DS is shallow-injected.