9 AJCS 15(01):9-15 (2021) ISSN:1835-2707 doi: 10.21475/ajcs.21.15.01.1942 Effects of composted swine manure on nutrient content in grains of Panicum miliaceum L. Dionei Schmidt Muraro 1* , Fabiana Lima Abrantes 2 , Claudir José Basso 3 , Fabio Lima Abrantes 4 , Vanessa Alba da Silva 3 , Adalin Cezar Moraes de Aguiar 5 , Ivan Ricardo Carvalho 6 , Henrique Pozebon 3 , Marcia Gabriel 3 , Marco Eustáquio de Sá 4 , Stela Maris Kulczynski 3 1 Department of Entomology and Acarology, University of São Paulo (ESALQ/USP) – Piracicaba, São Paulo, 13418- 900, Brazil 2 Departmentof Agronomy College, University of Oeste Paulista (UNOESTE), Raposo Tavares Highway Km 572, Presidente Prudente, São Paulo 19067175, Brazil 3 Department of Plant Protection, Federal University of Santa Maria (UFSM), Roraima Avenue 1000, Santa Maria, Rio Grande do Sul 97105900, Brazil 4 Department of Plant Science, Food Technology and Economy Partner, São Paulo State University Julio de Mesquita Filho (UNESP), Monção Street 226, Ilha Solteira, São Paulo 15385-000, Brazil 5 Department of Plant Science, Federal University of Viçosa (UFV), Avenida Peter Henry Rolfs, Viçosa, 36570-900, Brazil 6 Department of Agrarian Sciences, Regional University of Northwestern Rio Grande do Sul, 98700-000, Brazil Abstract The aim of this work was to evaluate the effect of different doses of composted swine manure on protein and macronutrient contents of proso millet grains and in nutrient export by the crop. The experiment was carried out in the years 2013 and 2014 in a randomized block design, with four replications and five treatments, composed of four doses of composted swine manure (0, 4.0, 8.0 and 12.0 Mg ha -1 ) and one dose of mineral fertilization (NPK 100-60-40 kg ha -1 ). Compost and mineral fertilizers were applied manually in each plot after the sowing of the crop, according to the established doses. After the harvesting, grain samples were taken to determine protein, N, P, K, Ca, Mg and S contents, as well as the amount of macronutrients exported by the crop. The data were submitted to analysis of variance. The means of the variables related to the compost doses were compared to the control plot (absence of fertilization) and to the mineral fertilization plot using the Tukey’ test (P≤0.05), and the effects of CSM doses were assessed by regression analysis, adopting as selection criteria the model and the magnitude of the regression coefficients at 5% of significance. The export of nutrients from the field by P. miliaceum grains at the dose of 4.0 Mg ha -1 of compost was equal to the mineral fertilization recommended for the crop, justifying the use of swine manure as a substitute for mineral fertilization. The use of compost provides protein content in P. miliaceum grains similar to the use of mineral fertilizer. Keywords: organic fertilizer, proso millet, pig slurry, composting, nutrient export, macronutrients. Abbreviations: CSM_composted swine manure; NPK_nitrogen phosphorus potassium; ASL_above sea level. Introduction Proso millet (Panicum miliaceum L.) is a short cycle grass (Lu et al., 2009) native to East Asia (Bettinger et al., 2007) and well adapted to warm climates (Baltensperger et al., 1995; Berglund, 2007). The grass has emerged as an alternative to crop rotation under no-tillage system in the USA (Habiyaremye et al., 2017), where it is grown mainly in the spring. Though still sparsely cultivated in Brazil, P. miliaceum has attracted the attention of growers as an alternative for wheat cultivation during the winter, since its short cycle allows the subsequent sowing of soybean within its optimum sowing window (Basso et al., 2015). The crop presents low production costs and high straw formation rate, one of the basic premises in the no-tillage system (Basso et al., 2015; Muraro et al., 2016). Proso millet grains can be used to feed poultry (Guglieri et al., 2004) and produce beer (Zarnkow et al., 2010) and ethanol (Rose and Santra, 2013). The use of swine waste as a nutritional source for agricultural crops has gradually increased in recent years (Meade et al., 2011) due to the resulting improvement in the chemical properties of the soil (Brito et al., 2005; Oliveira et al., 2014) and the lack of alternatives for the disposal of liquid swine waste in Brazil (Makara and Kowalsky, 2015; De Conti et al., 2016). Among the chemical elements typically present in swine waste, nitrogen (N) stands out in importance, since it is directly related to the grain yield of most crops and is usually required in large quantities (El- Shaarawi et al., 2011). Composted swine manure (CSM) is obtained from the mixture of liquid swine manure (LSM) and sawdust substrate, resulting in an organic fertilizer with high dry matter content (53%) and N in organic form. The