Tifton 85 (Cynodon sp.) is a forage crop widely used for the voluminous production, but it has also the potential to promote preservation or improvement in soil structural quality, when well managed. The aim of this work was to evaluate the soil physical quality in a rotational grazing area of Tifton 85 under irrigation in Prudente de Morais, MG, Brazil, due to the application of mineral and organic nitrogen fertilizers. The treatments included different forms of N supply: 400 kg ha-1 of urea; 400 kg ha-1 of bovine manure; 400 kg ha-1 of urea and manure, in proportion 1:1 and the control, without nitrogen fertilization. The following soil physical quality indicators were determined in the layers 0.0-0.05 m and 0.05-0.10 m after two years of N application: water retention curve, total porosity, macroporosity, microporosity, soil bulk density, available water capacity, bulk soil air capacity, soil matrix air capacity and relative water capacity. There were differences among the treatments, in both layers. In general, the treatments using bovine manure promoted greater water storage and availability, which was related to the increase of the microporosity, due to the organic matter effect. However, these same treatments presented a relative compaction, which was associated to the maintenance of higher soil moistures. It was concluded that, even under the effects of intensive grazing, there was generally adequate soil physical quality, but a special attention is recommended to the soil susceptibility to compaction. Resumo-O Tifton 85 (Cynodon sp.) é uma cultura forrageira muito utilizada para a produção de volumosos, mas também demonstra potencial para promover preservação ou melhoria da qualidade estrutural do solo, quando bem manejada. O objetivo deste trabalho foi avaliar a qualidade física do solo em área de pastejo rotacionado de Tifton 85 irrigado em Prudente de Morais, MG, Brasil, em função da aplicação de adubos nitrogenados de origem mineral e orgânica. Os tratamentos incluíram diferentes formas de suprimento de N: 400 kg ha-1 de ureia; 400 kg ha-1 de esterco bovino; 400 kg ha-1 de ureia e esterco, na proporção 1:1 e a testemunha, sem adubação nitrogenada. Determinaram-se os seguintes indicadores de qualidade física do solo nas camadas 0.0-0.05 e 0.05-0.10 m, após dois anos de manejo: curva de retenção de água, porosidade total, macroporosidade, microporosidade, densidade do solo, capacidade de água disponível, capacidade de aeração do solo, capacidade de aeração da matriz do solo e capacidade relativa de água no solo. Houve diferenças entre os tratamentos, em ambas as camadas. Em geral, os tratamentos com o uso de esterco promoveram maior retenção e disponibilidade de água, o que foi relacionado ao incremento da microporosidade, devido ao efeito da matéria orgânica. No entanto, esses mesmos tratamentos apresentaram uma relativa compactação, o que foi associado à manutenção de maiores umidades no solo. Concluiu-se que, mesmo sob os efeitos do pastejo intensivo, houve em geral adequada qualidade física do sol...

RESUMOO crescimento da renda e da população mundial tem demandado um aumento de alimentos e de insumos. Essas questões afetam diretamente a pecuária leiteira explorada em pastagens intensivas. Por meio deste estudo, buscou-se avaliar economicamente a estratégia da fertilização nitrogenada em pastagens destinadas a atividade leiteira, em distintos cenários econômicos e produtivos. Utilizou-se a margem bruta como indicador econômico. Ficou evidenciada a importância da eficiência da utilização de insumos e de forragem. No cenário atual de preços de fertilizante e de leite, a fertilização com nitrogênio (N) foi viável economicamente, principalmente em doses de, aproximadamente, 200 kg de N/ha/ano, quando houve fornecimento de concentrados e 400 kg de N/ha/ano, quando não ocorreu essa suplementação. Neste trabalho, a uréia apresentou melhor resultado econômico em relação ao sulfato de amônio.Tremos pra indexação: Alimentos, demanda, margem bruta, simulação, sustentabilidade. ABSTRACTIncome growth and world population growth has resulted in an increase of demand for food and supplies. These issues directly affect the dairy production in intensive grazing systems. The aim of this article is to evaluate economically the strategy of nitrogen fertilization in pasture for dairy activity in different economic and productive scenarios. Gross margin was used as economic indicator. The importance of efficient use of inputs and fodder was emphasized. In the current scenario of fertilizer and milk prices, fertilization with nitrogen (N) was economically viable, particularly in dosages of approximately 200 kg N / ha / year when there was a supply of concentrates and 400 kg N / ha / year when there was no such supplementation. In this work, the urea presented better economic results compared to ammonium sulfate.

The objective of this study was to evaluate the effect of the frequency of provision of protein energy supplementation on pasture during the dry period of the year on the performance of Nelore steers in rearing phase. FAZU teaching school conducted the experiment from July to September 2017. Twenty-two animals of the Nelore breed, aged 12 months and mean initial weight of 232.22 (± 20) kg, modules of 2 ha each, subdivided in six paddocks of Panicum maximum cultivars Mombaça and Tanzânia. The experimental design was completely randomized (DIC) and the averages were compared by the Tukey test at 5% significance. There was no significant difference between the three frequencies of supply of energy protein supplementation, in relation to the average daily weight gain, which were 837; 881 and 855g, at the frequencies of 7; 5 and 3 times per week, respectively. However, there was a significant difference (P <0.05) for the mean daily weight gain between the treatment in which the animals received mineral supplementation (434g), which was lower than the treatments in which the animals were fed with protein energy supplement at the level of 0.25% of body weight. In conclusion, during the period and in the evaluation conditions of this experiment, there was no difference in the effect of the frequency of supply of a protein energy supplement in the supply level of 0.25% of the animals' body weight. The average daily gain was higher for the animals that received the protein energy supplement compared to those supplemented with mineral. Five times a week supplementation obtained the best economic benefit among the evaluated frequencies.