Resumo: O objetivo deste trabalho foi avaliar o efeito do uso de diferentes adubos nitrogenados nas perdas de N por volatilização de NH3 e no rendimento de grãos de cultura de milho (Zea mays) na região semiárida do estado de Sergipe. O milho foi manejado sob condições de sequeiro e preparo convencional. Os tratamentos de fertilização foram: ureia revestida com enxofre (SU) e ureia organomineral (OMU). Também foram incluídos ureia comercial e sulfato de amônio (SA) como referência de fontes de N com alto e baixo potencial de volatilização de NH3, além de um controle não fertilizado com N. As fontes de N foram aplicadas na superfície do solo a uma taxa de 150 kg ha-1 de N, como cobertura, no estádio V5 de crescimento do milho. O experimento foi realizado em 2015 e repetido em 2016. As perdas de N pela volatilização de NH3 foram diferentes entre as fontes de N nos dois anos de estudo, com SA tendo apresentado a menor perda de N e ureia comercial, a maior. Na área tratada com OMU, as perdas pela volatilização de NH3 foram controladas de forma consistente, tendo mostrado redução de 74 e 67% em relação à da ureia regular em ambos os anos. SU, no entanto, apenas mitigou as perdas de NH3 em 2015, tendo as aumentado em 2016, em comparação à ureia comercial. O rendimento de grãos e o status de N da planta de milho, avaliados pela folha-índice, não refletiram claramente a perda de N pela volatilização de NH3. Para o semiárido de Sergipe, OMU é o melhor fertilizante à base de ureia para mitigar as perdas de N pela volatilização de NH3, e o uso de SA é uma alternativa para aumentar o rendimento do milho e eliminar as perdas de N como NH3.

Abstract: The objective of this work was to evaluate the effect of the use of different nitrogen fertilizers on N losses by NH3 volatilization and on the grain yield of a corn (Zea mays) crop grown in the semiarid region of the state of Sergipe, Brazil. Corn was managed under rainfed conditions and conventional tillage. The fertilization treatments were: sulfur-coated urea (SU) and organo-mineral-coated urea (OMU). Regular urea and ammonium sulfate (AS) were also included as a reference of N sources of high and low NH3-volatilization potential, as well as a control without N fertilization. The N sources were applied to the soil surface at a rate of 150 kg ha-1 N as side-dressing at the V5 growth stage of corn. The experiment was carried out in 2015 and repeated in 2016. Losses of N through NH3 volatilization differed among the N sources in the two study years, with AS presenting the lowest N losses and regular urea, the highest. In the area treated with OMU, losses by NH3 volatilization were consistently controlled, showing a reduction of 74 and 67% in relation to that of regular urea in both years. SU, however, only mitigated NH3-N losses in 2015, increasing them in 2016, compared with regular urea. Corn plant grain yield and N status, assessed by the index leaf, did not clearly reflect N losses by NH3 volatilization. For the semiarid of Sergipe, OMU is the best urea-based fertilizer to mitigate N losses by NH3 volatilization, and the use of AS is an alternative to increase corn yield and eliminate N losses as NH3.

RESUMO O objetivo com este trabalho foi avaliar estratégias de suplementação sobre o consumo de suplemento, comportamento e desempenho de novilhos zebuínos mantidos em pastagem de capim-marandu (Urochloa brizantha cv. Marandu) diferido. Foi utilizado delineamento inteiramente casualizado para testar cinco estratégias de suplementação: sal mineral (SM), sal proteinado com 25% de ureia (SP) e três multimisturas (45,5% NDT) com 10% (MM10), 15% (MM 15), ou 20% (MM20) de ureia. Foram utilizados vinte novilhos com peso inicial 300±24,9kg, sendo quatro por tratamento, mantidos em cinco piquetes de 3,4ha rotacionados semanalmente, de julho a outubro de 2010. Os dados foram submetidos à ANOVA, usando o Teste de Tukey para comparar as médias (P<0,05); entretanto, a análise econômica determinou a melhor estratégia. A ingestão de suplementos foi alterada (P<0,05) pela estratégia de suplementação, sendo de: 106, 196, 852, 666 e 400 g/animal/dia para SM, SP, MM10, MM15 e MM20, respectivamente. O aumento do consumo de suplementos não alterou o tempo de pastejo ou ruminação/ócio (P>0,05). SM resultou em perda de peso (-137 g/animal/dia). Utilizando-se o SP praticamente manteve o peso dos novilhos. Entretanto, para obtenção de ganho de peso, as multimisturas devem ser utilizadas (P<0,05). Nesses casos, o ganho de peso diário chegou a 324 g/animal (MM10). Baseado nos resultados econômicos, a melhor estratégia foi MM20, seguida de MM10.

SUMMARY The objective of this work was to evaluate different supplementation strategies on supplement intake, behavior, and performance of beef steers grazing stockpiled palisade grass (Urochloa brizantha cv. Marandu) pastures. There was used a completely randomized design trial to test five supplementation strategies: commercial mineral (SM), mineral plus25% of urea (SP), and three multimixtures (45.5% TDN) with 10% (MM10), 15% (MM 15), or 20% (MM20) of urea. Twenty zebuine steers weighting 300±24.9 kg of initial body weight, being four animals per treatment, were raised on five paddocks of 3.4 hectares under weekly rotation, from July to October of 2010. Data were submitted to ANOVA, using Tukey′s test to compare average values (P≤0.05); however, economic analysis determined the best strategy. Supplementation did not affect the grazing or rumination/resting time (P>0.05). The intake of supplements was affected (P<0.05) by supplementation strategy, being 106, 196, 852, 666, and 400 g/day for SM, SP, MM10, MM15, and MM20, respectively. SM resulted in losing weight (-137 g/animal/day). Using SP practically maintained the cattle weight. However, if gains are desired, multimixtures should be used (P<0.05). In those cases, daily weight gain reached 324 g/animal (MM10). Based on economic analysis, the best strategy was MM20, followed by MM10.

ABSTRACT The objective of this study was to evaluate the effects of polymer coated slow-release urea (SRU) in high-forage diets of beef steers on nutrient intake and digestibility, ruminal fermentation, microbial protein synthesis, and energy balance. Eight 24-mo-old rumen-fistulated castrated Nellore steers (average body weight = 418.0±40.0 kg) were used in a replicated 4 × 4 Latin square design. Animals were randomly distributed to receive one of the following diets: no urea inclusion; 1.0% inclusion of feed grade urea in the diet (dry matter [DM] basis); 1.0% inclusion of slow-release urea 1 in the diet (DM basis); and 1.0% inclusion of slow-release urea 2 in the diet (DM basis). Slow-release urea 2 had a similar composition to that of slow-release urea 1 and differed in that it contained 2.95% sulfur. A high-forage diet was provided (75% of total DM) and corn silage was used as the forage source. Diets with urea had increased crude protein (CP) intake, and CP and total digestible nutrients total tract digestion. Urea sources increased ruminal concentrations of ammonia nitrogen and acetate, and decreased butyrate concentrations. The polymer coated urea did not alter ruminal fermentation when compared with feed grade urea. Diets did not affect the energy balance of steers. Feed grade urea presented greater microbial protein synthesis than polymer coated slow-release urea. The partial replacement of soybean meal by 1% slow-release urea in a diet with 75% forage does not improve ruminal fermentation and microbial protein synthesis, and shows similar results as feeding feed grade urea to beef steers.

ABSTRACTThe objective of this experiment was to quantify the effects of feeding polymer-coated slow-release urea on nutrient intake and total tract digestion, milk yield and composition, nutrient balances, ruminal fermentation, microbial protein synthesis, and blood parameters in dairy cows. Sixteen Holstein cows (580±20 kg of live weight (mean ± standard deviation); 90 to 180 days in milk (DIM); and 28 kg/d of average milk yield) were used in a replicated 4 × 4 Latin square experimental design. The animals were assigned to each square according to milk yield and DIM. The animals were randomly allocated to receive one of the following experimental diets: 1) control (without urea addition); urea (addition of 1% on the diet DM basis); polymer-coated slow release urea 1 (addition of 1% on the diet DM basis); and polymer-coated slow release urea 2 (addition of 1% on the diet DM basis). All diets contained corn silage as forage source and a 50:50 forage:concentrate ratio. Milk and protein yield, production of volatile fatty acids, and propionate decreased when cows were fed diets containing urea. Addition of urea decreased nitrogen efficiency and nitrogen excreted in the feces. However, the diets did not change the cows' microbial protein synthesis, ruminal pH, or ammonia concentration. The inclusion of urea in cow diets decreases milk and protein yield due to lower production of volatile fatty acids. No advantages are observed with supplementation of polymer-coated slow-release urea when compared with feed-grade urea.

Nos últimos anos, novas tecnologias têm sido desenvolvidas para reduzir as perdas de N quando se utiliza ureia como fonte desse macronutriente. A utilização de fertilizantes de características ácidas pode reduzir as perdas de amônia por volatilização, quando combinados com a ureia. O objetivo deste trabalho foi avaliar as perdas de amônia provenientes de fontes de N revestidas e, ou, incorporadas com ou sem enxofre e bentonita. Esses foram aplicados na superfície de um Planossolo Háplico contido em bandejas (0,1 m2 de área e 10 cm de profundidade), em dose equivalente a 200 kg ha-1 de N. Foram avaliadas as perdas de N-NH3 por volatilização durante 21 dias, com auxílio de um coletor semiaberto. A adição de diferentes fontes de enxofre e de bentonita no processo de compactação da ureia reduziu as perdas de amônia em até 29 %, quando comparadas com a ureia granulada comercial, comprovando serem alternativas promissoras para aumentar a eficiência da adubação nitrogenada.

In recent years, new technologies have been developed to reduce N losses when using urea as a source of this macronutrient. The use of fertilizers with acidic features can reduce ammonia losses from volatilization when combined with urea. The objective of this study was to assess ammonia losses from sources of N with or without coating and/or incorporation of S and bentonite. These fertilizers were applied to the surface of a Haplic Planosol contained in trays (0.1 m2 area and 10 cm deep) at an N rate of 200 kg ha-1. Losses of NH3 through volatilization were evaluated for 21 days with the aid of a semi-open collector. The addition of different sources of S and bentonite in the urea compaction process reduced ammonia loss by up to 29 % when compared with commercial granulated urea, proving to be promising alternatives for increasing the efficiency of N fertilization.

Novas tecnologias com o intuito de minimizar as perdas de N-NH3 por volatilização devem ser desenvolvidas para aumentar a eficiência de uso do N-ureia. A incorporação de boro e cobre na ureia pode reduzir esses efeitos por meio da inibição da atividade da urease. O experimento foi conduzido em casa de vegetação, onde foram aplicados diferentes fertilizantes nitrogenados (ureia pastilhada com e sem boro e cobre, sulfato de amônio, ureia com inibidor da urease NBPT, ureia granulada e ureia revestida com boro e cobre) na superfície de um Planossolo Háplico contido em bandejas (0,1 m² de área e 10 cm de profundidade), em dose equivalente a 200 kg ha-1 de N. Foram avaliadas as perdas de N-NH3 por volatilização durante 18 dias, com o auxílio de um coletor semiaberto. A adição de cobre e boro no processo de pastilhamento da ureia reduziu as perdas de amônia por volatilização em até 54 %, quando comparado com a ureia granulada comercial, comprovando ser eficiente contra as perdas de N-NH3 por volatilização.

New technologies that enable a reduction in NH3-N volatilization losses should be developed to increase the N use efficiency of urea. The incorporation of boron and copper into urea can reduce these effects by inhibiting urease activity. The experiment was conducted in a greenhouse, testing the application of different N fertilizers (urea pellets with and without boron and copper, ammonium sulfate, urea with urease inhibitor NBPT, granulated urea and urea coated with boron and copper) to the surface of a Haplic Planosol in trays (area 0.1 m², depth 10 cm), at a rate of 200 kg ha-1 N. The NH3-N volatilization losses were assessed for 18 days, using a semi-open gas collector. The inclusion of copper and boron in the process of pelletizing urea reduced losses by up to 54 %, compared with the commercial granulated urea, proving the effective minimization of NH3-N volatilization losses.

O objetivo deste estudo foi avaliar a metodologia SREG GGE biplot e a análise de fatores na estratificação da interação genótipos×ambientes em milho. Foram avaliados 49 híbridos comerciais de milho de ciclo precoce em nove ambientes. Foi utilizado o delineamento látice quadrado 7×7, com duas repetições. Cada parcela consistiu de duas linhas de 5m espaçadas por 0,90m. Para a realização das análises, foram utilizados dados de produtividade de grãos. Os resultados indicaram a existência de dois mega-ambientes no Estado de Minas Gerais para híbridos de milho de ciclo precoce. A estratificação de ambientes pela análise de fatores mostrou-se mais seletiva em reunir ambientes pela similaridade de desempenho dos cultivares, mas não evidenciou as interações genótipos x ambientes específicas, o que foi possível pela análise SREG GGE biplot.

The objective of this study was to evaluate the use of SREG GGE biplot methodology and factor analysis to stratify the genotype×environment interaction in maize. Forty-nine early maize hybrids were evaluated in nine environments. The experimental design used was a 7×7 square lattice with two replicates. Each plot consisted of two 5m long rows spaced 0.90m apart. Grain yield data were used to perform the analysis. The results indicated the existence of two mega-environments in the State of Minas Gerais, Brazil, for early maize hybrids. The stratification of the environment by factor analysis was more selective to join the similarity the according with cultivar performance. However, this approach did not identify specific genotype x environment interactions, which is possible through SREG GGE biplot analysis.