Identifying maize inbred lines that are more efficient in nitrogen (N) use is an important strategy and a necessity in the context of environmental and economic impacts attributed to the excessive N fertilization. N-uptake efficiency (NUpE) and N-utilization efficiency (NUtE) are components of N-use efficiency (NUE). Despite the most maize breeding data have a multi-trait structure, they are often analyzed under a single-trait framework. We aimed to estimate the genetic parameters for NUpE and NUtE in contrasting N levels, in order to identify superior maize inbred lines, and to propose a Bayesian multi-trait multi-environment (MTME) model. Sixty-four tropical maize inbred lines were evaluated in two experiments: at high (HN) and low N (LN) levels. The MTME model was compared to single-trait multi-environment (STME) models. Based on deviance information criteria (DIC), both multi- and single-trait models revealed genotypes x environments (G x E) interaction. In the MTME model, NUpE was found to be weakly heritable with posterior modes of heritability of 0.016 and 0.023 under HN and LN, respectively. NUtE at HN was found to be highly heritable (0.490), whereas under LN condition it was moderately heritable (0.215). We adopted the MTME model, since combined analysis often presents more accurate breeding values than single models. Superior inbred lines for NUpE and NUtE were identified and this information can be used to plan crosses to obtain maize hybrids that have superior nitrogen use efficiency.

The aim of this study was to evaluate the adaptability and stability of 29 commercial maize hybrids in the southeast of the State of Minas Gerais, Brazil, employing three methods. The 29 commercial maize hybrids from the 2014/2015 crop were evaluated for grain yield in five locations in the southeast of Minas Gerais. A randomised-block design was used, with two replications. Each lot comprised two rows, five meters in length, at a spacing of 0.80 m, giving an effective area of 8.00 m2. In addition to individual and combined variance analysis, the methods of Eberhart & Russell (1966), AMMI (Additive Main Effects and Multiplicative Interaction Analysis) and mixed models were used to evaluate the adaptability and stability of the 29 hybrids. There was a significant difference (P<0.01) for the effects of hybrid, environment and the hybrid x environment interaction. The majority of the hybrids under evaluation displayed broad adaptability with good stability. It was concluded that the Eberhart & Russell, AMMI and mixed-model methods show similar results in classifying maize hybrids of broad adaptability. There is a difference in indicating hybrids with specific adaptability to favourable and unfavourable environments. Based on the three methods, the hybrids SHS7920PRO, BM709PRO2, BRS1055 and BM650PRO2 show a general adaptability for the environments under evaluation.

ABSTRACT:The adequate supply of nitrogen to coffee plantation is one of the main challenges of organic agriculture. The aim of the present study was to evaluate the effect of organic fertilization with two legume species in different intercropping periods on nitrogen nutrition, initial growth and productivity of coffee plantation. The experimental design was in randomized blocks, in 2x4 split-plot factorial design, being that the plot consisted of two intercrops (coffee+jack bean and coffee+hyacinth bean) and the four intercropping periods (30, 60, 90 and 120 days after sowing of the legume), and the subplot by 50% and 100% of fertilization for the coffee plantation. The increase in the intercropping period between legumes and coffee plantation favored a greater increase in height and node number of coffee trees, besides showing higher heights when fertilized with 50% of the recommended dose and intercropped with hyacinth bean. The intercropping with the hyacinth bean resulted in a larger crown diameter of coffee trees in 2010 and a larger diameter accumulated in the two evaluated years. Higher N contents were found in coffee trees fertilized with 100% of the recommended dose. The legumes supplied the nutritional requirements of the coffee harvest fertilized with 50% of the dose. The bean yield of the processed coffee is not affected by the intercropping with the green manures of jack bean or hyacinth bean.Index terms: Coffea arabica cv. Oeiras, Canavalia ensiformis, Dolichos lablab, nitrogen cycling, organic fertilization. PERÍODO DE CONSORCIAÇÃO ENTRE ESPÉCIES DE ADUBOS VERDES E CAFEEIROS ADUBADOS ORGANICAMENTERESUMO: O suprimento adequado de nitrogênio aos cafeeiros é um dos principais desafios da agricultura orgânica. O trabalho objetivou avaliar o efeito da adubação orgânica com duas espécies de leguminosas em diferentes períodos de consorciação sobre a nutrição nitrogenada, o crescimento e a produtividade iniciais de cafeeiros. O delineamento foi em blocos casualizados, em esquema fatorial (2x4) com parcela subdividida, sendo a parcela constituída por dois consórcios entre cafeeiros e leguminosas (café+feijão-de-porco e café+lablabe) e os 4 períodos de consorciação (30, 60, 90 e 120 dias após a semeadura da leguminosa), e a subparcela por 50% e 100% da adubação para o cafeeiro. O aumento do período de consorciação entre leguminosas e cafeeiros favoreceu um maior incremento em altura e do número de nós dos cafeeiros, e estes apresentaram maiores alturas quando fertilizados com 50% da dose recomendada e consorciados com lablabe. A consorciação com a lablabe resultou em maior diâmetro de copa dos cafeeiros em 2010 e maior diâmetro acumulado nos dois anos avaliados. Maiores teores de N foram encontrados nos cafeeiros adubados com 100% da dose recomendada. As leguminosas complementaram e supriram as necessidades nutricionais exigidas na colheita do café adubado com 50% da dose. O rendimento de grão do cafeeiro beneficiado não é prejudicado pelo consórcio com os adubos verdes feijão-de-porco ou lablabe.Termos pa...

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RESUMO Adubação nitrogenada de cafeeiros com composto e crotaláriaA resposta do cafeeiro aos adubos orgânicos é pouco estudada e, por isso, objetivou-se, neste trabalho, avaliar o efeito de diferentes doses de composto e de Crotalaria juncea L. sobre o crescimento, a produção e a nutrição nitrogenada dos cafeeiros. Os tratamentos foram: composto orgânico, nas doses de 25, 50, 75 e 100% da adubação recomendada, com ou sem a parte aérea de C. juncea. A C. juncea foi cultivada com N-NH 4 (2% de 15 N) e aplicada nos cafeeiros. A crotalária promoveu maior crescimento em altura e diâmetro de copa do cafeeiro. No 1º ano, o percentual de N derivado da crotalária atingiu 8,5% aos sete meses e 4,1%, aos quinze meses após a adubação. No 2º ano, foram atingidos 17,9% de N derivado da crotalária no início da colheita, cinco meses após a adubação. O aumento das doses de composto promove a elevação do pH, P, K, Ca, Mg, Soma de bases, CTCefetiva, saturação de bases e matéria orgânica, e redução da acidez potencial. O uso do isótopo 15 N permite a identificação da contribuição do N derivado da crotalária para o cafeeiro, com percentuais foliares de N derivado de Crotalaria juncea de 9,2 a 17,9%. Information concerning the response of coffee to organic fertilizers is scarce. This study evaluates the effect of different doses of compost and Crotalaria juncea L. on growth, production and nitrogen nutrition of coffee trees. The treatments consisted of compost at rates of 25, 50, 75 and 100% of the recommended fertilization, with or without the aerial part of C. juncea. C. juncea was grown with NH 4 -N (2% 15 N) and applied to coffee. The use of C. juncea increased growth in height and diameter of the coffee canopy. In the first year, the percentage of N derived from C. juncea reached 8.5% at seven months and 4.1% at fifteen months after fertilization. In the second year, the percentage of N derived from C. juncea reached 17.9% N at the early harvest, five months after fertilization. Increased rates of compost increased pH , P , K , Ca , Mg , sum of bases , effective CEC, base saturation and organic matter and reduced potential acidity. Palavras 15N allowed the identification of the N contribution from C. juncea with percentage of leaf N derived from Crotalaria juncea from 9.2 to 17.9%.

ABSTRACT:The knowledge about the rate of decomposition and nitrogen mineralization of green manures provides synchronization with the higher absorption stage by the coffee tree. The rate of decomposition and nitrogen mineralization varies according to the species of green manure and with the environmental factors. The aim of the present study was to evaluate the decomposition and nitrogen mineralization of two green manures intercropped with coffee trees for three different periods. The experiment was divided into two designs for statistical analysis, one referring to the characterization of plant material (fresh mass, dry matter, dry matter content, nitrogen concentration and accumulation in the jack bean (Canavalia ensiformis) and hyacinth bean (Dolichos lablab) and another to evaluate the rate of decomposition and N mineralization of these species. The decomposition rate decreased in both species as their growth time increased in the field. The decomposition was influenced by the phenology of green manures. Nitrogen mineralization of the jack bean decreased as the growth period in the field increased and was faster than hyacinth bean only when cut at 60 days. The N mineralization was slower than mass decomposition in both species.Index terms: Coffea arabica cv. Oeiras, Canavalia ensiformis, Dolichos lablab, decomposition rate, nitrogen cycling. DECOMPOSIÇÃO E MINERALIZAÇÃO DO NITROGÊNIO PROVENIENTE DE ADUBOS VERDES CONSORCIADOS COM CAFEEIROSRESUMO: O conhecimento sobre a taxa de decomposição e mineralização de nitrogênio dos adubos verdes possibilita uma sincronia com o estádio de maior absorção pelo cafeeiro. A taxa de decomposição e mineralização de nitrogênio variam com a espécie de adubo verde utilizado e com os fatores ambientais. O objetivo deste trabalho foi avaliar a decomposição e a mineralização de nitrogênio de dois adubos verdes, consorciados com cafeeiros por três períodos diferentes. O experimento foi separado em dois para análise estatística, sendo um referente à caracterização do material vegetal (massa fresca, massa seca, teor de massa seca, concentração e acúmulo de nitrogênio no feijão-de-porco e lablabe) e outro para avaliação da taxa de decomposição e mineralização do N dessas espécies. A taxa de decomposição reduziu em ambas as espécies à medida que se aumentou o tempo de crescimento destas no campo. A fenologia dos adubos verdes influenciou sua decomposição. A mineralização do nitrogênio do feijão-de-porco foi mais lenta à medida que aumentou o período de crescimento no campo e foi mais acelerada que da lablabe apenas quando cortado aos 60 dias, apresentando similaridade aos 90 e 120 dias e a mineralização do N foi mais lenta que a decomposição da massa, em ambas as espécies.Termos para indexação: Coffea arabica cv. Oeiras, Canavalia ensiformis, Dolichos lablab, taxa de decomposição, ciclagem de nitrogênio.