ABSTRACT: Soybean [Glycine max (L.) Merr.] grain yield is closely associated with the level of optimal nitrogen (N) supply, especially during the reproductive stages. Foliar fertilization with low rates of N have been considered as a strategy for furnishing additional N and enhancing grain yields. Field studies using 15N tracer were conducted over two growing seasons to investigate the impact of foliar N fertilization on grain yield, plant N content, the amount of N derived from fertilizer (NDFF) and N recovery efficiency (NRE). Four foliar N rates (0, 1300, 2600 and 3900 g ha−1) were supplied by two equal split applications at the R1 and R3 stages. Foliar N fertilization of soybean canopies did not affect grain yield, grain N content, shoot N content nor plant N content. Total NDFF was increased from 0.7 to 2.0 kg ha−1 across the N rates. Nonetheless, NRE was unaffected by foliar N fertilization, which averaged 53 %. Soybean plants allocated the same amount of N fertilizer to both grains and shoots. No significant effects of low rate foliar N fertilization were registered on soybean grain yield nor plant N content, despite considerable N fertilizer recovery by plant organs.

Resumo: Cobalto (Co) e molibdênio (Mo) são nutrientes indispensáveis para a fixação biológica e assimilação de nitrogênio pela soja. Neste trabalho teve-se como objetivo avaliar o aumento do Co e Mo nas sementes de soja pela aplicação via foliar desses nutrientes na planta mãe. O experimento foi realizado em lavoura de produção de sementes, em esquema fatorial 3x3 com três doses de Co e Mo e três tratamentos (épocas). Cada tratamento foi constituído de duas épocas de aplicação R3+R5.1 (T1); R3+R5.4 (T2); R5.1+R5.4 (T3). As doses foram 0, 400 e 600 g.ha−1 de Mo e 0, 40 e 60 g.ha−1 de Co. Não houve diferença na produtividade, peso de mil sementes e germinação. Houve interação entre dose e época no teor de Mo. A aplicação de 400 g.ha−1 de Mo no tratamento T1 (R3+R5.1) proporcionou maior teor de Mo nas sementes (13,5 g.kg−1), 1350% maior do que a testemunha. Para o Co houve diferença apenas para as doses, sendo que a aplicação de 40 ou 60 g.ha−1 de Co elevou em 30% o teor do nutriente nas sementes. Conclui-se que há maior enriquecimento de Co e Mo nas sementes com a aplicação de, respectivamente, 40 e 400 g.ha−1 aplicados em R3+R5.1.

Abstract: Cobalt (Co) and molybdenum (Mo) are vital nutrients for biological fixation and nitrogen assimilation by soybean. This study aimed to evaluate the increase of Co and Mo contents in soybean seeds by leaf applications. The experiment was carried out in a seed production field in a 3 × 3 factorial scheme with three Co and Mo doses and three treatments (times). Each treatment consisted of two application times: R3+R5.1 (T1), R3+R5.4 (T2), and R5.1+R5.4 (T3). Doses were 0, 400, and 600 g.ha−1 of Mo and 0, 40, and 60 g.ha−1 of Co. No difference was observed for productivity, one thousand-seed weight, and germination. An interaction was observed between dose and application time in the Mo content. The application of 400 g ha−1 of Mo in T1 (R3+R5.1) provided a higher Mo content in the seeds (13.5 g.kg−1), which is 1350% higher when compared to the control. For Co, there was a difference only for doses, and the application of 40 or 60 g.ha−1 of Co increased seed nutrient content by 30%. Therefore, a higher enrichment of Co and Mo was observed in seeds with applications of 40 and 400 g.ha−1, respectively, applied in R3+R5.1.

RESUMO A dinâmica de biomassa e nutrientes do milho pode ser alterada quando consorciado com Brachiaria (syn. Urochloa spp.). Objetivou-se investigar a dinâmica de biomassa, nitrogênio (N), fósforo (P) e potássio (K) para sistemas de produção de milho consorciado com espécies de Brachiaria. Campos experimentais foram conduzidos durante a safra e safrinha, em esquema de parcelas subdivididas. As parcelas principais foram compostas por espécies de braquiária (B. brizantha,B. ruziziensis, e B. Convert) consorciadas com milho, além de monocultivo de milho. As subparcelas consistiram de períodos de amostragem da forragem, variando de 0 a 60 dias após a colheita do milho. O consórcio não afetou a produtividade de grãos, acúmulo e partição de nutrientes no milho. Após a colheita de grãos, B. brizantha obteve a maior taxa de acúmulo de biomassa na safra (69 kg ha-1 dia-1) e safrinha (17 kg ha-1 dia-1). O acúmulo de nutrientes variou amplamente entre as espécies de Brachiaria e estação de cultivo: 0.2-1.2 kg ha-1 dia-1 para N; 0.01-0.07 kg ha-1 dia-1 para P; e 0.13-0.8 kg ha-1 dia-1 para K. Contudo, o maior acúmulo de nutrientes foi registrado para B. brizantha, seguida de B. ruziziensis e B. Convert. A curto prazo, o milho consorciado com Brachiaria na safra obteve maior efeito sobre a ciclagem de nutrientes e produção de biomassa. O consórcio entre milho e B. brizantha na safra foi a melhor opção para aumentar a produção de biomassa e a ciclagem de N, P e K.

ABSTRACT The corn biomass and nutrient dynamics may be altered when it is intercropped with Brachiaria (syn. Urochloa spp.). The present study aimed to investigate the dynamics of biomass, nitrogen (N), phosphorus (P) and potassium (K) for farming systems that produce corn intercropped with Brachiaria species. Field experiments were performed during the season and off-season, in a split-plot design. The main plots were composed of Brachiaria species (B. brizantha,B. ruziziensis and B. Convert) intercropped with corn, in addition to corn monocropping. The subplots consisted of three forage sampling periods, ranging from 0 to 60 days after the corn harvest. The intercropping arrangements did not affect the corn grain yield, nutrient accumulation and partitioning, relatively to the corn monocropping. After the grain harvest, B. brizantha achieved the greater biomass accumulation rate in both the season (69 kg ha-1 day-1) and off-season (17 kg ha-1 day-1). The nutrient accumulation ranged widely between the Brachiaria species and planting seasons: 0.2-1.2 kg ha-1 day-1 for N; 0.01-0.07 kg ha-1 day-1 for P; and 0.13-0.8 kg ha-1 day-1 for K. However, the greatest nutrient accumulation was found for B. brizantha, followed by B. ruziziensis and then B. Convert. In the short-term, corn intercropped with Brachiaria in the season showed the largest effect on the nutrient cycling and biomass yield. The intercropping between corn and B. brizantha in the season was the best way to enhance the biomass yield and the N, P and K cycling.

Resumen En fresa, se ha estudiado poco la fertilización potásica, lo que complica las estrategias de manejo para aumentar la productividad, y para la comprensión de la utilización de este nutriente en el cultivo de la fresa. El objetivo de este estudio fue evaluar la influencia de las fuentes y dosis de fertilizantes de potasio (K) en el rendimiento, la concentración de K, y las características agronómicas de la fruta de fresa cv. Camarosa, cultivada en condiciones de invernadero. El diseño experimental fue completamente al azar, con cuatro repeticiones, en un 6x3 factorial (seis tasas de K x tres fuentes de fertilizantes potásicos). Las fuentes utilizadas fueron sulfato de potasio, nitrato de potasio y cloruro de potasio aplicado en las siguientes tasas: 0, 60, 120, 180, 240 y 300 kg ha-1 de K2O. Las tasas crecientes de potasio permitieron un mayor contenido de potasio en hojas y frutos. El contenido de potasio más alto a nivel foliar más alto fue obtenido a través de KNO3 (11,70 g kg-1). El rendimiento, número de frutos por planta y la extracción de potasio por planta, aumentó linealmente con las dosis evaluadas y el peso medio del fruto a una dosis de 183 kg. ha-1. No hubo diferencia significativa entre las fuentes de potasio para el contenido foliar de potasio. La producción de fresa se maximiza mediante la fertilización potásica, independientemente del origen de la fuente.

Abstract In strawberry, potassium fertilization has been little studied, which difficult management strategies for an increasing yield and understanding the use of this nutrient in strawberry crop. The aim of this study was to evaluate the influence of sources and rates of potassium (K) fertilizers on yield, K level and agronomic traits of strawberry cv. Camarosa fruit, carried out under greenhouse conditions. A randomized in a completely block design with four replicates in a factorial arranged 6x3 (six rates of potassium x three sources of potassium fertilizers), was performed. Fertilizers sources used were as follows: potassium sulphate, potassium nitrate and potassium chloride in 0, 60, 120, 180, 240 and 300 kg ha-1 K2O doses. An increasing potassium rates have allowed a higher potassium content in leaves and fruits. A higher potassium content in leaves was obtained by KNO3 (11.70 g kg-1). Yield, fruit number per plant and potassium extraction per plant, increased linearly with the evaluated doses and fruit average weight at a dose of 183 kg ha-1. There was no significant difference among potassium content in leaves. Strawberry production is maximized through potassium fertilization, independent of the source origin.

Resumo: O objetivo deste trabalho foi avaliar métodos de implantação do consórcio milho e espécies forrageiras de Panicum spp. e os efeitos na produtividade do milho e no desenvolvimento das forragens. Dois experimentos com Panicum spp. foram conduzidos, um com 'Tanzania' e outro com 'Massai' em Piracicaba, SP, na safra 2012/2013. Em ambos os experimentos, os tratamentos foram: Panicum spp. semeado a lanço no momento da semeadura do milho; milho com Panicum spp. nas entrelinhas; Panicum spp. semeado com fertilizante; Panicum spp. semeado nas entrelinhas depois do estabelecimento do milho; Panicum spp. semeado a lanço depois do estabelecimento do milho; e milho solteiro. Para o milho, avaliaram-se a concentração de nitrogênio foliar, a altura de espigas e a produtividade de grãos. Para as cultivares de Panicum spp., avaliaram-se altura, massa seca, número de perfilhos e relação folha:colmo. Os métodos de implantação do consórcio avaliados não afetam o crescimento, a produtividade de grãos e a concentração foliar de N do milho. A implantação das cultivares de Panicum spp., quando o milho apresenta quatro folhas expandidas, reduz a massa seca e aumenta a relação folha:colmo das plantas forrageiras. A semeadura a lanço de Panicum spp., depois do estabelecimento do milho, não permite o estabelecimento adequado, com poucas plantas na área.

Abstract: The objective of this work was to evaluate methods of intercropping corn and Panicum spp. forages and their effects on corn yield and forage development. Two experiments with Panicum spp. were conducted, one with 'Tanzania' and other with 'Massai' in the municipality of Piracicaba, in the state of São Paulo, Brazil, in the 2012/2013 growing season. In both experiments, the treatments were: broadcast seeding of Panicum spp. at the same time of corn sowing; corn with Panicum spp. between rows; Panicum spp. sown with fertilizer; Panicum spp. sown between corn rows after corn establishment; broadcast seeding of Panicum spp. after corn establishment; and sole corn sowing. For corn, leaf nitrogen content, ear height, and grain yield were evaluated. For Panicum spp. cultivars, height, dry mass, tiller density, and leaf:stem ratio were evaluated. The intercropping establishment methods used do not affect corn growth, grain yield, and N leaf content. The seeding of both cultivars of Panicum spp. when corn plants had four expanded leaves reduces forage dry mass production and increases the leaf:stem ratio. The Panicum spp. broadcast method, performed after corn was established, does not allow appropriate establishment, with few plants in the area.

O objetivo deste estudo foi avaliar a eficiência do método dos discos foliares para estimar o índice de área foliar (IAF) de plantas de soja em comparação como método de fotos digitais. O delineamento experimental utilizado foi o de parcelas subdivididas com três repetições. Os IAFs calculados pelo método dos discos e das fotos digitais foram comparados em quatro estádios de desenvolvimento, e em quatro cultivares de soja (subparcelas). As cultivares de soja foram semeadas em Guarapuava, Estado do Paraná, Brasil, em três diferentes datas de semeadura (parcelas principais) na safra de 2010/2011. Análise de regressão foi feita para cada grupo de amostras, e a eficiência do método dos discos foi avaliado com base no coeficiente de determinação (R²), no F calculado e nos erros da interseção e da abscissa. As análises de regressão que compararam os dois métodos resultaram em F altamente significativos e baixos erros para todos os grupos de análises, o que mostrou a eficácia do método dos discos. Embora o valor de R² tenha sido elevado em todas as análises, os valores foram menores para as análises separadas por estádios de crescimento, especialmente para as amostras coletadas nos estádios V9 e R2. Os resultados indicaram que a área foliar específica calculada pelo método dos discos foliares foi menor do que a área foliar específica calculada pelo método das fotos digitais. O método dos discos foliares é um eficiente e robusto método para estimar o IAF de plantas de soja.

The objective of this study was to evaluate the efficiency of the leaf disc method for estimating the leaf area index (LAI) of soybean plants in comparison with the digital photo method. A split-plot experimental design was used with three replications. The LAIs calculated by the leaf disc and digital photo methods were compared at four growth stages in four soybean cultivars (subplot). These soybean cultivars were sowed in Guarapuava, Paraná State, Brazil, at three different sowing dates (main plot) in the 2010/2011 growing season. Regression analysis was used for each group of samples, and the efficiency of the leaf disc method was evaluated on the basis of the coefficient of determination (R²), the calculated F and the intersection and abscissa errors. The regression analysis that compared the two methods resulted in highly significant F values and low errors for all sample groups, which showed the effectiveness of the leaf disc method. Although the R² value was high for all of the analyses, the values were minor for the separate growth stage analysis, especially for the samples collected at the V9 and R2 stages. The results indicated that the specific leaf area calculated by the leaf disc method was lesser to the specific leaf area calculated by the digital photo method. The leaf disc method is an efficient and robust method for estimating the LAI of soybean plants.