ABSTRACT Variation in rainfall affects crops; therefore, agricultural practices become essential for forage production in semi-arid regions. This study aimed to evaluate the influence of different agricultural practices on phyllochron, structural characteristics of forage cactus and millet, and their relations with crop yield using the principal component analysis (PCA). The design was in randomized blocks, with six treatments: sole cropped cactus without straw mulching, sole cropped cactus with straw mulching, sole cropped millet without straw mulching, sole cropped millet with straw mulching, and cactus intercropping with millet, with and without straw mulching, each with four replicates. There were three cactus cycles and nine millet cycles (three cycles of cultivars BRS1501 and six of IPA Bulk-1-BF). Biometric parameters were evaluated monthly, while yield was determined after the crop harvest. Phyllochron was determined with the regression analysis. The PCA was applied to structural characteristics and yield. The systems adopted did not influence the structural characteristics of cactus and millet ( p > 0.05), except for cladode thickness, which increased with straw mulching. Phyllochron of the millet reduced when the crop was intercropped. The structural characteristics of cladode length, width, and thickness influenced crop yield, mainly in systems with straw mulching. Straw mulching and intercropping alter phyllochron of cactus and millet. The adoption of straw mulching has a more significant relationship with cactus yield, whereas biometric variables influence crop yield for millet, not the cropping system.

Resumo Objetivou-se avaliar o efeito de diferentes níveis de adubação potássica no crescimento inicial de clones de palma forrageira (Nopalea cochenillifera Salm Dyck). O experimento foi conduzido durante seis meses, disposto em delineamento em blocos ao acaso, em esquema fatorial 5x2, sendo cinco níveis de adubação potássica (0, 250, 500, 750 e 1000 Kg de K2O ha-1) e dois clones de palma forrageira (Doce Gigante e Doce Miúda), com quatro repetições. Foi plantado um cladódio por vaso (unidade experimental) com capacidade para 7 kg de solo (24 x 17 x 23 cm). Ao longo do período experimental, foram avaliadas as características estruturais das plantas, tais como altura e largura de planta, comprimento, largura, espessura e perímetro de cladódio, bem como contabilização do número de cladódios total e por ordem de surgimento. Ao final do experimento avaliou-se a biomassa, para determinação do rendimento de massa fresca (MV) e seca (MS) da parte aérea e do sistema radicular. Após a determinação de MS, determinou-se o teor potássico nos tecidos vegetais. Os dados foram submetidos a ANOVA e, caso necessário, ao teste de Tukey a 5% de significância. A adubação potássica e os clones de palma forrageira não exerceram influências significativas nas variáveis avaliadas durante a condução experimental. A adubação potássica não influencia as características estruturais, produtivas e teor potássico no crescimento inicial de clones de Nopalea cochenillifera.

Abstract The objective was to evaluate the effect of different levels of potassium fertilization on the initial growth of forage cactus (Nopalea cochenillifera Salm Dyck) clones. The experiment lasted six months, arranged in a randomized block design, in a 5 x 2 factorial scheme, with five levels of potassium fertilization (0, 250, 500, 750, and 1,000 kg of K2O ha-1) and two forage cactus clones (Little Sweet and Giant Sweet), with four replicates. One cladode was planted per pot (experimental unit) with a capacity of 7 kg of soil (24 x 17 x 23 cm). During the experimental period, the plants' structural characteristics were evaluated, such as plant height and width, length, width, thickness, and perimeter of the cladode, as well as accounting for the number of total cladodes, and in order of appearance. At the end of the experiment, biomass was evaluated to determine the fresh matter (FM) and dry matter (DM) yield of the aerial part and the root system. After determining the DM, the potassium content in the plant tissues was determined. The data were submitted to ANOVA and, if necessary, to the Tukey test at a 5% significance level. The potassium fertilization and the forage palm clones did not exert influences based on the variables evaluated during the experimental conduction. Potassium fertilization does not influence the structural and productive characteristics and the potassium content in the N. cochenillifera clones' initial growth.

Resumo Objetivo A urbanização leva a mudanças rápidas na estrutura e função do ecossistema. Terras úmidas em câmpus universitários sujeitos ao desenvolvimento da urbanização podem ser usados como estudos de caso de pesquisa aquática multidisciplinar e boas práticas ambientais que promovam a sustentabilidade. Métodos Foi realizado um estudo paleolimnológico em um lago semiartificial em um campus universitário no sul do Brasil para inferir impactos históricos e mudanças ecológicas desde a década de 1970 por meio de abordagens complementares: dados históricos, nutrientes, isótopos estáveis δ13C e δ15N, diatomáceas, microplásticos e análise da comunidade microbiana associada. Resultados O processo de eutrofização começou a se intensificar após o uso noturno por aves aquáticas de árvores como poleiros, e especialmente após o estabelecimento de construções ao longo das margens com fossa séptica de esgoto sanitário, que ocasionalmente transbordava e carreava material para o lago. Ao longo de décadas, identificamos um processo limnológico de hipertrofização que induziu a florações recorrentes de cianobactérias e proliferação maciça de macrófitas, juntamente com mudanças isotópicas e ocupação de algas com várias transições entre estados alternativos de lagos rasos. Tal processo limnológico foi claramente espelhado nas tendências de eutrofização paleolimnológica e mudanças isotópicas da matéria orgânica sedimentar. A deposição de microplásticos foi detectada como proxy para a intensificação da urbanização especialmente durante a construção das instalações da Universidade. Conclusões O uso combinado de dados paleolimnológicos e limnológicos históricos representa uma abordagem poderosa para identificar os impactos naturais e culturais no lago e identificar estratégias de manejo baseadas em tais informações científicas.

Abstract Aim Urbanization leads to rapid changes in ecosystem structure and function. Wetlands on university campuses under urbanization pressure could be used as case studies of multidisciplinary aquatic research and good environmental practices promoting sustainability. Methods A paleolimnological study was undertaken in a semi-artificial lake on a university campus in southern Brazil to trace historical impacts and ecological changes back to the mid-1970s through complementary approaches: historical data, nutrients, δ13C and δ15N stable isotopes, diatoms, microplastics and associated microbial community analysis. Results The eutrophication process started to intensify after the lake was used for nocturnal roosting by waterbirds, and especially after the establishment of constructions along the margins with septic tank sanitary sewage, which eventually spilled and leached into the lake. Over decades, we identified a limnological hypertrophication process leading to recurrent cyanobacterial blooms and massive macrophyte proliferation coupled with changes in isotopic ratios and algal occupation with several transitions between shallow lake alternative states. Such a limnological process has resembled the paleolimnological eutrophication trends and isotopic changes in sedimentary organic matter. The microplastic deposition was detected as a proxy for the intensification of urbanization, especially during the construction of the University facilities. Conclusions The combined use of paleolimnological and historical limnological data represents a powerful approach for inferring both natural and cultural impacts on the lake, and identifying management strategies based on such scientific information.

ABSTRACT The use of irrigation can improve the productivity and nutritional quality of the forage cactus in environments with a water deficit, resulting in profit to the producer. The productive performance, bromatological composition and economic benefits of using irrigation were investigated in this study with forage cactus clones regulated deficit irrigation (RDI). The study was conducted in an experimental design of randomised blocks, in a factorial scheme with subdivided plots. The plots consisted of water regimes based on the crop evapotranspiration (ETc) (rainfed, 40, 80 and 120% ETc). The cactus clones [‘Miúda’ (MIU), ‘Orelha de Elefante Mexicana’ (OEM) and ‘IPA Sertânia’ (IPA)] comprised the subplots. The total number of cladodes per plant, the fresh and dry matter yields and the bromatological composition were evaluated. Economic viability was assessed using the net revenue and benefit to cost ratio (BCR). The irrigation depths did not increase the yield of the clones. The OEM clone showed 276 and 343% greater fresh and dry matter production, respectively, when compared to the IPA clone; however, when compared with the MIU clone, it was 63%, both on a fresh and dry matter production. The water regimes had no effect on the nutritional quality of the cactus. Only IPA showed no profit during the first cycle (BCR < 1). It can be concluded that planting one irrigated hectare with the OEM and MIU clones offer economic returns starting from the first production cycle (18 months).

BRS Esteio is a common bean cultivar with black grains of excellent cooking quality, suited for cultivation in 21 Brazilian States. In 77 trials of Value for Cultivation and Use, the cultivar had a normal cycle (90 days), an average yield of 2,529 kg ha-1, which is 8.1% higher than that of the control cultivars, a high yield potential (4,702 kg ha-1), upright growth, tolerance to lodging, and moderate resistance to anthracnose.

To apply high amounts of K to the soil there must be adequate quantities of Mg, thus avoiding the rise of physiological disorders in the banana plant which appear as Mg-induced deficiency symptoms. The purpose of this study was to evaluate the effects of application of K and Mg on the vegetative development and yield of the banana cv. "Prata Anã'. Treatments were distributed in a randomized block design in a 3 x 5 factorial arrangement, corresponding to three doses of potassium (0, 800 and 1200 kg ha-1 year-1) and five doses of magnesium (0, 60, 120, 240 and 480 kg ha-1 year-1), with three replicates. The sources of potassium and magnesium were potassium chloride and magnesium sulfate, respectively. Application of K, regardless of the cycle, increased the bunch weight, the number of banana fruits per bunch, the number of hands per bunch, and the weight and diameter of the middle fruit of the banana plant. Increasing doses of Mg applied to the soil reduced the weight of the bunch in the first cycle; and with increasing doses of K there was an increase in the leaf content of K and Ca, with a decrease in the leaf content of Mg and B in the banana cv. 'Prata Anã'.

Para que sean aplicadas grandes cantidades de K en el suelo, hay necesidad que los niveles de Mg sean adecuados en lo mismo, evitando así la aparición de desórdenes fisiológicos en el banano, expresado en los síntomas de deficiencia inducida de Mg. El objetivo de este estudio fue evaluar los efectos de la aplicación de K y Mg en el desarrollo y la productividad del banano'Prata Anã'. Los tratamientos se dispusieron en un diseño de bloques al azar con un factorial 3 x 5, que corresponden a tres niveles de potasio (0, 800 y 1200 kg ha-1 año-1) y cinco dosis de magnesio (0, 60, 120, 240 y 480 kg ha-1 año-1), con tres repeticiones. Las fuentes de potasio y magnesio fueron, respectivamente, cloruro de potasio y sulfato de magnesio. La aplicación de K, independiente del ciclo, aumentó el peso del racimo, número de frutos por racimo, el número de manos por racimo, la masa y el diámetro del fruto central de la banana. Dosis crecientes de Mg aplicadas al suelo reducen la masa del racimo en el primer ciclo. Con el incremento de las dosis de K hubo un aumento en K y Ca foliar, con una reducción en Mg y B foliar del banano 'Prata Anã'.

Phosphorus critical level is influenced by soil physical and chemical attributes and characteristics of each plant species. The aim of this study was to determine the critical levels of phosphorus in soil and plants of Bracharia brizantha cv. Marandu and Panicum maximum cv. Tanzânia, using different doses and sources of P. The work was carried out under green house conditions using soil samples with different clay contents. In the experiment with the cultivar Marandu were applied 20 treatments in factorial scheme (5 x 4), corresponding to five P doses (0, 100, 200, 400 and 800 mg dm-3) and four P sources (monoammonium phosphate, triple superphosphate, simple superphosphate and Gafsa reactive rock phosphate). In the experiment with the cultivar Tanzânia was also applied magnesium termophosphate. The treatments were distributed in a complete block design with four replicates. No differences were observed among the effects of monoammonium phosphate, triple superphosphate, simple superphosphate, Gafsa reactive rock phosphate and magnesium termophosphate on the production of dry matter of grasses Marandu and Tanzânia. The triple superphosphate provided the lowest values of P critical level in soil, the Gafsa reactive rock phosphate provided the lowest values of P critical levels in grasses shoot.

El nivel crítico de fósforo se ve influenciado por los atributos físicos y químicos del suelo y las características de cada especie vegetal. El objetivo de este estudio fue determinar los niveles críticos de fósforo en el suelo y las plantas de Bracharia brizantha cv. Marandu y Panicum maximum cv. Tanzânia, utilizando diferentes dosis y fuentes de P. El trabajo se llevó a cabo bajo condiciones de invernadero utilizando muestras de suelo con diferentes contenidos de arcilla. En el experimento con la hierba Marandu, 20 tratamientos se aplicaron en un diseño factorial (5 x 4), correspondiente a cinco niveles de fósforo (0, 100, 200, 400 y 800 mg dm-3) y cuatro fuentes de fósforo (fosfato monoamónico, superfosfato triple, simple superfosfato y fosfato natural de Gafsa). En el experimento con la hierba Tanzânia, se aplicó también termofosfato magnesiano. Los tratamientos se dispusieron en un diseño de bloques al azar con cuatro repeticiones. No se observaron diferencias entre los efectos de fosfato monoamónico, superfosfato triple, simple superfosfato, fosfato natural de Gafsa y termofosfato magnesiano en la producción de materia seca de gramíneas Marandu y Tanzânia. El súper triple proporciona valores más bajos de nivel crítico de P en el suelo, al paso que el fosfato natural de Gafsa proporcionó más bajos niveles críticos de P en los brotes de hierbas.

A morfologia do sistema radicular é uma das características importantes na tolerância de plantas à deficiência hídrica. Assim, objetivou-se verificar aspectos morfológicos de importância, quanto à tolerância à deficiência hídrica do sistema radicular de cultivares de arroz de terras altas, cultivadas sob deficiência hídrica, em condições de casa-de-vegetação, para discriminar linhagens para regiões com distribuição irregular de chuvas. Para tanto, foram semeadas 37 cultivares com ampla variabilidade genética, em tubos de PVC (25 cm de diâmetro e 80 cm de altura) com solo, submetidas, após a emissão das panículas, a dois regimes hídricos: sem e com deficiência hídrica (reposição de, aproximadamente, 50% da água evapotranspirada). A densidade radicular foi avaliada na colheita dos grãos (de 20 cm em 20 cm), da superfície até 80 cm de profundidade, tendo as cultivares diferido quanto a esta característica. As cultivares Muruim Branco, Cano Roxo, Amarelão/Douradão e Arroz Agulhinha apresentaram alta densidade radicular, tanto sob deficiência como sob adequada disponibilidade hídrica. A densidade radicular de cultivares de arroz de terras altas, avaliada em colunas de solo, se relacionou, positivamente, com a tolerância à deficiência hídrica destas cultivares, em condições de campo. Esta metodologia constitui-se em importante ferramenta de fenotipagem, para tolerância à deficiência hídrica em arroz.

The root system morphology is one of the most important characteristics in the adaptation of plants to water stress. So, the objective of this study was to analyse important morphologic aspects, regarding the drought tolerance of the root system of upland rice cultivars cultivated under water stress conditions in a greenhouse, in order to discriminate lines to areas with uneven rainfall distribution. Thus, 37 cultivars with broad genetic divergence were sown in PVC tubes (25 cm diameter and 80 cm height) filled with soil, under two hydric regimes: without and with (reposition of about 50% of evapotranspired water) water stress, applied after the panicle emergence. Root density, evaluated at harvest from surface to 80 cm depth, at 20 cm intervals, differed among the cultivars. Muruim Branco, Cano Roxo, Amarelão/Douradão, and Arroz Agulhinha cultivars showed high root density under water deficit as well as under adequate water availability. The root density of upland rice cultivars, measured in soil columns, was positively related to the drought tolerance of these cultivars, under field conditions. This methodology can be considered a valuable technique for screening upland rice cultivars for drought tolerance.

Os coeficientes de digestibilidade aparente de matéria seca (CDAMS), matéria orgânica (CDAMO), proteína bruta (CDAPB), extrato etéreo (CDAEE), carboidratos totais (CDACHOT), carboidratos não-fibrosos (CDACNF), fibra em detergente neutro (CDAFDN) e fibra em detergente ácido (CDAFDA) foram determinados para avaliar o efeito de níveis crescentes de energia na dieta. A estimativa de digestibilidade aparente dos nutrientes, utilizando-se os métodos de coleta total de fezes, e a estimativa da produção de matéria seca fecal (PMSF), empregando-se a fibra em detergente ácido indigestível (FDAI) como indicador interno, também foram comparadas. Utilizaram-se 18 ovinos Santa Inês, machos não-castrados, com idade média de seis meses e peso vivo médio de 20 kg, alimentados com dietas contendo 2,42; 2,66; e 2,83 Mcal de energia metabolizável/kg de matéria seca, distribuídos em delineamento em blocos casualizados, com seis repetições. A estimativa da PMSF, utilizando-se a FDAI, foi efetuada para posterior comparação com a PMSF, determinada pelo método de coleta total de fezes. Para os CDAMS, CDAMO, CDAEE, CDACHOT e CDACNF, houve efeito linear crescente com o aumento nos níveis de energia; no entanto, para os CDAFDN e CDAFDA, observou-se efeito linear decrescente e, para o CDAPB, não houve efeito com o aumento nos níveis de energia da dieta. Conclui-se que a FDAI pode ser utilizada como indicador interno para estimativa do coeficiente de digestibilidade em ovinos.

The coefficients of apparent digestibility of dry matter (CADDM), organic matter (CADOM), crude protein (CADCP), ether extract (CADEE), total carbohydrates (CADTCHO), nonfiber carbohydrates (CADNFC), neutral detergent fiber (CADNDF) and acid detergent fiber (CADADF) were determined to evaluate the effect of the increasing dietary energy levels. The estimate of the apparent digestibility of the nutrients, using the method of fecal total collection, and the estimate of fecal dry matter production (FDMP), by the indigestible acid detergent fiber (IADF), as internal marker, were also compared. Eighteen Santa Inês sheep (averaging live weight of 20 kg and six months old) were full fed diets with 2.42; 2.66 and 2.83 Mcal metabolizable energy/kg of dry matter and allotted to a randomized block design, with six replicates. FDMP estimate, using IADF, was performed to be compared with the FDMP, determined by the total feces collection. It was observed increasing linear effect for CADDM, CADOM, CADEE, CADTCHO and CADNFC, as the the dietary energy levels increased. However, CADNDF and CADADF decreased linearly and, for CADCP, there was no effect, as the the dietary energy levels increased. IADF can be used as internal marker to estimate the coefficient of apparent digestibility in sheep.