Coastal Tablelands Research Articles

Áreas de Lagoas Intermitentes em Tabuleiros Costeiros do Recôncavo da Bahia: Gênese, Caracterização e Classificação dos Solos

RESUMO Os Tabuleiros Costeiros são áreas com relevo aplainado cortadas por vales, que apresentam predominantemente Argissolos Amarelos e Latossolos Amarelos. Contrastando com essa paisagem, existem depressões circulares conhecidas por lagoas, que imprimem nova dinâmica na formação dos solos, em razão da presença intermitente de água ao longo do ano. Os solos dessas áreas ainda são pouco conhecidos, o que implica na possibilidade de uso e manejo inapropriado. Objetivou-se descrever morfologicamente, caracterizar física e quimicamente e classificar os solos existentes em duas dessas áreas de lagoas, visando obter informações para subsidiar um manejo mais adequado. Constatou-se a presença de solos classificados como Organossolo Háplico Sáprico sódico, Gleissolo Háplico Sódico vertissólico (dois perfis), Gleissolo Háplico Sódico típico, Gleissolo Sálico Sódico vertissólico, Planossolo Háplico Eutrófico solódico e Vertissolo Hidromórfico Sódico salino. Esses solos apresentaram cores acinzentadas, típicas do hidromorfismo intermitente observado nas áreas, textura predominantemente mais fina, chegando às classes texturais argilosa e muito argilosa, e estrutura predominantemente maciça, aspectos que prenunciam baixa aeração, o que, juntamente com a alta porcentagem de saturação por sódio, indicam grandes limitações físicas e químicas. Esses aspectos recomendam seu uso como áreas de preservação permanente.

FORMAS DE FERRO, SILÍCIO E, OU, ALUMÍNIO NA GÊNESE DE FRAGIPÃS E HORIZONTES COESOS DOS TABULEIROS COSTEIROS

Na unidade geomorfológica dos Tabuleiros Costeiros dominam os solos com horizontes coesos, e alguns deles têm a presença de horizontes cimentados comumente do tipo fragipã. Esses horizontes interferem na dinâmica da água, no crescimento de raízes e, consequentemente, na nutrição mineral de plantas. O objetivo deste trabalho foi avaliar, por meio da dissolução seletiva, a participação de formas de Fe, Si e, ou, Al na coesão e, ou, cimentação de fragipãs e horizontes coesos em Argissolos e Espodossolos da região dos Tabuleiros Costeiros do sul da Bahia e norte do Espírito Santo. Para isso, foram realizadas extrações seletivas de Fe, Si e Al por ditionito-citrato-bicarbonato de sódio (DCB) e oxalato ácido de amônio. Os maiores teores de Fe, Si e, principalmente, Al extraídos por oxalato de amônio nos fragipãs sugerem que, na gênese desses horizontes, formas de baixa cristalinidade desses elementos agem como cimentantes químicos. As dissoluções seletivas não evidenciaram a participação de formas de alta ou baixa cristalinidade de Fe, Si e, ou, Al na gênese dos horiozontes coesos em solos dos Tabuleiros Costeiros. Os Argissolos Amarelos apresentaram goethitas com alta substituição isomórfica de Fe por Al, condizente com o ambiente de forte intemperização, não redutivo e pH ácido onde esses solos se encontram nos Tabuleiros Costeiros. A substituição isomórfica de Fe por Al nos óxidos de Fe cristalinos apresentaram relação com o grau de cristalinidade e teor de Fe obtido na primeira extração com o DCB.

Sources and doses of nitrogen in the productivity of Marandu-grass

The objective of this study was to evaluate the response of sources and levels of nitrogen on productivity of Brachiaria brizantha. Marandu at conditions of the Coastal Table lands of Piaui. The work was conducted to field, from May to July 2013 at the Experimental Station of Embrapa Meio-Norte, located in the city of Parnaíba, Piauí. The treatments consisted of the combination of two nitrogen sources (ammonium sulphate and urea) and three levels of nitrogen 19.56; 39.12 and 58.68 kg/ha/cut corresponding to 170, 340, 510 kg/ha/year, according to the randomized complete block design with three replications. Three cuts with an interval of 42 days each. Nitrogen fertilization positively influenced the yield of total dry matter. Leaf/stem ratio and the efficiency of nitrogen utilization responded negatively to increases nitrogen.

GEOMORFOLOGIA ESTRUTURAL DO GRÁBEN DO RIO MAMANGUAPE E ADJACÊNCIAS – ESTADO DA PARAÍBA, BRASIL

This present work is based on the morphostructural characterization of Mamanguape River graben, located in the north portion of the eastern border of the State of Paraíba, northeast of Brazil. By using detailed mapping, we aim to produce quantitative and morphological information, conditioned by the present structural framework of Mamanguape River graben and its adjacencies. For the elaboration of the cartographic products, three topographic maps, with scale 1:25.000 and 10m equidistance interval of the contour-lines, which covers the whole area at issue, were entirely digitalized and vectorized. With this scale, it was possible to make an inedited detailed mapping of Mamanguape River graben and its adjacencies. By using the cartographical products generated, it was possible to observe and quantify the morphological and morphostructural aspects in the area, such as: discrepant altimetricdifferencies between its north and south sectors, that run along the adjacency of the graben, abrupt slopes with more marked declivity on the north sector, hogbacks on shoulders, drainage network assimetric patterns and anomalous orientations and abrupt inflexions of various fluvial canals and accelerated backings of drainage headwaters. These characteristics point to the existence of a morphostructural control in the area, once only the climatic factor would make it impossible the formation of the morphological pattern found on it.Key words: Mamanguape river graben, Barreiras Formation, coastal tableland.

Load-bearing capacity and its relationships with the physical and mechanical attributes of cohesive soil

In north-eastern Brazil, sugarcane is mostly explored in coastal tablelands, where the soil has a particular feature that is called the “cohesive character”. This study aimed to analyse the relationship between physical properties of the soil and the preconsolidation pressure (σp) variation in cohesive soil. The work was performed in the Ultisol area, where sugarcane is cultivated. On a single plot, 42 points were delimited to obtain samples at depths of 0.10–0.13 and 0.30–0.33m, which resulted in 84 samples in total. Deformed and undeformed samples were collected to measure the following variables: water content, bulk density, soil penetration resistance, organic carbon, clay content, liquid limit, plastic limit, and the σp. For each layer, a principal component analysis was performed. After the scores for those components were obtained, a linear multiple regression model was fitted for the σp data to establish the relationships between the variables. The water content and the organic carbon showed negative relations with σp. The bulk density, soil penetration resistance, clay content, liquid limit and plastic limit were positively related. Higher σp values are associated with higher values of bulk density, soil penetration resistance, clay content, liquid limit and plastic limit, and smaller values are linked to an increase in water content and organic carbon.

THE RESPONSE OF SUGARCANE TO TRASH RETENTION AND NITROGEN IN THE BRAZILIAN COASTAL TABLELANDS: A SIMULATION STUDY

SUMMARYTo evaluate the impact of trash management on sugarcane production and N fertiliser requirements in environmental conditions of Brazilian coastal tablelands, a simulation was conducted with APSIM-Sugar cropping systems model. The model was parameterised for, and validated against results from a long term (over 23 years) experiment comparing the system-burnt trash and green cane trash blanketing (GCTB), in Linhares-ES. Simulations were conducted over two crop cycles (14 years) with different management (100%, 75%, 50%, 25% GCTB and burnt trash), and N fertiliser rates from 0 to 240 kg ha−1 (in 40 kg ha−1 increments) on the ratoon crops, and 75% of these rates on the plant crops. Measured cane yields and soil carbon were simulated well by the model. The RMSE (root mean square error) of predictions in burnt and GCTB treatments were 14.02 Mg ha−1 and 13.45 Mg ha−1 for yield, and 0.09 and 0.13% for soil carbon. In the simulation, the cane yield responded positively to the GCTB systems. Optimum N rates were higher in the 100%, 75% and 50% GCTB than with burnt trash and 25% GCTB reflecting the greater yields under GCTB systems. The response to trash retention was dependent on N fertiliser, and it was smaller or even negative at lower N rates. With adequate N, the positive responses were predicted to occur in all crops after the imposition of GCTB system. The removal of any proportion of the trash reduced the potential sugarcane yield. The simulations showed that average environmental losses of N are likely to be greater from trash-retained systems at all N fertiliser rates.

In vitrogermination and viability of pollen grain of coconut accessions

Storage as a means of maintaining the pollen viability is important for the preservation of the genetic variability, facilitates the exchange of germplasm and greatly contributes to the generation of variability obtained from artificial crosses, increasing the efficiency of breeding programs. The objective of this study was to select different culture media for the in vitro germination of pollen grain of dwarf and tall coconut accessions, as well as to determine the viability of pollen grain at room temperature conditions. For this purpose, Brazil Green Dwarf (BGD) and Brazilian Tall (BRA) pollen grains derived from the Coconut Active Germplasm Bank of Embrapa Coastal Tablelands Sergipe were used. To evaluate the effect of different culture media on the in vitro germination of pollen grains of anão verde do Brasil de Jiqui (AVeBrJ) and gigante do Brasil Praia do Forte (GBrPF) accessions, they were inoculated on to Petri dishes containing 2 ml of culture media. The pollen viability was assessed by staining with 1% acetic carmine and in vitro germination at 0, 24, 48 and 72 hours. The culture medium of Lora is suitable to assess the in vitro germination of pollen grain of the AVeBrJ and GBrPF accessions. The pollen grain of the AVeBrJ accession showed intermediate viability (66.87%) at room temperature up to 23.14 hours by in vitro germination. The pollen grain of the GBrPF accession showed high viability, above 70%, at room temperature up to 120 hours by in vitro germination.

Genesis of cohesive soil horizons from north-east Brazil: role of argilluviation and sorting of sand

Cohesive horizons are widespread along the Brazilian coastal tablelands and, despite their importance to soil management under intensive cultivation, their genesis remains, in many aspects, controversial. Studies diverge and indicate the participation of different mechanisms in the formation of these soil horizons. Although clay illuviation has been considered as one of the processes determining the formation of this soil attribute, recent studies suggest a limited participation of this soil process. The aim of the present study was to evaluate the relative contribution of argilluviation and sorting of sand to the genesis of cohesive horizons in an Ultisol toposequence from a toposequence from north-east Brazil. Soil samples were collected from cohesive and non-cohesive horizons from four soil profiles. We determined bulk soil density (BD), penetration resistance (PR), particle size distribution and the percentage of different sand fractions. The sand fractionation data were treated statistically to obtain different grain size parameters, such as mean grain size, sorting and kurtosis. An additional micromorphological study was performed on cohesive and non-cohesive horizons. The lowest BD and PR were recorded in non-cohesive horizons (1.53 Mg m–3 and 0.74 MPa, respectively), whereas significantly higher values of BD (1.66–1.80 Mg m–3) and PR (2.61–7.71 MPa) were observed in cohesive horizons. Thin sections of cohesive soil horizons showed a significant reduction in void sizes and interconnecting pores compared with non-cohesive soil horizons. The higher values of BD and PR observed in the cohesive horizons are apparently related to this poorly interconnected void network. Textural pedofeatures observable with optical microscopy, which indicate argilluviation, were only found in one cohesive horizon. Sand fractionation showed a predominance of medium and fine sand fractions and indicated the dominance of poorly selected sand in cohesive horizons, probably causing the higher BD and PR values. However, the presence of textural pedofeatures (clay coatings) in one of the cohesive horizons studied may indicate a combined contribution of sand heterogeneity and argilluviation in the genesis of these horizons. Overall, the results of the present study showed that subtle variations in the distribution of basic soil components (i.e. particle size fractions) may determine the formation of cohesive horizons and thus must be taken into account in future studies aiming to predict their spatial distribution and to establish more efficient management strategies.

Index of soil physical quality of hardsetting soils on the brazilian coast

Many soils have a hard-setting behavior, also known as cohesive or "coesos". In such soils, the penetration resistance increases markedly when dry and decreases considerably when moist, creating serious limitations for plant emergence and growth. To evaluate the level of structure degradation in hard-setting soils with different texture classes and to create an index for assessing soil hardness levels in hard-setting soils, six soil representative profiles were selected in the field in various regions of Brazil. The following indices were tested: S, which measures soil physical quality, and H , which analyzes the degree of hardness and the effective stress in the soil during drying. Both indices were calculated using previously described functions based on data from the water-retention curves for the soils. The hard-setting values identified in different soils of the Brazilian Coastal Tablelands have distinct compaction (hardness) levels and can be satisfactorily measured by the H index. The S index was adequate for evaluating the structural characteristics of the hard-setting soils, classifying them as suitable or poor for cultivation, but only when the moisture level of the soil was near the inflection point. The H index showed that increases in density in hard-setting soils result from increases in effective stress and not from the soil texture. Values for Bd > 1.48 kg dm-3 classify the soil as hard-setting, and the structural organization is considered "poor".

Edaphic fauna in wooded systems of conilon coffee in coastal tableland soil

The Espirito Santo is the biggest Brazilian producer of coffee conilon, highlighting the predominance of monocultures in the northern region. Some farmers insert tree species in plantations, modifying the soil and climate conditions of the agroecosystems. However, studies on the effect of this practice in relation to soil fauna are still incipient. The objective of this work was study the effect of forestation in conilon coffee plantations on meso-and macrofauna of the soil in the northern of Espirito Santo state. In the rainy and dry seasons, the meso-and macrofauna was sampled using pitfall traps installed in three coffee plants agroecosystems: monoculture, intercropped with Australian cedar (Toona ciliata M. Romer), and intercropped with teak (Tectona grandis L. f.). Subsequently the organisms of fauna were identified in major taxonomic groups. We collected a total of 10,451 invertebrates on the soil surface, belonging to 20 taxonomic groups, mostly during the rainy season. Regardless of the period and system, Collembola and Formicidae were the predominant groups on the soil surface. The richness of taxonomic groups was higher during the dry season in all agroecosystems. In the rainy season, the Shannon diversity index (H’) and Uniformity index (U) were higher (p <0.10) in consortium with cedar compared to other systems, with values of 0.45 and 0.68, respectively. The forestation of coffee plantation with Australian cedar provides greater availability of resources (feeding and habitat, for example) to soil fauna, being less vulnerable to seasonal climate changes.

English

The banana (Musa sp.) crop is notable for its social and economic importance in tropical and subtropical regions of world. In Brazil, despite being a main banana producer, its production is considered low, mainly due to water and nutrient shortages in soils. This fact motivated this study; so, it aimed to evaluate chlorophyll and macronutrients content in leaf tissue of banana &lsquo;Prata-An&atilde;&rsquo; (AAB) under fertigation with doses of nitrogen and potassium. It were evaluated chlorophyll a, b and total and leaf contents of nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg) and calcium (Ca) in banana trees grown in an Ultisol on the coastal tablelands of Sergipe State, Brazil. The experiment was conducted in the field, in a 42 factorial with four randomized blocks. Two factors with four levels were tested: nitrogen (0; 350; 700 and 1050, in kg ha-1 of N, as urea) and potassium (0; 400; 800 and 1200, in kg ha-1 of K2O, as potassium chloride). Increasing N applied through irrigation enhances leaf nitrogen until approximately 631.08 kg ha-1 of N, while chlorophyll total remains constant after 250 kg ha-1. Phosphorus and calcium are increased due to high doses of N, however, magnesium and potassium in the leaves are reduced. High doses of K increase leaf content of K until estimated dose of 698.07 kg ha-1 and reduce calcium and magnesium of banana &lsquo;Prata-An&atilde;&rsquo;. &nbsp; Key words: Musa sp., mineral fertilizer, nutrition, photosynthetic pigments, nutrient splitting.&nbsp

&lt;b&gt;Pollen grain viability of coconut accessions at low temperatures

The aim of this study was to evaluate the storage potential of the pollen grains of Brazil Green Dwarf (BGD), Brazilian Tall (BRA) and Cameroon Red Dwarf (CRD) coconut accessions under different storage conditions. Representative plants of BGD, BRA and CRD accessions were selected from the Coconut Active Germplasm Bank of Embrapa Coastal Tablelands. The pollen grains were collected, placed in cryotubes and maintained under the following storage conditions: T1, refrigerator (-4°C); T2, freezer (-20°C); T3, ultra-freezer (- 80°C) and T4, liquid nitrogen (-196°C). The pollen grain viability was determined by staining with 1% acetic carmine and in vitro germination in a Lora culture medium at 30 and 60 days after the storage. Storage under refrigerator (-4°C), freezer (-80°C) and liquid nitrogen (-196°C) conditions promoted a better pollen grain viability of the Brazilian Tall coconut accession. Storage under freezer (-20°C) and liquid nitrogen (-196°C) conditions promoted a better pollen grain viability of the Cameroon Red Dwarf coconut accession. Storage under freezer (-20°C and-80°C) and liquid nitrogen (-196°C) conditions promoted a better pollen grain viability of the Brazil Green Dwarf coconut accession. The pollen grain viability of the Brazilian Tall coconut accession is stable after 30 and 60 days of storage.

Structural quality of polyacrylamide-treated cohesive soils in the coastal tablelands of Pernambuco

Water-soluble polymers are characterized as effective flocculating agents due to their molecular features. Their application to soils with horizons with structural problems, e.g, a cohesive character, contributes to improvements in the physical quality and thus to the agricultural suitability of such soils. The purpose of this study was to evaluate the structural quality of soils with cohesive horizons of coastal tablelands in the State of Pernambuco treated with polyacrylamide (PAM) as chemical soil conditioner. To this end, three horizons (one cohesive and two non-cohesive) of a Yellow Argisol (Ultisol) were evaluated and to compare cohesive horizons, the horizon of a Yellow Latosol (Oxisol) was selected. The treatments consisted of aqueous PAM solutions (12.5; 50.0; 100.0 mg kg-1) and distilled water (control). The structural aspects of the horizons were evaluated by the stability (soil mass retained in five diameter classes), aggregate distribution per size class (mean weight diameter- MWD, geometric mean diameter - GMD) and the magnitude of the changes introduced by PAM by measuring the sensitivity index (Si). Aqueous PAM solutions increased aggregate stability in the largest evaluated diameter class of the cohesive and non-cohesive horizons, resulting in higher MWD and GMD, with highest efficiency of the 100 mg kg-1 solution. The cohesive horizon Bt1 in the Ultisol was most sensitive to the action of PAM, where highest Si values were found, but the structural quality of the BA horizon of the Oxisol was better in terms of stability and aggregate size distribution.

English

The sweet potato, Ipomoea batatas (L.) Lam has its origin in Tropical America. In Sergipe State (Brazil), its production is very important, and to explore its potential in local agriculture in the State, the Embrapa Coastal Tableland created a collection with 52 accessions located in Umba&uacute;ba City. Some accessions were from germplasm belonging to Embrapa vegetables and others from local farmers of Sergipe. Here, we provide the first data on the genetic diversity and structure of sweet potato collection of SPGB using random amplified polymorphic DNA (RAPD) markers. RAPD data were used to determine genetic variability via a model-based Bayesian procedure (structure) and molecular variance analysis (AMOVA). In addition, Shannon index, genetic diversity and Jaccard coefficients were also estimated. &nbsp;RAPD was efficient for the analysis of genetic diversity to identify groups and measure the genetic distance between accessions. The markers showed that the collection had a high level of polymorphism. By UPGMA, we separated three groups of genotypes and identified two reconstructed populations by structure software. &nbsp; Key words: Ipomoea batatas, cultivars, accessions.

Response of banana genotypes to yellow Sigatoka in coastal tablelands of Sergipe, Brazil

Brazil has low availability of productive commercial cultivars with appropriate size and resistance to yellow Sigatoka. The objective of this study was to evaluate the behavior of different banana genotypes against yellow Sigatoka at conditions of Coastal Tablelands of Sergipe. The experiment was conducted at the Experimental Field of Embrapa Tabuleiros Costeiros, municipality of Nossa Senhora das Dores. The experimental design was randomized blocks design with 22 genotypes and three replications, six plants per plot. The genotypes tested were: Enxerto-33, Japira-106, FHIA-23, YB42-17, YB42-47, FHIA-18, PA42-44, PA94-01, PV79-34, Pacovan Ken, Pacovan, Prata-Anã, Maravilha, Garantida, Princesa, Tropical, Maçã, Grande Naine, FHIA-02, Caipira, Bucaneiro and Thap Maeo. The severity of yellow Sigatoka was evaluated at 60, 270 and 420 days after planting (DAP) (from July/2009 to July/2010), using a descriptive scale of Stover. Then, the infection rate was calculated at 60, 270 and 420 DAP, and was compared by Scott-Knott test at 5%. It was observed that genotypes have the same behavior at 270 DAP. At 60 DAP, genotypes with lower infection rate were Bucaneiro, Enxerto-33, Japira-106, YB42-17, FHIA-02, FHIA-18, FHIA-23, PA42-44, PA94-01, Caipira, Maçã, Prata-Anã and Thap Maeo. At 420 DAP, the lowest rates were obtained for genotypes YB42-17, FHIA-23, Princesa, YB42-47, Tropical, Grand Naine, Caipira, Maçã, Garantida, Bucaneiro, Pacovan Ken and Thap Maeo.

Soil genesis on hypersaline tidal flats (apicum ecosystem) in a tropical semi-arid estuary (Ceará, Brazil)

Wetland soils, especially those under a semi-arid climate, are among the least studied soils in the tropics. The hypersaline tidal flats on the north-eastern Brazilian coast, locally named apicum, are coastal wetland ecosystems in the peripheral portions of semi-arid estuaries. Despite their great ecological importance, they have been highly impacted by anthropogenic activities. Morphological and analytical data of six soil profiles, representative of the different coastal compartments (mangroves, apicum and coastal tablelands) of the north-eastern Brazilian coast, were examined to better understand the pedogenesis of apicum soils. The hypersaline tidal flat soils were classified as Typic Fluvaquents and Typic Sulfaquents with the following main characteristics: predominance of sand fraction (62–77%); presence of high-activity clays (&gt;24 cmolc kg–1 clay); clay fraction comprising kaolinite, illite, smectite and an interstratified smectite/illite; exchangeable complex dominated by Na+ (ESP ≥15%); elevated levels of salinity (electrical conductivity, EC 25–44 dS m–1); alkaline pH values (7.5–9.5). The sandy texture and quartz-dominated composition of the hypersaline, tidal flat soils indicate a pedogenesis associated with the superficial addition of mineral material. This upbuilding process would have lowered the watertable (relatively to the ground level) and decreased the flooding frequency by the tides, favouring salinisation and solonisation processes at the hypersaline tidal flats. Furthermore, the still-existing hydromorphism would have promoted the maintenance of gleisation and sulfidisation. The presence of pyrite on the hyper-saline tidal flat soils further corroborates the formation of apicum soils from/over buried mangroves.

Caracterização de Espodossolos dos Estados da Paraíba e do Pernambuco, Nordeste do Brasil

Estudos com Espodossolos de ambientes tropicais de tabuleiros costeiros ainda são escassos. Este trabalho visou caracterizar perfis desses solos, tanto nos tabuleiros como em uma restinga nos Estados da Paraíba e do Pernambuco, Nordeste do Brasil. O estudo foi realizado com 14 perfis, inseridos em relevo predominantemente plano e sob cultivo de cana-de-açúcar, em que foram realizadas análises físicas, químicas e mineralógicas. Com relação às condições de drenagem, a maioria dos perfis foi definida como moderada a imperfeitamente drenada, com o lençol freático presente a uma profundidade de 182, 85 e 74 cm, em três deles. A textura evidenciou-se predominantemente arenosa, com variações entre areia, areia-franca e franco-arenosa, sempre com valores da fração argila inferiores a 130 g kg-1. Com relação às propriedades químicas, observaram-se acidez elevada, baixa saturação por bases, baixa CTC e alta saturação por Al3+. Alguns horizontes com cores nos matizes 10YR e 7,5YR, com valores entre 5 e 7 e cromas de 2 a 8 classificados como Bs, apresentaram teores de matéria orgânica mais altos que alguns horizontes classificados como Bhs, demonstrando a insuficiência do critério da cor para identificação desses horizontes cimentados. A mineralogia dos solos apresentou predominância de caulinita e quartzo na fração argila, com pequena representação de ilita, gibbsita, feldspato e anatásio. Nos tabuleiros, além desses minerais, também ocorreu a goethita. Na fração silte, verificou-se a predominância de quartzo e caulinita em todos os solos e, em menor expressão, anatásio, feldspato, goethita e gibbsita. Na fração areia, houve predominância do quartzo em todos os perfis, com traços de feldspato.

Comparison of Copper, Manganese, and Zinc Extraction with Mehlich 1, Mehlich 3, and DTPA Solutions for Soils of the Brazilian Coastal Tablelands

Deficiency of micronutrients is increasing in crop plants in recent years in Oxisols and Ultisols in the tropics. The predominant soils in the coastal tablelands of Brazil are Ultisols and Oxisols, with low cation exchange capacity and kaolinitic clay mineralogy. Soil copper (Cu), manganese (Mn), and zinc (Zn) extracted by the Mehlich 1 solution, currently used in the regional soil-testing laboratories, were compared with those extracted by the Mehlich 3 and diethylenetriaminepentaacetic acid (DTPA) solutions in a greenhouse experiment with 10 soil samples (0–20 cm deep) collected from representative Ultisols and Oxisols from various locations in the region. Corn was grown as a test crop, and its dry matter and micronutrient uptake was measured at 30 days of growth. Soil Cu, Mn, and Zn extracted with the three solutions were significantly correlated (0.65–0.95 range for r values), with the Mehlich 3 solution extracting greater quantities than the Mehlich 1 and DTPA solutions. Zinc and Cu taken up by corn plants were significantly related to their soil-extractable levels measured at harvest with all three of the solutions, except for Zn DTPA. However, similar relations between plant uptake and soil extractable Mn were poor, except for DTPA extracting solution.

Plantas de cobertura e adubação nitrogenada na produção de milho em sistema de plantio direto

A utilização de plantas de cobertura do solo pode otimizar o aporte de material orgânico e nutrientes e proteger o solo dos processos erosivos enquanto o N é um dos nutrientes mais exigidos pelas culturas agrícolas, podendo tornar-se um fator limitante de seu rendimento. Neste contexto, realizou-se um experimento para avaliar a influência de três diferentes leguminosas usadas como plantas de cobertura sobre os componentes morfológicos e de produção do milho cultivado em sucessão sob sistema de plantio direto, na ausência e na presença de adubação nitrogenada mineral (80 kg ha-1 de N) na forma de sulfato de amônio. O estudo foi desenvolvido em Latossolo Amarelo nos tabuleiros costeiros do estado de Alagoas. Os componentes de produção do milho apresentaram melhores resultados em sucessão à crotalária spectabilis. Constatou-se efeito da interação entre adubação verde e adubação nitrogenada resultando em maior produtividade de grãos para a cultura do milho.

Nutrição mineral e produção de abacaxizeiro 'Pérola', em função das relações K/N na adubação

A adubação do abacaxizeiro deve contemplar a reposição das quantidades de N e K absorvidas pela planta e exportadas pelos frutos e mudas, e o estabelecimento de relações adequadas entre as doses destes nutrientes. Este trabalho objetivou avaliar o efeito de diferentes relações K/N na adubação sobre a nutrição mineral e a produção de abacaxizeiro 'Pérola', em solos de Tabuleiros Costeiros da Paraíba. O experimento foi conduzido em delineamento experimental em blocos casualizados com 13 tratamentos e três repetições. Os tratamentos resultaram da combinação de quatro relações K/N (0,85:1; 1:1; 2:1 e 3:1), duas doses de N (7,2 e 10,8 g planta-1), quatro tratamentos adicionais (relação K/N de 2:1 na maior dose de N, variando-se a fonte, o parcelamento, a época e a forma de aplicação das doses de N e K) e uma testemunha absoluta (sem adubação). O aumento das relações K/N eleva o peso da folha 'D', os teores de K e os valores das relações K/N e K/Mg; reduz os teores de N e não afeta os teores de P, Ca e a relação K/Ca. O aumento das relações K/N não influencia no peso médio, na produtividade e no percentual de frutos das classes I, II e III. A utilização de sulfato de K, o parcelamento das doses de N e K, na forma de KCl, em cinco aplicações, e a aplicação de metade das doses de N e K via foliar na relação 2:1 aumentam o peso da folha 'D', o teor foliar de N e os valores de peso médio, produtividade e percentual de frutos da classe II.