ABSTRACT Nitrogen (N) fertilization effectiveness in onion depends on N source, as well as on soil type and management system. The aim of the study is to investigate the effect of N sources and doses applied as top-dressing on bulb yield, leaf N contents and on the postharvest conservation of onion bulbs grown under no-tillage (NTS) and conventional tillage (CTS) systems. Three experiments were carried out: two in Lebon Régis County-SC, under NTS; and one in Caçador County-SC, under CTS. The herein tested N sources comprised urea, ammonium nitrate, calcium nitrate and ammonium sulfate, in combination to N doses applied as top-dressing (70, 140, 210, 280 and 350 kg N ha-1) in addition to the control, without N. The N sources did not affect yield parameters, leaf N content and post-harvest onion losses. The maximum technical efficiency in bulb yield was observed at N doses of 195.8 and 258.4 kg ha-1 in the no-tillage system (NTS) and at 270.7 kg N ha-1 in the CTS. The NTS enabled maximum yield at N dose 47% lower than the officially recommended one. Maximum relative commercial yield was associated with 31.1 g kg-1 of leaf N.

RESUMO O cultivo de olerícolas em geral degrada o solo porque é necessário adotar operações de preparo mecânico intenso. Com esta pesquisa objetivou-se quantificar as perdas de solo (PS) e perdas de água (PA) por erosão hídrica no ciclo da cebola em distintos tipos de manejo do solo e de resíduo cultural, em condição de chuva simulada, em 2017. Estudaramse os tratamentos de plantio direto: 1) sulcos na linha de plantio sobre o resíduo de milho (PDM); 2) sulcos na linha de plantio sobre o resíduo de soja (PDS); 3) preparo do solo com uma aração + duas gradagens + rastelo manual sobre o resíduo de milho (PCM); 4) preparo do solo com uma aração + duas gradagens + rastelo manual sobre o resíduo de soja (PCS); 5) preparo do solo com uma aração + duas gradagens + rastelo manual sem cultivo e descoberto (SSC- testemunha). Sobre os tratamentos aplicaramse quatro chuvas simuladas, cada uma com duração de 60 minutos e 65 mm h-1 de intensidade constante, com um simulador de chuva com braços rotativos do tipo empuxo. As perdas de solo totais observadas ao final das quatro chuvas simuladas aplicadas nos tratamentos PDM, PDS, PCM, PCS e SSC foram respectivamente de 1,35; 3,35; 7,36; 33,72; e 55,44 t ha-1. Perdas de solo verificadas nos tratamentos PDM, PDS e PCM foram respectivamente 85%, 63% e 12% menores do que a tolerância de perda de solo de 9 t ha-1 ano-1. O aumento da cobertura do solo pelos resíduos culturais ocasionou diminuição exponencial das perdas de solo, enquanto essas perdas aumentaram exponencialmente com o aumento da velocidade da enxurrada. As perdas de água pela enxurrada apresentaram a mesma tendência das perdas de solo, mas com menor dependência do manejo do solo.

ABSTRACT The cultivation of vegetables in general degrades the soil because it is necessary to adopt intensive me-chanical preparation operations. The objective of this research was to quantify soil losses (SL) and water losses (WL) by water erosion in the onion cycle in different types of soil and crop residue management, under simulated rainfall conditions, in 2017. Notillage treatments were studied: 1) furrows in the planting line on the corn residue (NTC); 2) furrows in the planting line over the soybean residue (NTS); 3) soil preparation with a plow + two harrowing + manual rake on the corn residue (SPC); 4) soil preparation with a plow + two harrowing + manual rake on the soybean residue (SPS); 5) soil preparation with one plowing + two ha-rrowing + manual rake without cultivation and uncovered (BS - control). Four simulated rains were applied to the treatments, each lasting 60 min and 65 mm h-1 of constant intensity, with a rain simulator with rotating arms of the thrust type. The total soil losses observed at the end of the four simulated rainfall applied in the treatments NTC, NTS, SPC, and SPS were respectively 1.35; 3.35; 7.36; 33.72; and 55.44 t ha-1. Soil losses verified in the NTC, NTS and SPC treatments were respectively 85%, 63% and 12% lower than the soil loss tolerance of 9 t ha-1 year-1The increase in soil cover by crop residues caused an exponential decrease in soil losses, while these losses increased exponentially with the increase in runoff velocity. Runoff water losses showed the same trend as soil losses, but with less dependence on soil management.

RESUMO: A biomassa microbiana é determinante na dinâmica da matéria orgânica do solo e sua atividade é um indicador de qualidade do solo em agroecossistemas, refletindo mudanças em práticas de manejo e em condições ambientais. Avaliou-se o efeito de culturas de cobertura de inverno, solteiras ou consorciadas, sobre atributos químicos do solo, carbono da biomassa microbiana (CBM), respiração basal (RB), quociente metabólico (qCO2) e atividade das enzimas urease, β-glucosidase e FDA, bem como o rendimento da cebola em um sistema de plantio direto. O solo é um Cambissolo Húmico alumínico, os tratamentos foram testemunha com vegetação espontânea, cevada, centeio, nabo forrageiro (NF), NF + centeio e NF + cevada. Realizaram-se cinco coletas de amostras de solo (0-10 cm) entre junho a dezembro. Não houve diferenças entre os tratamentos para CBM e RB, e os maiores valores para esses atributos ocorreram em junho, quando as plantas de cobertura estavam em seu estágio inicial. Embora o qCO2 não tenha sido afetado por nenhum tratamento, ele variou entre os períodos de amostragem, com valores entre 0,62 e 10 µg de C-CO2 mg-1 MBC h-1, indicando um ambiente de baixo ou nenhum estresse. As culturas de cobertura tiveram pouca influência na atividade enzimática, mas o FDA foi reduzido em áreas com cultivos solteiros de cevada ou centeio. O rendimento médio de cebola nos tratamentos com culturas de cobertura foi de 13,01 (Mg ha-1), mais alto que no tratamento controle.

ABSTRACT: Microbial biomass is a driving force in the dynamics of soil organic matter, and microbial activity is an indicator of soil quality in agroecosystems, reflecting changes in management practices and environmental conditions. We evaluated the effect of monoculture and intercropped winter cover crops on soil chemical attributes, microbial biomass carbon (MBC), basal respiration (BR), metabolic quotient (qCO2), urease, β-glucosidase, and fluorescein diacetate (FDA) hydrolysis activity, as well as onion yield in a no-tillage system. Soil is a Typic Humudept, and treatments were control with spontaneous vegetation, barley, rye, oilseed radish (OR), OR + rye, and OR + barley. The soil was sampled (0-10 cm) five times between June and December. There were no differences among treatments for MBC and BR, and the highest values for those attributes occurred in June, when cover plants were in their initial stage. Although, qCO2 was not affected by any treatment, it varied among sampling periods, ranging from 0.62 to 10 µg C-CO2 mg-1 MBC h-1, indicating a low- or no stress environment. Cover crops had little influence on enzyme activity, but FDA was lowered in areas with single crops of barley and rye. Average onion yield in cover crops treatments was 13.01 (Mg ha-1), 30-40% higher than in the control treatment.

ABSTRACT The use of cover crops and poultry manure (PM) is an alternative to reduce the use of synthetic inputs and can contribute to the nutrient cycling in onions ( Allium cepa L.) grown under a no-tillage system. However, this management practice may contribute to an increase in N2O emissions to the atmosphere. The aims of this study were to evaluate the immediate effect on N2O emissions of adding PM onto cover crop residues and to verify the effect of different no-tillage systems on N2O emissions. Two studies (laboratory and field) were conducted with the addition of oilseed radish (OR), black oat (BO), and weed (WD) residues with and without PM under a no-tillage (NT) system. Emission of N2O (kg ha-1) was influenced by the different residue-management systems and was higher in treatments with OR residues (2.96 ± 0.67 kg ha-1 for OR and 5.28 ± 1.04 kg ha-1 for OR + PM). The other treatments behaved similarly with emissions of approximately 1.91 ± 0.17 kg ha-1 of N-N2O. The highest N2O emissions in the field study were found within the first 15 days and represented 50.3 % of the average emissions. Poultry manure showed high emissions when the cover crop was OR, but not when it was BO and WD.

ABSTRACT Carbon (C) and nitrogen (N) content in granulometric fractions of soil organic matter (SOM) are sensitive indicators of soil quality changes caused by management systems. This study evaluated the C and N content in granulometric fractions of SOM of aggregates, an Inceptisol under onion grown in no-till vegetable farming systems (NTVFS) and conventional tillage systems (CTS), comparing them to a secondary forest. Treatments consisted of soil cover crops, monocropped and intercropped with onions grown under NTVFS: spontaneous vegetation, 100% black oats; 100% rye; 100% oilseed radish; oilseed (14%) + rye (86%) intercrop and oilseed (14%) + oats (86%) intercrop. The same evaluations were also performed in an area with onions grown under CTS for ± 37 years, and in secondary forest (± 30 years). Undeformed soil samples were collected from 0-5, 5-10, and 10-20 cm deep soil layers, and aggregates were subsequently separated (8.00 mm > Ø ≥ 2.0 mm). Organic C (OC) and N of the granulometric fractions contents were quantified in aggregates, which were subdivided into particulate fractions (POC and PN) and mineral-associated fractions (OCam and Nam). NTVFS promoted protection of SOM at the 0-5 cm depth compared to CTS, as a result of higher POC content. Intercropped oats+oilseed and spontaneous vegetation contributed to an increase in PN content compared to all other treatments under NTVFS. Monocropped and intercroppped oilseed radish caused an increase in Nam, which was more effective than OCam to indicate differences among the systems. Conversion of areas from CTS to NTVFS promotes increases in POC and PN content in the upper soil layer. NTVFS improves the quality of aggregates, and it may reduce damage caused by CTS.

RESUMEN El contenido de carbono (C) y nitrógeno (N) en las fracciones granulométricas de la materia orgánica del suelo (MOS) es un indicador sensible de los cambios en la calidad del suelo causados por los sistemas de manejo. Este estudio evaluó el contenido de Cy N en fracciones granulométricas de la MOS de agregados, en un Inceptisol bajo cebolla cultivada en sistema de cultivo de vegetales sin labranza (SCVSL) y sistema de labranza convencional (SLC), comparándolos con un bosque secundario. Los tratamientos consistieron en cultivos de cobertura del suelo, monocultivos y consorciados con cebollas cultivadas bajo SCVSL: vegetación espontánea, 100% de avena negra; 100% de centeno; 100% nabo forrajero; consorcio de nabo (14%) + centeno (86%), consorcio de nabo (14%) + avena (86%). Las mismas evaluaciones se realizaron en un área con cebollas cultivadas bajo SLC durante ± 37 años, y en un bosque secundario (± 30 años). Se recogieron muestras de suelo no deformadas de capas de suelo de 0-5, 5-10 y 10-20 cm de profundidad, y los agregados se separaron posteriormente (8.00 mm> Ø ≥ 2.0 mm). Las cantidades de C orgánico (CO) y N de las fracciones granulométricas se cuantificaron en agregados, que se subdividieron en fracciones particuladas (PCO y PN) y fracciones asociadas con minerales (COam y Nam). SCVSL promovió la protección de MOS a una profundidad de 0-5 cm en comparación con SLC, como resultado de un mayor contenido de POC. La avena consorciada con nabo y la vegetación espontánea contribuyeron a un aumento en el contenido de PN en comparación con todos los otros tratamientos bajo SCVSL. El nabo forrajero en monocultivo y consorciado causó un aumento en Nam, que fue más efectivo que el COam para indicar diferencias entre los sistemas. La conversión de áreas de SLC a SCVSL promueve aumentos en el contenido de PCO y PN en la capa superior del suelo. SCVSL mejora la calidad de los agregados, y puede reducir el daño causado por SLC.

RESUMEN Se evaluaron los niveles de nitrógeno total (NT) y N de las sustancias húmicas (SH) de la materia orgánica en agregados de suelo cultivado con cebolla bajo siembra directa de hortalizas (SDH) y sistema de preparación convencional (SPC), comparando con un área de bosque. Los tratamientos evaluados fueron: vegetación espontánea; 100% avena; 100% centeno; 100% nabo; cultivos asociados de nabo (14%) + centeno (86%); cultivos asociados de nabo (14%) + avena (86%); área bajo SPC de cebolla (±37 años) y de bosque secundario de ±30 años). Cinco años después de la implantación del SDH fueran recogidas muestras no disturbados del suelo en las capas 0-5, 5-10 y 10-20 cm y obtenidos los agregados (entre 2,0 y 8,00 mm). En estos se determinaron los niveles de NT y el N de las SH, subdivididos en fracción ácidos fúlvicos (N-FAF), ácidos húmicos (N-FAH) y humina (N-HUM). La conversión de áreas de SPC a SDH favorece el aumento de los niveles de NT y N-HUM en la capa de 0-5 cm. Entre las especies de plantas de cobertura utilizadas en el SDH, los cultivos asociados de avena + nabo favorecieron el aumento del N-HUM (0-20 cm) en comparación a los demás tratamientos. La avena solo y el control con vegetación espontánea aumentaron los niveles de N-FAH y N-FAF, respectivamente, en la capa de 10-20 cm, en comparación a los demás tratamientos en SDH y SPC. El SPC con mijo como planta de cobertura aumentó los niveles de N-FAF (0-20 cm) en comparación con el SDH.

ABSTRACT The objective of this study was to evaluate the soil total nitrogen (TN), and N contents in humic substances (HS) of the organic matter in aggregates of soils cultivated with onion under no-till system for horticulture (NTSH) and conventional tillage system (CTS), comparing with an area of forest. The evaluated treatments were natural vegetation (control), 100% black oats, 100% rye, 100% oilseed radish, intercrop of oilseed (14%) + rye (86%), intercrop of oilseed (14%) + black oats (86%), area under CTS of onion for ±37 years, and area with secondary forest for ±30 years. Five years after the NTSH implementation, undisturbed soil samples from the layers 0-5 cm, 5-10 cm, and 10-20 cm were collected; these samples presented aggregate sizes between 2.0 mm and 8.00 mm. The TN, and N contents of the HS were subdivided into fulvic acids (N-FA), humic acids (N-HA), and humin (N-HU) fractions. The change from CTS to NTSH increases the TN and N-HU contents in the 0-5 cm soil layer. The intercrop of oats and oilseed radish, used as soil plant cover species in NTSH, presented a greater increase in N-HU (0-20 cm) than the other treatments. Black oats, and natural vegetation presented a greater increased in N-HA, and N-FA contents, respectively, in the 10-20 cm layer, than the other treatments in NTSH and CTS. CTS with millet as soil plant cover presented a greater increase in N-FA (0-20 cm) contents than the NTSH treatments.

ABSTRACT Carbon (C) contents of humic substances (HS) in soil aggregates are a sensitive indicator of changes in the edaphic quality caused by soil management systems and/or cover plant species. The aim of this study was to assess total contents of C and HS of organic matter in soil aggregates cultivated with onion under a no-till vegetable production system (NTVS) and conventional tillage (CT) compared to a secondary forest area. Treatments consisted of single and mixed cover crops and onion under NTVS: spontaneous vegetation, 100% black oat; 100% rye; 100% oilseed radish; consortium of oilseed radish (14%) + rye (86%); consortium of oilseed radish (14%) + black oat (86%). An area cultivated with onion under CT (± 37 years) and a forest area (secondary forest; ± 30 years) were also evaluated. Five years after implementation of NTVS, undisturbed soil specimens were collected from the 0.0-0.05, 0.05-0.10 and 0.10-0.20 m layers and aggregates were obtained (8.00 mm > Ø > 2.0 mm). In tríese aggregates, total organic carbon (TOC) and C of HS were determined, subdividided into a fulvic acid fraction (C-FAF), humic acid fraction (C-HAF) and humin (C-HUM). With the C values of the HS the following ratios were calculated: C-HAF/C-FAF and (C-HAF+C-FAF)/C-HUM. The highest content of TOC, C-FAF, C-HAF and C-HUM were found in the forest. In NTVS, the contents of TOC (at the 0.0-0.05 m depth) and C-HUM (0.0-0.05 and 0.05-0.10 m) were higher than those found under CT. The highest C-FAF contents were found under CT. NTVS compared to CT favors the humification process (higher C-HUM content and lower ratios of C-HAF+C-FAF/C-HUM (at the 0.0-0.05 and 0.05-0.10 m depths) and the protection of organic matter (higher TOC contents at the 0.0-0.05 m depth)). A linear relationship was observed between C-HUM and N of HS. Among the cover plant species, rye alone and rye combined with oilseed radish had the best results regarding humification of organic matter with predominance of C-HUM and C-HAF. This pattern was also observed in the control for C-HUM, due to the abundance of plant families and species, indicating that plant biodiversification is an effective way to improve the quality of soil.

RESUMEN Los contenidos de carbono (C) de las sustancias húmicas (SH) en los agregados del suelo son un indicador sensible de los cambios en la calidad edáfica causados por los sistemas de manejo del suelo y / o las especies vegetales de cobertura. El objetivo de este estudio fue evaluar el contenido total de C y SH de materia orgánica en agregados de suelo cultivado con cebolla bajo sistema de siembra directa de hortalizas (SSDH) y sistema de preparación convencional (SPC), comparando con un área de bosque. Los tratamientos consistieron en cultivos de cobertura solos y asociados con cebolla bajo SSDH: vegetación espontánea, 100% avena negra; 100% centeno; 100% nabo forrajero; consorcio de nabo (14%) + centeno (86%); consorcio de nabo (14%) + avena negra (86%). También se evaluó un área cultivada con cebolla bajo SPC (± 37 años) y un área de bosque (bosque secundario, ± 30 años). Cinco años después de la implementación de SSDH, se escogieron muestras de suelo de las capas 0,0-0,05, 0,05-0.10 y 0,10-0,20 my obtenidos los agregados (8.00 > Ø > 2,0 mm). En estos agregados, se determinaron el carbono orgánico total (COT) y C de SH, subdivididos en fracción ácido fúlvico (C-FAF), fracción ácido húmico (C-FAH) y humin (C-HUM). Con los valores de C de las SH, se calcularon las siguientes proporciones: C-FAH/C- FAF y (C-FAH + C-FAF)/C- HUM. El mayor contenido de COT, C-FAF, C-FAH y C-HUM se obtuvo en el bosque. En SSDH, los contenidos de COT (0,0-0,05 m) y C-HUM (0,0-0,05 y 0,05-0,10 m) fueron más altos que aquellos encontrados bajo SPC. Los contenidos más altos de C-FAF se encontraron bajo SPC. En SSDH en comparación con SPC favorece el proceso de humificación (mayor contenido de C-HUM y menores índices de C-FAH + C-FAF/C- HUM (en las profundidades de 0.0-0.05 y 0,05-0,10 m) y la protección de la materia orgánica (mayor contenido de COT a 0,0-0,05 m de profundidad)). Entre las especies de plantas de cobertura, el centeno solo y centeno asociado con nabo tuvieron los mejores resultados en cuanto a la humificación de materia orgánica con predominio de C-HUM y C-FAH. Este patrón también se observó en el control para o C-HUM, debido a la abundancia de familias de plantas y especies, lo que indica que la biodiversidad de las plantas es una forma efectiva de mejorar la calidad del suelo.

Spectroscopy associated with chemometrics is a non-destructive method of the samples for the prediction of phenolic compounds. The objective of the work was to apply the near infrared spectroscopy (NIR) technique for the prediction of phenolic compounds and flavonoids in aerial part samples of cover crops plants Raphanus sativus L., Secale cereale L. and Avena strigosa L. Samples were collected at 60, 80 and 100 days after sowing (DAS) of the plants and, after lodging (DAA), at 15 and 30 days, in an experiment implanted in the field, in the city of Ituporanga, Santa Catarina. The samples were homogenized, identified, transported on dry ice, lyophilized, crushed, sieved and stored at -20 °C for analysis. For the calibration, 84 samples were used and for the validation 10 samples. The combination of NIR spectroscopy and multivariate analysis by partial least squares regression allowed the development of prediction models of phenolics and flavonoids with associated errors averaging 10%. NIR spectroscopy is recommended for the development of calibration models because it allows to non-destructive infer phenolic and total flavonoid contents, with high analytical frequency, without the use of reagents and other inputs required by the reference method, with results very close to those obtained in the laboratory.

ABSTRACT This study evaluated the physical attributes of Humic Cambisol cultivated with onion in a no-tillage system (NTSV) and conventional tillage system (CTS), as compared to a secondary forest. The treatments consisted of the use of cover crops, alone and intercropped in an agroecological onion NTSV for six years, in randomized blocks with five replications: spontaneous vegetation, 100% oats; 100% rye; 100% wild radish; intercropping of wild radish (14%) and rye (86%); and intercropping of wild radish (14%) and oats (86%). We also evaluated an onion cultivation area under CTS for ±38 years and a forest area (secondary forest for ±31 years). Undisturbed soil samples were collected at depths of 0-5, 05-10, 10-15 and 15-20 cm, and the soil density, total porosity, macro and micropores, mean geometric diameter and mean weighted diameter of aggregates, and volumetric moisture were evaluated. The NTSV increased the aggregation indices, total porosity and volumetric moisture in comparison to the CTS and the aggregation indices in relation to the forest area. Alone and intercropped wild radish with oats and rye improved the soil physical attributes as compared to the CTS.

RESUMO Este trabalho avaliou os atributos físicos do solo cultivado com cebola em sistemas plantio direto de hortaliças (SPDH) e preparo convencional (SPC) do solo, comparados à área de floresta secundária. Os tratamentos constituíram-se da utilização de plantas de cobertura, solteiras e consorciadas em SPDH agroecológico de cebola por seis anos, em blocos ao acaso com cinco repetições: vegetação espontânea, 100% aveia; 100% centeio; 100% nabo forrageiro; consórcio de nabo forrageiro (14%) + centeio (86%); consórcio de nabo forrageiro (14%) + aveia (86%). Adicionalmente, foram avaliadas duas áreas, uma sob SPC com cultivo de cebola por ±38 anos e outra de mata (floresta secundária, ±31 anos). Foram coletadas amostras indeformadas de solo nas profundidades de 0-5, 05-10, 10-15 e 15-20 cm, e nestas avaliaram-se a densidade do solo; porosidade total, macro e microporos; diâmetro médio ponderado e geométrico dos agregados, e umidade volumétrica. O SPDH aumentou os índices de agregação, a porosidade total e umidade volumétrica em comparação ao SPC, e equiparou-se aos índices de agregação em relação à área de mata. O nabo solteiro e consorciado com aveia e centeio melhorou os atributos físicos do solo em comparação com o SPC.

ABSTRACT Nitrogen derived from cover crop residues may contribute to the nutrition of onion grown under minimum tillage (MT) and cultivated in rotation. The aim of this study was to evaluate the N transferred from different cover crop residues to the onion crop cultivated under MT in southern Brazil. In June 2014, oilseed radish, black oat, and oilseed radish + black oat residues labeled with 15N were deposited on the soil surface before transplanting onions. During the growth season and at harvest, young expanded onion leaves, complete plants, and samples from different soil layers were collected and analyzed for recovery of 15N-labeled residue. Oilseed radish decomposed faster than other residues and 4 % of residue N was recovered in leaves and bulbs at harvest, but in general, N in plant organs was derived from sources other than the cover crop residues. In addition, leaf N was in the proper range for all treatments and was adequately mobilized to the bases for bulbing. The N derived from decomposing residues contributed little to onion development and the use of these plants should be chosen based on their advantages for physical and biological soil quality.

ABSTRACT Nutrients present in soil aggregates are essential for maintaining the productive capacity of agroecosystems and environmental quality. The aim of this study was to evaluate the chemical properties of macroaggregates of a Humic Dystrudept cultivated with onions under a no-till vegetable system (NTVS) compared to the conventional tillage system (CTS) and a forest area in Ituporanga, SC, Brazil. The treatments consisted of the following single and mixed cover crops with onion under the NTVS: spontaneous vegetation, 100 % black oats, 100 % rye, 100 % oilseed radish, intercropped oilseed radish (14 %) + rye (86 %), and intercropped oilseed radish (14 %) + black oat (86 %). Additionally, we evaluated two areas, one with onion grown under the CTS for ±37 years and an area under forest for ±30 years, both adjacent to the experiment. Five years after implementation of the treatments with cover crops, we collected undisturbed soil samples at depths of 0.00-0.05, 0.05-0.10, and 0.10-0.20 m, and we obtained macroaggregates (8.00 mm > Ø ≥ 2.0 mm). We analyzed total organic carbon (TOC), pH in water, Ca2+, Mg2+, Al3+, H+Al, K+, and P in the macroaggregates. The conversion of onion-growing areas from the CTS to the NTVS after five years increases TOC, pH, Ca, Mg, and K in soil macroaggregates at the depth of 0.00-0.05 m. There is increased K content in the macroaggregates of soil under the NTVS at all depths evaluated in this study compared to the CTS. The use of millet in the CTS increases P content at depth (0.05-0.10 and 0.10-0.20 m). Intercropping black oat + oilseed radish increases Ca content at the 0.10-0.20 m depth in comparison to the black oat, rye + oilseed radish, and control treatments, and increases Mg content as well, compared to the other cover crops at the depths of 0.05-0.10 and 0.10-0.20 m.

RESUMO Na cultura da cebola, diversos trabalhos comprovam que a densidade populacional e a fertilização nitrogenada devem ser consideradas quando se deseja combinar produtividade com produtos de qualidade. O experimento teve por objetivo avaliar o efeito de doses de nitrogênio, via fertirrigação, em diferentes densidades populacionais na produtividade e armazenamento pós-colheita de bulbos de cebola nas condições do Alto Vale do Itajaí-SC. Com este propósito foram conduzidos dois ensaios de campo, em 2011 e 2013, em Cambissolo Háplico, em Ituporanga-SC. Os tratamentos corresponderam a quatro densidades de plantas (300, 400, 500 e 600 mil plantas/ha) submetidas a cinco doses de nitrogênio (0, 50, 100, 150 e 200 kg/ha de N), distribuídas ao longo do ciclo vegetativo da cultura via fertirrigação. Utilizou-se a cultivar Bola Precoce. As semeaduras foram realizadas em 25/04/2011 e 19/04/2013, os transplantes em 25/07/2011 e 12/07/2013 e as colheitas em 25/11/2011 e 21/11/2013. Foram avaliadas as produtividades comerciais (total, Cx2, Cx3 e Cx3+), teor de N na metade do ciclo, florescimento (%) e perda pós-colheita (%). Produtividades comerciais totais máximas de 58,3 e 55,1 t/ha são obtidas com doses de 161,3 e 129,0 kg/ha de N, respectivamente para 2011 e 2013. O aumento de doses de N reduz a formação de bulbos Cx2. A maior produtividade Cx3 (25,6 a 39,3 t/ha) foi obtida com populações de 500 a 600 mil plantas/ha e doses de 126,1 a 135,9 kg/ha de N. O aumento da densidade populacional reduz a produtividade Cx3+. As maiores produtividades Cx3+ (49,6 a 54,4 t/ha) foram alcançadas com doses de 126,3 e 156,7 kg/ha de N. Para a cultivar Bola Precoce podem ser considerados adequados na metade do ciclo teores foliares de N na faixa de 23,0 a 34,0 g/kg. O aumento das doses de N concorre para o aumento do florescimento, mas não influencia as perdas em pós-colheita.

ABSTRACT On onion, several studies have confirmed that the population density and nitrogen fertilization should be considered to combine quality and productivity. The experiment aimed to evaluate the effect of nitrogen by fertigation under different population densities on yield and postharvest losses of onion bulbs at Alto Vale do Itajaí, Santa Catarina State, Brazil. Two experiments were carried out, in 2011 and 2013, with Bola Precoce cultivar, over an Haplumbrept soil at Ituporanga, Santa Catarina State. The treatments included four plant densities (300, 400, 500 and 600 plants/ha) and five doses of nitrogen (0, 50, 100, 150 and 200 kg/ha N), distributed by fertigation. Sowing was carried out on 2011/04/25/ and 2013/04/19, transplanting on 2011/07/25 and 2013/07/12 and harvest on 2011/11/25 and 2013/11/21. Commercial yields (total, Cx2, Cx3 and Cx3+), N content in half the cycle, flowering (%) and postharvest losses (%) were evaluated: the highest total commercial yields of 55.1 and 58.3 t/ha were reached with doses of 129.0 and 161.3 kg/ha N, respectively. Increasing doses of N reduces the formation of Cx2 bulbs. The highest Cx3 yield (25.6 to 39.3 t/ha) was obtained with populations of 500 to 600 thousand plants/ha and doses of 126.1 to 135.9 kg/ha N. Increased population density reduces the Cx3+ productivity. The highest Cx3+ (49.6 to 54.4 t/ha) was achieved with doses of 126.3 and 156.7 kg/ha N. To cultivate Bola Precoce can be considered appropriate, in the middle of the cycle, foliar nitrogen content in the range of 23.0 to 34.0 g N/kg. The increase of nitrogen levels contributes to increase blooming, but does not influence the postharvest losses.

RESUMO: No Sul, principal região produtora de cebola do Brasil, não se dispõe, atualmente, de pesquisas sobre a dinâmica de absorção de nutrientes, exigência nutricional e exportação de nutrientes para o sistema de transplante de mudas, que abrange mais de 70% da área cultivada com esta hortaliça. Objetivou-se determinar o crescimento, acúmulo, partição e as taxas de absorção de nutrientes para a cultivar de cebola Bola Precoce no sistema de transplante na região Sul do Brasil. O presente trabalho foi conduzido a campo na Estação Experimental da Epagri, município de Ituporanga-SC. O delineamento experimental foi em blocos casualizados com 18 tratamentos e cinco repetições. Cada tratamento correspondeu a uma época de avaliação/coleta realizada em intervalos de sete dias. Cada parcela foi constituída de 27 plantas e para cada avaliação foram coletadas as cinco plantas centrais de cada parcela. Foi avaliado o acúmulo de massa seca, taxa de crescimento absoluto, teor e conteúdo dos nutrientes N, P, K, Ca, Mg, Zn, Fe, Cu, B e Mn nas folhas e bulbos e determinadas as taxas de absorção. O crescimento foi lento e a demanda por nutrientes baixa na primeira metade do ciclo até aos 60 dias após o transplante (DAT). Durante o período de bulbificação (61-119 DAT), o crescimento e a absorção de nutrientes foram intensificados e a planta acumulou 84% da MS total e entre 73 e 89% do total de nutrientes. No final do ciclo, para uma produtividade média de 37,34 t/ha, a sequência de acúmulo de nutrientes verificada em ordem decrescente foi N>K>Ca>P>Mg>Fe>B>Mn>Zn>Cu, com 101,4; 86,5; 46,6; 34,5; 12,1 kg/ha e 761; 221; 150; 84 e 34 g/ha, respectivamente. Dessa quantidade, 57,5; 52,8; 42,3; 68,5; 57,3; 37,6; 70,7; 41,9; 73,6 e 71,6%, respectivamente, foram depositados no bulbo.

ABSTRACT: In Southeit was rn Brazil, the Country main onion-producing region, research is not available on the dynamics of nutrient absorption, nutritional requirement and exportation of nutrients for the seedling transplanting system, which covers over 70% of the cultivated area with this vegetable crop. The objective was to determine growth, accumulation, partitioning and nutrient absorption rates of onion cultivar Bola Precoce in the transplanting system in the Southern Brazil. This study was carried out under field conditions at the Experimental Station of Epagri, municipality of Ituporanga, Santa Catarina State, Brazil. The experimental design was randomized blocks with 18 treatments and five replications. Each treatment corresponded to a time of assessment/collect held at intervals of seven days. Each plot consisted of 27 plants and for each evaluation we collected the five central plants in each plot. It was evaluated the dry matter accumulation, absolute growth rate, content of nutrients N, P, K, Ca, Mg, Zn, Fe, Cu, B and Mn in the leaves and bulbs and determined absorption rates. Growth was slow and demand for nutrients low in the first half of the cycle up to 60 days after transplanting (DAT). During bulbification (61-119 DAT), growth and nutrient absorption were enhanced and plants accumulated 84% of the total dry matter and from 73 to 89% of the nutrients. At the end of the cycle, for an average yield of 37.34 t/ha, nutrient accumulation in descending order was N> K>Ca>P>Mg>Fe>B>Mn>Zn>Cu, with 101.4; 86.5; 46.6; 34.5; 12.1 kg/ha and 761; 221; 150; 84 and 34 g/ha, respectively. From that amount, 57.5; 52.8; 42.3; 68.5; 57.3; 37.6; 70.7; 41.9; 73.6 and 71.6%, respectively, were deposited in the bulb.

Decorrente dos sistemas de manejo empregados no solo, como o sistema de preparo convencional (SPC) versus o sistema de plantio direto de hortaliças (SPDH), modificações nos atributos edáficos ocorrem; por exemplo, nos índices de agregação do solo e seu teor de carbono orgânico total (COT). Objetivaram-se quantificar os teores de COT e avaliar os índices de agregação do solo e a distribuição dos agregados por classes de diâmetro sob cultivo de cebola em SPDH e SPC, comparados a uma área de mata adjacente em Ituporanga, SC. Os tratamentos constituíram-se da semeadura de plantas de cobertura, solteiras e consorciadas, em SPDH: vegetação espontânea (VE); 100 % aveia; 100 % centeio; 100 % nabo-forrageiro; consórcio de nabo-forrageiro (14 %) e centeio (86 %); e consórcio de nabo-forrageiro (14 %) e aveia (86 %). Adicionalmente, foram avaliadas uma área de cultivo de cebola em SPC por ±37 anos e uma área de mata (floresta secundária; ±30 anos), ambas adjacentes ao experimento. Em setembro de 2013, cinco anos após a implantação dos tratamentos com plantas de cobertura, foram coletadas amostras indeformadas do solo nas camadas de 0-5, 5-10 e 10-20 cm e separados os agregados para avaliar a estabilidade via úmida. Nos agregados, foi quantificado o COT; após a separação em classes de diâmetro (8,00 mm>Ø≥0,105 mm), calcularam-se o diâmetro médio ponderado (DMP) e o geométrico (DMG) dos agregados; a distribuição deles em macroagregados (Ø≥2,0 mm), mesoagregados (2,0>Ø≥0,25 mm) e microagregados (Ø<0,25 mm); e o seu índice de sensibilidade (IS). Os dados foram submetidos à análise de variância e de componentes principais (ACP). Os maiores teores de COT foram encontrados na área de mata (52,83; 37,77; e 26,70 g kg-1, respectivamente para 0-5, 5-10 e 10-20 cm); e os menores, no SPC (18,23 g kg-1, 0-5 cm). Os tratamentos com plantas de cobertura, solteiras ou consorciadas, não apresentaram diferenças entre si (p≤0,05) para o COT, nem em relação à área testemunha (VE). O SPC apresentou os menores índices de DMP (3,425; 3,573; e 3,401 mm), DMG (2,438; 2,682; e 2,541 mm) e IS (0,77; 0,79; e 0,81), nas três camadas avaliadas. Para o DMP e DMG, não foram verificadas diferenças (p≤0,05) entre tratamentos no SPDH; porém, esses índices foram superiores aos do SPC; os de DMP, iguais aos da área de mata; e os de DMG, maiores na camada de 0-5 e 5-10 cm. Na camada de 10-20 cm, no SPDH, o tratamento com nabo-forrageiro apresentou maiores valores de DMP (4,520 mm), DMG (4,284 mm) e IS (1,07). Em relação à distribuição dos agregados por classes de diâmetro, o SPC evidenciou, respectivamente, os menores (14,22; 14,75; e 13,86 g) e maiores (4,94; 3,44; e 3,52 g/3,0; 3,0; e 3,76 g) valores para macro e meso/microagregados, enquanto o SPDH demonstrou maiores valores de macroagregados (médias de 19,90; 20,48; e 18,56 g) em comparação à mata (16,0; 16,31; e 15,47 g) e ao SPC (14,22; 14,75; e 13,86 g) nas três camadas avaliadas. O uso de plantas de cobertura, solteiras ou consorciadas, em SPD de cebola foi eficiente para recuperar e aumentar os teores de COT e os índices de DMP, DMG e IS em relação ao SPC; e, em comparação à área de mata, aumentou o DMG (0-5 e 5-10 cm). O nabo-forrageiro aumentou a agregação do solo (DMG e IS) na camada de 10-20 cm em relação aos demais tratamentos com plantas de cobertura. A ACP evidenciou a perda de COT e o aumento dos meso e microagregados no SPC, assim como a substituição do SPC por SPDH com plantas de cobertura elevou a formação de macroagregados estáveis em água, com posterior aumento do DMP, DMG e IS.

As a result of soil management systems, like the conventional tillage system (CTS) versus the no-tillage system (NTS) for vegetable crops, modifications in soil properties occur, which change, for example, the rates of soil aggregation and the content of total organic carbon (TOC). The aim of this study was to quantify the TOC contents and evaluate the rates of soil aggregation and the distribution of aggregates by diameter classes in a soil planted to onion in NTS and CTS and compare them to an adjacent forest area in Ituporanga, Santa Catarina, Brazil. We evaluated the following treatments, which consisted of planting cover crops, alone and intercropped, in NTS: spontaneous vegetation (SV); 100 % oats; 100 % rye; 100 % wild radish; intercropping of wild radish (14 %) and rye (86 %); and intercropping of wild radish (14 %) and oats (86 %). We also evaluated an onion-growing area under CTS for ±37 years, and a forest area (secondary forest for ±30 years), both adjacent to the experimental area. In September 2013, five years after setting up treatments with cover crops, undisturbed soil samples were collected from the 0-5, 5-10, and 10-20 cm soil layers, and aggregates were separated to assess stability by the wet method. In the aggregates, we quantified TOC and, after separation into diameter classes (8.00 mm>Ø≥0.105 mm), we calculated the mean weighted diameter (MWD) and mean geometric diameter (MGD) of the aggregates, the distribution of the aggregates in macroaggregates (Ø≥2.0 mm), mesoaggregates (2.0>Ø≥0.25 mm), and microaggregates (Ø<0.25 mm), and the aggregate sensitivity index (SI). Data underwent analysis of variance and principal component analysis (PCA). The highest TOC contents were found in the forest area (52.83, 37.77, and 26.70 g kg1 for the depths of 0-5, 5-10, and 10-20 cm, respectively) and the lowest in the CTS (18.23 g kg-1, 0-5 cm). Treatments with cover crops, alone or intercropped, did not differ among themselves (p≤0.05) for TOC, or in relation to the control area (SV). The CTS had the lowest rates of MWD (3.425, 3.573, and 3.401 mm), MGD (2.438, 2.682, and 2.541 mm) and SI (0.77, 0.79, and 0.81) in the three layers evaluated. For MWD and MGD, differences were not observed (p≤0.05) among treatments in NTS, but these rates were higher than the rates of CTS; the MWD readings were equal to the forest area; and the MGD readings were higher in the 0-5 and 5-10 cm layers. In the 10-20 cm layer, in the NTS, treatment with wild radish showed higher values of MWD (4.520 mm), MGD (4.284 mm), and SI (1.07). Regarding the distribution of aggregates by diameter classes, the CTS showed the smallest (14.22, 14.75, and 13.86 g) values for macroaggregates, and largest (4.94, 3.44, and 3.2 g/3.0, 3.0, and 3.76 g) values for meso-/microaggregates, respectively. The NTS showed higher macroaggregate values (means of 19.90, 20.48, and 18.56 g) compared to the forest area (16.0, 16.31, and 15.47 g) and to the CTS (14.22, 14.75, and 13.86 g) in the three layers evaluated. The use of cover crops, alone or intercropped, in NTS of onion was quick in recovering and increasing the TOC and the MWD, MGD, and SI indices in relation to the CTS, and, compared to the forest area, the MGD increased (0-5 and 5-10 cm). Oilseed radish increased soil aggregation (MGD and SI) in the 10-20 cm layer compared to the other treatments with cover crops. The PCA showed loss of TOC, and increase in the meso- and microaggregates of CTS, just as the substitution of CTS for NTS with cover plants increased the formation of macroaggregates stable in water, with a subsequent increase in the MWD, MGD, and SI indices.

A produção de biomassa e extração de nutrientes na cultura da cebola (Allium cepa) é influenciada pela nutrição das plantas. O experimento teve por objetivo avaliar a produção de biomassa e extração de nutrientes da cebola sob adubação convencional e orgânica com o uso de biofertilizantes. Com este propósito foi conduzido um experimento de campo, na safra 2010, num Cambissolo Háplico, em Ituporanga-SC. Aplicaram-se quatro tratamentos: convencional (T1) (adubação no plantio e de cobertura e tratos fitossanitários recomendados oficialmente para a cultura); e três outros com adubação de plantio com adubos permitidos pelo MAPA para sistemas orgânicos de produção, diferenciados pela aplicação em cobertura via solo com biofertilizante à base de esterco de peru [bioperu (T2)] ou esterco bovino [biobovino (T3)] ou biofertilizante à base de esterco bovino pulverizado a 3% [biobovino pulverizado (T4)]. Utilizou-se a cultivar Epagri 352-Bola Precoce. Semeadura, transplante e colheita foram realizados em 03/05, 12/07 e 06/12/2010, respectivamente. Foram avaliados durante o ciclo, em dias após o transplante (DAT), a extração total de nutrientes do sistema aéreo (aos 48, 68 e 108 DAT) e bulbos (148 DAT), a análise do solo (aos 48, 68, 108 e 148 DAT). O crescimento (biomassa fresca) e o desenvolvimento (número de folhas) das plantas foram avaliados aos 30, 48, 68 e 108 DAT. A adição de nutrientes via biofertilizantes no solo e foliar não é capaz de suprir a necessidade de nutrientes, sendo responsável por gerar desequilíbrios que diminuem o crescimento e desenvolvimento da cultura.

Biomass production and nutrient uptake on onion (Allium cepa) is influenced by plant nutrition. The experiment was carried out to evaluate biomass production and nutrient uptake of onion under conventional and organic fertilization with the use of biofertilizers. For this purpose we conducted a field experiment in a Cambisol, in 2010, at Ituporanga, Santa Catarina state, Brazil. Four treatments were applied: conventional (T1) (planting application and sidedress with conventional mineral fertilizers and phytosanitary treatment with products recommended for the onion crop), and three others with fertilizer allowed by MAPA (Ministry of Agriculture, Livestock and Food Supply) for organic production systems, differentiated by sidedress application via soil with turkey manure based biofertilizer [Bioperu (T2)] or cattle manure based biofertilizer [Biobovino (T3)] or cattle manure based biofertilizer sprayed at 3% [Biobovino sprayed (T4)]. The cultivar used was Epagri 352-Bola Precoce. The sowing, transplant and harvest were performed in 03/05/10, 12/07/10 and 06/12/2010, respectively. During the cycle were evaluated in days after transplanting (DAT), the total extraction of nutrients from the shoot (at 48, 68 and 108 DAT) and bulbs (148 DAT) and in the same dates of the soil analysis. The growth (fresh biomass) and development (number of leaves) of the plants were measured at 30, 48, 68 and 108 DAT. The addition of nutrients via soil or foliar biofertilizer is not able to supply the needs for nutrients and was responsible for generating imbalances which decrease the growth and development of the crop.