ABSTRACT Second-crop maize-ruzigrass (Urochloa ruziziensis) intercropping, nitrogen (N) fertilization, and high maize plant densities enhance biomass production and N cycling, which may favor soybean growth and yield in the following season. This study aimed to assess the effects of second-crop maize-ruzigrass intercropping, N top dressing, and maize plant density on straw production in autumn/winter, N cycling, and agronomic performance of soybean crops grown in succession. Field experiments were installed in the 2018/2019 and 2019/2020 seasons using a randomized complete block design with split-split plots and four replications. The following factors were investigated: cropping system (sole maize and maize intercropped with ruzigrass), N top dressing (0 and 80 kg ha-1), and maize plant density (40, 60, 80, and 100 thousand plants ha-1). Maize-ruzigrass intercropping improved straw yield (2,365 kg ha-1) and N cycling (50 kg ha-1), and increased soybean yield in the following season (232 kg ha-1). N fertilization of maize increased soybean grain yield by 180 kg ha-1. Maize plant density did not influence the performance of succeeding soybean crops, regardless of the growing season.

RESUMO O consórcio milho segunda safra com braquiária ruziziensis (Urochloa ruziziensis), adubação com nitrogênio (N) e alta densidade de plantas do milho aumentam a produção de biomassa e a ciclagem de N, o que pode favorecer o crescimento e a produtividade da soja na safra seguinte. Este estudo teve como objetivo avaliar os efeitos do consórcio milho segunda safra com Brachiaria ruziziensis, aplicação de N em cobertura e densidade de plantas de milho sobre a produção de palha no outono/inverno, ciclagem de N e desempenho agronômico da soja em sucessão. Os experimentos de campo realizados nas safras 2018/2019 e 2019/2020, em delineamento de blocos completos casualizados com parcelas subdivididas e quatro repetições, investigaram os seguintes fatores: sistema de cultivo (milho solteiro e milho consorciado com Brachiaria ruziziensis), cobertura de N (0 e 80 kg ha-1) e densidade de plantas de milho (40, 60, 80 e 100 mil plantas ha-1). O consórcio milho-Brachiaria ruziziensis melhorou a produtividade de palha (2.365 kg ha-1) e a ciclagem de N (50 kg ha-1) e aumentou a produtividade de soja em sucessão (232 kg ha-1). A adubação nitrogenada do milho aumentou a produtividade de grãos de soja em 180 kg ha-1. A densidade de plantas do milho não influenciou o desempenho da soja cultivada em sucessão, independentemente da safra.

ABSTRACT Late sowings anticipate flowering and decrease the soybean vegetative plasticity. These changes may limit the ability of plants to tolerate leaf area losses. The objective of this research was to evaluate the sowing date effect on soybean tolerance to defoliation at the beginning of pod formation. The experiment was set in Lages (Santa Catarina State, Brazil) during the 2016/2017 growing season. Two sowing dates were tested: November 2, 2016 (preferential) and December 15, 2016 (late). Five levels of defoliation (0%, 17%, 33%, 50% and 67%) of cultivar NA 5909 RG were imposed at the R3 growth stage. Grain yield showed a quadratic response to defoliation, ranging from 4,313 to 6,478 kg ha-1 in the preferential sowing date and from 3,374 to 4,443 kg ha-1 in the late sowing date. The plants tolerated up to 45.6% of defoliation in early sowing and 55.8% in late sowing, without yield losses, in comparison to the control. The highest level of defoliation reduced grain yield by 26.9% and 13.4% in early and late sowings, respectively, compared to the control. The delay of sowing date did not increase the sensitivity of cultivar NA 5909 RG to defoliation at the beginning of pod formation.

Abstract SCSBRS126 Dueto is a late-maturing high yield performing cultivar released by Epagri/Embrapa/Udesc. It has high tillering capacity, but poor resistance to lodging, medium resistance to blast, with long, slender grains and good sensory/cooking traits, and it has lower sterility under cold stress at microsporogenesis/anthesis and under heat at anthesis. SCSBRS SCSBRS12 latematuring late maturing EpagriEmbrapaUdesc Epagri Embrapa Udesc Epagri/Embrapa/Udesc capacity lodging blast long sensorycooking sensory cooking traits microsporogenesisanthesis microsporogenesis anthesis SCSBRS1

Abstract The objective of this work was to evaluate the impacts of nitrogen topdressing fertilization and plant density of second-crop maize on the biomass and crude protein production of ruzigrass (Urochloa ruziziensis) grown in intercropping. The experiment was carried out during two growing seasons in a randomized complete block design, in split plots, with four replicates. The treatments consisted of N topdressing rates (0 and 80 kg ha−1) and maize plant densities (40, 60, 80, and 100 thousand plants per hectare). Ruzigrass biomass accumulation was measured at the V14, R1, R3, and R6 stages of maize growth, as well as during ruzigrass desiccation. Ruzigrass crude protein content and production and biomass partitioning to leaves, stems, and senescent tissues were evaluated in the R6 stage of maize. The increase in maize plant density reduced ruzigrass growth. However, nitrogen fertilization and maize plant density did not affect ruzigrass biomass partitioning. During intercropping, N fertilization did not affect ruzigrass yield. After maize harvest, N fertilization resulted in a higher ruzigrass biomass (30.2% in 2019) and crude protein (13.8%) production. Low maize plant densities and N topdress fertilization improve the biomass production of ruzigrass in intercropping.

Resumo O objetivo deste trabalho foi avaliar os impactos da adubação nitrogenada de cobertura e da densidade de plantas de milho de segunda safra sobre a produtividade de biomassa e proteína bruta da braquiária (Urochloa ruziziensis) cultivada em consórcio. O experimento foi realizado em duas safras, em blocos ao acaso em parcelas subdivididas, com quatro repetições. Os tratamentos consistiram de doses de N em cobertura (0 e 80 kg ha−1) e densidades de plantas de milho (40, 60, 80 e 100 mil plantas por hectare). O acúmulo de biomassa da braquiária foi avaliado nos estádios V14, R1, R3 e R6 do milho, bem como na dessecação da braquiária Avaliaram-se o teor e a produção de proteína bruta e a par tição de biomassa em folhas, colmos e tecidos senescentes da braquiária no estágio R6 do milho. O aumento da densidade de plantas de milho reduziu o crescimento da braquiária. No entanto, a adubação nitrogenada e a densidade de plantas de milho não afetaram a partição de biomassa da braquiária. Durante o consórcio, a adubação nitrogenada não impactou a produtividade da braquiária. Após a colheita do milho, a adubação nitrogenada proporcionou maior produção de biomassa (30,2% em 2019) e de proteína bruta (13,8%) da braquiária. As baixas densidades de plantas de milho e a adubação nitrogenada melhoram a produção de biomassa de braquiária em consórcio.

ABSTRACT Soybean tolerance to defoliation may be affected by population density, as the plant population interferes with the crop leaf area index . This study aimed to evaluate the effect of defoliation at the beginning of pod formation on the agronomic performance of soybean at different plant densities. The experiment was conducted under field conditions in Campos Novos, SC, Brazil, during 2016/2017 and 2017/2018 growing season. The experimental design was a randomized block in a split-plot arrangement. The main plot consisted of three densities (100,000, 300,000, and 500,000 plants ha−1), whereas the subplots consisted of the cultivar NA 5909 RG submitted to five defoliation levels (0, 16.6, 33.3, 50, and 66.6%). Grain yield ranged from 4,219 to 5,356 kg ha−1 in the 2016/2017 growing season and 3,732 to 5,186 kg ha−1 in the 2017/2018 growing season. Plant density did not interfere with the grain yield response to defoliation performed at the beginning of pod formation. The 16.6% defoliation increase grain yield by 7.5 and 5.6% relative to the control in 2016/2017 and 2017/2018 growing seasons, respectively. The soybean tolerate defoliation of up to 33.3% at R3 with no significant decrease in grain yield, regardless of the plant density.

ABSTRACT Delay of sowing date in subtropical environments with long growing seasons can modify the yield response of corn hybrids to nitrogen (N) fertilization. This study evaluated the effects of the sowing time, and N top-dress rate on corn hybrids’ yield and N-use efficiency with different cycles. Two field experiments were carried out in subtropical environment of southern Brazil. The following factors were investigated: corn hybrids (AG9025, super early cycle and P30F53, early cycle), sowing times (early and late spring), and N top-dress rates (0, 150, 300 and 450 kg ha-1). The delay of sowing date from early to late spring reduced 10 % the number of kernels per ear, decreasing grain yield. Corn presented lower yield potential in late sowings (-24 %), associated with a smaller response of grain yield to the N rate increase. The maximum corn yield was achieved at a rate of 360 kg ha-1 of N in early spring sowing and 300 kg ha-1 in late spring. The hybrid with early cycle presented greater yield stability and higher N use efficiency than the super early cycle hybrid in the late sowing. The N agronomic efficiency use is 47 % lower in late spring sowing than in early spring sowing. Regardless of the sowing date, the N use efficiency decreased 0.08 for each kg ha-1 N rate increase. This study suggests a reduction of at least 20 % in the N top-dress rate when the sowing date of corn is delayed to late spring in southern Brazil to decrease N losses and production costs.

ABSTRACT. Water deficiency reduces leaf expansion and photosynthetic efficiency, potentially reducing the ability to withstand leaf area (LA) loss. This study aimed to evaluate the effects of water restriction on soybean tolerance to defoliation in the vegetative and reproductive periods of development. Two experiments were conducted in a greenhouse located in Lages, Santa Catarina State Brazil, during the 2017/2018 growing season. Cultivar NA 5909 RG was subjected to three WR levels (none, moderate, and severe) and five defoliation levels (0, 17, 33, 50, and 67%). Defoliation occurred at the V6 stage in the first experiment and R3 in the second. WR occurred for 7 days after defoliation. LA at R2 and R5 after defoliation at V6 and R3 decreased by 27.5 and 64.6%, respectively, regardless of WR. LA between V6 and R2 was not influenced by WR or defoliation. Moderate or severe WR reduced plant ability to recover LA between R3 and R5. Severe WR decreased grain production by 22.2% in the vegetative period and 21.2% per plant in the reproductive period compared to that of the control, regardless of defoliation. The highest defoliation level reduced grain production per plant by 24.7 and 24.3% relative to the control at stages V6 and R3, respectively, regardless of WR. WR imposed at the vegetative and reproductive stages did not increase defoliation sensitivity.

RESUMEN La reducción del espacio entre líneas y la siembra en líneas dobles en maíz (Zea mays L.) permite una distribución más equidistante de las plantas con una misma densidad. El objetivo de este trabajo fue evaluar los efectos de dos prácticas de manejo sobre el contenido de nitrógeno en la hoja índice, el índice de área foliar del cultivo y el rendimiento de granos de maíz a diferentes densidades de plantas. El experimento fue realizado en Lages, en la Universidad del Estado de Santa Catarina, en el sur de Brasil, en los periodos de cosecha 2016/2017 y 2017/2018. Se utilizó un arreglo de parcelas divididas de un diseño experimental de bloques completos al azar. En la parcela principal se evaluaron dos densidades (7 y 9 plantas m-2) y en las subparcelas se evaluaron cinco espacios entre líneas (0.4 m, 0.6 m, 0.8 m, 1.0 m y líneas dobles de 0.6 m entre cada una y 0.18 m entre líneas del par). Se evaluaron las características fisiológicas y el rendimiento de granos del maíz hibrido P30R50YH, sembrado en 20/10/2016 y 21/10/2017. Los rendimientos de grano fueron mayores en la densidad de 9 plantas m-2 que a 7 plantas m-2. El espacio entre filas no afectó el índice de contenido de nitrógeno en la hoja, el índice de área foliar del cultivo en el espigamiento, y el rendimiento de granos. El incremento en la densidad de plantas fue más eficiente que la reducción del espacio entre líneas y la siembra en líneas dobles para incrementar el rendimiento del hibrido P30R50YH.

ABSTRACT Reducing row space and sowing in twin rows of maize (Zea mays L.) allow more equidistant plant distribution at the same density. The objective of this research was to evaluate the effect of these two management practices on the nitrogen content of the index leaf, the leaf area index at silking, and the grain yield of maize at different plant densities. The experiment was carried out in Lages, Santa Catarina State University, in southern Brazil during the growing seasons 2016-2017 and 2017-2018. A split-plot arrangement of a randomized complete block design was used. Two plant densities (7 and 9 plants m-2) were distributed in the main plot, and five row spaces (0.4, 0.6, 0.8, 1.0 m and twin rows 0.6 m apart with 0.18 m between rows) were evaluated in split-plots. Physiological traits and grain yield were determined on the maize hybrid P30R50YH. The experiments were sown on 10/20/2016 and 10/21/2017. Kernel yields were higher at the plant density of 9 plants m-2 than at 7 plants m-2. The row space did not affect the nitrogen content of the index leaf, the crop leaf area index at silking, and the maize grain yield. The increment of plant density was more effective than the use of narrow and twin rows to enhance P30R50YH hybrid grain yield.

RESUMEN El fraccionamiento de la fertilización nitrogenada en la superficie, con la aplicación de una parte de nitrógeno en el panojamiento, puede aumentar el rendimiento de los granos de maíz, principalmente cuando el cultivo se siembra en la fecha más favorable para obtener una alta productividad. El objetivo de esta investigación fue evaluar los efectos de la fecha de siembra sobre la respuesta del maíz al fraccionamiento de la fertilización nitrogenada en la superficie y a los estados fenológicos. Se evaluaron dos fechas de siembra: preferencial (15/10/2015 y 20/09/2016) y tardía (5/12/2015 y 5/12/2016). En cada fecha de siembra fueron analizados seis tratamientos de aplicación de nitrógeno en la superficie: testigo sin N; aplicación de dosis completa de N en V5, V10 y VT; ½ aplicación de N en V5, + ½ aplicación de N en V10; y ⅓ de la aplicación de N en V5 + ⅓ de la aplicación de N en V10 + ⅓ de la aplicación de N en VT. La dosis de nitrógeno utilizada fue de 300 kg ha-1. El rendimiento de granos varió entre 8.9 a 15.3 t ha-1 en Lages y 7.4 a 16.4 t ha-1 en Atalanta. No hubo diferencias significativas en el rendimiento de granos ni en la eficiencia agronómica del uso de nitrógeno (EUN) entre los tratamientos con aplicación de la dosis completa de N en los estadios V5 y V10 y aquellos en los que el nutriente se dividió dos o tres veces, independiente de la fecha de siembra. La EUN fue mayor en la siembra realizada al en la fecha preferencial que en la fecha tardía, independientemente del manejo de la aplicación nitrogenada en la superficie. El fraccionamiento de la fertilización nitrogenada en la superficie hasta VT no incrementó el rendimiento de granos ni la EUN del maíz.

ABSTRACT The splitting of nitrogen side-dressing fertilization with the application of a nitrogen dose at maize tasseling may increase grain yield, mainly when the crop is sown at the most favorable date to achieve high productivity. This research was carried out to evaluate the effect of sowing date on the response of maize to the splitting of nitrogen side-dressing fertilization at different growth stages. Two sowing dates were tested: preferential (10/15/2015 and 09/20/2016) and late (12/5/2015 and 12/5/2016). Six nitrogen side-dressing management treatments were evaluated at each sowing date: control without N; complete nitrogen rate applied at phenological stages V5, V10 and VT; ½ N rate at V5 + ½ N rate at V10; and ⅓ N rate at V5 + ⅓ N rate at V10 + ⅓ N rate at VT. The N rate was equivalent to 300 kg ha-1. Grain yield ranged from 8.9 to 15.3 t ha-1 in Lages and from 7.4 to 16.4 t ha-1 in Atalanta. There were no significant differences in grain yield and agronomic efficiency of nitrogen use (AE) among the treatments with the entire N side-dressing fertilization at V5 and V10 and those when the nutrient was split into two or three times, regardless of sowing date. AE was higher when the crop was sown at the preferential sowing date than in the late sowing date, regardless of N side-dressing application. The splitting of nitrogen fertilization up to the crop tasseling did not increase maize grain yield or AE.

RESUMO A tolerância da soja à desfolha pode ser afetada pelo grupo de maturação relativa (GMR) da cultivar. Este trabalho foi conduzido objetivando avaliar os efeitos da desfolha artificial nas fases vegetativa e reprodutiva sobre o desempenho agronômico de cultivares de soja com diferentes grupos de maturação. Foram conduzidos dois experimentos em casa de vegetação, no município de Lages, SC. No primeiro a desfolha foi realizada em V6 e no segundo em R3. Avaliaram-se três cultivares com grupos de maturação relativa (GMR) contrastantes: BMX Veloz (GM 5.0, hábito de crescimento indeterminado), NA 5909 (GM 5.9, hábito de crescimento indeterminado) e TMG 7262 (GM 6.2, hábito de crescimento semideterminado). Cada cultivar foi submetida a cinco níveis de desolha: 0%, 16,6%, 33,3%, 50% e 66,6%. Avaliou-se a expansão foliar após a desfolha, o rendimento de grãos e seus componentes. A cultivar BMX Veloz apresentou menor capacidade de expansão foliar e menor rendimento de grãos do que as demais cultivares quando desfolhada em V6. O rendimento de grãos das três cultivares somente sofreu decréscimos significativos com desfolhas superiores a 16,6% em R3. Portanto, a cultivar BMX Veloz é menos tolerante à desfolha na fase vegetativa do que as cultivares NA 5909 e TMG 7262. O grupo de maturação da cultivar não interfere na tolerância da soja à desfolha na fase reprodutiva sob condições de casa de vegetação.

ABSTRACT Soybean tolerance to defoliation may be affected by relative maturity group (RMG) of the cultivar. For this reason, this study was carried out to evaluate the effects of artificial defoliation at vegetative and reproductive stages on the agronomic performance of soybean cultivars with different RMG. Two experiments were carried out in greenhouse conditions in Lages, Santa Catarina State, Brazil. Defoliation was carried out at V6 in the first experiment and at R3 in the second experiment. Three cultivars with contrasting RMG were used: BMX Veloz (RMG of 5.0, indeterminate growth habit), NA 5909 (RMG of 5.9, indeterminate growth habit), and TMG 7262 (RMG of 6.2, semi-determinate growth habit). Each cultivar was submitted to five defoliation levels: 0.0, 16.6, 33.3, 50.0, and 66.6%. Leaf expansion after defoliation, grain yield and its components were determined. The BMX Veloz showed lower leaf expansion capacity and lower grain yield when compared to the other cultivars when defoliated at V6. Grain yield of the three cultivars only showed significant decreases with defoliation levels higher than 16.6% at R3. The cultivar BMX Veloz is less tolerant to defoliation during the vegetative stage when compared to the cultivars NA 5909 and TMG 7262. Cultivar maturity group does not interfere with soybean tolerance to defoliation at the reproductive stage in greenhouse conditions.

RESUMO Doses de nitrogênio (N) em cobertura podem alterar o desempenho da cultura do milho segunda safra, e essa resposta pode variar se o milho for cultivado solteiro ou consorciado com espécies de gramíneas ou leguminosas. Objetivou-se avaliar o efeito de doses de N aplicadas em cobertura no crescimento e desempenho produtivo de milho segunda safra solteiro e consorciado com braquiária (Urochloa ruziziensis) ou crotalária (Crotalaria spectabilis). O delineamento experimental foi em blocos casualizados, com parcelas subdivididas e quatro repetições. As parcelas foram constituídas pelo milho solteiro, consorciado com braquiária ou com crotalária, e as subparcelas pelas doses de N (0, 60, 120, 180 e 240 kg ha-1). As variáveis avaliadas foram: índice SPAD em R1; índice de vegetação por diferença normalizada em V4 e V7; área foliar em R1; massa seca de folha e total do milho em R1; massa seca de grão e total do milho em R6; número de espigas por planta e de grãos por espiga; massa de mil grãos; e produtividade de grãos. Na ausência de adubação nitrogenada e com uso de 60 kg ha-1 de N em cobertura, o consórcio com U. ruziziensis reduz o crescimento e o desempenho produtivo de milho segunda safra. A adubação nitrogenada de cobertura no milho segunda safra em consórcio com U. ruziziensis minimiza a competição da forrageira sobre o crescimento do milho e proporciona, a partir de 120 kg ha-1 de N, desempenho produtivo similar ao do cereal solteiro. O consórcio com C. spectabilis não altera o crescimento e o desempenho produtivo do milho, bem como a resposta a doses de N aplicadas em cobertura, em relação ao milho solteiro, na segunda safra.

ABSTRACT Topdressing nitrogen (N) rates may alter the second-crop corn performance, and this response may vary if the corn is grown single or intercropped with grass or leguminous species. This study aimed to evaluate the effect of topdressing N rates on the growth and productive performance of second-crop corn grown single or intercropped with ruzigrass (Urochloa ruziziensis) or showy rattlebox (Crotalaria spectabilis). The experiment was carried out in a randomized block design, with a split-plot arrangement and four replications. The plots consisted of corn grown single or intercropped with ruzigrass or showy rattlebox, while the subplots consisted of N rates (0, 60, 120, 180 and 240 kg ha-1). The evaluated variables were: SPAD index at R1; normalized difference vegetation index at V4 and V7; leaf area at R1; leaf and total corn dry mass at R1; grain and total corn dry mass at R6; number of ears per plant and grains per ear; 1,000-grain mass; and grain yield. In the absence of N fertilization and with topdressing of 60 kg ha-1 of N, the intercropping with U. ruziziensis reduces the growth and productive performance of second-crop corn. The topdressing N fertilization for second-crop corn intercropped with U. ruziziensis minimizes the forage competition on corn growth and provides a productive performance similar to monocropping from 120 kg ha-1 of N. The intercropping with C. spectabilis does not change the corn growth and productive performance, as well as the response to the topdressing N rates, when compared to monocropping, in the second crop cultivation.

ABSTRACT Stalk rots compromise the translocation of water and nutrients, affecting grain filling. This study aimed to quantify the incidence of stalk rots in corn hybrids depending on sowing time and nitrogen topdressing rate, and to assess any correlation with grain yield. The experiment was conducted under field conditions in Atalanta, Santa Catarina state, Brazil, using a split-split-plot randomized block design. The hybrids AG 9025 PRO3 (super-early) and 30F53 VYH (early) were sown in the preferential (September 20) and late (December 5) sowing seasons with four nitrogen rates (0, 150, 300, and 450 kg·ha–1). The population density was 75,000 plants·ha–1 andthe nitrogen topdressing was carried out at the V4, V8, and V12 stages. The fungus Colletotrichum graminicola predominated in both hybrids and its presence was negatively correlated with stalk diameter and yield. The hybrid AG9025 PRO3 was more susceptible to stalk rot (35.1%) than the hybrid 30F53 VYH (8.8%). A higher incidence of stalk rot was observed in the late sowing season (31.1%) than in the preferential sowing season (11.2%). A decrease in the incidence of stalk rot was observed in the hybrid AG9025 PRO3 as nitrogen rates increased, but this behavior was not clearly observed in the hybrid 30F53 VYH.

RESUMO A podridão da espiga de giberela (PEG) do milho causada pelo complexo de espécies de Fusarium graminearum é uma doença destrutiva no sul do Brasil e no mundo. Cinco experimentos de campo foram conduzidos para determinar a eficácia de fungicidas, produtividade e qualidade de grãos (estudo I) e resposta do aumento de doses (estudo II) no controle de PEG, rendimento de grãos (RG) e grãos avariados (GA) em milho durante as safras 2014/15 e 2015/16. Os fungicidas foram pulverizados 48 horas antes (ação preventiva) ou 48 horas após (ação curativa) a inoculação de dois isolados de Fusarium meridionale (PR e MG). O estudo I consistiu na aplicação de nove ingredientes ativos (metconazol, piraclostrobina, tebuconazol, trifloxistrobina, protioconazol, tiofanato-metílico, azoxistrobina, ciproconazol e carbendazim) em oito formulações comerciais em duas épocas de semeadura do milho. O estudo II consistiu em uma aplicação de três fungicidas em doses crescentes e avaliadas em três datas de semeadura com apenas o isolado PR. No estudo I, não foram observadas diferenças entre fungicidas quando as variáveis PEG, RG e GA foram analisadas em conjunto. Houve interações entre o tempo de aplicação dos fungicidas e os isolados de F. meridionale quando a severidade de PEG e RG foram consideradas. A aplicação preventiva dos fungicidas em diferentes datas de semeadura e o uso do isolado de MG reduziu a PEG em 11,6% e aumentou o RG em 5,3% em comparação a aplicação curativa. No estudo II, houve interação significativa entre fungicidas e tempo de aplicação para GER, RG e GA. A aplicação preventiva de trifloxistrobina + protioconazol (0,15 + 0,17 e 0,22 + 0,26 L ha-1), piraclostrobina + metconazol (0,19 + 0,12 e 0,29 + 0,18 L ha-1) e carbendazim (2 L ha-1) reduziram GER em 41 e 50%; 47 e 54%; 54% nas três datas de semeadura, respectivamente. Houve aumento no RG de 45,7% e 46,8% quando trifloxistrobina + protioconazol (0,15 + 0,17 e 0,22 + 0,26 L ha-1), respectivamente, foi pulverizado preventivamente nas três épocas de semeadura em comparação ao tratamento controle. Trifloxistrobina + protiocanazole, piraclostrobina + metconazole e carbendazim (1,0 e 2,0 L ha-1) pulverizados nas duas doses preventivamente reduziram a incidência de GA em 53,5 e 48,7%; 47,7 e 57,5%; 48,1 e 50,5%, respectivamente, para cada fungicida e dose, e podem ser incorporados em um programa de manejo de doenças.

ABSTRACT Gibberella ear rot (GER) in maize, caused by Fusarium graminearum species complex, is a destructive disease in southern Brazil and worldwide. Five field-experiments were conducted to determine fungicide efficacy, grain yield and grain quality (study I), as well as response of increasing rates (study II) on GER control, grain yield (GY) and grain damage (GD) in maize during the 2014/15 and 2015/16 growing seasons. Fungicides were sprayed 48 h before (preventive action) or 48 h after (curative action) inoculation of two Fusarium meridionale isolates (PR and MG). Study I consisted in applying nine active ingredients (metconazole, pyraclostrobin, tebuconazole, trifloxystrobin, prothioconazole, thiophanate-methyl, azoxystrobin, cyproconazole and carbendazim) present in eight commercial formulations at two sowing dates. Study II consisted in applying increasing rates of three fungicides evaluated at three sowing dates using only PR isolate. In study I, no differences were observed among fungicides when the variables GER, GY and GD were analyzed together. There were interactions between time of fungicide application and F. meridionale isolates when GER severity and GY were considered. Preventive fungicide application at different sowing dates and the use of MG isolate reduced GER by 11.6% and increased GY by 5.3%, compared to curative application. In study II, there was a significant interaction between fungicides and application time for GER, GY and GD. Preventive application of trifloxystrobin + prothioconazole (0.15 + 0.17 and 0.22 + 0.26 L ha-1), pyraclostrobin + metconazole (0.19 + 0.12 and 0.29 + 0.18 L ha-1) and carbendazim (2 L ha-1) reduced GER by 41 and 50%, 47 and 54%, and 54% at the three sowing dates, respectively. There was an increment of 45.7% and 46.8% in GY when trifloxystrobin + prothioconazole (0.15 + 0.17 and 0.22 + 0.26 L ha-1), respectively, were preventively sprayed at the three sowing dates, compared to the control treatment. Trifloxystrobin + prothiocanazole, pyraclostrobin + metconazole and carbendazim (1.0 and 2.0 L ha-1) preventively sprayed at two rates reduced GD incidence by 53.5 and 48.7%, 47.7 and 57.5%, 48.1 and 50.5%, respectively, for each fungicide and rate, and could be incorporated into a disease management program.

ABSTRACT Currently, most nitrogen fertilizer is side-dressed when corn is in the four (V4) to eight (V8) expanded leaf stage. However, recent studies have shown that modern hybrids take up high amounts of nitrogen during grain filling. This indicates that a late nitrogen fertilization, at the time of crop flowering, may be important to optimize corn agronomic performance. This study aimed to evaluate the effect of the timing and splitting of nitrogen side-dress application on the agronomic performance of early corn hybrids in order to achieve high grain yield. The experiment was set in Lages, Santa Catarina, in the South of Brazil, during the 2014/2015 and 2015/2016 growing seasons. A randomized block design arranged in split plots was used. Two hybrids were tested in the main plots: P1680YH (very early) and P30F53YH (early). Six nitrogen side-dress systems were assessed in the split plots: control (without N), full N rate applied at V5, full N rate applied at V10, 1/2 N rate applied at V5 and 1/2 at V10, 1/3 N rate applied at V5, 1/3 at V10 and 1/3 at VT; and the whole N rate applied at VT. The nitrogen rate was 300 kg ha-1 N. Urea was used as the nitrogen source. Total grain yield and yield components, agronomic nitrogen use efficiency, and leaf area were determined. Grain yield ranged from 6,422 to 15,426 kg ha-1 in 2014/2015 and from 9,283 to 14,986 in 2015/2016. Nitrogen side-dress application performed one time at V5 or V10 or split into two or three applications at different growth stages had similar grain yield, number of ears per plant, kernels per ear, and 1,000 grain dry weight. Nitrogen side-dressed entirely at VT led to higher grain yield than the control. However, grain yield and agronomic nitrogen use efficiency were lower in this treatment than in the treatments involving the other growth stages of side-dress nitrogen. The early hybrid was higher yielding than the very early hybrid, regardless of the timing of nitrogen fertilization. Splitting of nitrogen fertilization up to tasseling was not an effective strategy to increase grain yield and agronomic nitrogen use efficiency of the corn hybrids P30F53YH and P1680YH.

ABSTRACT. An uneven distribution of maize plants at the sowing row can decrease grain yield. This work was carried out to evaluate the effect of an increasing nitrogen rate on maize agronomic performance under different variation coefficients of plant spatial distributions at the sowing row. The experiment was conducted in Lages, Santa Catarina State, South Brazil. Three variation coefficients (VC) of plant spatial distribution (0, 50, and 100%) were tested. At the 0 level, seeds were evenly distributed 17 cm from each other. In the other treatments with uneven spatial distributions, the distances between two neighbouring seeds ranged from 2 to 54 cm. Four nitrogen side-dress rates (0, 125, 250, and 375 kg N ha-1) were evaluated. The increase in VC of plant spatial distribution decreased the leaf area and the relative chlorophyll content of the index leaf at silking, regardless of the nitrogen rate. When the variation coefficient of seed placement was enhanced from 0 to 100%, such behaviour contributed to a decrease in the number of kernels per ear and the grain yield. Therefore, increasing the amount of N was not an efficient strategy for preventing yield losses caused by irregular plant spatial distribution at the sowing row.