ABSTRACT Nitrogen (N) fertilizer management is a key factor in the success of maize crops. The objective of this work was to evaluate the response of second-crop maize to N applied exclusively as topdressing or at planting + topdressing. Five experiments were conducted in areas in southwestern Goiás in 2019 and 2020 to evaluate N application rates of 0 and 30 kg ha-1 at planting, combined with five N rates applied as topdressing at the maize V3 stage over a total of 0, 75, 150, 225, and 300 kg ha-1. Dry matter production in the V6 or V9 stage and yield parameters at harvest were evaluated. N application did not affect the number of grain rows per ear but increased the number of grains per row and, particularly, grain weight. The crop responded positively to increases in the total N rate in 4 of the 5 experiments: in 1 of these experiments, N fertilizer application at planting contributed to an increase in the efficiency of topdressing fertilization, resulting in a higher maize yield with a lower total N rate; in the other 3, a positive maize response to N occurred when total N was applied as topdressing at V3. However, the highest mean maize grain yield (8,233 kg ha-1) was found in the trial that showed no response to N fertilizer application - probably due to the better chemical fertility conditions of the area combined with an adequate distribution of rainfall, considering the multiple factors involved in N application recommendations.

RESUMO O manejo de nitrogênio (N) na cultura do milho é fator chave para o sucesso de seu cultivo, de modo que se objetivou com esse estudo avaliar a resposta da cultura, em segunda safra, à doses de N aplicadas exclusivamente em cobertura ou na adubação de base (semeadura) complementada com a adubação de cobertura. Para tal, em 2019 e 2020 foram realizados cinco experimentos em áreas da região Sudoeste do Estado de Goiás, testando 0 e 30 kg ha-1 de N aplicados na base combinados com cinco doses totais de N (0, 75, 150, 225 e 300 kg ha-1) completadas em cobertura, quando as plantas estavam em estádio V3. Avaliou-se a produção de massa seca na fase vegetativa V6 ou V9, e, por ocasião da colheita, os parâmetros produtivos. Verificou que a aplicação de N não interfere no número de fileiras de grãos, mas aumenta o número de grãos por fileira e, principalmente, o peso de grãos. Em 4 dos 5 ensaios, a cultura respondeu positivamente ao incremento da dose total de N; em 1 desses, a adubação de base contribuiu para aumento da eficiência da adubação de cobertura, de modo que a produtividade do milho foi maior e atingida com uma dose total de N menor. Nos outros 3, respostas positivas foram observadas quando da aplicação total do N em cobertura e em dose única. A maior produtividade média de grãos de milho (8.233 kg ha-1), no entanto, ocorreu justamente no ensaio com ausência de resposta à adubação nitrogenada - provavelmente devido às melhores condições de fertilidade química da área aliada à adequada distribuição das chuvas, considerando assim múltiplos fatores para N recomendações de aplicação.

ABSTRACT Global consumption of oilseeds has been growing progressively in the last five growing seasons, in which soybean represents 60% of this sector. Thus, in order to maintain a high production in the region of Rio Verde, State of Goiás, against the phytopathological problems, this study aimed to define the best spectral range for the detection of H. glycines and P. brachyurus by linear regressions in soybean at R3 stage, as well as the elaboration of mathematical models through multiple linear regressions. For this, soil and root were sampled in the experimental area, as well as a flight was performed with the Sentera sensor. Data were used for the elaboration of regressions and for the validation of 2 mathematical models. Significant values were observed in simple linear regression only for cysts, in the visible range, with a good R² value for the Green, Red and 568 nm bands, to nonviable cysts. When working with the stepwise statistics, better results are found for H. glycines, which now has an R²(aj) of 0.7430 and P. brachyurus is then detected. From the mathematical model obtained with the multiple linear regression for non-viable cysts with an R²(aj) of 0.7430, it is possible to detect the spatial distribution of nematodes across the soybean field, in order to perform a localized management, optimizing the applications. Good results are also possible using the mathematical model obtained by simple linear regression.

ABSTRACT Images from unmanned aerial vehicles (UAV) can serve as a baseline for studies in weed science, complementing observations obtained in the ground. The objective of this work was to determine soybean (Glycine max (L.) Merr.) plant injury caused by pre-emergence herbicides in sandy and clayey soils, using a low-cost UAV. The experiment was conducted in a randomized complete block design, with four replicates and seven treatments consisted of herbicides (diclosulam, chlorimuron, sulfentrazone, flumioxazin, and S-metolachlor), hand weeded and untreated treatments. Ground-based evaluations were carried out to assess soybean crop injury, plant stand, leaf chlorophyll content, plant height, canopy distance and grain yield. Images were taken using a UAV equipped with an RGB (red green and blue) camera. Soybean plants sprayed with diclosulam had lower plant reflectance in the R (98.9), G (147.1) and B (74.3) range than the other treatments in sandy soil. In clayey soil, hand weeded treatment had higher plants (30.8 cm) and untreated favored smaller plants (24.9 cm) compared to herbicide treatments. In sandy soil, soybean yield of all treatments was similar, however in clayey soil, soybean yield treated with chlorimuron and flumioxazin was higher than 5000 kg ha-1 and better than the others treatments. The nutrient-poor soil (sandy) may have aggravated the plant injury caused by herbicides and explain the lower yield observed compared to clayey soil. It was determined soybean plant injury caused by pre-emergence herbicides with the use of unmanned aerial vehicles, providing complementary results to ground-based measurements, indicating the potential of this technology for low-cost evaluations in weed science.

RESUMEN Para mejorar el desarrollo de cultivos, se recomiendan sustratos comerciales indistintamente del tipo de cultivo y/o variedad sin considerar sus características y necesidades. Por lo tanto, se debe estudiar su composición y condición nutricional para cada tipo de planta en su etapa inicial. El objetivo de este estudio fue evaluar el desarrollo del sistema de brotes y raíces de dos cultivares de lechuga producidos en 10 sustratos diferentes. Los cultivares Great Lakes y Simpson Black Seed se evaluaron en 10 sustratos formulados mezclando un sustrato comercial, compuestos orgánicos (cerdos, ganado y aves de corral) y bagazo de caña de azúcar. El cultivar Great Lakes tuvo un mayor desarrollo de la parte aérea, mientras que el cultivar Simpson Black Seed tuvo un sistema de raíces más robusto. El sustrato que contenía los residuos provenientes de cerdos y aves fue el que favoreció el desarrollo de la parte aérea de las plántulas y la lechuga, mientras que los que contenían el 33% del bagazo de caña de azúcar fueron los que favorecieron el desarrollo del sistema radicular. El sustrato comercial utilizado de forma aislada, mostró el rendimiento más bajo.

ABSTRACT To improve crop development, commercial substrates are recommended without distinction for different crops and/or varieties without considering their characteristics and needs; therefore, their composition and nutritional condition must be studied for each type of plant in its initial formation. The objective of this study was to evaluate the development of shoot and root systems of two lettuce cultivars produced in 10 different substrates. Great Lakes and Simpson Black Seed cultivars were evaluated in 10 substrates formulated by mixing a commercial substrate, organic compounds (swine, cattle, poultry) and sugarcane bagasse. Great Lakes cultivar had a higher development of the aerial part, whereas Simpson Black Seed cultivar had a more robust root system. The substrate with swine and poultry favored the development of the aerial part of the seedlings and lettuce, while the substrates with 33% of sugarcane bagasse improved the development of the root system. The commercial substrate used in isolation showed the lowest performance.

RESUMO: A soja é uma das principais espécies de planta cultivadas no mundo. Todavia, perdas de produtividade são ocasionadas por vários tipos de estresses, incluindo os nematoides H. glycines e P. brachyurus. Como objetivo, buscou-se determinar a melhor banda espectral para a detecção do H. glycines e P. brachyurus com o uso de modelos de regressões lineares simples e definir um modelo matemático de regressão linear múltiplo para sua detecção, no início do florescimento (R1). Para isto, foram definidos nove pontos de coleta em cinco reboleiras, totalizando 45 pontos. As coletas foram feitas em um padrão específico de distâncias, de forma a ter amostras com tipos variados de populações de nematoides. Foram realizados voos com o Phantom 4 Advanced, Sequoia e Sentera sobre cada uma das reboleiras. O comprimento de onda do vermelho melhor explicou a variabilidade dos dados para H. glycines no solo e na raiz, bem como dos juvenis de segundo estádio no solo. Para P. brachyurus, a RedEdge da Sentera foi a que explicou melhor a variabilidade dos dados para nematoide na raiz e a NIR da Sequoia a que melhor explicou para juvenis no solo. Quando se utilizou um modelo matemático para a detecção do P. brachyurus e H. glycines, percebe-se uma grande melhora no R² e p-valor com relação às regressões lineares simples. No início da floração (R1), a refletância espectral da soja foi associada ao número de H. glycines e P. brachyurus no solo e nas raízes, usando sensores de baixo custo e multiespectrais.

ABSTRACT: Soybean is one of the main crop species grown in the world. However, there is a decline in productivity due to the various types of stress, including the nematodes Heterodera glycines and Pratylenchus brachyurus. The objectives were to determine the best spectral band for detecting H. glycines and P. brachyurus at the beginning of flowering (R1). Soil and root sampling was conducted at nine sampling sites in each of the five nematode-infested regions, totaling 45 sampling points. Flights were made at all regions using Phantom 4 Advanced, Sequoia and 14-band customized Sentera. For H. glycines, the red spectral band best explained the variability on soil and root nematode counts as well as the second stage of juveniles in soil. For P. brachyurus, Sentera RedEdge best explained the variability in root nematode counts and Sequoia NIR best explained soil juveniles. A multiple linear regression model using spectral data for detecting P. brachyurus and H. glycines improved R² compared to simple linear regressions. At flowering growth stage (R1), soybean spectral reflectance was associated with the number of H. glycines and P. brachyurus on soil and roots using low-cost and multispectral sensors.

RESUMO O sorgo biomassa [Sorghum bicolor (L.) Moench] é uma fonte renovável muito promissora para a produção de energia obtida por processos de cogeração e fermentação. Alguns aspectos do manejo da adubação para esta cultura, no entanto, devem ser melhor entendidos. Objetivou-se determinar a marcha de acúmulo de massa seca e de macro e micronutrientes em estádios fenológicos da cultura do sorgo biomassa (Palo Alto 2562), bem como estabelecer a ordem de acúmulo. O delineamento experimental utilizado foi o de blocos ao acaso, com quatro repetições. A fim de determinar a curva de acúmulo de massa seca e nutrientes, as plantas foram amostradas em nove estádios fenológicos (V1, V3, V5, V7, V9, V11, emborrachamento, florescimento e colheita). Analisou-se o acúmulo de massa seca e de N, P, K, Ca, Mg, S, Cu, Fe, Mn e Zn. O máximo acúmulo de massa seca foi de 24.853 kg ha-1. O K foi o nutriente absorvido em maior quantidade (447 kg ha-1), o que demonstra a alta capacidade da planta em absorver tal nutriente. O N foi o segundo nutriente mais acumulado pela planta (289 kg ha-1), e o seu padrão de absorção sugere que o seu fornecimento deve ser realizado até o estádio V7. Conclui-se, ainda, que a ordem de extração e acúmulo de macro e micronutrientes para a cultura do sorgo biomassa é a seguinte: K > N > Ca > Mg > S > P > Fe > Zn > Mn > Cu.

ABSTRACT Biomass sorghum [Sorghum bicolor (L.) Moench] is a very promising renewable source to produce energy obtained by cogeneration and fermentation processes. However, some aspects of the fertilizer management for this crop should be better understood. This study aimed to determine the accumulation progress of dry matter and macro and micronutrients in phenological stages of the biomass sorghum (Palo Alto 2562) crop, as well as to establish the accumulation order. The experiment was performed in a randomized block design, with four replicates. In order to determine the dry matter and nutrient accumulation curves, the plants were sampled in nine phenological stages (V1, V3, V5, V7, V9, V11, booting, flowering and harvest). Dry matter and N, P, K, Ca, Mg, S, Cu, Fe, Mn and Zn accumulations were analyzed. The maximum dry matter accumulation was 24,853 kg ha-1. K was the nutrient absorbed in the highest amount (447 kg ha-1), what demonstrates the high capacity of the plant to absorb this nutrient. N was the second most accumulated nutrient by the plant (289 kg ha-1) and its absorption pattern suggests that it should be supplied up to the V7 stage. It was also possible to conclude that the order of extraction and accumulation of macro and micronutrients for the biomass sorghum crops is: K > N > Ca > Mg > S > P > Fe > Zn > Mn > Cu.