Qualidade industrial do trigo em função do trinexapac-ethyl e doses de nitrogênio Industrial quality of wheat as a function of trinexapac-ethyl and nitrogen doses

Objetivou-se, neste trabalho, avaliar a época de aplicação do redutor de crescimento trinexapac-ethyl e de doses de nitrogênio no rendimento de grãos e qualidade industrial das cultivares de trigo Avante e BRS 177. O delineamento experimental foi blocos ao acaso em esquema fatorial 4 x 4, com quatro repetições. Os tratamentos constaram de épocas de aplicação de trinexapac-ethyl (100 g ha-1 entre o primeiro e o segundo nó visível do trigo; 100 g ha-1 entre o segundo e terceiro nó visível; aplicação sequencial de 50 g ha-1 em cada uma das fases anteriores; testemunha sem aplicação) e de doses de nitrogênio em cobertura (90, 135, 180 e 225 kg ha-1 para a cultivar Avante e 60, 80, 120 e 150 kg ha-1 para a cultivar BRS 177). Avaliaram-se características agronômicas, acamamento, componentes de rendimento, rendimento de grãos, qualidade do grão e da farinha. O trinexapac-ethyl, independentemente da época de aplicação, reduziu a estatura das plantas e a porcentagem de acamamento, com resposta diferencial no rendimento de grãos e sem influência substancial na qualidade industrial do trigo. O aumento nas doses de nitrogênio promoveu maior acamamento, afetou a qualidade do grão e da farinha da cultivar BRS 177, mas sem efeitos no rendimento de grãos.<br>The objective of this work was to evaluate the application time of the trinexapac-ethyl growth reducer and of nitrogen rates in the yield and industrial quality of the wheat cultivars Avante and BRS 177. The experimental design was complete randomized blocks in a 4 x 4 factorial scheme, with four replicates. The treatments consisted of periods of trinexapac-ethyl application (100 g ha-1 between the first and second visible node of the wheat; 100 g ha-1 between the second and third visible node; sequential application of 50 g ha-1 in each one of the previous phases; without application) and of nitrogen rates in covering (90, 135, 180 and 225 kg ha-1 for Avante cultivar and 60, 80, 120 and 150 kg ha-1 for BRS 177 cultivar). The following characteristics were evaluated: agronomical characteristic, lodging, yield components, yield, grain and flour quality. Trinexapac-ethyl, independently of the application time, reduced plant height and the lodging percentage, with different response in the yield and without substantial influence on the industrial quality of the wheat. The increase in the nitrogen rates promoted higher lodging, affected the grain and flour quality of BRS 177 cultivar and had no effect on yield

GPS receivers for georeferencing of spatial variability of soil attributes Receptores GPS para georreferenciamento da variabilidade espacial de atributos do solo

The characterization of the spatial variability of soil attributes is essential to support agricultural practices in a sustainable manner. The use of geostatistics to characterize spatial variability of these attributes, such as soil resistance to penetration (RP) and gravimetric soil moisture (GM) is now usual practice in precision agriculture. The result of geostatistical analysis is dependent on the sample density and other factors according to the georeferencing methodology used. Thus, this study aimed to compare two methods of georeferencing to characterize the spatial variability of RP and GM as well as the spatial correlation of these variables. Sampling grid of 60 points spaced 20 m was used. For RP measurements, an electronic penetrometer was used and to determine the GM, a Dutch auger (0.0-0.1 m depth) was used. The samples were georeferenced using a GPS navigation receiver, Simple Point Positioning (SPP) with navigation GPS receiver, and Semi-Kinematic Relative Positioning (SKRP) with an L1 geodetic GPS receiver. The results indicated that the georeferencing conducted by PPS did not affect the characterization of spatial variability of RP or GM, neither the spatial structure relationship of these attributes.<br>A caracterização da variabilidade espacial dos atributos do solo é indispensável para subsidiar práticas agrícolas de maneira sustentável. A utilização da geoestatística para caracterizar a variabilidade espacial desses atributos, como a resistência mecânica do solo à penetração (RP) e a umidade gravimétrica do solo (UG), é, hoje, prática usual na agricultura de precisão. O resultado da análise geoestatística é dependente da densidade amostral e de outros fatores, como o método de georreferencimento utilizado. Desta forma, o presente trabalho teve como objetivo comparar dois métodos de georreferenciamento para a caracterização da variabilidade espacial da RP e da UG, bem como a correlação espacial dessas variáveis. Foi implantada uma malha amostral de 60 pontos, espaçados em 20 m. Para as medições da RP, utilizou-se de penetrógrafo eletrônico e, para a determinação da UG, utilizou-se de trado holandês (profundidade de 0,0-0,1 m). As amostras foram georreferenciadas, utilizando-se do método de Posicionamento por Ponto Simples (PPS), com de (retirar) receptor GPS de navegação, e Posicionamento Relativo Semicinemático, com receptor GPS geodésico L1. Os resultados indicaram que o georreferenciamento realizado pelo PPS não interferiu na caracterização da variabilidade espacial da RP e da UG, assim como na estrutura espacial da relação dos atributos

Crescimento de folhas do capim-bermuda tifton 85 submetido à adubação nitrogenada após o corte Leaf growth of tifton 85 bermudagrass submitted to nitrogen fertilization after cutting

Com o objetivo de avaliar a influência de doses e épocas de aplicação de nitrogênio após o corte no fator de correção de área foliar, na taxa de alongamento de folhas e no comprimento e área da lâmina foliar do capim-bermuda tifton 85 (Cynodon spp) foram conduzidos dois experimentos em casa de vegetação. Ambos os experimentos foram estabelecidos em vasos com capacidade para 7 kg de terra, com solo classificado como Neossolo Quartzarênico Órtico típico, em esquema fatorial 4 × 2, para avaliação de quatro doses de nitrogênio (0, 80, 160 e 240 mg kg-1 de solo) e duas épocas de aplicação (imediatamente após o corte e sete dias após o corte das plantas). O delineamento experimental foi em blocos completos ao acaso, com quatro repetições. Com o fornecimento de nitrogênio, observou-se diminuição no fator de correção de área foliar. O nitrogênio proporciona variação positiva no comprimento foliar, na área da lâmina foliar e na taxa de alongamento da folha, variações que ocorreram em maior grandeza entre a não-aplicação de nitrogênio e a dose de 80 mg kg-1 de solo.<br>With the objective of evaluating the influence of nitrogen rates and application time after cutting on correction factor for leaf area, on leaf elongation rate and on blade leaf length and area of tifton 85 bermudagrass (Cynodon spp), two experiments were carried out in a greenhouse. Both experiments were established in pots with capacity for 7 kg of soil classified as Entisol, in a 4 × 2 factorial scheme, for evaluation of four nitrogen rates (0, 80, 160 and 240 mg kg-1 of soil) and two application times (immediately after cutting and seven days after cutting of the plants). It was used a complete randomized block design, with four replications. As nitrogen was supplied, it was observed a decrease in the correction factor for leaf area. There is a predominance of positive effects of nitrogen on leaf length, on leaf blade area and on leaf elongation rate. Great nitrogen effect was observed when comparying no-nitrogen application with the rate of 80 mg kg-1 of soil

Spatial relationships between soil attributes and corn yield in no-tillage system

Soil properties play an important role in spatial variability of crop yield. However, a low spatial correlation has generally been observed between maps of crop yield and of soil properties. The objectives of the present investigation were to assess the spatial pattern variability of soil properties and of corn yield at the same sampling intensity, and evaluate its cause-and-effect relationships. The experimental site was structured in a grid of 100 referenced points, spaced at 10 m intervals along four parallel 250 m long rows spaced 4.5 m apart. Thus, points formed a rectangle containing four columns and 25 rows. Therefore, each sampling cell encompassed an area of 45 m² and consisted of five 10 m long crop rows, in which the referenced points represented the center. Samples were taken from the layers 0-0.1 m and 0.1-0.2 m. Soil physical and chemical properties were evaluated. Statistical analyses consisted of data description and geostatistics. The spatial dependence of corn yield and soil properties was confirmed. The hypothesis of this study was confirmed, i.e., when sampling the soil to determine the values of soil characteristics at similar to sampling intensity as for crop yield assessments, correlations between the spatial distribution of soil characteristics and crop yield were observed. The spatial distribution pattern of soil properties explained 65 % of the spatial distribution pattern of corn yield. The spatial distribution pattern of clay content and percentage of soil base saturation explained most of the spatial distribution pattern of corn yield

Structural and productive characteristics of Marandu and Xaraés grasses fertilized at different times after harvesting

The objective of this study was to assess the effect of applying N and K2O at different times after harvest on the structure and production characteristics of Marandu and Xaraés cultivars of Brachiaria brizantha. Two greenhouse 4 × 2 factorial experiments using a randomized block design with eight treatments and four replicates were carried out. In experiment 1, the plants in pots were fertilized weekly with 50 mg/dm³ of N and K2O until a week before a uniformity cut, for a total of four applications. After cutting, plants were fertilized with 50 mg/dm³ of N and K2O at 0, 3, 6, and 9 days. Cultivars were evaluated after 44 days of regrowth. In experiment 2, a single 50 mg/dm³ dose of N and K2O was applied a week before the uniformity cut, and 100 mg/dm³ of N and K2O were applied at 0, 4, 8, and 12 days after cutting; cultivars were evaluated after 39 days of regrowth. In experiment 1, the leaf/stem ratio and dry matter yield were influenced by the time at which fertilizers were applied. In the second experiment, the total number of leaves, expanded leaves, dead leaves, and the leaf lamina accumulated length and dry matter production were influenced by the time at which fertilizers were applied. Marandugrass had more leaves and tillers than cv. Xaraés, which, in turn, had greater height, dry matter yield and regrowth vigor. Applying nitrogen and potassium fertilizer immediately after cutting improves the structural characteristics, while the dry matter yield is maximized by applying fertilizers immediately after cutting by using lower doses of N, or at 4.5 days after cutting by using higher doses of N