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One of the most critical aspects of agricultural experimentation is the proper choice of experimental design to control field heterogeneity, especially for large experiments. However, even with complex experimental designs, spatial variability may not be properly controlled if it occurs at scales smaller than blocks. Therefore, modeling spatial variability can be beneficial, and some studies even propose spatial modeling instead of experimental design. Our goal was to evaluate the effects of experimental design, spatial modeling, and a combination of both under real field conditions using GIS and simulating experiments. Yield data from cultivars was simulated using real spatial variability from a large uniformity trial of 100 independent locations and different sizes of experiments for four experimental designs: completely randomized design (CRD), randomized complete block design (RCBD), α‐lattice incomplete block design (ALPHA), and partially replicated design (PREP). Each realization was analyzed using different levels of spatial correction. Models were compared by precision, accuracy, and the recovery of superior genotypes. For moderate and large experiment sizes, ALPHA was the best experimental design in terms of precision and accuracy. In most situations, models that included spatial correlation were better than models with no spatial correlation, but they did not outperformed better experimental designs. Therefore, spatial modeling is not a substitute for good experimental design.

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-Grazing livestock in integrated crop-livestock systems can cause impacts in the subsequent crop cycle. Aiming to investigate how grazing could affect soybean, the 9th crop cycle of a pasture/soybean rotation was assessed. Treatments were grazing intensities (10, 20, 30 and 40 cm of sward height) applied since 2001 in a mixed of oat and annual ryegrass; and an additional no grazing area as control. Treatments were arranged in a completely randomized block design with three replicates. Grazing affected soybean population and the mass of individual nodules (P<0.05), while the number and mass of nodules per plant were similar (P>0.05). Soybean yield showed differences among treatments, but no difference was found between grazed and non-grazed areas. Grazing intensities impact the coverage and frequency of weeds (P>0.05). In conclusion, grazing intensity impacts different parameters of soybean yield and development, but only the grazing intensity of 10 cm can jeopardize the succeeding soybean crop.

Leaf appearance rate and phyllochron are related variables which play a central role in forage production. Phyllochron is the time interval between the appearance of successive leaves and varies according to a number of environmental factors, among which temperature is the most important. The experiment was conducted in natural pasture with the aim of testing phyllochron variation under different seasons, herbage allowances, and topographic positions. Marked tillers were used to define the phyllochron, establishing a relationship between the number of leaves produced against thermal time during the sampling period. The time (expressed in °C) needed for the emergence of a leaf is equal to 1/b, where b is the slope coefficient of the regression. The lines for the season combinations, herbage allowances and topographic positions sampled were compared. Under Spring and Summer conditions, the phyllochrons for P. notatum and C. selloana were 156°C and 238°C respectively, regardless of treatment. Key words: morphogenesis, leaf appearance, native grassland FILOCRONO DE Paspalum notatum FL. E Coelorhachis selloana (HACK.) CAMUS EM PASTAGEM NATURALRESUMO: A taxa de aparecimento de folhas (TAF) e o filocrono são conceitos associados, que exercem forte influência na produção de forragem. O filocrono é o intervalo de tempo entre o aparecimento de duas folhas sucessivas acima do pseudocaule e varia de acordo com alguns fatores ambientais, sendo a temperatura o fator determinante. O experimento foi conduzido em pastagem natural em Eldorado do Sul, RS, com o objetivo de testar a variação no filocrono em diferentes estações do ano, níveis de oferta de forragem (NOF) e posições topográficas (PT). Para a definição do filocrono, foram amostrados perfilhos marcados e estabeleceuse a relação entre número de folhas produzidas e a soma térmica do período amostral. A soma térmica (em°C ) necessária para que a planta emita uma folha é igual a 1/b, sendo b o coeficiente angular verificado na regressão. As retas obtidas para as combinações entre estações, NOF e PT foram comparadas. Em condições de primavera e verão, se obteve filocrono de 156°C para P. notatum e de 238°C para C. selloana, independentemente dos tratamentos avaliados. Palavras-chave: morfogênese, aparecimento de folhas, pastagem nativa

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