The utilization of Normalized Difference Vegetation Index (NDVI) data obtained through satellite images can technically improve the process of delimiting management zones (MZ) for annual crops, resulting in socioeconomic and environmental benefits. The aim of this study was to compare delimited MZ, using crop productivity data, with delimited MZ using the NDVI obtained from satellite images in areas under a no-tillage system. The study was carried out in three areas located in the state of Rio Grande do Sul, Brazil. Three crop productivity maps, from 2009 to 2015, were used for each area, whereby the NDVI was calculated for each crop productivity map using images from the Landsat series of satellites. Descriptive and geostatistical analysis were conducted to determine the productivity and NDVI data. The MZ were then delimited using the fuzzy c-means algorithm. Spearman's correlation matrix was used to compare the methodologies used for delimiting the MZ. The MZ based on NDVI calculated from the satellite images correlated with the MZ based on crop productivity data (0.48 < r < 0.61), suggesting that the NDVI can replace or be complementary to productivity data in delimiting MZ for annual cropping systems.

Nitrogen (N) is a dynamic element in the soil, so new nitrogen fertilization alternatives are required as a way of maximizing its efficiency. Besides, vegetation sensors are a way to assess and manage the nutritional demands of plants. This study aimed to evaluate the effect of nitrogen sources on photosynthetic pigments and their correlation with corn grain yield and dry biomass. The experiment was carried out in a randomized block design with nitrogen sources (mineral, organic and biological). Contents of chlorophyll a, b and total, as well as carotenoids, were evaluated. The chlorophyll indices evaluated by both methods were positively correlated with each other and with the grain yield per plant. Nitrogen fertilization 100 % mineral was superior, when compared to the other treatments, with increments of up to 44 %. There was a positive relationship between the methods of determining and estimating the chlorophyll contents. The grain yield per plant showed the highest values when using the 100 % mineral fertilizer source, with increments above 10 %, in relation to the other sources, spending US$ 89.77 on fertilizer and earning over US$ 538.60 on grain yield. There was a positive correlation between the photosynthetic pigments obtained by both methods and grain yield per plant. Both methods are recommended for the evaluation of chlorophyll concentrations.

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For years, the impacts of using cover crops in productive systems have been measured by their relation with soil chemical and physical characteristics. Consequently, the effects on the soil microbiological characteristics have been little explored. This research aimed to measure the short-term effects of cover crop systems on the enzymatic activity of arylsulfatase and beta-glycosidase, as well as the wheat grain yield. Thirty-five cover crop systems (18 single and 17 intercropped) were implemented, with 3 replications of the following variables for each treatment: enzymatic activity of arylsulfatase and beta-glycosidase, soil organic matter and sulfur contents, and wheat grain yield. The data were submitted to descriptive analysis, multivariate cluster analysis by dendrograms for the single and intercropped plant systems, and t-test for independent samples between the average scores of each group in the dendrograms. Independently of the crop system, there were short-term effects on the enzymatic activity and grain yield. Plants from the same botanic family presented different effects among them. Therefore, in the short-term, cover crops affect the enzymatic activity, and plants that present a higher enzymatic activity do not necessarily result in higher grain yields.

O objetivo deste trabalho foi determinar a qualidade na distribuição de plantas de milho na linha de semeadura, na região do Planalto Médio do Estado do Rio Grande do Sul. O estudo foi realizado no ano agrícola 2018/19, em 23 áreas de cultivo de milho, sendo 14 em sistema irrigado e nove no sistema sequeiro, localizadas em 11 municípios gaúchos. Em cada área foi mensurada a distância longitudinal entre plantas de milho na linha de semeadura, em estádio vegetativo V3. Para tanto, foram avaliados 10 m de plantas, em três repetições, e os dados foram tabulados e distribuídos em: espaçamentos aceitáveis, duplos e falhos. De acordo com classificação proposta na literatura clássica, 56,5% das áreas avaliadas encontram-se em ótimo estado de distribuição de plantas na linha, 39,1% em bom estado, e 4,4% das áreas em estado regular de qualidade da semeadura do milho. Ao observar os dois sistemas de cultivo, as médias de espaçamentos aceitáveis foi de 87,0% para o sistema irrigado, e de 93,8% para o sequeiro. Pode-se concluir que, na maioria das áreas avaliadas, a qualidade da semeadura da cultura do milho na região do Planalto Médio é ótima.