A B S T R A C TThe knowledge on the spatial variability of soil properties and crops is important for decision-making on agricultural management. The objective of this study was to evaluate the spatial variability of soil fertility and its relation with cocoa yield. The study was conducted over 14 months in an area cultivated with cocoa. A sampling grid was created to study soil chemical properties and cocoa yield (stratified in season, off-season and annual). The data were analyzed using descriptive and exploratory statistics, and geostatistics. The chemical attributes were classified using fuzzy logic to generate a soil fertility map, which was correlated with maps of crop yield. The soil of the area, except for the western region, showed possibilities ranging from medium to high for cocoa cultivation. Soil fertility showed positive spatial correlation with cocoa yield, and its effect was predominant only for the off-season and annual cocoa.Variabilidade espacial da fertilidade do solo e sua relação com a produtividade do cacaueiro R E S U M O O conhecimento da variabilidade espacial das propriedades do solo e das culturas é importante para a tomada de decisão sobre o manejo agrícola. Objetivou-se, neste estudo, avaliar a variabilidade espacial da fertilidade do solo e sua relação com a produtividade do cacaueiro. O estudo foi realizado durante 14 meses em uma área cultivada com cacaueiros. Foram estudados, a partir de um grid amostral, os atributos químicos do solo e a produtividade do cacaueiro (estratificada em safra, temporão e anual). Os dados foram analisados pela estatística descritiva e pela geoestatística. Os atributos químicos foram classificados utilizando-se a lógica fuzzy, para construção de um mapa de fertilidade do solo, o qual foi correlacionado com os mapas das estratificações da produtividade. O solo da área, com exceção da região oeste, apresentou possibilidades de média a alta, para a condução da cultura do cacau. A fertilidade apresentou correlação espacial positiva com a produtividade do cacaueiro, sendo seu efeito preponderante para o cacau temporão e anual. Key words:precision agriculture cocoa spatial variability fuzzy logic Palavras-chave: agricultura de precisão cacau geoestatística lógica fuzzy

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In Brazil, arugula is a vegetable often consumed in salads because it provides a flavorful option when paired with blander lettuces and because it is considered rich in vitamins A and C, potassium, sulfur and iron. However, several aspects of fertilization management for this crop must be studied further. Thus, the objective of this work was to determine the growth and accumulation of macronutrients within arugula, under field conditions. The experiment was conducted in four parcels (vegetable beds) with dimensions of 5.0 x 0.2 x 1.3 m, located within an experimental area of 54 m² (6.0 x 9.0 m). The Arugula cv. Cultivated, with seedlings produced in a protected environment. Standard fertilization was performed with 160 kg ha -1 of N, 340 kg ha -1 of P2O5, 160 kg ha -1 of K2O, 20 kg ha -1 of S and 1 kg ha -1 of B. The treatments were constituted by different collection times at 7, 14, 21, 28, 35 and 42 days after the arugula seedlings transplanting. Between 18 and 38 days after the transplanting of the seedlings, a significant increment in the accumulation of dry matter occurred. In the period between 20 and 30 days after the transplanting, the greatest demand for most macronutrients occurred. The order of macronutrient accumulation by arugula at 42 days was as follows: K > N >Ca> P > Mg > S.

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One of the most important crop practices to obtain high grain and forage yields in maize is the correct management of the seeding density, because the plant stand can influence growth components, production and partitioning of photoassimilates. The objective of this study was to evaluate the growth and yield of corn cultivation at five spacings, using two hybrids. The experiment was installed at the experimental farm of the Federal University of Campina Grande, CCTA/UFCG, Campus de Pombal, located in the city of Santo Domingo-PB. The experimental design was a randomised complete block, in a factorial scheme, with the factors being five spacings and two hybrids, with four replications. The spacings were 0.15, 0.30, 0.45, 0.60 and 0.75 m between plants, and the two hybrids were 'AG-1051' and 'BR-106'. The following yield components were evaluated: ear weight with straw and without straw; weight of 1000 seeds, ear length and diameter, grain yield and mass of corn. The spacings of 0.30 and 0.45 m had the best results, corresponding to the population densities of 30,000 and 40,000 plants ha -1 , and the 'AG-1051' cultivar had the best performance, with an average yield of 13 t ha -1 , largely due to its better genetic load.

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