ABSTRACT
Abstract in Brazil, management agricultural practices not currently consider the soil spatial variability as a result, crop growth can be non-uniform and yields often is low. This research aims to compare Kriging, Cokriging and Collocated cokriging using soil physical and hydraulic properties and their influences on soybean development. We hypothesized that spatial variability of physical and hydraulic properties has influence on soybean development and this variability can be better represented by Collocated Cokriging method. To test these hypotheses, we accessed the soil physical and hydraulic attributes in a field experiment under no-till system, cultivated with soybean. Geostatistical interpolators were applied to generate maps from which spatial dependence of the variables was evaluated. The experiment was conducted on a sandy clay loam Oxisol, on an experimental station located in Ponta Grossa, Paraná, Brazil. Evaluation of the soil attributes was performed: bulk density (BD), particle size distribution, saturated soil hydraulic conductivity (K fs ), total porosity (TP), macroporosity and microporosity. The plant was plant height and stand. Data analysis were performed by geostatistical methods; the spatial dependence was established using experimental univariate and cross semivariograms with datasets. Modeling semivariograms led to the generation of attribute maps by Kriging, Cokriging and Collocated cokriging. The estimation by Cokriging and Collocated cokriging was similar from Kriging. From the semivariogram, it was possible to identify that soil and plant attributes were spatially related with each other. The soya growth was mainly changed by slope of the area and little changed by saturated hydraulic conductivity.
ABSTRACT
Spatial variability of chemical attributes in soils tends to increase under the no-tillage system. However, data regarding this variability under this system for a long time are scarce. This study aimed to evaluate the spatial variability of phosphorus (P), organic matter (OM), pH, aluminum (Al), calcium (Ca), magnesium (Mg), potassium (K), base saturation (V%), sulfur (SO42-), and micronutrients: boron (B), iron (Fe), copper (Cu), manganese (Mn), and zinc (Zn) in soil with conventional tillage and no-tillage treatments for more than three decades in order to optimize fertilization and maintain soil conservation. Samples of Rhodic Hapludox were collected at 0.000.20 m depth. Sampling points were spaced 5 m apart, totaling 100 points. All sampling points were georeferenced according to the tillage system. Samples were analyzed chemically. Semivariograms and kriging were used in descriptive statistics and geostatistics analyses of the results. Only micronutrients and P presented distinct spatial variability between the treatments. Most of the analyzed chemical attributes presented spatial dependency in both tillage systems, which may help determine the best form of sampling and indicate adequate fertilization. According to semivariogram range values of OM, Mg, and K, the same sampling strategy may be adopted for analysis in both tillage systems, yet for Al, Ca, and pH the strategy should be specific
A variabilidade espacial dos atributos químicos tende a aumentar em solos sob sistema plantio direto. No entanto faltam informações sobre essa variabilidade em solos submetidos a esse sistema por longo período.Este estudo objetivou avaliar a variabilidade espacial do fósforo (P), matéria orgânica (MO), pH, alumínio (Al), cálcio (Ca), magnésio (Mg), potássio (K), saturação por bases (V%), enxofre (SO42-) e dos micronutrientes boro (B), ferro (Fe), cobre (Cu), manganês (Mn) e zinco (Zn) em plantio direto e plantio convencional adotados há mais de três décadas, como forma de otimizar a aplicação de fertilizantes e preservar a adoção do manejo conservacionista. Amostras de Latossolo Vermelho distrófico coletadas na profundidade de 0,00 - 0,20 m, e 5 m de distância entre os 100 pontos amostrados e georreferenciados por manejo, foramanalisadas quimicamente e os resultados submetidos à estatística descritiva e à geoestatística, através do estudo de semivariogramas e krigagem. Apenas os micronutrientes e o P apresentaram variabilidade espacial distinta entre os manejos. A maioria dos atributos químicos estudados apresentou dependência espacial em ambos os sistemas de manejo, o que pode determinar a melhor forma de amostragem e indicar a adubação adequada. De acordo com os alcances atribuídos aos semivariogramas, para MO, Mg e K pode-se adotar a mesma estratégia de amostragem para análise em ambos sistemas de manejo e para Al, Ca e pH deve ser específica