Identification of spatial variability of soil physico-chemical properties for precision farming
Site-specific crop management practices, known as precision farming, requires information about detailed spatial distribution of soil physico-chemical properties related to the yield productivity. Traditional mapping of soil properties in form of soil sampling is inefficient for assessment of high level of spatial variability due to the high costs. For this reason, a study was conducted within the research projects NAZV QJ1610289 and TACR TH02030133 to evaluate the digital soil mapping techniques, including proximal sensing methods in the form of on-the-go measurement of soil electrical conductivity, for mapping of agronomical relevant soil properties.The experimental work was carried out on the selected fields of Rostenice a.s. farm enterprise, located in the South Moravia region of Czech Republic. Total area of 476 ha within eight fields was measured from 2013 to 2016 by using CMD-1 instrument (GF Instruments, Czech Republic) mounted on the plastic sledges. This device measures the electrical conductivity by the principle of electromagnetic induction (EMI) with 0.98 m dipole center distance and effective depth of measurement of 1.5 m (vertical mode) or 0.75 m (horizontal). Soil properties were obtained by soil sampling in irregular grid with the density of 1 sample per 3 ha. Soil samples were taken from the depth of 30 cm and analyzed for soil texture (percentage of clay, silt and sand particles), content of available nutrients (P, K, Mg, Ca), cation exchange capacity (CEC), soil organic matter content (SOM) and wilting point (WP). The results showed different level of spatial variability among the observed fields. The correlation analysis proved differences in main sensitivity of EMI to the soil properties, mainly the percentage of clay particles smaller than 0.002 mm (r = 0.598). The correlation between EMI and nutrients content in soil and pH value was significant only for few fields. These outcomes showed, that rather than predictor of soil properties could be on-the-go measurement of soil EC used for identification of main zones within the fields at high spatial level.