# Root System and Its Relations with Soil Physical and Chemical Attributes in Orange Culture
## 2 Materials and Methods
### Soil Sampling and Physical-Chemical Analysis  
For soil and root sample collection, in each treatment three trenches were opened distanced every 0.5 m from the planting row, with dimensions of 2.0 m width, 2.0 m length and 3.5 m depth. Soil sampling was done at depths of 0.00-0.10, 0.10-0.20, 0.20-0.30, 0.30-0.40, 0.40-0.50, 0.50-0.75 and 0.75-1.00 m in two positions: (1) planting row (PR) and (2) plant canopy projection (CP) (Figure 2). Tree depth samples were collected and the trenches were arranged in places chosen by lot.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Minimum Tillage** & **Subsoiler Tillage** & **Triple Tillage** \\ \hline Agricultural implements & Harrow & Harrow & Harrow \\ \cline{2-4}  & Chiselling & Chiselling & Chiselling \\ \cline{2-4}  & - & Subsoiler & Subsoiler \\ \cline{2-4}  & - & - & Triple operation \\ \hline \hline \end{tabular}
\end{table}
Table 1: Sequence of agricultural operations used in each soil tillage: minimum tillage, subsoiler tillage and using the triple tillage implement.  
Figure 1: Agricultural implement developed by the Fisher Citrosuco group that performs triple tillage in citrus crops. Source: [PERSON].  
The total porosity of the soil is the fraction of volume that can be occupied by water and/or air of a determined total volume of soil. The direct porosity measure is based on the saturation of the soil with water that must occupy the entire volume of pores, assuming a density of water equal to 1000 kg. m\({}^{-3}\), and the water mass due to the difference between saturated soil and soil dried in an oven, by weighing on an analytical balance [16]. Macropores are pores that empty when a suction of 0.60 m is applied, emptying all pores with a diameter greater than 0.05 mm, and the microporosity is then defined as the volume that water occupies in the sample with a diameter between 0.05 and 0.0002 mm. The method used was the so-called tension table in which the determination of the mass of water retained in a soil sample, of known volume, is made after the time of equilibrium in the tension table, by weighing, obtaining the microporosity and macroporosity due to the difference between total porosity and microporosity [17].  
Soil mean weight-diameter was determined by the wet sieving method [18] and soil resistance to penetration was determined by the methodology proposed by [19].  
Chemical attributes that were calculated after determining pH were cation exchange capacity (CEC), saturation (SB) and the sum of bases (V%). Following the methodology proposed by [20] exchangeable cations (Ca\({}^{2+}\), Mg\({}^{2+}\) and K\({}^{+}\)), and potential acidity (H\({}^{+}\) + Al\({}^{3+}\)) and available phosphorus (P) were calculated. Calcium and magnesium were determined by atomic absorption spectrophotometer, and potassium by flame photometry.  
The micronutrients copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn) were extracted with diethylenetriaminepentaacetic acid (DTPA) solution at pH 7.3 as described by [21]. To determine soil organic carbon content, we used the Walkley-Black method described by [16].