# Root System and Its Relations with Soil Physical and Chemical Attributes in Orange Culture
## 4 Discussion
The multifunctionality of the device made it possible to carry out several processes that could increase soil compaction, if they were carried out separately. The physiological factors that determine the general productivity of a crop are influenced by soil compaction [38], which is associated with conditions of physical impediments when soils have high resistance to penetration, reduced total porosity and reduced number and size of pores that, consequently, impact root volume [39]. Therefore, the physical attributes are important for root development of the culture, although they did not enter the decision tree as main components. The macroporosity and bulk density of the soil are closely related attributes that influence the physical quality of the soil and, consequently, the production of the crop. Soil preparations aimed at conservation, with minimal tillage, can promote an increase in macroporosity due to less soil disturbance compared to conventional preparations that promote an increase in soil density due to compaction caused by agricultural machinery and implements [40]. The use of implements for mechanical decompaction of the soil is one of the practices widely used in the agricultural field. According to [38], soils managed with subsoilers present lower resistance to penetration values when compared with no-tillage systems, favoring root volume of the crop and consequently productivity. Considering this, subsoiling is an alternative in which [41] claims that the roots explore higher soil volume due to their higher density and homogeneous distribution in the profile, favoring a more appropriate environment for root volume and development. For the Oxisol area, use of the triple tillage implement provided medium to high root volume, with no observed negative effects, i.e., low root development of the crop. In addition, this soil tillage interacting with copper concentrations higher than 0.7 mg kg\({}^{-1}\) enabled high root volume in superficial layers (at depths less than or equal to 0.75 m), and medium root volume at levels less than or equal to 0.7 mg kg\({}^{-1}\). The micronutrient copper, when at concentrations that do not cause disturbances and toxicity to plants, performs fundamental functions in physiological processes such as protein and carbohydrate synthesis, photosynthesis and cellular respiration process. However, excess may impair the normal development of plants, affecting biochemical reactions and physiological processes in general [42] due to the triggering of morphological changes in the root system such as shortening and decreased density [43]. SubsoilTilage only, at a depth greater than 0.70 m, and soil copper contents greater than 0.7 mg kg\({}^{-1}\) provided high root volume to plants. Deeper soil tillage with sub-soiling may effectively improve the physical attributes altered in the compaction process, mainly soil porosity, due to the force exerted on deep, intermediate and superficial soil particles [44], and may improve the conditions of the environment, favoring root volume, nutrient absorption and, consequently, reflect on crop yield. [PERSON] et al. [45], suggested that deep tillage can improve accessibility to subsoil nutrients, when they are deficient in the supernatural layers, reflected in an increase of culture yield. Assessing the root volume obtained in a sugarcane area under conventional tillage and deep tillage with the use of a subsoiler, [46] found significant differences in the root volume of plants in the subsoiler tillage, obtaining greater density and length of the roots in addition to a more homogeneous root distribution in the soil profile up to 0.6 m in depth, while in conventional cultivation the roots were concentrated in the planting row. SubsoilTilage depends on specific local conditions. In areas where there are restrictive layers for root growth the effects can reach 20% greater than in areas with less compacted layers, as it allows minimization of barriers that prevent vertical growth, facilitating absorption of nutrients underground [45].