Inadequate management of soil and water can cause changes in soil physical characteristics, resulting in lower root development. Thus the objective of the present study was to evaluate the dry matter production of corn roots under combinations of levels of bulk density and water tension in the soil. The experiment was conducted in a greenhouse in a randomized block design, based on a modified central composite design of a 52 fractional factorial scheme, of combinations of bulk densities (1.0, 1.2, 1.4, 1.6 and 1.8 Mg m-3) and water tensions in the soil (10, 20, 30 40 and 50 kPa), resulting in 13 treatments with four replicates. An Oxisol collected in the layer of 0-0.2 m was used. The pots were made of PVC (polyvinyl chloride) tube with compacted soil in the middle layer. The tensiometers were installed at a depth of 0.15 m, remaining in the central region of the compacted layer. The experiment was collected 104 days after sowing. Root dry matter production of corn was limited by increased water stress and bulk density.

Open Agriculture. 2017; 2: 317-328 in BD observed after tillage in the 0-0.05 m soil depth increased after operations in all treatments. The increase was higher in the tractor sub-plot (15%) than in those where animal traction was used (8%). Before operation Ks class was rapid and fast in all samples, and after operation this value was reduced to 33% in T, whereas it reached 83% in C. Electrical Resistivity Tomography (ERT) was useful as a tool to identify the alterations caused by tillage operations on soil physical status. These preliminary results confirm the potential of animal traction as an option for mountain agri-environments, yet it requires much wider research to soundly ground its assets.Keywords: Animal traction, Soil compaction, Saturated hydraulic conductivity, Electrical Resistivity Tomography IntroductionSoil structure degradation, often called soil compaction, is regarded as one of the most serious form of land degradation caused by conventional farming practices which negatively disturbs the soil physical status. According to the European Environmental Agency (2012) compaction is one of the key threats affecting soils. It occurs even in no-tillage systems because of the compressive forces applied to soil by tractor wheels (Batey 2009). Compaction alters soil structure by crushing aggregates or combining them into larger units, increase soil bulk density, and decrease the number of coarse pores (Needham et al. 2004;Delgado et al. 2007). The problem is magnified because, being mainly a subsurface phenomenon, soil compaction is commonly considered as the type of land degradation most difficult to locate and rationalise. Unlike erosion and salinity that give strong surface evidence of their presence, soil DOI 10.1515DOI 10. /opag-2017 Received January 31, 2017; accepted April 12, 2017 Abstract: Soil Compaction results from compressive forces applied to compressible soil by machinery wheels, combined with tillage operations. Draft animal-pulled equipment may also cause soil compaction, but a huge gap exists on experimental data to adequately assess their impacts and, actually, animal traction is an option seen with increasing potential to contribute to sustainable agriculture, especially in mountain areas. This study was conducted to assess the impacts on soil compaction of tillage operations with motor tractor and draft animals. In a farm plot (Vale de Frades, NE Portugal) treatments were applied in sub-plots (30 m x 3 m), consisting in a two way tillage with tractor (T), a pair of cows (C) and a pair of donkeys (D). Undisturbed soil samples (120) were taken before and after operations for bulk density (BD) and saturated hydraulic conductivity (Ks). The relative changes

An experiment was carried out in Remígio county, Paraiba State, Brazil from July/2013 to May/2014, in order to evaluate effects of saline water irrigation, bovine biofertilizer and potassium types on soil salinity, leaf composition in macronutrients and on production of yellow passion fruit plants cv BRS Gigante Amarelo. Treatments were distributed in randomized blocks arranged in factorial design 2 × 2 × 2, referring to electric conductivity water of 0.35 and 4.00 dS m-1 , in soil without and with bovine biofertilizer applied via water (volume of 6 L plant-1 of mixture) one day before and every 90 days after transplanting and conventional potassium chloride (KCl) and coated with organic polymers supplied monthly. The soil salinity in beginning of plants flowering, was increased of initial value of 0.36 dS m-1 to respectively 3.43 and 5.43 dS m-1 between plants irrigated with non-saline and saline water. Fertilization with coated KCl reduced the potassium contents compared to conventional KCl. Except in nitrogen and potassium plants were deficient in other macronutrients but produced in promising level since the productivity was superior the Brazilian average, Brazilian Northeast and average of the Paraíba State Brazil.

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