Structuring potential of some cover crops and crambe in Haplortox under no-tillage system

An experiment was conducted at the Agronomic Institute of Parana – IAPAR, at the Experimental Station of the municipality of Santa Tereza do Oeste – PR, in Hapludox of clayey soil. Studies with the use of plants cover crops with vigorous root system in different systems of soil management systems are needed, in order to have a diversity of species capable of producing different amounts of crop residues which by decomposing, can alter the physical attributes and consequently, the productivity of the successor culture. The objective of this study was to evaluate the effect of crambe crop and plant cover crops in succession on the physical characteristics of a Haplortox under no-tillage system. The experimental area has been cultivated under no-tillage system for 18 years. The experimental area consisted of 15 plots, each plot with 20x25 m. In 12 plots, plant cover crops were planted, six species of summer and six of winter and the last three consisted of plots with no-tillage system with gypsum application, no-tillage system with scarification and traditional no-tillage (control) in a completely randomized design. The physical attributes of this soil were soil density (DS), total porosity (PT), microporosity (Micro), macroporosity (Macro) and saturated hydraulic conductivity (Ksat) of the soil in the periods of 2014 (initial characterization of the soil) and 2015 (after crambe culture). The microporosity (0.0-0.1 m layer) and Ksat (all soil layers) presented significant differences between treatments in the period of 2015. Microporosity was lower in the pigeon pea coverage (PP) (36.08%), while the largest occurred in the coverage of crambe C5 (45.38%). The Ksat was higher in the dwarf pigeon pea (DPP) (298.20 mm h-1) and sunn hemp (SH) (163.39 mm h-1) coverage in the 0.0-0.1 m layer. The highest Ksat was observed for crambe C9 (96.81 mm h-1), C8 (74.13 mm h-1), velvet bean (70.95 mm h-1) and C5 (53.94 mm h-1) respectively, in the soil layer of 0.1-0.2 m.   Key words: Soil management, soil structure, residues.