Effect of tillage systems and permanent groundcover intercropped with orange trees on soil enzyme activities

The objective of this study was to evaluate the effect of different soil tillage systems and groundcover crops intercropped with orange trees on soil enzyme activities. The experiment was performed in an Ultisol soil in northwestern Paraná State. Two soil tillage systems were evaluated [conventional tillage (CT) across the entire area and strip tillage (ST) with a 2-m strip width] in combination with various groundcover vegetation management systems. Soil samples were collected after five years of experimental management at a depth of 0-15 cm under the tree canopy and in the inter-row space in the following treatments: (1) CT-Calopogonium mucunoides; (2) CT-Arachis pintoi; (3) CT-Bahiagrass; (4) CT-Brachiaria humidicola; and (5) ST-B. humidicola. The soil tillage systems and groundcover crops influenced the soil enzyme activities both under the tree canopy and in the inter-row space. The cultivation of B. humidicola provided higher amylase, arylsulfatase, acid phosphatase and alkaline phosphatase than other groundcover species. Strip tillage increased enzyme activities compared to the conventional tillage system.

Effect of stand types on understory vegetation.

The objective of this study was to compare density, vegetative cover, basal area, height growth, aboveground biomass production, frequency, floristic composition, and species diversity of understory vegetation growing in Hungarian oak (Quercus frainetto Ten.), Oriental beech (Fagus orientalis L.) and a mixed stand of both species (90% Hungarian oak and 10% Oriental beech) with the same crown closure. Understory vegetation was sampled with a quadrat of 0.5 m x 1 m along the 25 m-long transect lines in each stand. A total of seventeen perennial plant species from thirteen different families were found in the three stand types and all of them were present in Hungarian oak stand, eleven in Oriental beech stand, and seven in the mixed stand of Hungarian oak and Oriental beech trees. Results showed that stand types had a statistically significant effect on density, vegetative cover, basal area, height growth, biomass production, frequency, floristic composition, and species diversity of understory vegetation. Total understory vegetation density was the highest for Hungarian oak stand with about 136 plants m-2 and the lowest for the mixed stand of Hungarian oak and Oriental beech with 44 plants m-2. In addition, the Hungarian oak stand had the most diverse understory vegetation with about 4.3 different plant m-2, followed by the Oriental beech stand with 3.7 plants m-2, and the mixed stand of the Hungarian oak and Oriental beech with 2.7 plants m-2. Species density and diversity were the highest in Hungarian oak stand whereas aboveground biomass production and height growth of understory vegetation were highest in the mixed stand.