Soil microbial biomass under different management and tillage systems of permanent intercropped cover species in an orange orchard

Elcio Liborio Balota,Pedro Antonio Martins Auler

doi:10.1590/s0100-06832011000600004

Abstract

To mitigate soil erosion and enhance soil fertility in orange plantations, the permanent protection of the inter-rows by cover species has been suggested. The objective of this study was to evaluate alterations in the microbial biomass, due to different soil tillage systems and intercropped cover species between rows of orange trees. The soil of the experimental area previously used as pasture (Brachiaria humidicola) was an Ultisol (Typic Paleudult) originating from Caiuá sandstone in the northwestern part of the State of Paraná, Brazil. Two soil tillage systems were evaluated: conventional tillage (CT) in the entire area and strip tillage (ST) (strip width 2 m), in combination with different ground cover management systems. The citrus cultivar 'Pera' orange (Citrus sinensis) grafted onto 'Rangpur' lime rootstock was used. Soil samples were collected after five years of treatment from a depth of 0-15 cm, under the tree canopy and in the inter-row, in the following treatments: (1) CT and an annual cover crop with the leguminous species Calopogonium mucunoides; (2) CT and a perennial cover crop with the leguminous peanut Arachis pintoi; (3) CT and an evergreen cover crop with Bahiagrass Paspalum notatum; (4) CT and a cover crop with spontaneous Brachiaria humidicola grass vegetation; and (5) ST and maintenance of the remaining grass (pasture) of Brachiaria humidicola. Soil tillage and the different cover species influenced the microbial biomass, both under the tree canopy and in the inter-row. The cultivation of brachiaria increased C and N in the microbial biomass, while bahiagrass increased P in the microbial biomass. The soil microbial biomass was enriched in N and P by the presence of ground cover species and according to the soil P content. The grass species increased C, N and P in the soil microbial biomass from the inter-row more than leguminous species.

Highlights

Most part of the soils cultivated with citrus in the Paraná State originated from geological Caiuá sandstone that has a low clay content, low natural fertility and a high water erosion potential
Soil conservation management systems have been studied in orange orchards in view of the soil disturbance caused by the conventional tillage, with the removal or incorporation of plant residues into soil, favoring the occurrence of erosive processes, mainly in the early phase of orchard establishment (Politano & Pissarra, 2005)
The chemical properties of the soils were analyzed after five years of treatment with different groundcover and soil tillage systems (Table 1)

Summary

Introduction

Most part of the soils cultivated with citrus in the Paraná State originated from geological Caiuá sandstone that has a low clay content, low natural fertility and a high water erosion potential Due to these Characteristics, conservation management systems have been suggested for the inter-row in orange plantations, aiming to mitigate soil erosion and enhance soil fertility by a permanent protection with groundcover species (Fidalski et al, 2007; Auler et al, 2008). The decrease of soil disturbance associated with cover species between the trees in perennial crop systems can change the soil habitat by affecting the nutrient status, root depth, residue amount and quality, the aggregation/microbial habitat, and can stimulate soil microbial diversity and activity (Dick, 1992; Balota et al, 2004). Soil disturbance can cause significant modifications in the soil habitat, affecting the microbial community

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Results