Effect of Cultivation and Soil Tillage Systems on the Microbial Biomass in Castor Bean Crop at the Irecê Plateau, Bahia

Camila Brasil Dias,Luciano Da Silva Souza,Carlos Alberto Da Silva Ledo,Eduardo Gross,Francisco Alisson Da Silva Xavier,Arlicélio De Queiroz Paiva

doi:10.5539/jas.v11n4p341

Camila Brasil Dias, Luciano Da Silva Souza + Show 4 more

Open Access

https://doi.org/10.5539/jas.v11n4p341

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Abstract

Inadequate soil management alters the microbiological attributes of the soil, causing reduction in microbial biomass and activity. Microbial biomass is the living and active part of the soil and can serve as an indicator of changes in the quantity of due to changes in land use. This study aimed to evaluate the effect of intercropping and soil tillage systems on the microbial biomass in castor bean-based crop in the Irec&ecirc; Plateau, Bahia, Brazil. The experiment was carried out on an eutrophic Haplic Cambisol with clay texture in the Mata Verde Farm of Alto do Quindinho, municipality of S&atilde;o Gabriel, Irec&ecirc; Plateau, Bahia, Brazil. Six intercropping systems were evaluated including solely castor bean (control) and castor bean intercropped with each of the castor bean cake, common bean, pigeon pea, corn, and gliricidia. Plowing + harrowing and subsoiling were the two soil tillage techniques associated to the intercropping systems. C and N contents in microbial biomass (Cmic and Nmic), soil basal respiration and metabolic quotient were determined in soil samples collected from the 0-10 and 10-30 cm layers. The different soil management systems influenced microbial biomass and activity, and the most suitable conditions for soil microbiota occurred in the soil tillage system with subsoiling. In the semi - arid condition, at 0-10 cm depth, the castor bean + castor bean cake crop system promoted an increase of Cmic content, and the castor + gliricidia system increased Nmic content, both under soil tillage with subsoiling.

Highlights

The region of Irecê is located in Northwestern Bahia, Brazil, and is considered as one of the country largest producer of castor bean
The interaction between soil tillage and intercropping systems was significant for microbial biomass C (MB-C) contents (Table 3)
Soil tillage with subsoiling led to increase in MB-C in comparison to the tillage with plowing and harrowing. This response can be attributed to the greater turning of the soil by the plow and harrow, which accelerates the process of oxidation of soil organic matter causing stress on the microbial biomass

Summary

Introduction

The region of Irecê is located in Northwestern Bahia, Brazil, and is considered as one of the country largest producer of castor bean. In Brazil, the Bahia state is the largest castor bean producer, with about 51,487 ha cultivated and a production of 33,541 tons in 2014, which corresponded to 89% of the national production and 95% of the production in the Northeast region (IBGE, 2016). One of most important and negative impacts of mechanization in agricultural systems is the increase of soil compaction due to machinery traffic (Roboredo et al, 2010). Mechanical soil tillage directly influences the physical and biological properties of the soil. Microbial biomass is considered as a good indicator to express the level of soil quality (Islam & Weil, 2000). Analysis of C and N contents in the microbial biomass in combination to soil basal respiration measurements are normally used for this purpose

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