The effect of crop sequences on soil microbial, chemical and physical indicators and its relationship with soybean sudden death syndrome (complex of Fusarium species)

Carolina Perez-Brandan,Jose Manuel Meriles,Jorgelina Huidobro,Gary D Bending,Sally Hilton,Cinthia Conforto,Jose Luis Arzeno,Silvina Vargas-Gil,Betiana Grumberg

doi:10.5424/sjar/2014121-4654

Abstract

The effect of crop sequences on soil quality indicators and its relationship with sudden death syndrome (SDS, a complex of Fusarium species) was evaluated by physical, chemical, biochemical and molecular techniques. Regarding physical aspects, soybean/maize and maize monoculture exhibited the highest stable aggregate level, with values 41% and 43% higher than in soybean monoculture, respectively, and 133% higher than in bean monoculture. Bulk density (BD) was higher in soybean monoculture, being 4% higher than in bean monoculture. The chemical parameters organic matter, total N, P, K, Mg, Ca, and water holding capacity also indicated that soybean/maize and maize monoculture improved soil quality. Fungal and bacterial community fingerprints generated using Terminal Restriction Fragment Length Polymorphism analysis of intergenic transcribed spacer regions of rRNA genes and 16S rRNA genes, respectively, indicated a clear separation between the rotations. Fatty acid profiles evaluated by FAME showed that bean monoculture had higher biomass of Gram (+) bacteria and stress indicators than maize monoculture, while the soybean/maize system showed a significant increase in total microbial biomass (total FAMEs content) in comparison with soybean and bean monoculture. The incidence of SDS (Fusarium crassistipitatum) was markedly higher (15%) under soybean monoculture than when soybean was grown in rotation with maize. In the present work, soil microbial properties were improved under soybean/maize relative to continuous soybean. The improvement of soil health was one of the main causes for the reduction of disease pressure and crop yield improvement due to the benefits that crop rotation produces for soil quality.

Highlights

In an attempt to increase yields and competitiveness, conservation management practices are being disregarded, the predominant practices being crop monoculture, intensive tillage, and excessive use of pesticides (Sainju et al, 2011)
Bulk density (BD) was significantly higher in soybean monoculture, with 4% higher values than in bean monoculture
The lowest BD values were recorded in the soybean/maize and maize monoculture, without statistical difference between those treatments

Summary

Introduction

In an attempt to increase yields and competitiveness, conservation management practices are being disregarded, the predominant practices being crop monoculture, intensive tillage, and excessive use of pesticides (Sainju et al, 2011). Part of the instability of monocultural agroecosystems can be associated with a soil structure weakened by increased susceptibility to compaction, reduced water infiltration, and increased erosion (Arshad et al, 2011). These characteristics make monoculture systems less resilient to stress (Zuo & Zhang, 2009). To identify the effects of different monoculture crops on soil properties and crop health, the magnitude of stress, the degree of exposure to stresses or the ecological response to exposure can be quantified using ecological indicators because they provide an efficient means to characterize composition, structure, and function of complex ecological systems (Karr, 1991). A challenge in selecting ecological indicators is determining those measures that appropriately characterize the system and yet are simple enough to be effectively and efficiently monitored (Dale et al, 2008)

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Results

Conclusion