Irrigated agriculture and tillage practices impact microbial community structure

La Agricultura de irrigación y las Practicas de Labranza Impactan la Estructura de la Comunidad Microbiana

Mills, DeEtta and Entry, James A. and Mathee, Kalai and Narasimhan, Giri and Jayachandran, Kris and Sojka, R.E. and Busscher, Warren J. (2003) Irrigated agriculture and tillage practices impact microbial community structure. pp. 749-754. In: Proceedings 16th Triennial Conf. of ISTRO: Soil Management for Sustainability. Australia-Brisbane, 2003/07/13-18.

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Abstract

Irrigation increases carbon (C) input to soils via increased litter and root production.
Intensively managed crop or pastureland has potential for C gain through the use of improved grazing
regimes, fertilisation practices and irrigation management. Soil microbial diversity is important
because it is often regarded as an index of soil health. Loss of biodiversity leads to loss of ecosystem
resistance and resilience to anthropogenic as well as natural stresses. Organic C and microbial
structural diversity present in Southern Idaho soils having long term cropping histories was measured.
The sites sampled were native sagebrush vegetation (NSB); irrigated mouldboard ploughed crops
(IMP), irrigated conservation-chisel-tilled crops (ICT) and irrigated pasture systems (IP). Organic C
concentration in soils decreased in the order NSB 0-5 cm>1P 0-30 cm = ICT 0-15 cm>IMP 0-30
cm>NSB 5-15 cm = NSB 15-30 cm. Amplicon length heterogeneity (ALH) LH-PCR, a DNA profiling
method, was used to profile the eubacterial structural diversity in all soils sampled at the different
depths. LH-PCR interrogates the variable domains of the ribosomal small subunit genes (SSU rRNA),
and separates these variable domains on high-resolution genetic analysers. ALH assays are based on
the natural variation in sequence lengths of the 16S rRNA genes and are independent of restriction
enzyme recognition sites. The application of the ALH technique as a monitoring tool for microbial
ecology has been shown to enhance and extend the current understanding of the structural dynamics of
microbial communities in their specific environments.
Using the profiling data from four hypervariable regions of the 16S rRNA (VI, VI +V2, V3 and V9), it
was shown that native sagebrush soil communities differed in bacterial richness (i.e. different
phylotypes) within the top 30 cm when compared to the irrigated agricultural soils. Between the
agricultural management systems (in the top 30 cm) the bacterial richness of conservation-tilled soils
was greater than irrigated mouldboard ploughed soils but less than irrigated pastures. Soil C
concentrations also correlated with eubacterial diversity indices for the four variable regions (r2 = 0.91,
0.92, 0.68, 0.70, respectively), evenness indices (r2 = 0.72, 0.68, 0.93, 0.80, respectively) and the
active bacterial biomass (r 2 = 0.75, 0.75, 0.79, 0.79 respectively). Since 1CT and IP increase C
sequestration and appear to support higher eubacterial diversity in soils compared to IMP, producers
can use these management practices on their lands to sequester organic C, improve soil microbial
diversity and enhance soil biological processes.

Item Type:	Conference or Workshop Item (Paper)
NWISRL Publication Number:	1122
Subjects:	Soil > Tillage Mass Import - autoclassified (may be erroneous)
Depositing User:	Dan Stieneke
Date Deposited:	20 Nov 2010 21:56
Last Modified:	07 Nov 2016 16:47
Item ID:	941
URI:	https://eprints.nwisrl.ars.usda.gov/id/eprint/941