Influence of organic and mineral amendments on microbial soil properties and processes

Abstract

Microbial diversity in soils is considered important for maintaining sustainability of agricultural production systems. However, the links between microbial diversity and ecosystem processes are not well understood. This study was designed to gain better understanding of the effect of short-term management practices on the microbial community and how changes in the microbial community affect key soil processes. The effects of different forms of nitrogen (N) on soil biology and N dynamics was determined in two soils with organic and conventional management histories that varied in soil microbial properties but had the same fertility. The soils were amended with equal amounts of N (100 kg ha -1 ) in organic (lupin (Lupinus angustifolius L.)) and mineral form (urea), respectively. Over a 91-day period, microbial biomass C and N, dehydrogenase enzyme activity, community structure of actinomycetes and α proteobacteria (by denaturing gradient gel electrophoresis (DGGE) following PCR amplification of 16S rDNA fragments) and N mineralisation were measured. Lupin amendment resulted in a 2 to 5-fold increase in microbial biomass and enzyme activity, while these parameters did not differ significantly between the urea and control treatments. The PCR-DGGE analysis showed that the addition of mineral and organic compounds had an influence on the microbial community composition in the short-term (up to 10 days) but the effects were not sustained over the 91-day incubation period. Microbial community structure was strongly influenced by the presence or lack of substrate, while the type of amendment (organic or mineral) had an effect on microbial biomass size and activity. These findings show that the addition of green manures improved soil biology by increasing microbial biomass and activity irrespective of management history, that no direct relationship existed among microbial structure, enzyme activity and N mineralisation, and that microbial community structure (by PCR-DGGE) was more strongly influenced by inherent soil and environmental factors than by short-term management practices.

Agricultural Management and Labile Carbon Additions Affect Soil Microbial Community Structure and Interact with Carbon and Nitrogen Cycling

“…Increased N mineralization increases the amount of N available to plants [26,27]. This coupled cycling is particularly important in minimizing potential leaching losses of inorganic N, since unlike synthetic fertilizer application, this process leads to N being mineralized in response to plant demand and hence more likely to be assimilated by plants and less likely to be lost via leaching and other N loss pathways [12,26,28].…”

“…Organic management practices using diverse rotations and additions of organic residues affect microbial community structure over the long term through buildup of soil organic matter (SOM) and changes in SOM chemistry [6,7,[12][13][14]. In addition, greater crop diversity alters plant litter inputs and can presumably increase the number of ecological niches available for soil microbes [7,11].…”

Factores que intervienen en el proceso de mineralización de nitrógeno cuando son aplicadas enmiendas orgánicas al suelo. Una revisión

“…En el trabajo realizado por Stark et al (2007) se concluyó que la actividad enzimática, actividad microbiana y taza de mineralización de N es más fuertemente influenciada por factores inherentes al suelo y al ambiente, que por prácticas de manejo. Como complemento, He y Zhang (2014) indican que el C orgánico en sistemas de labranza de conservación puede estar en formas menos lábiles, lo que genera una disminución en las tasas de mineralización de N. Los microorganismos requieren C como fuente de energía y N para sintetizar sus tejidos, la relación entre estos dos elementos debe permanecer dentro de cierto rango (del que se hablará más adelante) para que el proceso de mineralización se realice sin que haya inmovilización de N (consumo total de N por parte de los microorganismos) o pérdidas de N por volatilización o lixiviación.…”

Beneficial Role of Biofertilization on Yield Related Characteristics of Two Apple Cultivars and Soil Microorganisms Under Orchard Conditions

“…Stimulating effect of the applied biofertilizers are not only an indicator of a pronounced nitrogen-fixing capacity of introduced bacterial strains, but is also the indicative of a number of phenomena, i.e., intensification of photosynthesis process, inhibition of phytopathogens or synthesis of phytohormones (Sukhovitskaja et al, 2004), and other plant growth stimulators, targeted detoxification of heavy metals and high salt concentrations, and exocellular polysaccharide synthesis (Park et al, 2005;Biari et On the other hand, the highest number of fungi in the rhizosphere of the examined apple cultivars was obtained under chemical fertilizer treatment (27.00) whereas the lowest count determined in treatment with PGPR2 fertilizer (27.00). This phenomenon is most likely a consequence of changes in physical and chemical properties of soil, as well as changes in the structure of soil microbial cenosis (Stark et al, 2007). The authors point out that in such circumstances, an increase in population of toxinogenic and pathogenic fungi may cause a decline in numbers, especially Gram-negative bacteria and other poorly competitive species of soil microorganisms.…”