How different organic amendments influence microbial activity in soils

Researchers from Punjab Agricultural University in India looked at the effects of adding organic amendments in farmland soil, in particular, its impact on the soil’s microbial activity. Their findings were published in the journal Archives of Agronomy and Soil Science.

• For the study, the team collected soil samples from long-term experimental field plots. The selected plots had three levels of saline water irrigation: normal water and saline water with an electrical conductivity of 6 and 12 deciSiemens per meter (dS/m), respectively.
• The samples were then incubated with either finely ground biochar, rice straw, farmyard manure, or glucose for eight weeks at 25 C. The amendments were added at two rates – 1 and 2.5 percent carbon basis, respectively.
• The researchers then assessed the samples in terms of cumulative respiration, microbial biomass carbon, and nutrient availability (nitrogen and phosphorus). They found that these had a negative relationship with electrical conductivity. This relationship applied to all samples and amendments.
• The decrease in cumulative respiration was lowest with glucose amendment, followed by rice straw, farmyard manure, and biochar.
• Dissolved organic carbon, on the other hand, had a positive correlation with salinity, with increased carbon addition leading to higher concentrations.
• Lower nitrogen release from amendments under saline conditions limited microbial utilization of available carbon.

In sum, microbial activity in saline soils is highly dependent on organic amendments.

Journal Reference:

Chahal SS, Choudhary OP, Mavi MS. ORGANIC AMENDMENTS DECOMPOSABILITY INFLUENCES MICROBIAL ACTIVITY IN SALINE SOILS. Archives of Agronomy and Soil Science. 30 March 2017;63(13):1875–1888. DOI: 10.1080/03650340.2017.1308491