Soil microbial biomass nitrogen and β-glucosaminidase activity response to surface compaction and poultry-litter application in a claypan soil

In agroecosystems, compaction-induced changes in soil physical properties may significantly affect soil microbial activity, especially N-related processes. The objective of this study was to determine the effect of soil compaction on soil microbiological properties related to N in a claypan soil amended with poultry litter (i.e., Turkey (Meleagris gallopavo) excrement mixed with pine shavings as bedding) and cropped to corn (Zea mays L.). In a laboratory incubation, a silt loam soil was compacted to four bulk density levels (1.2, 1.4, 1.6 and 1.8 mg m−3) amended with and without poultry litter and incubated at 25 °C for 28 d. In a field experiment conducted in 2001 and 2002, a Mexico silt loam claypan soil was amended with litter (0 and 19 mg ha−1), left uncompacted or uniformly compacted and planted to corn or left fallow. In the incubation study, soil compaction reduced microbial biomass N (MBN) and soluble N (Sol N), but increased microbial C:N ratio and soil β-glucosaminidase activity. Added litter increased Sol N and soil β-glucosaminidase activity in the laboratory. Under controlled soil water content and temperature, all soil microbiological properties had a linear relationship with soil bulk density (r2 = 0.63**–0.90***). In the field, the compaction effect on all the measured soil microbial properties was less pronounced. The field observation also showed that litter-amended soil had higher MBN, Sol N and soil β-glucosaminidase activity compared to unamended soil in both compaction treatments, regardless of fallow and cropped plots. Under field conditions, MBN and microbial C:N ratio significantly correlated with soil water content (r = 0.49*** and −0.32***, respectively), while soil β-glucosaminidase activity was correlated with total soil organic C (r = 0.39***). The results showed that N-related soil microbiological properties were sensitive to changes induced by soil compaction, while beneficial effects of litter addition may mitigate some compaction effects on these soil properties.

► Soil compaction reduced soil microbial activities related to nitrogen (N).
► Litter addition could overcome these compaction effects on N processes.
► N-related soil microbiological properties were sensitive to changes induced by soil compaction.
► But beneficial effects of litter addition may mitigate some compaction effects on these soil properties.