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 degrees 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 beta-glucosaminidase activity. Added litter increased Sol N and soil beta-glucosaminidase activity in the laboratory. Under controlled soil water content and temperature, all soil microbiological properties had a linear relationship with soil bulk density (r(2) = 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 beta-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 beta-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. (C) 2011 Elsevier B.V. All rights reserved.