Browse on keywords: soil quality microbial biomass
Search results on 12/09/13
906. Blake, J.. 1989. Reading the soil.. Seattle Times p. F1, 7/24/89.
Describes in popular style the highlights of the long-term plots at Pendleton, OR. The importance of organic matter is stressed.
8668. Carter, M.R. and D.A. Rennie. 1982. Changes in soil quality under zero tillage farming systems: distribution of microbial biomass and mineralizable C and N potentials.. Can. J. Soil Sci. 2:587-597.
10436. Haines, P.J. and N.C. Uren. 1990. Effects of conservation tillage farming on soil microbial biomass, organic matter and earthworm populations, in northeastern Victoria.. Austral. J. Expt. Agric. 30:365-371.
Wheat was grown continuously for 7 years with conventional tillage and direct drilling (no-till). There was a significant gradient of organic matter under no-till. In the surface 2.5 cm, biomass C and N, and N mineralization were 35, 30, and 62% greater, respectively, than under conventional tillage. No-till did not significantly increase soil organic C or N. Of the estimated 7.8 t/ha of C added to the soil from crop residues, 4% was retained in the top 7.5 cm at the time of sampling. Microbial biomass varied considerably with season. The biomass of earthworms in the top 10 cm under no-till was more than twice that of conventional tillage, while total worm numbers increased significantly when wheat residue was retained versus burned.
10556. Follett, R.F. and D.S. Schimel. 1989. Effect of tillage practices on microbial biomass dynamics.. Soil Sci. Soc. Amer. J. 53:1091-1096.
Changes in microbial biomass dynamics and N cycling were studied in soils formed under grassland vegetation in western Nebraska, and farmed under wheat-fallow since 1970. Three tillage treatments were compared: no-till, stubble mulch, and moldboard plow. After 16 yr of cultivation, total N in the top 10 cm of soil had decreased to 73, 68, and 50% of native sod for the three tillages, respectively. Soil microbial biomass levels were decreased to 57, 52, and 36% for the respective tillages, compared to grass. CO2 respiration was proportional to microbial biomass, but N mineralization was not. It appeared that C availability for microbial growth declined with increased tillage intensity, which also decreased the soil's ability to immobilize and conserve mineral N.