Browse on keywords: organic matter microbial biomass
Search results on 05/23/13
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.
2249. Granatstein, D., D. Bezdicek, L. Elliott, V. Cochran, and J. Hammel. 1987. Long-term tillage and rotation effects on soil microbial biomass, carbon, and nitrogen.. Biol. Fertil. Soils 5:265-270..
This research examined plots that had been under different tillage and rotational management for 12 years. Rotations were WP (winter wheat-spring pea); WBP (winter wheat-spring barley-spring pea); WPA (winter wheat-spring pea undersown with red clover and alfalfa)-clover/alfalfa GM). The two tillages studied were moldboard plowing and no-till. There was little difference in microbial biomass, C or N below 5 cm in the no-till, with surface values being highest. Few differences due to rotation could be detected. The WPA rotation had the highest total C and N. Microbial biomass was higher in no-till surface soils where the preceding crop had provided high residue, while the opposite was true for tilled plots. Microbial biomass levels changed little from April to September, and then jumped higher in October with the advent of moisture.
3661. Knapp, E.B., L.F. Elliott, and G.S. Campbell. 1983. Microbial respiration and growth during the decomposition of wheat straw.. Soil Biol. Biochem. 15:319-323.
The response of the microflora to glucose additions indicated that the microbial populations were primarily limited by available C rather than available N after only 240 hr of incubation, even though about 95% of the original straw residue-C plus biomass C remained in the system.
3670. Knapp, E.B., L.F. Elliott, and G.S. Campbell. 1983. Carbon, nitrogen, and microbial biomass interrelationships during the decompostion of wheat straw: a mechanistic simulation model.. Soil Biol. Biochem. 15:455-461.
The effect of N on the disappearance of C from a wheat straw system, and the response of the biomass to N additions, was simulated using microbial growth and maintenance terms from the literature. Straw decomposition rate was shown to be strongly dependent on available C and N during initial decomposition. When N is limiting, excess available C apparently is immobilized as polysaccharides.
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.