Microbial and biochemical changes induced by rotation and tillage in a soil under barley production

Abstract

and three tillage treatments (moldboard plowing (MP), chisel plowing (CP) and no-tillage (NT)) were compared in a split-plot design. Total organic C was affected by the tillage treatments but not by the rotations. In the topsoil layer (0-7.5 cm), NT and CP treatments had C,contents 20% higher than the MP treatment. In the same soil layer, MBC averaged 300 mg C kg-' in the MP treatrnent and up to 600 mg C kg-l in the NT soil. Hot-water-extractable and acid-hydrolyzable carbohydrates were on average 4O% greater under reduced tillage than under MP. Both carbohydrate fractions were also slightly larger in the rotation than in the soil under continuous barley. The ratios of MBC and carbohydrate C to total organic C suggested that there was a significant enrichment of the OM in labile forms as tillage intensitywas reduced. Alkaline phosphatase activity was 507o higher under NT and 20% higher under CP treatments than under MP treatment and, on average, 15% larger in the rotation than in the continuous barley treatment. Overall, the management-induced differences were slightly greater in the top layer (0-7.5 cm) than in the lower layer of the Ap horizon (7.5-15 cm). All the properties measured were highly correlated with one another. They also showed significant temporal variations that were, in most cases, independent of the treaftnents. Four years of conservation tillage and, to a lesser extent, rotation with red clover resulted in greater OM in the top soil layer compared with the more intensive systems. This organic matter was enriched in labile forms.

Influence of tillage and liquid swine manure on productivity of a soybean-barley rotation and some properties of a fine sandy loam in Prince Edward Island

“…Soil structural stability was determined on soil samples obtained from the 0-to 10-and 10-to 20-cm soil depths only using a wet-sieving method (Angers and Mehuys 1993). Duplicate air-dried soil sub-samples (30 g) were placed on a nest of sieves (2.00, 1.00, 0.50, and 0.25 mm).…”

Soil microbial biomass and enzyme activity following liquid hog manure application in a long-term field trial

“…Addition of LHM to soil for several years may reduce its total C content, partly due to microbial oxidation of the native organic matter to support high bacterial growth (de Laval 1975). This oxidation of organic C can particularly be observed when crops do not leave enough residues to ensure the mainte-nance of soil C levels such as is the case of silage corn (Angers and Carter 1996). On the other hand, its high NH 4 + -N content could rapidly stimulate its nitrification under favorable soil aerobic conditions (Morvan et al 1996).…”

“…Monoculture corn is well-known to cause the physical degradation of soil (Tabi et al 1990), which may impair soil biological properties (Angers et al 1993). Soil conservation practices, such as manure addition, crop rotations and reduction of tillage intensity, have a profound influence on the size and activity of the soil microbial biomass (Schnürer et al 1985;Simard et al 1994).…”

Carbohydrates in hot water extracts of soil aggregates as influenced by long-term management

“…In both soils the carbohydrate C content was lowest in the 4.0-8.0 mm fraction. Several longterm studies have shown that rotation with legumes can increase the amount of carbohydrates in soil (6,10,18). Soil carbohydrates were strongly influenced by soil management systems, including amendments with bark compost or leaf litter (19).…”

“…They consist primarily of extracellular carbohydrates and are produced by bacteria, fungi, and plants. Many studies showed that bonding of carbohydrates were the main aggregating agent (10,24). …”