ALBERT

Description: Tillage influences the retention and storage of organic matter (OM) in soil. We used a sequential density and particle-size fractionation to evaluate the total quantity and distribution of organic carbon (C) and nitrogen (N) in the profile of soils under mouldboard ploughing and no-till. Cores (0-60 cm) from four long-term tillage studies (in Prince Edward Island, Quebec, and two sites in Ontario) on soils of different textures, from sandy loam to clay were collected and divided into six depth increments. Four soil OM fractions were isolated on the basis of size and density from each sample. At two sites the standing stocks of C and N were larger in tilled than in no-till soil profiles at depths slightly greater than plough depth; tillage effects were also evident at a third site, where the mass of C in a layer close to the depth of ploughing was greater in tilled soils. Ploughing also had a substantial and consistent positive effect in all four soils on the quantity of C (and in some cases N) protected within aggregates, particularly at or near the bottom of the plough layer, and sometimes in surface soil layers. We attribute differences observed in whole soil C and N due to tillage mostly to differences in mineral-associated OM, particularly in soils with heavier textures, but the other size and density fractions could, together, account for as much as 25% of the difference. Because the C capacity level was not reached in heavy-textured soils, these soils show greater potential for further accumulation of C in the soil profile than coarse-textured soils, especially near the bottom of the plough layer.Key words: Light fraction, soil organic matter, soil tillage, physically-protected organic matter, no-till, soil texture

Description: Conservation tillage (CT) for potato crop land has been increasing in Atlantic Canada, but producers are concerned that fields managed in this way may be wet, slow to warm in spring, have increased debris at harvest, exhibit higher soil compaction and result in reduced yield. The objective of this study was to compare the effects of four tillage practices on potato yield, soil properties and weed growth over a 3-yr period. The four tillage practices were: (1 ) conventional autumn mouldboard plowing followed by spring secondary tillage; (2) spring mouldboard plowing followed by secondary tillage; (3) autumn chisel plowing followed by spring secondary tillage; and (4) spring CT. Tillage practices significantly affected soil water content (at both the 0- to 15-cm and 15- to 30-cm soil depths) with CT generally showing a greater soil water content prior to spring tillage in comparison to the other treatments. Soil temperature (at the 2- to 5-cm soil depth) prior to spring tillage was not influenced by tillage differences. Conservation tillage increased soil compaction at the 10- to 30-cm soil depth, but not to a level considered detrimental to root growth. Tillage treatments had no effect on amount of soil clods and plant debris passing over the harvester. Potato yield (range of 43 to 51 Mg ha-1) and quality were not adversely influenced by tillage practices. There were few treatment effects on individual weed species or groupings of annual, perennial and total weeds. Overall, CT can be a viable management alternative to conventional tillage because this practice does not negatively affect field management, potato yield, or soil quality. Key words: Conservation tillage, residue management, potato, soil temperature, soil moisture, tillage methods

Description: Conservation practices in potato (Solanum tuberosum L.) cropping systems can reduce excess tillage, provide crop residue cover, and maintain crop productivity; however, little is known about their long-term influence on soil biota and biological properties. Conservation tillage was evaluated in two potato rotations: a 2-yr barley-potato rotation and 3-yr clover-based (barley-red clover-potato) rotation initiated in 1994 on a fine sandy loam (Orthic Podzol) in Prince Edward Island, eastern Canada. Soil samples were obtained in 2003 from the 0- to 10-cm soil depth of the potato phase of both rotations to evaluate the influence of conservation, compared with conventional tillage, on changes in soil fertility, soil structural properties, soil C and N fractions, soil-borne pathogens, nematode communities, and micro-arthropod (Collembola and Acari) communities. The 3-yr conservation tillage practice improved soil structural stability, increased soil extractable P and K, increased soil organic C and total N and their particulate fractions, compared with the other treatments. Comparisons with earlier studies indicated that soil organic C had reached an equilibrium level at the 0- to 10-cm soil depth. Reduction of potato disease caused by Rhizoctonia solani was evident in the 3-yr rotation, compared with the 2-yr rotation, but was not influenced by tillage practice. Plant parasitic nematodes were not greatly influenced by rotation and tillage treatments; however, densities of the beneficial bacterial-feeding nematodes were increased under the 3-yr conservation tillage treatment. The abundance of micro-arthropods was increased by conservation tillage, while their diversity was mainly influenced by the rotation cycle rather than tillage practice. Overall, the 3-yr conservation tillage treatment provided a more beneficial soil biological condition than the other treatments, especially when compared with the 2-yr conventional tillage practice. Key words: Conservation systems, potato rotation, fine sandy loam, soil fertility, soil organic C and N fractions, soil structure, soil-borne pathogens, nematode, Collembola; Acari

Description: Interactions between tillage management for manure incorporation and rate of manure application may influence crop productivity and soil properties. This study was conducted to evaluate the effect of liquid swine (Sus scrofa L.) manure (LSM) applied at three N rates (40, 80, 160 kg ha-1), compared with mineral N fertilizer, in a 2-yr barley (Hordeum vulgare L.)-soybean (Glycine max L. Merr.) rotation, incorporated by two tillage methods (chisel plough and disc), on crop yield and quality and some soil properties, especially C parameters. The LSM was applied every second year in the spring, prior to barley seeding. The study was conducted over a 5-yr period on a Charlottetown fine sandy loam (Orthic Humo-Ferric Podzol) in Prince Edward Island. The experimental design was a split-plot with four replicates. Soil samples (0–60 cm) were obtained at the termination of the study to determine residual effects of the LSM on soil properties. The two methods of LSM incorporation had no differential effect on crop response. Generally, increasing the application rate of LSM increased the barley yield, but had no effect on grain N concentration. A residual effect on crop grain yield for the high rate of LSM was evident in the soybean year. Crop response to LSM was similar to that of mineral fertilizer. Application operations for LSM had no adverse effect on soil strength or soil bulk density. Soil properties (microbial biomass C, carbohydrates, water-stable aggregates) were not greatly influenced by LSM application, however, increases in particulate C (POM-C) were evident for the high LSM rate at the 10- to 30-cm soil depth. The study showed that for fine sandy loams in Prince Edward Island low to medium rates of LSM applied every second year could serve as a source of N for barley in barley-soybean rotations. Key words: Barley, soybean, liquid swine manure, fine sandy loam, soil properties, tillage incorporation, eastern Canada

Description: Intensive forms of soil management occur in potato (Solanum tuberosum L.) production systems, but little is known about the influence of such practices on soil biological properties. Microbial biomass C, phosphatase activity, and the abundance (number), richness (family groups), and diversity of soil micro-arthropods (Collembola and mites) were compared in conventional and adjacent integrated pest management (IPM) systems of 3-yr potato rotations, established on fine sandy loams in Prince Edward Island, Atlantic Canada. The study was conducted at two sites over a 2-yr period. Soil microbial parameters were generally similar between management systems. Management differences showed some effect on micro-arthropod abundance and richness in three of the eight comparisons. Under optimum soil-water conditions, both Collembola and mite communities increased over the growing season regardless of management system. Key words: Soil management for potato, Collembola, mites, soil microbial biomass carbon, acid phosphatase, integrated pest management

Description: An improved soil physical structure, associated with organic amendments in crop rotations, can be viewed as an emergent property. A study was conducted to evaluate the effect of applied compost on soil water retention and available water capacity, and other associative soil properties in a long-term 3-yr potato rotation established on a Charlottetown fine sandy loam (Orthic Humo-Ferric Podzol) in Prince Edward Island. Soil samples (0–10 cm) were obtained from two crop phases (barley and potato) during the fourth cycle of the rotation (after four compost applications) in the 12th year of the experiment. Except for particulate N, compost had little effect on soil organic matter. In comparison to the barley phase, a combination of compost and surface tillage in the potato phase was associated with improved soil porosity parameters and increased soil water contents at −33 kPa (“field capacity” ), −100 and −300 kPa matric potential, compared with the no-compost control. These results indicate that compost stabilized the tillage induced soil aggregates and macro-porosity in the potato phase. Regression analysis showed that soil volumetric water content at both −33 and −1500 kPa matric potential was significantly related to soil C concentration, although the soil available water capacity remained unchanged. The results imply that the “non-nutrient” compost effect on potato productivity was related to soil water retention. Key words: Soil water retention, soil physical and biochemical properties, compost amendment, tillage, potato rotation, eastern Canada