Intensive Potato Production Research Articles

Soil variation within a hummocky podzolic landscape under intensive potato production

The purpose of this study was to determine if relationships between landscape position and soil properties occurred on a podzolic landscape with hummocky meso-topography, which is under intensive potato production in New Brunswick, Canada. Elevation was measured on an approximately 5 m grid spacing and used to construct a digital elevation model. Selected soil textural, morphological and chemical properties were measured on a 7×17 grid with 25 m spacing. Landform segmentation was used to divide sampling locations into eight landform elements based on profile and plan curvature, slope gradient and specific dispersal area. Orthic Humic Regosols and Orthic Sombric Brunisols were predominant in upper slope positions, whereas gleyed subgroups of the main soil orders were commonly found in the concave, lower slope positions. Lower, concave slope positions generally had lesser sand and coarse fragment contents, greater silt, organic carbon and 137Cs contents, and greater depth to C horizon and to bedrock than upper, convex slope positions. In contrast, A horizon thickness, clay content, soil pH and soil test P showed little relationship to landscape position. Landform segmentation was effective in characterizing the spatial distribution of soil loss at the study site, as indicated based on 137Cs content, and of soil taxa. However, the resulting landform elements had generally small differences in parameters such as SOC, sand, silt and clay content, which are commonly considered important in agricultural production. The landscape examined in this study appears to be dominated by soil loss and the closely related homogenizing effects of intensive tillage for potato production. The properties that continue to show a clear relationship to landform position are largely remnant properties (e.g., depth to bedrock or to the C horizon), whose pattern reflects a stronger hydrological and/or pedological control. The results provide further evidence that human-induced changes in soil can fundamentally alter the natural pattern of soil distribution in the landscape, even over relatively short (i.e., 100 years) time scales.

Hay mulching to reduce runoff and soil loss under intensive potato production in northwestern New Brunswick, Canada

Soil erosion by water associated with potato production in northwestern New Brunswick has been identified as one of the most severe soil degradation problems affecting soil quality in Canada. The objectives of this study were to evaluate the effectiveness of applying various rates of hay mulch following potato (Solanum tuberosum L.) harvest in reducing runoff and soil loss rates under northwestern New Brunswick climatic and soil conditions and to determine the impact of the various hay mulch application rates on potato yield. Wischmeier-like runoff-erosion plots (10 m wide by 30 m long) on a Holmesville gravelly loam soil were used. Annual hay mulch application rates of 0.00, 2.25, 4.50 and 9.00 t ha-1 wet mass were evaluated under continuous up-and-down-slope potato production on 8 and 11% slopes between October 1995 and October 1999. During the study period, annual precipitation was lower than normal. Calculated rainfall erosivities were 102, 66, 73 and 133% of the value typically used for conservation planning in this region (1276 MJ mm ha-1h-1). Seventy-three percent of the average annual erosivity for the 4-yr period was associated with storms occurring in June, July, August and September. Hay mulching at rates of 2.25, 4.50 and 9.00 t ha-1 conserved on average 13, 18 and 28 mm of June to September precipitation, respectively. Mean annual soil losses were reduced to 14, 7 and 2% of the control (5.6 t ha-1) by the 2.25, 4.50 and 9.00 t ha-1 treatments, respectively, on the 11% slope and to 43 and 24% of the control (2.0 t ha-1) on the 2.25 and 4.50 t ha-1 treatments, respectively, on the 8% slope. Eroded sediment silt, clay and organic matter (OM) contents were 1.6, 1.9 and 2.3 times the content of the surface soil at the experimental site. Mulching at rates as low as 2.25 t ha-1 reduced nutrient losses of NO3-N and available P, K, Ca and Mg to 26, 18, 28, 20 and 24% of control, respectively, on the 11% slope, and to 81, 50, 82, 66 and 77% of control, respectively, on the 8% slope. However, levels of nutrient losses from the controls were low to begin with (2.0, 0.4, 2.8, 10.9 and 1.6 kg ha-1 of NO3-N, and available P, K, Ca and Mg, respectively). Both total and marketable potato crop yields from all 2.25 and 4.50 t ha-1 treatments were in excess of 5% greater than their controls; however, only the increases in total yields from the 2.25 and 4.50 t ha-1 treatments and marketable yield from the 4.50 t ha-1 treatment on the 8% slope were significantly greater at P< 0.05. Yield of potato on the 9.00 t ha-1 treatment showed a consistent increase in total yield over the 4-yr period, going from 80% of control in 1996 to 127% of control in 1999, indicating a possible improvement in soil productivity. Hay mulching at rates up to 9.00 t ha-1 did not increase the incidence of disease or other defects. Hay mulching was found to be an effective tool for reducing soil loss while maintaining, and in some cases enhancing, potato yield. Key words: Hay mulching, soil loss, water erosion, organic residues, sediment composition, nutrient loss, erosivity

Organic matter and aggregation in a degraded potato soil as affected by raw and composted pulp residue

Soils under intensive potato (Solanumtuberosum L.) production are often low in organic matter content and microbial activity. Pulp fibre residue addition may restore the quality of these soils. An experiment was initiated in which raw or composted pulp fibre waste was added to a Fredericton sandy loam (Orthic Humo-Ferric Podzol) in New Brunswick (Canada). Each material was applied at 45 Mg (dry weight) ha–1 and 90 Mg (dry weight) ha–1 before planting. Soil was under continuous potato (cv. Russet Burbank) for 3 years. The raw and the composted pulp greatly increased soil organic matter (SOM) content, the C/N ratio, macroaggregation, C mineralization, microbial biomass C (MBC) and enzyme activities for the whole duration of the experiment but had no effect on its total N. Most of the SOM increase was found in the macroorganic matter fraction. The SOM, C/N ratio, macroaggregation, C mineralization and MBC decreased from the time of application. No major difference was found between materials except for CO2-C release in the incubation which was higher for the composted than for the raw pulp. This study indicated that pulp fibre, either applied raw or composted, increased SOM and macroaggregation and promoted microbial growth and activity in this potato soil which was low in C content. The beneficial effects on soil physical and biochemical properties were still present after 3 years of continuous cropping.

Mulching potatoes: Aspects of mulch management systems and soil erosion

Intensive potato production occupies much of the sloping arable land of Prince Edward Island, Canada, and is at the center of soil erosion concerns in this province. Corrective considerations have turned recent attention to mulching, but there is limited knowledge of its workability or effectiveness in potato systems. This study looks at the effect of mulching on soil loss from potatoes grown on standard erosion plots, and examines a relatively simple approach to assessing soil-surface splash detachment (splash erosion) under mulch-management systems with potatoes. Three sizes of splash cup (25, 50, and 100 mm in diameter) were used under simulated rainfall at 150 mm·h−1 for 10 minutes to measure splash erosion on potato plots under mulch-management systems which, respectively, left surface coverage of ∼ 5%, ∼ 15%, and ∼20%. The lowest straw coverage gave up to 56% more erosion than either of the two higher coverages. The 25-mm splash cup yielded 14% more sediment splash than the 100-mm splash cup on the basis of unit surface area of soil in the splash cup (unit area). Regression modeling of unit-area splash against straw cover showed an exponential decay in splash detachment with increasing straw cover. On the erosion plots, soil loss with mulching was half of what it was without mulching; and soil water retention was 5% greater with mulching.

Soil organic matter quality and aggregate stability under eight potato cropping sequences in a fine sandy loam of Prince Edward Island

Soil degradation and soil organic matter (SOM) reduction have long been suspected to occur under intensive potato (Solanum tuberosum L.) production in Prince Edward Island. Thus, this study was conducted to evaluate the effect of eight potato cropping sequences involving barley (Hordeum vulgare L.), ryegrass (Lolium multiflorum L.), red clover (Trifolium pratense L.) and barley under-seeded with red clover on aggregate stability and SOM properties of a Charlottetown fine sandy loam (Orthic Humo-Ferric Podzol). Total C and N, light-fraction (density < 1.7 g cm−3) C (LF-C) and light-fraction N (LF-N), microbial biomass C (MBC), carbohydrate content, alkaline phosphatase activity (APA) and aggregate stability were determined in the 0- to 15-cm soil layer in the 6th and 10th years of the trial. Average C and N contents were 20 to 27% greater in sequences that included 3 or 4 yr of potatoes and a high frequency of red clover than in a 9-yr potato sequence; and were attributed to the less frequent tillage and higher organic matter inputs associated with the forage component. The response for MBC, LF-C, LF-N and APA was greater than those for total C and N suggesting that the former parameters may better reveal SOM changes caused by variations in potato management than the latter. Light-fraction N was particularly sensitive to the inclusion of perennial legumes in the cropping sequence. Wet-aggregate stability was 33% higher after 6 yr in the sequence with 50% frequency of red clover than in the continuous potato system, but no effect was noted after 10 yr. The results of this study indicate that sequences which are limited to 30 to 40% of potatoes and have a high frequency of perennial forage such as red clover, lead to greater SOM content and quality of a Charlottetown fine sandy loam compared to continuous potatoes. Trends in aggregate stability generally followed those of SOM fractions but the effects were relatively smaller and varied with time. Key words: Potato, Solanum tuberosum L., soil aggregation, organic matter, carbon, nitrogen, light fraction, microbial biomass

Potential use of underseeded barley to increase carbon inputs to a loam soil in the New Brunswick potato belt

Organic carbon depletion as a result of intensive potato production is a serious concern in northwestern New Brunswick, Canada. Underseeding of rotational grain crops with selected grasses and legumes is being used by farmers to increase crop residues in order to maintain soil organic carbon levels. The objectives of this study were to quantify changes in selected soil propertiesm, effects on grain yield, and increases in total biomass production resulting from different underseeding treatments on a Caribou fine-loamy Brunisolic Gray Luvisol. Clovers, ryegrasses and a mixture of timothy, Alsike and red clover were underseeded in Chapais barley plots. Underseeding did little to improve soil bulk density, macroporosity and saturated hydraulic conductivity of the upper plow layer (4–12 cm depth) over one growing season. Averaged over a 3-yr period, underseeding did not significantly affect barley grain yields; however, annual reductions of up to 17% were experienced with some of the more aggressive companion crops, such as Lemtal Italian ryegrass. Underseeding significantly increased total biomass contributions (residues) to the upper 20 cm of the soil by 40 to 90%, making the year in grain production a potential net organic carbon supplier rather than an organic carbon depletor. Key words: Companion crop, roots, soil organic carbon, soil bulk density, soil permeability, crop residue

Effects of intensive potato production on soil quality and yield at a benchmark site in New Brunswick

The cumulative extent of soil redistribution by erosion and tillage was measured by comparing the 137Cs content of a soil under intensive potato production with that of an undisturbed forest soil. Soil redistribution rates estimated from 137Cs contents for the cultivated site varied from a loss of as high as 19.0 kg m −2 year −1 (190 t ha −1 year −1) to a gain of as much as 4.3 kg m −2 year −1 (43 t ha −1 year −1), with an average of 5.3 kg m −2 year −1 (53 t ha −1 year −1) soil loss. Measured soil 137Cs content and calculated soil loss (and deposition) were both found to be correlated with total potato yield ( P < 0.01), and with tuber specific gravity ( P < 0.05), in the two years of yield measurements (1991 and 1992). These years had near normal growing season precipitation, but contrasting distribution patterns of precipitation during the growing season. Estimated soil loss and gain were also correlated ( P < 0.01) with soil organic carbon and soil phosphorus contents. It is concluded that soil redistribution within the site, caused by either water erosion or tillage, or a combination of both these processes, had a marked effect on soil productivity.

Integrated crop management, the basis for environment friendly crop protection of potatoes

Relatively large amounts of pesticides are needed to control diseases and pests in modern, intensive potato production. Integrated crop management offers a way of reducing the need for pesticides. It aims to reduce costs and improve the quality of the product and of the production methods, while maintaining soil fertility and the quality of the environment. The components of integrated crop management are described. Prevention of diseases and pests has high priority. If diseases or pests are present, non-chemical control methods are preferred and chemical control is based on economic criteria and the monitoring of the soil and crops. The contribution of integrated crop management to the control of two important fungal diseases, late blight (Phytophthora infestans), and stem canker (Rhizoctonia solani) and of one pest, potato cyst nematode (Globodera spp..) is described. The prospects for further development of integrated crop protection are discussed.

Potato early dying—A serious threat to the potato industry

Potato early dying (PED) is characterized by a loss of plant vigor during mid to late summer followed by senescence and death of the crop a few weeks prior to normal maturity. This disease is of serious importance in areas of long-term or intensive potato production and is largely uncontrolled. Symptoms of PED, which are difficult to distinguish from normal senescence, especially in early-maturing cultivars, are uneven chlorosis and necrosis of vines and tan discoloration of vascular tissues. The basic cause of PED is the soil fungusVerticillium. Two species are involved—V. alboatrum predominating in cooler areas andV. dahliae in warmer areas. Both fungi commonly occur in cultivated soils and persist as melanized hyphae or microsclerotia, respectively. Infection occurs through roots followed by colonization of the vascular system. Contamination of uninfested fields can occur by wind or mechanical movement of soil-borne propagules or introduction of infested seed stock. AlthoughVerticillium is the primary pathogen in potato early dying, other soil organisms are involved, resulting in a “disease complex.” Research is under way in many areas to further our understanding of these pathogenic interactions and to exploit this knowledge for use in new systems of prediction and control.

EFFECTS OF TOPSOIL LOSS AND INTENSIVE CROPPING ON SOIL PROPERTIES RELATED TO THE CROP PRODUCTION POTENTIAL OF A PODZOLIC GREY LUVISOL

A 5-yr field study was conducted at Charlottetown, Prince Edward Island to determine the effect of losses of topsoil and organic matter likely to accrue from intensive potato production on the crop production potential of a loam to fine sandy loam Podzolic Grey Luvisol representative of major soil types used for potato production on P.E.I. The top 7.5 or 15 cm of the original 20-cm-thick Ap horizon was removed from strips on either side of a control (intact soil) strip. These strips were cropped under a 5-yr potato-barley rotation. Soil-loss treatments reduced the organic carbon content of the new 20-cm-thick Ap horizons formed by tillage by 9.4 and 37%, respectively, from 51.3 tonnes (ha∙20 cm)−1 in the original Ap horizon. Similarly, mineralizable nitrogen levels were reduced initially by 21 and 64%, respectively, compared with the intact soil. During the subsequent 2 yr, mineralizable nitrogen levels in the Ap horizons of the intact and minus 7.5-cm strips fell by 35%. Soil-loss treatments had no effect on Ap horizon texture, porosity, or bulk density. However, losses of topsoil reduced the soil’s capacity to store plant-available water (33 kPa – 1500 kPa) within the rooting zone above a Bt, horizon (bulk density 1.67 tonnes∙m−3) by 1.3 and 3.4 cm of water, respectively, from 9.8 cm for the intact soil. Rainfall patterns on P.E.I. suggest that such reductions in water storage capacity may reduce the soil’s crop production potential in 2 out of 5 yr. Key words: Topsoil loss, intensive cropping, Luvisol, organic carbon, mineralizable nitrogen, water storage capacity

Crop Rotation and Soil Pathogens — Trends in Germany

AbstractThe need to cut costs has led to a simplification of crop rotation in several fields of plant cultivation. The results of Thormann, who has grown wheat continuously on parts of his farmland for 10 years, are discussed. Also, the preliminary results of our own experiments with increasing proportions of wheat and barley suggest that more wheat and barley may be cultivated in crop rotation than is allowed according to the conventional limits determined by the increase of foot rot diseases and cereal root eelworm. Even in successive crops of maize the problem of soil‐borne pathogens can be tackled: the spread of blister smut is stopped by the control of the frit fly and by selection of tolerant varieties; root and stem rots of maize are overcome by the selection of appropriate varieties, too. On the contrary, the potato root eelworm is a serious pest in all sites of intensive potato production. Only an integrated control including the use of resistant varieties and the application of nematicides gives success. Much research work has to be done mainly to get more information on the biotical defence mechanisms of the soil.