Intensive Potato Production Research Articles

Effects of organic amendments and cover crops on soil characteristics and potato yields

ABSTRACT Intensive potato production may reduce the soil organic matter content (SOM), which may impact several soil functions and increase the incidence of potato diseases. We examined if cover crop and addition of organic materials may counteract these effects. Organic materials were one application of biochar mixed with liquid digestate (BLD); solid digestate (SD); or farmyard manure (FYM); with or without winter rye as cover crop, in a field with regular potato growing. Organic amendment increased SOM, especially for FYM and BLD, while cover crop did not affect SOM. Yet, cover crop increased tuber yields in the second year, and reduced the severity of potato diseases by 10% in post-harvest potatoes in both years. In the second year, the number of marketable potatoes after storage increased by 37% with cover crop. Organic amendments did not affect potato yield or quality, but the proportion of marketable potatoes tended to be higher in the amended soil. By lab incubation, BLD showed the largest potential for SOM storage, up to 32 years, followed by FYM and SD. Cover crops and organic amendments is recommended in potato production, especially for early potatoes where there is sufficient time after harvest to establish a good cover crop.

Nitrate leaching and potato tuber yield response to different crop rotations

Intensive potato production causes nitrate leaching and contributes to groundwater nitrate contamination. This study investigated the impacts of five potato rotations on nitrate leaching and tuber yield using a plot-based field experiment in combination with numerical modeling in Prince Edward Island, Canada, from 2014 to 2021. The rotations included barley underseeded with red clover–red clover–potatoes (B–RC), three buckwheat–buckwheat–potatoes rotations with buckwheat harvested for seed (BWS), terminated mid-season by disking (BWD) and terminated mid-season by mowing (BWM), and barley underseeded with timothy–timothy–potatoes (B–T). The buckwheat rotations represented typical management options for wireworm control, B–RC represented the local industry standard rotation, and B–RC and B–T acted as controls. Rotation-based total nitrate leaching that occurred from 23 October 2014–20 July 2020 (covering two 3-year rotation cycles) was calculated using a combination of lysimeter sampling and soil drainage numerical modeling. The three buckwheat rotations had comparable effects on total nitrate leaching and marketable tuber yield in most cases. When treated as a group, the buckwheat rotations (BW) were shown to significantly reduce total nitrate leaching by 30% within the two rotation cycles, while significantly increasing marketable tuber yield (mean of 2016 and 2019 potato yields) by 16% compared to B–RC. However, BW produced 58% more total nitrate leaching than B–T and had a comparable marketable tuber yield. Total nitrate leaching and tuber yield were highly correlated (R 2 = 0.95) with nitrogen (N) surplus (calculated as total N supply minus N removal at crop harvest within the total nitrate leaching accounting period), with higher N surplus producing higher nitrate leaching and lower tuber yield. Nitrogen removal accounted for 33%, 36% and 53% of total N supply for B–RC, BW and B–T, respectively, indicating very low N use efficiency. These findings suggest that N surplus was the key explanatory variable for the variations in total nitrate leaching and tuber yield, and adequately accounting for N credits from the preceding rotation crop (especially red clover) is important to minimize nitrate leaching while maximizing potato productivity. • Buckwheat–buckwheat–potatoes produced 30% less N leaching and 16% more tuber yield than barley–red clover–potatoes. • Buckwheat–buckwheat–potatoes produced 58% more N leaching and comparable tuber yield, compared with barley–timothy–potatoes. • Adequately accounting for N credits from preceding crops is required to reduce N leaching and enhance tuber productivity.

Modeling Potential production and yield gap of potato using modelling and GIS approaches

Understanding yield potential (Yp) and yield gap (Yg) in current intensive potato (solanum tuberosum L.) production is essential to meet future food demand with the limited resources. Evaluating yield gap is a strong approach to estimate maximum production potential when all factors are in the best condition. A complete estimation of yield gap and potential yield across all major potato producing regions in Iran is lacking. The global yield gap atlas (GYGA) protocol was used to estimate potential yield of potato in Iran. This protocol is based on the climatic zones (CZs) and the reference weather stations (RWS) buffer zones, soil types in each buffer zone. Thirty-five RWS buffer zones in potato producing regions were selected, and total potato area in the RWS buffer zones covered 83% of the whole potato harvest area. According to the results, the average Yp was 67.3 t ha–1 and actual yield (Ya) was 30 t ha–1. Therefore, the average tuber yield gap was 37.3 t ha–1. These results indicate that the Potato producers achieved 45% of the potential yield in Iran. Iranian farmers produced 5 million tons of potato from about 164,000 ha. If they can obtain only 80% of Yp (53.8 t ha–1), amount of potato production will be 8.8 million tones. As result, they can produce 5.2 million tons tuber yield of potato in 97,000 ha cultivation area. Thus, with closing yield gap and increasing potato production, it is possible to decrease potato lands.

To justification of parameters of ultra-low-volume spraying with pneumatic slot sprayers

Intensive potato production technology provides for improving the process of planting tubers with a potato planter with simultaneous treatment with protective and stimulating liquids. To this end, the design of the device was developed, and the parameters of pneumatic slot sprayers recommended for treated tubers with working fluids were optimized.

Aerial dispersal of Spongospora subterranea sp. f. subterranea, the causal agent of potato powdery scab

Potato powdery scab caused by Spongospora subterranea subsp . subterranea (Sss) causes extensive damage to the quality and marketability of tubers. Disease outbreaks in potatoes grown in virgin soils in south Israel, lead us to the hypothesis that wind-driven inoculum may also be a source of new infections. Wind and ground traps (13 of each type) were positioned near contaminated commercial potato fields with a history of powdery scab in two plots during 2013–14 (‘Nave 5’ and ‘Nave 89’). Quantification of pathogen density in soil/dust was carried out by DNA extraction and qPCR analysis. In ‘Nave 5’ plot, 58 and 45% (December and January, respectively) and 75 and 50% of the ground and wind traps, respectively, were Sss-positive, with no significant differences in Sss concentrations. In ‘Nave 89’ plot, the percentage of Sss-positive traps increased from 31% and 18% in the ground and wind traps, respectively, in February, to 100% in both trap types, in April, with no significant differences. Evaluation of the dispersal distance of Sss inoculum from contaminated fields was examined in soil samples taken from the top layer of the ground in the uncultivated area adjacent to the contaminated commercial potato fields with a history of powdery scab, in two sites (‘Nave 5’ and ‘Shalom 7’) during 2016. All soil samples, taken from uncultivated areas near the infested fields in various distances of up to 750 m, were Sss positive. This study demonstrated that Sss can be dispersed by wind, particularly in an intensive potato production region where contaminated fields exist.

Nitrogen dynamics and leaching potential under conventional and alternative potato rotations in Atlantic Canada

Elevated nitrate levels in surface and ground waters on Prince Edward Island (PEI), Canada, are of concerns for both drinking water quality and aquatic habitat protection. These elevated nitrate levels have been closely linked to excessive nitrogen (N) leaching from land under intensive potato production. An improved understanding of the effects of conventional and alternative potato rotation systems and associated rotation crops on N leaching and potato tuber yield is needed to inform if the alternative rotation can impose less impact on water quality while maintaining the economic viability. We contrasted two field based, 3-year potato-based rotations: a potato-barley-red clover (PBC) rotation (conventional), and a potato-soybean-barley (PSB) rotation (alternative), from 2014 to 2017. Crop tissue N accumulation, soil mineral N and N concentrations in soil leachate were measured during the experimental period for assessing N dynamics and potential N leaching loss from the two systems. On a rotation basis, soil mineral N and N concentrations in leachate under the PBC rotation were significantly higher when compared with the PSB rotation after the planting of red clover. The overall N utilization efficiency of the PSB rotation was 1.6 times to that of the PBC rotation. Due to the high N surplus during the red clover and potato phase, total N surplus of the PBC rotation across the 3 years was significantly higher than that of the PSB rotation. A strong positive correlation was found between nitrogen surplus and average seasonal leachate nitrate concentration. On rotation crop level, potato and red clover phases produced most of the potential N leaching loss during the rotation cycles. The red clover phase accumulated the largest amount of N and produced the largest amount of N loss when compared with other rotation crops. Nitrogen leaching occurred primarily in the non-growing season, with different rotation crops demonstrating different leaching patterns. In the potato phase, N leaching occurred primarily between October and late December. Nitrogen leaching sourced from the red clover spanned a long-lasting process: the high mineralization rate and extended mineralization period of the residue led to carry-over of N leaching into the subsequent growing season. In addition, potato yield following the PSB rotation was 13.4% higher than the PBC rotation in 2017. These data suggested that the alternative PSB rotation could increase potato yields while reducing N leaching compared to the conventional PBC rotation.

Impacts of Crop Rotation and Tillage Practices on Potato Yield and Farm Revenue

Core Ideas The two‐step regression simulation approach was the most appropriate model to evaluate all important explanatory variables on mean potato yield.Potato yield increased when the frequency of potato increased in the rotation.Rotations with lower potato frequency had higher net revenue for the potato year; however, rotations with higher potato frequency had higher overall net revenues.The overall financial impacts of rotations with lower potato frequency were negative.Other incentives for adopting beneficial management practices are necessary. To reduce the impacts of intensive potato (Solanum tuberosum L.) production systems on the environment, beneficial management practices (BMPs) (e.g., crop rotation and conservation tillage) have been promoted in Atlantic Canada. However, quantitative information on the impacts of BMPs on yield and farm revenue is still lacking. Direct assessment of BMPs in operating farms is difficult because producers adjust other inputs and practices when implementing BMPs. A dataset with 5 yr of crop rotation, farm inputs, and soil and climate data was obtained from farms in New Brunswick, Canada. Two‐step regression with a stochastic production function method was used to assess the impacts of three crop rotations and two tillage practices on potato yield. Potato yield increased when potato frequency increased in the rotation. This effect was largely caused by increased fertilizer and other inputs on rotations with a higher potato frequency. Spring moldboard plowing had negative effects on yield compared with fall moldboard plowing. The two‐step yield model was used with different scenarios to estimate the effect of crop rotation on farm revenue net of input costs. Rotations with lower potato frequency had higher net revenue for the potato year, largely because of reduced input costs. However, rotations with higher potato frequency had higher overall (multiyear) net revenues because of the more valuable potato years in the rotation. Therefore, without considering the long‐term impacts on the environment, the overall financial impacts of rotations with lower potato frequency were negative. This suggests that other incentives for adopting BMPs are necessary.

Hydrogeophysical monitoring reveals primarily vertical movement of an applied tracer across a shallow, sloping low-permeability till interface: Implications for agricultural nitrate transport

Intensive potato production is an important contributor to groundwater and surface water nitrate contamination in the province of Prince Edward Island (PEI), Canada. In PEI, the presence of a permeability contrast between soil and the underlying compact basal till at approximately 1 m depth is known to cause temporary perched water table conditions, but the implications for agricultural nitrate transport are not well understood. This study is the first detailed field investigation to examine the impact of the soil – compact basal till interface on vertical and lateral subsurface flow of water and solutes on a moderate hillslope in PEI. A surface-applied tracer test was conducted and a shallow drain-tile pipe system, with a tipping bucket gauge, was installed down-gradient of the tracer application to monitor lateral subsurface flow. In addition, three-dimensional electrical resistivity imaging (ERI) was employed to monitor the evolution of the applied tracer plume over a period of 1 year. A small scale, transient flow and transport model was used to simulate the tracer test and to investigate the sensitivity of tracer transport to selected parameters (primarily, the hydraulic conductivities of the soils and underlying compact basal till). Monitoring, conducted from October 2013 to June 2015, and numerical modeling showed a strong tendency for vertical flow of water and tracer through the soil – compact basal till interface as opposed to lateral down-slope subsurface flow. Water balance calculations estimated a total vertical flow of 94.5% of the infiltration for the October 2014 to January 2015 period. The preference for vertical over lateral flow and transport was consistent with electrical resistivity images for the same time period. These findings indicate that the fate of infiltrating water and dissolved nitrate is the deeper bedrock aquifer water table, and that intermittent perched water table conditions do not result in significant lateral flow toward nearby surface waters.

Short‐Term Effects of Diverse Compost Products on Soil Quality in Potato Production

Core Ideas Compost application increased soil organic matter content and improved soil quality. Compost products with greater C concentrations resulted in greater soil improvements. Particulate organic matter C was the index most responsive to compost addition. Mature composts with greater C concentrations and dry matter were most suitable. Soil quality has declined with intensive potato production practices in New Brunswick, Canada. Compost application may rapidly increase soil organic matter (SOM) and reverse declining productivity. This study assessed five diverse compost products for their short‐term effects on soil quality, and in particular SOM. Selected compost products derived from a range of forestry, marine, and municipal waste materials were compared with a non‐amended control. Treatments were applied to field plots at 45 Mg ha–1 dry weight in October of 2014 and 2015. Biological, chemical and physical soil properties under potato production in 2015 and 2016 (after one and after two consecutive applications) were used to evaluate soil quality. Compost application increased soil pH and concentrations of Mehlich‐3 extractable nutrients (K, Ca, Mg, and S). Compost reduced bulk density in the potato hill by 8% in both years. Particulate organic matter (POM) was the most sensitive indicator to compost‐application with twofold increases in POM‐C. Compost application increased soil organic carbon by 24% in 2016 and also increased permanganate oxidizable carbon, and soil respiration. Several soil properties were strongly correlated with compost composition, with better quality composts (i.e., more mature; greater in C, N, and other plant‐available nutrient concentrations) producing the greatest soil quality response. Overall, mature composts with greater C concentrations (i.e., low ash) and greater dry matter were most suitable for enhancing soil quality in New Brunswick potato production systems.

Особенности интенсивного производства картофеля в Тульской области

Особенности интенсивного производства картофеля в Тульской области

Modeling land-based nitrogen loads from groundwater-dominated agricultural watersheds to estuaries to inform nutrient reduction planning

Summary Excessive nitrate loads from intensive potato production have been linked to the reoccurring anoxic events in many estuaries in Prince Edward Island (PEI), Canada. Community-led watershed-based nutrient reduction planning has been promoted as a strategy for water quality restoration and initial nitrate load criteria have been proposed for the impacted estuaries. An integrated modeling approach was developed to predict base flow nitrate loads to inform the planning activities in the groundwater-dominated agricultural watersheds. Nitrate load is calculated as base flow multiplied by the average of nitrate concentration at the receiving watershed outlet. The average of nitrate concentration is estimated as the integration of nitrate leaching concentration over the watershed area minus a nitrate loss coefficient that accounts for long-term nitrate storage in the aquifer and losses from the recharge to the discharge zones. Nitrate leaching concentrations from potato rotation systems were estimated with a LEACHN model and the land use areas were determined from satellite image data (2006–2009) using GIS. The simulated average nitrate concentrations are compared with the arithmetic average of nitrate concentration measurements in each of the 27 watersheds for model calibration and in 138 watersheds for model verifications during 2006–2009. Sensitivity of the model to the variations of land use mapping errors, nitrate leaching concentrations from key sources, and nitrate loss coefficient was tested. The calibration and verification statistics and sensitivity analysis show that the model can provide accurate nitrate concentration predictions for watersheds with drainage areas more than 5 km 2 and nitrate concentration over 2 mg N L −1 , while the model resolution for watersheds with drainage areas below 5 km 2 and/or nitrate concentration below 2 mg N L −1 may not be sufficient for nitrate load management purposes. Comparisons of normalized daily stream discharges among the active hydrometric stations indicated that stream base flow could be prorated for nitrate load calculation from the nearest gauging station in the absence of discharge measurements. Annual nitrate losses, including aquifer long-term storage, denitrification, and riparian plant uptake were estimated to be 0.8 mg N L −1 , corresponding to 3.4 kg N ha −1 . The maximum and median base flow nitrate loads to the estuaries from among the 27 calibration watersheds were predicted to be 28.4 and 8.7 kg N ha −1 respectively with a root mean square error (RMSE) as 2.3 kg N ha −1 . From among the 75 watersheds selected for model verification, the maximum and median base flow nitrate loads to the estuaries were estimated to be 29 and 5.5 kg N ha −1 respectively with RMSE as 2.6 kg N ha −1 . At the estuaries with nitrate loads above the medians, the predominant nitrate sources (75–98%) were derived from the potato rotation lands, highlighting the importance of N use management with potato production for water quality restoration; nitrate load derived from atmospheric N deposits was estimated to account for 3.6–13% of annual nitrate loads in watersheds with nitrate loads exceeding the median values. The application of the model to nutrient reduction planning in the Southwest River watershed implies that a significant change on cropping practices has to be made in order to mitigate the anoxic events in this highly impacted agricultural watershed.

Different vegetable crop rotations affect soil microbial communities and soilborne diseases of potato and onion: literature review and a long-term field evaluation

A major concern in potato and onion production worldwide is the sustainability of crop production systems using short-term rotations. Although rotation crops are known to influence soil microbial communities, few long-term field studies have investigated effects of potato and onion crop rotations on soil microflora and soilborne diseases. A long-term trial (10 years) was established in New Zealand in the 2004–05 season to determine changes in soil characteristics, soil biological communities, plant productivity and soilborne diseases resulting from different crop rotations. Six different crop rotation ‘treatments’ were used: three were onion-focused and three were potato-focused. For both the onion- and potato-focused rotations, one treatment was continual monoculture, one was biennial alternating onion and potato (‘conventional’ rotation, common local commercial practice) and one was a 4-year cycle where the onion or potato crops were grown every fourth season with different crops in the intervening seasons (‘sustainable’ rotation). The results of the rotations were evaluated at the end of 2012–13, nine growing seasons after the trial began. Soils from the three potato-focused rotations had similar microbial biomass carbon (C) and nitrogen (N), total C and N, and enzyme activity, but had different microbial activity parameters. Soils from the three onion rotations differed in organic matter content, total C and N, enzyme activity and carbohydrate utilization. The main factor correlated with potato diseases (stem canker, black scurf) and crop yields was the amount of Rhizoctonia inoculum in the soil. Onion yields in 2012–13 were correlated with the severity of pink root during the growing season. Total microbial activity in soil gave better relationships to soilborne disease incidence (Rhizoctonia stem canker of potato or pink root of onion) and to crop yields, than soil chemical parameters (pH, nutrient status, C:N ratio) or other microbiological parameters (microbial biomass, total culturable bacteria and fungi, and microbial diversity). This research has broadened understanding of effects of crop rotations on soil microbial community characteristics, soilborne diseases and crop productivity of potatoes and onions grown in a soil and an area where intensive vegetable production is common. This knowledge will assist growers to increase crop yields and reduce soilborne pathogens in a sustainable manner. Based on the results from this study, intensive potato and onion production should require these crops to be grown within 4-year crop rotations in order to foster sustainable yields and minimize soilborne diseases.

Controls on Nitrate Loading and Implications for BMPs Under Intensive Potato Production Systems in Prince Edward Island, Canada

AbstractPotato production is critical to economy of Prince Edward Island (PEI), but has been linked to increasing groundwater nitrate contamination and anoxic events in estuaries. Given that PEI is entirely groundwater‐dependent for potable water, this has resulted in considerable pressure to find solutions to protect water quality. However, our understanding of the controls on nitrate loading to groundwater, and the consequent potential to mitigate nitrate loading through beneficial management practices (BMPs), is limited. In PEI, flow and nitrate transport in the vadose zone are controlled by the matrix porosity of the till and sandstone, while flow and transport in the saturated zone are controlled by a conductive fracture network with limited storage capacity. Diffusion of nitrate stored in the matrix may introduce a significant time lag between reduced nitrate loading from implementation of BMPs and measureable improvement in groundwater quality. BMPs with potential to mitigate nitrate loading to groundwater through improved nitrogen fertilizer practices in producing potato crops have been identified, but implementation of these practices alone is not sufficient to control nitrate loading due to the economic context of potato production. Additional BMPs for improved potato cropping systems have also been identified; however, reducing the intensity of agricultural production, including the proportion of land in potato production, at the watershed level may be required to meet the drinking water guideline for nitrate in PEI. Given the important role of market forces in determining profitability of crop production, it becomes challenging to modify crop production practices to meet an environmental goal without some additional external incentive or public pressure.

Differentiation of potato ecosystems on the basis of relationships among physical, chemical and biological soil parameters

Boiteau, G., Goyer, C., Rees, H. W. and Zebarth, B. J. 2014. Differentiation of potato ecosystems on the basis of relationships among physical, chemical and biological soil parameters. Can. J. Soil Sci. 94: 463–476. A study of soil physical, chemical and biological properties of five cultivated agro-ecosystems (two conventional potato, two organic potato and one cereal production systems) and two uncultivated agro-ecosystems (pasture and 20-yr abandoned potato field) was carried out at 21 field sites over 3 yr in New Brunswick, Canada. Twenty-four of the initial 42 variables chosen for their significant response to differences among farming systems were used in a principal component analysis to understand their relationships with the agro-ecosystems studied. The chemical, physical and biological soil properties considered contributed to a single dominant factor (PCI) of agricultural soil health representing soil organic matter dynamics. Conventional, uncertified organic and certified organic potato agro-ecosystems were lowest, intermediate and highest, respectively, on the PCI gradient. Conventional potato systems were characterized by high erosion, high soil bulk density, high soil test sulphur and phosphorus and high bacterial counts. Certified organic potato systems formed a separate group with the reference ecosystems (i.e., pasture and abandoned potato field under long-term rejuvenation). This group was characterized by high soil organic carbon, high soil aggregate stability, high soil water-holding capacity and high meso- and macro-fauna counts. The uncertified organic potato production system and organic barley system were characterized by average values, intermediate between conventional and certified organic potato systems. Results confirmed the strong negative impact of intensive cycles of conventional potato production on soil health. The clear separation observed between conventional, uncertified organic and organic potato ecosystems indicates that the positive impact of rotations and other management practices must be sustained over long periods for full rehabilitation of soils previously under intensive potato production. However, results also revealed that fields under organic certified potato production were retaining the properties of undisturbed reference sites such as pastures and abandoned potato fields under long-term rejuvenation.

Nitrogen and oxygen isotopes in nitrate in the groundwater and surface water discharge from two rural catchments: implications for nitrogen loading to coastal waters

In Prince Edward Island, Canada, widespread intensive potato production has contributed to elevated nitrate concentrations in groundwater and streams, and eutrophic or anoxic conditions occur regularly in several estuarine systems. In this research, the stable isotopes of nitrogen and oxygen in nitrate in intertidal groundwater discharge and stream water were used, in conjunction with water quality and quantity data and land use information, to better understand the characteristics of nitrate delivered to two small estuaries with contrasting land use in their contributory catchments. Most of the water samples collected during the two-year study had isotopic signatures that fell in the range expected for nitrate derived from ammonium-based fertilizers (26.5 % of the samples) or in the overlapping range formed between ammonium-based fertilizers and nitrate derived from soil (64 % of the samples). Overall, isotopic signatures spanned over relatively narrow ranges, and correlations with other water quality parameters, or catchment characteristics, were weak. Nitrate in groundwater discharge and surface water in the Trout River catchment exhibited significantly different isotopic signatures only for the nitrogen isotope, while in the McIntyre Creek catchment groundwater discharge and surface water had similar isotopic signatures. When the isotopic results for the waters from the two catchments were compared, the surface waters were found to be similar, while the isotopic signatures of nitrate in groundwater were distinct only for the nitrogen isotope. Denitrification in the two study catchments was not evident based on the isotopic results for nitrate; however, in the case of the Trout River catchment, where a small freshwater pond exists, an average nitrate load reduction of 14 % was inferred based on a comparison of nitrate loads entering and leaving the pond. Overall, it appears that natural attenuation processes, occurring either in the streams or groundwater flow systems, do not significantly reduce nitrate loading to these estuaries.

Integrating Farming and Páramo Conservation: A Case Study From Colombia

The Colombian environmental policy voted in 1993, which aimed to strengthen the protection of natural resources, particularly biodiversity and water, is totally unfavorable to farming in the strategic páramo ecosystem. However, many rural development practitioners and researchers believe that integrated management of the páramo is possible and that farming activities can be part of the solution along this agriculture–conservation frontier. This issue has become particularly acute on the Rabanal páramo (western cordillera), in Colombia, where the projected expansion of a core protection zone will soon include major areas currently used for agriculture and settlements. Although small-scale farmers have been living there for decades, the environmental authorities are intent on prohibiting farming activities in the entire protection area. A study of local history and aerial photos indicates that this zone has been a dynamic part of local farming systems since at least the 1950s and that the páramo has evolved from a subsistence farming area to a zone that now includes intensive potato production conducted by external entrepreneurs. The presence of these entrepreneurs is mainly due to small-scale farmers' need for a cost-effective solution to maintain the productivity of their pastures. By interviewing participants in the debate, as well as by mapping agricultural land that will soon be included in the protected area, objectives for action were developed that would result in more sustainable farming practices, thus enhancing the conservation of páramo biodiversity and water resources.

Soil and crop responses to long-term potato production at a benchmark site in northwestern New Brunswick

Concerns about deteriorating soil quality led to Agriculture and Agri-Food Canada establishing a network of 23 soil quality monitoring benchmark sites with the objective of providing a baseline data set for assessing change in soil quality and biological productivity of representative Canadian farming systems. A site (22-NB) was established in 1990 in northwestern New Brunswick to monitor changes in Podzolic and Brunisolic soils developed on coarse loamy till on a rolling landscape under intensive potato (Solanum tuberosum L.) production [potato-potato-barley (Hordeum vulgare L.) rotation] that was cultivated along the contour with variable grade diversions and a grassed waterway. Soil samples were collected in 1990 and again in 2000. Field saturated hydraulic conductivity (Kfs) at 10–20, 26–36 and 50–60 cm, earthworm counts and crop yield measurements were conducted annually. 137Cs data were collected in 1990 to estimate soil displacement at the site. Runoff and soil loss between May 01 and Nov. 30 were measured annually. The soil conservation system at site 22-NB has resulted in annual runoff and soil loss of only 9 mm and 311 kg ha-1, respectively. Measured values of 137Cs averaged 2114 Bq m-2 (70% of baseline). Changes in the Ap horizon properties between 1990 and 2000 included significant (P < 0.05) increases in available P (+ 86.7 mg kg-1) and K (+ 13.4 mg kg-1) and significant reductions in available Mg (−45.8 mg kg-1) and SOC (−0.51 g kg-1). The Kfs of 10- to 20-cm, 26- to 36-cm and 50- to 60-cm depths were 1.3, 1.0 and 1.0 cm h-1, respectively. Very few earthworms were present (0.05 worms m-2). The upper terrace was consistently the highest yielding in both potato and barley, while the lowest terrace was consistently the lowest yielding in both crops. Crop yields may have been affected by micro-climate and other soil differences as a result of site position.While the system of contour tillage with variable grade diversions and grassed waterway conserved both soil and water, the potato-potato-grain rotation did not maintain SOC levels or sustain earthworm populations. Associated heavy rates of fertilization also lead to increased levels of soil K and P. Key words: Soil quality, soil organic carbon, hydraulic conductivity, earthworms, runoff, water erosion

Tillage translocation and tillage erosivity by planting, hilling and harvesting operations common to potato production in Atlantic Canada

In Canada, the negative impacts of tillage erosion is a growing concern, especially in regions where highly erosive cropping and tillage systems are practiced on highly erodible, topographically complex landscapes. To date, tillage erosion studies have focused primarily on the movement of soil by primary and secondary tillage operations. However, in potato ( Solanum tuberosum L.) production there is often considerable soil disturbance that occurs during “tertiary” field operations conducted during the growing season. Therefore, the objective of this project was to generate tillage translocation and erosivity values for implements common to planting, hilling and harvesting operations within intensive potato production systems in Atlantic Canada. Our results show that tertiary tillage operations result in significant soil displacement and can be equally as erosive as primary and secondary tillage operations. Both the planting, cultivating and hilling (PCH) sequence and the harvester moved soil extremely large distances (up to 23.6 and 6.0 m, respectively). In fact, the mean translocated distance of the tilled layer ( T L) and the mass of translocated soil ( T M) of the PCH sequence (0.42 m and 115.9 kg m −1, respectively) and the harvester (0.55 m and 71.7 kg m −1, respectively) are larger than those reported previously for primary and secondary tillage operations in New Brunswick. In addition, the net downslope movement of soil for the PCH sequence and the harvester was approximately 36 and 26 kg m −1, respectively, suggesting that both tertiary tillage operations have the potential to be erosive. A direct relationship was observed between both T L and T M and slope gradient for the PCH sequence, but similar relationships were not found for the harvester, even though the harvester moved approximately 30 % more soil downslope than upslope. Linear regression functions were generally improved after including slope curvature in the model, but these results were not always significant. Soil movement by the PCH sequence and harvester were also largely influenced by tillage speed and tillage depth, and future research is needed under controlled conditions to determine whether it is changing topography or the variability in tillage speed and depth across the landscape in response to changing topography that is driving tillage erosion within mechanized agricultural systems. It is clear that tertiary tillage operations must be considered when developing best management practices to improve soil conservation strategies for potato production systems in Canada and worldwide.

Spatial and temporal trends in soil properties and crop yield at a site under intensive up- and down-slope potato production in northwestern New Brunswick

Few quantitative data are available to assess temporal changes in the soil quality of Canada’s agricultural lands. Site 20-NB was established in 1989 to monitor changes in an Orthic Humo-Ferric Podzol developed on coarse loamy till on a rolling landscape under intensive potato production in Atlantic Canada with soil compaction and water erosion the dominant forms of degradation. Sampling of soil and crop parameters was conducted on a 20 × 25 and 25 × 25 m grid basis with 66–90 sample locations. Baseline soil samples were collected in 1989 and the site was re-sampled in 1999. Samples were analysed for pH, available P, K, Ca and Mg, and total soil organic carbon (SOC). Field saturated hydraulic conductivity (Kfs) at 12–22, 27–37 and 50–60 cm, earthworm counts and crop yield measurements were conducted annually. 137Cs data were collected to estimate long-term soil erosion. Annual runoff (May 01 to Nov. 30) and soil loss were measured. Seasonal soil loss between 1989 and 1999 was only 6522 kg ha-1 yr-1 compared with 137Cs-estimated soil displacement of 53 000 kgha-1 yr-1, occurring over the 1960 to 1990 period. In the Ap horizon, soil pH and P increased by 8 and 5%, respectively, while SOC was reduced by 8%. Some changes were identified in the subsoil (50–65 cm) with a 7% increase in pH and a 27% reduction in P. There was little annual variation in the Kfs of the Ap, B and C horizons which ranged from 0.4 to 1.3, from 0.7 to 1.3 and from 0.8 to 2.0 cm h-1. Solum Kfs was significantly less than in an adjacent forested area by 52–80%. Earthworm numbers increased at a rate of 1.5 earthworms m-2 yr-1. Crop yield did not show any temporal trend over the 10-yr period other than that it appeared to be significantly influenced by crop rotation. Potato yield (CV = 12) tended to be less variable than barley (CV = 22) or clover (CV = 21). The benefits of site specific management were found to be questionable. 137Cs-estimated soil loss was most strongly related to SOC (r = −0.66) and average potato yield (r = −0.55). Key words: Soil quality, soil carbon, hydraulic conductivity, earthworms, water erosion

Impact of incorporated hay mulch on selected physical, chemical and microbiological properties of a loam soil in Atlantic Canada after five years of continuous potato production

Maintenance of soil quality and crop productivity is a major concern under intensive potato (Solanum tuberosum L.) production. The effects of four consecutive annual applications of 0.00, 2.25, 4.50 and 9.00 t ha-1 wet hay on growing season soil moisture and thermal regimes, soil quality and yield were evaluated on a loamy Orthic Humo-Ferric Podzol between 1995 and 1999. Hay mulching increased soil moisture at the beginning of the growing season by 6.5 to 12.7%, with increases significant until June 24, September 07 and September 20 for the 2.25, 4.50 and 9.00 t ha-1 treatments, respectively. Growing season soil temperature of the 4.50 and 9.00 t ha-1 treatments were lower than control, but only by −0.2 and −0.8°C, respectively. Hay mulching increased soil organic carbon (SOC) of the plow layer (0–25 cm), which increased biological activity resulting in better soil aggregation with more macropores, faster saturated hydraulic conductivity and reduced bulk density. Soil air CO2 concentration was significantly correlated to SOC content, aggregation, porosity and saturated hydraulic conductivity. Hay mulching at 2.25 and 4.50 t ha-1 increased total potato yield over that of the unmulched control by 11–14%, but was insufficient to maintain soil productivity. Hay mulching at 9.00 t ha-1 may have been excessive in terms of crop yield as it showed no total yield benefits. Key words: Organic carbon, CO2 concentration, aggregates, porosity