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In acidic soils with high phosphorus (P) fixing capacity, P application at levels higher than crop requirements is common in crops with high P demands such as potato (Solanum tuberosum L.), which could lead to eutrophication. Recycled sources of P fertilizer, such as struvite, can be efficient in meeting crop P demands while minimizing P losses. The objective of this study-conducted in four provinces over 3 yr (2016-2018, with 12 sites in total) in Eastern Canada-was to assess potato response to P fertilizer as triple superphosphate (TSP) or a mixture of TSP with struvite. Eight P treatments were applied with five increasing P rates as TSP (0, 26, 52, 79, and 105 kg P ha −1 ) and three treatments as a mixture of TSP and struvite (25, 50, and 75% (w/w) struvite) at a rate of 79 kg P ha −1 . Phosphorus availability indices measured multiple times over the growing season were composed of Mehlich-3 extracted P (P M3 ), soil P adsorbed on anion exchange membranes (P AEMs ), and petiole P-PO 4 (P petiole ) concentrations. There was a potato yield response to P inputs at all sites, with the control treatment showing lower potato yield at all sites. Potato yield, P petiole , P M3 , and P AEMs were comparable between 100% TSP and TSP+struvite at the same rate, except at one site where struvite at a higher proportion depressed yield and was associated with lower P uptake. Overall, the use of struvite could be a sustainable mean to address long-term globally P scarcity.

Potato producers in the Atlantic Canadian provinces of New Brunswick (NB) and Prince Edward Island (PE) rely on the photosystem II-inhibiting herbicide metribuzin for weed management. Recently, potato producers in the region have reported unacceptable common lambsquarters control following an application of metribuzin. Tissue and seed samples were collected from escaped common lambsquarters populations from across the potato producing regions of NB and PE and screened for the Ser264Gly mutation in psbA. Overall, 46% of sampled populations possessed the Ser264Gly mutation across the region. Cross-resistance testing to atrazine, metribuzin and linuron confirmed populations with the Ser264Gly were resistant to triazines and triazinones but remained susceptible to linuron. Dose response analysis determined a moderate level of resistance to metribuzin in common lambsquarters which would not be controlled in producers fields. A field experiment was conducted in Fredericton, NB and Harrington, PE, to determine if currently registered and unregistered products and tank-mixes would control PSII-inhibitor-resistant common lambsquarters in potato. All evaluated products, with the exception of S-metolachlor, provided control equivalent to the weed-free check without compromising potato yield or quality. This study demonstrates that PSII-inhibitor-resistant common lambsquarters are found in Atlantic Canadian potato production systems, but can be controlled with currently registered herbicides and rates with alternative modes of action.

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Organic matter levels combined with drought periods during the growing season have adverse impacts on rain-fed potato production in coarse textured soils of eastern Canada. Using pulp fiber residues (PFR) may build up soil organic matter, improve crops yield and nutrient uptake, and reduce the need for supplemental irrigation in this region. A box experiment with 3 rates of PFR [0, 45, and 90 Mg ha −1 dry mater carbon (C) basis] with or without supplementary drip irrigation was established in a sandy loam soil in New Brunswick, Canada. Red clover, barley, and potato were cultivated as three crops of the rotation in 1999, 2000, and 2001, respectively. The PFR only applied before red clover in fall 1998. Selected soil chemical and physical properties were measured before planting and after harvest. Crops yield and nitrogen (N), phosphorus (P), and potassium (K) accumulation were determined at harvest. Soil organic-C content, bulk density and water holding capacity were improved by PFR application. Red clover and barley biomass production were significantly increased by PFR application. This effect was promoted by supplemental irrigation. Potato tuber yield was not affected by PFR and it was higher in rain-fed compared to supplementary irrigated system. Although, there was some initial evidence of N immobilization but generally PFR application increased N, P, and K bioavailability. This research has demonstrated that PFR can successfully be used as soil amendment in coarse textured soils without any adverse effect.

Soil erosion can be a serious issue in eastern Canada during the three to five weeks it takes for potato (Solanum tuberosum L.) to emerge under the cool, humid climatic conditions with frequent heavy rainfall events. Seeding a fast-growing nurse crop at the same time as the potato crop can hold the soil particles in place, reduce surface crusting, and increase water infiltration. The objective of this study, conducted in Prince Edward Island and in New Brunswick in 2017, was to evaluate the effects of under-seeding potato with barley [Hordeum vulgare L.] and winter rye [Secale cereale L.]) on marketable potato yield, nitrate dynamics during the growing season, and soil moisture content. Nurse crop growth was terminated mechanically (hilling), with a selective herbicide, or a non-selective herbicide. Yield increases ranging from 9% to 91% were observed when nurse crop growth was terminated using a non-selective herbicide at both sites. Inconsistent results were obtained when a mechanical method or a selective herbicide were used with marketable yield reduced at one site and no effect on yield at another site. There was a trend toward higher soil nitrate contents under the control than under the nurse crop treatments even though not consistent across sampling timings. Results demonstrated that there are circumstances under which nurse crops can be successfully integrated into a potato-based system and provides future hypotheses to test. Potential confounding factors that can impact the nurse crop efficiency are discussed.

Reduced within-field potato (Solanum tuberosum L.) yield variation may lead to increased productivity and reduced environmental impact. Using soil samples collected from 88 site-years in commercial fields in New Brunswick, Canada from 2013-2017, this study examined how within-field variation in potato tuber yield was related to soil properties and topographic features. At each of 774 sampling locations, a wide range of soil physical and chemical properties was measured in the lab and topographic features were assessed using a regional digital elevation model. Principal component (PC) analysis identified three PCs, which accounted for 79.1% of the total variation. The PC1 (41.3% of total variance) was dominated by soil texture (i.e., sand, silt) and the quantity and quality of soil organic matter (i.e., soil organic C, particulate organic matter C, and soil C/N ratio). Under rain-fed potato production in New Brunswick, finer soil texture and increased soil organic matter pools are expected to enhance soil water availability and thereby improve yield. The PC2 (22.7% of total variance) was related primarily to parameters associated with soil fertility, and PC3 (15.1% of total variance) was related primarily with concave or convex landforms, which may influence yield through drought or excess water. This study demonstrated the value in using multivariate approaches to identify the factors that control within-field yield variability in the presence of significant regional variation in soil properties and environmental conditions. The findings point to the value of enhancing the quantity and quality of soil organic matter as a key strategy to overcome yield limitations under rain-fed production.