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Average potato yield in Prince Edward Island, Canada, has been stagnant since 2006. Two field studies were conducted on Charlottetown fine sandy loam soil to address this concern. In the first experiment, two alternative crop rotations, grain corn (Zea mays L.)–sorghum sudan grass (Sorghum × drummondii)–potato (C–SS–P) and soybean (Glycine max (L.) Merr.)–mustard (Brassica juncea (L.) Czern.)–potato (Soy–M–P), were compared to a conventional barley (Hordeum jubatum L.) (under seeded with red clover)–red clover (Trifolium pratense L.)–potato (Solanum tuberosum L.) (B–RedCl–P) rotation. This experiment was conducted for two 3‐year cycles comparing the effects of potato rotation, nitrogen fertilizer, and supplemental irrigation. The second experiment evaluated the inclusion of winter cover crops in a 3‐year potato crop rotation. The profitability of potatoes in each rotation was assessed using a stochastic budget of yields and fertilizer and crop prices. The effects of supplemental irrigation were not significant; however, nitrogen fertilization increased potato yields by 48%. Potato yields and net revenues in C–SS–P increased by 10.5% and 32.6% and in Soy–M–P by 6.7% and 20.5%, respectively, compared to potato in B–RedCl–P rotation. The use of winter rape cover increased potato yields by 18.6% compared to a system without winter covers, although some of these increases could be due to the use of sudan grass instead of red clover in B–RedCl–P rotation. It is recommended that potato producers implement the alternative rotation with additional fertilization and winter cover crops to increase yields and profits. Core Ideas: Alternate rotations increased potato yields by 8.6% compared to the standard rotation.Potatoes with corn and sorghum increased profit by 32% compared to the standard rotation.N fertilizers raised potato yields by 48% but supplemental irrigation was insignificant.Winter cover cropping increased potato yields by 18.6% compared to no winter cover. [ABSTRACT FROM AUTHOR]

Strategies to improve sustainability are important in intensively managed potato (Solanum tuberosum L.) systems. This study has assessed rotation systems and N sources to mitigate potato yield and soil organic matter decline in Prince Edward Island (PEI), Canada. Three‐year potato rotation systems were initiated in 2006: continuous potato (CP); potato–barley (Hordeum vulgare L.) underseeded with red clover (Trifolium pratense L.)–red clover (PBR); and potato–barley–sorghum sudan grass ([Sorghum bicolor L.) used as green manure])/winter rape (Brassica napus subsp. rapifera) (PBSW); and potato–barley–canola ([Brassica napus susbsp. napus] used as green manure)/winter rape (PBCW). Three different N sources (mineral N fertilizer, liquid hog manure, and lobster flake) were applied in a split‐plot fashion during the potato phase. Potatoes were grown in 2006, 2009, 2012, and again in 2013 to evaluate residual effects. In 2012, total N or total C in the whole soil, in particulate organic matter or in the slurry fractions were not affected by N sources or rotation systems. The PBSW and PBCW rotations generated significantly higher potato yields in 2009 and 2013, whereas the CP rotation produced significantly lower potato yields in 2 of 4 yr. The addition of lobster flake suppressed yield compared with other N sources in 3 of 4 yr. The PBR rotation, which is common in PEI can increase nitrate losses over winter. Alternatively, the PBSW and PBCW rotations may represent a good substitute to the PBR rotation as they can increase potato yield while minimizing nitrate losses. [ABSTRACT FROM AUTHOR]

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 (R2 = 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. [ABSTRACT FROM AUTHOR]

• N surplus under the conventional PBC rotation was significantly higher than the alternative PSB rotation. • Nitrogen surplus was strongly correlated with leachate N concentration. • Potato and red clover phases produced most of the N leaching during the rotations. • Conventional practice of amending red clover as green manure poses a high risk to the environment. • Potato yield following the PSB rotation was 13.4% higher than the PBC rotation. 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. [ABSTRACT FROM AUTHOR]

To balance economic potato production with environmental risks, it is crucial to understand the effects of forage crops preceding potatoes on soil nitrate (NO 3 -) leaching potential, soil quality and potato yield. This study compared a legume forage (red clover, RC), a grass forage (timothy, T), and a red clover-timothy mixture (M) over two cycles of a 3-yr rotation (barley underseeded with forage-forage-potato) from 2013 to 2018. The forage crops were grown under low input maintenance system receiving only starter N fertilizer during the establishment year. Legume-based forages (i.e., RC and M) had greater dry matter accumulation and lower C:N ratio, and therefore added a greater quantity and quality of organic matter inputs to the soil compared with the grass-based forage (T). This resulted in increased soil N supply to the subsequent potato crop, and improved soil quality as indicated by increased aggregate stability, permanganate oxidizable carbon (POX-C), autoclaved citrate extractable soil protein (ACE), and flush of CO 2 upon rewetting a dried soil for legume- than grass-based forages. Under N limited conditions (i.e., no N fertilizer applied) forage legumes were associated with higher potato yield than forage grass. However, tuber yield was not increased when N fertilizer was applied, a finding attributed to a better synchrony between potato N uptake and soil N supply in the presence of N fertilizer with the forage grass treatment. The legume-based forages improved soil quality, increased soil N supply as well as NO 3 - leaching losses. Results of this study suggest that there may be a trade-off between selecting forage crops to reduce NO 3 - leaching and to enhance soil quality. • Compared forage legumes and grasses on soil quality, N cycling, and potato yield. • Soil quality improved, soil N supply and nitrate leaching increased with legumes. • Higher potato yield with legumes than grasses only under N limiting conditions. • Trends towards higher potato yield with forage grasses with N fertilizer applied. • Trade-offs between improving soil quality and potato yield and reducing N leaching. [ABSTRACT FROM AUTHOR]