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Article

Potato Cropping System and Variety Impacts on Soil Properties, Soilborne Diseases, and Tuber Yield in a Long-Term Field Trial

by
Robert P. Larkin
United States Department of Agriculture, Agricultural Research Service, New England Plant, Soil, and Water Laboratory, Orono, ME 04469, USA
Agronomy 2024, 14(12), 2852; https://doi.org/10.3390/agronomy14122852
Submission received: 30 September 2024 / Revised: 25 November 2024 / Accepted: 28 November 2024 / Published: 28 November 2024
(This article belongs to the Section Soil and Plant Nutrition)
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Abstract

:
Cropping systems incorporating soil health management practices such as longer rotations, cover crops and green manures, and organic amendments have been shown to improve soil and crop health. However, long-term trials are needed to fully assess the impacts and effects of these systems over time. Crop varieties may also respond differently to cropping practices or systems. In field trials originally established in 2004, three different 3-year potato cropping systems focused on management goals of soil conservation (SC), soil improvement (SI), and disease suppression (DS) were evaluated and compared to a standard 2-year rotation (SQ) and a nonrotation control (PP). Results compiled over a 4-year period (2019–2022) using two different potato varieties showed that the SI system (with a history of compost amendments) improved soil properties, including organic matter and nutrient contents, aggregate stability, and microbial activity relative to other systems. The SI system also had higher total and marketable tuber yields (by 22–28%) relative to the standard SQ system. The DS system, which included a disease-suppressive green manure rotation crop, also improved yield (by 12%) and reduced soilborne diseases (black scurf and common scab). Variety Caribou Russet, a newer variety with improved characteristics, produced higher marketable yields and larger tuber size, as well as lower severity of common scab than the standard Russet Burbank variety. These results demonstrate that improved cropping systems can substantially enhance productivity relative to standard cropping systems, as well as provide greater sustainability through long-term improvements in soil health.

1. Introduction

Potato (Solanum tuberosum L.) is a major food crop throughout the world and was recently cited as “the most important lifesaving, staple food and nutritious vegetable in the world” at the International Day of Potato [1]. It is an essential production crop throughout the U.S. and is the top agricultural commodity for the state of Maine [2]. However, intensive agricltural practices adversely affect soil resources and soil health over time, leading to reductions in productivity, sustainability, resilience, and environmental quality [3,4]. Potato production can be particularly detrimental to soil quality due to the extensive tillage and minimal crop residue that are inherent in potato maintenance and harvest operations, as well as the generally short rotations and low crop diversity that are characteristic of cropping systems throughout many potato-growing regions in the U.S. [5,6,7]. Over time, these practices disrupt soil structure and biodiversity and accelerate surface runoff, erosion, and loss of organic matter and soil fertility [4]. These degradations in soil health may also result in greater problems with soilborne diseases such as black scurf (caused by Rhizoctonia solani), common scab (caused by Streptomyces scabies), and Verticillium wilt (caused by Verticillium dahliae) [8,9]. Improving the sustainability and productivity of potato production is necessary to ensure an adequate supply of this crucial food source into the future.
Several soil and crop management practices have been shown to be beneficial in improving soil health and potato crop yield, as well as potentially reducing soilborne diseases, in individual short-term trials. These include using longer rotation periods between potato crops [9,10,11,12], the addition of cover crops and green manures [13,14,15], the use of organic amendments of compost, biochar, or animal manure [16,17,18,19,20], and reductions in tillage [10]. The inclusion of disease-suppressive rotation crops, such as biofumigant Brassica green manures, which break down to produce toxic metabolites that can reduce populations of plant pathogens and alter soil microbial communities, has been shown to reduce soilborne potato diseases [21,22,23]. The incorporation of multiple such agricultural practices into improved potato cropping systems may help enhance the productivity and sustainability of potato production systems. Although the effects of these individual practices have been well-characterized, few studies have examined the combined effects of multiple different practices into integrated cropping systems and their long-term effects on soil properties, soilborne diseases, and crop productivity, which are needed to determine the sustainability and viability of these cropping systems in potato production [7,24,25].
Another factor that can greatly affect productivity under varying conditions is the variety of potato grown [26,27,28]. In addition to the known characteristics of different varieties, there may be differences in their responses to varying soil conditions and cropping systems. For decades, Russet Burbank has been the industry standard processing and fresh market potato variety grown throughout the U.S., and the predominant variety grown in Maine, due to its good processing, culinary, and storage qualities [29]. However, Russet Burbank is a late-maturing variety, requiring up to 140 or more growing days to produce maximum yields [30], yet the cool climate and short growing season in Maine rarely extends beyond 110–120 days, somewhat restricting production. A recently released potato variety developed by the University of Maine, Caribou Russet, has a shorter time to maturity, as well as some other characteristics that may make it more suitable for Maine production conditions [31,32].
In this research, which continues our ongoing studies focused on improving potato cropping systems [33,34,35,36,37], the effects of selected cropping systems incorporating different soil health management practices were assessed on various soil and crop properties over long-term conditions. These potato cropping system field trials were originally established in 2004, with the development of three specific cropping systems addressing the management goals of soil conservation, soil improvement, and disease suppression, which were compared to standard rotation and nonrotation controls [33]. These systems were subsequently monitored over several years, characterizing their effects on soilborne potato diseases and soil microbiology [33,34], soil properties such as organic matter [35], and crop growth and productivity [36]. In 2013, some system modifications were made to improve grower feasibility and implementation, and these trials have continued to provide new information on these effects over time [37]. A new component of the research is the inclusion of the potato variety Caribou Russet (in addition to Russet Burbank) as an additional variety to assess its productivity and responses to the cropping systems. The objectives of the present research were to assess (i) the longer-term effects of cropping systems incorporating soil health management practices such as longer rotations, cover crops and green manures, and organic amendments on soil properties, crop yield, and soilborne diseases, and (ii) the responses of two different potato varieties (one standard and one new variety with some improved characteristics) regarding these properties.

2. Materials and Methods

2.1. Cropping Systems

Cropping system treatments comprised three ‘improved’ systems that incorporated management practices selected to address specific management goals of soil conservation, soil improvement, and disease suppression. They were designated as SC, SI, and DS systems, respectively. These systems were all 3-year rotations with added components specific to their management goal. Also included were two ‘control’ systems, one representing a typical standard rotation currently used in the northeast U.S., designated as the ‘status quo’ or SQ system, and the other a nonrotation control of continuous potato, with potato planted every year, and designated as PP. The original cropping systems, established in 2004, have been fully described previously [33,34]. Some modifications made to the systems in 2013 to provide a better fit for growers and their production practices have also been previously described [37]. An overview of these current cropping systems and their features is provided in Table 1. Briefly, the standard SQ system consists of a 2-year rotation of barley (Hordeum vulgare L.) underseeded with red clover (Trifolium pretense L.) as a cover crop, followed by potato the following year, with regular spring and fall tillage each year. The SC (3-year) system has barley underseeded with ryegrass (Lolium perenne L.) as a cover crop in the first year, with canola (Brassica napus L.) as a cash crop in the second year, followed by potato in the third year. The SI system consists of the same 3-year rotation as SC but features a previous history of compost amendments (composted dairy manure added at 45 Mg ha−1 yr−1 for 7 years, 2004–2010). The DS system incorporates the use of a biofumigant Brassica green manure, additional crop diversity, and different cover crops. The DS (3-year) system also starts with barley underseeded with ryegrass in the first year but is followed by the disease-suppressive Brassica juncea L. ‘Caliente 199′ mustard blend grown as a green manure and a fall cover crop of rapeseed (Brassica napus L. ‘Dwarf Essex’) in the second year, and potato in the third year. Mustard seed was planted (12 kg ha−1) in June, grown for 2 months, then flail-mowed and incorporated into the soil while still fresh and green (green manure), with the rapeseed cover crop planted (12 kg ha−1) two weeks later. The nonrotation PP control had a potato crop planted in the same plots each year (with spring and fall tillage). All systems were monitored under natural rainfed (no irrigation) conditions, as this is consistent with the majority of commercial potato production in Maine and the northeastern US.

2.2. Field Set-Up and Management

Research plots were located at the USDA-ARS New England Plant, Soil and Water Laboratory Field Experimental Site in Presque Isle, ME (46°38′56.4” N, 68°00′28.5” W, 142 m above sea level), and the trial was conducted as a two-factor (cropping system and potato variety) randomized complete block design with 5 replicate blocks. The soil type was a Caribou sandy loam (Fine-loamy, isotic, frigid Typic Haplorthods). Each rotation phase or entry point (representing each possible rotation crop for all years) was included in each block so that each full rotation was represented each year, as previously described [37]. Two different potato varieties, Russet Burbank and Caribou Russet, were used. Russet Burbank has been around for over a hundred years and has been the predominant potato variety grown throughout the U.S. and Canada for decades due to its desirable characteristics, including high yield, high specific gravity, low oil absorption, low sugar content, and excellent taste and storage qualities [38,39]. Caribou Russet is a relatively recent release from the University of Maine that features some improved characteristics, including earlier maturity, fewer defects, good yield, and good disease resistance [31]. For potato planting, each main plot (3.7 × 15.1 m) consisted of four potato rows, with cut seedpieces planted in furrows in each plot, two rows of Russet Burbank (0.9 m centers, 35 cm spacing between plants) and two rows of Caribou Russet (0.9 cm centers, 25 cm spacing). Fertilization was the equivalent of 224 kg ha−1 N and 249 kg ha−1 each of P2O5 and K2O. All potato plots were also sprayed with a pre-emergence herbicide (metribuzin at the rate of 1.0 kg a.i. ha−1) within 2 weeks of planting. In-season cultivation included one pass with a cultivator and one pass with a hiller. Potato plots were also sprayed regularly for control of late blight (at 7–14-day intervals, depending on weather conditions and disease forecasting information) throughout the growing season, with alternating applications of mancozeb and chlorothalonil at recommended rates. All other crops were managed using the recommended production practices for that crop. Potato crop assessments reported here cover the period from 2019 to 2022, constituting data from four consecutive cropping years.
Environmental conditions at the site, including air and soil temperature, relative humidity, and rainfall were monitored throughout each growing season using a Watchdog 2000 Series weather station (Spectrum Technologies, Aurora, IL, USA) outfitted with temperature probes and a tipping bucket rain gauge. For ease of presentation, temperature and rainfall data were summarized as average monthly values for each year of the study (Table 2).

2.3. Soil Properties

Bulk soil samples were collected from each potato plot in the spring of each year just prior to planting and 60 days after planting for soil property assays. Six soil cores (7.5 × 15 cm) randomly collected from throughout each plot were combined into one composite sample per plot, air-dried, sieved, and used for subsequent analyses. An additional separate soil sample (intact soil core) was collected in spring only for aggregate stability analysis. Soil property analyses were conducted by Agvise Laboratories (Northwood, ND, USA) in conjunction with analyses of other potato soils as part of the Potato Soil Health Project (https://potatosoilhealth.cfans.umn.edu/ accessed on 26 August 2024). Chemical analysis included soil K, Ca, Mg, Mn, Fe, Na, and S content and CEC determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES). Biologically related analyses included organic matter content determined by loss on ignition at 360 °C, total carbon by combustion on an Elementar vario MAX CN analyzer, active carbon (POXC—permanganate oxidizable carbon), bioavailable N (ACE protein—autoclave citrate extractable protein), and microbial respiration via Solvita 24 h CO2 burst assay. Soil pH was measured from a 1:1 soil-to-water slurry. Nitrate-N and ammonium-N were determined by cadmium reduction. Available P was determined via the Olsen extraction methods. Water stable aggregate stability was determined at the large macroaggregate (2 mm), macroaggregate (0.25 mm), and microaggregate (0.05 mm) sizes, and the combined macroaggregate percentage was used as a general indicator of aggregate stability. Methodologies for all extractions and analyses were previously described and referenced by Klasek et al. [40].
In the summer of 2022, an additional one-time assay of soil phospholipid fatty acids (PLFA) was conducted using bulk soil samples from each plot. PLFA analysis was conducted by Ward Laboratories (Kearney, NB) to quantify the soil microbial biomass and broadly characterize the microbial groups, such as Gram-positive and Gram-negative bacteria, fungi, actinomycetes, and arbuscular mycorrhizal fungi (AMF), present in the soil using phospholipid biomarkers [41].

2.4. Tuber Yield and Size

In early October of each year, tubers were harvested from the full length of the two rows each of Russet Burbank and Caribou Russet potatoes from each plot. The total weight of the harvested tubers was used to determine the total yield on a Mg ha−1 basis. A representative subset of the harvested tubers, amounting to a total of 20–25 kg per plot, was washed, graded, and sized into 4 categories from small to extra-large (small, <11; medium, 114–22; large, 228–34; and extra-large, >34) [42]. Marketable yield was calculated as the proportion of the total weight of tubers of a size greater than 11 each.

2.5. Disease Assessments

Potato plants were monitored in the field throughout the growing season for signs and symptoms of soilborne diseases, including Rhizoctonia stem and stolon canker, white mold, and Verticillium wilt. A subset of the harvested tubers, consisting of at least 40 tubers of marketable weight, was rated for incidence and severity of soilborne diseases of tubers, including black scurf, common scab, powdery scab, and silver scurf. Disease severity for all tuber diseases was determined as the approximate percent surface coverage of the visible symptoms on each tuber.

2.6. Statistical Analyses

All data analyses were conducted using the Statistical Analysis Systems ver. 9.4 (SAS Institute, Cary, NC, USA). Data from each potato crop year were analyzed using standard analysis of variance (ANOVA) for a randomized complete block design. Data from all years were also combined and analyzed (with year and interactions as additional factors) to evaluate the cumulative and multi-year effects of the cropping systems. Mean separation was accomplished with Fisher’s protected LSD test. Correlation analyses were conducted (using Pearson’s product-moment correlation coefficients) among yield, disease, and soil property parameters to determine the parameters most closely associated with productivity. Significance was evaluated at p < 0.05 for all tests.

3. Results

3.1. Soil Properties

Soil’s physical and chemical properties were significantly affected by the different cropping systems, but not by the potato variety grown. Differences were generally consistent from year to year, so results are shown as cropping system averages over the 4-year period (2019–2022). Soil pH was highest in the Soil Conserving (SC) system and significantly higher than all other systems except Soil Improving (SI), whereas soil pH was lowest in continuous potato (PP) and significantly lower than all other systems (Table 3). Soil organic matter (OM) was significantly higher in SI than in all other systems throughout the study, averaging 38–51% higher than in the standard rotation (SQ) and PP. Organic matter content was significantly lower for PP than all other systems, whereas OM contents for the remaining systems were intermediate (Table 3). Water-stable aggregate stability, represented by macroaggregates greater than 0.25 mm, was highest in the SI and SC systems and lowest in PP (Table 3).
Soil concentrations of macro-nutrient elements also varied among cropping systems, with significantly higher levels of NO3-N and somewhat higher levels of NH4-N (significantly higher than SC) observed in SQ soil. Concentrations of P and K tended to be highest in PP and were notably lower in the DS and SC systems (Table 3). The soil content of the cations Ca and Mg, as well as cation exchange capacity (CEC), was higher in SI than in all other systems, whereas Mg content was lowest in PP, and Ca tended to be lower in PP and DS (Table 3).
Properties associated with soil microbiology were also affected by the cropping system. For all indicators measured, including total organic carbon (TOC), active C, ACE protein, and CO2 respiration, the SI system maintained higher levels than all other cropping systems, whereas PP resulted in lower levels than all other systems, with SI averaging values 40–50% higher than PP and 14–36% higher than SQ (Table 4). In addition, soil PLFA analysis of samples from 2022 provided indicators of microbial community size and abundance. Total microbial biomass and the relative proportion of fungi based on PLFA analysis were highest in the SI and SQ systems and lowest in PP, with SI averaging a 77% and 125% increase, respectively, relative to PP (Table 5). Continuous potato (PP) also resulted in lower values of most microbial parameters, including functional group diversity index and the relative proportions of total fungi, actinomycetes, Gram-positive and Gram-negative bacteria, actinomycetes, AM fungi, saprophytes, and the ratio of fungi to bacteria, but showed the highest levels of undifferentiated microorganisms and the ratio of Gram-positive to Gram-negative bacteria (Table 5). SI also showed generally higher proportions of Gram-negative bacteria, AM fungi, and a higher ratio of fungi to bacteria, as well as a lower ratio of Gram-positive to Gram-negative bacteria than other systems, which can be used as indicators of soil health.

3.2. Tuber Yield and Size

Overall, potato tuber yields were greatly affected by weather and environmental conditions that varied each year. Low summer rainfall in 2019 and particularly hot, dry conditions in spring and late summer of 2020 (with monthly rainfall deficits of several cm) (Table 2) resulted in much lower than average potato yields. However, abundant rainfall throughout the summer of 2021 led to much higher, above-average yields (with marketable yields averaging more than double those observed in 2020) (Table 6). In 2022, a wet spring caused wet fields and planting delays, but adequate rain through the summer resulted in fairly average yields. Both the factors of cropping system and potato variety significantly affected tuber yields in all years, but there was no significant interaction between the two factors.
SI system plots, which have a history of compost amendments, produced the numerically highest total and marketable (tubers > 114 g) yields and significantly greater yields than PP in all four years of the study (2019–2022), with increases in total yield from 19 to 38% and increases in marketable yield from 38 to 75% (Table 6). SI also increased total and marketable yields relative to the standard SQ system in three of the four years (all but 2019), with increases ranging from 14 to 78%. The Disease-Suppressive (DS) system also resulted in total and marketable yields significantly greater than PP in 2020 through 2022 and greater than SQ in 2020 and 2022 (by 11–63%) (Table 6). The PP nonrotation control consistently resulted in yields lower than most other systems. When data were combined over all four years, SI demonstrated significantly higher total and marketable yields than all other systems, and DS produced higher yields than SQ and PP (Figure 1). All cropping systems (including SQ) resulted in higher marketable yields than PP. Over the 4-year period, SI averaged total yields that were 22 and 28% greater than SQ and PP, respectively, and marketable yields that were 28 and 50% greater, with DS yields averaging 11 and 16% greater than SQ and 12 and 32% greater than PP, for total and marketable yields, respectively. SC also increased yield overall compared to SQ and PP for total yields and PP only for marketable yield by 6–22% (Figure 1).
Potato variety also affected yield, with Caribou Russet (CR) producing significantly higher marketable yields than Russet Burbank (RB) in all four years, ranging from 20 to 47% greater, and greater total yields in 2019 and 2022 (by 8–15%) (Table 6). Averaged over all four years, CR produced significantly higher yields than Russet Burbank, with total and marketable yields averaging 5 and 25% greater, respectively (Figure 2).
Tuber size distribution was closely related to the differences in yield observed, again, with both cropping system and potato variety affecting size distribution, but with no significant interaction between the two factors. Variable environmental conditions across years also affected size distributions (with low rainfall years resulting in smaller tubers), but cropping system and potato variety effects were consistent over all the years. Potato variety had the greatest effect on size distribution, with Caribou Russet producing greater proportions of tubers in the medium (115–22), large (228–34), and extra-large (>34) size classes than Russet Burbank, resulting in an overall higher percentage of marketable tubers (>11) (74.8 vs. 62.6%) and 40% more large and extra-large tubers (31.6 vs. 22.6%) (Figure 3). Consequently, Russet Burbank resulted in a higher percentage of small or under-size tubers (36.9 vs. 23.7%) and more misshapen tubers (13.6 vs. 2.1%) than Caribou Russet.
For cropping systems, SI resulted in the overall highest percentage of marketable tubers (74.8%), which was significantly greater than that of SC, SQ, and PP systems, whereas PP resulted in the lowest of all systems (62.6% vs. 70.0 to 74.8%). Correspondingly, PP showed higher percentages of small/under-sized tubers (37.4%) than all other systems (25.2 to 30.8%), and SI, followed by DS and SQ (28.7 to 30.9%), had higher percentages of large and extra-large sized tubers relative to PP (20.8%) (Figure 4). SQ and PP also showed higher percentages of misshapen tubers (9.4–9.7%) than SC and SI (6.1–6.7%).

3.3. Disease Assessments

An assessment of Verticillium wilt pathogen in the soil from spring soil samples indicated that PP plots had higher counts of Verticillium propagules than all other systems (p < 0.001, LSD 5.4), averaging 24.0 propagules per g of soil (ppg) vs. 10.4 ppg for SQ, and 5.2–6.8 ppg for the other systems. However, no symptoms of Verticillium wilt were observed either in the field or on tubers, and no other significant above-ground plant or foliar diseases were noted throughout the growing seasons. The primary tuber diseases observed each year were black scurf, caused by Rhzoctonia solani, and common scab, caused by Streptomyces scabies. Both factors, cropping system and potato variety, affected the incidence and severity of both diseases in most years, but results were not always consistent across years.
The nonrotation control (PP) resulted in the highest incidence and severity of black scurf in most years, with a high of 23% incidence in 2019, but SC showed higher incidence and comparable severity in 2021, and SQ showed comparable severity in 2022 (Table 7). All of the rotation cropping systems showed some degree of reduction of black scurf relative to PP. DS resulted in the overall lowest incidence and severity of black scurf in most years (other than 2019, when DS did not reduce disease), with reductions in incidence and severity of 41–72% and 17–24%, respectively. The SI and SC systems also reduced disease in some years relative to PP and/or SQ, ranging from 13 to 71% (Table 7). When data were combined over all four years, all cropping systems reduced the incidence and severity of black scurf relative to PP (incidence by 31–51% and severity by 12–18%), and DS also reduced severity relative to SQ (Figure 5A).
Potato variety affected the incidence and severity of black scurf differently by year, with CR demonstrating lower incidence than RB in 2019 and 2020 (by 25–57%) but higher incidence in 2022 (by 32%) and lower severity in 2019 (by 25%) but higher severity in 2022 (by 17%), and comparable disease levels in 2021 (Table 7). When compared over all four years, CR had a lower incidence of black scurf (10.1 vs. 12.1%, p = 0.001) than RB but with no overall difference in severity (0.88–0.90, p = 0.29).
Tuber disease levels of common scab also varied from year to year, with higher incidence and severity of common scab observed in the wetter years (2021 and 2022) than in the drier years. DS significantly reduced the incidence and severity of common scab relative to PP in all four years, with reductions of 5–35%, and relative to SQ in three of the four years (all but 2021), with reductions of 12–35% (Table 8). SI and SC also reduced the incidence and severity of common scab compared to PP and/or SQ in some years, but not as consistently as DS. When data were combined over all four years, all 3-year cropping systems reduced scab severity compared to PP and SQ, and DS also significantly reduced the incidence and severity of scab severity compared to PP and SQ, with reductions of 6–18% (Figure 5B).
The effects of potato variety on common scab were inconsistent, with Caribou Russet showing lower incidence and severity of scab than Russet Burbank in 2019, and lower severity of scab in 2020 and 2021, but higher incidence in 2020 and higher incidence and severity in 2022 (Table 8). When data were combined over all the years, CR averaged lower scab severity than RB overall (2.42 vs. 3.23%, p < 0.001), but there was no overall difference in scab incidence between the two varieties (61.9 vs. 62.8, p = 0.19).

3.4. Correlation Analysis

Several soil properties were significantly correlated with total and marketable yield in multiple individual years and over all the four years combined. Total and marketable yield were highly correlated (p < 0.01) with Ca and Mg concentration, and CO2 respiration in all four years and overall (r = 0.30–0.80), and OM content, ACE protein, and TOC were significantly correlated with total and marketable yield in three of the four years (excluding 2019) and over all the years (r = 0.15–0.56). The only year when yield was correlated with a disease parameter was 2010, with the incidence and severity of black scurf being negatively correlated with total and marketable yield (r = −0.34 to −0.45, p < 0.01). Interestingly, although not correlated with disease in any individual year, the incidence and severity of common scab, as well as CEC and NH4, were correlated with total and marketable yield over all four years combined. It seemed to be related to the differences caused by the wetter vs. drier years, which resulted in increases in common scab and yield.

4. Discussion

In this research, potentially beneficial soil and crop management practices were incorporated into standard production practices to develop improved potato cropping systems. Three systems with incremental changes were designed to focus on management goals of soil conservation (SC), soil improvement (SI), and disease suppression (DS) and were compared with standard rotation and nonrotation controls. These systems have been monitored for their effects on various soil properties, crop productivity, and potato diseases for many years. In all three systems, rotation length was increased from two to three years relative to the standard rotation, and in the current systems, all start with the same first-year crop of a small grain (barley) underseeded with a cover crop (ryegrass) that has previously proven to improve yield and reduce disease relative to the standard rotation [8]. The SC system added a revenue-producing rotation crop (canola) in the second year as well as an additional cover crop (winter rye), providing crop diversity, better soil coverage, and a reduction in tillage relative to the standard rotation. The SI system built upon SC with the addition of organic amendments (compost), providing substantial improvements in organic matter and its many related properties. The DS system replaced the second-year crop with a biofumigant green manure (mustard) and Brassica cover crop (rapeseed) to enhance the suppression of soilborne diseases through biofumigation and Brassica effects on soil microbiology. Previous reports have documented the effects of these systems over time.
In the current research, these systems were assessed for their longer-term effects on potato yield, disease development, and soil properties over four recent potato cropping seasons (2019–2022). This represents nearly two decades since the start of the trials and one decade since some modifications were made to the systems. An additional new component is the comparison between two different potato varieties, one old standard and one new variety, with characteristics potentially better suited to this environment regarding yield and soilborne diseases. Combined results across all four cropping seasons, representing different environmental conditions, confirmed the importance of the cropping system, as virtually all of the crop and soil characteristics measured were significantly affected by the cropping system. The soil-improving (SI) system, with its previous history of compost amendments, produced the greatest overall effects and improvements in numerous crop production and soil health parameters.
At this stage, marketable tuber yields in all crop rotations were significantly greater than those with no rotation (PP), and total yield was significantly greater for all of the 3-year systems (SI, SC, and DS) than in the 2-year standard (SQ) and PP systems. Overall, total and marketable tuber yields were significantly greater in the SI system than all others, averaging 22 to 51% greater than SQ and PP systems over all the years. The largest yield differences among cropping systems occurred in the driest year, 2020, where yields were quite low overall, but SI resulted in marketable yields that were 75–78% greater than both SQ and PP systems. Varying weather conditions and rainfall, in particular, greatly affected potato yields, with two dry years (2019 and 2020) followed by two wet or adequate moisture years (2021 and 2022), resulting in large differences across years and illustrating the critical nature and relationship between soil water availability and potato yield [43,44]. However, the SI system was able to maintain generally higher yields throughout all years. The SI system also accounted for the highest percentage of marketable tubers, large and extra-large tubers, as well as fewer small or under-sized tubers than SC, SQ, and PP. Such SI effects on yield are associated with the many changes observed due to this system, including higher OM content, higher microbial activity, and improved nutritional qualities. The importance of water availability and soil structure as affected by OM content and related properties have been well-documented as major factors in yield and productivity [44,45,46,47].
Previous reports on these systems have also demonstrated other significant effects of SI on soil properties associated with soil health, such as lower bulk density, increased aggregate stability, microbial biomass and activity, as well as increased active C and total and particulate organic matter C and N compared to the other systems [33,34,36]. These effects are indicative of the major role of organic amendments, and particularly compost, in improving soil health properties, which have been documented in numerous other studies [17,48,49,50,51]. Organic matter amendments are known to improve soil structural stability through increases in aggregate stability and improvements in aeration, porosity, bulk density, and water movement [52,53,54].
It is notable that these effects are still observed and associated with the compost amendments in the current SI system, as all compost amendments were made between 2004 and 2010, with no further compost applied. Thus, for the past 10+ years, the SI and SC systems were exactly the same (the only difference being those previous compost amendments), yet SI has maintained higher OM content, higher microbial biomass and activity, and higher yields than other systems. This suggests that as long as sufficiently high OM levels are maintained, soil health benefits will continue to be realized, even without additional compost amendments. However, when compared with previous results, SI effects, including OM content and resulting yield effects, have been diminishing over the years since compost amendments ceased. For example, at the conclusion of compost amendments in SI (2011), OM content was above 7%, and the total yield average was 42% higher than that of PP [34]. In the period from 2015 to 2018, OM content averaged 5.6% and total yield was 36% greater than PP [37], and in the current study, OM content averaged 5.3% and SI averaged total yields 28% greater than PP. Overall, OM content decreased sharply in the first few years after compost amendments ceased but then leveled off at around 5.6% and then decreased much slower after that. Other management practices included in the SI system, such as the use of desirable cover crops and crop diversity, likely helped maintain OM levels above those of the other systems for many years. Due to the fact that OM content and yield levels are slowly declining in SI over time, current plans are to re-apply compost in subsequent seasons to increase OM content again, which should potentially also increase yields to previous levels. It should be noted that the full effects of the SI system result from the combination of multiple practices, which include the use of cover crops and a longer rotation period in addition to the organic amendments, as observed in other studies [16,55].
Overall higher tuber yields (than SQ and PP) were also observed in the DS system, in addition to reductions in the incidence and severity of black scurf and common scab, whereas relatively minor effects were observed on other soil properties [35,37]. Primary effects of Brassica green manures similar to that included in the DS system consist of reductions in fungal plant pathogens, weeds, and nematodes through biofumigation, as well as other changes in soil microbiology, resulting in suppression of soilborne diseases [56,57,58]. Thus, the disease-suppressive attributes of the Brassica green manure rotation and cover crops and their impacts on soil microbiology have continued to provide at least some level of reduction of soilborne diseases throughout many years and rotation cycles. Although the populations of soilborne pathogens were not assessed in this study, soilborne diseases have been consistently reduced in DS relative to the other systems. Additional analyses of specific changes in soil microbiome characteristics are currently being conducted. In recent meta-analyses of hundreds of studies, green manures and biofumigation in many different cropping systems consistently increased soil OM content, nutrient concentrations, microbial biomass, enzyme activity, and crop yields and reduced pest abundance and disease incidences [59,60]. Additional studies throughout Maine and Canada have documented reductions in soilborne diseases and improved potato yield with Brassica green manures [21,61,62,63,64]. However, unlike in previous years, in the present study, disease reduction provided by the DS system was not significantly greater than that provided by the other 3-year rotations in most years or overall, indicating either diminishing effects by DS or improved suppression provided by SI and SC.
Both SI and SC showed improvements in the reduction of soilborne diseases relative to previous years of this study [33,34,37]. This may represent biological properties that developed over time to reduce disease severity, potentially due to changes in soil microbial characteristics, general suppression, or other biological mechanisms, as cover crops and organic amendments have been associated with changes in soil microbiology and reductions in soil-borne diseases [48,64,65], and the development of disease-suppressive soils [66,67]. Recent on-farm studies demonstrated that 2 to 5 years of cover crop usage produced small positive impacts on multiple soil health properties, such as OM content, aggregate stability, active C, and microbial activity, but it was also noted that additional years were needed for more substantial changes to result [68]. Other studies also indicated that substantial effects due solely to cover crops and/or rotation length alone may take several years to develop [10,69,70]. In the current study, these effects developed slowly over time, further indicating the importance of long-term assessments of cropping systems.
Other results observed at this stage of the study that differ from earlier observations include greater differences in soil properties between the nonrotation (PP) system and the 3-year cropping systems, such as lower pH, OM content, C forms, and microbial activity than other systems, which indicates further decline and degradation of soil health through nonrotation monocropping [34,37,71,72,73]. However, some nutrient contents, including soil P and K, were higher in PP than all other systems. This is likely due to the buildup of these elements in soil due to the yearly application of high levels of NPK fertilizer consistent with potato production, whereas other systems have these fertilizers added only every two or three years. Despite these high nutrient levels, yields are lower than in other systems, and these higher residual nutrient levels will be more susceptible to leaching and run-off to surrounding areas [74,75].
The introduction of a second potato variety represents a new component of this study and provides a means to assess whether different varieties may respond differently to the cropping systems, as well as assess a variety that may be better suited to the production system in Maine. Although the variety Russet Burbank has been the industry standard and predominant variety grown in Maine and throughout the U.S. for many years, with its late maturity, it may not be the best fit for the short growing season in Maine. Caribou Russet is a dual-purpose (processing and fresh market), russet-skinned variety with high yields, mid-season maturity, and moderate resistance to common scab and Verticillium wilt developed by The University of Maine and released in 2016 [31,32]. In the current research, potato variety did not affect most soil properties but did affect tuber yield and soilborne diseases to some degree. However, there was no indication that the potato varieties responded differently to the cropping systems, as there was no significant interaction between the cropping system and variety factors for any of the parameters. Thus, cropping system had the same overall effects regardless of the variety grown, and vice versa.
Although yields varied by year and were not significantly different every year (for total yield), over all the years, Caribou Russet resulted in greater total and marketable tuber yield than Russet Burbank (by 5–26%). Interestingly, total yield was not significantly different between the two varieties in both the driest and wettest years (whereas marketable yield was greater for Caribou Russet every year). Caribou Russet generally produced larger tubers and a higher percentage of marketable tubers every year. The larger tubers and overall increased yields are presumably due to the earlier maturity of Caribou Russet, where more tubers are able to reach full size within the limitations of the Maine growing season. In this study, the time from planting to pre-harvest vine-kill was 105–120 days, which is less than optimal for Russet Burbank but prime maturity for Caribou Russet. It was not possible to go beyond this length due to the encroachment of cold fall temperatures, which trigger the natural senescence of the potato plants. Caribou Russet also showed some capabilities for lower soilborne tuber diseases than RB, with overall reductions in the incidence of black scurf and severity of common scab; however, results were not consistent each year. As a result, additional research is needed to confirm any variety effects and other factors affecting disease reduction. But overall, Caribou Russet was found to be a high-quality replacement for Russet Burbank, particularly in the northeast and shorter season potato-growing regions, demonstrating higher yields, larger tuber sizes, and better quality (fewer misshapen tubers).

5. Conclusions

The soil improvement (SI) cropping system, which is characterized by a previous history of compost amendments, the use of cover crops, and an extended (3-year) rotation period, has continued to substantially improve potato tuber yield and numerous soil health parameters, and reduce soilborne diseases, relative to a standard (2-year) rotation in a long-term (nearly 20 years) trial. Significant effects have persisted for many years after compost amendments have ceased and indicate that soil improvements (and higher yields) can be maintained indefinitely with the appropriate cropping system. Another 3-year cropping system, disease suppression (DS), which includes a Brassica green manure rotation crop and cover crops, has reduced multiple tuber diseases and improved yield relative to a standard rotation throughout this long-term trial. Additionally, the potato variety Caribou Russet was shown to provide higher yields and larger tuber sizes than the industry standard variety Russet Burbank under varying environmental conditions and multiple seasons. Caribou Russet has earlier maturity and favorable characteristics that may be more suitable for use in the northeast and other short-growing-season regions. The success of these cropping systems in improving soil health and maintaining high yields and low disease for extended periods and under varying environmental conditions demonstrates that the incorporation of soil health management practices such as longer rotations, cover crops and green manure, and organic amendments, into improved cropping systems can substantially enhance productivity relative to standard cropping systems currently used throughout the northeastern U.S., as well as provide greater sustainability through improvements in soil health.

Funding

This research received no external funding.

Data Availability Statement

The data presented in this study are available upon request from the corresponding author.

Acknowledgments

Numerous people have contributed to this research in various ways over the many years of these studies; most importantly, we thank D. Torrey for managing and maintaining the field site, J. Hunt, A. Introne, E. Champaco, and D. Cowperthwaite for additional technical support, as well as research colleagues J. Hao, C. Rosen, and L. Kinkel, as leaders of the Potato Soil Health Project, and past research colleagues W. Honeycutt, T. Griffin, M. Olanya, and Z. He, who were instrumental in establishing and maintaining the study through the early years of the trial.

Conflicts of Interest

Mention of trade names, proprietary products, or specific equipment does not constitute a guarantee or warranty by the U.S. Department of Agriculture and does not imply approval to the exclusion of other products that may be suitable. The authors declare no conflicts of interest.

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Figure 1. Effects of cropping system (SI—Soil Improving, DS—Disease Suppressive, SC—Soil Conserving, SQ—standard rotation, and PP—nonrotation control) on (A) total and (B) marketable tuber yields over a 4-year period (2019–2022). Bars topped by the same letter are not significantly different from each other based on ANOVA and Fisher’s protected LSD test (p < 0.05). × indicates mean value.
Figure 1. Effects of cropping system (SI—Soil Improving, DS—Disease Suppressive, SC—Soil Conserving, SQ—standard rotation, and PP—nonrotation control) on (A) total and (B) marketable tuber yields over a 4-year period (2019–2022). Bars topped by the same letter are not significantly different from each other based on ANOVA and Fisher’s protected LSD test (p < 0.05). × indicates mean value.
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Figure 2. Effect of potato variety on total and marketable tuber yield over a 4-year period (2019–2022). Bars topped by the same letter are not significantly different from each other based on ANOVA and Fisher’s protected LSD test (p < 0.05). × indicates mean value.
Figure 2. Effect of potato variety on total and marketable tuber yield over a 4-year period (2019–2022). Bars topped by the same letter are not significantly different from each other based on ANOVA and Fisher’s protected LSD test (p < 0.05). × indicates mean value.
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Figure 3. Effect of potato variety on tuber size class distribution (small, medium, large, and extra large) from combined data over four cropping seasons (2019–2022).
Figure 3. Effect of potato variety on tuber size class distribution (small, medium, large, and extra large) from combined data over four cropping seasons (2019–2022).
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Figure 4. Effect of cropping system (SI—Soil Improving, DS—Disease Suppressive, SC—Soil Conserving, SQ—Standard Rotation, and PP—nonrotation control) on tuber size class distribution combined data over four cropping seasons (2019–2022).
Figure 4. Effect of cropping system (SI—Soil Improving, DS—Disease Suppressive, SC—Soil Conserving, SQ—Standard Rotation, and PP—nonrotation control) on tuber size class distribution combined data over four cropping seasons (2019–2022).
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Figure 5. Effects of cropping system (SQ—standard rotation, SC—Soil Conserving, SI—Soil Improving, DS—Disease Suppressive, and PP—nonrotation control) on the severity (represented by percent surface coverage) of soilborne tuber diseases (A) black scurf and (B) common scab over four cropping seasons (2019–2022). Bars topped by the same are not significantly different from each other based on ANOVA and Fisher’s protected LSD test (p < 0.05). × indicates mean value.
Figure 5. Effects of cropping system (SQ—standard rotation, SC—Soil Conserving, SI—Soil Improving, DS—Disease Suppressive, and PP—nonrotation control) on the severity (represented by percent surface coverage) of soilborne tuber diseases (A) black scurf and (B) common scab over four cropping seasons (2019–2022). Bars topped by the same are not significantly different from each other based on ANOVA and Fisher’s protected LSD test (p < 0.05). × indicates mean value.
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Table 1. Names, descriptions, and features of the cropping systems used in these trials.
Table 1. Names, descriptions, and features of the cropping systems used in these trials.
Cropping System Parameters
NameAbbreviationLengthRotation SequenceFeatures
Status Quo SQ2 yearsBarley/Red clover—PotatoStandard practice rotation (Control)
Soil ConservingSC3 yearsBarley/Ryegrass—Canola/winter rye cover
(Limited tillage, straw mulch cover)		Increased length (3 years), cover crops
Soil ImprovingSI3 yearsBarley/Ryegrass—Canola/winter rye coverHistory of compost amendment (2004–2010)
Disease SuppressiveDS3 yearsBarley/Ryegrass—Mustard GM/rapeseed cover
Sudangrass GM/Rye cover		Biofumigant Brassica green manure crop
Continuous PotatoPP1 yearPotato—PotatoNonrotation (negative) control
Table 2. Average daily temperature and total rainfall for the months of May through September at the Presque Isle, ME research site for 2019 to 2022 compared with the long-term (30-year) average (LTA) conditions.
Table 2. Average daily temperature and total rainfall for the months of May through September at the Presque Isle, ME research site for 2019 to 2022 compared with the long-term (30-year) average (LTA) conditions.
Average Daily Temperature (°C)Rainfall (cm)
Treatment2019202020212022LTA2019202020212022LTA
May9.911.312.012.311.47.39.210.47.98.7
June16.218.118.615.016.412.64.07.514.68.6
July20.921.019.020.119.05.58.914.113.09.4
August18.418.620.719.818.24.62.57.510.910.0
September12.613.814.815.013.212.21.119.08.58.7
Season avg15.616.617.016.415.642.225.758.554.945.5
Table 3. Selected soil physical and chemical properties and nutrient concentrations as affected by the cropping system as measured each spring and averaged over four cropping years (2019–2022).
Table 3. Selected soil physical and chemical properties and nutrient concentrations as affected by the cropping system as measured each spring and averaged over four cropping years (2019–2022).
System ypHOM AggstabNO3NH4PKCaMgCEC
(%)(%)mg/kg
SI5.74 ab5.32 a64.7 a12.9 b4.7 ab101.0 b213.7 b1058 a191.6 a10.2 a
DS5.70 bc4.10 b62.9 ab9.8 c4.5 ab95.3 d187.5 c856 c166.9 c8.9 c
SC5.78 a3.92 b64.0 a10.2 c4.3 b94.6 d185.1 c880 bc175.1 b8.9 c
SQ5.63 c3.84 b61.1 bc15.9 a5.1 a108.8 b211.4 b899 b145.9 d9.4 b
PP5.48 d3.52 c59.1 c9.2 c4.5 ab127.3 a253.9 a860 c127.2 e9.5 b
LSD0.070.142.21.40.74.114.1357.50.4
y Cropping systems, SI = Soil Improving, SC = Soil Conserving, DS = Disease Suppressive, SQ = Status Quo, PP = Continuous potato systems, OM = Organic matter content, Aggstab = water-stable aggregate stability >0.2 m, CEC = Cation exchange capacity. Values within columns followed by the same letter are not significantly different from each other based on ANOVA and Fisher’s protected LSD test (p < 0.05).
Table 4. Soil microbiological properties as affected by cropping system and as measured by total organic C (TOC), Active C, ACE Protein test, and CO2 respiration (Solvita CO2 burst test).
Table 4. Soil microbiological properties as affected by cropping system and as measured by total organic C (TOC), Active C, ACE Protein test, and CO2 respiration (Solvita CO2 burst test).
Cropping System yTOCActive C ACE CO2 Resp.
(%)(mg/kg soil)Protein(mg/kg soil)
SI3.01 a685.0 a14.4 a161.2 a
DS2.25 b505.7 b11.0 b132.5 c
SC2.21 b517.2 b11.0 b132.1 c
SQ2.22 b521.1 b10.8 b141.2 b
PP2.07 c452.2 c10.2 c111.9 d
LSD0.0825.20.46.9
y Cropping systems, SI = Soil Improving, SC = Soil Conserving, DS = Disease Suppressive, SQ = Status Quo, PP = Continuous potato systems. Values within columns followed by the same letter are not significantly different from each other based on ANOVA and Fisher’s protected LSD test (p < 0.05).
Table 5. Total microbial biomass and relative proportions of different microbial groups as affected by cropping system based on soil PLFA analyses taken from soil samples collected in summer 2022.
Table 5. Total microbial biomass and relative proportions of different microbial groups as affected by cropping system based on soil PLFA analyses taken from soil samples collected in summer 2022.
Sys yBiomassDiver.BactFungiActinG-G+AMFSapUndFBRG+/G−
ng/gIndex% RatioRatio
SI1362 a1.43 a41.8 a8.1 a9.6 a13.2 a28.6 a2.68 a5.39 ab50.1 b0.193 ab2.20 b
DS 967 bc1.38 a37.4 a6.4 ab8.6 a9.8 ab27.6 a1.59 abc 4.64 abc56.1 b 0.166 abc3.22 ab
SC1153 ab1.37 a37.3 a5.2 bc8.7 a9.1 bc27.0 a1.72 bc3.62 bc 57.2 ab0.139 bc3.18 ab
SQ1335 a1.47 a39.2 a8.4 a8.3 a12.2 ab28.3 a2.12 ab6.30 a52.0 b0.213 a2.28 b
PP769 c1.24 b31.9 b3.6 c6.5 b7.0 c24.9 b0.83 c2.78 c64.5 a0.110 c3.77 a
LSD2970.115.22.71.43.81.90.981.907.60.0581.15
y Cropping systems, SI = Soil Improving, SC = Soil Conserving, DS = Disease Suppressive, SQ = Status Quo, PP = Continuous potato systems. Values within columns followed by the same letter are not significantly different from each other based on ANOVA and Fisher’s protected LSD test (p < 0.05).
Table 6. Effects of different cropping systems and potato varieties on total tuber yield and marketable yield each year from 2019 to 2022.
Table 6. Effects of different cropping systems and potato varieties on total tuber yield and marketable yield each year from 2019 to 2022.
Total Tuber Yield (Mg/ha)Marketable Yield (Mg/ha)
Factor y20192020202120222019202020212022
System
SI25.1 a24.1 a41.8 a36.4 a17.7 a16.7 a34.1 a29.4 a
DS21.4 bc22.7 ab37.9 b33.9 ab13.2 c15.3 ab30.6 a26.8 ab
SC21.9 bc19.9 bc39.0 ab31.1 bc14.3 bc12.1 bc30.9 a23.4 bc
SQ23.5 ab18.2 c35.9 b 27.0 d16.8 ab9.4 c29.9 a20.4 c
PP20.2 c17.5 c31.9 c30.6 cd12.8 c 9.5 c23.0 b20.3 c
LSD2.73.13.13.23.13.74.03.9
Variety
CR24.0 a20.2 a38.0 a33.0 a17.8 a13.9 a32.7 a26.8 a
RB20.8 b20.7 a36.8 a30.6 b12.1 b11.3 b27.2 b21.4 b
LSD1.71.91.92.31.92.32.52.5
y Cropping systems, SI = Soil Improving, SC = Soil Conserving, DS = Disease Suppressive, SQ = Status Quo, PP = Continuous potato systems. Potato varieties: CR = Caribou Russet, RB = Russet Burbank. Values within columns for each factor followed by the same letter are not significantly different from each other based on ANOVA and Fisher’s protected LSD test (p < 0.05).
Table 7. Effects of different cropping systems and potato varieties on development of black scurf (caused by Rhizoctonia solani) on potato tubers over four field seasons (2019–2022).
Table 7. Effects of different cropping systems and potato varieties on development of black scurf (caused by Rhizoctonia solani) on potato tubers over four field seasons (2019–2022).
Incidence (% Infected Tubers)Severity (% Surface Coverage)
Factor y20192020202120222019202020212022
System
SI15.9 bc5.1 ab16.1 b6.7 b0.80 b0.81 bc0.99 b0.88 b
DS19.4 ab4.2 b7.3 d7.6 b0.87 ab0.76 c0.86 c0.84 b
SC13.9 bc4.4 b22.6 a5.6 b0.81 b0.76 c1.11 a0.84 b
SQ11.1 c4.5 b10.1 cd6.1 b0.76 b0.88 b0.91 c0.98 a
PP23.0 a15.1 a14.5 bc11.3 a0.99 a 1.00 a1.05 a1.01 a
LSD5.74.45.33.40.120.100.080.06
Variety
CR14.7 b4.4 b15.6 a8.9 a0.74 b0.85 a0.98 a0.98 a
RB19.6 a10.1 a12.7 a6.0 b0.99 a0.84 a0.98 a0.84 b
LSD3.72.93.42.20.090.060.050.04
y SI = Soil Improving, SC = Soil Conserving, DS = Disease Suppressive, SQ = Status Quo, PP = Continuous potato systems. Potato varieties: CR = Caribou Russet, RB = Russet Burbank. Values within columns for each factor followed by the same letter are not significantly different from each other based on ANOVA and Fisher’s protected LSD test (p < 0.05).
Table 8. Effects of different cropping systems and potato varieties on development of common scab (caused by Streptomyces scabies) on potato tubers over four field seasons (2019–2022).
Table 8. Effects of different cropping systems and potato varieties on development of common scab (caused by Streptomyces scabies) on potato tubers over four field seasons (2019–2022).
Incidence (% Infected Tubers)Severity (% Surface Coverage)
Factor y20192020202120222019202020212022
System
SI34.5 a61.0 bc72.4 b71.1 c1.53 a3.12 bc3.36 bc2.79 c
DS25.3 b58.5 c71.3 b70.7 c1.36 b3.05 c3.39 bc2.78 c
SC36.0 a56.7 c76.5 ab66.0 c1.58 a3.02 c3.49 b2.70 c
SQ38.7 a76.9 a70.5 b88.2 a1.62 a3.64 a3.32 c3.16 a
PP39.0 a67.1 b81.9 a77.8 b1.61 a 3.36 b3.77 a2.91 b
LSD6.87.96.44.30.14 0.240.150.09
Variety
CR28.2 b66.4 a74.9 a82.8 a1.14 b2.75 b2.89 b2.95 a
RB44.5 a60.5 b73.5 a66.7 b2.13 a3.98 a4.25 a2.79 b
LSD4.12.94.12.70.090.150.100.06
y SI = Soil Improving, SC = Soil Conserving, DS = Disease Suppressive, SQ = Status Quo, PP = Continuous potato systems. Potato varieties: CR = Caribou Russet, RB = Russet Burbank. Values within columns followed by the same letter are not significantly different from each other based on ANOVA and Fisher’s protected LSD test (p < 0.05).
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Larkin, R.P. Potato Cropping System and Variety Impacts on Soil Properties, Soilborne Diseases, and Tuber Yield in a Long-Term Field Trial. Agronomy 2024, 14, 2852. https://doi.org/10.3390/agronomy14122852

AMA Style

Larkin RP. Potato Cropping System and Variety Impacts on Soil Properties, Soilborne Diseases, and Tuber Yield in a Long-Term Field Trial. Agronomy. 2024; 14(12):2852. https://doi.org/10.3390/agronomy14122852

Chicago/Turabian Style

Larkin, Robert P. 2024. "Potato Cropping System and Variety Impacts on Soil Properties, Soilborne Diseases, and Tuber Yield in a Long-Term Field Trial" Agronomy 14, no. 12: 2852. https://doi.org/10.3390/agronomy14122852

APA Style

Larkin, R. P. (2024). Potato Cropping System and Variety Impacts on Soil Properties, Soilborne Diseases, and Tuber Yield in a Long-Term Field Trial. Agronomy, 14(12), 2852. https://doi.org/10.3390/agronomy14122852

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