Improving Sustainability of Paste Tomato Production in a High Tunnel and Open Field Through Cultivar Selection and Irrigation Management

Abstract

Sustainable vegetable production requires strategies that optimize yield while conserving water and minimizing resource inputs. This study, conducted at the Horticulture Research Farm near Absaraka, ND, evaluated the performance of several paste-type tomato (Solanum lycopersicum) cultivars under different irrigation strategies in high-tunnel and open-field production systems to identify cultivar and irrigation combinations that support sustainable production. Across seasons and production environments, cultivar significantly influenced marketable yield, fruit number, fruit size, and the proportion of unmarketable fruit, whereas irrigation treatments had limited effects on total and marketable yield. High-yielding cultivars such as ‘Granadero’, ‘Pozzano’, ‘Cauralina’, and ‘Amish Paste’ consistently produced greater marketable yields in both production systems, although ‘Cauralina’ also exhibited higher levels of fruit cracking and unmarketable yield. In high-tunnel production, deficit irrigation strategies based on soil moisture thresholds (10% and 30% management allowable depletion) maintained yields comparable to time-based irrigation, suggesting that water-efficient irrigation scheduling can sustain productivity. In the open field, cultivar responses varied under different irrigation regimes, highlighting the importance of selecting cultivars adapted to water-limited conditions. Fruit quality attributes, including soluble solids content and titratable acidity, were primarily influenced by cultivar rather than irrigation. Overall, the findings demonstrate that cultivar selection combined with water-efficient irrigation management can maintain tomato productivity while reducing water use and production losses. These results support the development of more sustainable tomato production systems that enhance resource-use efficiency, reduce waste from unmarketable fruit, and maintain fruit quality across diverse production environments.

1. Introduction

Tomato (Solanum lycopersicum L.) originated in western South America, including present-day Ecuador and Peru, and its global dissemination occurred following its introduction to Europe by Spanish colonizers in the 16th century, where subsequent domestication and diversification led to its widespread adoption and varied culinary uses worldwide [1,2]. Tomato is a globally important horticultural crop valued for both its nutritional composition and economic significance; however, its productivity is highly sensitive to environmental variability, particularly fluctuations in temperature and soil water availability [3,4,5].

In northern continental climates such as North Dakota, tomato production is constrained by a short growing season, low early-season soil temperatures, and large diurnal temperature variation, all of which can limit vegetative growth, reproductive development, and fruit maturation. These constraints have accelerated the adoption of high-tunnel (HT) systems, where passive microclimate modification enhances heat accumulation and protects crops from abiotic stress [6,7]. However, HT environments can also elevate daytime temperatures and vapor pressure deficit, thereby increasing crop evapotranspiration and plant water demand relative to open-field (OF) systems [8,9].

In contrast to regions where rainfall partially buffers crop water status, tomato production in HT systems of the northern Great Plains relies almost entirely on controlled irrigation inputs. Consequently, irrigation management must account not only for water-use efficiency (WUE) but also for maintaining plant physiological stability under rapidly changing environmental conditions. Previous studies have demonstrated that drip irrigation and deficit irrigation strategies can improve WUE and fruit quality in tomato; however, these studies have primarily focused on optimizing irrigation scheduling under relatively stable climates or controlled environments [10,11,12].

Emerging research emphasizes that improving sustainability in horticultural systems requires integrating irrigation management with genotype-specific resilience to water stress rather than focusing solely on maximizing resource efficiency [13]. In tomato, genotypic variation in traits such as stomatal conductance, root system architecture, osmotic adjustment, and fruit sink strength can significantly influence plant performance under soil moisture deficits [14,15,16].

High-tunnel production further modifies plant responses to water availability by altering microclimatic drivers such as radiation, temperature, and humidity, which regulate transpiration and plant water status [6,8]. These interactions highlight the importance of evaluating irrigation × environment × genotype interactions [17,18].

Management allowable depletion (MAD)-based irrigation scheduling provides a physiologically meaningful approach to regulating soil water availability by linking irrigation timing to plant-available water thresholds [19,20]. However, limited information exists on cultivar-specific responses under HT conditions, particularly in highly variable climates.

2. Materials and Methods

2.1. Site Description and Weather Monitoring

The experiments were conducted in an OF and an HT environment during the 2022 and 2023 planting seasons. The experimental site was situated at the North Dakota State University Horticulture Research Farm, Cass County, near Absaraka, ND (46°59′28.2″ N 97°21′19.9″ W, elevation of 1070 m). This area has been classified as continental with hot or mild summers, freezing winters and 380–760 mm of annual precipitation. Soil type at the site is a Warsing soil series, according to Soil Survey [21], which is a mix of extremely active, cold oxyaquic hapludolls, fine-loamy over sandy or sandy-skeletal Warsing soils with layered sand and gravel, and loam alluvium on top that drains reasonably well. This region’s lowest temperature, −34 °C, is inside plant hardiness zone 4a [22].

The HT trial was conducted in a gothic-style unheated HT (Northpoint, Rimol Greenhouse Systems, Inc., Hooksett, NH, USA) covered with a double-layer air-inflated four-year-rated 6-mil clear polyethylene greenhouse film treated with anti-condensate and ultraviolet features with 13-gauge steel framework for support. The length of the HT was oriented north to south with dimensions 29 m long, 9 m wide and 5 m tall. The HT was strengthened by nominal lumber-framed end walls, baseboards and hip boards. Ventilation was accomplished by thermostatically controlled electric roll-up sidewalls running the length of both sides set to open at 24 °C and motorized shutter vents in each gable end wall set to open at 25 °C. Additional air circulation during the hot days was provided by manually opening the two large end-wall doors.

In the field, weather data, air temperature, and rainfall were recorded using the North Dakota Agricultural Weather Network (NDAWN) station, located near Prosper, North Dakota, at an elevation of 284 m above mean sea level [23]. The temperature and rainfall sensors of the NDAWN station were 1.5 m above the soil surface. A Decagon EM50 data logger (Decagon Devices, Inc., Pullman, WA, USA) was deployed at the experimental site to monitor indoor and outside air temperature readings. Both data loggers measured air temperature similarly to the NDAWN stations.

2.2. Experimental Design and Land Preparation

Each of the nine beds in the HT and OF was 4.6 m long and 0.69 m wide. There was only one row of plants in each bed, with 0.69 m between plants and 1.83 m between rows. In this split plot study, the whole-plot factor was irrigation, while the sub-plot was the eight tomato paste cultivars Pozzano F1 (Johnny’s Selected Seeds), Amish Paste (Johnny’s Selected Seeds), Granadero F1 (Johnny’s Selected Seeds), Cauralina F1 (Burpee Seeds), Big Mama F1 (Burpee Seeds), Gladiator F1 (Burpee Seeds), Super Sauce (Burpee Seeds) and San Marzano (Burpee Seeds), replicated three times. The eight paste tomato cultivars were selected to compare high-yielding, modern hybrids (Pozzano F1, Granadero F1, Cauralina F1, Big Mama F1, Gladiator F1, Super Sauce) against popular heirlooms/standards (Amish Paste, San Marzano).

2.3. Crop Seeding and Transplanting

Tomato seeds were planted into the standard insert 800 series (T.O. Plastics, Clearwater, MN, USA) containing a soilless growing media (PRO-MIX BX, Premier Tech, Rivière-du-Loup, QC, Canada) six weeks before their intended transplant date (HT: 5 May 2022, and 1 May 2023, and OF: 1 June 2022, and 12 June 2023) at the NDSU greenhouse Fargo, ND (23.9 °C, 16:8 L:D, RH = 40–65%). After three weeks, seedlings were transplanted into SVD-450 molded plastic pots (SVD-450, T.O. Plastics, Clearwater, MN, USA) filled with the same growing media. Seedlings were fertigated weekly using a fertilizer injector (Dosatron International, Clearwater, FL, USA) and a 20-20-20 general-purpose water-soluble fertilizer (JR Peters Inc., Allentown, PA, USA) at 100 mg L⁻¹ N. Seedlings for the OF trials were acclimated at a protected outdoor location one week prior to transplanting.

2.4. Irrigation and Management Practices

Two lines of 15-mil drip tape with 20.3 cm spacing between emitters (Toro^® Aqua-Traxx, DripWorks, Willits, CA, USA) and 1.89 L min⁻¹ flow rate per 30.48 m drip length at a pressure range of 69–103 kPa were installed underneath the 0.025 mm black plastic mulch that was placed over each raised bed to conserve soil moisture and suppress weed seed germination. The drip irrigation system was controlled by a solenoid valve, flowmeter (Midwest Instrument, Sterling Heights, MI, USA), a soil potential sensor (Watermark, Irrometer Company, Riverside, CA, USA) and a controller with Wi-Fi. In both production systems, the following three irrigation regimes were applied: time-based (comparable to the traditional irrigation regime), 10% MAD and 30% MAD [23].

Soil potential sensors monitored the soil moisture status at 9:00 a.m., 3:30 p.m., and 9:00 p.m. every day for the 10% and 30% MAD. Irrigation for the time-based treatment was done every Monday, Wednesday, and Friday at 9:00 a.m. for a total duration of 24 min regardless of the soil moisture content. Crop management practices, such as weeding, were done by hand, while pest control was carried out when necessary, according to extension recommendations [24].

Fertilizer was applied in three separate doses throughout the growing season to achieve a total of 134.5:134.5:134.5 kg ha⁻¹ N:P:K. In 2023, some tomato plants in the HT and OF showed signs of micronutrient deficiencies, so in response, multipurpose micronutrients (Agro.K Inc., Fridley, MN, USA) were applied topically four times at 14-day intervals.

2.5. Harvesting and Data Collection

In the HT, fruits were harvested twice a week in both 2022 and 2023, from 10 July to 30 September and from 21 July to 25 October, respectively. Harvesting for the OF trials was done weekly from 5 August to 22 September 2022, and twice a week from 24 August to 17 October 2023. Tomatoes were picked at the “pink to red” stages of maturity according to the USDA maturity requirements and the unofficial visual aid provided by the USDA Marketing Service Fruit and Vegetable Division [25]. Appearance described the classification of the fruits into marketable and non-marketable categories.

Fruits were considered non-marketable due to the following defects: tomato spotted wilt virus, fruit cracking, insect damage, blossom end rot, cat-facing, and “other.” Fruit with minor scars or cracks was considered marketable. Tomato fruit samples were also collected in 2023 for the testing of titratable acidity (TA), pH, and total soluble solids (TSS). Representative fruits from each treatment per replication were randomly selected at the breaker stage during the early, mid, and late season of production for analysis. The pH was measured by a digital handheld pH meter (Atago Co., Ltd., Tokyo, Japan), and TSS (°Brix) was measured by a pocket refractometer [Model: PR-32 α, Atago Co., Ltd. (Tokyo, Japan)]. Fruit TA was determined by 0.1 N NaOH titration to an endpoint of pH 8.1 and expressed as a percentage of citric acid in 100 mL of juice [26].

2.6. Statistical Analysis

Data analysis was done using the linear mixed model procedures of SAS PROC MIXED (version 9.4; Statistical Analysis Software [SAS] Institute, Cary, NC, USA). The data were analyzed for the presence of significant main effects and interactions. When appropriate, the least-square means were compared using Fisher’s least significant difference test (p < 0.05). The cultivar and irrigation effects were considered fixed, while those of year and replications were considered random. Years were analyzed separately due to the virus outbreak in 2022 that decimated the OF tomato plants and eliminated OF data analysis in 2022.

3. Results

3.1. Weather Data in High Tunnel and Open Field

In June of 2022, the OF reached a maximum temperature of 38.5 °C, while the HT temperatures were consistently higher, peaking at 39.6 °C (Table 1). By July, the OF maximum temperature dropped to 36.6 °C, but the HT remained warmer, exceeding OF temperatures by 2.3 °C, 1.9 °C, and 2.9 °C for maximum, mean, and minimum readings, respectively.

Table 1. Mean maximum (Max.), average (Avg.) and minimum (Min.) air temperature (°C) for the open field and high tunnel at the Horticulture Research Farm near Absaraka, ND, during 2022.

	High Tunnel Temperature z			Open Field Temperature & Rainfall y
Month	Avg. (°C)	Max. (°C)	Min. (°C)	Avg. (°C)	Max. (°C)	Min. (°C)	Rain (mm)
May	18.2	32.2	3.6	-	-	-	103.0
June	23.1	39.6	7.4	21.2	38.5	3.4	93.0
July	25.1	38.5	13.5	22.8	36.6	10.6	84.7
August	23.2	38.6	12.1	20.8	35.9	8.3	56.1

^z High tunnel data is from 11 May to 26 August due to datalogger malfunction. ^y Open-field data represents data from 1 June to 25 August due to a datalogger malfunction.

In June of 2023, the average OF temperature reached a maximum of 35.9 °C and a minimum of 9.6 °C, while HT temperatures exceeded OF readings by 2.6 °C, 2.3 °C, and 5.2 °C for maximum, average, and minimum temperatures, respectively (Table 2). In July, the OF recorded highs of 36.4 °C and lows of 7.1 °C, with the HT remaining warmer by 3.1 °C, 4.3 °C, and 4.5 °C. The highest temperature in the HT, 40.7 °C, occurred in July, while the lowest temperature, −4.6 °C, was noted in October.

Table 2. Mean maximum (Max.), average (Avg.) and minimum (Min.) air temperature (°C) for the open field and high tunnel at the Horticulture Research Farm near Absaraka, ND, during 2023.

	High Tunnel Temperature z			Open Field Temperature & Rainfall y
Month	Avg. (°C)	Max. (°C)	Min. (°C)	Avg. (°C)	Max. (°C)	Min. (°C)	Rain (mm)
June	24.4	38.2	14.8	21.8	35.9	9.6	103.4
July	23.7	40.7	11.6	20.6	36.4	7.1	22.3
August	23.3	38.1	13.7	20.9	34.6	9.8	65.6
September	19.8	37.4	7.8	17.5	35.6	3.7	46.7
October	12.4	34.6	−4.6	10.0	34.1	−3.8	29.7
November	3.9	20.6	−2.1	0.0	5.1	−6.2	3.6

^z High tunnel data represents data from 15 June to 2 November. ^y Open-field data represents data from 15 June to 27 October.

3.2. High Tunnel 2022

3.2.1. Marketable Yield Parameters

There was no interaction between cultivars and irrigation treatments, but there was a cultivar effect on marketable yield, number of fruits plant⁻¹ and the average weight of individual fruits plant⁻¹. The mean marketable yield per plant ranged from 3.7 to 8.8 kg plant⁻¹ (Table 3). Although ‘Granadero’ had the highest marketable weight, this yield did not differ from the marketable yields of ‘Cauralina’, ‘Amish Paste’ and ‘Pozzano’. ‘Big Mama’ recorded the lowest marketable yield at 3.7 kg plant⁻¹, but this yield did not differ from the marketable yield of ‘Gladiator’, ‘San Marzano’, and ‘Super Sauce’.

Table 3. Marketable yield, total number of marketable fruit, and average weight of individual fruit produced per plant in the high tunnel in 2022.

	Marketable Fruit
Cultivar	Yield (kg Plant−1)	No. of Fruit Plant−1	Avg. Fruit Wt. (g)
Amish Paste	6.5 ab z	42.8 c	150 b
Big Mama	3.7 c	29.0 cd	130 c
Cauralina	7.2 ab	39.4 c	170 b
Gladiator	5.1 bc	30.4 cd	170 b
Granadero	8.8 a	99.6 a	90 d
Pozzano	6.8 ab	70.0 b	90 d
San Marzano	5.7 bc	96.7 a	60 e
Super Sauce	5.2 bc	19.4 d	280 a

^z Means followed by the same letter in the same column are not significantly different using Fisher’s Protected least significant difference (LSD) test at p < 0.05.

‘Granadero’ also had the highest number of marketable fruits plant⁻¹ (99), which was similar to the number of fruits produced by ‘San Marzano’ (Table 3). ‘Pozzano’ had the second most fruits plant⁻¹ (70), while the rest of the cultivars produced significantly fewer fruits, with ‘Super Sauce’ only averaging 19 fruits plant⁻¹, which was similar to the number of fruits produced by ’Gladiator’ and ‘Big Mama’.

‘Super Sauce’ produced the heaviest individual fruit, which weighed on average 280 g and was statistically greater than the individual fruit weight from the rest of the cultivars (Table 3). ‘San Marzano’ had the lightest individual fruit, which weighed 60 g and was significantly less than the individual fruit weight from the rest of the cultivars.

3.2.2. Total Yield and Unmarketable Yield

Irrigation did not affect the total yield or the unmarketable yield, and no cultivar by irrigation interaction was observed. However, cultivar had a significant influence on the total yield, the unmarketable yield, and the percentage of cracks. ‘Cauralina’ had the greatest total yield (10.8 kg plant⁻¹), although not significantly greater than Granadero’, ‘Amish Paste’ and ‘Pozzano’ (Table 4). ‘Big Mama’ had the lowest total yield at 5.3 kg plant⁻¹, although not significantly less than ‘San Marzano’, ‘Gladiator’, ‘Super Sauce’, ‘Pozzanno’ or ‘Amish Paste’.

Table 4. Total yield, unmarketable yield and percentage of fruit growth cracks produced per plant in the high-tunnel trial in 2022.

		Unmarketable
Cultivar	Total Yield (kg Plant−1)	Yield (kg Plant−1)	% Cracks
Cauralina	10.8 a z	3.5 a	14.0 a
Granadero	9.9 ab	1.2 bc	1.1 b
Amish Paste	8.5 abc	2.0 bc	19.1 a
Pozzano	8.1 abc	1.4 bc	1.7 b
Super Sauce	7.5 bc	2.3 b	15.8 a
Gladiator	7.2 bc	2.0 b	4.6 b
San Marzano	6.6 bc	0.9 c	0.2 b
Big Mama	5.3 c	1.7 bc	4.1 b

^z Means followed by the same letter in the same column are not significantly different using Fisher’s Protected least significant difference (LSD) test at p < 0.05.

The weight of the unmarketable fruits ranged from 0.9 to 3.5 kg plant⁻¹ (Table 4). ‘Cauralina’ had the highest unmarketable yield at 3.5 kg plant⁻¹, which was greater than the unmarketable yield from any other cultivar. ‘San Marzano’ had the lowest unmarketable yield at 0.9 kg plant⁻¹, which did not differ from the unmarketable yield of ‘Big Mamma’, Granadero’, ‘Pozzano’ and ‘Amish Paste’. Fruit cracks were the main cause for unmarketable fruit with ‘Amish Paste’, ‘Super Sauce’ and ‘Cauralina’ (19.1, 15.8 and 14%, respectively) having a higher percentage of fruit cracks compared to the remaining cultivars. ‘San Marzano’ had the fewest fruit cracks at 0.2% per plant, which was similar to the fruit cracks for ‘Granadero’, ‘Pozzano’, ‘Big Mama’ and ‘Gladiator’.

3.3. High-Tunnel Tomatoes 2023

3.3.1. Marketable Yield Parameters

The cultivar by irrigation interaction was not significant for marketable yield in 2023. In contrast, irrigation influenced marketable yield with the highest marketable yield of 8.1 kg plant⁻¹ from plants receiving 30% MAD irrigation, which was similar to the marketable yield from plants receiving 10% MAD irrigation (Table 5). Plants that received the time-based irrigation treatment had the lowest marketable yield at only 6.9 kg plant⁻¹.

Table 5. Effect of irrigation on the marketable yield produced per plant in the high-tunnel trial at the Horticulture Research Farm near Absaraka, ND, during 2023.

Irrigation	Marketable Yield (kg Plant−1)
30% MAD	8.1 a z
10% MAD	7.8 a
Time-based	6.9 b

^z Means followed by the same letter are not significantly different using Fisher’s Protected least significant difference (LSD) test at p < 0.05.

Cultivar influenced marketable yield, number of fruits plant⁻¹ and the average weight of individual fruits per plant. ‘Pozzano’ had the greatest marketable yield at 12.1 kg plant⁻¹, but this was not significantly higher than the marketable yield from ‘Granadero’ (Table 6). ‘San Marzano’ had the lowest marketable yield at 4.5 kg plant⁻¹, but this was not significantly lower than ‘Amish Paste’, ‘Big Mama’, ‘Cauralina’, or ‘Super Sauce’. ‘Pozzano’ had the highest number of fruits plant⁻¹ at 103 fruits, which was significantly higher than the fruit produced by any other cultivar. ‘Granadero’ and ‘San Marzano’ produced the second-highest number of fruits plant⁻¹. The rest of the cultivars produced lower numbers of fruits plant⁻¹, with ‘Super Sauce’ producing the fewest fruits plant⁻¹ at 22 fruits. ‘Super Sauce’ had the heaviest individual fruit at 310 g, which was statistically greater than any other cultivar. ‘Cauralina’ and ‘Gladiator’ had the second heaviest with an individual fruit weight of 220 and 190 g, respectively. ‘San Marzano’ had the lightest individual fruit at 70 g.

Table 6. Marketable yield, total number of marketable fruit and average weight of individual fruit produced per plant for high-tunnel cultivar trial in 2023.

	Marketable Fruit
Cultivar	Yield (kg Plant−1)	No. of Fruit Plant−1	Avg. Fruit Wt. (g)
Amish Paste	6.8 cd z	41.1 cd	170 c
Big Mama	6.0 cd	32.1 d	180 c
Cauralina	6.8 cd	30.7 d	220 b
Gladiator	7.7 bc	42.0 cd	190 bc
Granadero	9.8 ab	79.2 b	130 d
Pozzano	12.1 a	103.0 a	120 d
San Marzano	4.5 d	63.0 bc	70 e
Super Sauce	7.1 bcd	22.9 d	310 a

^z Means followed by the same letter in the same column are not significantly different using Fisher’s Protected least significant difference (LSD) test at p < 0.05.

3.3.2. Total and Unmarketable Yield (Cracks and Yellow Shoulder)

No interaction of cultivar by irrigation, nor the main effect of irrigation, influenced the total yield and unmarketable yield. However, there was a significant cultivar response with ‘Cauralina’ recording the greatest total yield at 13.8 kg plant⁻¹, which was not statistically greater than ‘Granadero’, ‘Amish Paste’ or ‘Pozzano’ (Table 7). ‘San Marzano’ had the lowest total yield at 5.1 kg plant⁻¹, but this yield did not differ from the total yield of ‘Big Mama’ or ‘Super Sauce’. ‘Cauralina’ and ‘Amish Paste’ had the highest percentage of cracks at 16.8 and 16.0%, respectively. ‘Cauralina’ also had the highest percentage of yellow shoulder disorder at 4.6%. This resulted in ‘Cauralina’ having a significantly greater unmarketable yield at 7.04 kg plant⁻¹ compared to any other cultivar.

Table 7. Total yield, unmarketable yield, percentage of cracks and yellow shoulder disorder produced per plant in the high-tunnel trial in 2023.

		Unmarketable
Cultivar	Total Yield (kg)	Yield (kg)	% Cracks	% Yellow Shoulder
Cauralina	13.8 a z	7.04 a	16.8 a	4.6 a
Granadero	10.4 abc	0.6 c	1.9 c	0.2 c
Amish Paste	10.4 abc	4.2 b	16.0 a	1.9 b
Pozzano	12.24 ab	0.04 c	0.4 c	0.05 c
Super Sauce	7.34 e	1.0 c	2.2 c	0.04 c
Gladiator	9.1 bd	1.4 c	7.7 b	0.5 c
San Marzano	5.1 e	0.7 c	0.3 c	0.6 c
Big Mama	6.4 e	0.7 c	1.6 c	0.1 c

^z Means followed by the same letter within the same column are not significantly different on the least significant difference (LSD) test at p < 0.05.

3.3.3. Fruit Quality

For fruit quality measurements, there were no significant interactions of cultivar by irrigation, and the effect of irrigation was not significant. Only cultivars influenced SSC and TA fruit quality measurements, while pH was not influenced by any factor. The fruit SSC ranged from 4.31 to 5.45 °Brix. ‘Cauralina’ had the highest fruit SSC, which was significantly higher than fruit SSC from all the other cultivars (Table 8). ‘San Marzano’, ‘Big Mama’, ‘Pozzano’ and ‘Amish Paste’ had the next highest fruit SSC. The rest of the cultivars had the lowest and statistically similar fruit SSC. ‘Granadero’ had the highest fruit TA, but this fruit TA did not differ from the rest of the cultivars except for ‘Gladiator’ and ‘Pozzano’, with the lowest fruit TA values of 0.10 and 0.12%, respectively.

Table 8. Soluble solids content (SSC), titratable acidity (TA), and pH of high-tunnel fruit harvested at the red ripeness stage from three harvests in 2023.

Cultivar	SSC (°Brix)	Titratable Acidity (%)	pH
Big Mama	4.58 bcd z,y	0.16 abc	4.22
San Marzano	4.72 bc	0.19 abc	4.04
Amish Paste	4.78 b	0.44 ab	3.92
Cauralina	5.45 a	0.55 a	3.9
Gladiator	4.33 cde	0.10 c	3.87
Pozzano	4.46 bcde	0.12 bc	3.84
Granadero	4.15 e	0.56 a	3.8
Super Sauce	4.31 e	0.14 abc	3.73

^z Values represent the means of fruit harvested at the red ripeness stage from three harvests in 2023 in the high tunnel. ^y Means followed by the same letter in the same column are not significantly different using Fisher’s Protected least significant difference (LSD) test at p < 0.05.

3.4. Open-Field Tomatoes 2023

3.4.1. Average Fruit Weight

In the open-field (OF) trial, there was no significant interaction between irrigation and cultivar for fruit weight. In contrast, irrigation had a notable effect on fruit weight, with plants receiving the time-based irrigation treatment producing the heaviest fruits at an average of 190 g, though this did not differ from the average fruit weight for plants under the 10% MAD irrigation treatment (Table 9). Plants in the 30% MAD treatment had the lightest fruits, averaging 130 g plant⁻¹, which was significantly lower than the fruit weights achieved by plants within the other two irrigation treatments.

Table 9. Effect of irrigation on tomato average fruit weight in the open-field trial at the Horticulture Research Farm near Absaraka, ND, during 2023.

Irrigation	Average Fruit Weight (g)
10% MAD	180 a z
30% MAD	130 b
Time-based	190 a

^z Means followed by the same letter are not significantly different on the least significant difference (LSD) test at p < 0.05.

3.4.2. Marketable Yield Parameters

No cultivar by irrigation interaction nor irrigation main effect influenced the marketable yield, number of fruits plant⁻¹, or average fruit weight. In contrast, cultivar had a significant effect on marketable yield plant⁻¹, with ‘Pozzano’ recording the highest marketable yield at 4.2 kg plant⁻¹, even though this was not statistically higher than ‘Granadero’ or ‘Gladiator’ (Table 10). ‘San Marzano’ produced the lowest marketable yield at 1.5 kg plant⁻¹, but this was not statistically less than the marketable yield for ‘Big Mama’, ‘Amish Paste’, ‘Cauralina’, ‘Gladiator’ or ‘Super Sauce’.

Table 10. Marketable yield, total number of marketable fruit and average weight of individual fruit produced per plant for the open-field trial in 2023.

Cultivar	Market Yield (kg Plant−1)	No. of Fruit Plant−1	Avg. Fruit Wt. (g)
Amish Paste	2.1 bc z	8.53 c	220 ab
Big Mama	1.8 c	11.2 c	180 bc
Cauralina	2.0 bc	8.2 c	240 a
Gladiator	2.5 abc	11.9 bc	180 abc
Granadero	3.7 ab	32.2 a	100 de
Pozzano	4.2 a	30.0 a	120 d
San Marzano	1.5 c	27.7 ab	60 e
Super Sauce	2.5 bc	10.4 c	220 ab

^z Means followed by the same letter within the same column are not significantly different on the least significant difference (LSD) test at p < 0.05.

‘Granadero’ produced the highest number of fruits at 32 fruits plant⁻¹, even though this was not statistically higher than ‘Pozzano’ and ‘San Marzano’ with 30 and 27 fruits plant-1, respectively (Table 10). The rest of the cultivars produced fewer fruits, ranging from 8 to 11 fruits plant⁻¹ with ‘Cauralina’ having the lowest fruit number plant⁻¹. In contrast, ‘Cauralina’ had the highest average fruit weight at 240 g. ‘Amish Paste’, ‘Super Sauce’ and ‘Big Mama’ were statistically similar in fruit weight with weights of 220, 220 and 180 g, respectively. ’Granadero’ and ‘San Marzano’ had significantly lower individual fruit weights, with ‘San Marzano’ having the lightest individual fruit at 60 g.

3.4.3. Total Yield

There was a significant interaction effect between cultivar and irrigation on total yield. When examining the influence of irrigation treatment for a cultivar, both ‘Big Mama’ and ‘San Marzano’ exhibited stable yields across all irrigation treatments, with no significant yield differences among the irrigation treatments (Table 11). In contrast, ‘Cauralina’ and ‘Pozzano’ showed significant variability in yield across the three irrigation levels, highlighting a differential response to irrigation treatments.

Table 11. Effect of the interaction effect of irrigation and cultivar across the irrigation regimes on tomato total yield harvested (kg plant⁻¹) in the open field at the Horticulture Research Farm near Absaraka, ND, during 2023.

	Total Yield
Cultivar	10% MAD	30% MAD	Time-Based
	kg Plant−1
Amish Paste	7.35 a z AB y	3.37 b A	7.81 a A
Big Mama	2.08 a C	3.17 a A	2.09 a BC
Cauralina	10.26 a A	1.48 c A	7.00 b A
Gladiator	3.01 b C	4.35 b A	8.74 a A
Granadero	5.67 a BC	2.70 b A	4.94 a ABC
Pozzano	5.37 b BC	1.81 c A	7.18 a A
San Marzano	3.14 a C	3.35 a A	1.71 a C
Super Sauce	4.31 a BC	2.32 b A	5.73 a AB

^z Means followed by the same small case letter across different irrigation regimes (in a row) are not significantly different using the least significant difference (LSD) test at p < 0.05. ^y Means followed by the same letter within the same column are not significantly different on the least significant difference (LSD) test at p < 0.05.

When examining the influence of cultivar for an irrigation treatment, ‘Cauralina’ and ‘Amish Paste’ produced the highest total yield under the 10% MAD regime, while ‘Big Mama’ had the lowest yield (Table 11). Under the 30% MAD irrigation level, total yield did not vary across cultivars. Under the time-based irrigation treatment, ‘Gladiator’ and ‘Amish Paste’ achieved the highest yields, whereas ‘San Marzano’ and ‘Big Mama’ had the lowest yields.

3.4.4. Fruit Quality

No significant differences were observed for the irrigation by cultivar interaction or the main effects of irrigation and cultivar on the fruit quality measurements, except for cultivar influence on fruit pH. ‘Pozzano’ had the highest pH at 4.0, but this fruit pH did not differ statistically from all the other cultivars except for ‘Granadero’ with a pH of 3.25 (Table 12). Fruit TA ranged between 0.68 and 1.37% while SSC ranged between 4.55 and 5.17 °Brix.

Table 12. Soluble solids content (SSC), titratable acidity (TA), and pH of open-field tomatoes in 2023.

Cultivar	pH	Titratable Acidity (%)	SSC (°Brix)
Big Mama	3.51 ab zy	1.37	4.77
San Marzano	4.01 a	1.27	5.27
Amish Paste	3.74 ab	1.11	5.02
Cauralina	3.61 ab	1.11	5.17
Gladiator	3.94 a	1.34	4.66
Pozzano	4.00 a	1.03	4.98
Granadero	3.25 b	0.84	4.97
Super Sauce	3.91 a	0.68	4.55

^z Values represent the least significant means of fruit harvested at the red ripeness stage from three harvests in 2023 in the open field. ^y Means followed by the same letter in the same column are not significantly different using Fisher’s Protected least significant difference (LSD) test at p < 0.05.

4. Discussion

Sustainable vegetable production increasingly depends on management strategies that optimize yield while conserving water and minimizing losses [27,28]. The results of this study demonstrate that cultivar selection exerted a stronger influence on paste tomato productivity and fruit quality than irrigation strategy across both high-tunnel (HT) and open-field (OF) systems. This finding reinforces the central role of genetic variability in determining crop performance and aligns with previous work identifying genotype as a primary driver of yield potential, fruit characteristics, and environmental stability [29,30,31].

Significant variation among cultivars for marketable yield, fruit number, and fruit size highlights the importance of genotype-specific source–sink relationships and assimilate partitioning. High-performing cultivars such as ‘Granadero’, ‘Pozzano’, and ‘Amish Paste’ likely maintained stronger sink demand through enhanced fruit set and carbon allocation, resulting in consistently higher productivity. However, yield formation in tomato reflects a genotype-dependent trade-off between fruit number and individual fruit weight [30,31]. Importantly, high total yield did not always correspond to high marketable yield. The cultivar ‘Cauralina’ produced substantial total yield but exhibited a high proportion of unmarketable fruit due to cracking and physiological disorders.

From a mechanistic perspective, fruit cracking is strongly associated with rapid fluctuations in plant water status driven by changes in soil water potential. Transitions from relatively dry soil conditions to near-saturation following irrigation or rainfall can induce abrupt increases in xylem flow and fruit turgor pressure, exceeding the mechanical limits of the fruit epidermis [32,33]. These responses are further modulated by temperature dynamics, particularly in HT systems where elevated temperatures increase vapor pressure deficit (VPD) and transpiration demand. Rapid rehydration under high VPD conditions can intensify transient water influx into fruit tissues, increasing cracking susceptibility. Cultivar-specific differences in cuticle composition, epidermal elasticity, and osmotic adjustment capacity, therefore, play a critical role in determining resistance to cracking. These findings emphasize that selecting cultivars combining high productivity with physiological resilience to water status fluctuations is essential to reduce losses and improve system efficiency [34].

In contrast to cultivar effects, irrigation treatments had relatively limited influence on yield, particularly under HT conditions. Soil moisture-based deficit irrigation (10% and 30% MAD) maintained yields comparable to conventional time-based irrigation, indicating that moderate reductions in soil water potential did not exceed critical physiological thresholds for yield formation. Tomato plants are capable of tolerating moderate soil water deficits (approximately −30 to −60 kPa) without substantial reductions in stomatal conductance or photosynthesis, provided that stress does not coincide with critical developmental stages such as flowering and early fruit set [35,36]. This tolerance is mediated through root-to-shoot signaling, particularly via abscisic acid (ABA), which regulates stomatal behavior and maintains water-use efficiency under mild stress [10,37].

The relatively weak irrigation response observed in this study may also reflect the application of season-long moderate deficits rather than stage-specific stress imposition. This approach likely avoided acute stress events that typically induce strong physiological responses, thereby minimizing both yield penalties and potential quality enhancements [36,38]. These findings support previous reports that regulated deficit irrigation can improve water-use efficiency while maintaining yield, particularly in controlled environments where soil moisture can be precisely managed [24,28,39,40].

In the OF system, irrigation influenced fruit size but had minimal impact on total yield, suggesting compensatory plant responses under moderate stress conditions. Reduced fruit size under deficit irrigation is primarily attributable to decreased cell expansion resulting from lower turgor pressure, while maintenance of fruit number indicates that reproductive processes were less sensitive under the imposed stress levels [41,42]. This compensation reflects the physiological plasticity of tomato plants, although the extent of this response is strongly genotype-dependent.

The HT system produced higher yields and fruit numbers than the OF system, consistent with previous studies [7,43,44]. Mechanistically, HT environments buffer temperature extremes, reduce wind-driven transpiration, and prevent rainfall-induced fluctuations in soil water potential, thereby stabilizing plant water relations. However, elevated temperatures within HTs can increase evaporative demand, necessitating precise irrigation management to maintain optimal soil moisture conditions. The results indicate that soil moisture-based irrigation effectively stabilizes plant water status under these conditions, preventing both excessive depletion and over-irrigation.

Fruit quality parameters, including SSC and TA, were primarily influenced by cultivar rather than irrigation treatment, consistent with previous findings [45,46]. The limited irrigation effect suggests that moderate deficit levels did not induce sufficient osmotic adjustment or metabolic shifts to substantially alter fruit composition. Nonetheless, slight increases in SSC under reduced water availability may occur due to concentration effects and changes in carbohydrate metabolism [4,46]. The high SSC observed in ‘Cauralina’ indicates potential suitability for processing markets, although its susceptibility to cracking may offset this advantage.

4.1. Limitations

This study was conducted over a limited number of seasons and environmental conditions, which may restrict extrapolation to broader climatic scenarios. Soil water dynamics were inferred from irrigation treatments rather than continuously monitored at high temporal resolution, limiting precise characterization of soil water potential thresholds. Additionally, physiological measurements such as stomatal conductance, leaf water potential, and hormonal signaling were not assessed, constraining mechanistic interpretation. The range of cultivars evaluated, while representative, does not capture the full extent of genetic variability available for resilience traits.

4.2. Future Research

Future research should integrate continuous soil moisture monitoring with plant-based physiological indicators (e.g., canopy temperature, sap flow, or crop water stress index) to better define critical thresholds for irrigation management. Investigations into the genetic and structural determinants of fruit cracking resistance, including cuticle properties and osmotic regulation, are needed to support breeding programs. Furthermore, evaluating cultivar performance under more extreme and variable climatic conditions will be essential for identifying resilient genotypes. The integration of precision irrigation technologies with decision-support systems also represents a promising approach for improving water-use efficiency at commercial scales.

4.3. Practical Implications for Sustainability

The findings indicate that cultivar selection represents a more robust and practical strategy than irrigation manipulation alone for enhancing sustainability in paste-type tomato production systems. Cultivars with stable yields, efficient assimilate partitioning, and reduced susceptibility to physiological disorders can significantly improve production efficiency and reduce waste. Soil moisture-based irrigation scheduling should be adopted to maintain soil water potential within optimal ranges, avoiding both excessive depletion and rapid rewetting cycles that exacerbate fruit disorders. In HT systems, sensor-based irrigation can reduce water use while maintaining productivity, whereas in OF systems, selecting resilient cultivars is critical for buffering environmental variability.

5. Conclusions

This study demonstrated that cultivar selection plays a central role in achieving sustainable tomato production across both high-tunnel and open-field systems under the unique climatic conditions of North Dakota. While irrigation strategies had relatively limited effects on marketable yield, soil moisture-based deficit irrigation approaches maintained yields comparable to conventional time-based irrigation in high tunnels, indicating that water use can be reduced without compromising productivity. Cultivars such as Granadero, Pozzano, and Amish Paste consistently produced high marketable yields, highlighting their potential suitability for sustainable production systems focused on yield stability and resource efficiency. However, some cultivars with high total yields, such as Cauralina, also exhibited higher rates of fruit cracking and unmarketable yield, emphasizing the importance of balancing productivity with fruit quality and marketability to reduce food loss. The lack of strong irrigation effects on many yield and quality parameters suggested that moderate deficit irrigation strategies may be viable tools for improving water-use efficiency, particularly in controlled environments such as high tunnels. Additionally, the differential responses of cultivars to irrigation in the open field indicated that cultivar selection should be aligned with site-specific water management practices to optimize performance under variable environmental conditions. Collectively, these findings highlight the importance of integrating cultivar choice with efficient irrigation management to support sustainable paste-type tomato production systems that conserve water resources, reduce production losses, and maintain high-quality yields.