In-row Spacing Research Articles

COMMERCIAL POMEGRANATE (PUNICA GRANATUM L.) PRODUCTION IN CALIFORNIA

Commercial pomegranate production in California is found primarily in the southern San Joaquin Valley, a region with Mediterranean type climate. Pome-granates have been grown in California since 1792, spread by Christian missionaries from Spain, and in commercial production since 1896 when shipments of trees arrived from Florida. For decades in the late 1900s the statewide hectarage remained near 1000, but has increased dramatically to 11700 in 2007, most of which is less than four years old. Pomegranates are often grown in conjunction with other permanent crops such as stone fruit and nut crops. Planting systems range from rows 3.6 to 5.8 m and in-row spacing from 1.5 to 5.2 m, with row spacing often determined by equipment preferences for other crops. Training systems are typically free-form multiple trunks, although single trunk and trellised production is being used. Irrigation systems, like crop spacing, are often dictated by companion crops found on individual farms; flood irrigation is found on older trees with newer trees planted with micro irrigation systems. Organic production of pomegranates remains limited due to market acceptance; challenges for organic production are Alternaria alternata and Aspergillus niger, as well as omnivorous leafroller (Platynota stultana) and flat mite (Brevipalpus lewisi). Numerous herbicides are registered for use in conventional pomegranates and weed barriers and hand weeding in organic systems. Both fresh market and juice fruit continue to be commercially harvested by hand but attempts at mechanization for both uses are underway. Common yields for mature pomegranates are as low as 6-10 MT/ha when used exclusively for fresh market consumption, but can be as great as 25-35 MT/ha when grown for juice, with the fresh:juice ratio dependant on both market conditions and autumn weather patterns. Most pomegranates are sold through food retailers in North America, and their current preference for high sugar/high acid, dark red rind color and dark red aril color favors cultivars such as ‘Granada’ and ‘Foothill’ in early season, and ‘Wonderful’ in main season. The United States Depart-ment of Agriculture National Clonal Germplasm Repository in Davis, California, contains selected lines sent from Dr. Levin’s Turkmenistan collection as well as genetic variants found in California production; variation for fruit attributes may influence consumer acceptance to other fruit types already common throughout pomegranate consuming cultures.

Evaluation of In-Row Plant Spacing and Planting Configuration for Three Irrigated Potato Cultivars

Research studies have shown that planting potatoes (Solanum tuberosum L.) in a bed configuration can improve water movement into the potato root zone. However, plant spacing recommendations are needed for potatoes planted in a bed configuration. This study was conducted to evaluate the effect of in-row plant spacing and planting configuration on yield of Russet Burbank, Russet Norkotah, and Ranger Russet potatoes under sprinkler irrigation. For the three cultivars, the effect of in-row plant spacing (three spacing treatments) for each planting configuration (4 row conventional ridged-row [4RC], 5 row bed [5RB], and 7 row bed [7RB]), and the effect of planting configuration at a uniform population on total tuber yield, U.S. No. 1 tuber yield, tubers per ha, average size (by weight), and large tuber yield were investigated at the USDA-ARS Northwest Irrigation & Soils Research Lab in Kimberly, ID on a Portneuf silt loam (coarse-silty mixed mesic Durixerollic Calciorthid) in 2008 and 2009. The greatest influence of in-row plant spacing was on average size and tubers per ha. In general, as in-row plant spacing increased (plant population decreased) the average tuber size increased and tubers per ha decreased. There was little influence of in-row spacing on measured production variables under the bed planting configurations except for tubers per ha which generally increased with narrower plant spacing. For Russet Norkotah and Ranger Russet there were few differences in measured production variables between planting configuration treatments. For Russet Burbank, the 4RC planting configuration had 14.6% significantly greater total tuber yield than the 7RB planting configuration, 20.2% greater U.S. No. 1 tuber yield than both bed planting configurations, and 25.2 and 29.9% greater large tuber yield than the 5RB and 7RB planting configurations, in 2009. Optimum production of Russet Norkotah and Ranger Russet potatoes is possible under all the planting configurations and plant spacing range evaluated in this study, granting growers flexibility in their systems, however, evidence from this study suggests that production of Russet Burbank may be less suited to bed planting configurations.

Wave Attenuation through Multiple Rows of Scatterers with Differing Periodicities

A solution method is proposed for calculating wave scattering by a multiple-row array in which the rows are permitted to have different periodicities. Each individual row contains an infinite number of identical and equispaced scatterers, which can be solved through standard techniques by invoking periodicity. Previous studies have investigated the wave attenuation produced by multiple-row arrays but in which the periodicity in the rows is fixed. However, this leads to difficulties around the resonant points, at which the number of scattering angles produced by the rows changes. The method outlined in the present work involves a discretization of the directional spectrum. This is combined with a mapping of the individual rows onto neighboring geometries that fit into the discrete system so that, as the mesh is refined, the geometry converges to its intended form. The method is applied to a canonical problem in which a potential function exists in the two-dimensional plane exterior to an array composed of circular scatterers, which have a Neumann condition imposed on their boundaries. Forcing is provided by an incident wave. Wave attenuation is investigated in a numerical results section using ensemble averages in which the row spacings and in-row spacings are chosen from normal distributions. Convergence of the solutions with respect to the numerical method is established, and examples of the smoothing effects gained from incorporating variation in the in-row spacing are given.

‘Mountain Merit’: A Late Blight-resistant Large-fruited Tomato Hybrid

‘Mountain Merit’ (NC 0694) was tested in observational trials in 2006 at MHCREC, Mills River (formerly Fletcher) and advanced to conventional replicated trials at MHCREC where it was tested each summer from 2007 to 2009. ‘Mountain Merit’ was tested in a replicated organic trial at Waynesville in 2009. Each trial consisted of two replicates with six plants per replicate. In-row spacing of plants was 45 cm and between-row spacing was 150 cm. The conventional trials were planted in early season (first week of June) and late season (first week of July) each year, whereas the organic trial was planted in the second week of June.

Yellow Nutsedge (Cyperus esculentus) Interference in Soybean

Field research was conducted in 2000 and 2001 to determine the effect of yellow nutsedge emergence timing and plant density on soybean yield and on yellow nutsedge propagation the following year. Yellow nutsedge tubers were planted at 0-, 7.5- (13/m2), 15- (8.6/m2), 30- (4.3/m2), 60- (2.2/m2), and 90-cm (1.5/m2) in-row spacings with soybean. Yellow nutsedge densities from 2.2 to 13 plants/m2in a high-yield year (2000) and 4.3 to 13 plants/m2in a low-yield year (2001) reduced grain yields 9 to 34%. In a separate experiment, tubers were planted 0, 2, 4, 6, and 8 wk after planting at a 15-cm (8.6/m2) in-row spacing. Seedlings that emerged with the crop and until 2 wk after planting reduced yield 9 to 11%. Yellow nutsedge densities from 1.5 to 13 plants/m2contributed to significant aboveground biomass production, even with a competitive crop, such as soybean. For every gram of aboveground yellow nutsedge biomass produced in the fall, there were more than four shoots present the following spring.

Effect of Plant Density on Bell Pepper Yield and Quality

Plant density can affect development and yield of bell pepper (Capsicum annuum L.). Information on the optimum plant density of different types of peppers in the Caspian Sea region is limited. The experiment was arranged in a randomized complete block with three plant densities (30,000, 42,000, and 78,000 plants·ha−1) with an in-row spacing of 0.45, 0.30, or 15 m between plants in rows 0.8 m apart and replicated three times. The 42,000 plants·ha−1 density produced suitable vegetative growth, best yield, and did not have any significant negative effects on bell pepper quality.

Effects of seed size and in-row spacing on growth and yield of early potato in a mediterranean-type environment in Turkey.

Optimizing plant density and seed size are the most important subjects of early potato production systems in mediterranean-type environments due to their effects on seed cost, plant development, yield and quality of the crop. The effects of different in-row spacing (20, 25, 30 and 35 cm) and seed size (small, medium and large) treatments on yield components and tuber yield of early potato were studied in Adana, where is situated in the east mediterranean region of Turkey, during 2006 and 2007 growing seasons. It was determined that closer spacing reduced tuber number per hill, average tuber weight, tuber yield per hill and percentages of large and medium size tubers. Total yields increased as increasing planting density up to 20 cm spacing. Planting larger seeds positively affected all growth and yield components in both years. Tuber yield per hectare was increased up to certain stem density and then started to decline at all seed sizes. However, the optimum stem density for the maximum tuber yield per hectare markedly differed depending on size of seed tubers. The optimum stem density increased with increasing seed size. Our findings indicated that size of seed tuber has further importance for growth of potato plant as well as competition aspect in early potato production in the mediterranean-type environments. Hence it was concluded that using larger tubers had an advantage for vigorous early growth and for obtain high tuber yield in early potato production in the mediterranean-type environments. Seed size should be considered during recommendation for planting density in potato production. Key words: Seed size, in-row spacing, early potato, competition.

Influence of Plant Density and Cultivar on Mini Triploid Watermelon Yield and Fruit Quality

Mini triploid (seedless) watermelons (Citrullus lanatus) are a growing segment of the U.S. watermelon market due to their small, one-serving size. Although mini triploid watermelons were first released and commercially grown about 6 years ago, little information is available for optimum planting densities that are needed to achieve the greatest percentage of marketable fruit in the 3- to 8-lb range. In 2006 and 2007, the fruit grade distribution response to six plant densities (2489, 3111, 4149, 6223, 8297, and 12,446 plants/acre) of four mini watermelon cultivars (Betsy, Petite Treat, Valdoria, and Vanessa) was measured at the Southern Illinois University Horticulture Research Center in Carbondale. ‘SP-1’ was used as the in-row pollenizer at 25% of the total planting. Although all cultivars responded similarly to the plant densities evaluated, ‘Vanessa’ provided the greatest fruit number and weight per acre, and percentage of fruit in the mini grade, compared with the other cultivars. Marketable mini triploid watermelon yield dramatically increased with closer in-row spacings. At lower plant densities (wider in-row spacings), a greater proportion of icebox-sized fruit (>8 lb) was produced, and the amount of marketable, mini-sized fruit (3–8 lb) declined. The grade distribution of mini triploid watermelon numbers and weights were the greatest at the highest plant density evaluated [0.5 ft in-row spacing (12,446 plants/acre)], with about 80% of the total yield in the mini grade. The greatest net revenues were also obtained at this high density. This study indicated that it is critical for producers of mini triploid watermelons to recognize the dramatic impact that plant density has on marketable fruit yield (3–8 lb). Growers of mini triploid watermelons will see a drastic improvement in revenues with closer in-row spacings compared with the approximate 2 ft in-row spacings currently used (about 4000 plants/acre). The increased cost of higher plant densities are more than offset by the greater return on investment.

Influence of Plant Density and Cultivar on Mini Triploid Watermelon Yield and Fruit Quality

Mini triploid (seedless) watermelons (Citrullus lanatus) are a growing segment of the U.S. watermelon market due to their small, one-serving size. Although mini triploid watermelons were first released and commercially grown about 6 years ago, little information is available for optimum planting densities that are needed to achieve the greatest percentage of marketable fruit in the 3- to 8-lb range. In 2006 and 2007, the fruit grade distribution response to six plant densities (2489, 3111, 4149, 6223, 8297, and 12,446 plants/acre) of four mini watermelon cultivars (Betsy, Petite Treat, Valdoria, and Vanessa) was measured at the Southern Illinois University Horticulture Research Center in Carbondale. ‘SP-1’ was used as the in-row pollenizer at 25% of the total planting. Although all cultivars responded similarly to the plant densities evaluated, ‘Vanessa’ provided the greatest fruit number and weight per acre, and percentage of fruit in the mini grade, compared with the other cultivars. Marketable mini triploid watermelon yield dramatically increased with closer in-row spacings. At lower plant densities (wider in-row spacings), a greater proportion of icebox-sized fruit (>8 lb) was produced, and the amount of marketable, mini-sized fruit (3–8 lb) declined. The grade distribution of mini triploid watermelon numbers and weights were the greatest at the highest plant density evaluated [0.5 ft in-row spacing (12,446 plants/acre)], with about 80% of the total yield in the mini grade. The greatest net revenues were also obtained at this high density. This study indicated that it is critical for producers of mini triploid watermelons to recognize the dramatic impact that plant density has on marketable fruit yield (3–8 lb). Growers of mini triploid watermelons will see a drastic improvement in revenues with closer in-row spacings compared with the approximate 2 ft in-row spacings currently used (about 4000 plants/acre). The increased cost of higher plant densities are more than offset by the greater return on investment.

In-row Distance in Triploid Miniwatermelon Cultivars Affects Yield and Quality in Diverse Environments in the Southeastern United States

The goals of these studies were to determine how miniwatermelon (Citrullus lanatus) cultivars differed and responded to plant in-row spacing in terms of percentage of marketable fruit and yields, and if plant spacing impacted internal fruit quality. Three genetically diverse triploid miniwatermelon cultivars (Mohican, Petite Perfection, and Xite) were selected. These cultivars were evaluated in field locations at northern Florida (Quincy), central South Carolina (Blackville), coastal South Carolina (Charleston), and eastern North Carolina (Kinston) at five within-row distances. Within-row distance included 9, 12, 15, 18, and 21 inches. All plots were15 ft long with row middles 9 ft apart. Fruit were categorized as marketable if they weighed between 3.1 and 9.0 lb per fruit. Within this range further categories were divided as follows: ≤3.0 lb (cull), 3.1 to 5.0 lb (small), 5.1 to 7.0 lb (average), 7.1 to 9.0 lb (large), and ≥9.1 lb (cull). There was a cultivar by location interaction, suggesting that the three cultivars responded differently at each of the four locations. ‘Petite Perfection’ was among the highest yielding at all locations except Quincy, where it was the lowest yielding cultivar. As with total yields, the percentage of marketable fruit was similar for some cultivars across locations. Cultivar Petite Perfection produced the highest percentage of marketable fruit at three of the four locations. The exception was the Quincy site where ‘Xite’ had the highest percentage of marketable fruit. Within-row plant distances and populations affected total marketable yield, both for fruit weight and number per plant, regardless of cultivar and location. As the plant population increased from eight plants per plot (21-inch in-row spacing) to 12 plants per plot (15-inch in-row spacing), total marketable miniwatermelon fruit yields increased in total fruit number as well as total weight. There was a cultivar by location interaction for the percentage of soluble solids and the rind thickness measurements, suggesting that some cultivars responded differently at each of the four locations. Quality effects were more apparent with ‘Mohican’ and ‘Xite’, as they were more responsive to location than ‘Petite Perfection’.

In-row Distance in Triploid Miniwatermelon Cultivars Affects Yield and Quality in Diverse Environments in the Southeastern United States

The goals of these studies were to determine how miniwatermelon (Citrullus lanatus) cultivars differed and responded to plant in-row spacing in terms of percentage of marketable fruit and yields, and if plant spacing impacted internal fruit quality. Three genetically diverse triploid miniwatermelon cultivars (Mohican, Petite Perfection, and Xite) were selected. These cultivars were evaluated in field locations at northern Florida (Quincy), central South Carolina (Blackville), coastal South Carolina (Charleston), and eastern North Carolina (Kinston) at five within-row distances. Within-row distance included 9, 12, 15, 18, and 21 inches. All plots were15 ft long with row middles 9 ft apart. Fruit were categorized as marketable if they weighed between 3.1 and 9.0 lb per fruit. Within this range further categories were divided as follows: ≤3.0 lb (cull), 3.1 to 5.0 lb (small), 5.1 to 7.0 lb (average), 7.1 to 9.0 lb (large), and ≥9.1 lb (cull). There was a cultivar by location interaction, suggesting that the three cultivars responded differently at each of the four locations. ‘Petite Perfection’ was among the highest yielding at all locations except Quincy, where it was the lowest yielding cultivar. As with total yields, the percentage of marketable fruit was similar for some cultivars across locations. Cultivar Petite Perfection produced the highest percentage of marketable fruit at three of the four locations. The exception was the Quincy site where ‘Xite’ had the highest percentage of marketable fruit. Within-row plant distances and populations affected total marketable yield, both for fruit weight and number per plant, regardless of cultivar and location. As the plant population increased from eight plants per plot (21-inch in-row spacing) to 12 plants per plot (15-inch in-row spacing), total marketable miniwatermelon fruit yields increased in total fruit number as well as total weight. There was a cultivar by location interaction for the percentage of soluble solids and the rind thickness measurements, suggesting that some cultivars responded differently at each of the four locations. Quality effects were more apparent with ‘Mohican’ and ‘Xite’, as they were more responsive to location than ‘Petite Perfection’.

Yield in Nonpungent Jalapeño Pepper Established at Different In-row Spacings

It is not known how plant spacing affects fresh yield in transplanted nonpungent jalapeño peppers (Capsicum annuum L.). Transplants of a nonpungent jalapeño, cv. Pace 105, were established at 8, 16, 24, 32, 40, and 48 cm between plants in mid-April of 2006 and 2007 and in early July in 2007. Fruit were harvested once when 5% of marketable-sized pods in rows were red. Distance to first flower and yield characteristics were determined. Fruit were culled based on pod size and presence of blemishes. Height on the stem to the first flower averaged 15.8 cm over all treatments. Plants in the Spring 2006 season had the highest marketable and cull yields. Numbers of marketable fruit/ha were higher at the 8-cm spacing than at the 40- or 48-cm in-row spacings. There was little difference in marketable yield as a result of in-row spacing. The greatest number of cull fruit per plant was on plants spaced 48 cm apart. Plant spacing had no effect on number of cull fruit or cull yield/ha. Culls accounted for ≈22% of total yield. Individual cull fruit weights were ≈50% less than for marketable fruit. Spacings tested did not appear to greatly affect development or yield of this pepper. This will allow producers to have the option of either using fewer plants on the same amount of land or more plants on less land without much reduction of quantity or quality of yield.

Effects of In-row Spacing on Eggplant Yield

Research was conducted to determine appropriate in-row spacing for eggplant (Solanum melongena) and to determine the best economic returns of this practice. ‘Classic’ eggplant seedlings were transplanted at in-row distances of 1.0, 1.5, 2.0, 2.5, 3.0, and 3.5 ft. Eggplant height decreased linearly as in-row spacing increased. In-row spacing affected total eggplant fruit number, with no fruit number differences among 1.0, 1.5, 2.0, and 2.5 ft, averaging ≈46,800 fruit/acre. Total fruit weight followed a trend similar to that for total fruit number and there were no differences among 1.0, 1.5, 2.0, and 2.5 ft (ranging between 18.2 and 19.9 tons/acre). From an economical standpoint, the comparison between 2.0 and 2.5 ft resulted in the former spacing having a marginal return rate of 8.03% in relation to an in-row spacing of 2.5 ft, which indicated that growers would earn $0.08 extra for each $1.00 of net profit by switching from 2.5 to 2.0 ft in-row plant spacing.

Competitive Effect of In-row Diploid Watermelon Pollenizers on Triploid Watermelon Yield

Successful fruit set in triploid watermelons [Citrullus lanatus (Thunb.) Matsum. & Nakai] requires a diploid watermelon cultivar, or pollenizer, to be planted nearby as a pollen source. Pollenizer cultivars have been developed to be planted in-row with triploid plants without spacing change, which decreases area per plant. These cultivars have different growth habits, from highly reduced foliage to standard foliage, and it is uncertain how pollenizer growth habit may affect triploid plant growth and yield. Two diploid watermelon pollenizers, ‘Mickylee’ and ‘SP-1’, with markedly different growth habits were planted at five in-row spacings from triploid plants to determine the effect of plant competition on triploid watermelon yield. All treatments used a 1:1 pollenizer to triploid ratio to measure the direct effect of pollenizer growth on associated triploid yields. Experiments were conducted at two locations during Spring 2006 (Quincy and Citra, FL) and one during Fall 2006 (Quincy). Triploid plants paired with ‘Mickylee’ yielded 11.4% (Citra) and 22.4% (Quincy) less weight in the spring and 8.5% less in the fall than plants paired with ‘SP-1’ and also produced fewer fruits per plant. However, the results from the fall trial were not significant. Pollenizer to triploid spacing had a linear effect on yield per plant and fruits per plant, and there was no interaction between pollenizer cultivar and spacing. The use of ‘Mickylee’ as a pollenizer may be an attractive option because of lower seed costs compared with other pollenizers, but these results indicated lower triploid watermelon yields from plants paired with ‘Mickylee’, which is most likely a result of increased plant competition.

Effects of Silver Reflective Mulch, White Inter-row Mulch, and Plant Density on Yields of Pepper in Maine

Bell peppers (Capsicum annuum) are an economically important yet difficult to grow crop in northern New England. Yields of bell peppers can be increased through the use of plastic mulches; however, refinements are needed to make bell peppers a more viable crop in regions with short, variable growing seasons. The objectives of this study were to (1) compare the effects of black mulch with white inter-row much, reflective silver mulch, and standard black plastic mulched beds on bell pepper yield and quality and (2) compare the effects of two in-row plant arrangements [single rows at 12-inch within-row spacing (7260 plants/acre) and double rows spaced 18 inches apart with 18-inch in-row spacing (9680 plants/acre)] on pepper yield and quality. Treatments were factorial combinations of three mulch treatments and two within-row planting arrangements. Double rows produced more fruit by number and weight than single rows; however, fruit harvested from the double-row plots tended to be smaller than fruit harvested from the single-row plots. Mulch treatments significantly influenced total marketable yield and yield of cull bell peppers grown in Maine. The plots receiving the inter-row white mulch or reflective silver mulch treatment produced significantly greater yield than standard black plastic mulch treatment. The reflective mulch treatment produced significantly more cull fruit per acre compared with the white inter-row mulch and black plastic.

Analysis of Ratio-based Responses

It is not appropriate to compare ratio-based expressions for different cultivars or treatments if a plot of the denominator versus the numerator of a ratio-based expression has a nonzero y-intercept and the values for either the denominators or numerators differ with cultivars or treatments. Whenever nonzero y-intercepts are encountered, the value for a ratio-based expression will be dependent on both the denominator and numerator. The “ratio problem” is demonstrated with shoot N concentration in blueberries (Vaccinium corymbosum L.) and amino acid accumulation in almonds [Prunis dulcis (Mill.) D.A. Webb]. Data were collected from the first and second growth flush of blueberry shoots on plants that were at two in-row spacings and two rates of N fertilizer. Free amino acid:total amino acid ratios were measured in dormant almond trees fertilized at different rates with and without foliar N supplements. Functions describing the relationship between dry weight and total N content in blueberry tissues have positive y-intercepts for both N fertilizer application rates. Functions describing the relationship between total amino acids and free amino acids in almond trees have a negative y-intercept. Differences attributable to fertilization rate in blueberries probably were the result of differences in N uptake and N utilization, but the effects of spacing and growth flush are indirect and can be accounted for by differences in dry weight. Likewise, effects of fertilization rate and foliar N supplement in almonds are indirect and can be accounted for by differences in the total amino acids in dormant trees. With regression one can determine if the relationship between the denominator and numerator differs for the groups or treatments being studied. When an analysis of covariance is used to account for differences in the denominators of ratio-based expressions, results are consistent with the regression analysis. When a conclusion is based on statistical differences of a ratio-based expression, it is the researcher's responsibility to determine whether these effects are direct or indirect.

VARIATION IN PLANT AND SOIL WATER RELATIONS AMONG IRRIGATED BLUEBERRY CULTIVARS PLANTED AT TWO DISTINCT IN-ROW SPACINGS

A study was conducted to determine the effect of in-row spacing on plant and soil water relations in 'Duke', 'Bluecrop', and 'Elliott' highbush blueberry (Vaccinium corymbosum L.) and to identify possible mechanisms that may enhance the ability of these cultivars to tolerate short-term soil water deficits. Changes in soil water content, stem water potential, and leaf stomatal conductance were measured 4 years after planting on well-irrigated plants of each cultivar spaced 0.5 or 1.2 m within rows on raised beds (~0.3 m high) and 3.0 m between rows. Irrigation (711 mm) was applied equally to all treatments by overhead sprinklers during the dry summer months from mid-May to early-September. Close spacing significantly reduced individual shoot dry weight, but also significantly increased crop light interception and water uptake from 0-0.6 m soil depth compared to plants spaced further apart. Spacing had little effect, however, on plant water relations. Independent of cultivar and spacing, stomatal conductance decreased rapidly as stem water potential approached -0.6 to -0.8 MPa. Among cultivars, 'Bluecrop' had the lowest root mass and root:shoot dry weight ratio at either spacing, while 'Elliott' had the highest. 'Duke', however, produced the deepest root system, extracting a significant amount of water below 0.6 m when plants were closely spaced. 'Duke' also maintained, on average, higher stem water potentials and greater stomatal conductance than the other cultivars as soil water was depleted.

Vegetative and productive responses of ‘Conference’ and ‘Williams’ pear trees planted at different in-row spacings

Abstract The effect of in-row spacing on the vegetative and productive performance of 4-year-old ‘Conference’ (CON) and ‘Williams’ (WIL) pear trees was studied. Analysis of digital images was used to estimate canopy growth and conformation. Fruit quality was determined by measuring fruit weight, flesh firmness, peel color, soluble solid content, and titratable acidity. WIL produced more and more efficiently than CON, especially at closer spacings. WIL canopies were generally bigger than CON canopies, and reduced spacing penalized stem growth and influenced canopy conformation. Root growth and conformation was similar for both cultivars, whereas decreasing in-row spacing reduced root dry weight, length, volume, and spread area only in WIL. Also, WIL trees partitioned more to fruit and leaves compared to CON, and increasing spacing resulted in a relative shift toward vegetative growth. CON fruit was smaller but sweeter and less acidic than WIL fruit. Increasing spacing influenced negatively WIL fruit quality parameters, with the only exception of fruit weight, which was increased. For the range of in-row spacing considered, our results indicate that WIL may represent a more efficient and competitive option than CON for high-density plantings, at least in the early stages of orchard life.

Plant spacing and cultivar affect melon growth and yield components

Abstract The objective of this study was to evaluate the effect of cultivars and in-row spacing on vegetative growth and yield components in melon ( Cucumis melo L.). The cultivars ‘Early Dawn’ (ED), ‘Superstar’ (SS) and ‘Medoro’ (ME) were grown in rows 1.5 m apart at plant spacing 0.6, 0.9, 1.2 or 1.5 m. Cultivars ED and SS were grown in 1998 and 1999, while ED and ME were tested in 2000. The main vine length, diameter, number of leaves and lateral branches were highest at 1.5 m in-row spacing in 1999 and 2000, while there was no influence of plant spacing on observed growth parameters in 1998. ED performed better compared with other two varieties, mostly due to more fruit per ha and per plant. Yield was significantly decreased with increased plant spacing in all 3 years of research. At in-row spacing of 1.5 m yield was in average 25% lower than at 0.6 m spacing. Average fruit weight slightly increased with plant spacing up to 1.2 m, even though the differences were significant only in 1999. Small differences among cultivars were also found. Number of fruit per ha decreased linearly while number of fruit per plant increased linearly as plant spacing increased in all cultivars except SS in 1999.

Growth-room and field studies with seed tubers treated with ethylene and 1-methylcyclopropene (1-MCP) during storage

Based on ethylene management in potato storage, we hypothesized that the applied treatments would modify number of sprouts per seed tuber. Thus, in combination with in-row spacing (closer for seed, wider for processing) in the field treatments will give either (1) a high number of small tubers destined for seed use, or (2) a relatively smaller number of large, uniform tubers suitable for processing. A three-year study (2001–2003), conducted with two french fry processing cultivars, Russet Burbank (RB) and Shepody (SH), aimed at the development of a novel modified atmosphere seed tuber storage treatment. Seed tubers were stored at 4 C from October to May of each year in a cold room under five modified atmospheric regimes: (1) air ventilation only (Control); (2) 4 µl L−1 ethylene applied continuously beginning in November and (3) beginning in February; (4) 1 µ1 L−1 MCP (1-methylcyclopropene) applied as a gas for 48 h only in early December followed by continuous 4 µl L−1 ethylene and (5) MCP alone applied as above. Each year, once a month (mid-January until end of April), a number of seed tubers was taken from each storage treatment, planted to pots and grown for 4 wk in a growth-room. In these studies, shoot emergence from the ethylene-treated seeds of both cultivars occurred significantly earlier, giving higher number of stems per tuber and stolons per stem than Control and MCP treatments. Moreover, the time to emergence after planting decreased with the increased length of storage. Field studies that were conducted from the end of May (planting) until October each year, produced similar trends (although not significant atP≤0.05) and resulted in a higher number of tubers per stem. In RB at the closer in row spacing (30 cm) used for seed production, ethylene enhanced yield of smaller tubers in the 30- to 115-g and 115- to 300-g categories. The ethylene storage treatments also increased tuber number per plant, but not the total mass of harvested potatoes. The MCP treatment, in combination with the wider in-row spacing (40 cm) used for the production of processing tubers, significantly increased the percentage of large tubers (>300 g). In SH, contrary to RB, the ethylene treatments did not alter tuber size distribution and the application of MCP reduced tuber size rather than increasing it. Results from this study suggest that both ethylene and MCP can be used in seed potato storage to influence the tuber size distribution of the crop from that seed.