Comparative performance of three small seed tuber sizes and standard size seed tubers planted at similar stem densities

Summary Small seed tubers of 1–5 g, 5–10 g and 10–20 g were planted at the same sprout densities as standard size seed tubers of 40–60 g in order to give similar stem densities. Early ground cover by foliage, total yield, and yield of tubers >45 mm were consistently greater in plots planted with larger seed tubers. The effect of seed tuber size on yield and tuber number per stem varied between years but 1–5 g seed tubers always gave lower yields per stem than larger seed tubers. Reducing the spacing between rows from 90 cm to 60 cm and maintaining the same sprout density was more effective in increasing yields from small seed tubers than increasing sprout density from 20 to 40 sprouts per m² by reducing plant spacing within the row.     

Microtuber and minituber production and field performance compared with normal tubers

Summary Microtuber and minitubers of cv. Monalisa were produced in the laboratory and compared with normal seed tubers in a field experiment. These tubers were planted at similar plant densities (13.6 sprouts per m²) with two distances between rows (60 and 90 cm). Final ground cover was almost complete only in the plots derived from normal tubers and decreased with the size of the mother tubers. Normal seed, mini- and microtubers yielded respectively 50.8, 31.7, and 17.0 t/ha (means of two spacings). At close and wide spacing between rows, microtubers yielded respectively 27.3 and 6.7 t/ha, and minitubers 38.9 to 24.4 t/ha. Row spacing did not influence the yields from normal seed tubers. Total number of tubers per m² was also affected and, as means of the two spacings, ranged from 107.8 with microtubers, 122.1 with minitubers, to 142.9 with normal tubers. Mother tuber type also affected the yield distribution in three tuber grades (<36, 36–55, and 55–80 mm) and micro and minitubers produced many small tubers. Multiplication rates and the possible use of different propagation sources are discussed.     

Effects of Mulch and Potato Hilling on Development of Foliar Blight (<Emphasis Type="Italic">Phytophthora infestans</Emphasis>) and the Control of Tuber Blight Infection

Foliar and tuber blight caused by Phytophthora infestans accounts for significant losses in potatoes in field and storage. Nevertheless, limited research has been published on the effects of cultural practices on late blight control. Field experiments were conducted in two years on Howard gravely loam soil in New York State to evaluate the effectiveness of mulching using oat straw and hilling in preventing tuber blight infection for cvs Allegany and Katahdin. Potato hilling and mulching had little effect on foliar blight development. The cultivar affected the disease development in the foliage, with cv. Allegany showing lower foliar late blight than cv. Katahdin. Tuber blight incidence averaged 25% for cv. Allegany and 3% for cv. Katahdin in hilled plots, while in the mulched plots the incidence of tuber blight averaged 33% for cv. Allegany and 10% for cv. Katahdin. The straw hay mulch was ineffective in tuber blight control. Tubers set at a soil depth of more than 7 cm had lower tuber blight incidence than shallow tubers set at a depth of less than 7 cm. In both years, hilling provided partial protection of tubers but its effectiveness was limited in the presence of favourable conditions for late blight development. Even though large hills had proportionally a lower tuber blight incidence than medium-sized hills, the difference between the different hill sizes was not significant. These studies suggest that the use of cultivars with foliage resistance to late blight in combination with cultural practices may partially reduce the incidence of tuber blight. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation for endorsement by Cornell University or the US Department of Agriculture.     

Effects of transitory water stress on potato tuber stem-end reducing sugar and fry color

Potatoes grown for processing in irrigated regions of the Pacific North-west sometimes develop undesirably high concentrations of reducing sugars in tuber stem ends due to hot weather and water stress during tuber development. Such tubers usually produce french fries with dark stem ends or sugar ends. In order to better quantify the relationship between water stress and stem-end sugar levels for Russet Burbank, single episodes of transitory water stress were established by delaying irrigations until soil water potentials ranging from -32 to -107 kPa were reached during early tuber bulking. To determine when the increase in reducing sugars occurred, tubers were sampled before transitory stress, at maximum stress, after stress was relieved with sprinkler irrigation, and post harvest. Reducing sugar concentrations did not increase in tuber stem ends until two weeks or longer after the plant water stress was relieved. Increased reducing sugar concentrations were positively associated with decreased soil water potential (drier soil). Tubers were sliced and fried at harvest and six weeks post-harvest. Decreasing soil water potential (drier soil) was associated with progressively darker fry colors at harvest and post harvest. Significant darkening in the average stem-end fry color light reflectance of tubers at harvest as observed at -80 kPa in 1988 and -69 kPa in 1989. The effect of imposed water stress on tuber stem-end reducing sugar concentrations was most pronounced post harvest.     

马铃薯种薯生产技术标准参数研究──Ⅰ．不同种植密度对种薯产量和块茎大小的影响

本研究以马铃薯极早熟品种“东农３０３”脱毒种薯为试验材料，将种薯分成（２０±５）ｇ和（３０±５）ｇ两组，分别按５个密度进行种植（行距均为７０ｃｍ，株距分别为１２．５、１５．０、１７．５、２０，０和２２．５ｃｍ）．试验结果表明，在哈尔滨的自然条件下，马铃薯块茎产量和单位面积块茎数目随着种植密度的增大而增加，单个块茎重量则随着密度的增加而减少．大种薯（３０±５）ｇ播种可以获得较高的块茎产量．在本试验中，种薯重量为（３０±５）ｇ、株１２．５和１５．０ｃｍ时，获得了较高的块茎产量和较多的块茎数．通过对植株地上部鲜重和叶面积指数变化的分析，表明高密度群体具有发育快、生长旺盛的特点。     

Hill to hill variations in tuber yield of potatoes in Alberta

The hill to hill variation in tuber yield and mainstem number was studied on 18 potato farms. There were up to 14-fold differences in the tuber yield per hill among plants of Norland, Russet Burbank, Norchip, Carlton and Alaska Red. The mainstem number was more variable than tuber weight per hill in Norland, Russet Burbank and Alaska Red. However, the opposite was true in Norchip and Carlton. In nearly all comparisons, the number of tubers per hill was less variable than tuber weight and mainstem number per hill. The total variation in tuber weight found in about 50% of the samples could be explained by the variance of hills within rows. Even in samples where an added variance component due to differences among rows was present, relatively more variation occurred within than among rows. The correlation coefficients between the number of mainstems and tuber weight per hill were positive but significant (P&< 0.05) only in Norland and Norchip. The correlation coefficients between the number of mainstems and number of tubers per hill were also positive but slightly higher and significant (P<0.01) in all 5 cultivars. The coefficient of determination values indicated that variation in cut seed piece weight explained only about 10% of the total variation in tuber weight harvested per hill. At a spacing of 30 cm within the row, a major proportion of hill to hill variation in tuber yield had to be explained by factors other than the seed piece weight.     

The dependence of internal brown spot development upon calcium fertility in potato tubers

Summary To determine calcium fertility and high temperature effects on internal brown spot development in potato, cv. Russet Burbank plants were fertilised with Hoagland's nutrient solution with or without calcium. Prevalence and severity of internal brown spot were greatest in tubers receiving no calcium fertilisation during growth. Internal brown spot was evident as early as tuber initiation. A high growth medium temperature (32°C) at tuber maturity with a lack of calcium increased internal brown spot incidence and severity. No tubers subjected to the high temperature and fertilised with calcium developed internal brown spot. Peel calcium concentration of tubers receiving no calcium fertilisation was lower (0.5–0.8 g/kg) than tubers receiving calcium (1.2–1.9 g/kg). Medullary tissue calcium concentration was similar under both calcium regimes. Calcium availability during early tuber growth was an influential factor in internal brown spot development, however high temperature effects may not be discounted in exacerbating the disorder. H/LA Paper No. 95-7. Project No. 1984, College of Agriculture and Home Economics Research Center, Pullman WA 99164, USA     

The effect of soil moisture and nitrogen on yield and quality of the Russet Burbank potato

A study was conducted to obtain more information on the effects of soil moisture and nitrogen on yield and quality of the Russet Burbank potato. Total yield of tubers increased with nitrogen rates as a result of more tubers per plant and larger tubers but the percent of malformed tubers also increased. Increased nitrogen rates decreased of dry matter of tubers and increased the total amino-nitrogen content of the tubers. Placing all of the nitrogen in bands on each side of the row produced more tubers having growth cracks, culls and reduced yield of No. 1’s when compared with broadcasting. Applying a moisture stress to potato plants during the early tuber set period increased the percentage of malformed tubers having pointed stem ends, bottlenecks and dumbbell shapes; although total yield and grade of tubers were not significantly affected. Irrigating when available soil moisture was 75 or 85 percent instead of 65 percent during the growing season did not affect total yield, grade or tuber quality at the five percent probability level.     

The influence of reduced temperatures after emergence on the subsequent growth and development of the potato

Summary The performance of potato platato plants raised under glass and transplanted to the field after emergence was compared with that of field-raised plants. The transfer from the warmer environment of the glasshouse to the cooler environment of the field resulted in immediate initiation of tubers. The period between initiation and the commencement of rapid bulking was, however, prolonged so that some of the advantage was lost. Nevertheless, this technique enabled yields, in the range of 2–6 tons per acre to be achieved some 4–5 days carlier; the tubers were also more uniform in size. Foliar applications of urea after tuber initiation hastened and extended the phase of rapid bulking, leading to carlier marketable yields and to higher yields at maturity. Urea applied before tuber initiation delayed its commencement. Plants which were transplanted after raising under glass always matured more quickly and gave lower final yields than field-raised plants. The physiological bases of the respones found are discussed. Some plants were exposed to frosts. Recovery from frost damage was rapid; the rate of tuber bulking was slower but yields at maturity were slightly higher than those of plants protected from forst.     

The effect of tuber size on the susceptibility of potatoes to metoxuron

Summary Field and pot experiments to determine whether the tuber size of volunteer potatoes affected their susceptibility to foliar applications of metoxuron are reported. The reduction in haulm weight of plants from small tubers (2–3 cm diameter) was greater than that of plants from large ones (4–5 cm diameter). This greater control was related to the lower vigour at spraying of the plants from the small tubers. It is suggested that these results could explain the variability in the level of control of volunteer potatoes achieved by metoxuron in carrot crops.     

Freezing behavior of potato (Solanum tuberosum) tubers in soil

Volunteer potatoes are a major weed problem in potato rotations in regions with mild winter soil temperatures. Freezing dynamics of potato tubers in air have been previously reported, but freezing dynamics of tubers in soil may differ due to ice nucleation sites and soil water associated with soil. Laboratory experiments conducted in hydrated and dry soil columns and field experiments were conducted to determine cold temperatures required to kill potato tubers in soil. Potato tubers in air-dried soil columns exposed to decreasing temperatures typically supercooled to ?3 to ?7 C before exhibiting a distinct exotherm, which stabilized at ?1.4 to ?1.5 C, representing the freezing point of tubers. Tubers that were supercooled and removed from the cold environment before experiencing this exotherm were able to sprout and had no visual symptoms of freezing injury, whereas tubers that experienced the exotherm were nonviable and unable to sprout. Tubers in soil columns hydrated to 7% SWC supercooled much less than tubers in dry soil and exhibited an exotherm that stabilized near ?1.9 C. Tubers exposed to temperatures near the tuber-freezing point (?1.4 to ?1.9 C) for periods of 1 min to 24 h, but not undergoing an exotherm, exhibited varying degrees of injury, which increased with time of exposure. Tubers held at ?1.0 C for 4 to 24 h were unharmed and able to sprout similar to controls. In field trials conducted from 1993 to 1999 in the Columbia Basin of Washington, tubers buried at shallow depths (5 cm) were much more likely to experience lethal cold temperatures than tubers buried deeper. In general, when minimum soil temperature at tuber depth reached ?1.5 to ?1.9 C or lower, some tuber mortality occurred and when soil temperature at tuber depth reached ?2.8 C or lower, extensive tuber death occurred. Monitoring of winter soil temperatures by depth in potato- growing regions could be used to predict severity of volunteer potato for the subsequent growing season.     

Potato production on wide beds: Impact on yield and selected soil physical characteristics

Planting three rows of potatoes in a bed the width of two conventional rows offers an easily managed way to increase seed piece populations, with the potential of increasing tuber yield and enhancing tuber quality. A wide bed production system (3 rows of potatoes planted on a 1.9 m flat-topped raised bed) was compared to a conventional-ridged system (1 row of potatoes in sharply sloped ridges on 96 cm centers) in 1996 and 1997 on a Norfolk sandy loam soil and a Portsmouth fine sandy loam soil in eastern North Carolina. Potato plant stands, leaf area index at approximately 9 WAP, yield, and quality were measured. Soil temperature, soil moisture, and cone index, as a measure of soil penetration resistance, were also measured, wide beds were more moist than conventional ridges early in the season. Cone index was greater throughout the root profile in wide beds in two of three tests. The row on the west side of an individual wide bed was most similar to conventional ridges in daily soil temperature fluctuations between minimum and maximum temperatures, and had greater fluctuations than the middle and eastern rows of the wide bed. Total yield and yield of grade A potatoes were not significantly different between wide beds and conventional ridges at either site. At one site, yield of grade B potatoes was significantly less in the wide bed; among the three rows in the wide bed, the eastern row had significantly lower yield of grade B potatoes. Conventional ridges had a higher percent of green grade A potatoes than the wide beds in one of three trials. Under North Carolina conditions, changing production systems would be unadvisable for most growers because wide beds do not increase yield enough to justify spending the money for more seed and to change equipment.     

Effect of Cooking and Processing on CIPC Residue Concentrations in Potatoes and Processed Potato Products

Residue concentrations of the sprout suppressant chlorpropham (or CIPC) were determined in raw and cooked potatoes and processed potato products, 48 h after CIPC aerosol treatment and after 30 days of subsequent storage at 4 or 12 °C. In the raw (uncooked) tuber, 48 h after CIPC treatment, the CIPC residue in the peel was 4.7 mg kg^-1, while in the peeled tuber it was 0.1 mg kg^-1. Boiling resulted in a decrease in residue concentration in the peel, but no significant differences in the residue concentration of the peeled tuber were observed. Pressure cooking resulted in a significantly increased residue concentration in the peel, but no significant change in the peeled tuber, whereas microwave cooking also did not increase the residue concentration in the peel significantly compared with that in raw tubers. Also the trend towards increases in residue concentration in microwave-cooked peeled tubers was not significant. The CIPC residue concentration detected in peeled tubers was 0.4–0.7 mg kg^-1 after boiling, 0.4–1.5 mg kg^-1 after pressure cooking and 0.4–3.8 mg kg^-1 after microwave cooking. The highest values were always found for tubers stored for 30 days at 4 °C. Processed products such as crisps, French fries, dehydrated sliced potatoes and starch contained different concentrations of CIPC residue, which was also detected in the cooking water and frying oil. The highest residue concentrations detected were 0.7, 4.7, 1.3 and 0.2 mg kg^-1 in crisps, French fries, dehydrated sliced potatoes and starch, respectively. The highest CIPC residue concentration observed in raw potatoes was much lower than the maximum residue level of 10 mg kg^-1 prescribed by the European Union.     

Effect of soil water tension and harvest time on levels of infestation byPhoma foveata Foister in soil and on tubers and stems of potato (Solanum tuberosum L.) in northern Sweden

Summary The incidence ofP. foveata in soil and tuber samples from field experiments often increased significantly as the harvest season progressed and temperatures fell. Mean levels of tuber and soil infestation were significantly higher in irrigated rows compared with those artificially sheltered from precipitation, both at normal and late harvest dates. Soil infestation was most frequently detected within 10 cm of the parent tuber. No pycnidia were visible on the haulm, and very few latently infected stem segments and leaves were detected using various methods. In three out of four years, the incidence ofP. foveata in tubers after wounding was reduced by washing them gently in tap water immediately after harvest.     

Sprouting of seed tubers during cold storage and its influence on tuber formation, flowering and the duration of the life cycle in a diploid population of potato

Summary The influence of a short tuber dormancy and the subsequent sprout growth of the seed tubers during storage at 4 °C on the processes related to plant development and tuber formation was investigated in a diploid population with 238 genotypes, its crossing parents and seven tetraploid varieties. Sprout growth during storage at 4 °C was positively correlated to the duration of the dormancy period at 18–22 °C, the low temperature prolonging the dormancy period. Results show that the duration of the dormancy period and the sprouting of seed tubers during storage at low temperature did not have a determinant influence on plant development, tuber formation or the duration of the plant cycle in this large and highly diverse population of potato.     

The response of cassava (Manihot esculenta) to spatial arrangement and to soybean intercrop

Response of cassava to row spacing and plant population density (0.62 plants m⁻² in 180-cm rows; 1.23 plants m⁻² in 90-, 180-, 270-, and 270- plus 90-cm (i.e. paired rows); and 2.46 plants m⁻² in 90- and 180-cm rows), and to soybean intercrop at two row spacings of cassava (90 and 270 cm) was studied at a high latitude (27°S) in south-east Queensland, Australia, where low temperature limits a growing season to 9 months. Detailed observations were made in sole crops on leaf canopy structure and light penetration in the three row spacings at the medium density to allow an estimation of light availability for an intercrop between cassava rows.The low plant density or the 270-cm row plants produced the lowest total dry matter and tuber yield at harvest, while the two higher densities or the two narrower rows produced similar total and tuber dry weight. Intercropped cassava produced a similar tuber yield to the sole crop at the corresponding spatial arrangement, but total dry matter was lower in the former.Leaf area index was similar among the 90-, 180- and 270-cm row spacings in sole crops throughout the growth period. However, leaf area was unevenly distributed horizontally for a longer time as row spacing increased. This resulted in light penetrating the inter-row space for a longer period in wider rows in sole crops, more than 50% full sunlight reaching soil level for 90, 120 and 130 days after planting in the 90-, 180- and 270-cm rows, respectively. This light environment would be available for an intercrop if cassava growth is not affected by the intercrop. The results for cassava intercropped with soybean show that in fact cassava growth was reduced by the associated soybean, and hence light available for the soybean growth would have been more than that estimated above.     

The immediate effect of gamma irradiation upon the sugar content of potatoes previously stored at 2, 4.5, 6, 10 and 15.5°C

Summary The sugar content of samples of potatoes, cv. Majestic, was varied by storage for 4 weeks at 2, 4.5, 6, 10 and 15.5°C, before irradiation with 10 krad. With initial sucrose contents of 0.14–0.37% FW (tubers from 4.5–15.5°C) the marked temporary increase in sucrose, as reported previously, was observed, reaching a maximum after 3–7 days before falling rapidly to a level rather higher than in non-irradiated tubers. Tubers from 2°C, with 1.4% sucrose, showed an immediate drop in this after irradiation, succeeded within 3 days by a rise to values not significantly different from the controls. Irradiation caused a significant increase in reducing sugar content, for a period of up to 7 days in sweetened tubers, but for 21 days or more in unsweetened tubers. Previous storage at the different temperatures had some permanent residual effect upon the sugar content of the controls during subsequent storage for up to 90 days at 10°C.     

Growth and Tuberization of Hydroponically Grown Potatoes

Three hydroponic systems (aeroponics, aerohydroponics, and deep-water culture) were compared for the production of potato (Solanum tuberosum) seed tubers. Aerohydroponics was designed to improve the root zone environment of aeroponics by maintaining root contact with nutrient solution in the lower part of the beds, while intermittently spraying roots in the upper part. Root vitality, shoot fresh and dry weight, and total leaf area were significantly highest when cv. Superior, a medium early-maturing cultivar, was grown in the aeroponic system. This better plant growth in the aeroponic system was accompanied by rapid changes of solution pH and EC, and early tuberization. However, with cv. Atlantic, a mid-late maturing cultivar, there were no significant differences in shoot weight and leaf area among the hydroponic systems. The first tuberization was observed in aeroponics on 26–30 and 43–53 days after transplanting for cvs Superior and Atlantic, respectively. Tuberization in aerohydroponics and deep-water culture system occurred about 3–4 and 6–8 days later, respectively. The number of tubers produced was greatest in the deep-water culture system, but the total tuber weight per plant was the least in this system. For cv. Atlantic, the number of tubers <30 g weight was higher in aerohydroponics than in aeroponics, whereas there was no difference in the number of tubers >30 g between aerohydroponics and aeroponics. For cv. Superior, there was no difference in the size distribution of tubers between the two aeroponic systems. It could be concluded that deep-water culture system could be used to produce many small tubers (1–5 g) for plant propagation. However, the reduced number of large tubers above 5 g weight in the deep-water culture system, may favor use of either aeroponics or aerohydroponics. These two systems produced a similar number of tubers in each size group for the medium-early season cv. Superior, whereas aerohydroponics produced more tubers than aeroponics for the mid-late cultivar Atlantic.     

Pre-sprouting as a Tool for Early Harvest in Organic Potato (Solanum tuberosum L.) Cultivation

Earlier harvest of potatoes (Solanum tuberosum L.) can be achieved by different pretreatments of the seed tubers. In factorial field trials in 2008–2010, two different pre-sprouting methods were evaluated: conventional pre-sprouting of tubers and pre-sprouting of tubers with stimulation of adventitious root formation (PR). The results were compared with those for untreated seed tubers stored at 4 °C until planting (control). One variety was included in three trials, and two varieties were included in one trial. The new PR method was intended to give faster development and tuber initiation than conventional pre-sprouting, which can be of value when the growing season is restricted or when early harvest is important. Plant emergence, leaf necrosis (as a measure of maturity) and incidence of late blight were assessed during the growing season. After harvest, tuber fresh weight, size and density were assessed. It was found that pre-sprouting treatments gave on average 7 days earlier emergence compared with the control. Necrosis began earlier in pre-sprouted treatments in all cases except for the late variety Sarpo Mira. In 2008 and 2009 potato late blight struck late, after onset of senescence, but in 2010 it struck earlier and the pre-sprouted treatments proved more susceptible than the control. Total tuber yield was 7–24% higher on average in all pre-sprouted treatments in the different field trials. Tests on time of harvest showed that the advantage for the pre-sprouting treatments was maintained during the season, but the difference with the control decreased with time. When the different pre-sprouted treatments were compared, the new PR method proved to be not better than conventional pre-sprouting.     

Row fumigation with Vorlex for control of a meadow nematode (Pratlylenchus penetrans) in potatoes

Row fumigation with Vorlex at 3 and 7 gallons per acre was applied for meadow nematode (Pratylenchus penetrans) control in potatoes. The material was applied 3 weeks before planting using one chisel per row at a depth of 8″, and ridged. The treatments resulted in a reduction in population ofP. penetrans in the soil and in the potato roots. On a soil with a relatively high population of meadow nematodes, row application of Vorlex at 3 and 7 gal per acre resulted in a yield increase of 10 and 14% respectively, and a lower incidence of tubers with vascular discoloration. By early October as many nematodes were present in treated rows as in untreated rows. Row fumigation is of value for only one potato crop.