马铃薯脱毒试管苗在不同扦插密度条件下的产量性状和经济参数的分析

为了探讨马铃薯脱毒试管苗在温室条件下的适宜扦插密度问题,利用早熟品种荷兰15号、中熟品种尤金和中晚熟品种克新13号的脱毒试管苗为试验材料,种植并生产原原种。采用单因素随机设计,设密度分别为每平方米154株、182株、222株、286株、400株和667株共6个处理,用方差分析探讨了扦插密度与结薯个数(单位面积上的商品薯数、单株商品薯数、单位面积上的结薯总个数、单株结薯总个数)、产量参数(单位面积上的商品薯产量、单株商品薯产量、单位面积上的总产量、单株产量)和经济参数(利润和经济效益)的关系。研究结果表明:荷兰15号、尤金和克新13号的脱毒试管苗扦插密度每平方米在154～667株之间时,随着扦插密度的增大,其结薯总个数均逐渐增多,单株商品薯产量和单株产量均逐渐变低;这3个品种在每平方米上的商品薯产量、总产量、利润和经济效益的变化趋势不同;通过结薯个数和经济参数的综合评价,得出荷兰15号和尤金的适宜扦插密度每平方米为400株,克新13号的适宜扦插密度为286株。     

晋西南山区川水地马铃薯不同栽培密度试验

对晋西南山区川水地覆膜种植的马铃薯主栽品种费乌瑞它进行不同栽培密度试验。试验结果的方差分析表明:每公顷密度在53 892～89 820株范围内,其单株商品薯数、单株薯重、单株商品薯重、小区产量、小区商品薯产量存在显著与极显著差异;单株结薯数无显著差异;小区产量以每公顷76 989株最高,小区商品薯产量以每公顷67 365株最高,而在生产实际中,追求更多的是商品薯产量,所以,该区域的马铃薯品种费乌瑞它覆膜种植以每公顷67 365株的密度为宜。     

Manipulating Stem Number, Tuber Set and Size Distribution in Specialty Potato Cultivars

Manipulating seed physiological age is an effective method to alter tuber set and size distribution for many cultivars. However, cultivars Cal White, Red La Soda, Chieftain, Yukon Gold, and Satina were largely insensitive to high temperature-induced age-priming treatments. Gibberellins (GA) also have potential for altering tuber set and size development. When applied to cut seed of the five cultivars, GA hastened plant emergence, increased stem and tuber numbers per plant, and decreased average tuber size. The optimum concentration of GA for shifting tuber size distribution to maximize crop value without decreasing total yield depended on cultivar. Total yields decreased substantially in all cultivars with 10 mg L^?1 GA but lower concentrations (0.5–4 mg L^?1) either increased yields of Red La Soda, Yukon Gold, Chieftain and Satina by 11, 13, 15, and 24 %, respectively, or had no effect (Cal White). GA-induced increases in tubers per hectare ranged from zero (Cal White, Satina) to 36 % (Chieftain) and associated increases in yields of premium priced creamer size potatoes (C size; 10–66 g, 28–51 mm diameter) ranged from 0 to 140 %, depending on cultivar and length of the growing season. Increases in total crop values ranged from 7 to 30 % (Chieftain) with the optimum concentrations of GA, which also varied by cultivar. Effective use of GA to alter tuber size distribution for increased value depends on cultivar, concentration, and harvest timing.     

株行距和施肥量对木薯产量及生长的影响

采用裂区试验设计方法,研究株行距和施肥量对华南5号木薯产量和生长的影响.结果表明:在本试验株行距和施肥量条件下,施肥量对木薯产量和生长的影响比株行距大.密植(0.6～0.8 m)有利于提高淀粉产量、鲜薯产量和鲜薯淀粉含量,以0.8m株行距最佳,而疏植(1.2～1.4m)有利于提高单株薯数、单株鲜薯重、单株鲜茎叶重、收获指数和茎径.施肥有利于提高淀粉产量、鲜薯产量、单株鲜薯重、单株鲜茎叶重、茎径、株高和单株薯数,但降低鲜薯淀粉含量和收获指数.丰产栽培技术要兼顾单位面积株数、单株鲜薯重和鲜薯淀粉含量.建议在土壤肥力差和少施肥时,用0.6 m株行距;土壤肥力中等且较高施肥时.采用0.8 m株行距;土壤肥力中上且优越水肥管理,采用1.0 m株行距.     

Effects of different plant density and nitrogen application rate on nitrogen use efficiency of potato tuber

In order to investigate the plant density and nitrogen level on nitrogen use efficiency components (agronomical, physiological, apparent recovery and nitrogen use efficiency), the amount of nitrogen uptake by plant, yield and yield components of potato (Solanum tuberosum L.) Agria cultivars' tuber, a factorial experiment based on randomized complete block design was conducted in Ardabil, Iran, in 2006 with three replications. Factors were adjusted for the nitrogen level (0, 80, 160 and 200 kg ha(-1) net nitrogen) and plant density (5.5, 7.5 and 11 plant m(-2)). Results showed that with increasing the nitrogen levels and plant densities agronomical nitrogen use efficiency, physiological nitrogen efficiency and nitrogen use efficiency were decreased and apparent recovery nitrogen efficiency was increased. The most nitrogen uptake in plant was observed at the 200 kg ha(-1) net nitrogen. The most yield and number of tuber per unit area were gained at the 80 and 160 kg ha(-1) net nitrogen. Increasing the plant density resulted in increasing in the tuber yield per unit area and the rate of nitrogen up to the 160 kg ha(-1) net nitrogen. So, application of the 80 kg ha(-1) net nitrogen and plant density of 11 plant m(-2) is recommended to get highest yield with the most nitrogen use efficiency.     

Efficacy of Seed Aging and Gibberellin Treatments for Manipulating Apical Dominance,Tuber Set and Size Distribution of cv. Shepody

The cultivar Shepody has excellent early processing qualities and produces above average tuber yields but sets relatively few tubers that often become excessively large relative to market demand. Optimizing tuber set and size of Shepody for seed and frozen processing markets currently entails adjusting in-row spacing and vine kill date. However, arresting tuber growth by vine killing for size control sacrifices yield potential. Aging seed by storing at 12, 22, and 32°C for 80-, 450-, and 900-degree days, or gibberellin (GA) treatments, were evaluated as more direct approaches for modulating stem number (apical dominance), tuber set, and size distribution relationships. Shepody proved to be inherently resistant to high temperature-induced age-priming treatments. In contrast to other cultivars studied previously, age-priming Shepody seed during storage had no effect on plant emergence and the resulting increases in stem number, tuber set, and associated decreases in average tuber weight were marginal. By contrast, GA applied as seed dip or spray effectively hastened plant emergence, reduced apical dominance, increased tuber set, and decreased average tuber size. The magnitude of these GA-induced effects depended on concentration and application technique (seed dip versus spray). For frozen processing, GA applied as a seed dip at 1 mg L^-1 added an additional tuber per plant and decreased average tuber size by 15% without affecting U.S. No. 1 tuber yields and gross returns; however, 2 and 3 mg L^-1 GA decreased U.S. No. 1 tuber yields and crop value by an average of 16 and 14%, respectively. Spray applications of 2–6 mg L^-1 GA also reduced U.S. No. 1 tuber yield and frozen processing value. Conversely, the increase in tuber set (1.5 tubers plant^-1) and associated 25% reduction in average tuber weight induced by 2 mg L^-1 GA applied as either dip or spray increased gross crop values on a seed contract by 25 and 38%, respectively. The differential efficacies of dip versus spray applications of GA on tuber set and size distribution were likely attributable to differences in GA deposition on the seed. Applying low concentrations of GA to cut seed of Shepody as either a dip (1–2 mg L^-1) or spray (2 mg L^-1) effectively modulated tuber set and size to significantly increase gross returns for seed, and to better satisfy the needs of processors for more moderate size tubers.     

How Planting Density Affects Number and Yield of Potato Minitubers in a Commercial Glasshouse Production System

Commercial potato minituber production systems aim at high tuber numbers per plant. This study investigated by which mechanisms planting density (25.0, 62.5 and 145.8 plants/m²) of in vitro derived plantlets affected minituber yield and minituber number per plantlet. Lowering planting density resulted in a slower increase in soil cover by the leaves and reduced the accumulated intercepted radiation (AIR). It initially also reduced light use efficiency (LUE) and harvest index, and thus tuber weights per m². At the commercial harvest 10 weeks after planting (WAP), LUE tended to be higher at lower densities. This compensated for the lower AIR and led to only slightly lower tuber yields. Lowering planting density increased tuber numbers per (planted) plantlet in all grades. It improved plantlet survival and increased stem numbers per plant. However, fewer stolons were produced per stem, whereas stolon numbers per plant were not affected. At lower densities, more tubers were initiated per stolon and the balance between initiation and later resorption of tubers was more favourable. Early interplant competition was thought to reduce the number of tubers initiated at higher densities, whereas later-occurring interplant competition resulted in a large fraction of the initiated tubers being resorbed at intermediate planting densities. At low planting densities, the high number of tubers initiated was also retained. Shortening of the production period could be considered at higher planting densities, because tuber number in the commercial grade > 9 mm did not increase any more after 6 WAP.     

Potato Crop Response to Genotype and Environment in a Subtropical Highland Agro-ecology

Potato response to environment, planting date and genotype was studied for different agro-ecological zones in Lesotho. Field experiments were conducted at four different sites with altitudes ranging from 1,655 to 2,250 m above sea level during the 2010/2011 and 2011/2012 summer growing seasons. Treatments consisted of three cultivars that varied in maturity type, two planting dates and four sites differing in altitude and weather patterns. Various plant parts were measured periodically. To understand and quantify the influence of abiotic factors that determine and limit yields, the LINTUL crop growth model was employed which simulated potential yields for the different agro-ecological zones using weather data collected per site during the study period. Observed actual crop yields were compared with model simulations to determine the yield gap. Model simulations helped to improve our understanding of yield limitations to further expand potato production in subtropical highlands, with emphasis on increasing production through increased yields rather than increased area. Substantial variation in yield between planting date, cultivar and site were observed. Average tuber dry matter (DM) yields for the highest yielding season were above 7.5 t DM ha^?1 or over 37.5 t ha^?1 fresh tuber yield. The lowest yield obtained was 2.39 t DM ha^?1 or 12 t ha^?1 fresh tuber yield for cultivar Vanderplank in the 2011/2012 growing season at the site with the lowest altitude. Modelled potential tuber yields were 9–14 t DM ha^?1 or 45–70 t ha^?1 fresh yield. Drought stress frequently resulted in lower radiation use efficiencies and to a lesser degree harvest indices, which reduced tuber yield. The site with the lowest altitude and highest temperatures had the lowest yields, while the site with the highest altitude had the highest yields. Later maturing cultivars yielded more than earlier maturing ones at all sites. It is concluded that the risk of low yields in rain-fed subtropical highlands can be minimised by planting late cultivars at the highest areas possible as early as the risks of late frosts permit.     

密度和钾肥对马铃薯品种东农306产量的影响

以特用型马铃薯品种"东农306"为材料,在2003～2004年进行了种植密度与钾肥用量对产量的影响试验。结果表明,该品种在不同种植密度与钾肥用量下单株产量差异显著,在本试验中以行距70 cm和株距30 cm的密度、硫酸钾用量150 kg·hm~(-2)最适合该品种的个体生长,能获得较高的单株产量和商品薯产量;行距70 cm和株距20 cm的密度、硫酸钾用量75 kg·hm~(-2)最适合该品种的群体生长,能获得较高的群体产量和商品薯产量。     

Effects of intraspecific competition on yield of early potato grown in mediterranean environment

Since the environment of the Mediterranean regions allows offseason production, potatoes are planted in autumn-winter and harvested in spring. During this period, potatoes are subjected to low temperatures and short day lengths which modify the growth characteristics of plants. For this reason, our analysis of competition response was conducted to better clarify the biological relationship between yield and plant density. Field trials were conducted in Sicily (south Italy), a highly representative area of early potato crop in the Mediterranean Basin, with the aim of studying effects of intraspecific competition on tuber yield and yield components. Ten planting densities (ranging from 3.0 to 8.0 plants m^?2) were studied on cv. Spunta using “tuberpieces” with a different number of eyes (one eye or all the eyes in 1996; one eye, two eyes, or all the eyes in 1997). Intraspecific competition reduced the tuber yield of individual plants, which became gradually less evident with increasing plant density. Competition affected the number of tubers per plant in the lower plant populations only (from 3.0 to 5.8 plants m^?2), whereas effects on average tuber weight were at times more marked in the higher populations (from 5.8 to 8.0 plants m^?2) and at other times in the lower densities (from 3.0 to 5.8 plants m^?2). As a consequence of increased plant density, and notwithstanding the higher intraspecific competition, the yield of tubers per unit area increased linearly. Regardless of the number of eyes per tuber-piece, when passing from the lower to the higher plant density, yield increased from 34.0 to 54.11 ha^?1 in 1996 and from 39.9 to 56.7 t ha^?1 in 1997.     

Potato Late Blight and Tuber Yield: Results from 30 Years of Field Trials

During 1983–2012, three field trials per year were performed in each of the three southernmost counties in Sweden to test different fungicide programmes aiming to control late blight, primarily in the very susceptible potato cultivar Bintje. A dataset with results from these field trials was used (i) to examine possible changes in the appearance and behaviour of late blight attack over the years, (ii) to investigate the relationship between late blight in foliage and tuber blight, (iii) to investigate the relationship between late blight and tuber yield and (iv) to identify any correlations between different variables in the dataset. Late blight reached epidemic proportions, i.e. 75% disease severity in the untreated control, in the majority of the field trials. The estimated first attack of late blight was earlier in many field trials after 1998. Differences between years and regions were great in terms of date of the first attack and how the attack developed during the season. For example, in 2002–2005 and 2007, the first attack occurred 40–55 days after planting (DAP), compared with 95–108 DAP in 1994 and 1996. In 1994, 2006 and 2009–2011, the attacks increased from first symptoms to 65% disease severity in the untreated control within 16–21 days, compared with 35–40 days in 1995, 1999 and 2002. The relationship between foliage late blight and tuber blight was weak with the best match found at high disease severity late in the growing season (r?=?0.33; p?<?0.001). The relationship between blight-free tuber yield and start of the first attack indicated a yield increase of 287 kg/day (R ²?=?0.27) for every day’s delay in first attack. Using the DAP for 65% disease severity in the untreated control improved the correlation (R ²?=?0.64) and indicated a yield increase of 534 kg/day for every day’s delay in first attack. The later the onset of attack, the higher the blight-free tuber yield in treated plots. In general, significant correlations were found between blight-free tuber yield, size fractions of tuber yield, date of first late blight attack, date of different degrees of disease severity, disease severity, date of treatment, treatment measures and maintenance.     

Population density studies with Russet Burbank II. The effect of fertilization and plant density on growth,development and yield

The response of Russet Burbank grown at five plant densities (4.0 to 11.1 × 10⁴ plants ha^?1), to level of fertilization was studied in field experiments at Guelph, Canada in the 1972 and 1973 growing seasons. Growth analysis techniques were used to establish growth patterns of Russet Burbank at three of the above plant densities (4.0,6.3 and 11.1 × 10⁴plants ha^?1), while the effect on root development of rate of fertilization was observed in controlled environments. In both seasons total tuber yield was not influenced by plant density, while marketable yield showed a negative response to increased density. The interaction between plant density and level of fertilization did not approach significance in either season. Due to greater axillary branching at the lower plant densities, leaf area index and photosynthetically active radiation measured at two levels in the canopy, were similar at all densities. Fertilizer levels used in the field showed no negative effect on root growth in experiments conducted in controlled environments. Marked variation in the number of mainstems and thus the number of tubers produced per plant between seasons indicated the importance of using the mainstem as the basic population unit.     

Yield-enhancing and tuber-downsizing effects of transplantation cultivation method of case-held tuber seedlings in the sweet potato cultivar Beniharuka

We developed transplantation cultivation method of case-held tuber seedlings (CTS), which was derived from direct planting method of seed tubers, and applied this method to the sweet potato cultivar Beniharuka. A plastic case made of polypropylene was designed for cultivation of CTS. Seed tubers of cultivar Beniharuka in the range of 30–80 g were cut in half. The half-cut tubers were placed inside the plastic cases, and the cases were filled with a commercial soil mix. The case-held tubers were incubated under natural sunlight in a glass house. After 3–4 wk, the CTS were transplanted into a field. Mother tuber (seed tuber) enlargement was suppressed by the plastic confinement of the cases, and daughter tubers were formed above the case as vine-root-originated tubers. In the field experiments in 2012 and 2013, daughter tuber yields were increased 19% and 21% by case-held tuber seedling transplanting (CTST) over conventional vine-planting (VP), the number of daughter tubers per plant in CTST were 36 and 68% higher than in VP, and the mother tuber yields were limited to 2.1 and 4.3% of the total fresh yield of mother and daughter tubers, respectively in 2012 and 2013. Application of CTST method to cultivar Beniharuka enhanced tuber yield, increased the number of daughter tubers per plant, downsized daughter tubers compared to VP, and mother tuber enlargement was suppressed by case-holding. The CTST method is expected to produce more and smaller good in shape tubers of cultivar Beniharuka compared to VP.     

Potato (Solanum spp.) in the hot tropics. VI. Plant population effects on soil temperature,plant development and tuber yield

Nine experiments were run at three hot tropical sites (5–12°S, 180–800 m) within Peru to quantify the influence of plant population on soil temperature and growth and yield of the potato.Radiation interception was greatest at the highest plant populations and soil cooling was directly proportional to the amount of crop cover over the soil, but no appreciable effect on the timing of tuber initiation was apparent. More stems per unit land area leading to a higher leaf area index (lai) were primarily responsible for greater interception of radiation at the higher plant populations, although some compensation in stem number per unit land area and in lai at lower populations was evident later in the season.In general, tuber yield increased linearly with increases in planted population over the range studied (2.7–12.5 plants m⁻², and in one experiment to 31.7 plants m⁻²), and was proportional to increases in the amount of intercepted radiation. Tuber yields ranged from 8 to 60 t ha⁻¹ over sites and populations. Vigorous clones with Solanum tuberosum spp. andigena in their genetic background constituted the exceptions to this linear trend, and for these clones yields declined at the highest populations, particularly when the rectangularity of planting vastly deviated from square patterns. Tuber yield of Solanum tuberosum spp. tuberosum and Neotuberosum (S. tuberosum spp. andigena selected for tuberization under long-day conditions) clones did not respond to variations in rectangularity of planting and, probably due to their small stature and early maturity, did not demonstrate signs of intense between-plant competition for tuber yield as measured with the Kira competition density index. In contrast, for clones with Solanum tuberosum ssp. andigena in their genetic background, maximum tuber yield at populations greater than 5.5 plants m⁻² was dependent on the rectangularity of planting, and declined as the latter deviated from squareness.Since the proportion of marketable tubers was scarcely affected by the planting densities, plant population of S. tuberosum ssp. tuberosum clones planted in hot climates should be as close as possible without limiting the amount of soil available for hilling-up.     

Influence of Foliar-Applied Growth Retardants on Russet Burbank Potato Tuber Production

The potato cv Russet Burbank grows poorly in the semi-arid climate of the High Plains, primarily due to its tendency to produce misshaped tubers. Since gibberellic acid (GA₃) is associated with stem elongation and may be involved in tuber shape, the objective of this study was to determine whether GA₃ biosynthesis inhibitors could improve tuber shape. Prohexadione-Ca and chlormequat-Cl are two well-known such inhibitors. They were applied to ‘Russet Burbank’ at 0, 70, 280, 1,120, 4,480 g/ha when the largest tubers were 20, 60 and 100 g/tuber from 2001 to 2003. Neither compound affected tuber shape. Yields increased 17–20 % by prohexadione-Ca at 280 g/ha and 9–33 % by chlormequat-Cl at 4,480 g/ha. In 2004, prohexadione-Ca at 280 g/ha was applied when the largest tubers were 3, 25, 100, 180, and 370 g to determine a tuber stage response. Yield increased 14 % when applied at 25 and 100 g/tuber growth stages, but the number of misshaped tubers increased from 48 % to 75 %. These two inhibitors did not overcome tuber misshaping and should not be used for that purpose.     

Auxin Modulates Gibberellin-Induced Effects on Growth,Yield, and Raw Product Recovery for Frozen Processing in Potato (<Emphasis Type="Italic">Solanum tuberosum</Emphasis> L.)

Tuber shape phenotype is an important determinant of raw product (≥7.6-cm-long French fries) recovery for frozen processing. Tuber length-to-width (L/W) ratios ≥1.8 translate to maximum yield of raw product; however, some cultivars produce tubers with much lower L/W ratios. While gibberellin (GA) can be used to elongate tubers, it also decreases tuber size and can thereby attenuate raw product recovery. We investigated the utility of GA and naphthaleneacetic acid (NAA) combination treatments for modifying tuber set, size, and shape to increase yield of raw product from ‘Payette Russet’ and ‘Alturas’; two late-season frozen-processing cultivars that often produce tubers with undesirably low L/W ratios. Models describing L/W ratio and fry yield by tuber size class were developed to translate total U.S. No. 1 tuber yields (>113 g) into yield of raw product. Increases in the L/W ratios of 113–284-g tubers had a greater effect on recovery of French fries (% fresh wt) than for tubers >284 g. Undersize (<113 g) and oversize (>340 g) tubers yielded 0 and 96% fries, respectively, regardless of L/W ratio. GA applied as a seed treatment effectively hastened emergence and altered tuber shape by increasing the L/W ratios of ‘Alturas’ and ‘Payette Russet’ tubers, enhancing total fry yield for the 113–340-g tubers by 24–46%, depending on concentration and application technique (dip, spray, in-furrow). However, GA also decreased apical dominance and shifted tuber size distribution away from >284-g tubers toward higher yields of <170-g tubers, erasing the gains in fry yield when all size classes (>113 g) were considered. When combined with GA, NAA maintained apical dominance, attenuated the shift in tuber size distribution, had no effect on the GA-induced increase in tuber L/W ratio, and only partly moderated the GA-induced stimulation of plant emergence. Raw product yield from ‘Payette Russet’ increased 12–39% in spray application trials by using NAA to confine the effect of GA to tuber shape and limit the loss of U.S. No. 1 tubers to undersize. Increases in tuber L/W ratio with GA/NAA seed treatments translated to increased yield of fries only when the relative concentrations were adjusted to minimize loss of >284-g tubers and gain in undersize tubers, as dictated by cultivar sensitivity to GA. ‘Alturas’ was less sensitive to GA than ‘Payette Russet’ for shifts in tuber size distribution but not shape, resulting in 17% increase in raw product with GA alone in pre-plant seed spray application studies. GA/NAA combination treatments provide an effective approach to manipulate tuber size distribution and enhance the yield of raw product for frozen processing in cultivars with a rounder tuber shape phenotype.     

The Effect of Nitrogen Rate on Vine Kill,Tuber Skinning Injury,Tuber Yield and Size Distribution,and Tuber Nutrients and Phytonutrients in Two Potato Cultivars Grown for Early Potato Production

Early potatoes are typically produced using less nitrogen than a full season potato crop as high rates of nitrogen may delay tuber set and lead to excessive vine growth that is difficult to terminate prior to harvest. Bintje and Ciklamen potato cultivars were grown with preplant soil nitrogen levels of 34 to 38, 67, and 101 kg N ha^-1 in 2013 and 2014 near Paterson, Washington. Nitrogen rate had little impact on the number of tubers and stems per plant of both cultivars, but increasing nitrogen rate tended to increase leaf area of both cultivars. Vine desiccation of Bintje with diquat was less complete as nitrogen rate increased, while Ciklamen vine kill was reduced by higher nitrogen in 1 of 2 years. Tuber skinning injury, tuber weight loss, and tuber size distribution were not affected by nitrogen rate. Tuber skinning injury and tuber weight loss were reduced in both cultivars by harvesting at 4 weeks after initial vine kill compared to harvesting at 2 weeks after vine kill. Total tuber yield was lower for both Bintje and Ciklamen in 1 of 2 years at the 34 to 38 kg N ha^-1 rate. Tuber nitrogen and zinc levels tended to increase with increasing nitrogen rates, while most other nutrients, vitamin C, total phenolics, and antioxidant capacity showed little response. It appears that 67 kg N ha^-1 provides adequate nitrogen to produce a good tuber set and yield of small tubers while not producing excessive vine growth that may be more difficult to kill.     

脱毒小薯原原种粒级、密度、品种熟性对一级原种繁殖的影响

采用马铃薯脱毒小薯不同粒级、不同密度、不同品种熟性三因子三水平正交试验，研究了原原种对一级原种的产量、单株平均结薯数及＜２５ｇ小薯所占比率的影响。结果表明：当早熟、结薯少、薯块均匀的品种原原种播种密度在１．２万株／亩以上，晚熟和中晚熟、结薯较多薯块不均匀的品种在１．０～１．２万株／亩之间，且播种粒级大于０．５ｇ／粒时，一级原种繁殖方可收到既高产又具较高的繁殖系数和较低用种量的效果。     

Effects of Nitrogen Fertilizer Application Time on Dry Matter Accumulation and Yield of Chinese Potato Variety KX 13

Application time of nitrogen (N) fertilizer can significantly influence the yield and quality of potato tubers. The objective of this experiment was to assess the effects of N application time on dry matter accumulation in foliage and tubers, as well as on marketable tuber ratio, dry matter concentration, and specific gravity of the Chinese cultivar KX 13. The four treatments were as follows: all the 150 kg?N?ha^?1 applied at planting (T1); 100 kg N ha^?1 applied at planting and 50 kg N ha^?1 applied 1 week before tuber initiation (20 days after emergence, DAE) (T2); 100 kg N ha^?1 applied at planting and 50 kg N ha^?1 applied 1 week before tuber bulking stage (35 DAE) (T3); and 100 kg?N?ha^?1 applied at emergence and 50 kg N ha^?1 applied 1 week before tuber bulking stage (35 DAE) (T4). For all treatments, 90 kg P₂O₅ ha^?1 ((NH₄)₂HPO₄) and 150 kg K₂O ha^?1 (K₂SO₄) were applied at planting. Thirty tons per hectare of marketable tuber yield was achieved with T3, while 23 t ha^?1 marketable yield was achieved by applying all 150 kg N ha^?1 at planting (T1). Relative to treatment T1, T3 also significantly increased harvest index (HI) from 0.76 to 0.86 and marketable tuber ratio from 64.8% to 79.2%. Applying N at planting in conjunction with dressing at 20 DAE (T2) gave a high marketable tuber ratio (74%) and HI (0.86), but the lower total tuber yield led to a lower marketable tuber yield. Without N application at planting (T4), N dressing did not increase the yield and HI. Treatments with N dressing had no significant effect on specific gravity or dry matter concentration of tubers.     

The effect of density on tuber yield in plants grown from true potato seed in seed beds during two contrasting seasons

The production of potatoes from true seed was studied in direct-sown seed beds during both winter and summer seasons in Lima, Peru. After emergence, seedlings were thinned to give 6, 12, 24, 48 or 96 plants per m². In all five density treatments plants were arranged in a square configuration. In both seasons, increasing plant density significantly increased total tuber number as well as tuber weights in the grades 1–5 g, 5–20 g and 20–40 g. The yield of tubers larger than 40 g was similar in all densities. In the warm summer season, tuber number was significantly reduced and mean tuber weight was 56% greater compared with that in the winter season. The potential of producing consumer potatoes from true seed in seed beds in warm climates is discussed.