Production of potato minitubers by repeated harvesting: Effects of crop husbandry on yield parameters

Summary Minitubers can be produced in large quantities by repeated harvesting of tubers from in vitro propagated plantlets at 4, 7 and 10 weeks after transplanting to the glasshouse at high plant densities. Yield parameters of minitubers can be manipulated by crop husbandry. By supplying nutrients or using a square plant arrangement, minituber yield increased. Effects on numbers of tubers were cultivar-dependent. Changing plant density from 50 to 800 plants per m² or the minimal diameter of harvested tubers from 5 to 12 mm did not significantly affect tuber yield per m². Higher plant densities resulted in more tubers per m² but fewer tubers per plant. Removing smaller tubers greatly increased the number of small tubers, but did not affect yield and number of tubers in larger grades. Crop husbandry techniques affected minituber yield mainly through their effects on leaf area duration, and the number of minitubers through their effects on growth of tubers to a harvestable size.     

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 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.     

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.     

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.     

Greenhouse production of potato (Solanum tuberosum L. cv. Désirée) seed tubers using in vitro plantlets and rooted cuttings in large propagation beds

Summary Seed tuber production fromin vitro potato plantlets and cuttings was conducted in large propagation beds in a greenhouse. Propagules of wholein vitro plantlets (WIP), plantlets with apical (ACR) and lateral (LCR) cuttings removed, the rooted apical cuttings (RAC) and rooted lateral cuttings (RLC) were planted at three densities of 25, 49 and 100 plants per m². The plantlets from which cuttings were removed (ACR and LCR) produced more tubers than the rooted cuttings (RAC and RLC); however, the most tubers were produced by WIP. RAC produced highest tuber yields followed by WIP and RLC. Intact WIP and plantlets with cuttings removed (ACR and LCR) produced twice as many tubers <40 g as those from rooted cuttings (RAC and RLC). The yield (kg/m²) as well as the number of tubers per m² increased with the increasing planting density within the densities tested.     

Influence of plant spacing on potato (Solanum tuberosum L.) morphology,growth and yield under two contrasting environments

Summary In experiments at a temperate (43^oN) and a tropical (14^oN) location, closer plant spacing decreased stem branching, root growth, and mean tuber size but increased tuber yields per ha. Closer spacing increased plant height at the temperate site but decreased it at the tropical site where canopy cover did not reach 100%. The increased branching at the wider spacing did not compensate for fewer plants/m². Total and tuber weight per plant increased with wider spacing and was much greater under temperate than tropical conditions. Tuber yield/stem also increased with lower stem densities. Although these results provide initial data for modelling, the contrast between the two environments and interactions between spacing and cultivar suggest that further experiments need to be done with a range of cultivars at intermediate locations.     

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.     

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.     

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.     

Branch development responses to planting density and yield stability in soybean cultivars

The objective of this study was to elucidate variability among soybean cultivars in yield response at different planting densities in reference to branch development. We investigated the main stem and branch seed yield and the branching characteristics of determinate Hokkaido and indeterminate US cultivars at the Rakuno Gakuen University in Ebetsu. In 2009 and 2010, two Japanese and two US cultivars were grown at three densities from 9.5 to 20 plants m^?2. In 2011 and 2012, three cultivars from each region were cultivated at three densities from 8.3 to 22.2 plants m^?2. The seed yields of the US cultivars at densities of 16.7 plants m^?2 or less were markedly higher than those of the Hokkaido cultivars, showing that their yield is less sensitive to lower planting density than Hokkaido cultivars. The difference in yield in response to planting density among cultivars was closely associated with a larger increase in branch seed yield with lower planting density, which effectively compensated for the decrease in main stem number per unit land area. The variability of branch development in response to planting density (branching plasticity) was quantified by correlating branch performance with plant spacing (land area per plant). Some US cultivars exhibited greater branching plasticity than Japanese cultivars with similar growth duration. Results of this study suggest soybean cultivar differs in responsiveness to varied planting density through different branching plasticity.     

柳叶刺蓼对玉米生长的影响及其经济阈值研究

柳叶刺蓼是吉林省春玉米田的恶性杂草,严重危害玉米生长发育,降低玉米产量。在大田条件下采用添加柳叶刺蓼密度系列试验和拟合函数关系模型方法,研究柳叶刺蓼与玉米的竞争关系。结果表明,在柳叶刺蓼的竞争干扰下,玉米株高、茎粗、穗长、单穗重、百粒重及产量均随柳叶刺蓼密度的增加而降低,空秆率增加。幂函数y=2.947x~(0.855)能较好地拟合玉米产量损失与柳叶刺蓼密度之间的关系(R~2=0.983;F=287.355;P=0.000 1)。玉米田柳叶刺蓼人工除草的经济阈值为3.97~5.02株/m~2,90%莠去津可分散粒剂或20%氯氟吡氧乙酸乳油化学防除柳叶刺蓼的经济阈值分别为0.45~0.58和0.53~0.67株/m~2。     

Varying Nitrogen Concentrations to Optimize Basic Seed Potato Minitubers Production in a Three-Phase Hydroponic System

In hydroponics, nutrient management is the limiting factor to obtaining optimal production, and nitrogen (N) is the key component to consider when optimizing nutrient management in these types of systems. The objective of this study is to evaluate different combinations of N fertilizer concentrations in order to optimize the yield of basic seed potato minitubers in a three-phase hydroponic system. Treatments consisted of five combinations of N concentrations, applied before and after 21 days after plant transplant as follows, respectively: 1) 13 and 13, 2) 13 and 0, 3) 13 and 7.8, 4) 13 and 16, and 5) 13 and 26 mmol L^?1. Propagation was performed by transplanting 3–4 cm potato plantlets cv. Agata from sprouts. There were significant effects of N treatments on all measured variables (root, leaf, stem, and plant dry weight and minituber number and weight). To obtain the maximum minituber number yield, 9.51 minitubers/plant, corresponding to 67 minitubers/m², post 21-day adjusted N concentration was 18.4 mmol/L. Treatment 4 promoted higher basic seed potato minituber yield in a three-phase hydroponic system.     

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.     

Optimum plant density of Digitaria eriantha for herbage accumulation and hydrological performance in a summer dominant rainfall zone

In the frost‐prone, summer dominant rainfall zone of northern NSW and southern Queensland, sown tropical grass pastures commonly establish with plant densities >26 plants per m², yet the optimum density for maximum herbage accumulation and hydrological performance is not known. A replicated, field study was established in northern NSW in November 2011, using five densities of Digitaria eriantha (digit grass): 0, 1, 4, 9 and 16 plants per m² and a range of agronomic and hydrologic measures was assessed. The results showed that the largest differences between plant densities in herbage accumulation, root depth, soil water extraction and rainfall refill efficiency occurred during the first 2 years; after this time, digit grass pastures with densities of ≥4 plants per m² responded similarly. Plant frequency increased with increasing plant density but the treatments did not converge. During the first two growing seasons, there was no effect of plant density on water use efficiency; however, by the third growing season, pastures with 4 plants per m² were the most water efficient. Overall, the results indicated that 1 plant per m² was too low to efficiently use resources, 16 plants per m² utilized the resources quickly then tended to stall, while 4–9 plants per m² was a good compromise between agronomic and hydrological response, achieving both herbage accumulation and sustainability goals. A practical management advantage of pastures with 4–9 plants per m² is they allow soil water resources to be available for a longer period of time and potentially provide the opportunity to establish legumes in the ensuing 24‐month period.     

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。     

The competitive ability of different chickpea (Cicer arietinum) genotypes against Polygonum aviculare under field conditions

Polygonum aviculare L. is a troublesome weed in chickpea cultivated in the Mediterranean environment of Central Italy. A 2-year field study was carried out to evaluate the competitive ability and the yield response of different chickpea genotypes against P. aviculare. Experimental treatments consisted in six chickpea genotypes (Alto Lazio, C1017, C133, C134, C6150 stable lines and cultivar Sultano) cultivated in weed-free conditions and with P. aviculare at four densities (4, 8, 16, 32 plants m⁻²). The competitive ability of chickpea against P. aviculare was assessed on the basis of (i) the relative biomass total (RBT); (ii) the competitive balance index (Cb), and (iii) the competitive index (CI). The chickpea seed yield in weed-free conditions ranged from 2.6 to 2.1 t ha⁻¹ of DM and was higher in C6150 and Sultano. P. aviculare caused an average chickpea seed yield loss of 14, 46, 74 and 88% at the density of 4, 8, 16, 32 plants m⁻² compared to the weed-free crop. The relationship between the P. aviculare density and the percentage of chickpea yield loss was described by the rectangular hyperbola model with the asymptote constrained to 100% maximum yield loss. The estimated coefficient I (yield loss per unit density as density approaches zero) was lower in C133, Sultano, and C1017. RBT was higher than 1 in all chickpea genotypes at 4 plants m⁻² of P. aviculare, while at higher P. aviculare densities it was similar to 1 suggesting that there is no resource use complementarity between chickpea and the weed. Generally, at the density of 50 plants m⁻² the chickpea crop was more competitive than P. aviculare at 4 plants m⁻² (Cb > 0), equally competitive at 8 plants m⁻² (Cb = 0), and less competitive at 16 and 32 plants m⁻² (Cb < 0). No chickpea genotype achieved the objective of combining a high seed yield potential and a great competitive ability against P. aviculare. C6150 and Sultano had a high seed yield production in weed-free conditions, but they were poorly competitive against P. aviculare at intermediate and high weed infestation, while C1017 showed a satisfactory level of Cb and CI at all P. aviculare densities although its seed yield was the lowest in weed-free conditions. However, the results suggest that, from an agronomical point of view, P. aviculare plant density should be less than 4 plant m⁻² in order to prevent severe chickpea seed yield loss in field conditions.     

Population density studies with Russet Burbank I. Yield/stem density models

Two reciprocal polynomial models were used to quantify yield/stem density relationships in the Russet Burbank cultivar y^?θ = α + β? and y^?1 = β₀ + β₁? + β₂?² where y = yield per plant; ? = stems m^?2 and β₀, β₁, β₂ and α, β, and θ are fitted parameters. The use of a systematic design allowed characterisation of the yield/density response surface over a wide range of densities (1.8 to 20.0 plants m^?2) without involving experiments of impractical size. The effect of both seed size (30, 40, 50, 60 gm) and type (cut or whole) on the relationship was studied. Both models provided excellent statistical fits for marketable yield data, while the former model gave a similar fit for total yield data. The form of the relationship was not influenced either by seed size or type. Total yield was asymptotically related to stem density while marketable yield was parabolically related.     

Production and use of seedling tubers from true potato seed (TPS) for potato cultivation in Italy

Summary The effect of varying plant population on the production of tubers from potato seedlings was investigated during 1992 and 1993 using three different plant densities: 35, 70, 100 plants/m². Increasing the plant population significantly increased the number of tubers produced, but no significant difference was found between the plant densities of 70 and 100 plants/m². The seedling tubers produced in nursery beds were tested in the field for ware potato production using different sized tubers. The best performances were obtained using tubers 30–40 mm. Significant differences were evident among the 7 true potato seed (TPS) families used, but data grouped by type of cross did not indicate any significant difference between 4X×4X and 4X×2X crossing groups.     

Field performance of potato minitubers with different fresh weights and conventional seed tubers: Multiplication factors and progeny yield variation

Summary Multiplication factors and progeny yield variation in crops from minitubers of five weight classes (ranging from 0.13–0.25 g to 2.00–3.99 g) and conventional seed tubers were studied in field experiments in three years. Multiplication factors were calculated as the number and weight of progeny tubers produced per planted tuber or per unit planted tuber weight. They were lower for the lighter minitubers when calculated per tuber and higher when calculated per weight. Yield variation was described by coefficients of variation for the number and weight of progeny tubers produced. Variation over individual plants of a crop was higher in stands from the lighter minitubers. Variation over plots within a field was sometimes higher for the lighter minitubers, but variation over years was similar for all minituber classes. Variation over plots in progeny tuber weight was higher for minitubers than for conventional tubers.