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.     

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.     

Influence of time of application of maleic hydrazide on the yield and quality of Russet Burbank potatoes

A three-year study in central Wisconsin with timed foliar applications of maleic hydrazide at 3 lb/A (3.36 kg/ha) resulted in an improvement in quality and a favorable alteration in the shape of tubers of the Russet Burbank potato variety. Application in early and mid-July resulted in an increase in yield of U.S. 1 tubers and reduced yield of malformed tubers. Over 40 percent fewer misshapen tubers were produced when applications of maleic hydrazide were made during July when compared with tubers from untreated plants. Applications made in midor late July resulted in tuber development with a more favorable length to diameter ratio of U. S. 1 tubers, again compared with tubers from untreated plants. Maleic hydrazide applied in early or mid-June resulted in severely reduced yield and increased incidence of misshapen tubers. When applied in July or early August, no effect on tuber specific gravity was found. Maleic hydrazide functioned as an effective sprout inhibitor on tubers from all treatment dates except when applied in early June.     

The productivity of oats and berseem clover intercrops. II. Effects of cutting date and density of oats on annual forage yield

Annual forage yields of intercrops of berseem clover (Trifolium alexandrinum L.) and oats (Avena sativa L.), as affected by timing of initial harvest and sowing rate of oats, were investigated. Berseem clover was intercropped with oats at 0, 30, 60, 90 and 240 plants m^?2 of oats in 1999 and 2000 in Alberta, Canada. Cutting date treatments involved initial harvest at 10‐d intervals between 35 and 88 d after planting (DAP), and one or two subsequent harvests of regrowth. Total intercrop dry‐matter (DM) yield averaged 12·9–13·3 t ha^?1 with proportions of 0·21–0·43 of berseem clover in the forage. Treatments with an initial cut at the silage stage of oats (76 DAP in 1999, 88 DAP in 2000, at about soft‐dough stage of oats) had greater yields of oats, lower yields of berseem clover, and lower proportions of berseem clover in total annual yields than treatments with an earlier initial cut. Total crude protein (CP) yield was greater with an initial cut at 65–66 DAP than with a silage‐stage initial cut. With an initial cut at 35 DAP (before stem elongation of oats) or after 65 DAP (after heading of oats), yield potential of oats was sometimes reduced compared with silage‐stage treatments, but this was balanced by a greater yield of berseem clover. The impact of harvest timing on total yield decreased as the proportion of berseem clover in the intercrops increased. With decreasing density of oats, DM yield of first‐cut intercrops and total DM yield of oats decreased, while regrowth and total DM yields of berseem clover increased. Intercrops with oats at 60 plants m^?2 had equal or greater total DM and CP yields than intercrops with 240 plants m^?2 of oats. For intercrops with oats at 60 plants m^?2, with initial cuts at 65–66, 75–76, or 88 DAP, yields of regrowths were 0·30–0·35, 0·16–0·26 and 0·09 of the total yield respectively. Oats–berseem clover intercrops showed potential to manipulate the pattern of annual forage yield and to provide flexibility of harvest without reducing annual yields.     

Yield and quality of Russet Burbank potato as influenced by interactions ofRhizoctonia,maleic hydrazide,and PCNB

Soil treatment with pentachloronitrobenzene (PCNB) at 22.4 kg/ha a.i. reduced symptoms of theRhizoctonia disease (Rhizoctonia solani Kühn) on potato (Solarium tuberosum L.) and resulted in significant increases in the numbers of stems and stolons. With disease control there was no effect on either total or U.S. #1 yield, but decreases of tuber size were evident and effects were observed on grade. Yield of malformed tubers was reduced by 35%, but this benefit was counteracted by a 41% increase of undersized tubers. Among U. S. 1’s, yield of non-size A’s (113 to 170 g) were increased by 22%, while tubers in optimum size ranges for french fries and bakers (> 284 g) were decreased by 24%. No effect was observed on carton sized tubers (170 to 369 g). Foliar sprays of maleic hydrazide (MH) applied on either of several dates (23 July, 2 Aug., 13 Aug.) at 3.4 kg/ha a.i. reduced total yield by 4.9 to 5.7%, but yields of U.S. #1 potatoes or sizes > 170 g were unaffected. Treatments with MH on either 23 July or 2 Aug. reduced yield of undersized potatoes by 23%. MH treatments did not interact with PCNB treatment to change either total yield or size, but adverse effects on U.S. #1 yields were indicated. MH treatments applied on either 2 Aug. or 13 Aug. reduced U.S. #1 yields among PCNB treated plots by 7 to 10%. MH reduced length/width ratios and, depending on date of application, increased specific gravity. PCNB did not influence tuber shape or specific gravity, but a significant reduction of standard deviations among length/width ratios indicated greater uniformity of shape with treatment.     

Tillage and seed-sprouting strategies to improve potato yield and quality in short season climates

Management practices that accelerate crop development and allow earlier harvest would be beneficial in short-season potato (Solanum tuberosum L.) production areas. Yield and quality of the potato cultivar ‘Russet Burbank’ were evaluated in a 2-yr study in northern Maine to determine effects of soil tillage and seedsprouting treatments designed to dry soil early in the spring and hasten seed emergence. The tillage treatments, consisting of fall raised bed (RB), fall ridge till (RT), and spring chisel plow (CH), were tested in combination with green-sprouted and non-sprouted seed tubers on a Caribou gravelly loam (coarse-loamy, mixed, frigid,Typic Haplorthod). Plants from green-sprouted seed emerged earlier than from non-sprouted seed tubers (87%-96% vs 21%-37%, respectively, at 18 days after planting [DAP] in 2000; and 73%-88% vs 18%-23%, respectively, at 20 DAP in 2001). Green-sprouted seed tubers in RB yielded 4.6 to 5.9 T ha^-1 more than nonsprouted seed tubers in RB. However, non-sprouted seed tubers yielded higher than green-sprouted seed tubers in RT by 2.9 to 4.2 T ha^-1 and in CH by 1.1 to 4.1 T ha^-1. Similarly, green-sprouted seed tubers in RB and nonsprouted seed tubers in RT and CH produced higher marketable yield, greater tuber length, and greater tuber diameter than the corresponding seed-sprouting treatment. In the comparatively wetter year (2000), the use of green-sprouted seed tubers in RB significantly increased total and marketable yields, and produced longer and larger tubers than all other treatments. However, in 2001 (relatively dry year), yield and quality from green-sprouted seed tubers in RB did not differ from non-sprouted seed in RT or CH. Green-sprouted seed produced fewer sunburned and rotten tubers, but more misshapen tubers than non-sprouted seed in RB tillage. The technique of producing Russet Burbank potatoes in raised beds is a promising system in regions with short growing seasons for enhancing early soil drainage during spring and improving soil water retention during critical periods of crop growth and development.     

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.     

Soybean response to gibberellic acid I. Time of application relative to emergence

Soybean (Glycine max (L.) Merr.) cultivars planted too late or too early may be subjected to short photoperiods that can cause plants to flower prematurely and produce many pods at lower nodes near the soil surface. This can result in considerable mechanical harvest loss even if yield potential is good. The purpose of this experiment was to study the effect of gibberellic acid (GA), applied on four soybean cultivars at different times relative to emergence, on internode length, yield, and agronomic characteristics. Seven timings (−1, 0, 1, 2, 3, 4, and 5 days after emergence (dae)) of GA application at 25 g ha⁻¹ were tested. Field experiments were conducted for 2 years at Ona (27° 25′N), and 1 year at Gainesville (29° 40′N), Florida. Cultivars were main-plot treatments, and time of GA application plus a replicated control were subplots. At Ona, ‘Amsoy 71’ (Maturity Group (MG) II), ‘Williams’ (MG III), ‘Cutler 71’ (MG IV), and ‘Essex’ (MGV), were seeded in early March in 250-mm row spacings to a final population of 8 plants m⁻¹ of row. At Gainesville, the Williams cultivar was seeded on March 15 in 350-mm rows at 20 plants m⁻¹.Applied GA at +4 or +5 dae resulted in a 40–50-mm increase in length of the hypocotyl, plus internodes 1 and 2 were increased 49–67% compared to the control, but did not affect total plant height. Length of upper internodes was slightly reduced by the GA treatments. The timing of GA application had no effect on seed quality, seed weight, or total seed yield. Approximately 10% of the total seed yield came from the lower three nodes (cotyledonary, unifoliate, and first trifoliate). These results indicate that GA can increase the basal stem elongation of soybean by an average of 50 mm, which could aid commercial harvesting.     

Field and laboratory studies on the control of nematode and aphid virus vectors in potatoes by pesticides applied as side-bands

Field trials were undertaken with a prototype machine to determine whether virus vector nematodes and aphids were controlled by the carbamoyl oxime pesticides aldicarb (Temik 10G) and oxamyl (Vydate 10G) incorporated into the ridge of a growing potato crop. The treatments were applied at tuber initiation (7 or 8 weeks after planting) and were compared with similar amounts of the same pesticides applied in-furrow at planting. All aldicarb treatments significantly decreased the incidence of tobacco rattle virus spraing transmitted by trichodorid nematodes. However, the side-banded treatments were less effective than the in-furrow treatments applied at similar rates. Numbers of aphids infesting the crop were significantly and similarly decreased by both methods of application. Pesticide treatments did not significantly increase yield, and total tuber yields from the standard infurrow and the side-banded treatments were similar. To provide further information on the efficacy and movement of carbamoyl oxime pesticides between different isolated root systems on single parent tubers, replicated pot experiments were made. Parent tubers were maintained with a physical barrier between a root system treated with pesticide and another left untreated. In a nematode bioassay Meloidogyne incognita was added to both the treated and untreated root systems to test for the presence of nematicidal activity. The number of root-galls which developed in 8 weeks were counted. Both aldicarb and oxamyl decreased the number of galls on the treated root system. However, little evidence of translocation through the parent tuber was found, the number of galls on the untreated roots being largely unaffected. The roots of plants grown from tubers treated in a similar manner were tested for the presence of aldicarb and oxamyl residues by gas-liquid chromatography. No translocated pesticide was detected. In aphid bioassays, using excised leaves, 3–5 weeks after applying aldicarb at 20 and 40 mg a.i./pot or 4–9 weeks after applying aldicarb at 80 mg a.i./pot, aphid survival was always significantly less on treated stems than on non-treated stems growing at the opposite end of the tuber or on control stems growing from untreated tubers. However, there was some evidence for translocation through the parent tuber as fewer aphids survived on leaves from non-treated stems than from untreated control stems.     

Maleic hydrazide effects on tuber yield, sprouting characteristics, and french fry processing quality in various potato (Solanum tuberosum L.) cultivars grown under argentinian conditions

Field trials were carried out during 1995–1998 in commercial crops of five potato cultivars grown at several locations in Argentina to test maleic hydrazide (MH potassium salt, 36% ) effects on tuber yield, sprouting characteristics, and processing quality. MH was applied at growth stage IV, when developing tubers were 40–70 mm, at 9, 10,12 and 14 1 ha^-1 in single or split treatments. MH treatments did not produce phytotoxicity symptoms in the foliage and did not decrease tuber yield. MH increased tuber yield in Kennebec, Russet Burbank and Shepody in several experiments, while not in Atlantic and Ranger Russet. MH treatments delayed initial sprouting date and inhibited sprout growth during storage periods up to 8 months, which resulted in lower weight losses due to sprouting. Tuber dry matter content and fry color were similar or in some cases improved due to MH treatments, while no consistent results were found regarding reducing sugar content.     

Effects of nitrogen fertilization and in-row seedpiece spacing on yield of three potato cultivars in Prince Edward Island

AC Novachip and NorWis were recently introduced as new potato (Solanum tuberosum L.) chip cultivars on Prince Edward Island (P.E.I.), Canada. Variability of nitrogen application and in-row seedpiece spacing, required for maximum yield, exist among cultivars presently grown in P.E.I. This study was conducted to determine the N rate and in-row seedpiece spacing required for optimum production of AC Novachip and NorWis compared to the standard cultivar Norchip, and also, to determine the effects of treatments and harvest dates on AC Novachip. Treatments included N applied at 90, 134, and 179 kg/ha with in-row seedpiece spacings at 20.3, 25.4 and 30.5 cm. In addition to the 120 day harvest for all three cultivars, treatments for AC Novachip were also harvested at 80 and 100 days after planting. For the 120 day harvest, yield of Canada No. 1 size tubers was higher for NorWis compared to Norchip while yields for AC Novachip and Norchip were similar. Nitrogen application had no effect on yields of AC Novachip. Similar to Norchip, increasing the rate of applied N more than 134 kg/ha resulted in little or no increase in yields of NorWis. Yields of Canada No. 1 size tubers decreased as in-row spacing increased for AC Novachip and were greater at 25.4 compared to 30.5 cm spacing for Norchip. In-row seed-piece spacing had no affect on Canada No. 1 size tuber yields of NorWis. Increasing the days to harvest increased the yields of AC Novachip. Nitrogen rate or in-row spacing had no effect on Canada No. 1 yields of AC Novachip at the 80 and 100 day harvests. The results of this study suggest that little gain in yield of Canada No. 1 size tubers for NorWis, similar to the standard cultivar Norchip, can be obtained with N application more than 134 kg/ha or for AC Novachip by increasing the rate of N from 90 to 179 kg/ha. Unlike NorWis yields of AC Novachip and NorWis are reduced when in-row seedpiece spacing is increased from 25.4 to 30.5 cm.     

Influencing seed tuber yield of Ranger Russet and Shepody potatoes with gibberellic acid

Freshly-cut seed pieces of the potato cultivars Ranger Russet and Shepody were dipped in 0, 0.5, 1 or 2 mg/1 Gibberellic Acid (GA₃) prior to planting. GA₃ treatments increased stem and tuber numbers per hill of both cultivars and shifted tuber size profile toward the production of more seed-sized (up to 226 g) tubers and fewer large (greater than 340 g) tubers. The effect of GA₃ on reducing average tuber size was similar for the two cultivars. Total tuber yields were not affected. A 2 mg GA₃/1 seed piece dip decreased the yield of US#1 tubers in Ranger Russet primarily due to a significant increase in yield of tubers less than 226 g. Also, yields of culls were greater after a 1 mg GA₃/1 seed piece treatment, suggesting Ranger Russet is sensitive to this concentration of GA₃. One and 2 mg GA₃/1 seed piece dips to Shepody increased yields of tubers less than 113 g by 93% and reduced the yield of tubers greater than 340 g by 25% to 50%. GA₃ at 1 to 2 mg/1 may be useful in the production of seed potatoes with the cultivar Shepody which tends to produce many large tubers.     

Assessment of Opportunities for Burundian Small-Scale Potato Farmers to Increase Productivity and Income

From 2014 through 2016, on-farm experiments were carried out in three provinces surrounding Bujumbura town in Burundi to improve the low potato (Solanum tuberosum) yields, which currently stand at about 6 t ha^?1. It was hypothesised that in rain-fed conditions, improved varieties, healthier seed tubers, pre-sprouting in light, proper fertilisation and protection from late blight attack would improve yield and quality, such as tuber weight, tuber size and lower brown rot incidence. The treatments in the on-farm trials at five farms in each of three sites (15 replicates) were applied in two seasons, giving 30 replicates in 580 plots. The following treatments were compared with growers’ current practices: introduction of two new varieties, use of early generation seed from a rapid multiplication scheme, earlier harvesting of a seed crop, seed storage in a diffused light store, and research-based timing and dose rate of fertilisers and fungicides. Marginal rates of return on investments were calculated at farm level and current and tested alternative technologies were compared. Costs and benefits of applying such techniques were calculated. An improved variety contributed up to 20% yield increase and healthier seed 80%. Early harvesting reduced yield by 30% and reduced incidence of brown rot in the current season, but increased it (from 21 to 39%) in the following season when tubers were replanted. Diffused light storage, alternating contact and systemic fungicide application, and application of chemical fertilisers resulted in 30, 50 and 60% yield increases, respectively. It was shown that it is possible to double yields and economic returns (marginal rates of return) under the growing conditions in Burundi when growers plant healthy pre-sprouted seed of a new variety and apply chemical fertilisers and fungicides.     

赤霉素对不同甜叶菊品系主要农艺性状、糖苷含量及产量的影响

喷施不同浓度的赤霉素(GA)于4种不同类型的甜叶菊品系叶表面,考察外源激素处理对其主要农艺性状、糖苷含量及糖苷产量的影响。结果表明:(1)赤霉素处理组同对照组相比,处理后株高、节长显著增长,且节间伸长效果主要集中在茎秆中部,叶长显著变短、叶宽显著变窄,叶长宽比值增大,单株干叶产量下降;赤霉素处理间,表现出一定的浓度效应,即随着赤霉素处理浓度增大,表现出一定的株高增加,叶长、叶宽减小的趋势。(2)就提高植株糖苷含量而言,100 mg/L的GA处理(A1)提高了SR1型甜叶菊的RA苷的含量,100 mg/L和300 mg/L GA提高了SR3品系ST苷含量,300 mg/L GA提高了SR2品系ST苷含量。(3)就糖苷产量而言,由于各处理下其干叶产量均显著下降,最终导致所有GA处理中,除300mg/L的GA处理显著提高了SR2的ST苷产量外,其余GA处理均不利于甜叶菊RA或ST糖苷产量的提高。     

The productivity of oats and berseem clover intercrops. I. Primary growth characteristics and forage quality at four densities of oats

Berseem clover (Trifolium alexandrinum L.) was sown as an intercrop with oats (Avena sativa L.) at 0, 30, 60, 90 and 240 oats plants m^?2 in May in 1999 and 2000 in Alberta, Canada. Forage yield and quality were measured at 10‐d intervals between 35 and 88 d after planting (DAP). Yield is defined as the biomass above 6 cm of the soil surface. The dry‐matter (DM) yield of berseem clover in sole crops increased by 5–10 g m^?2 d^?1 between 35 and 55 DAP and then increased by 21–28 g m^?2 d^?1 between 55 and 75 DAP. The DM yields of oats sown at 240 plants m^?2 increased by 26–28 g m^?2 d^?1 over the whole period from 35 to 75 DAP. Oats were the dominant component in the intercrops, even at low densities of oats. Berseem clover grown with 60 oats plants m^?2 received only 0·24 of the incident light when shading by oats peaked at 65 DAP. DM yields of berseem clover in intercrops with 60 oats plants m^?2 averaged 0·14–0·32 of the yields of berseem clover sole crops. Between 35 and 88 DAP in 2000, the crude protein (CP) concentration of berseem clover sole crops declined linearly from 310 to 180 g kg^?1 DM, and the CP concentration of oats exhibited a quadratic response, declining from 350 g kg^?1 DM at tillering to 110 g kg^?1 DM at the soft dough stage. The mean CP concentration of berseem clover in intercrops with 60 oats plants m^?2 was 25 g kg^?1 less than in berseem clover sole crops, indicating that competition by oats reduced the CP concentration of berseem clover. At later sampling dates, CP and DM yields of intercrops with oats at 60 plants m^?2 equalled those with oats at 240 plants m^?2. The addition of berseem clover to oats in intercrops at 60 oats plants m^?2 reduced the neutral‐detergent fibre concentration by 30 g kg^?1 DM compared with oats alone. Oats were very competitive as a companion crop for berseem clover. Adding berseem clover to oats increased forage quality and may provide for increased intake and digestibility of forage to support higher livestock productivity.     

Some unique benefits with sudangrass for improved U.S. #1 yields and size of Russet Burbank potato

Three studies provided additional knowledge of beneficial effects of sudangrass for yield and quality increases of the Russet Burbank potato. Two of these studies showed significant increases of both U.S. #1 and smooth tubers > 280 g following green manures of sudangrass. These sudangrass (HS-33) effects did not differ from a sorghum-sudan hybrid (Trudan-8). When a sudangrass green manure was compared with a fallow treatment, results of the first study showed mean yield increases of 36% for U.S. #1 tubers > 280 g and yields of a second study by 34% for U.S. #1 tubers. This same sudangrass treatment outperformed green manures of either Austrian winter pea, barley, or sweet corn by increased U.S. #1 yields that ranged from 27% to 61%. By several lines of evidence, these benefits were found to extend beyond the effect of Verticillium suppression. Soil N was significantly increased following green manures of sudangrass, and these increases were in turn negatively correlated with wilt incidence and positively correlated with yields of both U.S. #1 tubers and tubers > 280 g. Additional benefits also included significant increases of tuber grade percentages for marketable tubers and of smooth tubers > 280 g. Benefits from sudangrass green manures beyond the effects of Verticillium suppression became further evident following a greenhouse study that involved field soil and sudangrass that had been grown in the same field. This study corroborated both field experiments by showing increased yields with green manures of sudangrass that approximated 5.5 t ha^-1 dry wt. As with the field studies, these yield benefits also extended beyond the effects of Verticillium suppression and were closely associated with significant increases ofFusarium equiseti, F. oxysporum, andF. solani. Throughout all studies, sudangrass green manures significantly increased microbial activities with increased populations ofFusarium spp. and increased concentrations in soil of mineralizable N, organic P, K, Mn, along with the percent soil organic matter -all factors that could have contributed to significant increases of yield and quality.     

Effect of Storage and Pre-sprouting Regimes on Seed Potato Performance in Norway

Physiological quality affects vigour and yield potential of potato seed tubers. Under short-season conditions, a seed tuber should preferably produce a short cycle and mature crop. The aim of the current studies was to assess how various storing and pre-sprouting treatments affect growth vigour and yield formation. Results showed that different low-temperature storage regimes before pre-sprouting treatments had no clear effects although some minor differences between treatments occurred. For pre-sprouted (‘green’-sprouted) seed tubers, results from field trials in southern Norway (2007–2008) showed that emergence of cvs Asterix and Saturna improved significantly compared to unsprouted seed. Total yields increased significantly for both cultivars in 1 out of 2?years. For Saturna, a major increase in number of tubers per plant resulted in larger proportions of smaller-size grades and thus lower marketable yields. In other trials (northern Norway, 2006–2007), varying duration of pre-sprouting did not affect growth vigour and yield. For number of tubers and size grades, the results varied significantly between pre-sprouting durations, but differently among trials, so no clear conclusions can be drawn. In one of the two trials, increased duration of pre-sprouting resulted in higher proportions of the smaller sizes at the expense of large tubers. Different levels of temperature sums during pre-sprouting (ca. 200 or 400?day-degrees >4?°C) did not affect seed performance. In conclusion, our studies showed that pre-sprouting may improve growth vigour and increase the proportion of smaller grade sizes.     

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.     

Effects of nitrogen,phosphorus and potassium fertilizer treatments on weight loss and changes in chemical composition of potato tubers stored at 4°C

Summary Pot and field experiments were carried out to test fertilizer treatments on the behaviour of potato tubers stores at 4°C and ≥90% relative humidity for 6 months. Weight losses (separated into water and dry matter) were enhanced after N and K fertilization and decreased by increasing P supply. Glucose and fructose contents were reduced at harvest by high N-fertilizer rates compared to no or low fertilization, but throughout storage reducing sugar accumulation was increased, sucrose reduction was decreased and ascorbic acid was increased. K fertilization affected the chemical composition of the tubers somewhat similar to that of nitrogen fertilization. High initial nitrate content of the tubers seemed to be increased and low nitrate values were decreased during storage. The tubers from pot experiments showed similar changes but of greater magnitude.     

Efficacy of metam sodium for controllingVerticillium dahliae prior to potato production in sandy soils

The efficacy of metam sodium (MS) for controlling Verticillium wilt of potato was evaluated in two field experiments conducted in a sandy soil, heavily infested withVerticillium dahliae, and previously treated with MS. Compared to control plots where AUDPC value was 3141 (in 1999) and stem infection was 71.2% (in 2000), in plots treated with 600 L MS/ha AUDPC values were reduced by 57% to 80%, and stem infection was reduced by 49–54%. The incidence of infected dry stems, evaluated at the end of each season, was significantly reduced by all MS treatments, especially by 900 L/ha applied to a 60-cm depth (1999). Disease incidence in daughter tubers was also significantly reduced by all MS treatments. Yields obtained with 600 L/ha MS applied to a 30-cm depth were 32% and 21% higher than in the control in 1999 and 2000, respectively. In plots treated with 600 L/ha MS applied to a 60-cm depth yields were 17% and 28% higher than in the control in 1999 and 2000, respectively. With 900 L/ha MS applied to a 60-cm depth, yield was 21% higher than in the control in 1999. The yield of the low MS dose (300 L/ha), applied only in 2000, was not significantly different from the control. The differences in yield were due to the greater percentage of tubers larger than 45 mm. Yield reduction was highly correlated with disease severity expressed as AUDPC (in 1999 experiment). The net income in the 600 L MS/ha treatments was higher than in the control in both experiments. No indication of enhanced biodegradation was observed in the present study.