Yield,market quality and petiole nitrate concentration of non-irrigated Russet Burbank and Shepody potatoes in response to sidedressed nitrogen

Russet Burbank and Shepody potatoes were grown with the following four nitrogen treatments: 1) 90 kg ha^?1 at planting; 2) 180 kg ha^?1 at planting; 3) 90 kg ha^?1 at planting followed by an additional 90 kg ha^?1 side-dressed after tuber initiation; or 4) 90 kg ha^?1 at planting followed by an additional 45 kg ha^?1 sidedressing. When compared to the 90 kg ha^?1 at-planting treatment, petiole NO₃-N concentrations increased rapidly after sidedressing and were relatively constant through mid-season. Sidedressed N significantly increased total yields relative to the 90 kg N ha^?1 at-planting treatment by an average of 5.0 t ha^?1 in three of nine experiments. Three of the experiments, where yields did not significantly increase, were on sites which were not expected to respond to supplemental N based on petiole NO₃-N testing. A red clover green manure crop was the previous crop for two of these experimental sites. Petiole NO₃-N testing criteria were only partially effective in detecting sites where response to sidedressed N occurred. When compared to a single application of 180 kg N ha^?1 at planting, split application of 90 kg N ha^?1 at planting followed by a 90 kg N ha^?1 sidedressing significantly reduced total yields in one of nine experiments and did not affect yields in the remaining eight experiments. Tuber uniformity was improved in three of nine experiments by the split-N treatment. Specific gravity was not significantly affected. Use of 45 kg N ha^?1 at side-dressing resulted in similar yield as the 90 kg N ha^?1 sidedressing, although yield of large-sized tubers was often decreased with the lower N rate. Use of reduced at-planting N rates followed by sidedressed N does not appear to increase yields of non-irrigated Russet Burbank and Shepody potatoes when compared to the at-planting N rates that are currently recommended. This management approach can maintain yields at levels comparable to at-planting N programs and does provide an opportunity to reduce N application rates on sites where soil N reserves and soil amendments may make a substantial N contribution to the potato crop. Side-dressed N application can frequently improve yields and tuber size when potatoes have been underfertilized at planting; however, some inconsistency in response can be expected in regions that rely on unpredictable natural rainfall.     

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.     

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.     

Response of russet norkotah clonal selections to nitrogen fertilization

The low vine vigor and high N requirement of Russet Norkotah may lead to N loss and groundwater contamination on coarse-textured soils. Recent clonal selections from Texas have produced strains that have larger and stronger vines, which may alter N requirements. This twoyear study examined the N use efficiency (NUE), yield, and quality of Russet Norkotah strain selections fertilized with different N levels on a Hubbard loamy sand in central Minnesota. The selections, Texas Norkotah Strain (TXNS) 112, TXNS 223, and TXNS 278 were grown with standard Russet Norkotah under irrigated conditions and received total N levels of 28, 112, 224, or 336 kg ha^-1. Total, marketable, and large (>340 g) tuber yields increased linearly (P>0.05) with rate of N application in 1998 but not in 1997. The genotype main effect was not significant for any of the tuber yield parameters measured based on fresh weight. Vine, tuber, and total dry biomass yields were 116%, 5.8%, and 13.2%, respectively, higher with the selections than Russet Norkotah. Harvest index (HI), or the proportion of total dry matter partitioned to tubers, was 7% greater for Russet Norkotah than the TXNS selections, reflecting the larger vine growth of the selections. The selections accumulated significantly higher N in the vines (0.113 kg kg^-1 N) than the standard clone (0.053 kg kg^-1 N) as N rate increased from 28 to 336 kg ha^-1, and the difference between the selections and the standard clone was larger at higher N rates than at lower N rates. Russet Norkotah partitioned 10% more N to tubers than did the TXNS selections, reflecting the difference in HI between the standard cultivar and its clones. Nitrogen recovered from fertilizer N applied in addition to the 28 kg ha^-1 starter N (NUE₂₈) averaged 36% and varied little with genotype, N rate, or cropping year. Biomass accumulation from similar N additions (AUE), however, was significantly higher for the selections than Russet Norkotah at 112 kg N ha^-1 in 1997 only. At low N rate (112 kg ha^-1), the selections had higher physiological use efficiency (PUE₂₈) (mean 45.9 g g¹) than Russet Norkotah (25.9 g g¹). Results from this study demonstrate that, although N recovery was similar for the four genotypes, the Texas Norkotah strains produced greater biomass than Russet Norkotah per kg N applied at low rate in 1997 and per kg of fertilizer N absorbed by the plant in both years. However, under the conditions of this study, higher biomass of the selections did not translate into a marketable yield advantage over the standard cultivar.     

Influence of applied nitrogen on potato part II: recovery and partitioning of applied nitrogen

Maximizing fertilizer nitrogen (N) uptake efficiency, while maintaining crop productivity may reduce potential nitrate contamination of groundwater. A two-year field investigation was conducted to evaluate the effects of applied N on fertilizer N uptake, uptake efficiency, and total fertilizer N recovery of potato (Solarium tuberosum L. var. Russet Burbank) grown on irrigated sandy soils in Michigan. Nitrogen was applied as₁₅N-depleted ammonium sulfate [(NH₄)₂SO₄] at rates 0, 56, and 112, kg N ha^-1 in a single application at planting or 112 and 168 kg N ha^-1 in split applications during the growing season. Fertilizer N uptake efficiency was relatively unaffected by the N treatments. Fertilizer N uptake efficiency for the whole crop at onset of senescence averaged 52 percent, while values calculated for tubers at harvest were 34 percent. An average of 27 percent of the applied N was present in the soil to a depth of 120 cm after harvest. Approximately 83 percent of this N was found in the 0–30 cm depth. Over 90 percent of the recovered soil N was in the organic form. In this investigation, crop fertilizer N uptake and fertilizer N recovery in soil averaged 63 percent and was largely unaffected by the rate or timing of fertilizer N applications.     

Improving Yield and Quality of Processing Potato Crops Grown in the Argentinian Pampas: the Role of N,P and S and Their Impact on CO<Subscript>2</Subscript> Emissions

The area grown with processing potato crops in the Argentinian Pampas has been increasing steadily since 1995. The aim of this work was to assess the effects of N, P and S upon yield and tuber quality and their impact on CO₂ emissions assessed with the Cool Farm Tool-Potato. During the spring-summer growing seasons 2008/2009 and 2009/2010, ten fertilization experiments to individually assess N, P and S effects were carried out in the southeast region of the Argentinian Pampas. Nitrogen (four N rates), phosphorus (four P rates) and sulfur (three S rates) were applied at planting and tuber initiation; at combined rates of 0, 50, 100 and 150 kg N ha^?1, and at rates of 0, 25, 50 and 100 kg P ha^?1 and 0, 10 and 20 kg S ha^?1. N and P had a positive effect on total tuber yield, but tuber dry matter concentration (DMC) decreased at higher N rates. The fraction of marketable tubers suitable for processing into French fries increased with the addition of N, showed no variations with P fertilization, and decreased when S was applied. French fry colour, length/width (L:W) ratio and tuber defects were not affected by N, P and S fertilization. With regard to CO₂ emissions assessed with the Cool Farm Tool-Potato, results showed that the higher the N rates the higher the CO₂ emissions, but they decreased at higher yields. P and S rates did not have an impact on the CO₂ emissions, which also decreased at higher yields. Under the production system of the Pampas, N should be split between planting and tuber initiation, and intermediate P rates should be applied all at planting, in order to improve crop yield and quality and to reduce CO₂ emissions.     

Tuber yield, storability, and quality of Michigan cultivars in response to nitrogen management and seedpiece spacing

Information is required on nitrogen (N) fertility and seedpiece management for new cultivars and advanced breeding lines. Interactions amongst N fertilizer rate, genotype, and seedpiece spacing are complex, and can affect tuber yield, quality, and storability as well as N fertilizer efficiency. A field study was carried out in 2001 and 2002 at MSU Montcalm Research Farm in central Michigan. Tuber yields and post-harvest quality characteristics were evaluated for five potato genotypes (MSG227-2, MSE192-8Rus, Jacqueline Lee, Liberator, and Snowden) in response to a factorial combination of three N levels (200 kg N ha^-1, 300 kg N ha^-1-, and 400 kg N ha^-1) and two seedpiece spacings, narrow (0.20 m or 0.25 m) and wide (0.33 m or 0.38 m). Narrow seedpiece spacing consistently produced the highest U.S. No. 1 yields in all genotypes tested (37 and 34 t ha^-1, narrow vs wide spacing, respectively). There was a tradeoff between seedpiece spacing and N level in 2001 as tuber yields were enhanced by higher N levels at wide seedpiece spacing, but not at narrow spacing. In 2002, tuber yield was not enhanced, but petiole nitrate-N and tuber-N increased as N fertilization increased. Genotype was the major factor that influenced tuber quality characteristics at harvest and for stored tubers (e.g., specific gravity, internal defects, bruising, chip color rating, sucrose, and glucose). Spacing had minimal effects, whereas higher levels of N slightly reduced specific gravity both years, reduced internal defects in 2001 and enhanced sucrose at harvest in 2002. The cultivars tested demonstrated excellent storage characteristics for different N fertility levels and seedpiece spacing combinations. Overall, the recommended N fertilizer level for moderately long-duration potato cultivars in Michigan (200 kg N ha^-1) and a narrow seedpiece spacing optimized yield and tuber quality performance while conserving N fertilizer.     

Potato responses to calcium application on several soil types

On low cation exchange capacity, sandy soils where soil test Ca is low, potato tuber (Solanum tuberosum L.) Ca levels may not be optimal for maximum yield or quality; therefore, this study evaluated the effect of several levels of applied Ca on potato yield and quality on four soil types in Wisconsin. Calcium was applied to a Plainfield loamy sand, a Keiner loamy sand, a Pence sandy loam, and an Antigo silt loam at five rates in 1984 (0, 84, 252, 420, and 588 kg Ca ha^?1) and at six rates in 1985 (0, 56, 112, 168, 224, and 336 kg Ca ha^?1) as a band of CaSO₄ in the hill. In 1984, on the Plainfield soil, three rates of sidedress Ca(NO₃)₂ (0, 84, and 168 kg Ca ha_?1) were factorially combined with the five CaSO₄ treatments to evaluate the efficacy of Ca(NO₃)₂ as a concomitant Ca and N source. In general, total yield was not affected by CaSO₄ additions; however, the addition of approximately 100 kg Ca ha^?1 as Ca(NO₃)₂ increased total yield 3.6 Mg ha^?1. On the low-CEC, low-Ca soils (Plainfield and Kelner), improved tuber grade and/ or US1A size grade were detected with the addition of up to approximately 300 kg Ca ha^?1 as CaSO₄. The percent of US1A tubers increased 5 to 10% and the yield of US1A prime size (170–370 g) tubers increased 3.4 to 8.4 Mg ha^?1 above control values. These improvements were accompanied by increased periderm Ca concentrations, even though leaflet Ca concentrations were not affected by Ca applications. The use of 100 kg Ca ha^?1 asCa(NO₃)₂ in combination with CaSO₄ was more effective than CaSO₄ alone. On higher soil test Ca soils (Pence and Antigo), responses were inconsistent and periderm Ca was generally not increased.     

Recovery of starter nitrogen-15 fertilizer with supplementarily applied ammonium nitrate on irrigated potato

Nitrogen contamination in ground water of potato (Solanum tuberosum L.) producing areas has indicated a need for improved management of N and water, particularly on sandy soil. Therefore, a field experiment was conducted with the objective of following the recovery and partitioning of starter¹⁵NH₄ and¹⁵NO₃ into potato plant tops and tubers in conjunction with additional supplementarily applied NH₄NO₄. Potato plants treated with starter¹⁵NH₄ or¹⁵NO₃ tended to increase the percent recovery of starter¹⁵N in tubers sampled from one growth time to the next to reach nearly 40% recovery toward the end of the season. Whole plants reached peak recovery of around 50% of the starter¹⁵N near mid-season. From then on, there was a trend for loss of starter¹⁵N by senescence, defoliation or translocation to the roots. The percent recovery of starter¹⁵N was significantly higher at final tuber harvest (not whole plants) for the treatment with starter¹⁵NH₄ at 112 kg ha^?1 combined with 112 kg ha^?1 of supplemental N as compared to the treatment with 112 kg ha^?1 of starter¹⁵NH₄ plus 224 kg ha^?1 of supplemental N. This difference may have been a result of isotope dilution. Early in June the accumulation of starter¹⁵NO₃ in whole plants was about five times as high as that from starter¹⁵NH₄. Later there was no difference in percent recovery of these two forms of N. The temporary delay in starter¹⁵NH₄ uptake was probably related to slow nitrification early in the season instead of preferential uptake of starter¹⁵NO₃.     

Effect of Nitrogen Rate on Growth,Yield, Economics and Crisps Quality of Indian Potato Processing Cultivars

A field study was conducted during 2000–2001 and 2001–2002 at the Central Potato Research Institute Campus, Modipuram, India, in order to increasing the processing-grade tuber yield of India’s first ever developed processing potato cultivars, Kufri Chipsona-1 and Kufri Chipsona-2. Tuber yield and post-harvest quality characteristics were evaluated in response to five N levels (0, 90, 180, 270 and 360 kg N ha^-1). The crop growth traits (stem number, plant height and compound leaf number) responded positively to N application, whereas the effect of N fertilization on processing-grade tuber number, total tuber number per ha and tuber number per plant was quadratic. There was a steady increase in tuber weight per plant, processing-grade tuber yield, total tuber yield and biomass yield in response to N application. Kufri Chipsona-1 produced a 23.6% higher tuber yield per plant than Kufri Chipsona-2. Agronomic N use efficiency decreased linearly with increased N doses. Specific gravity and tuber dry matter percentage responded positively to N application, while crisps colour (at harvest and after storage) and reducing sugars remained unaffected. Cultivar was the major factor that influenced the tuber quality parameters (specific gravity, crisps colour). Higher values of these quality traits were observed in Kufri Chipsona-2 as compared to Kufri Chipsona-1. Net income and benefit cost ratio (B:C) indicated that Chipsona cultivars should be fertilized with 270 kg N ha^-1 for realizing higher processing-grade yields and desirable quality tubers.     

Tuber growth and biomass partitioning of two potato cultivars grown under different n fertilization rates with and without irrigation

Nitrogen and water deficiencies are known to affect potato yield, but much less is known of their effect on tuber growth and biomass partitioning. The objective of this on-farm study conducted at two sites in each of three years, 1995 to 1997, was to determine the effects of supplemental irrigation and N fertilization rates on tuber growth and biomass partitioning of the cultivars Shepody and Russet Burbank. The N fertilization rates were 0,100, and 250 kg N ha^-1in 1995, and 0, 50,100, and 250 kg N ha_?1 in 1996 and 1997. The highest bulking rate observed in our study (7.3 g fresh tubers m^-2 °C^-1) can be considered near the potential bulking rate in New Brunswick. The water deficit in the absence of supplemental irrigation reduced this potential bulking rate by as much as 40%, but this reduction was much less at five of six sites and negligible at two of six sites. Nitrogen deficiency reduced the bulking rate at two of six sites. This negative effect of N deficiency on bulking rate was greater with irrigation than without irrigation at two of six sites; the tuber bulking rate with irrigation was reduced by as much as 50% with no N applied at one site. Shepody had a greater bulking rate than Russet Burbank. The tuber bulking of Russet Burbank, however, started earlier and lasted longer than that of Shepody. Water and N deficiencies increased biomass partitioning to tubers and large roots. Shepody partitioned a greater proportion of its biomass to large roots and had a greater root biomass than Russet Burbank. Our results demonstrate the ability of potatoes to modify biomass partitioning when grown under water and/or N stresses. As a result of this compensation, the reduction in tuber yield due to limited N and water stresses is minimized.     

Nitrogen fertilization and irrigation affects tuber characteristics of two potato cultivars

Nitrogen fertilization, irrigation, and cultivars affect tuber characteristics such as tuber size, specific gravity, and N concentration. Few studies, however, have investigated the interaction of irrigation and N fertilization on the tuber characteristics of potato cultivars, particularly in Atlantic Canada. The objective of this on-farm study, conducted at four sites in each of three years, 1995 to 1997, was to determine the effects of supplemental irrigation and six rates of N fertilization (0-250 kg N ha^-1) on the number of tubers per plant, the average fresh tuber weight, tuber N concentration, nitrate (NO₃-N) concentration, and specific gravity of the cultivars Shepody and Russet Burbank. Nitrogen fertilization increased the average fresh tuber weight, tuber N and N0₃-N concentrations, and decreased specific gravity. Effects of increasing N fertilization on tuber characteristics were often more pronounced for Shepody than for Russet Burbank, and for irrigated than for non-irrigated conditions. Shepody had greater average fresh tuber weight and tuber N concentration, lower specific gravity, and fewer tubers per plant than Russet Burbank. Supplemental irrigation increased the average fresh tuber weight and the number of tubers per plant, but it had a limited effect on specific gravity and tuber N and NO₃-N concentrations. Tuber NO₃-N con centration and specific gravity were strongly related to tuber N concentration, which in turn depended primarily on N fertilization. Incidents of lowest specific gravity and highest NO₃-N concentration occurred with a relative yield close to or equal to 1.0. We conclude that the risks of low specific gravity and high tuber NO₃-N concentration are greater when fertilization exceeds the N requirements to reach maximum tuber yield.     

Potassium rate and source effects on potato yield, quality, and disease interaction

Field experiments were conducted over eleven site-years where five K rates (0, 93, 187, 280, and 373 kg K ha^?1) as KC1 or K₂SO₄ were band-applied at planting to potato (Solanum tuberosum L. ). Significant yield increases up to 332 kg K ha^?1 were observed in five of eleven site-years when soil test K ranged from 75 to 110 mg kg¹. The increase in tuber yield was associated with an increase of tuber size (170 to 370 g) and above in the US#1A category. Lack of yield response at the other site-years may be due to the high soil test K (125 to 180 mg kg^?1). Statistically significant differences in total tuber yield were not evident between the two sources of K fertilizer studied; however, there was a tendency for a significant rate x source interaction (p > 0.15) in five site-years where K₂SO₄ increased tuber yield more than KC1 at rates up to 280 kg K ha^?1. Above this rate, tuber yield decreased for K₂SO₄ but remained stable for KC1. Based on the tuber yield data and initial soil test K from the controls of each site-year, data from this study suggest that 104 mg K kg^?1 is a critical pre-plant soil test level. A reduction in specific gravity with increasing applied K was evident in most of the site-years of this study, although decreases were generally not as marked when K₂SO₄ was used. A significant decrease in hollow heart with increasing rate of K fertilization was observed in four of eleven site-years; however, statistically significant yield responses to added K were found at only one of these sites. The incidence ofRhizoctonia solani was generally not affected by K rate; however, there was a tendency in some site-years for a higher disease incidence when KC1 was used instead of K₂SO₄ Potassium rate slightly decreased stem numbers per seed piece, averaging 3.7, 3.6, 3.5, 3.4, and 3.3 across all experiments, for the 0, 93, 187, 280, and 373 kg K ha^?1 rates, respectively.     

Response of potatoes (cv russet burbank) to supplemental calcium applications under field conditions: Tuber calcium, yield, and incidence of internal brown spot

Potato tuber tissue is low in calcium as compared to leaves and stems. Several recent studies have provided evidence linking tuber quality with tuber tissue Ca concentration. The purpose of the present study was to determine the influence of supplemental Ca and N fertilization on tuber Ca concentration and internal brown spot of potato. Three soluble products (calcium nitrate, calcium chloride, and N-Plus; 9N:0K:0P:11Ca) were used as Ca sources with and without gypsum. In addition, a combination of calcium chloride, urea, and calcium nitrate (CUC) was also used without gypsum. Each treatment consisted of five replications, which received the same total amount of N (252 kg ha^?1) supplied either alone or in various combinations of ammonium nitrate, urea, calcium nitrate, calcium chloride, and N-Plus. The soluble sources of Ca were added at 68.8 to 168.0 kg ha^?1 while gypsum supplied Ca at 49 kg ha^?1. The application of all N by hilling (non-split) was compared to split application of N and Ca at hilling and 2, 4, and 6 wk after hilling. Tubers were mechanically harvested and graded according to industry standards. About 100 U.S. No. 1 tubers from each replication were cut in half along the longitudinal axis and visually inspected for internal defects. From each replication, non-periderm tissue from 15 tubers was combined for Ca analysis. There was no treatment effect on tuber yield in both years. Application of gypsum, either alone or in combination with the soluble sources, was not effective in reducing incidence of internal brown spot (IBS). Furthermore, with one exception, application of gypsum either alone or in combination with soluble sources of Ca was not effective at increasing tuber tissue Ca concentration. Combined analyses of data from 2 years showed that the application of soluble sources of Ca without gypsum increased tuber Ca concentration and decreased the incidence of IBS. Furthermore, split application of N had similar beneficial effects as compared to non-split N. Data from 1997 (a year with high IBS) gave a significant inverse relationship between tuber Ca and IBS, suggesting that an increase in tuber Ca can reduce IBS incidence.     

Influence of calcium on internal heat necrosis of Atlantic potato

While Atlantic is the cultivar of choice of potato chip processors for the mid-Atlantic region, susceptibility to internal heat necrosis (IHN) greatly increases grower risk of economic loss from unsalable tubers. Yield, tuber calcium levels, and percentage of tubers with IHN of several cultivars from a common seed source were examined at two locations. The percentage of tubers with IHN were significantly higher for Atlantic while the tuber Ca concentration was lower than those of Superior. Both the percentage of tubers with IHN and tuber Ca concentration was higher in New Jersey than Virginia. Lower Ca levels were found in tubers with necrotic medullary tissue than in those without. Studies were completed in Virginia and New Jersey to evaluate the influence of Ca source, Ca rate and location within the hill as well as nitrogen rate on the onset and progression of IHN of Atlantic potato. Tuber yield was not significantly influenced by either Ca source (calcium carbonate (CaCO₃) or calcium sulfate (CaSO₄)) or Ca rate (0-1800 kg Ca/ha). Calcium rate had no influence on size distribution. As expected, a significantly greater percentage of large tubers were noted with delayed harvest. In a short growing season (<110 days) yield was not influenced by nitrogen rates ranging from 84 to 252 kg/ha. However, with delayed harvest, yield was increased and IHN slightly reduced with 168 or 252 kg N/ha when compared to 84 kg/ha. The influence of applied Ca on IHN varied between years, but the addition of Ca or N did not reduce IHN sufficiently to avoid out-of-grade because of internal defects. Location of applied Ca within the hill had no effect on yield, specific gravity, IHN, or tissue Ca concentrations. Slightly higher leaf Ca was found when using CaCO₃ than CaSo₄. The influence of Ca rate in 1987 and 1988 on leaf, periderm, or medullary Ca concentrations was not consistent. Nitrogen had no significant influence on tissue Ca levels.     

Fumigation and Fertilizer Nitrogen Source Effects on Potato Yield,Quality, and Early Dying

Research has shown that while fumigation and use of ammonium N can both reduce the severity of verticillium wilt (Verticillium dahliae Kleb.) of potatoes (Solanum tuberosum L.), the use of the two practices together raises concerns over feeding the crop only ammonium N under reduced nitrification conditions. To assess the validity of this concern, we conducted two 3-year field split-plot experiments with both using metam sodium fumigant (none, fall or spring applied) as the main plot. For the first experiment, N source (134 kg N ha^?1 as ammonium sulfate, urea, or ammonium nitrate) was the split, whereas for the second trial in-season N rate (0, 67, 134, or 202 kg N ha^?1 all as ammonium sulfate) was the split. For both trials, in 2 of the 3 years, fumigation significantly increased tuber yield by an average of 9.9 Mg ha^?1 and decreased late-season verticillium severity ratings from 77 to 45%. In some years, fumigation also increased the proportion of U.S. No. 1 tubers and tubers >170 g. No differences in crop yield or quality were observed between the various N sources applied. This was true even on spring-fumigated areas with the highest rate of ammonium N applied. These experiments confirm that the choice between in-season potato N fertilizer should be based on factors such as potential for benefits or N losses, cost, and convenience of use rather than concern over an interaction between fumigation and ammonical N. While both fumigation and N rate reduced verticillium severity ratings in some years, the lack of interaction suggests these factors are functioning independently.     

Plant and soil responses to nitrogen and phosphorus fertilization of bromegrass‐dominated haylands in Saskatchewan,Canada

Field experiments were conducted at three different sites in Saskatchewan, Canada (Colonsay, Vanscoy and Rosthern) over two years (2005 and 2006) to determine the effects of dribble‐banded and coulter‐injected liquid fertilizer applied in the spring of 2005 at 56, 112 and 224 kg N ha^?1 with and without P at 28 kg P₂O₅ ha^?1. The three sites were unfertilized, 7‐ to 8‐year old stands of mainly meadow bromegrass (Bromus riparius)‐dominated haylands. All fertilization treatments produced significantly (P ≤ 0·05) higher dry matter yield than the control in the year of application at the three Saskatchewan sites. There was no significant difference between the two application methods (surface dribble band vs. coulter injected) for any fertilizer treatments. The addition of 28 kg P₂O₅ ha^?1 P fertilizer along with the N fertilizer did not have a significant effect on yield in most cases. In the year of application, increasing N rates above 56 kg N ha^?1 did not significantly increase yield over the 56 kg N ha^?1 rate in most cases, but did increase N concentration, N uptake and protein concentration. A significant residual effect was found in the high N‐rate treatments in 2006, with significantly higher yield and N uptake. In 2005, the forage N and P uptake in the fertilized treatments were significantly higher than the control in all cases. The N uptake at the three Saskatchewan sites increased with increasing N rate up to the high rate of 224 kg N ha^?1, although the percent recovery of applied N decreased with increasing rate. The P fertilization with 28 kg P₂O₅ ha^?1 also increased P uptake. Overall, rates of fertilizer of approximately 56 kg N ha^?1 appear to be sufficient to produce nearly maximum forage yield and protein concentration of the grass in the year of application.     

Forage yield and quality from intercropped barley, annual ryegrass and different annual legumes

Six annual legumes were evaluated as components of cereal-grass-legume intercrops in two experiments at two sites differing in elevation by 789 m. Barley (Hordeum vulgare L.) and Westerwolds rye-grass (Lolium multiflorum Lam.) were seeded on all intercrop plots. Dry-matter (DM) yield, crude protein (CP) and organic matter digestibility (OMD) were measured. DM yield and N content were used to estimate legume N fixation. Experiment 1 was conducted at both sites. At the lower site, Persian clover (Trifolium resupinatum L.) and annual alfalfa (Medicago sativa L.) accounted for 70% of the DM yield in harvest 1 (July), increased CP and OMD, but did not affect intercrop yield. They increased harvest 2 (August/September) intercrop yield by 263% and CP concentration by 65 g kg^?1 DM. They increased harvest 3 (October) yield by 275% and CP concentration by 78 g kg^?1 DM. Inclusion of striate lespedeza (Lespedeza striata) did not affect intercrop yield or quality. Annual legumes failed to establish at the higher elevation site and therefore had no effect on DM yield or forage quality. In Experiment 2, in which the performance of Westerwolds ryegrass was also compared with that of Italian ryegrass, and conducted at the lower site only, Persian clover and berseem clover (T. alexandrinum L.) increased CP of all three of the year's harvests. These two species contributed 29% of the DM yield in the first harvest (July) but did not affect total intercrop yield. They increased harvest 2 (August) yield by 313%. Persian clover increased harvest 3 (October) yield by 318% and berseem clover increased harvest 3 yield by 405%. Barrel medic (Medicago truncatula) and snail medic (M. scutellata) contributed 29% of harvest 1 yield, and increased both DM yield and CP content. Medics did not regrow. Aubade Westerwolds ryegrass contributed a greater percentage of the DM yield than did Maris Ledger Italian ryegrass at harvests 1 and 2. Ryegrass type did not affect total DM yield but did affect forage quality; intercrops containing the Italian ryegrass had higher CP at harvest 2 and higher OMD at harvest 3 than those containing the Westerwolds ryegrass. Over both experiments, at the lower elevation site, stands with Persian clover, berseem clover or alfalfa produced 80% of the yield of barley-ryegrass receiving 250 kg N ha^?1, and 165% of the yield of unfertilized barley-ryegrass. Berseem and Persian clover fixed about the same amount of N over the growing season; 188 kg N ha^?1 in Experiment 1 and 134 kg N ha^?1 in Experiment 2.     

Fertilization of Russet Burbank in short-season environment

A three-year investigation determined effects of N, P, K, and S rates on tuber yield and quality, economic return, and plant nutrient status of Russet Burbank grown on mineral soils in the Klamath Basin of Oregon. Yield responses were consistent over years. The highest yields and economic returns were achieved with the combination of 202 kg N, 29 kg P, 56 kg K, and 22 kg S ha^-1. Petiole NO₃-N concentrations were below published critical levels at the optimal N fertilizer rate of 202 kg N ha-1. Yield and economic return responses to increasing N rates were positive but small. The highest yield occurred at the lowest P rate (29 kg ha^-1). Tuber yield, grade, or quality did not respond to K fertilization. Findings suggest that nitrogen fertilizer management based on petiole analysis may require modifications for short growing-season environments.     

Effect of rate and time of fertilization on nitrogen and yield of Russet Burbank potatoes under center pivot irrigation

Applying less N on Russet Burbank potatoes (Solanum tuberosum L.) at planting time may reduce the potential loss of N from sandy soil by wind erosion and leaching early in the season. The objective of this study was to evaluate the effect of rate and time of N fertilization on potato production. Potatoes were grown in outdoor pot cultures with N rates of 75,150 and 300 ppm and in field plots with N rates from 112 to 448 kg N/ha applied in single and split applications. The results from pot cultures harvested after one month’s growth showed that yield of tops increased and tuber yield decreased as applied N at planting increased from 75 ppm to 150 or 300 ppm. Field results showed that the yield of potatoes was as high or higher when N applications were split between planting and when plants were 15 to 20 cm tall (early tuberization) as with the same amount of N applied at planting. Generally 112 kg N/ha at planting time was sufficient when additional N was applied after emergence. Split application of N resulted in more second growth on tubers than when all of the N was applied at planting.