Effects of different nitrogen forms on potato growth and development

The objective of this study was to test if the effects of different nitrogen forms on potato growth depend on the plant growth stage. Plants from different potato cultivars were treated with different forms of nitrogen before tuber initiation and after tuber formation. A nitrification inhibitor was used to prevent the transformation of ammonium (NH₄⁺) to nitrate (NO₃^?). Plant growth, tuber formation, leaf area, leaf chlorophyll content, and tuber yield were assessed. The results obtained over 2 years indicate that plants treated with NO₃-nitrogen (N) before or at tuber initiation produced more tubers per plant than those treated with NH₄-N. However, plants treated with NH₄-N develop tubers earlier. Additionally, after tuber formation, plants treated with NH₄-N had better shoot growth than plants treated with NO₃-N. A larger leaf area with higher leaf chlorophyll content resulted in greater dry matter accumulation and higher tuber yield at harvest for plants treated with NH₄-N.     

Phosphorus nutrition of white rose potato in relation to growth and minerals of leaf and root tissues

Abstract

White Rose potato plants (Solanum tuberosum, L.) were grown outdoors, without tuber formation, in a modified Hoagland's nutrient solution with 9 treatments of KH₂PO₄ ranging from 0 to 4.0 mmoles per liter. Deficiency symptoms ranged from very severe to none at harvest after 27 days of growth. Growth of the potato plants increased with increased P supply and was associated with an increased P content of the plant tissues. The critical H₂PO₄‐P concentration at a 10% reduction of top growth, based on a second leaf analysis, was about 1,000 ppm for the petiole and terminal bladelet and about 1,200 ppm for the lateral bladelet, dry weight basis.

Phosphorus nutrition had only a slight effect on the K, Na, Mg and NO₃‐N concentrations of the root tissues but Ca increased as phosphate increased which suggests a calcium phosphate precipitation. Phosphorus stress lowered the K, Na, Ca, Mg and NO₃‐N concentrations of the petiole tissues of the recently matured leaf which suggests that P increases salt accumulation. Phosphorus nutrition had only a slight effect on the concentrations of K, Na, Mg and Ca of the blade tissues of the recently matured leaf but NO₃‐N increased greatly with P supply.     

Nitrogen and Potassium Fertilization Responses of Potato (Solanum tuberosum) cv. Spunta

A potato field experiment was conducted for 2 consecutive years to determine the effects of nitrogen (N) and potassium (K) fertilization rates on the yield and quality of potato cv. Spunta cultivated on soil low in N and K. A 3?×?4 complete factorial experiment was used with three rates of nitrogen (330, 495, and 660 kg N ha^–1) and four rates of potassium (112, 225, 450, and 675 kg K₂Ο ha^–1). An additional treatment without fertilization was used as the control. On soils low in N and K, potatoes showed low yield response to K fertilizer. The greatest tuber yields for both years were achieved at 495 kg N ha^–1 and 112 kg K₂O ha^–1 (29.81 t ha^–1) and 225 kg ha^–1 (27.13 t ha^–1), respectively. Differences in mean fresh weight due to treatment application were not significant. Application of 495 kg N ha^–1 significantly reduced harvest index (the ratio of tuber dry weight to the total dry weight at harvest) compared to 330 kg N ha^–1, but at 660 kg N ha^–1 harvest index achieved the greatest significant value. Potassium fertilization had no significant influence on harvest index. Nitrogen rates positively influenced the number of tubers. The addition of 450 kg K₂O ha^–1 significantly enhanced the number of tubers compared to the lower K rates, and the number was significantly decreased by the application of 675 kg K₂O ha^–1. Tuber dry-matter concentration was significantly promoted by N fertilization in both cultivation years, but it was negatively affected by K fertilization in the first year of cultivation. There was no change in tuber N with N application, but N application strongly increased nitrate (NO₃) concentration, which fluctuated between 360 and 1382 mg kg^–1 wet mass. Tuber NO₃ was negatively correlated with tuber yield, indicating that high levels of NO₃ in tubers can adversely affect yield. Tuber response to K fertilization was not in accordance with the rate of applied nutrient.     

CO2与养分交互作用对番茄幼苗叶片碳、氮积累及碳、氮比动态的影响

营养液栽培条件下,以番茄(品种,合作906)为材料,研究CO2施肥与4种不同养分供应强度的交互作用对番茄幼苗生长及其叶片中的碳、氮浓度与碳、氮比动态变化的影响。结果表明,在不同营养液养分浓度下,CO2施肥能增加番茄幼苗生物量的积累,提高生长速度;增加番茄幼苗叶片中氮、碳积累量与吸收速率;而且对CO2作用效果的响应随营养液养分浓度的提高而增加。在所有处理中碳、氮积累量与吸收速率随生育期的延长呈上升趋势。说明在番茄育苗后期要增加施肥量,而且在CO2施肥的情况下施肥量增加的量要大。CO2施肥对生长在不同营养液中番茄叶片中的碳、氮比在不同生长阶段的影响是不同的,但在同一CO2浓度条件下,番茄幼苗各个取样阶段均表现为碳、氮比随营养液浓度的降低而增加。对番茄幼苗碳、氮积累量、总干生物量与生长时间的关系研究表明,氮积累量、总干生物量与生长时间均符合二次曲线变化。     

Effect of Integrated Management of Nitrogen Fertilizer and Cattle Manure on the Leaf Chlorophyll,Yield, and Tuber Glycoalkaloids of Agria Potato

Management of nutrients, especially nitrogen (N), is one of the most important factors in potato production. Cattle manure and mineral fertilizers are two sources of N that can affect the quality and quantity of potato yield. The effects of the use of cattle manure (5, 10, 15, and 20 ton ha^?1), N fertilizer (50, 100, and 150 kg ha^?1), and their interaction on tuber yield, chlorophyll content, and glycoalkaloid concentration were evaluated during field experiments in Iran in 2008 with a randomized complete block design with a factorial arrangement of three experimental replications. At the time of flowering, chlorophyll a, b, and total (chlorophyll) were recorded by spectrophotometry. Furthermore, at the end of the growth season, tuber yield was calculated and tuber glycoalkaloids were measured by the colorimetric method for the assessment of quantitative and qualitative characteristics of potato. Chlorophyll a, b, and total content increased linearly and very significantly in response to the application of manure and N fertilizer. The interaction between manure and N fertilizer was also significant; somehow the maximum content of total chlorophyll [1.448 mg g^?1 fresh weight (FW)] was obtained by using 150 kg N + 20 ton of manure per hectare. Cattle manure, N fertilizer, and their combination had a highly significant effect on tuber yield. Maximum tuber yield (36.8 ton ha^?1) was obtained by the utilization of 20 ton manure + 150 kg N per hectare. Total glycoalkaloid content was affected by the N application only. It showed a linear increase in the presence of increased concentration of N fertilizer.     

Interactive effects of elevated CO2 and nitrogen fertilization levels on photosynthesized carbon allocation in a temperate spring wheat and soil system

Increasing atmospheric CO2 concentration impacts the terrestrial carbon(C) cycle by affecting plant photosynthesis, the flow of photosynthetically fixed C belowground, and soil C pool turnover. For managed agroecosystems, how and to what extent the interactions between elevated CO2 and N fertilization levels influence the accumulation of photosynthesized C in crops and the incorporation of photosynthesized C into arable soil are in urgent need of exploration.We conducted an experiment simulating elevated CO2 with spring wheat(Triticum aestivum L.) planted in growth chambers.13C-enriched CO2 with an identical 13C abundance was continuously supplied at ambient and elevated CO2 concentrations(350 and 600 μmol mol-1, respectively) until wheat harvest.Three levels of N fertilizer application(equivalent to 80, 120, and 180 kg N ha-1 soil) were supplied for wheat growth at both CO2 concentrations. During the continuous 62-d 13CO2 labeling period, elevated CO2 and increased N fertilizer application increased photosynthesized C accumulation in wheat by 14%–24% and 11%–20%, respectively, as indicated by increased biomass production, whereas the C/N ratio in the roots increased under elevated CO2 but declined with increasing N fertilizer application levels. Wheat root deposition induced 1%–2.5% renewal of soil C after 62 d of 13CO2 labeling. Compared to ambient CO2, elevated CO2 increased the amount of photosynthesized C incorporated into soil by 20%–44%. However, higher application rates of N fertilizer reduced the net input of root-derived C in soil by approximately 8% under elevated CO2. For the wheat-soil system, elevated CO2 and increased N fertilizer application levels synergistically increased the amount of photosynthesized C. The pivotal role of plants in photosynthesized C accumulation under elevated CO2 was thereby enhanced in the short term by the increased N application. Therefore, robust N management could mediate C cycling and sequestration by influencing the interactions between plants and soil in agroecosystems under elevated CO2.     

Nitrogen supply determines responses of yield and biomass partitioning of perennial ryegrass to elevated atmospheric carbon dioxide concentrations

Perennial ryegrass (Lolium perenne L. cv. Parcour) grown at eight levels of nitrogen (N) fertilization (0–765 mg/pot) was exposed to ambient (390 ppm) and elevated (690 ppm) carbon dioxide (CO₂) concentrations for 83 days. Plants were cut three times and dry matter yields determined for each harvest. At final harvest, dry weight of root and stubble biomass was determined, as N concentrations of all plant fractions were determined. Carbon dioxide enrichment effects on yield and total plant biomass increased with increasing N fertilization. The weaker CO₂‐related yield enhancement at low N supply was due to the plants inability to increase tiller number. Root fraction of total plant biomass at final harvest was increased by high CO₂ and decreased by N supply. Root biomass was significantly increased by CO₂ enrichment and for both CO₂ treatments the N supply for maximum root mass coincided with the N supply for reaching maximum total plant biomass. A significant correlation between root fraction of total plant dry matter and N concentration of total plant biomass, which was not changed by CO₂ enrichment, indicates that biomass partitioning between shoot and root is controlled by the internal N status of the plant.     

EFFECTS OF CARBON DIOXIDE AND PHOSPHORUS SUPPLY ON POTATO DRY MATTER ALLOCATION AND CANOPY MORPHOLOGY

□ Data on combined effects of elevated carbon dioxide concentration (CO₂) and phosphorus fertilization (P) on potato are scarce. Growth chamber studies (E1 and E2) that used three P and two CO₂ levels were conducted. Leaf, stem, tuber, and stolon dry matter increased with P. Lateral-stem production was sensitive to P with a minimum 2.5-fold increase in mass. Leaf length increased an average 20.2% in E1 and 38.2% in E2 and leaf area increased an average 336% in E1 and 470% in E2 across CO₂ levels. Tuber dry mass increased 22% in E1 and 38.2% in E2 in response to elevated CO₂ and total dry mass by 14.1 and 15.4%. Tissue P contents increased with P but were unaffected by CO₂. Effects of P on canopy branching were associated with plant N status. The studies suggest elevated CO₂ levels are unlikely to alter potato P requirements on a unit mass basis.     

Starch concentration and impact on specific leaf weight and element concentrations in potato leaves under varied carbon dioxide and temperature

Foliar concentrations of starch and major elements, nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg), along with specific leaf weight (SLW) were determined in the potato (Solanum tuberosum L.) cvs ‘Denali’, ‘Norland’, and ‘Russet Burbank’ grown for 35 days under CO₂ concentrations of 500, 1,000, 1,500 and 2,000 μmol.mol^‐1 at both 16°C and 20°C air temperature. The starch concentration, pooled from the three cultivars, increased with increasing CO₂ concentration at both 16°C and 20°C and was consistently higher at 16°C than at 20°C. The SLW (g.m^‐2) was positively related to the foliar starch concentration on the basis of leaf area or dry weight. The concentrations of N, P, Ca, and Mg in leaves were negatively related to starch concentration under =14% starch on a dry weight basis. Above 14% starch, there was no significant relationship between element and starch concentrations. Similar patterns were seen when the SLW and element concentrations were expressed on a starch‐free basis. In contrast, the leaf concentration of K was not closely related to the starch concentration because the K concentration was similar at varied CO₂ levels. The results of this study indicate that the changes in SLW and concentrations of N, P, Ca, and Mg in potato leaves only partially resulted from the changed starch concentration.     

Soil and tuber calcium affecting tuber quality of processing potato (Solanum tuberosum L.) cultivars grown in Hokkaido,Japan

Calcium (Ca) nutrition for potato (Solanum tuberosum L.) is important to increase tuber Ca concentration and improve potato tuber yield and quality. High tuber Ca content among other benefits mitigates incidence of blackspot bruise through maintenance of membrane health and regulation of biochemical reactions that leads to potato tuber discoloration. However, growers avoid application of Ca fertilizer in potato production in the belief that it causes potato common scab in Hokkaido, Japan. This study was conducted in Hokkaido to determine the current status of soil Ca and tuber Ca content levels, and its effect in mitigating incidence of potato bruise. Soil and tuber samples were collected from 90 and 80 fields in Tokachi and Kamikawa districts, respectively, in 2013 and 2014. Soil samples were analyzed for base saturation, Ca saturation, and exchangeable Al. Tuber Ca content and susceptibility of tubers to bruising were also evaluated. This study found that (1) 81% and 76% of soils collected from Tokachi and Kamikawa district, respectively, were deficient in Ca level, (2) tuber Ca content was lower than the reported value (250 mg kg^?1) considered to mitigate incidence of bruise, and (3) incidence of bruise were influenced by both tuber specific gravity and Ca content. There is urgent need to apply Ca fertilizer to attain increased soil Ca levels and improve quality of tubers.     

Influence of Sulfur Fertilization on Infection of Potato Tubers with Rhizoctonia solani and Streptomyces scabies

ABSTRACT

Under conditions of sulfur (S)-deficient soil, applied S fertilization had a significant repressive effect on fungal infections such as that of oilseed rape and grapes with light leaf spot (Pyrenopeziza brassicae) and powdery mildew (Uncinula necator), respectively. For potatoes (Solanum tuberosum L.) it has been shown in earlier literature that elemental sulfur fertilization increased yield of potato tubers and improved tuber quality and resistance against Streptomyces scabies; the bactericidal effect was attributed to a reduced soil pH. So far, however, no information is available about the influence of S supply on bacterial and fungal diseases in potatoes. It was the aim of the present investigation to quantify the influence of S form and dose on infections of potato tubers with Rhizoctonia solani and Streptomyces scabies as a contribution to plant nutrition strategies for healthier plants. Field experiments with potatoes were conducted in 2001 and 2002 in Poland in a split-plot design with different sulfur forms (elemental S and K₂SO₄) and rates (0, 25, and 50 kg ha^{? 1} S). The application of sulfur significantly increased tuber yield in both years of experimentation. Generally, with increasing sulfur dose a significant decrease of the infection rate with Rhizoctonia solani was found for elemental S as well as for K₂SO₄ applications. Infection rate and severity of the disease was improved only by elemental S application due to a reduction in soil pH in the case of Streptomyces scabies. Thus it can be concluded that the health-promoting effect of sulfur fertilization was related mainly to the S status of the plant in case of infections with Rhizoctonia solani, while for Streptomyces scabies no mechanisms of S-induced resistance were found. The identification of differences in the S metabolism of Rhizoctonia solani and Streptomyces scabies may therefore elucidate S-induced resistance mechanisms in plants.     

Changes in C storage by terrestrial ecosystems: How C-N interactions restrict responses to CO2 and temperature

A general model of ecosystem biogeochemistry was used to examine the responses of arctic tundra and temperate hardwood forests to a doubling of CO₂ concentration and to a 5°C increase in average growing season temperature. The amount of C stored in both ecosystems increased with both increased CO₂ and temperature. Under increased CO₂, the increase in C storage was due to increases in the C∶N ratio of both vegetation and soils. Under increased temperature, the increased C storage in the forest was due to a shift in N from soils (with low C∶N ratios) to vegetation (with high C∶N ratios). In the tundra, both a shift in N from soils to vegetation and an increase in C∶N ratios contributed to increased C storage under higher temperatures. Neither ecosystem sequestered N from external sources because the supply rate was low.     

两种氮水平下CO2浓度升高对冬小麦生长和氮磷浓度的影响

预计到 2 1世纪末期大气CO2 浓度将会比目前水平增加 1倍 ,约 70 0 μmolmol- 1 左右。因此CO2 浓度升高对作物的影响研究十分重要。本文探讨在两种氮 (N)水平下 ,CO2 浓度升高对冬小麦 (TriticumaestivumL cv Xinong 872 7)生长和地上部N、磷 (P)浓度的影响及原因。试验设 3 5 0 μmolmol- 1 和 70 0 μmolmol- 1 两种CO2 浓度水平和 45kghm- 2 和 90kghm- 2 两种N肥施用水平。结果表明 ,CO2 浓度升高 ,冬小麦株高和叶面积指数 (LAI)均增加 ,净同化率 (NAR)值增加 ,叶面积比率 (LAR)下降 ,比叶重 (SLW )不增加。高CO2 浓度对相对生长率 (RGR)的影响因施N水平而异 ,低N时RGR不增加 ,高N时明显增加。CO2 浓度增加 ,小麦抽穗提早 7～ 8d ,叶鞘、茎杆和地上部干物重提高 ,叶片、叶鞘和茎杆N、P浓度降低 ,但叶片、叶鞘和茎杆N、P吸收量增加均不明显。CO2 浓度升高 ,氮磷利用效率 (NUE和PUE)提高 ,而对相对氮磷累积速率 (RNAR和RPAR)影响不大。高CO2 浓度冬小麦体内N、P浓度下降是由于稀释效应以及NUE和PUE提高之故。     

不同供磷状况下CO2浓度升高对番茄根系生长及养分吸收的影响

采用培养试验研究了磷缺乏与正常供磷条件下,CO₂浓度由350μL/L升高至800μL/L苗期番茄的生物量、根系特征和不同器官N、P、K养分含量的变化。结果表明,无论缺磷与否,CO₂浓度升高均能显著增加番茄地上部及根系的干物质积累量,提高根冠比。在磷缺乏条件下,CO₂浓度升高对番茄根系生长的促进主要表现为增加根系的体积和表面积;而在磷正常供应条件下主要表现为同时增加根体积和分根数,有利于形成强壮的根系。在两种供磷水平下,CO₂浓度升高对番茄各器官的N、P、K含量产生不同的稀释效应,但N、P、K总积累量却随CO₂浓度升高而显著增加;而且CO₂浓度与供P水平对番茄植株的N、P、K积累量具有极显著的正交互效应。     

Phosphorus‐deficiency effects on response of symbiotic N2 fixation and carbohydrate status in soybean to atmospheric CO2 enrichment

The impact of phosphorus (P) deficiency on response of symbiotic N₂ fixation and carbohydrate accumulation in soybean (Glycine max [L.] Merr.) to atmospheric CO₂ enrichment was examined. Plants inoculated with Bradyrhizobium japonicum MN 110 were grown in growth chambers with controlled atmospheres of 400 and 800 μL CO₂ L^‐1 and supplied either 1.0 mM‐P (P‐sufficient) or 0.05 mM‐P (P‐deficient) nitrogen (N)‐free nutrient solution. When plants were supplied with sufficient P, CO₂ enrichment significantly increased whole plant dry mass (83%), nodule mass (67%), total nitrogenase activity (58%), and N (35%) and P (47%) accumulation at 35 days after transplanting (DAT). Under sufficient P supply, CO₂ enrichment significantly increased starch concentrations in nodules compared to the normal atmospheric CO₂ treatment. Under normal CO₂ levels (400 μL L^‐1) nonstructural carbohydrate concentration (starch plus soluble sugar) was significantly higher in leaves of P‐deficient plants than in leaves of P‐sufficient plants in which nonstructural carbohydrate concentration exhibited a strong diurnal pattern. Under deficient P supply whole plant dry mass, symbiotic N₂‐fixation parameters, and N and P accumulation were not enhanced by atmospheric CO₂ enrichment. Phosphorus deficiency decreased nonstructural carbohydrate accumulation in nodules at the end of a 10‐day period in which functional activity was developing by 86% relative to P‐sufficient controls. While P deficiency elicited significant increases in the nonstructural carbohydrate concentration in leaves, it caused significant decreases in the nonstructural carbohydrate concentration in nodules over the diurnal cycle from 30 to 31 DAT. Collectively, these results indicate that the lack of a symbiotic N₂‐fixation response to atmospheric CO₂ enrichment by P‐deficient plants may be related to the decreased carbohydrate status of nodules.     

Carbon dioxide enrichment decreases critical nitrate and nitrogen concentrations in wheat

Atmospheric carbon dioxide (CO₂) levels are increasing. In a glasshouse experiment with wheat grown at 5 levels of nitrate (NO₃) supply, CO₂ enrichment (1500 cm³/m³) substantially decreased critical concentrations of N03‐N and total‐N in stem bases and leaves. For example, critical NO₃‐N concentrations in stem bases at Feekes Stages 1.5, 5, and 10.3, were 4.5, 2.0, and 2.0 mg/g dry wt, respectively, for CO₂‐enriched plants, compared with 7.5, 6.2 and 6.4 mg/g dry wt, respectively, for control plants grown at the ambient level of CO₂. However, concentrations of NO₃‐N in the rooting medium required to produce maximum dry matter accumulation by CO₂‐enriched plants were similar to those of control plants at the three growth stages. Critical concentrations of NO₃‐N and total‐N declined with time in stem bases and leaves of plants grown at both ambient and elevated CO₂ levels, but the decline was greater for CO₂‐enriched plants. It was concluded that diagnostic criteria based on current critical N concentrations may become invalid as the atmospheric level of CO₂ increases.     

Boron fertilization effects in processing grade potato on an Inceptisol of West Bengal,India

A 2-year field trial was conducted in processing grade potato cv. Kufri Chipsona-3. The treatments comprised recommended dose of fertilizer (RDF) (200:150:150 N:P₂O₅:K₂O kg ha^?1) with or without boron (B) application (soil and foliar). The results revealed that B fertilization significantly increased tuber number and yield. Three sprays of 0.1% boric acid (at 40, 50 and 60 days after planting) produced the maximum number and yield of tubers and enhanced B uptake in potato tuber, haulm as well as in total plant accounting 85.8, 182.0 and 169.8% more than control, respectively. The same treatment came up with greatest net return and benefit: cost ratio. B fertilization exerted significant influence on available N and B status of post-harvest soil, while the effect was non-significant on available P and K. Results suggest that right dose and method of B application is vital for optimizing tuber yield and B-use efficiency for processing grade potato.     

Potassium concentration effect on growth,gas exchange and mineral accumulation in potatoes

This study was conducted to evaluate the responses of potatoes to six K solution concentrations maintained with a flow‐through nutrient film system. Potato plants were grown for 42 days in sloping shallow trays containing a 1 cm layer of quartz gravel with a continuous flow of 4 ml min^‐1 of nutrient solutions having K concentrations of 0.10, 0.55, 1.59, 3.16, 6.44, 9.77 meq L^‐1. Plant leaf area, total and tuber dry weights were reduced over 25% at 0.10 meq L^‐1 of K and over 17% at 9.77 meq L^‐l of K compared to concentrations of 0.55, 1.59, 3.16 and 6.44 meq L^‐1 of K. Gas exchange measurements on leaflets in situ after 39 days of growth demonstrated no significant differences among different K treatments in CO₂ assimilation rate, stomatal conductance, intercellular CO₂ concentration, and transpiration. Further measurements made only on plants grown at 0.10, 1.59, 6.44 meq L^‐1 of K showed similar responses of CO₂ assimilation rate to different intercellular CO₂ concentrations. This suggested that the photosynthetic systems were not affected by different K nutrition. The leaves of plants accumulated about 60% less K at 0.10 meq L^‐1 of K than at higher K concentrations. However, Ca and Mg levels in the leaves were higher at 0.10 meq L^‐1 of K than at higher K concentrations. This indicates that low K nutrition not only reduced plant growth, but also affected nutrient balance between major cations.     

Nitrogen rhizodeposition of young wheat plants under elevated CO<Subscript>2</Subscript> and drought stress

The objective of this study was to determine the effect of drought stress and elevated CO₂ concentrations around the shoots on N rhizodeposition of young wheat plants. In a pot experiment, the plant N pool was labeled through ¹⁵NH₃ application to shoots at nontoxic NH₃ concentrations, and the impact of low water supply (40% field capacity), elevated CO₂ (720 μmol mol⁻¹ CO₂), and the combination of both factors on the ¹⁵N distribution was studied. Total ¹⁵N rhizodeposition ranged from 5 to 11% of the total ¹⁵N recovered in the plant/soil system. Elevated CO₂ concentration as well as drought stress increased the belowground transport of N and increased the relative portion of N rhizodeposition on total ¹⁵N in the plant/soil system. However, while the increased N rhizodeposition with elevated CO₂ was the result of increased total belowground N transport, drought stress additionally increased the portion of ¹⁵N found in rhizodeposition vs roots. Elevated CO₂ intensified the effect of drought stress. The percentage of water soluble ¹⁵N in the ¹⁵N rhizodeposition was very low under all treatments, and it was significantly decreased by the drought-stressed treatments.     

Potato tuber yield and quality in response to different nitrogen fertilizer application rates under two split doses in an irrigated sandy loam soil

Abstract

Management strategies to minimize nitrogen (N) losses to the atmosphere and water bodies from potato production fields while maintaining tuber yields and quality relies on good N management. A 2-year (2016–17 and 2017–18) field trial with ‘Symphonia’ potato was completed on a sandy loam soil irrigated with flood irrigation in Punjab, Pakistan to investigate the effect of N fertilizer rate on vegetative, yield and tuber quality parameters. The N fertilizer treatments comprising six N rates from 0 to 300?kg ha^?1 were applied at 50?kg N increments. Number of stems and tubers plant^?1 showed a quadratic response while other parameters revealed cubic trends in response to N fertilizer rates. Applying more than 250?kg ha^?1 of N fertilizer did not increase vegetative growth and yield. In conclusion, the optimal N-application rate of 250?Kg ha^?1 has great potential to improve yield and quality of potato in the sub-tropical region of Punjab, Pakistan. These findings, besides improving productivity can minimize the risk of N fertilizer loss to the atmosphere.