Leek Production Research Articles

Efisiensi Produksi Bawang Prei (Allium Ampeloprasum) Di Pertanian Organik (Porkab) Desa Suberejo Kecamatan Batu Kota Batu

<p><em>This study aims to analyze the production factors of leek farming, analyze the efficiency of leek farming in PORKAB. Respondents amounted to 30 people with saturated sampling technique. To determine the effect of the use of production factors on leek farming using Cobb-Douglas analysis, and to determine the level of efficiency in leek farming using three parts of production inputs technically, allocatively and economically. The results of this study indicate that the factors that affect production in leek farming, namely vegetable pesticides, have a significant effect, while land area, labor, seeds, and manure have no significant effect on leek production. Technically, the area of land, seeds, manure and vegetable pesticides in leek farming is not technically efficient while the workforce is technically inefficient. The total value of technical efficiency, which is 1.017, is greater than 1, meaning that the proportion of additional production factors will result in greater production. Allocatively, labor and manure have an allocative efficiency value greater than 1, meaning that leek farming is not allocatively efficient. In the area of land, seeds and vegetable pesticides are smaller than 1, meaning that leek farming is not allocatively efficient. While economically on land area, seeds and vegetable pesticides are not economically efficient, while labor and manure are not economically efficient.</em></p><p><strong><em>Keywords: Efficiency, Prey Onion, Production.</em></strong></p>

Detection of leek white tip disease under field conditions using hyperspectral proximal sensing and supervised machine learning

Leek white tip disease is one of the key yield-limiting factors in leek production. It leads to socio-economic and environmental costs due to the need for fungicide applications. Precision agriculture aims at reducing these costs, while maintaining or improving farmer revenues. To be able to apply variable rate fungicides, in-field disease detection is necessary. In this work, a disease detection methodology was created that can detect early, pre-symptomatic white tip disease symptoms in field conditions with millimetre resolution. A hyperspectral training library was constructed containing 29,744 spectra of healthy leek, weed plants, diseased leek plants and soil. Soil pixels were removed from hyperspectral images by means of LDA classification, followed by a custom noise filter algorithm. Then, a logistic regression supervised machine learning classifier was trained with five classes: healthy plant material, early (pre-visual) disease, moderate disease, severe disease and fully developed disease. The overall accuracy of the disease detection model was 96.74%. Model diagnostics showed a low likelihood of classifying diseased pixels as healthy (3.59%) and a low likelihood of falsely classifying healthy pixels as diseased (0.77%).

Chapter 12. Onion, Leek, and Chive Production in Florida

Chapter 12 of the Vegetable Production Handbook.

In Vitro Gynogenesis in Leek (Allium ampeloprasum L.).

Leek (A. ampeloprasum L.) is an economically important vegetable crop from Alliaceae family. It is a non-bulb forming biennial species grown for its pseudostem and leaves. Leek is a tetraploid with one of the largest genomes known among cultivated plant species. It has enormous economic importance all around the world for many purposes such as vegetable, medicinal herb, and food seasoning. Production and consumption of leek is in rise all around the world and breeders are trying to develop new F1 hybrid varieties with desired agronomical traits. Although self-compatible, leek shows high tendency toward outcrossing and display severe inbreeding depression when selfed with its own pollen. Therefore, inbred development through classical breeding techniques is very difficult in this crop. Traditional leek genotypes are highly heterozygous, open pollinated varieties. There is a high demand for F1 hybrid varieties with resistance to biotic and abiotic stresses and high-quality plants. Our group is trying to incorporate gynogenesis-based doubled haploid technology to leek improvement programs. Over the years, many experiments were carried out to determine the gynogenic potential of donor leek genotypes of different genetic backgrounds in different induction media. Here, we report a protocol allowing production of green gynogenic leek plants via single step culture of unopened flower buds. Ploidy levels of gynogenic regenerants are determined by flow cytometry analysis. A majority of the gynogenic leek regenerants produced survived well in vivo.

Effectivity of Potassium and Fish Fertilizer on Leek Growth (Allium fistulosum L.)

Leek is one type of leaf vegetable that is commonly used for cooking vegetables or seasonings. Currently, it founded some problem in leek cultivation, including the production is low because the fertilization is not appropriate. The type and dosage of fertilizer can contribute to increasing production. This research aims to determine the dosage of potassium, and fish fertilizer is right for increased leek production. The research was conducted from January - March 2015 in the Berastagi experimental farm, with altitude ± 1340 meters above sea level; the soil type was andisol. Experiments using a randomized block design (RBD) factorial with three replications. The first factor is the dosage of potassium fertilizer K0 (0 kg/ha), K1 (100 kg/ha), K2 (200 kg/ha), and K3 (300 kg/ha). The second factor is dosage fish fertilizer I0 (0 kg/ha), I1 (500 kg/ha), I2 (1000 kg/ha), and I3 (1500 kg/ha). The leek variety was used is local variety. The results showed that there is an interaction between the potash and fish fertilizers on leek plant height. Application potash fertilizer (K2O) dosage of 200 kg/ha and fish fertilizer dosage of 1000 kg/ha can increase the leek plant height 56,98 cm. Application potash fertilizer (K2O) dosage of 200 kg/ha can increase the stem diameter, length of stems, length of leaves, and fresh weight per plant. Application fish fertilizer dosage of 1000 kg/ha can increase the stem diameter, leaves length, fresh and dry weight per plant

For the Safety of Agricultural Products (From the Standpoint of GLOBALG.A.P and the Sustainable Development Goals)

GLOBALG.A.P. (G-GAP), an international farm assurance program of good agricultural practices, has attracted attention with the 2020 Tokyo Olympics in Japan. The Miyagi University School of Food Industrial Sciences Affiliated Farm at Tsubonuma (Sendai, Miyagi Prefecture, Japan) received G-GAP certification for our leek production on 1 December 2018 (to 30 November 2019). We began working towards compliance with the over 200-point checklist in the summer of 2016. It is important for the person in charge to pay attention to food safety, traceability and quality management, workers' safety and health, soil, fertilizer and pesticide management, integrated pest management and sustainable water management. The checklist consists of All Farm Base(AF), Crops Base(CB) and Fruits and Vegetables(FV). We recognized five major benefits of this practice. 1) Communication about the farm work between faculty members and field staff became easier than before. 2) We had a common direction to acquire the G-GAP certification. 3) The practice of G-GAP is involved in all aspects of agricultural issues. 4) G-GAP can lead to themes in the academic issues. 5) The practice can be incorporated into the training curriculum at our farm. We thought that the mission of G-GAP and the Sustainable Development Goals are similar in several points, with ‘sustainable’ being a common word in both. We think that G-GAP can be an effective tool for students to practice farm work, and we intend to incorporate G-GAP into our training curriculum.

Leek production in conventional and organic arable-vegetable rotations in the Netherlands

Leek production, one of the most important vegetables grown on the sandy soils in the South East of the Netherlands, is known to have a high rate of nitrogen leaching. Nitrogen leaching from leek cultivation depends not only on the cropping strategy but also on the whole farming system. The objective of this study was to evaluate nitrogen losses and crop yield of leek cultivation and the total farming system with different fertilization strategies. A farming systems experiment with two conventional and one organic farming system with arable and vegetable crops on sandy soils was evaluated. One conventional farming system (LOW) had a low organic matter input consisting of crop residues and green manure crops only. The other conventional farming system (STANDARD) had a regular organic matter input including cattle and pig slurry. The organic system had a high organic matter input because of the use of farm yard manure and cow slurry. Data of crop yield, nutrient balances and nitrate leaching for the period 2011-2016 are discussed. In the LOW system, crop production was on average 5% lower than in STANDARD. Nitrogen surplus was lower in LOW than in STANDARD. Phosphorus surplus was about equal between the systems and potassium surplus was higher in LOW than in STANDARD. Nitrate leaching was comparable in LOW and STANDARD, but both above the limit set in the EU nitrates directive of 50 mg L-1. Other indicators of nitrogen leaching as soil mineral nitrogen content and nitrogen surplus indicate that leaching risk in LOW is lower than in STANDARD. Leek yield in the organic system was low because of incidences of pests and diseases. However, in years with low disease pressure yields were only a few percent lower compared to the conventional yields. Nutrient surpluses of N, P and K were high in the organic system. Nitrogen leaching was below 50 mg L-1 in the organic system. A dilemma still exists between crop yield and nitrate leaching in the conventional systems: lower nitrate leaching is coupled with lower crop yields. The organic system gives relatively low yield however with good results regarding nitrate leaching.

Response of Leek (Allium porrum L.) to Different Irrigation Water Levels Under Rain Shelter

ABSTRACTA pot experiment was conducted to investigate the effects of different water levels on water-use efficiency, yield and growth parameters of leek (Allium porrum L.) and was carried out in the practical research field of Ondokuz Mayıs University in Turkey. Different irrigation water levels were based on the weight changes of each pot and included 5 irrigation treatments [25% (I25), 50% (I50), 75% (I75), 100% (I100) and 118% (I118) times of consumed water]. Decreases in irrigation water resulted in decreases in plant height, stem diameter, leaf and stem fresh weights, leaf and stem dry weights and leaf area, but did not significantly affect leaf number or chlorophyll content. A yield-response factor of 1.26 was obtained, implying that the leek crop was sensitive to water stress caused by deficit irrigation. Comprehensive analysis of yield, water use efficiency, and evapotranspiration, the I75 treatment can be suggested for leek production in water-scarce regions.

Opportunities and risks of biofertilization for leek production in urban areas: Influence on both fungal diversity and human bioaccessibility of inorganic pollutants

The influence of biofertilization with arbuscular mycorrhizal fungi (AMF) on trace metal and metalloids (TM) - Pb, Cd and Sb - uptake by leek (Allium porrum L.) grown in contaminated soils was investigated. The effect of biofertilization on human bioaccessibility of the TM in the plants was also examined. Leek were cultivated in one soil with geogenic TM sources and one soil with anthropogenic TM, to assess the influence of pollutant origin on soil-plant transfer. Leek were grown for six months on these contaminated soils, with and without a local AMF based biofertilizer. Fungal communities associated with leek roots were identified by high throughput sequencing (illumina Miseq®) metagenomic analysis. The TM compartmentation was studied using electron microscopy in plants tissues. In all the soils, biofertilization generated a loss of diversity favoring the AM fungal species Rhizophagus irregularis, which could explain the observed modification of metal transfer at the soil-AMF-plant interface. The human bioaccessibility of Sb increased in biofertilized treatments. Consequently, this latter result highlights a potential health risk of the use of this fertilization technique on contaminated soil since further field investigation is performed to better understand the mechanisms governing (1) the effect of AMF on TM bioaccessibility and (2) the evolution of AMF communities in contaminated soils.

Management of leek diseases in Kashmir valley

Leek is grown commercially in limited areas in the Kashmir valley. Interest in commercial leek production in Kashmir has increased in recent years because of increased markets. Purple Leaf Blotch caused by Alternaria porri is an important disease of Allium spp. worldwide, especially in warm and humid environments, causing up to 60% damage on garlic in India (Bisht and Agrawal 1993) and 59% losses in onion bulb yield. Early symptoms appear on the older leaves as white flecks and under suitable environmental conditions the white flecks expand and produce sunken purple lesions that are often elliptical with a yellow to pale-brown border. The symptoms of Purple Leaf Blotch are frequently indistinguishable from those of stemphylium leaf blight caused by Stemphylium vesicarium; stemphylium leaf blight is characterized by elongated spindle-like lesions on leaves, initially small and white, which later become sunken with a purple colour surrounded by a whitish margin. It was first recorded on garlic in India (Rao and Pavgi 1975). It has been reported on garlic in the South Africa (Aveling 1993), and Brazil (Boiteux et al. 1994)

Sustainable leaf harvesting and effects of plant density on wild leek cultivation plots and natural stands in Southern Quebec, Canada

Overharvesting reduces the populations of wild leek in deciduous temperate forests of North America. Forest farming relying on planted bulbs that are fertilized and selectively harvested could enhance and sustain wild leek production. Density reduction following bulb harvest could improve yield in natural wild leek stands that reach growth-limiting densities. Limiting the harvest to leaves may also provide an alternative form of exploitation, but could slow growth by reducing both carbon and nutrient reserves depending on the timing and intensity of such harvest. Our objectives were to assess the effects of (1) planting density and post-harvest density reduction, and (2) the timing and intensity of leaf harvest on subsequent growth and reproduction of wild leek. Three experiments were established. Bulbs were planted at densities from 44 to 356 bulbs m−2, covering the range surveyed in natural populations. Plots in dense populations were subjected to up to 40 % bulb harvest. In cultivated plots, either half or all the leaves on each plant were harvested, from 15 to 25 days after unfolding. Plants growing in higher density plots exhibited slower growth and reproduction rates, but greater productivity per cultivated area. A similar effect, albeit marginal, was obtained following bulb harvests in natural populations. Harvesting leaves did not affect survival, but delaying the harvest and harvesting only half of the leaves favored subsequent plant growth. We recommend harvesting down to a fixed bulb density rather than harvesting a percentage of bulbs, and harvesting leaves only as ways to ensure sustainable exploitation of leeks.

Effect of plant density and heaving on the production and quality of leek (Allium ampeloprasum L. var. porrum J. Gay)

La cebolla puerro y otras liliaceas, tradicionalmente, se han localizado en valles de climas medios y frios moderados de las regiones andinas y cercanos a los centros de consumo. La produccion y consumo de Allium ampeloprasum L. var. porrum J. Gay, se ha incrementado por sus cualidades condimentarias y por los beneficios de caracter medicinal. Los sistemas productivos implementados para esta hortaliza adoptan tecnologias procedentes de paises con condiciones diferentes a las nuestras. Por lo tanto, para optimizar el cultivo y satisfacer la demanda creciente de mercados especializados, se requiere evaluar practicas agronomicas, lo cual, se constituyo en el proposito del presente trabajo. Se determino el efecto de cinco densidades de siembra y del aporque, sobre el peso, el diametro y la longitud del tallo. Los resultados mostraron que a mayor densidad, el peso y el diametro del fuste disminuyeron, sin ser afectadas por el aporque, mientras que la longitud de pseudotallo presento una relacion directamente proporcional: a mayor densidad, mayor longitud. Se obtuvieron puerros con longitudes superiores a la media del mercado, con las distancias de 20 x 25cm y 30 x 25cm, en donde tambien se lograron los mayores pesos frescos promedios, 354,93g y 354,42g, respectivamente. A una distancia de siembra de 30cm x 5cm, se cosecharon puerros largos y delgados. La practica del aporque es necesaria dentro del sistema de produccion de la cebolla puerro para el blanqueado del tallo; sin embargo, dicha practica no influyo directamente sobre los parametros de produccion, como el peso y el diametro del pseudotallo.

Testing fertilizer, gypsum, planting season and varieties of wild leek (Allium tricoccum) in forest farming system

Wild leek (Allium tricoccum) is an edible spring ephemeral of the eastern deciduous forests of North America that takes advantage of the short period of high light conditions between snowmelt and canopy closure to accumulate the carbon required to complete its annual growth and seed production. In Quebec (Canada), this slow-growing species has been subjected to great harvesting pressure, which forced the provincial government to ban commercial harvest and sales in 1995. An illegal market has since developed and the plant is still under threat. Conservation of existing natural populations might be possible through commercial production of wild leek. To investigate this possibility, we set up plots in four sugar maple forest stands where different organic fertilizer and gypsum (0 or 3,000 kg ha−1) applications were tested, together with two wild leek varieties, and bulb planting season. The two varieties, tricoccum and burdickii, despite morphological differences, are both suitable for cultivation. Planting bulbs in the spring seems more advantageous than in autumn, but these results will need to be confirmed. Fertilized plants exhibited better growth the year following transplantation than did non-fertilized plants. Belowground:aboveground biomass ratios indicated that plants receiving more fertilizer produced larger bulbs, but leaf size did not differ statistically. According to leaf nutrient analysis, fertilizers would need to be applied each year, whereas gypsum (as a calcium source) can be applied less frequently. Our results indicated a high potential for wild leek as a forest crop, at least when the bulbs are planted.

New Insights in the Life Cycle and Epidemics of Phytophthora porri on Leek

AbstractWhite tip, caused by Phytophthora porri, is a devastating disease in the autumn and winter production of leek (Allium porrum) in Europe. This study investigated the disease cycle of P. porri in laboratory and field conditions. Oospores readily germinated in the presence of non‐sterile soil extract at any temperature between 4 and 22°C, with the formation of sporangia which released zoospores. The zoospores survived at least 7 weeks in water at a temperature range of 0 till 24°C. Microscopic examinations revealed that zoospores encysted and germinated on the leek leaf surface and hyphae entered the leaf directly through stomata or by penetrating via appressoria. Oospores were formed in the leaves within 6 days, while sporangia were not produced. By monitoring disease progress in fields with a different cropping history of leek, it could be deduced that P. porri survives in soil for up to 4 years. Disease progress during three consecutive years was correlated with average daily rainfall in the infection period. Disease incidence on leek was reduced when rain splash was excluded by growing the plants in an open hoop greenhouse. Based on these findings, we propose a disease cycle for P. porri in which oospores germinate in puddles, and zoospores reach the leaves by rain splash and survive in water in the leaf axils, from where they infect the plant by direct penetration or via stomata. When conditions become unfavourable, oospores are produced in the leaves which again reach the soil when leaves decay. Secondary spread of the disease by sporangia does not seem to be important.

The role of crop waste and soil in Pseudomonas syringae pathovar porri infection of leek ( Allium porrum)

Pseudomonas syringae pv. porri, the causal agent of bacterial blight of leek, is a current threat for leek ( Allium porrum) production in the Netherlands. The roles of post-harvest crop waste and plant invasion from soil in leek plant infection was investigated with the purpose to gain better understanding on the ecology and epidemiology of this pathogen. In a survey done over 167 leek fields, P. syringae pv. porri was present in 101 fields. About a tenfold higher P. syringae pv. porri average infection rate was recorded in leek plants from fields where post-harvest crop waste was returned than in those from fields where no waste was returned. P. syringae pv. porri could survive for at least 1 month in shredded plant material made from infected plants (mimicking crop waste in practice). Field experiments done over three successive years revealed that leek plants that were treated with crop waste at the nursery and production growth stages consistently showed higher infection rates than plants that remained untreated. Plants that were treated with crop waste only at one of both stages revealed intermediate infection rates. In a plant–soil microcosm study, it appeared that P. syringae pv. porri strain P55R colony numbers in the leek rhizosphere were approximately 4 orders in magnitude higher than in corresponding bulk soils. P. syringae pv. porri was shown to colonize leek roots and cells of the pathogen were also present in the leaves. It was concluded that post-harvest crop waste play an important role in the epidemiology of P. syringae pv. porri in leek production. The following route for primary infection of leek plants is proposed, from crop plant residues via soil to leek roots and plants.

FEED THE CROP OR FEED THE SOIL? A CASE STUDY IN LEEK (ALLIUM PORRUM L.)

The purpose of our study was to assess the role of soil quality parameters in leek production and to assess their importance relative to nitrogen (N) applied as fertilizer. We selected seven (2004) and seven (2005) fields on leek farms in the southern sand district of the Netherlands and measured physical and chemical soil properties. Three N rates (0, 90 and 360 kg N ha -1 as calcium ammonium nitrate; denoted as N 0 , N 90 , N 360 ) were given at each site. Leek (Allium porrum L. 'Kenton') was planted in June-July and harvested next spring. Measured response variables were shoot biomass yield (gross and net, fresh and dry) and shoot N-yield (gross, net) at harvest. Pooled data from both years were analyzed by linear regression. N uptake from unfertilized soil (U 0 ), and topsoil properties soluble organic N (N S0 ), soil organic matter content (SOM), total nitrogen (N tot ) and water content at field capacity (W fc ) all had large and significant impacts on biomass yield and N yield. These five properties (X i ) were correlated and were therefore used alternately in regression models. Effects of soil properties found by regression refer to a shift in the regressor from its 25% to its 75% percentile value, and are expressed here relative to mean yields (both years, all treatments). This normalization facilitates direct comparison with fertilizer effects. Normalized effects of X i variables on biomass yield and N yield were between +0.10 and +0.20. Effects of fertilizer application at N 90 were about +0.10 (biomass yield) and +0.20 (N yield). At N 360 effects were +0.10 to +0.20 (biomass yield) and +0.30 to +0.40 (N-yield). So while N fertilizer strongly promoted N-uptake relative to growth, soil properties X i affected growth and N yield more evenly. With shifts in X i variables, dry matter produced per kg additional N uptake was 1.49 to 1.77 times larger than with extra N uptake resulting from fertilizer application at N 90 . This indicates that soil properties X i promoted yield not only via enhanced N supply. Besides effects of X i properties and N fertilizer, we found significant effects of year, soil texture, pH and inorganic soil N at planting, on biomass yield. Texture parameters F sfine (50-210 μm) and M 50 (median of particle size in 50-2000 μm fraction) had large and additive positive effects on net fresh yield. Apparent recovery of fertilizer N (ANR) averaged 0.35 at N 90 , and 0.17 at N 360 . ANR decreased with higher N so and increased with higher W fc .

Assessing the ecological soundness of organic and conventional agriculture by means of life cycle assessment (LCA)

PurposeSustainable agriculture implies the ability of agro‐ecosystems to remain productive in the long‐term. It is not easy to point out unambiguously whether or not current production systems meet this sustainability demand. A priori thinking would suggest that organic crops are environmentally favourable, but may ignore the effect of reduced productivity, which shifts the potential impact to other parts of the food provision system. The purpose of this paper is to assess the ecological sustainability of conventional and organic leek production by means of life cycle assessment (LCA).Design/methodology/approachA cradle‐to‐farm gate LCA is applied, based on real farm data from two research centres. For a consistent comparison, two functional units (FU) were defined: 1ha and 1 kg of leek production.FindingsAssessed on an area basis, organic farming shows a more favourable environmental profile. These overall benefits are strongly reduced when the lower yields are taken into account. Related to organic farming it is therefore important that solutions are found to substantially increase the yields without increasing the environmental burden. Related to conventional farming, important potential for environmental improvements are in optimising the farm nutrient flows, reducing pesticide use and increasing its self‐supporting capacity.Research limitations/implicationsThe research is a cradle‐to‐farm gate LCA, future research can be expanded to comprise all phases from cradle‐to‐grave to get an idea of the total sustainability of our present food consumption patterns. The research is also limited to the case of leek production. Future research can apply the methodology to other crops.Originality/valueTo date, there is still lack of clear evidence of the added value of organic farming compared to conventional farming on environmental basis. Few studies have compared organic and conventional food production by means of LCA. This paper addresses these issues.

Pre-inoculation with arbuscular mycorrhizal fungi increases early nutrient concentration and growth of field-grown leeks under high productivity conditions

Pre-inoculation of transplants with arbuscular mycorrhizal fungi may increase the in-field P uptake through an increased exploitation of the soil volume and, thereby, reduce the need for P fertilizer application. The objective of this study was to investigate how pre-inoculation influences the post-transplanting rate of mycorrhizae development, nutrient uptake and growth of field-grown leek plants (Allium porrum L.) at various P levels. Field experiments were carried out in normal field soils supporting high crop production levels. This work demonstrated that pre-inoculation increased the post-transplanting rate of mycorrhizae development, the shoot and root concentration of P, Zn, Cu, and N, and the plant production. Therefore, module-raised pre-inoculated transplants should be adopted as a management strategy in leek production in order to ensure sufficient mycorrhization of young plants for uptake of P and, thereby, reduce the need for application of fertilizer P.

First Report of Tomato spotted wilt virus in Leek (Allium porrum) in the United States

Tomato spotted wilt virus (TSWV) is a member of the family Bunyaviridae. It has many important crop hosts including tomato, pepper, tobacco, peanut, and onion. In Georgia, Vidalia onions (Allium cepa), a close relative of leek, can be infected by TSWV and Iris yellow spot virus (IYSV), which is another thrips-vectored tospovirus (2). For this reason, samples of leek transplants with virus-like symptoms in one field at the border of Georgia and Florida were tested for the presence of TSWV and IYSV. The transplants had been grown from seed in a greenhouse at the same location. The sampled plants exhibited extended bleaching of leaf tips and necrotic lesions. These symptoms were also seen on onion plants infected with TSWV and IYSV. The only natural infections of leek with IYSV have been reported thus far only from Reunion Island (4) and Slovenia (1), but to our knowledge, TSWV has not been reported as a pathogen of leek. Green tissue near the necrotic lesions and bleached tips of one symptomatic leaf per plant was sampled and analyzed using a double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) (Agdia, Inc., Elkhart, IN). Of 90 plants tested, eight were positive for TSWV and none were positive for IYSV. Leek samples testing positive using ELISA were blotted onto FTA cards (Whatman Inc., Brentford, UK) to bind viral RNA for preservation and then processed according to the manufacturer's protocol. Punch-outs from the FTA cards were used for reverse transcription polymerase chain reaction (RT-PCR) with the TSWV-specific forward primer (5'-TTAAGCAAGTTCTGTGAG-3') and reverse primer (5'-ATGTCTAAGGTTAAGCTC-3') (3) to confirm the identity of TSWV. The primers are specific to the viral nucleocapsid gene. An amplicon of the expected size (774 bp) was produced from TSWV ELISA-positive leek plants, but not from healthy controls. TSWV has been found in many plants worldwide, but to our knowledge this is the first report of TSWV infecting leek. The effect that TSWV has on leek production is currently unknown.

COMPARISON OF SPLIT NITROGEN APPLICATION STRATEGIES IN LEEK (ALLIUM PORRUM) TO REDUCE N FERTILIZATION ON SANDY SOILS IN THE NETHERLANDS

High nitrogen (N) fertilization to maximize production of leek (Allium porrum L.) combined with low N recovery can lead to considerable nitrogen pollution of the environment. A field trial was conducted in 2002 and 2003 on a sandy soil in the Netherlands. To synchronize N supply and N demand, two strategies of sequential split nitrogen application (SNA) were compared: 1) SNA-soil: in which the split N applications are the difference between standardized crop demand and the available amount of mineral N in the soil for each period; 2) Crop Scan method: in which the split N applications are derived from comparing the actual crop nitrogen status to the desired nitrogen status, using crop reflectance measurements and a crop growth model. Total fertilizer application according to Crop Scan method in 2002 saved 65 kg N ha-1 compared to recommendation of SNA-soil, maintaining maximal production. In 2003 the total N application of SNA-soil and Crop Scan were respectively 95 and 113 kg N ha-1, whereas a N application of 45 kg N ha-1 was sufficient. The Crop Scan method overestimated the N application needed in 2003 because it did not account for the high mineral N content in the soil. SNA-soil overestimated the N application needed in autumn in both years. Combination of Crop Scan measurements, to assess plant N need, and soil N analysis may cover the flaws, which each method separately showed.