Browsing by Subject "peruna"

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  • Kymäläinen, Anni (Helsingfors universitet, 2013)
    In Finland, potato is cultivated on more than 22 000 hectares, which makes it one of the most important crops. Potato is considered drought sensitivive because of it´s shallow roots. Thus, irrigation is recommended to improve not only the yield but to ensure good tuber quality. However irrigation is increases production costs. Nitrogen fertilization also affects yield and tuber quality but excess nitrogen can increase costs, nutrient leaching and reduce tuber quality. Thus, the equipment that can be used to estimate nutrient deficiencies have become more common. The effect of irrigation and nitrogen fertilization on growth and tuber yield of potato was investigated during 2001 – 2003 at Potato Research Institute in Lammi, Finland. Irrigation methods were surface irrigation and subsurface drip irrigation. Nitrogen was applied as a single dose when planting or as sidedress. Further interest was to find out whether SPAD values could be used to evaluate both the demand and timing of potato nitrogen fertilization. Irrigation did not affect potato development, tuber yield or starch content. Irrigation methods had no effect on tuber yield either. However, irrigation reduced the yield of marketable tuber yield. The benefit of drip irrigation was the possibility of combined irrigation and fertilizer application. Nitrogen increased tuber yield. The potato stand that received nitrogen as a single dose produced the greatest yield. However, even the potato stand which did not receive nitrogen produced quite large yield, over 30 tn/ha. In 2003, the stands which were given sidedress nitrogen with drip irrigation produced even greater yield than the ones that had been given nitrogen as a single dose. The stands which did not receive nitrogen had highest starch content. The SPAD values were used when estimating the demand of nitrogen fertilization with drip irrigation. SPAD measurements are easily conducted and non-destructive. SPAD values can be used to estimate the demand and timing of fertilization, even though there seems to be slight delay until the values indicate the nutrient deficiency.
  • Solala, Kari (Helsingfors universitet, 2009)
    The literature review of this thesis deals with light, different light sources and their properties. LED (Light Emitting Diode) light was specially taken into consideration, because the use of LED lights will increase in general illumination. The literature review also deals with the quality changes of dairy products and potatoes caused by exposure to light. The aim of this study was to search for such a spectral distribution of light which would cause only minor changes in the sensory quality of milk and the surface colour of potatoes. Objective was to also find out if there is a difference between the effects of fluorescent light and LED light on the quality of milk and greening of potatoes. Reduced (1,5 %) fat milk and new potatoes were used as testing materials. The milk in commercial carton board packages was exposed to six different light sources: white fluorescent lamp, white LED and LED of four different colours. The potatoes packed in transparent LDPE (Low Density Poly Ethylene) bags were stored under five different light sources: white fluorescent lamp, white LED and LED of three different colours. The light intensity at the surface of the packages was about 1000 lx in both studies. In the milk study, the effects of light were evaluated with a sensory method using descriptive analysis. In the potato study, the light effects were analysed with colour measurements (avalue) using a spectrophotometer and with surface temperature measurements using a laser thermometer. Sensory evaluation of milk there resulted in few statistically significant differences in the intensity of the attributes between the milks stored under different light sources. Light exposure caused a rapid greening of potatoes in every illumination. According to colour change percentage, the greening order under different lights was: white LED < yellow LED < green LED < turquoise LED < fluorescent light. The potatoes which were stored in dark had no change in their surface colour. The surface temperature of potatoes increased most under white LED and turquoise LED lights. A spectral distribution of light which would have caused less changes in sensory quality of milk than commonly used fluorescent light was not found in this study. The results showed, however, that in addition to blue light which has always been considered the most harmful for milk the red light also caused remarkable quality changes. Based on the results of this study, it could be suggested that under the LED lights the quality of packed milk retained its quality characteristics at least as well as under the fluorescent light. There were differences between the effects of different lights on the greening of potatoes. White and yellow LED light caused less greening of potatoes than the other lights. The strongest greening of potatoes was observed under the fluorescent light.
  • Örö, Nelly (Helsingin yliopisto, 2018)
    Meat and bone meal is a by-product of rendering industry. It contains significant amounts of nutrients, for example 2720 tonnes per year phosphorus in Finland. The use of meat and bone meal in agriculture ceased because of the mad cow disease in 1994. Meat and bone meal has been proved to nearly equal mineral fertilizers both economically and in fertilization effect with many crops. The use of high phosphorus content meat and bone meal as fertilizer decreases the need for non-renewable phosphorus resources and closes food system nutrient cycles. The objectives of this thesis were to consider the suitability of meat and bone meal in potato production and to estimate the recycling potential of meat and bone meal in potato production in Finland. The recycling potential was calculated as a ratio between the annual phosphorus demand in potato production and the amount of phosphorus in meat and bone meal produced in Finland. The mean yields of potato as well as the fertilization rates in agri-environment measures and the plant-available proportion of meat and bone meal were used in calculation. The annual phosphorus demand of potato production was estimated as 1100 tonnes and the amount of plant-available phosphorus in meat and bone meal was estimated as 1630 tonnes. This number includes a category 1 disease risk material which must currently be disposed of. The recycling potentials of meat and bone meal were calculated as 67 % and 74 % for all the material and excluding the category 1 material, respectively. Consequently, the amount of phosphorus in meat and bone meal can supply the demand in potato production. Meat and bone meal is a long-term phosphorus fertilizer and suitable for potato production in Finnish conditions if nitrogen and potassium are supplemented to meet the crop’s demand with other fertilizer products. It’s also an advantage that meat and bone meal is accepted in organic production. In a recycling nutrients point of view, the utilization of meat and bone meal as a fertilizer for instance in potato production is a good opportunity to return nutrients to the agroecosystem’s cycle.
  • Helsky, Tuija; Anttalainen, Mikko; Palviainen, Sakari; Kemppainen, Pirkko; Lehto, Marja; Salo, Tapio; Mäkelä, Mika; Tuominen, Ari; Piilo, Tiina (Suomen ympäristökeskus, 2006)
    Suomen ympäristö 57/2006
    Tässä raportissa esitetään parhaan käytettävissä olevan tekniikan (BAT) mukaisia tuotantomenetelmiä ja päästöjen käsittelymenetelmiä perunan ja juuresten kuorimoille ja niille raaka-ainetta toimittaville yrityksille. Suomessa on nykyisin noin 200 kuorimolaitosta, jotka toimittavat kuorittua perunaa ja juureksia suurkeittiöille ja elintarviketeollisuudelle ja laitosten määrä on edelleen kasvussa. Lisäksi on monia satoja viljelijöiden ja tukkukauppiaiden varastoja, joissa esikäsitellään kuorimojen raaka-aineeksi toimitettavia perunoita ja juureksia lajittelemalla, erottamalla multaa ja pesemällä. Suurin osa kuorimolaitoksista on perustettu maatilan yhteyteen käsittelemään pääasiassa tilalla viljeltyjä raaka-aineita. Monet laitokset käyttävät myös muualla viljeltyjä raaka-aineita. Kuorinnassa syntyvän kuorimassan hyötykäyttö tai muu käsittely ja toiminnasta syntyvät jätevedet ovat ympäristönsuojelun kannalta merkittävimmät asiat kuorimolaitoksilla. Kuorimassa on koostumukseltaan olennaisesti samanlaista kuin käytetty raaka-aine ja soveltuu periaatteessa erinomaisesti eläinten, lähinnä nautakarjan, rehuksi. Myös lajittelutähteet voidaan hyödyntää toimittamalle ne mahdollisuuksien mukaan rehuksi kotieläimille tai riistalle. Lajittelutähteiden, eli epämuodostuneiden, pilaantuneiden sekä ali- tai ylimittaisisten perunoiden tai juureksien, määrään voidaan vaikuttaa kasvukauden aikaisilla viljelytekniikoilla ja toimenpiteillä. Jätevesikuormituksen vähentämiseksi on ensisijaisen tärkeää kerätä kuorimassa solunesteineen talteen niin, että solunestettä ei pääse käsittelyyn johdettavan jäteveden joukkoon. Tällöinkin muodostuu kuorinnan jälkeisistä huuhteluista, tilojen ja laitteiden pesuista ym. melko väkeviä jätevesiä, joiden kuormitus on kuitenkin murto-osa solunestepitoisista vesistä ja joiden käsittely on olennaisesti helpompaa kuin väkevien, paljon solunestettä sisältävien jätevesien. Raportti on tarkoitettu suomalaisten yritysten ja viranomaisten käyttöön parhaan käytettävissä olevan tekniikan määrittelemiseksi erityisesti ympäristölupien käisttelyssä. Se antaa myös yleisölle tietoa alalla sovellettavista tekniikoista.
  • Seppälä, Ulla (University of Helsinki, 1997)
  • Matikainen, Laila (Helsingin yliopisto, 2019)
    This Master's thesis compares the commercial cooking tests of potatoes in Finland and Europe. The cooking type comprises the structural properties of potato, which are described e.g. in terms of floury and waxy or types A-D. Other measures of cooking quality, such as color, taste and odor, were excluded from the work. The main focus of the thesis was on the survey of European cooking type tests and on the comparative study of descriptors for different varieties. As the use of descriptors and terminology differ slightly from one country to another, the significance of the differences in the resulting cooking type result was also considered. In the study, seven varieties with seven different meters and a total of 12 different measuring methods were compared. The key method of the thesis was sensory evaluation by descriptive method. The descriptors were used as unambiguously as possible, such as evaluating flouriness by appearance and by palpation in the mouth. In addition to sensory evaluations, experiments with structure analysis, hyperspectral imaging, and color measurement were included in the study. The purpose of the analysis was to look at the descriptor ensembles, and to observe their dimension on the axis waxy - floury and possible other independent dimensions that would diversify the description of the cooking quality. The results were examined statistically by means of generalized linear models, correlations and principal component analysis. The thesis concluded that there are some differences between European ways of determining the cooking type, and in borderline cases, different results are possible. In general, European descriptor ensembles are strongly built to support the waxy-floury axis. In addition to the descriptor ensembles, the cooking type determination include procedures and calculation methods and cannot be separated from the whole. The results of the study support the fact that hardness/softness is an independent dimension, and hardness determined by the texture analyzer clearly distinguished the varieties. In sensory comparison, external observation and mouthfeel evaluation produced similar results, except for hardness assessment. The instrumental methods distinguished the varieties more clearly than sensory evaluation. Disintegration analyzed by color measurement and starch content is a viable combination for cooking type determination.
  • Tall, Anna (University of Helsinki, 2007)
    Julkaisuja / Helsingin yliopisto, soveltavan biologian laitos
  • Andersson, Johanna (Helsingin yliopisto, 2014)
    Bacterial soft rot and blackleg are amongst the major diseases of potato (Solanum tu-berosum L.). In Finland Pectobacterium atrosepticum, Pectobacterium carotovorum subsp. carotovorum, Pectobacterium wasabiae and Dickeya-species cause rotting of the tuber and softening of stems on potato. These diseases cause major postharvest losses and weaken the quality of the crop, which is a problem in seed potato production. The aim of this study was to determine whether the antagonistic bacteria are toxic to in vitro plants, as well as to study the ability of the antagonistic bacteria to spread inside or on the in vitro plants. It was also investigated if the antagonistic bacteria can prevent soft rot of potato in in vitro plants, as well as the ability of the antagonistic bacteria to prevent the spreading of soft rot bacteria from soil to the plants. This study was carried out in laboratory and in greenhouse conditions in the University of Helsinki at the Department of Agricultural Sciences. As potato material cultivar Melody was used and as antagonistic bacteria 10 different bacteria were chosen: Serratia plymuthica A30 (NR), Flavobacterium sp. strain B17 (A3), Agrobacterium sp. (A6), unsequensed bacteria isolated from potato root (A4), Serratia j5h9 (S1), Alcaligenes faecalis (R8), Bacillus M1ju27 (BC1), Bacillus S3H53 (BC2), Burkholderia M1423 (BK3) and Pseudomonas S2h50 (PS3). Dickeya solani and Pectobacterium carotovorum were used as pathogens. Although BC1, BC2, S1 and BK3 antagonists did not influence negatively the potato in vitro seedling growth they did not, however, properly prevent soft rot of in vitro plants. Further studies on preventing soft rot of in vitro plants is needed.
  • Aho, Jenna (Helsingfors universitet, 2017)
    In a previous study, Pectobacterium strains were isolated from rotten potato tubers and stems. Strains were identified as P. carotovorum subspecies carotovorum by their biochemical properties. In acnA gene sequence analysis the strains isolated from diseased potato stems were different from P. carotovorum subspecies carotovorum type strain and also from strains isolated from rotten potato tubers. However, the strains isolated from rotten potato stems were not able to cause typical blackleg symptoms, like rotting of stems, when inoculated in potato plants. The focus of this master’s thesis was to further study if the new strains are pathogenic in nature or whether they could have arrived to already rotten potato tissue as secondary infection. One goal was to find out if the strains can produce compounds that inhibit growth of known blackleg pathogens, and could they make already contaminated potatoes disease free in a field. This was tested in vitro as well as in a field trial with two potato varieties. As a result the strains isolated from stems were able to produce toxic compounds that inhibited the growth of several common soft rot and blackleg pathogens, whereas compounds produced by the strains isolated from tubers had no effect on the growth of the other bacteria. This suggests that the strains present in stems have properties that make it possible for them to spread from the environment to already infected stem lesions and compete with blackleg and soft rot bacteria already present in the tissue. Blackleg symptoms were absent during the field trial, but in some cases the inoculations caused soft rot of tubers and stunted growth of the inoculated plants. The two potato varieties used in the field trial, Rikea and Fontane, had a different response against the used strains. Although the in vitro results suggested that some of the strains that were originally isolated from stems could act as biological control agents, the results from the field trial contradicted this indicating that the strains might have pathogenic properties, which makes them unsuitable as biological control organisms.
  • Pennanen, Laura (Helsingin yliopisto, 2018)
    The potato virus Y (PVY) is a type member of the family Potyvirus which infects the nightshade family (Solanaceae) plants. Economically it is considered to be the most siqnificant problem in seed potato production worldwide. Meaningful methods to prevent economical damage caused by PVY are the production of certified seed potato and breeding of PVY-resistant cultivars. The starting point of breeding is identifying different PVY strains. Sequence information from HCPro protein (HCPro) and coat protein (CP) regions are essential to be able to identify different PVY strains and their recombinant forms. The aim of this study was to express the variation in CP and HCPro regions of PVY. This was done by sequencing PVY data from Finlands seed potato fields from year 2015 and comparing it to Yanping Tians (Doctor of Science, Agriculture and Forestry) sequence data from the same area from the years 2006 and 2007. The PVY positive samples used in this study were collected in 2015 in a virus screening test executed by Evira. The screening was done by using ELISA test. The comparison in this study was executed by aligning CP and HCPro regions from all samples and examining the regions by nucleotide and aminoacid level. Comparison was also executed by creating phylogenetic trees from aligned sequences. On the findings of this study the recombinant strain PVY-NTN was the most common strain in Finlands seed potato fields in 2015. Occurence of PVY-O strain was reduced significantly when compared to data from 2006 and 2007. The seven PVY-NTN samples that were examined in this study had a typical aminoacid region to PVY-O strain. This region covers aminoacids R269–K270 and is absent from a known recombinant PVY-NTN ”Nevski” and it is also a singular finding when compared to Yangping Tians samples. However, this change in aminoacid structure did not seem to provoke resistant genes in known potato cultivars to recognize these samples. It is plausible that PVY profits from this new mutation in its aminoacid structure, but this cannot be point out on the bases of this study.
  • Saarela, Olli (Helsingfors universitet, 2016)
    The potato virus Y (PVY) is a member of the family Potyvirus, which is the largest plant pathogenic virus family. PVY is one of the most important pathogens of the nightshade family (Solanaceae) plants. PVY is a particular problem in seed potato production, as well as in tomato and pepper production. Some PVY races cause necrotic symptoms (PTNRD) in potato tubers, which will make the tubers unsuitable for use. This thesis studied the ability of several recombinant strains of PVY to infect these three plant species. First objective was to find out which recombinant strains can infect the plants systemically and whether some of them will cause PTNRD symptoms in potato tubers. Secondly, we wanted to find out what parts or even specific amino acids in the HCpro of PVY affect the infection ability of the virus. This was done by comparing the genomes of the recombinant and wild type viruses and based on the experimental data. Finally, we wanted to see if the mutations would persist in the virus genomes for the duration of the infection. The test plants were infected by applying virus contaminated plant juice and grinding powder on the plant leaves. Plants were first grown in growing chambers and then transferred to a greenhouse. The plants were tested for viral infection with DAS-ELISA for three times during different stages of growth. To investigate whether the mutations had persisted in the virus genome, the viral RNA was isolated, multiplied with RT-PCR and then sequenced. Most of the recombinant viruses were not able to systemically infect either of the potato cultivars tested (cv. ‘Nicola’ and cv. ‘Annabelle’). ‘Nicola’ was more susceptible than ‘Annabelle’. The Tyr323Phe-mutation in the HCpro seemed to have a positive effect on the viruses ability to infect ‘Nicola’ in recombinant O5ON-F. PTNRD was caused by recombinants O5NNO45, N605-F and O5ON-F only in ‘Nicola’. Tyr323Phe-mutation had persisted in the N605-F during the infection. Tomato cv. ‘Moneymaker’ was more resistant towards the recombinants than cv. ‘Ildi’, though both cultivars were considerably more susceptible towards the recombinants than either of the potato cultivars or the pepper cultivars. The pepper cultivars tested were resistant towards PVYN605 and PVYOUK.
  • Solarmo, Elina (Helsingfors universitet, 2011)
    Potato virus Y (PVY) is currently the most yield and quality limiting pathogen of the cultivated potato (Solanum tuberosum L.) globally. While yield losses specific to PVY are hard to measure in presence of other pathogens they are estimated as 20 to 80 %. The most important way by which the virus spreads are virus-infected seed potatoes. High quality seed potato is very important for food, food industry and starch potato production. Visual inspection of the potato plants underestimates usually the real percentage of PVY infection. Laboratory tests provide more accurate results about the incidence of infections. The problem with testing PVY is that the virus cannot be detected reliably from samples taken from dormant tubers. Different treatments have been used to break dormancy of tubers e.g. chemicals (Rindite, bromoethane), plant hormones (gibberellic acid) and adjusted storage temperatures (cold and heat treatment). The results have varied a lot. In this thesis an experiment with oxygen-carbon dioxide (O2 40 %-CO2 20 %) treatment with different periods of time was used to end dormancy of potato tubers. The aim was to test whether the treatment could end dormancy of tubers earlier than normally and to see if the treatment has an effect on detection of PVY. One aim was also to test how reliably PVY could be detected from tuber and sprout samples compared with potato leaf samples which are normally used for virus testing. Results from the sprouting treatment were variable and could not be readily generalized. The treatment had no effect on the detection of PVY incidence. When the different plant materials were compared with each other, tuber material showed the lowest PVY percentage when compared to sprouts and leaves. Testing sprouts also underestimated the incidence PVY. The best material for testing PVY in potatoes were the leaf samples.
  • Ikonen, Teemu (Helsingfors universitet, 2002)
  • Helsingin yliopisto, kulttuurien tutkimuksen laitos, kansatiede (Helsingin yliopisto, kulttuurien tutkimuksen laitos, kansatiede, 1974)
  • Rahko, Juhani (Helsingfors universitet, 2012)
    Potatoes (Solanum tuberosum) are an important crop for the food security of developing countries, and farmed area of potatoes in those countries is expanding constantly. It would be important to solve the problems of potato production and distribution in Tanzania. The research problem of this thesis was to examine the value chain of potatoes in Tanzania and factors that prevent the industry’s development. Furthermore, the aim was to evaluate agricultural policies affecting potato value chain and illustrate the present state of potato production and marketing chain in contrast to other crops. The research was conducted by executing 14 semi-structured expert interviews in Tanzania in June 2011. In addition to this, two researchers answered in written form. The interviewees were researchers, agricultural extension officers, managers of nongovernmental organisations, dealers of agricultural market place, a agricultural project coordinator, and officials from the ministry of agriculture as well as from the ministry of trade and marketing. Theoretical framework in this thesis is based on structure-conduct-performance (SCP)-paradigm. Moreover, the basic conditions and public policy of the industry are to be found out. The results indicate that the government does not affect much to the operation nor the development of the potato value chain: potato is not the government priority in Tanzania. On the other hand, there are no straight policy measures or institutional barriers that are hindering the conditions of smallholders or other actors in the chain, either. Bad seed quality is most likely the biggest challenge on the production part. Difficulties to get loans and the lack of investments and farmers’ groups are hindering the production. The biggest infrastructural issue is poor road network in the countryside. As a suggestion based on the results is that two instances should be created: a national potato board and marketing centres in the villages. The prerequisite for those instances to be possible to establish and function well is the activity of the government. Especially to operate the market centers properly, it is important that the village leaders and farmers would be committed to its activities.
  • Vänttinen, Kristofer (Helsingfors universitet, 2017)
    Potato (Solanum tuberosum L.) is a plant that belongs to the group of nightshades (Solanaeceae). Enzymatic browning occurs in potato tuber when it is peeled or bruised. Polyphenols in tuber (e.g. chlorogenic acid and tyrosine) are oxidised into o-kinones by polyphenol oxidase. When kinones polymerise, melanins are formed. These compounds cause the brown colour in potato tubers. Sulfites are used as food additives in potatoes preventing enzymatic browning reactions. The maximum permitted usage levels in European Union are 50 mg SO2/kg in peeled potatoes, 100 mg SO2/kg in cooled and frozen potatoes and 400 mg SO2/kg in dried potato products (No 1333/2008). The allergy threshold limit for sulfites in food products is 10 mg SO2/kg (No 1169/2011). The objectives of this study were 1) to determine the sulfite content in various potato products on the market, 2) to examine the binding of sulfite on potato in the relation with temperature, time and concentration, 3) to examine sulfite content in different potato varieties and 4) to compare the HPLC results with the rapid determination methods. The objectives in the literature review were to study the use of a potato as a food component, industrial peeling of potatoes, enzymatic browning reactions, sulfites and their analytical methods. In this study, a modified RP-IP-HPLC-PC (Reversed Phase Ion-Pair High Performance Liquid Chromatography Post-Column) method was used. For rapid determination methods, two kits were used: Merck MQuantTM Sulfite Test and Neogen ALERT® for Sulphites in Seafood. 18 food products were selected to this study (6 mashed potato flours, 3 fresh products and 9 frozen). Box-Behnken Experimental Design was carried out prior to the examination of sulfite binding in different potato varieties (Belana, Nicola, Siikli, Gala, Jelly, Melody, Bellarosa, Afra and Puikula). Sulfite was found in four mashed potato flours and three fresh potato products. In flours, the content of sulfites were below the maximum limit, but over the allergy threshold limit (10 mg SO2/kg). However, sulfite was labelled. In fresh products, the content of sulfite in the first product was below the allergy threshold limit, the second product fell under the maximum limit but the third product exceeded it. In the first product sulfite was not labelled but in the other two ones it was. In Box-Behnken Experimental Design, results were analysed with one-way ANOVA. Concentration (%) had the biggest influence on sulfite binding on potato (p = 0,000) and then time (s) (p = 0,0079). Temperature (°C) didn’t have any statistical significance (p = 0,3513). According to the results, the best measurement point was 1 %, 60 s, +5 °C. The peeled potato varieties were sulfite treated in these conditions. Statistical analysis was carried out with one-way ANOVA and then Tukey HSD. According to the results, there was a statistical significance (p = 0,000) in sulfite binding in different potato varieties. Sulfite was bound most in Puikula (67,0 ± 8,8 mg SO2/kg) and least in Gala (19,7 ± 5,3 mg SO2/kg). The most difference within the varieties in sulfite binding were with Belana, Gala and Puikula. Jelly had a difference only with Gala. In rapid determination methods, ALERT® was more accurate than MQuantTM. ALERT® could be applied on the surface of the sample contrary to MQuantTM that needed 3 or 5 times dilution before measurement. ALERT® is a good choice for semiquantitative rapid method. MQuantTM, however, is not suitable for rapid measurement of sulfites in potato products.
  • Nikkari, Saara (Helsingfors universitet, 2013)
    A field experiment was conducted at Potato Reseach Institute during 1997-2002 in Lammi, Finland. The first aim of the work was to find out the suitability of three- and four-year crop rotation on potato production. The second aim was to investigate the effect of three different tilling methods and four different preceding crops on yield and quality of potato. The tilling methods were autumn and spring ploughing and light cultivation. The preceding crops were barley with straw left in the plots, barley with straw harvested, oat with straw harvested and two-year-grass. There were no differences on yield or quality of tubers between the studied crop rotations. The tuber yield did not differ between the tilling methods or the preciding crops. There was an interaction between all studied rotation and tilling methods. Three-year rotation resulted in approximately 5 % higher tuber yield and 14 % higher marketable yield following spring ploughing and light cultivation in comparison to autumn ploughing. However, four-year rotation resulted in an opposite result, since the tuber yield was 7 % and marketable yield 17 % higher following autumn ploughing in comparison to both spring ploughing and light cultivation. The most effecting factor on tuber quality was the two-year-grass as a preceding crop. Starch content was a little less than one percentage point higher following grass in comparison to all other preceding crops studied. Plant stand was also slightly sparser and tubers were slightly larger following grass in comparison to other preceding crops studied. This was due to grass lumps which caused problems in planting and resulted in uneven plant stand density. There were more green tubers following grass in comparison to other preceding crops studied. The starch content was a little less than one percentage point lower following spring ploughing in comparison to other tilling methods. Common scab was observed somewhat more following spring ploughing. The light cultivation resulted in the highest number of green tubers. Three- and four-year crop rotations seem to fit for potato cultivation, and oat and barley are suitable as preceding crops for potato. Yield is not affected when spring ploughing- and light cultivation is applied with cereals as preceding crops. The two-year-grass is also suitable preceding crop for potato. It increases the tuber starch content, even tough it can decrease the quality. Thus, autumn ploughing is the best option as a tilling method to be used for grass as a preceding crop in potato cultivation.
  • Korpi, Terhi (Helsingin yliopisto, 2019)
    The production of potato starch leads to large amount of separate cellular liquid. So far industries haven’t had use for this potato juice, and it has been distributed back to fields. This causes unnec-essary expenses for industries as well as raises the risk of nutrients leaching. These factors have raised the interest in developing processes for further processing of the cellular liquid. The main interest of industries is still potato starch, which is why they are interested in what affects the nitro-gen and protein content of starchy potatoes and what is their relationship to starch content. This study was done in unison with Perunantutkimuslaitos (Petla) during the starch potato variety test in summer of 2016. In this study the effects of four cultivational factors (site, cultivar, nitrogen fertilization level and time of harvest) were examined via the changes in nitrogen and protein levels in tubers. The weather factors were considered from the data collected from the nearest measure-ment location of the Finnish Meteorological Institute. The goal of the study was to find out what are the factors that have the biggest effect on the changes in nitrogen and protein contents of starch potato variants. Cultivars were found to have the biggest effect, but the site as well as sowing time and weather conditions had an effect as well. Correlation between starch and nitrogen content was not observed. In addition, the goal was to determine the ideal combination of cultivational factors for optimal starch, nitrogen and protein yield. Early variants do have more secure production of yield, since late variants are easier affected from different growing conditions. Raising the level of fertilization to 100 kg/ha was the optimum based on the results of this study, but only if time of harvesting was opti-mized as well.
  • Helsingin yliopisto, kulttuurien tutkimuksen laitos, kansatiede (Helsingin yliopisto, kulttuurien tutkimuksen laitos, kansatiede, 1974)