Phosphorus application strategies in potato

Phosphorus (P) is an essential element that plays an important role in carbohydrate metabolism and energy transfer systems in all plants. Sufficient P supply is therefore essential for providing adequate food, fibre and fuel for society. In potato, P deficiency reduces yield and tuber number due to reduced radiation interception by the canopy. Phosphorus is a limited, non-renewable resource. When lost to water bodies, P causes environmental problems such as eutrophication. Potato fields may be a significant contributor to P loads to water due to high P recommendations and a tendency for P leaching in soils where the P sorption/binding capacity is saturated. Efficient use of P in potato cultivation is therefore crucial in order to reduce P consumption and environmental impacts. The thesis improves the current understanding of potato P requirements as regards optimising P application strategies, use efficiency and potato tuber yield. The results show that split P applications can improve P recovery by 25%, particularly on soils with low P content and low buffering capacity, and can improve physiological P use efficiency (PPUE) where P availability is limiting yield. Irrigation and subsoiling can both significantly improve P recovery, PPUE and yield. Foliar application does not improve PPUE, but can increase P concentration and yield if the plant is supplied with sufficient water. However, foliar P application should not be used as a general strategy, but can be recommended where the soil buffering capacity is extremely high. It is shown in this thesis that many Swedish soils contain sufficient amounts of P to support optimal growth and are no longer responsive to P fertilization. To determine the responsiveness of potato yields to P, data on soil organic material, pH, soil buffering capacity and varietal characteristics are needed, in addition to the amount of P-extractable with ammonium lactate (P-AL value) used in Sweden today. More sophisticated P recommendation models which take these parameters into account are urgently needed. As long as yield effects from P fertilization cannot be predicted, excessive P fertilization will probably continue, resulting in waste of a non-renewable resource, eutrophication of the aquatic environment and reduced farm profits. The findings in this thesis contribute to understanding the complex picture of P acquisition in potato and, hopefully, to more efficient use of the non-renewable P resource

Potato yield and tuber set as affected by phosphorus fertilization

In order to minimize phosphorus (P) leaching from potato cropping systems, P recommendations based on facts regarding the influence on the potato plant is needed. A literature study and a practical experiment were conducted in order to determine potato yield and tuber set as affected by Pfertilization. The influence of soil moisture on P availability and the effects of foliar‐ P application were also investigated. Five different nutrient P treatments ranging from 0 to 0.3 g/pot were evaluated. Each nutrient P treatment was divided into 8 doses and applied weekly to plantlets grown in 50% pumice stone‐ 50% peat. Two different soil moisture levels were tested, "moist treatment" ranging from 0.35 to 0.45 g cm‐3 and "dry treatment" ranging from 0.25 to 0.35 g cm‐3. Foliar‐ P applications were applied 16 and 26 days after emergence (d.a.e.) in line with common practice recommendations. Nutrient P treatments significantly effected the total fresh weight of tubers, shoots and tuber number. The moist treatment gave significant higher yield of both tubers and tuber number compared to the dry treatment which could beexplained by an increased P uptake. The foliar‐ P application resulted in higher tuber yield only in plants with low P status within the moist treatment; indicating that plant water and P status might be important for P uptake through leaves. The foliar‐ P applications however, gave no significant effects on tuber number.I arbetet mot ett minskat forsforutsläpp från Sveriges potatisodlingar krävs grundläggande kunskaper om fosforns inverkan på potatisplantan för att korrekta rekommendationer skall kunna ges till våra odlare. I detta arbete som innefattar både en litteraturstudie och ett praktiskt odlingsförsök har fosforns inverkan på knölsättning och skörd studerats i detalj. Även markfuktens inverkan på fosforns tillgänglighet och bladgödslingens effekt på potatisplantan har studerats. I försöket som är utfört i artificiella växtkammare har fem fosforgivor som varierar mellan 0 och 0,3 g fosfor per kruka testats. Varje behandling delades upp i 8 givor och tillfördes en gång i veckan till varje individuell planta som var planterad i ett substrat som bestod av 50% pimpsten och 50% torv. Två olika fuktighetsnivåer testades, en ”fuktig behandling” som varierade från 0.35 till 0.45 g cm‐3 och en ”torr behandling” som varierade från 0.25 till 0.35 g cm‐3. Bladgödslingen utfördes vid två tillfällen, första behandlingen gjordes 16 dagar efter uppkomst  och den andra efter 26, helt enligt de rekommendationer som finns. Fosforgivorna påverkade både vikt och knölantal signifikant liksom hög markfukt som gav högre skörd och fler knölar vilket kunde knytas till ett ökat fosforupptag. Bladgödslingen av fosfor gav en signifikant skördeökning endast i plantor med låg fosforstatus i de fuktiga leden vilket antyder att plantans vatten och fosforstatus kan vara av betydelse för fosforns upptag genom bladen. Bladgödslingen resulterade dock inte i fler antal  knölar

Droppbevattningens inverkan på kvalitet och kvantitet hos Solanum tuberosum L i jämförelse med konventionell spridarebevattning

A literature study and a field trial have been carried out in order to investigate the physiological response of potato plants to different soil moisture levels. Higher yield, quality and number of tubers can according to the literature be obtained if constant high soil moisture is kept during major parts of the growing season. A field trial was set up where drip irrigation was used as an alternative to conventional irrigation techniques to maintain high and constant soil moisture. The application of water in the drip irrigated area was monitored and adjusted on a daily basis so that the soil moisture stayed as close as possible to the recommended level. The sprinkle irrigated area was irrigated according to traditional practices with approximately 35 mm every 7th to 10th day depending on the whether. The result from the field trial was in line with the information found in literature; constant high soil moisture gave on average 11 % higher yield, higher quality and higher number of tubers. The marketable yield increased with 28 % in the drip irrigated area compared with the sprinkle irrigated area. The conclusion from this study is that drip irrigation can be used as a cost effective alternative to traditional sprinkle irrigation.En litteraturstudie samt ett fältförsök har genomförts för att studera markfuktens inflytande på kvalitet och kvantitet hos Solanum tuberosum. Litteraturstudien visar att hög och jämn markfukt vid odling av potatis ger högre skörd, fler antal knölar och bättre kvalitet. Ett praktiskt odlingsförsök genomfördes för att undersöka om teorin överenstämmer med praktiken. I försöket testades droppbevattning som ett alternativ till konventionell spridarbevattning i ett enkelt blockförsök. Markfukten i det droppbevattnade ledet styrdes utifrån avdustningen och reglerades så att den höll sig inom det rekomenderade intervallet. Det spridarbevattnade ledet vattnades på traditionsenligt vis med ca 35 mm var 7-10 dag beroende på väderlek. Resultaten från försöket styrkte teorin, en hög och jämn markfukt gav i medeltal 11 % högre skörd och den säljbara fraktionen, dvs. storleken mellan 38 och 55mm, blev 20 % högre. Största ökningen blev det i fraktionen 38-45 mm där det droppbevattnade ledet gav 36 % mer skörd än det spridarbevattnade. I medeltal gav det droppbevattnade ledet 62 % mindre potatis i fraktionen större än 55 mm. Andelen foder i det droppbevattnade ledet minskade så att den totala säljbara varan ökade med i genomsnitt 28 % i jämförelse med det spridarbevattnade ledet. Slutsatsen från denna studie är att droppbevattning kan användas som ett kostnadseffektivt alternativ till spridarbevattning

Method for in-field texture analysis of sugar beet roots using a handheld penetrometer

Methodology for analysing textural properties of sugar beet roots in the laboratory has previously been established. It has been shown to be reliable and of value in exploring relationships between textural properties, damage rates, and storability of varieties. In this paper, a methodology for the assessment of textural properties in-field, prior to harvest, using an inexpensive handheld penetrometer is examined. Three sugar beet varieties were grown in Belgium, the Netherlands, and Sweden during 2019. Textural properties were assessed in-field with the handheld penetrometer 2, 1 and 0 months prior to harvest, and with the laboratory penetrometer directly after harvest. Comparison of the results showed generally strong correlations. A power analysis suggests a difference in mean Handheld Pressure of 0.10 MPa could be found significant within a large trial with a block design. The reliability of the handheld penetrometer was further assessed in the Swedish national variety trials over three years (2019-2021). Correlation coefficients of 0.86 and 0.94 were found between mean Handheld Pressure for 2019 and 2020, and 2020 and 2021 respectively. The handheld penetrometer can be applied as an economic means of quantifying differences in textural properties of sugar beet varieties. Clear operating procedure and training must exist