The nutrient status of the soils in Shenchong Basin and the effects of soil erosion were examined during the summer of 1987. Eight raingauges and two thermographs provided meteorological data. Soil samples were collected from different land use categories in the uplands and lowlands, including agricultural areas. Water and sediment samples were collected from 1) surface discharge from the upland slope, rills and a gully during storms and 2) surface and ground waters during dry weather. Analysis was carried out on water samples to determine ammonia-nitrogen, nitrate-nitrogen, orthophosphate, soluble iron, calcium and potassium concentrations. The soil and sediment samples were analyzed for nitrate-nitrogen, available phosphorus, exchangeable potassium, calcium, magnesium and iron. Concentrations of nitrate and orthophosphate in the water samples were very low. Potassium showed the highest concentrations. Ammonia was the dominant inorganic nitrogen species in water and possibly the soils. The soils were highly acidic (pH < 5) and the soluble iron concentrations were high in the upland soils. Total aluminum concentrations were also high. Potassium concentrations were high in soils from vegetated areas. The higher levels of calcium and magnesium in the agricultural soils were were related to lime additions. Available phosphorus concentrations were very low. Nitrate showed no spatial trend except for the high concentration in the cassava field which was attributed to the peanut plants that were previously planted there. In general, nutrient concentrations were low compared to other tropical areas in the world. / Thesis / Master of Science (MSc)

The research objectives were to examine the effect of soil nutrient status on the growth rate, reproductive development, yield components and yield of maize in a long-term trial. On the Experimental Farm of the University of Pretoria, treatments selected for this investigation were O (control), PK (nitrogen deficient), NK (phosphorus deficient), NP (potassium deficient), NPK (balanced nutrient), and WNPKM (mixture of balanced nutrient and manure). Growth analyses were performed, embryonic tassel and ear development recorded, developmental stages and rate of tasseling and silking were monitored while yield components were determined at maturity. The balanced nutrient treatment (WNPKM) plants showed the highest growth rate and produced the highest biomass while the P and K deficient treatments resulted in low growth rates and low biomass. The PK and NPK treatments were intermediate in terms of growth rate and biomass production. The WNPKM, NPK and PK treatments exhibited a high net assimilation rate (NAR) and crop growth rate (CGR), illustrating that an adequate supply of N, P and K is required for high growth rate and biomass production. Plants in the WNPKM plots exhibited early tassel initiation and ear differentiation and larger reproductive organs. Reproductive development in the PK treatment was ahead of those of the NP and NPK treatments. Nutrient stress delayed initiation and differentiation resulting in smaller reproductive organs. A linear relationship was found between leaf area indices (LAI) and the sizes of the reproductive structures. The higher the LAI the larger the size of the reproductive structures. Emergence of inflorescences was timely in plants exposed to the balanced nutrient but delayed in nutrient deficient treatments. Grain yield and the yield components were positively affected by the balanced nutrient treatment while the nutrient stress treatments reduced the yield. Copyright 2008, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. Please cite as follows: Bello, ZA 2008, Effect of soil nutrient status on growth, reproductive development and yield components of maize in a long term field trial, MSc(Agric) dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-02122009-105701 / > E1251/gm / Dissertation (MSc(Agric))--University of Pretoria, 2008. / Plant Production and Soil Science / unrestricted

Fruit tree leaf nutrient concentrations are commonly used to determine fertilizer rates, but information is limited regarding nutrient requirements, seasonal N uptake and removal rates, and soil N dynamics for pomegranate. Relationships between fertilizer rates, leaf nutrient concentrations, fruit yield and quality were examined in five mature, commercial California ‘Wonderful’ pomegranate orchards. Site 1 was observed for two growing seasons (2018-2019) and sites 2-5 were observed for one season (2018 or 2019). In 2018, 150, 300, or 450 g N/tree was applied at sites 1-3 in a single application at early fruit development or in two equal applications at early and mid-season fruit development. In 2019, fertilizer rates were adjusted based on site-specific leaf nutrient analysis and crop load and applied at mid-season fruit development (158, 185, 225, 286, 392, or 625 g N/tree at site 1; 115, 130, 150, 175, 212, or 270 g N/tree at site 4; and 107, 122, 142, 171, 214, or 286 g N/tree at site 5). A randomized complete block design was used for all experiments. Leaves were collected from all data trees during early, mid-season and late fruit development and analyzed for leaf nutrient concentrations. At harvest, total fruit weight per tree and individual fruit weight and diameter were measured. Canopy volume was measured during the dormant season prior to pruning. Nitrogen partitioning, uptake and removal rates were studied by analyzing plant tissue, soil, and lysimeter water samples in 2019 at site 5. Fruit yield and average diameter varied significantly depending on site and fertilizer treatments. Average fruit yield per tree ranged from 5-90 kg fruit/tree (site 1: 78.5 kg fruit/tree in 2018 and 91.1 kg fruit/tree in 2019, site 2: 55.6 kg fruit/tree, site 3: 29.7 kg fruit/tree, site 4: 5.6 kg fruit/tree, site 5: 9.1 kg fruit/tree). Sufficiency ranges and significant relationships were determined between certain nutrients, including nitrogen and potassium, to fruit yield and diameter. Higher fertilizer treatments were associated with higher residual soil N compared to the low fertilizer treatments within the root zone (2.25-19.33 mg/L NO3-N) and below the root zone (2.25-9.17 mg/L NO3-N) suggesting a higher likeliness of nitrogen leaching with fertilizer applications exceeding the crop’s nitrogen demand. Overall, variability between sites in fertilizer treatment effects, leaf nitrogen concentrations, and yield suggests that setting site-specific yield goals based on estimated N uptake and removal is necessary to develop effective pomegranate fertilizer programs.

5 pp. / Soil testing is comprised of four steps: Collection of a representative soil sample, laboratory analyses of the soil sample, interpretation of analytical results, and management recommendations based on interpreted analytical results.

Revised; Originally Published: 2006 / 5 pp.

Nutrient concentrations in plant tissues are directly correlated with the nutritional status and productivity of fruit trees. Plant tissue testing is one of the most effective and accurate methods to determine nutritional status of perennial plants. Tissue test analyses were performed on tart cherry (Prunus cerasus) and peach (Prunus persica) leaves to validate tissue sufficiency levels used in Utah and to determine optimal timing of tissue sampling for prediction of harvest nutrient status, focusing on phosphorus (P), potassium (K), calcium (Ca), iron (Fe), and zinc (Zn). Sufficiency limits that were adopted in Utah were developed in the 1960s from research data accumulated from the primary fruit growing regions in the United States. Limited research has been conducted under Utah growing conditions. Tissue nutrient concentrations over time correlated well with current sufficiency limits and observed nutrient deficiencies in the field. Tissue concentrations of P, K, Fe, and Zn were found to be chronically low in Utah orchards. Plant tissue data demonstrates that mid-season sampling can predict nutrient status at harvest. Mid-season sampling also allows time for corrective adjustments to maintain sufficiency levels and reach optimal fruit production. Nutrient management practices are commonly applied annually to increase yield, fruit quality, and overall health of an orchard. Yield was measured on previously treated tart cherry orchards to determine residual effect on tree nutrient status. Orchards were treated 2 to 3 years prior with rate-response formulations of P and K; one has since adopted recommended fertilizer rates for optimizing tart cherry production in Utah and the other continued with their less aggressive management practices. The less aggressively managed orchard showed trends across treatments, but differences were not significant. Annual fertilizer applications may not immediately show effect during year of application, but long term management is essential for overall productivity of orchards.

Agricultural land releases large amounts of nitrogen and phosphorus to water bodies which causes eutrophication. Creating wetlands on agricultural land is one way to prevent this major issue. However, constructed wetlands are a large emission source of greenhouse gases. The aim of this study was to quantify the CH4 and N2O emissions in 21 constructed wetlands (CWs) around Mälardalen located in mid-Sweden and 19 CWs in the county of Halland along the south-west coast of Sweden and examine if there was any relation between the emissions and the nutrient status. Furthermore, the emission contributed by CH4 ebullition was evaluated. Synoptic water and gas sampling was done during early and late autumn. Floating chambers were deployed in six wetlands and measured CH4 ebullition over a 24-hour period. The diffusive CH4 emissions varied between 0.10–103 mg m-2 d-1 with a mean value of 13 mg m-2 d-1. The N2O emission varied between -0.086–7.8 mg m-2 d-1 with a mean of 1.4 mg m-2 d-1. Significant negative correlation between N2O emission and C:N ratio and a significant positive correlation between N2O emission and N:P ratio was found. No relation between the CH4 emission and total organic carbon (TOC) was found which other studies have been able to prove. Only a weak relation between the CH4 emission and the C:N ratio was found. The ebullition in the six wetlands varied between 0–62 mg m-2 d-1 and accounted for more than 85% of the total CH4 emission in most of the chambers. No significant difference in ebullition was found within the CWs but between the CWs there were found significant differences. The conclusion of this thesis is that CWs in agricultural areas represent a large source of CH4 and N2O emissions and that nutrient status has a major influence of the N2O emissions. Lastly, ebullition seems to be a major pathway for the CH4 emission. / Jordbruksmark släpper ut stora mängder kväve och fosfor till ytvatten vilket orsakarövergödning. Skapandet av våtmarker på jordbruksmark är ett sätt att förhindra detta problem.Dock är anlagda våtmarker stora utsläppskällor av växthusgaser. Målet för den här studien varatt kvantifiera utsläppen av CH4 och N2O från 21 anlagda våtmarker runt Mälardalen beläget imitten av Sverige och 19 anlagda våtmarker i Hallands län längs Sveriges sydvästra kust.Vidare var syftet att undersöka om det fanns någon relation mellan utsläppen ochnäringsstatusen. Fortsättningsvis, utsläppen av CH4 genom ebullition utvärderades. Synoptiskvatten- och gasprovtagning utfördes under tidig höst och senhöst. Flytande kamrar sattes ut isex våtmarker och mätte CH4 ebullition under en 24-timmars period. Utsläppen av CH4genom diffusion varierade mellan 0.10–103 mg m-2 d-1 med ett medelvärde på 13 mg m-2 d-1.Utsläppen av N2O varierade mellan -0.086–7.8 mg m-2 d-1 med ett medelvärde på 1.4 mg m-2d-1. Signifikant negativ korrelation mellan utsläpp av N2O och C:N-kvoten och en signifikantpositiv korrelation mellan utsläpp av N2O och N:P-kvoten hittades. Ingen relation mellanutsläppen av CH4 och totalt organiskt kol hittades vilket andra studier kunnat påvisa. Endasten svag relation mellan utsläppen av CH4 och C:N-kvoten hittades. Ebullitionen i de sexvåtmarkerna varierade mellan 0–62 mg m-2 d-1 och stod för mer än 85 % av det totala CH4utsläppen i de flesta kamrarna. Inga signifikanta skillnader i ebullition kunde hittas inom deanlagda våtmarkerna men dock mellan våtmarkerna. Slutsatsen av den här studien är attanlagda våtmarker på jordbruksmark representerar en stor källa av CH4 och N2O utsläpp ochatt näringsstatusen i anlagda våtmarker har en stor inverkan på utsläppen av N2O. Slutligen,ebullitionen verkar vara en betydande utsläppsväg för CH4.

<p>Temporal and spatial variations of pelagic microorganisms in the northern Baltic Sea were studied, as well as factors influencing their abundance and growth rates. Three main questions were asked 1) How does increased productivity influence the structure of the microbial food web? 2) Does predation limitation vary between trophic levels? 3) What is the relative importance of resource and predation limitation at different trophic levels?</p><p>A field study in the northern Baltic Sea showed that dominating protozoa, flagellates and ciliates, increased with increasing primary productivity from north to south. Furthermore, relatively small protozoan cells dominated in the low productive north, while larger cells became more dominant in the south. The relationship between plankton size structure and productivity was further studied in an experimental system. In agreement with present theories regarding nutrient status of pelagic food webs, increased productivity caused a lengthening of the food chain as well as a change in plankton size structure. While microplankton dominated in nutrient rich treatments pico- and nanoplankton dominated during nutrient poor treament. The flagellate community was dominated by a potentially mixotroph, <i>Chrysochromulina</i> sp., at low nutrient concentrations. To our knowledge this is the first experimental study showing that <i>Chrysochromulina</i> sp. in resemblance with other mixotrophs is favoured by nutrient poor conditions compared to strict autotrophs and heterotrophs.</p><p>During a stratified summer period autotrophic microorganisms in the northern Baltic Sea did not respond to removal of potential predators, indicating that they were primarily limited by inorganic nutrients. An exception was small eucaryotic picoplankton that showed a large response to predator removal. Among the heterotrophic microorganisms direct effect of predation seemed to increase from ciliates, heterotrophic bacteria, small heterotrophic flagellates, medium flagellates to large flagellates. No quick indirect effect was observed, but after four days trophic cascades were detected.</p><p>The relative importance of resource and predation limitation was studied among heterotrophic bacteria, flagellates and ciliates in the northern Baltic Sea. For all these groups, resource limitation seemed to prevail during the summer period. The results also indicated that the relative importance of predation increased with the productivity of the system. To our knowledge there are no earlier measurements on the relative importance of resource and predation limitation for micoorganisms in the pelagic environment.</p>

Temporal and spatial variations of pelagic microorganisms in the northern Baltic Sea were studied, as well as factors influencing their abundance and growth rates. Three main questions were asked 1) How does increased productivity influence the structure of the microbial food web? 2) Does predation limitation vary between trophic levels? 3) What is the relative importance of resource and predation limitation at different trophic levels? A field study in the northern Baltic Sea showed that dominating protozoa, flagellates and ciliates, increased with increasing primary productivity from north to south. Furthermore, relatively small protozoan cells dominated in the low productive north, while larger cells became more dominant in the south. The relationship between plankton size structure and productivity was further studied in an experimental system. In agreement with present theories regarding nutrient status of pelagic food webs, increased productivity caused a lengthening of the food chain as well as a change in plankton size structure. While microplankton dominated in nutrient rich treatments pico- and nanoplankton dominated during nutrient poor treament. The flagellate community was dominated by a potentially mixotroph, Chrysochromulina sp., at low nutrient concentrations. To our knowledge this is the first experimental study showing that Chrysochromulina sp. in resemblance with other mixotrophs is favoured by nutrient poor conditions compared to strict autotrophs and heterotrophs. During a stratified summer period autotrophic microorganisms in the northern Baltic Sea did not respond to removal of potential predators, indicating that they were primarily limited by inorganic nutrients. An exception was small eucaryotic picoplankton that showed a large response to predator removal. Among the heterotrophic microorganisms direct effect of predation seemed to increase from ciliates, heterotrophic bacteria, small heterotrophic flagellates, medium flagellates to large flagellates. No quick indirect effect was observed, but after four days trophic cascades were detected. The relative importance of resource and predation limitation was studied among heterotrophic bacteria, flagellates and ciliates in the northern Baltic Sea. For all these groups, resource limitation seemed to prevail during the summer period. The results also indicated that the relative importance of predation increased with the productivity of the system. To our knowledge there are no earlier measurements on the relative importance of resource and predation limitation for micoorganisms in the pelagic environment.

Altitudinal gradients offer attractive opportunities for studies of population differentiation in response to environmental heterogeneity. In this thesis, I examined population differentiation along altitudinal gradients by combining common-garden experiments with field studies and experiments in alpine, subalpine and boreal populations of the perennial herb Solidago virgaurea. More specifically, I determined whether leaf physiology in terms of nitrogen concentration and resorption, flowering phenology, flower production and reproductive effort vary along altitudinal gradients. Nitrogen concentration in green leaves were higher in alpine than in subalpine and boreal populations. These differences persisted when plants were grown from seeds in a common-garden experiment at two sites, suggesting that the differences have a genetic component. There was mixed support for a trade-off between maximized carbon gain through the maintenance of high nitrogen concentration, and minimized nitrogen loss through high resorption. In their natural habitats alpine populations began flowering later than subalpine populations, but this difference was reversed when plants were grown in a common environment. This suggests that genetic differences among populations counteract environmental effects and reduce phenotypic variation in flowering time among populations. Flowering time thus shows countergradient genetic variation in S. virgaurea. In a common-garden experiment, boreal populations produced more flowers and had a higher reproductive effort than subalpine and alpine populations indicating habitat-specific genetic differences in reproductive allocation. In a field study, which included three populations, seed set was close to zero in the alpine population, intermediate in the subalpine population, and high in the boreal population. Experimental flower removal showed that seed production was associated with a considerable cost in terms of reduced flowering propensity the following year, but did not support the hypothesis that a large floral display is important for pollination success.