Articles containing the keyword 'N fertilization'

A total of 1,800 3-year old seedlings of Norway spruce (Picea abies (L.) H. Karst.) from two Norwegian and one German provenance were treated with two different nitrogen levels during the 1992 growth season. The plants were kept during the following winter at two different temperature levels. In the spring of 1993, the nutrient application was resumed, and the plants were divided between three different treatments, 350 and 650 p.p.m. in open top chamber and a control plot outside the chambers. This treatment was repeated also during the following 1994 growth season.

The growth and primary production were studied by photosynthesis experiments and by non-destructive growth measurements. The result indicate that raised winter temperature may lead to increased needle loss and reduced growth the following season, particularly in northern provenances. Carbon dioxide significantly influenced growth in addition to nutrient level and winter temperature. High CO2 also seemed to cause increased photosynthesis at early season, and earlier budbreak and growth cessation than in control plants.

• Skre, E-mail: os@mm.unknown
• Nes, E-mail: kn@mm.unknown

Forest ecosystems may accumulate large amounts of nitrogen in the biomass and in the soil organic matter. However, there is increasing concern that deposition of inorganic nitrogen compounds from the atmosphere will lead to nitrogen saturation; excess nitrogen input does not increase production. The aim of this study was to determine the long-term changes caused by nitrogen input on accumulation of nitrogen in forest soils and in ground vegetation.

The fertilization experiments used in this study were established during 1958–1962. They were situated on 36- to 63-year-old Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) stands of different levels of fertility. The experiments received nitrogen fertilization 5–7 times over a 30-year period, and the total input of nitrogen was 596–926 kg/ha.

Nitrogen input increased the amount of organic matter in the humus layer and the nitrogen concentration in the organic matter. Furthermore, the total amount of nutrients (N, P, K, Ca and Mg) bound by the humus layer increased due to the increase in the amount of organic matter. However, nitrogen input decreased the biomass of ground vegetation. The nitrogen concentration of the plant material on the nitrogen-fertilized plots was higher than on the control plots, but the amount of nutrients bound by ground vegetation decreased owing to the drastic decrease in the biomass of mosses. Ground vegetation does not have the potential to accumulate nitrogen, because vegetation is dominated by slow-growing mosses and dwarf shrubs which do not benefit from nitrogen input.

• Mäkipää, E-mail: rm@mm.unknown

In a greenhouse experiment that lasted for two years, nitrogenase activity, height growth and biomass production was compared in six clones of alder of which four were clones of Alnus incana and two A. incana x A. glutinos hybrids. In addition, the effect of a fertilizer nitrogen gradient was tested on one of the clones.

Clonal differences in height growth and nitrogenase activity were recorded at the end of the first growing season. The growth rhythm of some of the clones changed markedly during the second growing season but differences in nitrogenase activity between clones levelled out. Nitrogen fertilization suppressed nodulation during the first growing season, and also the following year the nitrogenase activity was significantly higher in alders grown without nitrogen supplement. Height growth and total biomass production was also depressed at rather low nitrogen levels.

The PDF includes a summary in Finnish.

• Palmgren, E-mail: kp@mm.unknown
• Saarsalmi, E-mail: as@mm.unknown
• Weber, E-mail: aw@mm.unknown

A method for calculation of the effect of practical fertilization for economic evaluation is presented and discussed. 55 Norway spruce (Picea abies (L.) H. Karst.) dominated stands on Oxalis-Myrtillus type sites were surveyed five to eight years after fertilization with nitrogen (90-170 kg/ha). The relationships between the fertilization effect and various stand characteristics were discussed. Fertilization increased the growth of the stands on an average by 2.2 m³/ha/year. In total the increase of tree growth during the research period was 17.5 m3/ha. This corresponds to a yield of 525–659 FIM/ha.

The PDF includes a summary in English.

• Westman, E-mail: cw@mm.unknown
• Leikola, E-mail: ml@mm.unknown
• Nummi, E-mail: tn@mm.unknown

The effect of nitrogen fertilization and two insecticides on the occurrence of the plant pine bark bug, Aradus cinnamomeus Panzer, was investigated in a young Scots pine (Pinus sylvestris L.) stand in Southern Finland. Three years after the treatment the bug density was lowest in the trees treated with lindane or dimethoate. However, in spite of the increasing height growth of the trees, they did not grow significantly faster than the control trees. Nitrogen fertilization increased both bug density and the height growth of the trees. Thus, the value of nitrogen fertilization against Aradus cinnamomeus remains obscure.

The PDF includes a summary in Finnish.

• Heliövaara, E-mail: kh@mm.unknown
• Annila, E-mail: ea@mm.unknown
• Terho, E-mail: et@mm.unknown

Application of nitrogen at levels of 200, 400 and 600 kg ha^-1 resulted in increases of 35, 18 and 12% in the photosynthetic rate in young Scots pine (Pinus sylvestris L.). The number of buds, degree of branching, and needle size were positively related to the amount of nitrogen applied. A 10–40% increase in the average needle area was found. A positive correlation was found between total photosynthesis and stem growth.

The PDF includes a summary in Finnish.

• Kellomäki, E-mail: sk@mm.unknown
• Puttonen, E-mail: pp@mm.unknown
• Tamminen, E-mail: ht@mm.unknown
• Westman, E-mail: cw@mm.unknown

The effect of nitrogen fertilizers on the photosynthetic capacity of conifers is assessed on the basis of literature. The review emphasizes the role of changes of needle mass as a factor affecting the result of nutrient application. In particular, the increase in needle mass results in a considerable increase in photosynthetic capacity. The effect of fertilization on the photosynthetic rate seems to be of minor importance. The effect on the photosynthetic rate is, however, poorly documented as is the case for the effect of fertilization on the respiration rate. There is evidence that proper application of nitrogen fertilizers may double the photosynthetic capacity of conifers, mainly as a result of increase in needle mass.

The PDF includes a summary in English.

• Kellomäki, E-mail: sk@mm.unknown

The paper describes a preliminary attempt to assess the long-term effect of urea application on the quantity of nitrogen available for plants in forest soil. The soil samples required for the study were collected from an experimental area which had been set up for investigations into both the single and joint effect on tree growth of two levels of each of urea and phosphorus application. The stand was a mixed forest of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) H. Karst.) on Myrtillus type site with an average volume of 217.5 m³/ha.

According to the results, the nitrogen available for plants of the humus layer was significantly higher in fertilized than in unfertilized plots as late as four years after application. In terms of absolute values, the quantities were extremely small, only 3–4% of the amounts applied. In comparison with these results it was interesting to notice that urea application seemed to increase the C/N ratio.

The PDF includes a summary in English.

• Westman, E-mail: cw@mm.unknown

Soil respiration readings are reported for three ameliorated peatland sites of different types, covering a period of four years, during which the sites were drained and treated with various fertilizers. Respiration is shown to increase exponentially with temperature, varying mostly in the range 100–500 mg CO² m^-2 h^-1. The changes in soil respiration followed those in surface temperature with a time-lag of approximately 3–3.5 hours. At one site, where the groundwater table dropped by about 0.5 m after ditching, soil respiration increased 2.5-fold within a few weeks, whereas at the other two sites both the fall in the groundwater table and the resultant changes in soil respiration were small.

The fertilizers tested were slow-dissolving PK, fast-dissolving PK, wood ash, slow-dissolving PK + urea, slow-dissolving PK + Nitroform (urea formaldehyde) and slow-dissolving PK + urea + a micro-element mixture. Application of fast-dissolving PK + urea led to a rapid increase in soil respiration at the site poorest in nutrients, and slow-dissolving PK to a slow increase in respiration. The greatest, steady increase of all was achieved by treatment with ash. At the sites with a higher natural nutrient content the application of fertilizers usually led to a decline in soil respiration lasting 1–2 years, after which the initial level was normally regained. Treatment with micro-elements caused an initial fall in soil respiration values in all three biotopes, followed by a pronounced increase.

The PDF includes a summary in Finnish.

• Silvola, E-mail: js@mm.unknown
• Välijoki, E-mail: jv@mm.unknown
• Aaltonen, E-mail: ha@mm.unknown

• Luoranen, Finnish Forest Research Institute, Suonenjoki Research Unit, Juntintie 154, FI-77600, Suonenjoki, Finland E-mail: jaana.luoranen@metla.fi
• Rikala, Finnish Forest Research Institute, Suonenjoki Research Unit, Juntintie 154, FI-77600, Suonenjoki, Finland E-mail: rr@nn.fi

• Jacobson, The Forestry Research Institute of Sweden, Uppsala Science Park, SE-75183 Uppsala, Sweden E-mail: staffan.jacobson@skogforsk.se