Plant Nutrition, subject area within the SLU Agricultural Long-Term Experiments

Within the subject area Plant Nutrition, there are 24 active long-term field experiments divided into eight experimental series. The experiments address the effects of liming, long-term soil fertility, changes in soil organic matter, and soil biology. The trials are located at sites ranging from Umeå in the north to Trelleborg in the south, with most situated at one of SLU’s research stations (Röbäcksdalen, Lövsta, Lanna och Lönnstorp). 

Plant and soil samples have been collected and archived since the start of the experiments.

A guide to the trials

Here is a guide with more information about the long-term field experiments in plant nutrition in pdf format.

R3-0020 and R3-0021: Humus balance in different cropping systems

The soil organic matter content develops differently in cropping systems with only cereals compared to cropping systems with long-term leys, in this case, three years of ley after establishment followed by another three years of ley, and so on. In the cereal experiments, the development is compared between treatments where the straw is removed and where it is left in the field. Comparisons in both the cereal and ley experiments are made at different nitrogen levels.

Locations and starting years: Röbäcksdalen 1980, Säby 1970, Lanna 1981, Lönnstorp 1980.

RAM-56 and R3-0130: Soil biological conditions

Soil organic matter experiments RAM56:
The "RAM experiment" at Ultuna was established in 1956. The addition of various types of organic materials at different plant nutrient levels is compared. Effects on soil properties such as carbon and nitrogen dynamics are studied. The experimental plots are enclosed by steel frames, 2×2 m in size, sunk into the ground, with about 10 cm of the frame protruding above the soil surface. All management is done manually. The frames ensure that any edge effects can be disregarded.

R3-0130 Soil biological conditions:
The experiment was established in 1996 at Lanna in Västergötland. The aim is to develop different soil biological conditions through the addition of various types of organic materials. Materials applied include grass hay, animal manure, sewage sludge, and municipal compost.

R3-9001 and R3-2037: Soil fertility experiments

The Swedish soil fertility experiments currently comprise nine trials in series R3-9001 and two trials in series R3-2037. Of the nine trials in R3-9001, four are located in Skåne, one in Västergötland, two in Östergötland, and two in Uppland. The two trials in series R3-2037 were established in 1969 and are located at Röbäcksdalen near Umeå in Västerbotten County and at Offer, between Sollefteå and Kramfors in Västernorrland County.

In R3-9001, a farming system with livestock (where animal manure is applied and leys are included in the crop rotation) is compared with a system without livestock (no manure application and no leys in the rotation).

R3-1002: Permanent liming trial

The experimental design includes a large number of treatments. The main factor is liming, but the handling of crop residues is also included. Liming is applied at three levels: no liming, liming to 70 percent base saturation, and liming to 100 percent base saturation. This is combined with treatments where all crop residues are removed and where all residues are returned. Finally, all treatments are compared at three different NPK levels: low, moderate, and high. The experiments are maintenance-limed every fourth year.

One remaining trial is located at Röbäcksdalen, Umeå, established in 1963.

R3-1001: Lime and phosphorous

The plant availability of soil phosphorus largely depends on the soil chemical conditions. Different forms of phosphorus also react differently. In this experiment, various phosphorus fertilization strategies are examined on soils that have not recieved lime since the 1940s, as well as in soils with various levels of liming.

This experimental series, which includes the two oldest field trials in the country, shows how liming and phosphorus fertilization affect each other. One experiment was established in 1936 and the other in 1941. Both are located at Lanna in Västergötland.