Lennart Mattsson

Swedish Soil Fertility Experiments

Twelve long-term soil fertility field experiments in south, central and north Sweden were started in the period 1957-1969. Five of the experiments, two in south and three in central Sweden, were situated at favourable sites, the other seven were placed at sites with less favourable climatic conditions and natural soil properties. Two crop rotations, one with and one without livestock and 16 combinations of inorganic NPK (nitrogen phosphorus potassium) fertilizers were compared in the south and central Swedish experiments. In north Sweden, there was one rotation with livestock and 30 NPK combinations. There was a four-course rotation in the south, a six-course in central Sweden and a seven-course rotation in north Sweden. The ordinary fertilizer treatments in the rotations without livestock almost doubled the yields of cereals compared with the unfertilized plots; with more fertilizer yields were even larger. In the livestock rotations the mineral fertilizer effects were smaller owing to positive effects of the manure. N responses were always considerably greater than PK responses. In north Sweden yield responses were of the same magnitude as in south and central Sweden. With no fertilizers, in the livestock rotations the uptakes of N, P and K were 50-90, 10-15 and 30-100 kg ha -1 , respectively, depending on the crop. In the non-livestock rotations corresponding values were 25-40, 7-10 and 10-25 kg. In north Sweden the N removal was even higher owing to the large proportion of ley in the rotation. In zero N treatments in south Sweden, over a 24 year period, losses of organic matter were nearly 10 t ha -1 in the non-livestock rotation and about half as much in the livestock rotation. With 100 kg N ha -1 losses were negligible. Levels of AL-extractable P were not maintained where P additions equalled offtakes in the crops, but decreased by about 1 unit during the period. P dynamics differed between sites; on some, P fertilizer had no effect on either yields or soil P, whereas in other cases P fertilization increased yields and kept soil P in plant-available forms. The cadmium content in sugar beet roots increased with increased NPK fertilization, but the increases were smaller than differences between sites. The cadmium content varied from 128 to 288 ppb.

Application of the PROFILE model to estimate potassium release from mineral weathering in Northern European agricultural soils

Negative potassium (K) balances have been reported from grass-dominated organic systems in several European countries, and in these systems delivery of K from soil primary minerals by weathering is probably crucial to sustained productivity. Mass balances and K budgets have been made at eight grass-dominated experimental agricultural systems, one each in Scotland and Sweden and six in Norway. Where no fertiliser K was applied, the deficits obtained were in the range 35–241 kg K ha−1 per year. An estimate of the weathering rate was determined by the biogeochemical PROFILE model that varied widely between locations (3–82 kg K ha−1 per year). This paper is a first attempt to apply the steady-state PROFILE model on agricultural soils by using data from experimental sites. The Monte Carlo simulation of the weathering rate calculation showed that differences in specific surface area and soil water content strongly influenced the predicted weathering rate, which was associated with a degree of uncertainty. All sites showed a negative annual K-balance, which means that the specific contribution that mineral weathering makes to the long-term replenishment of soil exchangeable-K is important but may not be sufficient to counteract large K removal associated with high crop yields. Despite the uncertainties in the weathering rate calculation, these preliminary results are still useful in several aspects because the simulations make it possible to compare different agroecosystems with different management regimes, climate, soil properties, etc. The simulations also indicate which environmental factors are likely to be the most influential on weathering rates. Soil physical properties, such as moisture content, bulk density and surface area, appeared to be amongst the most important input parameters controlling actual weathering rates within groups of soils having similar mineralogical and chemical compositions. There is now a need for improved laboratory experimental data that better describe the kinetics of mineral weathering in order to enhance the accuracy and precision of PROFILE.

Properties and classification of soils of the Swedish long-term fertility experiments: V. Sites at Vreta Kloster and Högåsa

The overall objective of this study was to discover the most limiting soil properties for crop production at two fertility sites. The Vreta Kloster soil, classified as a very fine, mixed, semiactive Oxyaquic Haplocryoll, according to the Soil Taxonomy and as a Haplic Phaeozem according to the World Reference Base for Soil Resources (WRB), consisted of very dark greyish brown silty clay overlying a subsoil of heavy clay (70–80%). Porosity increased with depth due to a greater micro- but not macro-pore volume. Stocks of C and N amounted to 76.4 t C ha−1 and 8.7 t N ha−1 in the Ap-horizon and 24.8 t C ha−1 and 3.25 t N ha−1 in the subsoil to 1 m depth. Soil pH increased with depth, 6.6 to 7.4, and CEC values ranged 25 to 31 cmolc kg−1 soil. The main clay minerals were illite/mica (45%) followed by vermiculite (9–20%). Chlorite and kaolinite amounted to 2% throughout the profile. In dry years, crop production at the Vreta Kloster site was greatly reduced, which can be attributed to the absence of macro-pores and high portion of micro-pores and in the subsoil reducing the amount of water available to crops. The Högåsa profile, classified as a sandy mixed Humic Dystrocryept according to the Soil Taxonomy and as Arenic Umbrisol according WRB, consisted of loamy very fine and fine sand. Soil pH and bulk density increased with depth from 5.7 to 6.5 and 1.3 to 1.6 kg dm−3, respectively. Carbon and N stocks amounted to 72.3 t C ha−1 and 5.9 t N ha−1 in the Ap-horizon and were low in the subsoil, 13.5 t C ha−1 and 1.1 t N ha−1. Clay mineralogy was dominated by illite/mica (26–50%) with vermiculite being formed in the Ap-horizon. Chlorite amounted to 3–6% and kaolinite to 2–3% in the profile. Crop yields were less affected by rainfall conditions and leys were more productive at Högåsa than Vreta Kloster. A high mechanical resistance reducing root penetration of the subsoil and a low nutrient content limited crop production at Högåsa.

Management effects on topsoil carbon and nitrogen in Swedish long-term field experiments¿budget calculations with and without humus pool dynamics

The annual input and output of nitrogen (N) to and from agricultural land is relatively small compared with the total stock of organic N in soil. However, the long-term humus N pool dynamics is seldom considered in fertilisation planning, and thus N surpluses in budgets are considered as losses. In this paper, we analyse the consequences of this assumption and investigate how observed data precision affect the precision of model projections. We used available data sets from long-term agricultural field experiments in Sweden (topsoil C and N concentrations, crop yields as well as soil type and climate data) for calculating topsoil C and N mass dynamics. ICBM/2N, a simple C and N soil model (available at: www.mv.slu.se/vaxtnaring/olle/ICBM.html), was used for calculating soil organic matter balances. We parameterised this model for two field trials, and for specific crops, using available data and educated guesses and compared the results with those obtained from the conventional approach, not including humus pool C and N dynamics. In spite of the corrections for bulk densities, etc., the soil carbon measurements were too variable for a critical model validation or a sensitive test of the effects of including pool dynamics. In other words, we had to rely on the model assumptions for the projections and soil data could only be used to obtain general means, e.g., for the whole duration of the experiment. We think this is a general problem, not limited to this data set and model. We also show, at least in principle, how estimates of organic N pool dynamics can be used to produce improved N balance sheets for individual crops. For example, the apparent N use efficiency by sugar beet increased from 58 to 99% when organic N pool dynamics were included.

Occurrence of Glomeromycota spores and some arbuscular mycorrhiza fungal species in arable fields in Sweden

Fungi within the phylum Glomeromycota were investigated in arable fields throughout Sweden. Sweden is located between 55° and 69° North. The fungi within this phylum form arbuscular mycorrhizal symbiosis with plant roots. Sampling of soil was carried out to a depth of 30 cm in the rhizosphere. Arbuscular mycorrhizal fungi were found at all 45 sampling sites, at densities between 3 and 44 spores per g dry weight of soil. No significant differences in spore densities were found between different agro-climatic zones or between semi-natural grassland and ploughed fields. Our study revealed that the upper half (0–15 cm) of the soil profiles had significantly more spores than the lower half (15–30 cm). Spores from eight sampling sites were identified from the indigenous soils. Almost 90% were shown to belong to the genus Glomus. The other genera found were Gigaspora and Scutellospora.

Transport of phosphorus forms and of nitrate through a clay soil under grass and cereal production

Many nutrients are lost from soil to water viatile drains. However, there are very few reliable studies of such phosphorus(P)losses under Swedish agriculture practices, especially in connection tofertiliser and slurry applications and related to nutrient balances. Tile drainlosses were measured from nine experimental plots in south-west Sweden; fourplots were measured for 7 years and five plots for 2–3 years. Cereals,mainly spring barley (Hordeum vulgare, L.) and oats(Avena sativa, L.), were grown in six plots, while oneplotwas cultivated with grass, timothy (Phleum pratense L.)andmeadow fescue (Festuca pratensis, L.), one with lucerne(Medicago sativa, L.) and meadow fescue (F.pratensis, L.), and the last one was a “set-aside” withgrass (Lolium perenne, L. and Trifoliumrepens, L.) that was neither fertilised nor used for crop removal.Attention was paid to the forms in which P was transported to water since thishas important ecological implications. Average losses of particulate P (PP)fromthe “set-aside land” was significantly lower than from the cerealproduction, but the average losses of soluble reactive P (SRP) and dissolvednonreactive P (DUP) were the same. Average loss of PP from the grass ley during 3years (0.09 kg per ha−1 y−1) wassignificantly less than the losses from cereal production. Total P loss of 0.3kg per ha−1 y−1 was equal to the averagelossfrom the Swedish monitoring network of observation fields. Compared to theaverage nitrate-nitrogen (NO3-N) leaching, which was 7 kg perha−1 y−1 from cereals, the NO3-Nleaching was very low from the plots with lucerne-grass and “set-aside”.After applying and directly ploughing in 80 kg ha−1 ofsuperphosphate for cereal production in November 1998, 0.6–1.8 kgSRP ha−1 y−1 was lost through the drain tiles.Surface application of cattle slurry in spring 1999 to the grass ley alsoresulted in a very pronounced increased base level of SRP. This paper documentsthe importance of applying slurry during dry conditions and of placingfertiliser into the soil according to crop requirements in the time perspectiveof one year.

Compatibility of the ammonium lactate (AL) and sodium bicarbonate (Olsen) methods for determining available phosphorus in Swedish soils

Abstract Plant-available P was first extracted in soils 114 years ago and a number of different analytical methods have since been developed, but for good reasons none of these methods has been adopted as a standard for all soils. With increasing cooperation within research, there is a need to harmonise the interpretation of analytical data for fertiliser recommendations, research, and environmental control. This paper evaluates the compatibility of the Swedish standard ammonium lactate (PAL) method and the widely used Olsons sodium bicarbonate (POls) method in 82 topsoil samples taken from Swedish long-term soil fertility field trials. The PAL-values were usually larger than POls, with a mean PAL/POls quotient of 2.30±1.04 (0.67–6.58). The PAL and POls means and ranges were 126±89 (5–360) and 55.1±33 (3.1–122.8) mg P kg−1 dry soil, respectively. Stepwise multiple linear regression analysis was used to evaluate the relationship between PAL and POls and how this relationship was affected by clay content, pH, and soil organic carbon content (SOC). After statistical transformation, it emerged that the square root of clay content (17.4%±13.82, range 1–54.4) and pH (6.45±0.54, range 5.5–7.7) significantly affected the relationship at partial R 2-values of 2 and 12%, respectively, while ln(SOC) (2.54%±1.21, range 1–6.03) did not, apparently due the narrow range. The regressions of predicted vs. measured values explained 95 and 94% of the variation in PAL and POls, respectively. The mean deviation of predicted compared with measured values was 21.3 and 8.3 mg P kg−1 dry soil for PAL and POls, respectively, corresponding to 20 or 19% of the measured values. We conclude that a data set consisting of PAL-values can be converted into POls-values and vice versa with reasonably high accuracy when accounting for clay content and pH.

Use Efficiency and Leaching of Nutrients in Organic and Conventional Cropping Systems in Sweden

In the past few years, organic farming has been proposed as a possible way of reducing N leaching from agricultural soils and improving the use efficiency of plant nutrients. This is, to a large extent, considered to be attributed to the fact that synthetic fertilisers are not allowed in such systems and the N inputs mainly originate in various types of organic manures. In this overview, results from a number of Swedish field studies are presented in which crop yields, nutrient-use efficiencies and leaching in organic and conventional systems are evaluated. Some studies were conducted in lysimeters and others in large tile-drained field plots. In two lysimeter experiments, leaching of N derived from either poultry manure or red clover (Trifolium pratense L.) green manure were compared with fertiliser N, all labeled with 15-N. In the lysimeters on which poultry manure was applied, 32% of N applied leached during three years, whereas only about 3% leached in ammonium nitrate fertilised lysimeters. In plots on a sandy soil, annual N leaching loads averaged over the whole 6-yr crop rotation reached 39,kg N ha-1 in the organic rotations and 25,kg N ha-1 in the conventional rotation. Phosphorus-leaching loads were overall small in all systems, whereas K leaching was highest in the conventional rotation (i.e., on average, 27,kg ha-1 yr-1). In terms of crop yields, they were reduced by 20–80% in the organic rotations compared to the same crops in the conventional rotations. This was explained in terms of N deficiency, weed competition, and infestation of crop diseases in the organic systems. These results suggest that organic crop production uses agricultural soils less efficiently, with no benefit for water quality.

Swedish long‐term experiments

In 1996 there were 124 individual long‐term experiments in Sweden financed by the Swedish University of Agricultural Sciences to a cost of 648.000 Euro. Of these 39 were plant nutrition and soil fertility experiments distributed between the 54th to the 63rd latitude. At three sites, south, central and north, N mineralization in cropping systems with ley and manure was investigated. Approximately 90 kg N per ha and year was removed by the crops at all three sites. Temperature, cropping history and ley proportions are factors that influenced the N mineralization. In rotations without ley and manure at the central and south sites the N uptake was around 30 kg per ha and year. Soil C content decreased during 35 years in the south but changed insignificantly at the central and north sites, 31 and 28 years respectively. Only minor effects on soil C content were observed by increased biomass production due to N fertilization. The efficient C metabolism of the heterotrophic microflora emphasises the significance and importance of the simultaneous ongoing N mineralization for the N supply of crops and for the environment.

Sulfur flow in a soil-plant system—effects of long-term treatment history and soil properties

The influence of long-term treatment and soil type on sulfur (S) flow patterns within soil and from soil to plant was studied in a pot experiment with Italian rye grass (Lolium multiflorum cv. SW Fredrik) with (+S) or without (-S) added S. Soil samples were taken from two field treatments (farmyard manure (FYM) application or crop residue (CR) incorporation) at four sites with differing soil types within the Swedish long-term fertility experiment series. To follow gross processes, the initial soil sulfate pool was labeled with carrier-free H235SO4. The –S treatment resulted in visual symptoms of S deficiency, reduced biomass production and lower total S uptake by the rye grass. The isotopic measurements revealed that more than two thirds of the plant S was derived from non-labeled soil organic S, even in the + S treatment, and that all organic S pools (physically unprotected/protected and residual organic S) in the soil were involved in the S transformations. The long-term FYM treatment had resulted in higher S cycling rates and a slightly higher resistance to S deficiency than the CR treatment. The influence of soil type on S flow patterns was important, but probably only partly related to the soil S properties.