Soil structure, organic matter and earthworm activity in a comparison of cropping systems with contrasting tillage, rotations, fertilizer levels and manure use

Abstract In order to assess long-term effects on productivity, environmental impacts and soil fertility of contrasting farming practices, six cropping systems, ranging from conventional arable without livestock to organic mixed dairy farming with few arable crops, have been compared since 1989 on a loam soil. A decline in soil structure quality was found in a conventional arable system with annual ploughing with no rotational grass. This system had higher bulk density and mean aggregate size than other systems, and lower levels of plant available water and aggregate stability. Opposite trends were related to the proportion of grass leys in the other systems and to their levels of soil organic matter. The latter declined markedly over 15 years in the conventional arable system, and there were smaller declines in most other systems. In an arable system without ploughing, but with rotary tillage in spring, organic matter was maintained and high structural stability was found. This system had high bulk density, but the proportion of small aggregates equalled that found in systems with ley. There were overall increases in earthworm density (84%), earthworm biomass (80%) and the density of earthworm channels (132%) in the topsoil between 1994 and 2004. Most of these increases were found in systems with 1–3 years of ley in the 4-year rotation. Low values of all earthworm parameters, and only minor changes over the period studied, were found in two non-organic arable systems without ley, indicating high pressure on soil fauna. Lower earthworm activity was found in the non-organic arable system with reduced tillage as compared to the non-organic arable system with annual ploughing. Thus, 50% leys in the rotation appeared desirable for the maintenance of satisfactory soil structure and earthworm activity. Though the deterioration of soil structure in the conventional arable system was not extreme, as the soil was well structured initially, the results may have implications for the sustainability of stockless arable systems on soils with a less favourable initial structure

Timeliness and traffic intensity in spring fieldwork in Norway: Importance of soil physical properties, persistence of soil degradation, and consequences for cereal yield

Future increase in precipitation in Scandinavia may exacerbate the dilemma of spring fieldwork that farmers have, concerning topsoil compaction versus delayed sowing on autumn ploughed soil. The former may lead to soil physical degradation, while the latter may lead to a shorter growing season, both with consequential loss of cereal yield potential. In order to enable farmers to adapt their spring fieldwork to climate change, research needs to include seedbed preparation at higher soil moisture conditions. A split-plot experiment in southeastern Norway in 2014–2017 explored the effects of timing (early, medium, late) and traffic intensity (zero, one, two or three additional wheelings) of spring fieldwork on soil physics and yield. Early spring fieldwork in the unfavourably wet conditions of 2016 gave rise to larger and stronger aggregates, higher penetration resistance, changed pore characteristics and reduced yields. Increased penetration resistance persisted until autumn. The small effect of traffic intensity was explained by location, soil type and intensity range involved. In this context of spring fieldwork timeliness, the proportion of 2–6 mm aggregates and penetration resistance were the properties most strongly correlated with other soil physical properties and cereal yield

Hvordan måles innholdet av organisk materiale og karbon i norsk jord?

I Norge brukes oftest glødetap av tørr, siktet jord som mål på innhold av organisk materiale i dyrka jord. I mineraljord med økende innhold av leire, må glødetapet korrigeres ned mer og mer for å finne det virkelige innholdet av organisk materiale i jorda. Både organisk materiale, mold og humus inneholder foruten karbon også flere andre grunnstoffer. Det er vanlig å beregne at organisk materiale i jord i snitt inneholder 50-58 % karbon. Generelt gir glødetapet best mål for innhold av organisk materiale i jordartsklassene mineralblandet moldjord og organisk jord og jordarter med lavt leirinnhold (< 9 %). Det er også der minst forskjell mellom glødetapet og moldinnhold (mer nøye innhold av organisk materiale). I slik jord er også karboninnholdet nærmest 50 % av både glødetapsverdien og verdien for beregnet moldinnhold. I mineraljord med økende innhold av leire, vil glødetapet derimot måtte korrigeres ned mer og mer for best mulig mål for moldinnholdet (det reelle innholdet av organisk materiale) og i etterkant beregning av karboninnholdet. I slik jord blir det større forskjell mellom glødetapsverdien og moldinnholdet i analysene vi bruker. Det blir også viktigere å beregne karboninnholdet mer nøyaktig, og ikke dividere glødetapsverdien, men moldinnholdet med 2. Dette fordi leirinnholdet påvirker glødetapsverdien mye og gir i slik jord et langt lavere reelt innhold av organisk materiale enn glødetapsverdien viser. I lettleire og mellomleire er derfor ofte det reelle karboninnholdet veldig lavt, under 20 % av glødetapstallverdien, og under 1 % karbon av TS

Cul-de-sac

Englis

Animal manure for biogas production - what happens to the soil?

Utilizing animal slurry to produce biogas may reduce fossil fuel usage and emissions of greenhouse gases. However, there is limited information on how the recycling of digested slurry as a fertilizer impacts soil fertility in the long run. This is of concern because organic matter in the slurry is converted to methane, which escapes the on-farm carbon cycle. In 2010, a study of this question was initiated on the organic research farm in Tingvoll, Norway. So far, a biogas plant has been built, producing anaerobically digested slurry to be compared with undigested slurry in perennial ley and arable crops. Effects on crop yields, soil fauna, microbial communities, soil structure, organic matter and nutrient concentrations are measured

SoilEffects - start characterization of the experimental soil

This report describes the establishment, experimental plan and initial soil characteristics of the field experiment linked to the project “Effects of anaerobically digested manure on soil fertility - establishment of a long-term study under Norwegian conditions” (SoilEffects, 2010-14). The aim of the SoilEffects project is to identify potential risks and benefits for soil fertility when animal manure is anaerobically digested for biogas production. The field experiment was established on Tingvoll research farm in 2011. A biogas plant was built at this farm in 2010, to digest the manure from a herd of about 25 organically managed dairy cows. This report describes the initial characterization of the soil biology, chemistry and physics, along with the background of the project, the selection process of the research field and the project design. Effects of the manure treatment and application will be studied during 2011-14. The aim of this report is to function as a reference for later publications, and to inform other scientists establishing medium long-term field trials. Except from a few results on water-soluble C and soil microbiology from 2011, all results presented here are based on studies conducted in autumn 2010 or spring 2011, before any manure was applied. Effects of the experimental treatments were studied for different soil characteristics in 2011, 2012 and 2013 and will be presented in separate publications. The field experiment has two cropping systems; grass (perennial grass-clover ley) with 20 experimental plots, and arable with 20 plots. Each experimental plot measures 3 m x 8 m. The ley was established in 2009 with cereals as a cover crop. The arable system was established in 2011, by ploughing a part of this ley. In the arable system, the soil is ploughed annually in spring, no legumes are grown, and aboveground plant material is removed at harvest. This practice is intended to stress the maintenance of soil organic matter in the arable system, to possibly reveal clearer effects of the experimental treatments. Within each cropping system, five experimental treatments are compared. They comprise two fertilization levels for each type of manure, plus a control treatment with no manure application. Each treatment has four replicates, randomly distributed within four blocks in each system. There is a significant soil variation on the experimental field. However, for most of the studied characteristics, no statistically valid differences were found between average values across Blocks within each cropping system. The content of soil organic matter (SOM) is higher in the grass system than the arable system.In the upper soil layer (0-20 cm) the average SOM content measured by ignition loss was 11.3 % in the grass and 6.6 % in the arable system. Analyzed by total-C measurements, the corresponding SOM values were 11.03 % and 5.97 %. In Norwegian soil, SOM values between 3 and 6 % are regarded as high humus contents (“moldrik”), whereas values between 6 and 12 % are regarded as very high. The average values for total C (0-20 cm) were 6.41 in the grass and 3.47 % in the arable system, and for total-N 0.39 and 0.21 %. On average for all treatments in the grass system (n= 20), the upper soil layer contained 0.32 mg organic C per g soil (air dried) by extraction in cold water (CWEC), increasing to 1.7 mg by hot water extraction (HWEC). In the arable system, the corresponding values were 0.23 and 1.1 mg. The SOM content of the grass system was higher and more variable than that of the arable system,and differences between blocks were greater and more statistically significant in the grass than in the arable system. Differences in the initial SOM between the means of plots that have been assigned to different subsequent treatments of manure applications were on the whole much smaller than those between blocks within the same crop system. Nevertheless, significant differences were found in some cases, and thus the initial SOM status of the soil should be taken into account when interpreting differences that may arise after the treatments have been carried out for a number of years. The soil texture, loamy sand (‘siltig mellomsand’) was similar in all replicate blocks and both depths in the grass system. It was slightly heavier and somewhat more variable in the arable system, with on average 16 % less sand, 11 % more silt and 4 % more clay. Somewhat heavier soil in the deeper parts of the terrain may be explained by washing out the soil layer during postglacial land elevation. The gravel contents were fairly low (< 10 %) in all cases. Soil moisture retention and aeration properties of the upper soil layer were measured on each plot. Total porosity, aeration properties and moisture retention at low tension were all clearly greater in the grass system than in the arable system. Satisfactorily high levels of aeration and plant-available water-holding capacity were found in both systems. Close relationships were seen between the moisture retention and the soil organic matter content. This accounts for many of the differences in such properties that were found between blocks. Soil aggregate size distribution was measured in the seedbed of the arable system plots. This confirmed that the predominant structure of the soil may be described as ‘single-grain’, with only 16 % aggregates of 2-6 mm and 16 % aggregates > 6 mm. There was little variation between Blocks in the aggregate size distribution. The stability of soil aggregates (2-6 and 6-10 mm) to simulated rainfall was high (>85 %) in all cases, with little variation between blocks or treatment means. The soil nutrient content was comparable in the two cropping systems. The nutrient concentrations in the upper soil layer (0-20 cm) were P-AL 2.87/2.31; K-AL 5.25/5.24; Mg-AL 4.34/3.53; Ca-AL 107.6/80.7; K-HNO3 122.4/175 mg of nutrient 100 g-1 dry soil in the grass/arable system. The pH value (H2O) was 5.82/5.87. The accumulated soil respiration and the microbial community structure differed between the grass and the arable system. Soil respiration seemed to be influenced both by manure Application and cropping system. In 2011, no significant change in the soil microbial community structure was found five days after manure application. This, however, may change with repeated manure applications over several years. Five earthworm species were identified in the field experiment. Apporrectodea caliginosa was the most common, but also Lumbricus terrestris was abundant. Octolasion cyaneum was found mainly in the arable system. The average density was 133 earthworms m-2 in the grass system and 117 in the arable system. The average biomass was somewhat higher in the arable system (63.5 g m-2)than in the grass system (42.1 g m-2). Collembolans were sampled from the grass system, in treatments with no or high manure application (but before manure application), from totally 12 plots. 17 species of collembolans were found, with an average density of and 7950 individuals m-2. The variation in species composition and density was high, and larger between treatments than between blocks. 11 species were found in all treatments. The most numerous collembolan species were the soil dwelling, white Mesaphorura macrochaeta and Protaphorura armata, and the litter dwelling greenish Isotomurus graminis

ANIMAL MANURE – REDUCED QUALITY BY ANAEROBIC DIGESTION?

In this paper, we present results from three growing seasons, 2011-2013 to discuss whether anaerobic digestion of animal manure impacts soil characteristics and plant yields

Earthworms: Interactions with management; impacting plant growth?

This paper reviews several studies of earthworms in agricultural soil in Norway. Crops and management significantly influence the earthworm fauna