Trond Børresen

Ploughing and rotary cultivation for cereal production in a long-term experiment on a clay soil in southeastern Norway. 1. Soil properties

Rotary cultivation to 10 cm depth versus mouldboard ploughing to 25 cm depth at two rates of nitrogen application (50 and 100 kg ha−1) were investigated in a factorial field experiment on a clay soil at Tune in southeastern Norway. The experiment was started in the autumn of 1976, and the measurements discussed in this paper were made in 1989. The main crops were spring barley (Hordeum vulgare L.) and spring oats (Avena sativa L.). The soil structure was measured by volumetric relations, aggregate stability and cone penetrometer resistance in the soil after 13 years with rotary cultivation and ploughing. The soil structure had improved on the rotavated soil with regard to plant growth requirements and erosion control. Aggregate stability was about 15 g per 100 g greater on rotavated as compared with ploughed soil. This could be explained by the increased content of organic matter in soil which had not been ploughed, but only rotavated for 13 years. The content of organic matter had on the average increased by 0.06 g per 100 g year−1 in the top layer (0–5 cm) in rotavated soil, and had remained constant in ploughed soil. The penetration resistance was similar for rotavated and ploughed soil for the upper 15 cm. The soil physical parameters were measured at one level of applied nitrogen (100 kg ha−1). The pH had decreased 0.006 units per year in the upper 20 cm after rotary cultivation as compared with ploughing. In this experiment the drop in pH was not an effect of nitrification. Available phosphorus and available potassium were significantly greater in the top layer (0–5 cm) in rotavated soil. The difference in available potassium between ploughed and rotavated soil had remained relatively constant since 1980, while the difference in available phosphorus had increased. Soil pH and nitrate concentration were affected by nitrogen fertilization.

Measuring differences in soil properties in soils with different cultivation practices using computer tomography

Abstract A change in tillage practice from mouldboard ploughing to reduced tillage with a rotavator is suggested to reduce problems with soil erosion in Norwegian soils. The long-term effects on soil properties by this change have to be investigated in order to maintain agricultural production and avoid new negative side effects on the environment. In this investigation, soil with 4entional tillage practice was compared to soil with reduced tillage using computer tomography (CT). The advantage of CT is that it nondestructively provides a spatial density distribution. The macropores are effectively separated from the soil matrix with micropores. It was found that soil with conventional tillage had a loose structure with a wide range of densities in the ploughing layer. Below the ploughing depth the soil was compact with very little macropores. The soil with reduced tillage had a nearly uniform density profile, but macroporosity in the subsoil was significantly larger than near the surface. Computer tomography is a useful tool for nondestructively measuring bulk density and macroporsity. The effect of an increased number of macropores on solute infiltration was also visualised using CT.

The effect of ploughing depth and seedbed preparation on crop yields, weed infestation and soil properties from 1940 to 1990 on a loam soil in south eastern Norway

Abstract The effect of ploughing depths, seedbed preparation and nitrogen fertilisation on a loam soil (fluvaquentic humaquept) were investigated in a factorial field experiment on a loam soil at As in southeastern Norway. The experiment was established in the autumn of 1939, reorganised in 1962 and was completed in the autumn of 1990. The working depths for ploughing (12, 18 and 24 cm) and seedbed cultivation (4, 8 and 12 cm) were constant during the whole research period. Different nitrogen application rates (50, 100, 150 kg ha−1) and seedbed preparation implement treatments (S-tine vs. rotary cultivator) were superimposed on the experiment in a factorial configuration in 1962. Since 1962 the main crops have been barley (Hordeum vulgare L.), oats (Avena sativa L.) and ley (timothy (Phleum pratense L.) and red clover (Trifolium pratense L.)). The yield loss for shallow ploughing (12 cm) was most pronounced in years with high weed infestation and at low nitrogen application rate (50 kg ha−1). Shallow harrowing with an S-tine cultivator (4 cm, one pass) significantly reduced cereal yields compared with more intensive and deeper cultivation. The soil structure measured from 1968 to 1987 appeared to be slightly better with regard to plant growth requirements after shallow (12 cm) compared with deep (24 cm) ploughing. Bulk density was lower and the porosity greater in the 7–11 cm layer after shallow compared with deep ploughing. The modulus of rupture increased significantly with ploughing depth. The amount of organic matter at the 0–40 cm depth was not influenced by ploughing depth. However, the content of organic matter in the surface layer was greater after shallow ploughing. Mineralisation of organic matter was estimated to be about 36 kg N ha−1 year−1 greater for a nitrogen application rate of 50 kg ha−1 compared with 150 kg ha−1. In the 0–40 cm layer the amount of organic matter on average decreased by about 1650 kg ha−1 year−1 from 1944 to 1987.

Ploughing and rotary cultivation for cereal production in a long-term experiment on a clay soil in southeastern Norway. 2. Yields and weed infestation

Rotary cultivation to 10 cm depth (rotavator) and ploughing to 25 cm depth (mouldboard plough) were compared at two nitrogen application rates (50 and 100 kg ha−1 in a factorial experiment on a clay soil at Tune in southeastern Norway. The experiment was established in the autumn of 1976. Changes in soil properties after 13 years of treatment are discussed in a first paper (Borresen, T. and Njos, A., 1993. Soil Tillage Res., 28: 97–108). In this paper quantity and quality of yields and weeds infestation during 14 years are discussed. The main crops were barley (Hordeum vulgare L.) and oats (Avena sativa L.). Rotary cultivation yielded 200 kg ha−1 more on average than ploughing. Particularly in years with dry early summer, rotary cultivation gave significantly higher yields compared with ploughing. The nitrogen content in the cereal increased when grown on rotavated soil. The total uptake of nitrogen in grain and straw was frequently greater on rotavated soil. On average the difference was as high as 5 kg ha−1 in grain and 2 kg ha−1 in straw. Loding increased and the grain percentage decreased if the solid was rotavated. Phosphorus, potassium, calcium and magnesium contents of the grain were not affected by the tillage system. The infestation of couch grass (Elytrigia repens L. Nevski) and other weeds was greater on the rotavated soil and more pronounced at the beginning of the experiment than in later years. It was necessary to apply glyphosate for 5 years during this period to control the couch grass and other perennial weeds.

Long-term experiment with straw management, stubble cultivation, autumn and spring ploughing on a clay soil in S.E. Norway

Autumn vs. spring ploughing, stubble cultivation and straw management were investigated in a factorial field experiment on a clay loam at Tune in S.E. Norway. The experiment was started in the autumn of 1963 and was completed in the aut3mn of 1984. The main crops were barley (Hordeum vulgare L.) and oats (Avena sativa L.). Autumn ploughing gave significantly higher yields, 420 kg ha−1 higher on average, than spring ploughing. The combination spring ploughing/no stubble cultivation/incorporated chopped straw treatment gave a yield decrease of 608 kg ha−1 year−1 as compared with autumn ploughing/no stubble cultivation/burnt straw. Incorporation of straw by stubble cultivation in combination with autumn ploughing was the best management practice as far as yields are concerned. The seedbed in spring was finer in the autumn ploughed soil because of the effect of freezing and thawing. Stubble cultivation had little effect when the soil was ploughed in autumn. To avoid yield depression after spring ploughing it was important to incorporate the straw by stubble cultivation in autumn. Stubble cultivation depressed the infestation of couch grass (Elytrigia repens L. Nevski). Burning straw resulted in higher yields when the soil was ploughed in spring and also reduced infestation of weeds. The positive effect of burning on yield was especially clear on spring ploughed soil without stubble cultivation. After 19 years of ploughing in cereal straw, aggregate stability and organic matter content in the soil had increased as compared with burning. The increase in organic matter was 0.3%. Other physical properties were not influenced by straw management.

Recent yield results and trends over time with conservation tillage on clay loam and silt loam soils in southeast Norway

Abstract Yields are reported from four long-term (16–30 years) tillage trials, comparing results since 1998, under relatively wet conditions, with earlier experience. In trial 1, on clay loam, mean grain yield with spring harrowing only, has since 1998 been 87% of that obtained with autumn ploughing, whereas it was 94% for the whole period since 1991. The inclusion of autumn harrowing increased these figures to 94 and 98%, respectively. Over the last six years, spring ploughing gave 5% lower yield than did autumn ploughing. Relative yields of unploughed versus ploughed treatments were negatively correlated with summer rainfall. Grain protein was lowest with spring harrowing only. In trial 2, on clay loam, direct drilling has since 1998, as in previous years, given around 10% lower yield than has autumn ploughing. Autumn harrowing gave 4% lower yield in winter wheat and 6% higher yield in spring oats than did autumn ploughing, whilst yields of spring turnip rape were not significantly affected by tillage. In trial 3, also on clay loam, six alternative straw treatments were compared under four unploughed tillage regimes. Relative to straw removal, retaining large residue amounts depressed yields hardly at all with autumn and spring harrowing, but by 7% with spring harrowing only and by 13% with direct drilling. Overall, direct drilling gave 18% lower yields in this trial than did autumn and spring harrowing, whilst the yield reduction with spring harrowing only was 7%. In trial 4, on silt loam, both spring harrowing only and direct drilling have since 1998 given 6% lower yield than has autumn ploughing, whereas autumn and spring harrowing has given 6% higher yield. Under drier conditions during 1991–1997, autumn ploughing gave up to 11% lower yield than did unploughed treatments. Straw retention was beneficial in the absence of ploughing during that period, but has had little effect in more recent years.

Effects of adding moraine soil or shell sand into peat soil on physical properties and grass yield in western Norway

Abstract In terms of agricultural use, peat soils have weak structure, high water content, insufficient soil aeration and poor thermal properties resulting in suboptimal physical properties and yields of grass. During the period 1978–1995, a long-term field trial was conducted on highly decomposed peat soil in order to investigate the impact of adding mineral materials to improve soil characteristics and increase grass yield. Shell sand or moraine soil (200, 400 or 800 m3 ha−1) was incorporated into peat soil. Generally, addition of both shell sand and moraine soil improved the physical properties of the soil and grass production. During the first nine years, shell sand (400 m3 ha−1) was the most efficient. Thereafter, moraine soil (400 and 800 m3 ha−1) seemed most beneficial. This study indicates that additions of shell sand or moraine soil to peat are appropriate methods to improve and conserve the physical properties and cropping potential of these vulnerable soils.

Traffic-induced soil compaction during manure spreading in spring in South-East Norway

The objective of this study was to evaluate long-term effects of two tillage regimes (ploughing and minimum tillage) on the bearing capacity of a clay rich soil, by using two different slurry tankers (4.1 and 6.6 Mg wheel load) and contrasting wheeling frequencies (1 and 10 passes). The soil strength was assessed by laboratory measurements of the precompression stress (Pc) at −6 kPa in topsoil (20 cm) and subsoil (40 and 60 cm) samples. Stress propagation, elastic and plastic deformation during wheeling were measured in the field with combined stress-state-transducer and displacement transducer system. Results presented in this study show that minimum tilled soil had 74% higher Pc than ploughed soil in the upper soil layer, whilst differences were less distinct in subsoil. Wheeling increased Pc at all soil depths. Compared to ploughing, higher strength in the upper layer of minimum tilled soil led on average to 60% and 48% reductions in the major principal stress with the use of the light and heavy slurry tanker, respectively. The extent of the major principal stress was dependent on the ground pressure in the topsoil. The first pass of a wheel caused the greatest damage in some cases, but all wheelings led to accumulative plastic deformation in both vertical and horizontal directions. Wheeling with high intensity would have exceeded Pc in all cases when soil was at a matric potential of −6 kPa. The results show that soil water content is an important factor influencing bearing capacity. Drier soil (−100 kPa), in combination with minimum tillage, limited the occurrence of stresses exceeding Pc in the upper soil layer.

Effect of tillage methods on soil erosion in Norway

Abstract Soil erosion is considered a serious environmental problem in parts of Norway. The effect on water quality is the most important concern, and the improvement of water quality is the major aim for mitigation techniques and regulations on tillage. Documentation of effects of tillage practices therefore has a high priority. In this paper, results from five plot experiments are presented. They are all located in the grain-growing district in southeastern Norway on clay and loam soils. Tillage treatments for spring cereals and winter cereals are compared. The effect of tillage is pronounced on erodible soils. The results showed that annual average soil losses in surface runoff for autumn-tilled and spring-tilled plots were 7 and 0.8 t ha−1yr−1 at Bjørnebekk; 4.3 and 0.4 t ha−1yr−1 at Askim; 2.6 and 0.2 t ha−1yr−1 at Hellerud; 1.1 and 0.2 t ha−1yr−1 at Øsaker; and 0.18 and 0.1 t ha−1yr−1 at Syverud, respectively. The corresponding total phosphorus losses were 8.4 and 1.5 kg ha−1yr−1 at Bjørnebekk; 4.5 and 0.8 kg ha−1yr−1 at Askim; 3.0 and 0.8 kg ha−1yr−1 at Hellerud; 1.30 and 0.44 kg ha−1yr−1 at Øsaker; and 0.43 and 0.45 kg ha−1yr−1 at Syverud for autumn and spring tillage, respectively. The effects were less pronounced on soils with a lower erodibility, but reduced autumn tillage is the most effective way to mitigate soil erosion as well as total phosphorus losses. The study also showed that the total phosphorus losses are closely correlated with soil losses. The results show the importance of soil tillage for soil and phosphorus losses and suggest that farmers avoid autumn tillage on areas with high erosion risk.

Effects of eucalyptus and coniferous plantations on soil properties in Gambo District, southern Ethiopia

Abstract Plantation establishment using exotic species on disturbed cultivated and undisturbed primary forest soils is common in Gambo district, southern Ethiopia, but their effects on soil properties are not fully known. This study investigated the effects of plantation species on major soil physical and chemical properties and further evaluated the soil quality under different land uses. Soil samples in triplicates, collected under different plantations, were analysed for their physical and chemical properties. Based on these soil properties, an integrated soil quality index was determined. The soil bulk density (BD) varied from 0.72 to 0.80 cm−3 in plantations established on primary forest land and natural forest and from 0.86 to 1.14 g cm−3 in those plantations established on cultivated soils. Also significantly lower pore volume and infiltration rate were observed under plantations established on cultivated lands than those on primary forest soils. Higher water volume (% at −1500 kPa matric potential) was obtained in soils under Juniperus procera and natural forest compared with that under the rest of the plantations investigated. The concentration of soil organic carbon (SOC) varied from 3.4 to 10.2%, N from 0.3 to 1.0% and Av.P from 1.5 to 7.0% in soils under plantations and natural forest. Exchangeable cations generally showed a decreasing trend with depth in all land use types with minor exceptions. The concentrations of exchangeable Ca+2 varied from 6.5 to 22.7 cmol kg−1 and were significantly higher under Juniperus procera than under Eucalyptus species. The soil under plantations on previously cultivated lands showed soil quality index below 0.5 (the baseline value), while those established on undisturbed forest soil were generally above that value. The study results suggest that selecting species such as Juniperus procera and prolonging the harvesting period would improve and maintain the quality of soil properties.