| 1. |
- Getahun, Gizachew Tarekegn, et al.
(författare)
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Effects of loosening combined with straw incorporation into the upper subsoil on soil properties and crop yield in a three-year field experiment
- 2022
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Ingår i: Soil and Tillage Research. - : Elsevier BV. - 0167-1987 .- 1879-3444. ; 223
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Tidskriftsartikel (refereegranskat)abstract
- Subsoil management needs to be integrated into the current tillage regimes in order to access additional resources of water and nutrients and sustain crop production. However, arable subsoil is often deficient in nutrients and carbon, and it is compacted, affecting root growth and yield. In this study, crop yield and soil responses to loosening of the upper subsoil, without and with straw injection below the plough layer (25-34 cm), were studied during three crop cycles (2016-2018) in a field experiment near Uppsala, Sweden. Responses to straw injection after loosening were studied after single and triple consecutive applications of 24-30 Mg ha-1 during 2015-2017 to spring-sown barley and oats. Subsoil loosening combined with one-time or repeated straw addition (LS treatments) significantly reduced soil bulk density (BD) and increased porosity, soil organic carbon (SOC) and total nitrogen (N) compared with loosening (L) alone (one-time or repeated annually) and the control. In treatment L, the soil re-compacted over time to a similar level as in the control. Field inspections indicated higher abundance of earthworms and biopores in and close to straw incorporation strips. Aggregates readily crumbled/fragmented by hand and casts (fine crumbs) were frequently observed in earthworm burrows. The treatment LS improved soil properties (SOC and porosity) and water holding capacity, but had no significant influence on crop yield compared with the control. Crop yield in all treatments was 6.5-6.8 Mg ha-1 in 2017 and 3.8-4.0 Mg ha-1 in 2018, and differences were non-significant. Absence of yield effect due to treatments could be possibly due to other confounding factors buffering expression of treatment effects on yield. Lower relative chlorophyll content in leaves in the loosening with straw treatment during early growth stages, did not affect final crop yield. Subsoil loosening performed three times gave no further improvement in soil properties and grain yield compared with one-time loosening. There was no difference in yield between repeated subsoil loosening + straw and one-time treatment. It will be interesting to study the long-term effects of deep straw injection and evaluate its impact under other soil and weather conditions.
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| 2. |
- Getahun, Gizachew Tarekegn
(författare)
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Eleven Years' Effect of Conservation Practices for Temperate Sandy Loams: I. Soil Physical Properties and Topsoil Carbon Content
- 2017
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Ingår i: Soil Science Society of America Journal. - : Wiley. - 0361-5995 .- 1435-0661. ; 81, s. 380-391
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Tidskriftsartikel (refereegranskat)abstract
- Conservation agriculture (CA) has been suggested as a means of making intensification of agriculture sustainable. The purpose of this study was to understand and quantify long-term individual and combined effects of key conservation practices on soil physical properties and topsoil C content. Field experiments were conducted in 11- to 12-yr-old experiments on two Danish sandy loams at Foulum and Flakkebjerg. Three crop rotations/residue management treatments were compared and tillage was included as a split-plot factor. The tillage systems were moldboard plowing to a depth of 20 cm (MP), direct drilling (D) and harrowing to a depth of 8 to 10 cm (H). Soil sampling and in-field measurements were performed in autumn 2013 and spring 2014. In the field, soil structure was visually evaluated and penetration resistance (PR) measured. Soil C, wet stability (clay dispersion and wet aggregate stability), and soil strength were determined in the laboratory. The MP soil had a uniform soil organic carbon (SOC) content in the 0- to 20-cm depth of topsoil, whereas H and D resulted in SOC accumulation near the soil surface. Plowing resulted in the best visually assessed topsoil structure and had the lowest PR. However, H and D in combination with residue retention gave the best structural stability. Residue retention alleviated negative effects of reduced tillage on PR and improved wet stability in the MP treatment at the Foulum site. Clay and SOC correlated well with soil physical parameters, confirming their important role in soil structure formation and stabilization. Our study showed benefits of combining key CA elements, although longer-term studies are most likely needed to reveal the full potential.
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| 3. |
- Getahun, Gizachew Tarekegn, et al.
(författare)
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Impact of loosening and straw addition to the subsoil on crop performance and nitrogen leaching: A lysimeter study
- 2021
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Ingår i: Journal of Environmental Quality. - : Wiley. - 0047-2425 .- 1537-2537. ; 50, s. 858-867
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Tidskriftsartikel (refereegranskat)abstract
- Poor subsoil properties are difficult to ameliorate and detrimental to soil fertility and crop yield. The effects of loosening (L) and loosening + straw (LS) similar to 60 Mg ha(-1) into the subsoil (25-40 cm depth) on crop yield, water flow, and the nitrogen (N) balance components under bare soil conditions and a barley (Hordeum vulgare L.) crop were investigated in an about 21-mo lysimeter study and compared with a control treatment. Undisturbed soil columns (n = 12) were excavated from an agricultural field in May 2016, installed at a lysimeter station, and exposed to outdoor climatic conditions in Uppsala, Sweden, in August 2016. Spring barley ('Makof') was grown between June and September 2017. Total N leaching loads over the 21 mo were high (74-193 kg ha(-1)). The LS treatment reduced the N load by 49% (P = .01) and 62% (P = .001) compared with the L and control treatments, respectively. Loosening reduced N load by 25% (P < .07) compared with the control. Emissions of N2O were low (0.04-0.07 kg N ha(-1)), and no differences were observed between treatments. Leaf relative chlorophyll content was lower in the LS treatment than in the L and control treatments (P < .05). Yield was also lowest in the LS treatment (5.8 Mg ha(-1)) and was 7 and 8.5% lower than in the control and L treatments (P > .05), respectively. These results suggest that LS can reduce N leaching. The overall effects of LS on crop performance and N removal and leaching should be further scrutinized in long-term field studies.
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| 4. |
- Getahun, Gizachew Tarekegn, et al.
(författare)
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Liming with CaCO3 or CaO affects aggregate stability and dissolved reactive phosphorus in a heavy clay subsoil
- 2021
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Ingår i: Soil and Tillage Research. - : Elsevier BV. - 0167-1987 .- 1879-3444. ; 214
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Tidskriftsartikel (refereegranskat)abstract
- A 22-month incubation experiment was conducted to study the effect of lime on clay dispersion, wet aggregate stability (WAS) and dissolved reactive phosphorus (DRP), using a heavy clay subsoil with an initial pH of 7.0 and 7.3 g kg(-1) of soil organic carbon. Lime was applied to achieve soil pH values of 7.5, 8 and 8.4. Clay dispersion decreased linearly with increased pH (corresponding to an increase in lime amount) for both lime types (R-2 = 0.44 for CaO; R-2 = 0.53 for CaCO3, P < 0.05), with a decrease of 2-16 % (CaO) and 3-17 % (CaCO3) compared with the control.Both WAS and DRP followed piece-wise linear functions, with an increase and peak around pH 7.5-7.8, and a decline at higher pH (WAS: R-2 = 0.73 for CaO, R-2 = 0.68 for CaCO3, P < 0.001; DRP: R-2 = 0.84 for CaCO3, R-2 = 0.33 for CaO, P < 0.001). Wet aggregate stability increased on average by 13 % and 11 % at the lowest and intermediate levels, respectively, compared with the control. At the highest lime application rate, WAS was 6 % (CaO) and 8 % (CaCO3) lower than in the control. These differences were probably caused by changes in electrical charge and in concentrations of soluble calcium and dissolved organic carbon (DOC) as the pH increased. More studies are needed to understand the processes in detail and to draw conclusions that are more robust.
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| 5. |
- Getahun, Gizachew Tarekegn, et al.
(författare)
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Short-term effects of loosening and incorporation of straw slurry into the upper subsoil on soil physical properties and crop yield
- 2018
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Ingår i: Soil and Tillage Research. - : Elsevier BV. - 0167-1987 .- 1879-3444. ; 184, s. 62-67
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Tidskriftsartikel (refereegranskat)abstract
- Subsoils that are compacted, nutrient-poor or low in soil organic matter (SOM) often limit crop growth and yield. Improvement of subsoil conditions by deep loosening is laborious and expensive and its positive effect may not last. This study investigated the effect of deep loosening and injection of slurry made from cereal straw (30 Mg dry mass ha(-1)) at 25-34 cm depth on soil properties and crop performance in a Swedish field experiment that started in autumn 2015 and monitored soil and crop properties during 2016. Loosening + straw incorporation into subsoil resulted in significantly higher soil organic carbon (SOC) content, potential plant-available water and porosity and lower bulk density (BD) in spring 2016 compared with the control. In autumn 2016, penetrometer resistance (PR) and BD were both significantly lower and SOC and porosity were significantly higher in the loosening + straw treatment compared with the control and loosening only (29-34 cm). Furthermore, BD was significantly lower in the loosening + straw treated subsoil than in the top soil layer of the control (0-10 cm). Observations indicated that more continuous pores were found in the loosening + straw treatment than in other treatments. Roots and soil faunas were found more frequently where straw was incorporated. Grain yield increased by 5.6% due to loosening + straw addition (P = 0.03) and by 4% due to loosening only (P = 0.06). These results indicate that loosening + straw input into upper subsoil had a positive short-term influence on soil physical properties, potential plant-available water and grain yield. Straw addition prolonged the positive effect of loosening.
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| 6. |
- Getahun, Gizachew Tarekegn
(författare)
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Subsoil improvement for sustainable intensification : impact of loosening with straw incorporation or liming on subsoil properties, crop performance and water quality
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Subsoil has a high capacity for nutrient and water retention, but arable subsoil is often nutrient poor, carbon-deficient and compacted, affecting both root growth and yield. In field and lysimeter experiments, this thesis investigated the effects of subsoil loosening and loosening with cereal straw incorporation (24-60 Mg ha-1) (loosening + straw) on crop yield, soil properties (bulk density, penetration resistance, moisture characteristics) and leaching. A rectangular metal tube welded behind each tine of a deep loosener was used to inject straw as a slurry in the field, while subsoil was loosened and mixed manually with milled straw in lysimeter studies. In laboratory experiments, subsoil was limed with different amounts of CaCO3 and CaO to increase soil pH from 7.0 to 7.5, 8.0 and 8.4 and incubated for 22 months to examine changes in soil structural stability and dissolved reactive phosphorus. Field subsoil loosening + straw significantly increased soil organic carbon, total nitrogen and water holding capacity. It also decreased bulk density, from around 1.5 Mg m-3 in the control to about 1.0 Mg m-3. The effects of loosening + straw persisted for at least three years, but loosening alone had weak and short-lived effects. Loosening + straw significantly increased grain yield in the first cropping season (6% higher than the control), but not in the following two years. Nitrogen balance calculations of lysimeters showed that short-term nitrogen losses were lowest in the subsoil loosening + straw treatment and that nitrogen leaching was reduced by about 62%. In incubations, subsoil liming decreased clay dispersion. Wet aggregate stability and concentration of dissolved reactive phosphorus increased and peaked around pH 7.8 and 7.5, respectively. Combining loosening with straw incorporation into subsoil appeared to improve soil properties and water quality, but not crop yield on the experimental soil. On other soil types, this practice may have more beneficial effects.
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| 7. |
- Rychel, Katrin, et al.
(författare)
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Deep N fertilizer placement mitigated N2O emissions in a Swedish field trial with cereals
- 2020
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Ingår i: Nutrient cycling in agroecosystems. - : Springer Science and Business Media LLC. - 1385-1314 .- 1573-0867. ; 118, s. 133-148
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Tidskriftsartikel (refereegranskat)abstract
- Deep fertilizer placement is a proposed strategy to increase crop yield and nitrogen (N) use efficiency while decreasing nitrous oxide (N2O) emissions from soil to atmosphere. Our objective was to test three fertilization depth orientations to compare overall N use efficiency, based on a 2-year field trial on a mineral soil cropped with cereals in Uppsala, Sweden. The field was fertilized with ammonium nitrate at a rate of 120 kg ha(-1)(2016) and 105 kg ha(-1)(2017) and a deep fertilizer placement (DP) at 0.20 m was compared to a shallow placement (SP) at 0.07 m and a mixed-depth placement (MP) where fertilizer was halved between the depths of 0.07 and 0.20 m, and a non-fertilized control (NF). In 2016, compared to SP, MP and DP increased N content in harvested grain by 3.6% and 2.5% respectively, and DP increased grain yield by 11% (P < 0.05). In both years, N2O emissions were similar in DP and NF, whereas SP and MP emissions were similar but generally higher than those in DP and NF. Fertilizer-induced emission factors (EF) for the growing season of 2017 decreased with fertilizer placement depth and were 0.77 +/- 0.07, 0.58 +/- 0.03, and 0.10 +/- 0.02 for SP, MP, and DP, repectively. Although deep N placement benefits are likely dependent on weather conditions and soil type, this strategy has a clear potential for mitigating N2O emissions without adversely affecting yield.
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| 8. |
- Rychel, Katrin, et al.
(författare)
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Lysimeter deep N fertilizer placement reduced leaching and improved N use efficiency
- 2023
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Ingår i: Nutrient cycling in agroecosystems. - 1385-1314 .- 1573-0867. ; 126, s. 213-228
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Tidskriftsartikel (refereegranskat)abstract
- Deep fertilization has been tested widely for nitrogen (N) use efficiency but there is little evidence of its impact on N leaching and the interplay between climate factors and crop N use. In this study, we tested the effect of three fertilizer N placements on leaching, crop growth, and greenhouse gas (GHG) emissions in a lysimeter experiment over three consecutive years with spring-sown cereals (S1, S2, and S3). Leaching was additionally monitored in an 11-month fallow period (F1) preceding S1 and a 15-month fallow period (F2) following S3. In addition to a control with no N fertilizer (Control), 100 kg N ha(-1) year(-1) of ammonium nitrate was placed at 0.2 m (Deep), 0.07 m (Shallow), or halved between 0.07 m and 0.2 m (Mixed). Deep reduced leachate amount in each cropping period, with significant reductions (p < 0.05) in the drought year (S2) and cumulatively for S1-S3. Overall, Deep reduced leaching by 22, 25 and 34% compared to Shallow, Mixed and Control, respectively. Deep and Mixed reduced N leaching across S1-S3 compared with Shallow, but Deep further reduced N loads by 15% compared to Mixed and was significantly lowest (p < 0.05) among the fertilized treatments in S1 and S2. In S3, Deep increased grain yields by 28 and 22% compared to Shallow and Mixed, respectively, while nearly doubling the agronomic efficiency of N (AE(N)) and the recovery efficiency of N (REN). Deep N placement is a promising mitigation practice that should be further investigated.
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