| 1. |
- Abubaker, Jamal, et al.
(författare)
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Short-Term Effects of Biogas Digestates and Pig Slurry Application on Soil Microbial Activity
- 2015
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Ingår i: Applied and Environmental Soil Science. - : Hindawi Limited. - 1687-7667 .- 1687-7675. ; 2015, s. 1-15
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Tidskriftsartikel (refereegranskat)abstract
- The effect of four biogas digestates (BD-A, BD-B, BD-C, and BD-D) and pig slurry (PS) on soil microbial functions was assessed at application rates corresponding to 0–1120 kg-N ha−1. At dose corresponding to 140 kg-N ha−1, 30.9–32.5% of the carbon applied in BD-A, BD-C, and PS was utilized during 12 days, while for BD-B and BD-D corresponding utilization was 19.0 and 16.9%, respectively. All BDs resulted in net nitrogen assimilation at low rates (17.5–140 kg-N ha−1) but net mineralization dominated at higher rates. PS resulted in net mineralization at all application rates. All residues inhibited potential ammonium oxidation (PAO), with EC50-values ranging between 45 and 302 kg-N ha−1. Low rates of BDs appeared to weakly stimulate potential denitrification activity (PDA), while higher rates resulted in logarithmic decrease. The EC50-values for PDA were between 238 and 347 kg-N ha−1. No inhibition of PDA was observed after amendment with PS. In conclusion, biogas digestates inhibited ammonia oxidation and denitrification, which could be an early warning of potential hazardous substances in the digestates. However, this effect can also be regarded as positive, since it may reduce nitrogen losses.
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| 2. |
- Bergkvist, Göran, et al.
(författare)
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Fruit Tree-Based Agroforestry Systems for Smallholder Farmers in Northwest Vietnam-A Quantitative and Qualitative Assessment
- 2020
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Ingår i: Land. - : MDPI AG. - 2073-445X. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Rapid expansion of unsustainable farming practices in upland areas of Southeast Asia threatens food security and the environment. This study assessed alternative agroforestry systems for sustainable land management and livelihood improvement in northwest Vietnam. The performance of fruit tree-based agroforestry was compared with that of sole cropping, and farmers' perspectives on agroforestry were documented. After seven years, longan (Dimocarpus longan Lour.)-maize-forage grass and son tra (Docynia indica (Wall.) Decne)-forage grass systems had generated 2.4- and 3.5-fold higher average annual income than sole maize and sole son tra, respectively. Sole longan gave no net profit, due to high investment costs. After some years, competition developed between the crop, grass, and tree components, e.g., for nitrogen, and the farmers interviewed reported a need to adapt management practices to optimise spacing and pruning. They also reported that agroforestry enhanced ecosystem services by controlling surface runoff and erosion, increasing soil fertility and improving resilience to extreme weather. Thus, agroforestry practices with fruit trees can be more profitable than sole-crop cultivation within a few years. Integration of seasonal and fast-growing perennial plants (e.g., grass) is essential to ensure quick returns. Wider adoption needs initial incentives or loans, knowledge exchange, and market links.
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| 3. |
- Dahlin, Sigrun, et al.
(författare)
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Allanblackia – a tree crop under current domestication: What are the soil requirements and symbionts?
- 2012
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- In order to improve livelihoods and enhance food security and resilience of rural communities, diverse and multifunctionalagricultural systems are promoted. There has long been a lack of investment in domestication of plant species that arespecifically suited to African farmers' circumstances, but there is now a growing demand for commercialization and use of localcrops and trees. One example is the indigenous tree Allanblackia which seeds contain high-value edible oil. Traditionally,Allanblackia seeds have been collected from wild stands by rural communities, but more recently access to wild stands isthreatened by deforestation. During the last decade, Allanblackia oil has further received attention from industry as raw materialin the production of spreads and soaps, increasing the demand for Allanblackia seeds. In response to this ICRAF in 2002launched a research program aiming for the domestication of Allanblackia tree species on smallholder farms. Up to now,research activities have focused on selection of highly productive plant materials and propagation methods. However, to fullyoptimize the harvest potential of domesticated Allanblackia, the trees´ requirements for nutrients and water must be met, butknowledge on this is largely lacking. Work carried out on management of Allanblackia seedlings at the nursery has preliminarilyshown that incorporation of soil collected from native Allanblackia stands in the potting medium enhances growth of seedlings,indicating a positive plant-microbial interaction. Symbiotic relationships between plants and micro-organisms are very commonand often stimulate nutrient and water uptake from the soil. However, in this case it remains to clarify if such interaction existsand, if so, which organisms are involved and how they can be promoted in the nursery and on farm-land. The purpose of thisstudy is to obtain information about the environmental requirements of Allanblackia and it has two main objectives. The generalsoil chemical and physical parameters of natural A. stuhlmannii stands will be determined and will with information on climaticconditions and the soil water regime be used to characterise the abiotic requirements of the species. Biological enhancing factorswill be sought, with a particular focus on mycorrhizal symbionts. The fieldwork will be carried out during August-September2012, in the Eastern Arc Mountains, Tanzania. Together with local expertise and researchers at ICRAF, native Allanblackiastands will be localised and site characteristics, such as elevation, slope and drainage assessed. In addition, soil samples will becollected for characterisation of chemical and physical properties, such as soil pH, major plant nutrients, soil organic carbon, soiltexture, bulk density and water holding capacity. The root systems will also be traced from the tree and root fragments collected,bleached and stained. These will subsequently be examined for occurrence of arbuscules and vesicles in the search for possiblesymbionts, and degree of colonisation determined. The study will provide knowledge on the environmental requirements andbiological relationships essential for understanding the tree's biology and appropriate cultivation practices and thus contribute tothe domestication process. Preliminary results will be presented at the conference.
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| 4. |
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| 5. |
- Dahlin, Sigrun, et al.
(författare)
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Cutting regime affects the amount and allocation of symbiotically fixed N in green manure leys
- 2010
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Ingår i: Plant and Soil. - : Springer Science and Business Media LLC. - 0032-079X .- 1573-5036. ; 331, s. 401-412
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Tidskriftsartikel (refereegranskat)abstract
- Cutting strategy effect on N(2) fixation and distribution of fixed N above and below ground in red clover (Trifolium pratense L.) and mixed red clover/perennial ryegrass (Lolium perenne L.) green manure leys was quantified in field experiments including in situ mezotrons and microplots. Symbiotically fixed N in clover, transfer of fixed N to grass in the mixed stands and the fate of (15)N contained in mulch were estimated by isotope dilution. Below ground clover-derived N was estimated by leaf labelling. Total N(2) fixation was estimated by correcting fixed N in plant shoots with plant-derived N below ground and recycled N from mulch. The total N(2) fixation was larger in harvested and mulched stands (average 45 g m(-2)) than in the intact stands (32 g m(-2)). Of the fixed N, 53% (intact), 46% (harvested) and 60% (mulched) was found below ground. The average recycling of N in mulch was 21% and contributed 13.7% (pure clover) and 2.2% (mixed) of the clover N in the regrowth. Recycling of N did not decrease N(2) fixation in the mulched compared with harvested stands. The results indicate that cutting regime should be considered when estimating total amounts of N fixed by green manure leys.
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| 6. |
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| 7. |
- Dahlin, Sigrun
(författare)
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Does labour invested in sustainable intensification practices give sufficient yield returns?
- 2018
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Annan publikation (populärvet., debatt m.m.)abstract
- The increasing demands for nutritious food, feed, fibre and fuel of a growing world population with changing consumption patterns cannot be satisfied through increasing the arable land area. Sustainable intensification of crop production is needed, as in producing more without environmental harm but with positive effects on natural resources, profits and social capital. However, smallholder farming systems in e.g. sub-Saharan Africa (SSA) face many barriers to increased crop productivity, one being labour shortages during key periods that strongly influence yields. For example, insufficient labour often leads to late planting and a mismatch with the growing season, and to poor weed control leading to high competition for nutrients, water and light and thus to low yields.
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| 8. |
- Dahlin, Sigrun, et al.
(författare)
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Effect of grass-diet and grass-legume-diet manure applied to planting holes on smallholder maize production in Rwanda
- 2021
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Ingår i: Field Crops Research. - : Elsevier BV. - 0378-4290 .- 1872-6852. ; 263
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Tidskriftsartikel (refereegranskat)abstract
- Animal manure provides plant nutrients and also affects soil nutrient availability, pH buffering and soil physical properties through its contribution to soil organic matter pools. However, the quality and quantity of manure are often low on smallholder farms in sub-Saharan Africa and the initial effect of manuring on crop yield may be small or even negative. In a two-factorial experiment over four seasons in southern Rwanda, the fertiliser value to a maize crop of manures produced by cattle fed a basal diet of only Chloris gayana grass or a mixed C. gayanaAcacia angustissima diet was compared with that of NPK 17-17-17 and no fertiliser. The potential liming effect of the manures was also evaluated through inclusion (or not) of travertine as the second factor. All amendments were applied only to maize planting holes. The crop failed in season 1 due to drought, but manure application (5 t ha-1) approximately doubled maize yield compared with the unfertilised control during seasons 2-4, while NPK (70 kg N ha-1) increased yield by 3- to 4-fold, with corresponding improvements in crop performance indicators. The mixed diet increased manure quality and maize yield compared with the grass diet in season 4. Liming showed a consistent tendency to improve crop performance indicators and yield, but significant differences were only identified in some cases, possibly because the pH increase was small. The results suggest that in regions where manure availability is limiting, application of reduced rates only to planting holes may be an efficient technology. Enhanced animal feed can result in higher quality manure, and ultimately increase crop yield, if nutrient losses during manure handling and storage can be limited.
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| 9. |
- Dahlin, Sigrun, et al.
(författare)
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Effect of wood ash and crushed rock soil amendments on red clover growth and dinitrogen fixation
- 2017
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Ingår i: Agricultural and Food Science. - 1459-6067 .- 1795-1895. ; 26, s. 188-197
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Tidskriftsartikel (refereegranskat)abstract
- The fertiliser effect of adding wood ash or crushed rock to a low-fertility soil, compared with an unamended control, was assessed in a pot experiment with a perennial ryegrass-red clover mixture. Dinitrogen (N-2) fixation by the clover and translocation of fixed N to the grass were determined using N-15 natural abundance. The wood ash produced the highest accumulated clover biomass over two cuts, followed by the crushed rock. Chemical analyses suggested that the increase was due to K supply by the amendments. The wood ash also led to larger amounts of fixed N compared with the control. However, N-2 fixation was not increased as much as biomass amount, leading to dilution of plant N. There were minor or no treatment effects on mineralisation from soil N pools. This indicates that good-quality wood ash can be successfully used as a multi-element soil amendment to enhance clover growth on low-fertility soils.
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| 10. |
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