| 1. |
- Chilundo, Mario, et al.
(författare)
-
Effects of reduced irrigation dose and slow release fertiliser on nitrogen use efficiency and crop yield in a semi-arid loamy sand
- 2016
-
Ingår i: Agricultural Water Management. - : Elsevier BV. - 0378-3774. ; 168, s. 68–77-
-
Tidskriftsartikel (refereegranskat)abstract
- Quantification of the interactive effects of irrigation water and nitrogen (N) fertiliser on nitrogen use efficiency (NUE) provides an important insight for more effective water and N management. This study evaluated the effects of different irrigation and N fertiliser management options on water flux, N uptake, NUE and maize grain yield in a semi-arid loamy sand, in Mozambique. The experiments were carried out in field plots in two consecutive cropping periods (CP's) representing contrasting growing seasons: a hot-wet season (CP-1) and a cold-dry season (CP-2). The treatments included two irrigation methods (furrow and drip), two irrigation levels (75 and 100% of the crop water requirement), and two distinct N fertiliser types (a quick-release and slow-release urea) arranged in a randomised complete block design. In both CP-1 and CP-2, NUE tended to be higher for the 75% irrigation level, regardless of irrigation method and N fertiliser type. Higher NUE was generally observed in CP-2 than in CP-1. The highest grain NUE (41.6 kg kg(-1) N) was observed in CP-2 under furrow irrigation combined with 75% irrigation level and quick-release N fertiliser. Slow-release N fertiliser did not improve N uptake, NUE or maize yield. Potential N losses were assumed to be higher in CP-1 than in CP-2, associated with higher estimated deep percolation volumes in CP-1 (mean 127 mm) than in CP-2 (mean 12 mm). In CP-1, deep percolation events mainly coincided with high rainfall events. Furrow irrigation tended to give higher NUE than drip irrigation, especially in CP-2. Reducing of irrigation level by 25% tended to increase N uptake, NUE and maize yield for both CP-1 and CP-2. The effects of slow-release N fertiliser and drip irrigation were inconclusive. (C) 2016 Elsevier B.V. All rights reserved.
|
|
| 2. |
- Chilundo, Mario, et al.
(författare)
-
Influence of irrigation and fertilisation management on the seasonal distribution of water and nitrogen in a semi-arid loamy sandy soil
- 2018
-
Ingår i: Agricultural Water Management. - : Elsevier BV. - 0378-3774. ; 199, s. 120-137
-
Tidskriftsartikel (refereegranskat)abstract
- Increased use of irrigation on semi-arid sandy soils requires optimisation of irrigation and fertilisation practices to reduce water and nitrogen (N) losses. Field experiments were conducted on a semi-arid loamy sandy soil in two consecutive cropping periods, one in a cold-dry season (CP-cd) and one in a hot-wet season (CP-hw). The effects of individual treatment factors and their interactions, including two different irrigation methods (furrow - F or drip - D), two irrigation levels (full - I-f or reduced - I-r) and two top dressing N fertiliser types (quick - N-q or slow - N-s release), on water and N distribution in the soil profile, potential water fluxes to the zone below the roots and N losses from the 0-90 cm soil profile were studied. The concentrations of NO3-N and NH4-N in soil water (from suction cups) and soil (from bulk soil samples) tended to be higher at greater depth in the treatments with lower soil water tension, resulting from the interactions between the factors F or D with I-f and N-q, most probably resulting from net downward redistribution of N. The IrNs treatments resulted in longer soil water NO3-N and NH4-N residence time at 30 and 60 cm depth, and throughout the two cropping periods NO3-N was higher in N-s than in Nq treatments. Potential faster downward water flux, and thus water losses and the N leaching risk, was concentrated to the first 50-75 days after sowing in Fl(f)N(q) and Dl(f)N(q) treatments, while it was spread throughout the cropping periods in Fl(f) and Dl(f). Hence, treatments Fl(r)N(q) and Dl(r)N(q) in both CP-cd and CP-hw resulted in the highest estimated N losses from the 0-90 cm soil profile. Based on these results, a combination of D irrigation, I-r irrigation level and N-s fertiliser type should preferably be applied, to avoid the risk of excessive water losses, downward N redistribution and subsequent leaching. (C) 2017 Elsevier B.V. All rights reserved.
|
|
| 3. |
- Chilundo, Mario, et al.
(författare)
-
Response of maize root growth to irrigation and nitrogen management strategies in semi-arid loamy sandy soil
- 2017
-
Ingår i: Field Crops Research. - : Elsevier BV. - 0378-4290 .- 1872-6852. ; 200, s. 143-162
-
Tidskriftsartikel (refereegranskat)abstract
- Strategies to promote dense, deep root systems are important for the efficient use of water and nitrogen fertilisers in subtropical loamy sandy soil. This study assessed the effect of interactions between irrigation method (drip and furrow), irrigation level (full and reduced), and nitrogen fertiliser type (quick release and slow-release) on root growth of maize (Zea mays L.) and the associated effect on grain yield, aboveground biomass and leaf area index. Factorial field experiments on semi-arid loamy sandy soil in Mozambique was carried out in four cropping periods (two in the hot-wet season, two in the cold-dry season). The response to the management factors at three growing stages of coarse (>= 0.7 mm diameter) and fine (<0.7 mm diameter) root density (RD) (two cropping periods) and maximum rooting depth (four cropping periods) were measured in situ by modified profile wall method. The interactions between management factors did not explain the variation in maize RD or maximum rooting depth. However, seasonal variation between the cropping periods affected the distribution of coarse RD. Drip irrigation gave 33-153% higher coarse RD and 26-55% higher fine RD than furrow irrigation in deeper layers (16-64 cm), whereas furrow irrigation gave 21-40% higher coarse RD than drip at a shallow depth (0-16 cm). Irrigation level had little effect on RD, whereas slow-release fertilisation resulted in overall higher RD, aboveground biomass and grain yield than quick-release fertilisation in the cold-dry season. RD or maximum rooting depth showed few significant correlations with grain yield, biomass and leaf area index, respectively, but higher RD generally tended to result in higher yield. Overall, drip irrigation combined with reduced irrigation and slow-release N fertiliser appeared to be the most promising strategy to promote maize rooting and increase yield, especially in the cold-dry season.
|
|
| 4. |
- Gossweiler, Benjamin, et al.
(författare)
-
Impact of Land Use Change on Non-Point Source Pollution in a Semi-Arid Catchment under Rapid Urbanisation in Bolivia
- 2021
-
Ingår i: Water. - : MDPI AG. - 2073-4441. ; 13
-
Tidskriftsartikel (refereegranskat)abstract
- Changes in pollution pressure exerted on the Rocha River in Bolivia from diffuse sources were assessed using potential non-point pollution indexes (PNPI) for 1997 and 2017. PNPI is a simple, low-effort, time- and resource-saving method suitable for data-scarce regions, as it works at catchment level with commonly available geographical data. Land use type (obtained by Landsat imagery classification), runoff (determined by runoff coefficient characterisation) and distance to river network (calculated at perpendicular distance) were each transformed into corresponding indicators to determine their relative importance in generating pollution. Weighted sum, a multi-criteria analysis tool in the GIS environment, was used to combine indicators with weighting values. Different weighting values were assigned to each of the indicators resulting in a set of six equations. The results showed that higher PNPI values corresponded to human settlements with high population density, higher runoff values and shorter distance to river network, while lower PNPI values corresponded to semi-natural land use type, lower runoff coefficient and longer distances to river. PNPI values were positively correlated with measured nitrate and phosphate concentrations at six sub-catchment outlets. The correlation was statistical significant for phosphate in 2017. Maps were produced to identify priority source areas that are more likely to generate pollution, which is important information for future management.
|
|
| 5. |
- Gossweiler, Benjamin, et al.
(författare)
-
Spatial and Temporal Variations in Water Quality and Land Use in a Semi-Arid Catchment in Bolivia
- 2019
-
Ingår i: Water. - : MDPI AG. - 2073-4441. ; 11
-
Tidskriftsartikel (refereegranskat)abstract
- Increasing pressures caused by human activities pose a major threat to water availability and quality worldwide. Water resources have been declining in many catchments during recent decades. This study investigated patterns of river water quality status in a peri-urban/rural catchment in Bolivia in relation to land use during a 26 year period. Satellite images were used to determine changes in land use. To assess water quality, data in the dry season from former studies (1991-2014), complemented with newly collected data (2017), were analysed using the National Sanitation Foundation-Water Quality Index method and the Implicit Pollution Index method. The highest rates of relative increase in land use area were observed for forest, urban, and peri-urban areas, whereas relative decreases were observed for water infiltration zones, bare soil, shrubland, and grassland areas. The water quality indices revealed clear water quality deterioration over time, and from catchment headwaters to outlet. Statistical analyses revealed a significant relationship between decreasing water quality and urban expansion. These results demonstrate the need for an effective control programme, preferably based on water quality index approaches as in the present study and including continuous monitoring of runoff water, mitigation of pollution, and water quality restoration, in order to achieve proper water management and quality.
|
|
| 6. |
- Högberg, Peter, et al.
(författare)
-
Klargöranden om täckdikning
- 2016
-
Ingår i: Upsala nya tidning. - 1104-0173.
-
Tidskriftsartikel (populärvet., debatt m.m.)
|
|
| 7. |
|
|
| 8. |
- Joel, Abraham, et al.
(författare)
-
A tool for assessing the status of drainage ditches and the need for remedial measures
- 2015
-
Ingår i: Acta Agriculturae Scandinavica, Section B - Soil and Plant Science. - : Informa UK Limited. - 0906-4710 .- 1651-1913. ; 65, s. 100-109
-
Tidskriftsartikel (refereegranskat)abstract
- Poor maintenance of drainage systems has been identified as one of Swedish agriculture's weak points, as impaired land drainage can lead to major environmental problems. Drain maintenance work is receiving increasing attention in work conducted within the European Union Water Framework Directive. Moreover, the functionality and maintenance of agricultural ditches will need to be improved to cope with predicted higher pressures on water infrastructure in a future climate. In Sweden, ditch maintenance work is mandatory, but must be carried out with great consideration for the environment. There is currently no simple method available in Sweden for assessing the comprehensive status of open drainage ditches and determining whether remedial measures are needed. This study tested an on-site method, Minnesota Agricultural Ditch Research Assessment for Stability, for evaluating the status of drains and the need for improvements. The study also included an evaluation of physical ditch properties that can be assessed visually on-site and the processes they represent. The results showed that it is viable to evaluate ditch properties such as bank stability, erosion and deposition susceptibility visually on-site. However, more intensive surveys are needed to identify the processes affecting bank stability. For assessing how improvement of drain status affects bank stability and hydraulic properties, Hydrologic Engineering Centre's River Analysis System simulations can be a useful tool when complemented with updated cross-section measurements and existing documentation.
|
|
| 9. |
- Joel, Abraham, et al.
(författare)
-
Effekter av jordbearbetningssystem på vatten-, sediment- och fosfortransport i övre delen av marken vid olika regnintensitet. : slutrapport SLF Projektnummer H0970242
- 2014
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Det finns idag ett stort behov av åtgärder för att minska fosforförluster och transport av sedimenten från land till vatten. Syftet med projektet har varit att öka kunskapen om storleken på vatten-, sediment- och fosfortransporter i övre delen av markprofilen vid olika regnintensiteter. Fältmätningar och laboratoriestudier har genomförts på två lerjordar i försök med olika jordbearbetning. Resultaten visade på en högre avrinning och lägre turbiditet för reducerad jämfört med konventionell bearbetning. Turbiditet och P-koncentrationer i avrinningsvattnet ökade med ökad avrinning. Vid en sänkning av tillflödet tog det lång tid innan turbiditet och P-koncentrationen sjönk i avrinningsvattnet. En platskalibrering är nödvändig om turbiditet ska användas som indikator för P innehåll i avrinningsvatten.
|
|
| 10. |
- Joel, Abraham, et al.
(författare)
-
Mapping suitability of controlled drainage using spatial information of topography, land use and soil type, and validation using detailed mapping, questionnaire and field survey
- 2009
-
Ingår i: Hydrology research. - : IWA Publishing. - 1998-9563 .- 2224-7955 .- 0029-1277. ; 40, s. 406-419
-
Tidskriftsartikel (refereegranskat)abstract
- Controlled drainage has the potential to moderate the variability in temporal water runoff and to control N leaching. The objective of this study was, firstly, to present a feasibility study to identify land that is suitable for installation of controlled drainage in four counties in the coastal areas of southern Sweden and, secondly, to present a methodology to validate land that has been identified as suitable. In the feasibility study, digital data of land use, slope gradient and soil types were individually rated and combined into suitability classes. Of 726,000 ha cultivated land, 21% was classified as very highly or highly suitable, 13% moderately suitable and 6% marginally suitable. The validation study comprised analyses of the study areas from (i) digitized information on existing drainage network associations, provided by regional authorities, (ii) a questionnaire study directed to land users and (iii) physical investigation of soil properties of chosen fields on 82 farms. At least 67% of the land being appointed as being suitable for controlled drainage in the feasibility study was drained or had a drainage demand. There was a high correspondence between the results obtained in the validation study as compared to the feasibility study.
|
|
