| 1. |
- Bai, Z. G., et al.
(författare)
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Proxy global assessment of land degradation
- 2008
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Ingår i: Soil Use and Management. - : Wiley. - 0266-0032 .- 1475-2743. ; 24:3, s. 223-234
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Forskningsöversikt (refereegranskat)abstract
- Land degradation is always With Lis but its causes, extent and severity are contested. We define land degradation as a long-term decline in ecosystem function and productivity, Which may be assessed using lone-term, remotely sensed normalized difference vegetation index (NDVI) data. Deviation from the norm may serve as a proxy assessment of land degradation and improvement - if other factors that may be responsible are taken into account. These other factors include rainfall effects which may be assessed by rain-use efficiency, calculated from NDVI and rainfall. Results from the analysis of the 23-year Global Inventory Modeling and Mapping Studies (GIMMS) NDVI data indicate declining rain-use efficiency-adjusted NDVI on ca. 24% of the global land area with degrading areas mainly in Africa south of the equator, South-East Asia and south China, north-central Australia, the Pampas and swaths of the Siberian and north American taiga; 1.5 billion people live in these areas. The results are very different from previous assessments which compounded what is happening now with historical land degradation. Economic appraisal can be undertaken when land degradation is expressed in terms of net primary productivity and the resultant data allow statistical comparison With other variables to reveal possible drivers.
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| 2. |
- Liu, Jian, et al.
(författare)
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Potential phosphorus leaching from sandy topsoils with different fertilizer histories before and after application of pig slurry
- 2012
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Ingår i: Soil Use and Management. - : Wiley. - 0266-0032 .- 1475-2743. ; 28, s. 457-467
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Tidskriftsartikel (refereegranskat)abstract
- This study investigated the effects of historical long-term and recent single applications of pig slurry on P leaching from intact columns of two sandy topsoils (Mellby and Böslid). The soils had similar physical properties, but different soil P status (ammonium lactate-extractable P; P-AL) and degree of P saturation (DPS-AL). Mellby had P-AL of 220-280 mg kg-1 and DPS-AL of 32-42%, which was higher than for Böslid (P-AL 140 mg kg-1 and DPS 21%). The study investigated the effects since 1983 of four treatments with different fertilizer histories, in summary high (HighSlurryMellby) and low (LowSlurryMellby) rates of pig slurry and mineral P (MinMellby) applications at Mellby and mineral P application at Böslid (MinBöslid). The columns were irrigated in the laboratory five times before and five times after a single application of pig slurry (22 kg P ha-1). Concentrations of dissolved reactive P (DRP), dissolved organic P and total-P (TP) in leachate and loads were significantly higher (p <0.005) from the treatments at Mellby than those at Böslid. TP concentrations followed the trend: HighSlurryMellby (0.57-0.59 mg L-1) > MinMellby (0.41-0.49 mg L-1) > LowSlurryMellby (0.31-0.36 mg L-1) > MinBöslid (0.14-0.15 mg L-1), both before and after the single slurry application. DRP concentrations in leachate were positively correlated with DPS-AL values in the topsoil (R2=0.95, p<0.0001), and increased with greater DPS-AL values after the single slurry application (R2=0.79, p<0.0001). Thus, DPS-AL can be an appropriate indicator of P leaching risk from sandy soils. Moreover, the build-up of soil P due to long-term repeated manure applications seems to be more important for potential P losses than a single manure application.
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| 3. |
- Aronsson, Helena, et al.
(författare)
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Leaching of N, P and glyphosate from two soils after herbicide treatment and incorporation of a ryegrass catch crop
- 2011
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Ingår i: Soil Use and Management. - : Wiley. - 0266-0032 .- 1475-2743. ; 27, s. 54-68
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Tidskriftsartikel (refereegranskat)abstract
- During 2005-2007, studies were carried out in two field experiments in southwest Sweden with separately tile-drained plots on a sandy soil (three replicates) and on a clay soil (two replicates). The overall aim was to determine the effects of different cropping systems with catch crops on losses of N, P and glyphosate. Different times of glyphosate treatment of undersown ryegrass catch crops were examined in combination with soil tillage in November or spring. Drainage water was sampled continuously in proportion to water flow and analysed for N, P and glyphosate. Catch crops were sampled in late autumn and spring and soil was analysed for mineral N content. The yields of following cereal crops were determined. The importance of keeping the catch crop growing as long as possible in the autumn is demonstrated to decrease the risk of N leaching. During a year with high drainage on the sandy soil, annual N leaching was 26 kg/ha higher for plots with a catch crop killed with glyphosate in late September than for plots with a catch crop, while the difference was very small during 1 yr with less drainage. Having the catch crop in place during October was the most important factor, whereas the time of incorporation of a dead catch crop did not influence N leaching from either of the two soils. However, incorporation of a growing catch crop in spring resulted in decreased crop yields, especially on the clay soil. Soil type affected glyphosate leaching to a larger extent than the experimental treatments. Glyphosate was not leached from the sand at all, while it was found at average concentrations of 0.25 mu g/L in drainage water from the clay soil on all sampling occasions. Phosphorus leaching also varied (on average 0.2 and 0.5 kg/ha/yr from the sand and clay, respectively), but was not significantly affected by the different catch crop treatments.
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| 4. |
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| 5. |
- Delin, Sofia
(författare)
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Fertilizer value of nitrogen in hen and broiler manure after application to spring barley using different application timing
- 2011
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Ingår i: Soil Use and Management. - : Wiley. - 0266-0032 .- 1475-2743. ; 27, s. 415-426
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Tidskriftsartikel (refereegranskat)abstract
- The nitrogen (N) fertilizer effect of layer hen and broiler manure applied at different times on spring barley yield was studied in seven Swedish field experiments during 2005-2008. Two experiments had parallel field incubations to study N release after fertilizer application. The effect of total N in manure on N offtake was 30-40% that of mineral N, except in a dry year, when the effect was very low. Although the relative proportions of ammonium N, uric acid N and other N differed between the hen and broiler manure, the effect of total N was similar for both. In field incubations, mineral N decreased from 75 to 60% of total N applied in hen manure, whereas it increased from 20 to 50% in broiler manure, because of net immobilization and release, respectively. The limited fertilizer nitrogen replacement value, corresponding to only 30-40% of total N, could be as a result of ammonia volatilization after rather shallow incorporation with harrow. Net N release from broiler manure lasted for 6-8 weeks after application, after which it generally ceased. In some cases, manure application in early spring gave better yield effects than application at sowing, probably because of better synchronization of the N release with crop N requirements. The residual N effect on the N offtake in crop in the year after manure application was on average 3% of the total N applied, equivalent to a fertilizer replacement value of about 6%.
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| 6. |
- Djodjic, Faruk, et al.
(författare)
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Changes in plant-available and easily soluble phosphorus within 1year after P amendment
- 2013
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Ingår i: Soil Use and Management. - : Wiley. - 0266-0032 .- 1475-2743. ; 29, s. 45-54
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Tidskriftsartikel (refereegranskat)abstract
- Diffuse losses of phosphorus (P) from arable land are often related to soil P and P amendments. We follow the in situ dynamics of plant-available [ammonium lactate/acetic acid (P-AL)] and easily soluble (0.01m CaCl2) P during 1year after fertilizer application at five sites in long-term fertility field experiments in Sweden with three different soil P levels and amendment rates and two different crop rotation systems. Clear differences between soils and P treatments were found. These can to a large extent be explained by the amount of applied of P and soil sorption capacity. The bell curve' indicating the development of plant-available P can be described successfully using Gaussian modelling. Strong correlation between plant-available and easily soluble P as determined by the above-mentioned methods shows that the existing agronomic soil test P can be a good indicator even for easily soluble P, especially if other soil properties such as soil sorption capacity are taken into account. From the management standpoint, small increases in both plant-available and easily soluble P as in the P replacement treatment indicate that such a management strategy may reduce environmental risks as a result of P amendments. Increases in P amendments above the agronomic optimum increased plant-available P for a considerable time after P amendment (24months) to indicate high environmental risk.
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| 7. |
- Eriksson, Ann Kristin, et al.
(författare)
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Phosphorus in Agricultural soils around the Baltic Sea : comparison of laboratory methods as indices for phosphorus leaching to waters
- 2013
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Ingår i: Soil Use and Management. - : Wiley. - 0266-0032 .- 1475-2743. ; 29, s. 5-14
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we investigated the phosphorus (P) content of Baltic soils. In the first set of analyses, 99 soil samples from the Baltic states and Sweden (soil set 1, representing seven different catchments or experimental plots) were analysed for soil P using four extraction methods: ammonium lactate (P-AL) P double lactate (P DL) Mehlich 3 (PM3) and carbonate (P Olsen) (r=0.85-0.97) In abolute values,results from PM3, PDL and P Olsen gave means of 71, 61 and 20%, respectively, of the values from the PAL extraction method. Significantly different relationships were found between P soil concentrations and pH of the extract. In addition, soil pH and organic matter content were found to be of importance. Secondly, we tested 110 soil samples (soil set 2) from five different Swedish monitoring fields with clay soils where PAL clearly correlated with soil P extracted in calcium chloride (PCaCl2) (R= 0.95). Values of a single-point phosphorus sorption index (PSI) correlated with the aluminium concentration (AlAL) tests with different extraction agents - calcium chloride (PCaCL2w) water (Pw), POlsen or PAL - correlated with the mean annual flow-weighted concentration (1999–2010) of dissolved reactive P (DRP) in drainage water. Neither was there any clear relationship between DRP concentration in drainage water and these tests combined with PSI or with other sorption indices including extracted Al and iron (Fe). However, DRP was related to the clay content of the topsoil (r = 0.91, P < 0.05).
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| 8. |
- Keller, Thomas
(författare)
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Rules of thumb for minimizing subsoil compaction
- 2012
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Ingår i: Soil Use and Management. - : Wiley. - 0266-0032 .- 1475-2743. ; 28, s. 378-393
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Tidskriftsartikel (refereegranskat)abstract
- Subsoil compaction is persistent and can affect important soil functions including soil productivity. The aim of this study was to develop recommendations on how to avoid subsoil compaction for soils exposed to traffic by machinery at field capacity. We measured the vertical stress in the tyresoil contact area for two traction tyres at ca. 30- and 60-kN wheel loads on a loamy sand at field capacity. Data on resulting stress distributions were combined with those from the literature for five implement tyres tested at a range of inflation pressures and wheel loads. The vertical stress in the soil profile was then predicted using the Sohne model for all tests in the combined data set. The predicted stress at 20 cm depth correlated with the maximum stress in the contact area, tyre inflation pressure, tyresoil contact area and mean ground pressure. At 100 cm depth, the predicted vertical stress was primarily determined by wheel load, but an effect of the other factors was also detected. Based on published recommendations for allowable stresses in the soil profile, we propose the 50-50 rule: At water contents around field capacity, traffic on agricultural soil should not exert vertical stresses in excess of 50-kPa at depths >50 cm. Our combined data provide the basis for the 8-8 rule: The depth of the 50- kPa stress isobar increases by 8 cm for each additional tonne increase in wheel load and by 8 cm for each doubling of the tyre inflation pressure. We suggest that farmers use this simple rule for evaluating the sustainability of any planned traffic over moist soil.
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| 9. |
- Kirchmann, Holger
(författare)
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Land-use effects on the distribution of soil organic carbon within particle-size fractions of volcanic soils in the Transmexican Volcanic Belt (Mexico)
- 2011
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Ingår i: Soil Use and Management. - : Wiley. - 0266-0032 .- 1475-2743. ; 27, s. 186-194
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to determine the effect of land-use and forest cover depletion on the distribution of soil organic carbon (SOC) within particle-size fractions in a volcanic soil. Emphasis was given to the thermal properties of soils. Six representative sites in Mexico were selected in an area dominated by Andosols: a grassland site, four forested sites with different levels of degradation and an agricultural site. Soils were fractionated using ultrasonic energy until complete dispersion was achieved. The particle-size fractions were coarse sand, fine sand, silt, clay and particulate organic matter from the coarse sand sized fraction (POM-CS) and fine sand (POM-FS). Soil organic carbon decreased by 70% after forest conversion to cropland and long-term cultivation; forest cover loss resulted in a decrease in SOC of up to 60%. The grassland soil contained 45% more SOC than the cropland one. Soil organic carbon was mainly associated with the silt-size fraction; the most sensitive fractions to land-use change and forest cover depletion were POM followed by SOC associated with the silt and clay-sized fractions. Particulate organic matter can be used as an early indicator of SOC loss. The C lost from the clay and silt-sized fractions was thermally labile; therefore, the SOC stored in the more degraded forest soils was more recalcitrant (thermally resistant). Only the transformation of forest to agricultural land produced a similar loss of thermally stable C associated with the silt-sized fraction.
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| 10. |
- Mattsson, Lennart
(författare)
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Grain yield and crop N offtake in response to residual fertilizer N in long-term field experiments
- 2010
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Ingår i: Soil Use and Management. - : Wiley. - 0266-0032 .- 1475-2743. ; 26, s. 455-464
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Tidskriftsartikel (refereegranskat)abstract
- Organic inputs [e.g. animal manure (AM) and plant residues] contribute directly to the soil organic N pool, whereas mineral N fertilizer contributes indirectly by increasing the return of the crop residues and by microbial immobilization. To evaluate the residual effect of N treatments established in four long-term (> 35 yr) field experiments, we measured the response of barley (grain yield and N offtake at crop maturity) to six rates (0, 30, 60, 90, 120 and 150 kg N/ha) of mineral fertilizer N (N(new)) applied in subplots replacing the customary long-term plot treatments of fertilizer inputs (N(prev)). Rates of N(prev) above 50-100 kg N/ha had no consistent effect on the soil N content, but this was up to 20% greater than that in unfertilized treatments. Long-term unfertilized plots should not be used as control to test the residual value of N in modern agriculture with large production potentials. Although the effect of mineral N(prev) on grain yield and N offtake could be substituted by N(new) within a range of previous inputs, the value of N(prev) was not eliminated irrespective of N(new) rate. Provided a sufficient supply of plant nutrients other than N, the use-efficiency of N(new) did not change significantly with previous mineral N fertilizer rate. The residual effect of mineral N fertilizer was negligible compared with the residual effect of N from AM and catch crop residues.
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