Do earthworms affect phosphorus availability to grass? A pot experiment.
Vos, M.J. ; Ros, M.B.H. ; Koopmans, G.F. ; Groenigen, J.W. van - \ 2014
Soil Biology and Biochemistry 79 (2014). - ISSN 0038-0717 - p. 34 - 42.
pontoscolex-corethrurus glossoscolecidae - organic-matter - phosphate adsorption - colloidal phosphorus - lumbricus-terrestris - geophagous earthworm - soil-phosphorus - tropical soil - plant-growth - casts
The largest part of phosphorus (P) in soil is bound by the soil solid phase; its release to the soil solution therefore often does not meet the demand of plants. Since global P fertilizer reserves are declining, it becomes increasingly important to better utilize soil P. We tested whether earthworm activity can increase P availability to grass (Lolium perenne L.) in a 75-day greenhouse pot experiment in a soil with low P availability. The full factorial design included two factors: P fertilization (control without P; phytate; and inorganic P) and earthworm population (control without earthworms; Lumbricus rubellus Hoffmeister, Lr; Aporrectodea caliginosa Savigny, Ac; and Lumbricus terrestris L., Lt). At four times during the experiment, aboveground plant growth and P uptake were determined. In a separate incubation experiment, earthworm casts and bulk soil were analyzed for inorganic and organic P in water extracts. We observed higher levels of dissolved P pools (p <0.001) in the water extracts of earthworm casts compared to those of the bulk soil. The magnitude of the difference differed between earthworm species, with the largest levels for Lr: from
Key role of China and its agriculture in global sustainable phosphorus management
Sattari, S.Z. ; Ittersum, M.K. van; Giller, K.E. ; Zhang, F. ; Bouwman, A.F. - \ 2014
Environmental Research Letters 9 (2014)5. - ISSN 1748-9326 - 8 p.
environmental impacts - soil-phosphorus - crop yield - food-chain - fertilizer - nitrogen - perspective - scarcity - balances - industry
Growing global demand for food leads to increased pressure on phosphorus (P), a finite and dwindling resource. China is the largest producer and consumer of P fertilizer in the world. A mass balance analysis of historical P use on China's arable land shows that P input substantially exceeds crop P uptake leading to the accumulation of residual soil P. A Dynamic P Pool Simulator (DPPS) model is applied to estimate future P demand in China's arable land. Our simulations show that more sustainable use of P accounting for the residual P can save ca. 20% of the P fertilizer needed until 2050 in China relative to the Rio + 20 Trend scenario. This saving would be equivalent to half of the P required in Africa or sufficient for Western Europe to achieve target crop P uptake in 2050.
Diffuse Phosphorus Models in the United States and Europe: Their Usages, Scales, and Uncertainties
Radcliffe, D.E. ; Freer, J. ; Schoumans, O.F. - \ 2009
Journal of Environmental Quality 38 (2009)5. - ISSN 0047-2425 - p. 1956 - 1967.
intensively farmed grasslands - stream water phosphorus - surface-applied manures - agricultural watersheds - soil-phosphorus - spatial variability - dynamic topmodel - risk-assessment - catchments - river
Today there are many well-established computer models that are being used at different spatial and temporal scales to describe water, sediment, and P transport from diffuse sources. In this review, we describe how diffuse P models are commonly being used in the United States and Europe, the challenge presented by different temporal and spatial scales, and the uncertainty in model predictions. In the United States for water bodies that do not meet water quality standards, a total maximum daily load (TMDL) of the Pollutant of concern must be set that will restore water quality and a plan implemented to reduce the pollutant load to meet the TMDL. Models are used to estimate the current maximum daily and annual average load, to estimate the contribution from different nonpoint sources, and to develop scenarios for achieving the TMDL target. In Europe, the EC-Water Framework Directive is the driving force to improve water quality and models are playing a similar role to that in the United States, but the models being used are not the same. European models are more likely to take into account leaching of P and the identification of critical source areas. Scaling up to the watershed scale has led to overparameterized models that cannot be used to test hypotheses regarding nonpoint sources of P or transport processes using the monitoring data that is typically available. There is a need for more parsimonious models and monitoring data that takes advantage of the technological improvements that allow nearly continuous sampling for P and sediment. Tools for measuring model uncertainty must become an integral part of models and be readily available for model users.
Impacts of agricultural phosphorus use in catchments on shallow lake water quality: about buffers, time delays and equilibria
Schippers, P. ; Weerd, H. van de; Klein, J.J.M. de; Jong, B. de; Scheffer, M. - \ 2006
Science of the Total Environment 369 (2006)1-3. - ISSN 0048-9697 - p. 280 - 294.
soil-phosphorus - surface waters - sediment phosphorus - thame catchment - management - eutrophication - nutrient - nitrogen - runoff - land
Phosphorus (P) losses caused by intensive agriculture are known to have potentially large negative effects on the water quality of lakes. However, due to the buffering capacity of soils and lake ecosystems, such effects may appear long after intensive agriculture started. Here we present the study of a coupled shallow lake catchment model, which allows a glimpse of the magnitude of these buffer-related time delays. Results show that the buffering capacity of the lake water was negligible whereas buffering in the lake sediment postponed the final lake equilibrium for several decades. The surface soil layer in contact with runoff water was accountable for a delay of 550 years. The most important buffer, however, was the percolation soil layer that may cause a delay of 150-1700 years depending on agricultural P surplus levels. Although the buffers could postpone final lake equilibria for a considerable time, current and target agricultural surplus levels eventually led to very turbid conditions with total P concentrations of 2.0 and 0.6 mg L-1 respectively. To secure permanent clear water states the current agricultural P surplus of 15 kg P ha(-1) yr(-1) should drop to 0.7 kg P ha(-1) yr(-1). We present several simple equations that can be used to estimate the sustainable P surplus levels, buffer related time delays and equilibrium P concentrations in other catchment-lake systems. (c) 2006 Elsevier B.V. All rights reserved.
Mapping hydrological pathways of phosphorus transfer in apparently homogeneous landscapes using a high-resolution DEM
Sonneveld, M.P.W. ; Schoorl, J.M. ; Veldkamp, A. - \ 2006
Geoderma 133 (2006)1-2. - ISSN 0016-7061 - p. 32 - 42.
soil-phosphorus - management-practices - agricultural land - surface waters - losses - netherlands - nitrogen - grassland - quality - runoff
Agriculture is a significant contributor to the diffuse loading of phophorus (P) in fresh water systems. At the landscape level, source areas and targeted surface waters are connected through different hydrological pathways. One of these pathways, P removal through surface runoff, may increase in relative importance when storm events occur and in wet seasons. With Digital Elevation Models (DEMs) it is possible to identify dominant surface pathways in the landscape although resolution of available DEMs is often not detailed enough for areas with low relief or for more detailed landscape-field studies. New high-resolution DEMs that do combine a high resolution with substantial spatial coverage provide the opportunity to develop site-specific management alternatives for sensitive or critical source areas at the landscape level. The objective of this paper is to map hydrological pathways of P for a relatively flat glacial till landscape in the Northern part of the Netherlands and to compare two strategies (A and B) in this landscape for minimizing P loading of surface waters following different scenarios. Strategy A assumes equal lowering of phosphate input rates for all fields and strategy B takes into account the relative sensitivity of fields for removal through overland flow. Available soil data, which did not allow to geo-reference individual fields, showed high soil P levels in about 5% of all fields. Data on field inputs of total phosphate (P2O5) were available for 29 farms and showed that fertilized fields received on average 124 kg ha¿ 1 in the year 2000. Transfer potential of each individual field was evaluated on the basis of two characteristics in a 5 × 5 m resolution DEM: 1) the degree of internal drainage through re-distribution and 2) the degree of external drainage, which indicates the overland flow potential. Almost every field was characterised by sinks (98%) and external drainage into along-field ditches (99%). In addition, almost half of the fields showed drainage directly into surface waters (47%). Applying a classification scheme to rank the sensitivity for losses through overland flow provided a framework to distribute catchment inputs of phosphate at field level (strategy B). Comparing the strategy of distributed phosphate inputs (B) with generic phosphate inputs (A) showed that catchment input-to-output ratios are higher for strategy B for three out of four of the applied scenarios.
Risk assessment methodologies for predicting phosphorus losses
Schoumans, O.F. ; Chardon, W.J. - \ 2003
Journal of Plant Nutrition and Soil Science 166 (2003)4. - ISSN 1436-8730 - p. 403 - 408.
organic phosphorus - soil-phosphorus - netherlands - phosphate - grassland
Risk assessment parameters are needed to assess the contribution of phosphorus (P) losses from soil to surface water, and the effectiveness of nutrient and land management strategies for the reduction of P loss. These parameters need to take into account the large temporal and spatial variation in P transfer from individual fields arising from (a) changing but predictable factors such as land use, soil P status, P application rates, forms and ways of fertilization and spreading, (b) predictable but inherent factors such as soil type, soil dispersivity, slope and hydrological routing, and (c) unpredictable weather factors such as rainfall amount and intensity. In most situations, water transport is the driving force of P loss from agricultural land to surface water. Therefore, the hydrological pathways determine to a large extent the relevance of these different factors. Over the last decade several soil P tests have been proposed as a first step to link field conditions to risk of P loss. The major reason is that these soil P tests are also meaningful in discussions with farmers. Recently, more complex P loss risk parameters have been derived based on different approaches. However, the scope and purposes of these P loss risk parameters vary remarkably. Finally, there is a need to evaluate the usefulness of new P tests that can be used as an indicator of P loss risk, e.g. in relation to monitoring purposes. The implementation of the EU Water Framework Directive will increase this need. In this paper, the practicable applicability of P parameters for risk assessment is discussed in relation to purpose, scale (from field, farm to catchment), effectiveness, sensibility etc. Furthermore, a conceptual framework for P indicators is presented and evaluated, based on the outcome of the presentations and the discussions in Zurich.
Selective extraction of labile phosphorus using dialysis membrane tubes filled with hydrous iron hydroxide
Koopmans, G.F. ; Zeeuw, M.E. van der; Chardon, W.J. ; Dolfing, J. - \ 2001
Soil Science 166 (2001)7. - ISSN 0038-075X - p. 475 - 483.
soil-phosphorus - phosphate - netherlands - release - losses - runoff - oxide - water
Leaching of phosphorus (P) can be a serious problem in P-enriched sandy soils. Techniques that decrease the P content of such soils have been proposed as possible remediation methods. In this study, we determined the effect of P removal from two P-rich sandy soils on extractability of soil P in a laboratory experiment. We created soil samples in increasing stages of P depletion by using a sink method, which consists of a dialysis membrane tube filled with hydrous Fe-(hydr)oxide (DMT-HFO). Total amounts of P removed were relatively small compared with the high initial ammonium-oxalate extractable P contents. However, amounts of water and CaCl2 extractable P in the depleted soil samples decreased by 57 to 80%, on average, for both soils. On the other hand, the ammonium-oxalate-based P saturation index decreased by only 11%. Apparently, labile P forms were readily removed, which means that depletion by the DMT-HFO was selective. Our results suggest that remediation methods that remove a small but selective amount of P from soil may cause a significant decrease of the soil potential to release dissolved P. We also used our results to evaluate the suitability of the DMT-HFO to act as an infinite sink for P. For that, the desorption results were described with a simple kinetic Langmuir equation. Errors of kd (desorption constant) and Q0 (amount of P initially adsorbed) were calculated. Although the model fit was good for both soils (r2=0.98*** and 0.99***), errors in Q0 and kd were large. Therefore, the DMT-HFO method could not be used to determine the desorption constants of our soils. Values of kd and Q0 obtained by this method should not be used in modeling studies