Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

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    We will mail you new results for this query: keywords==Phosphorus
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Machine learning to realize phosphate equilibrium at field level in dairy farming
Mollenhorst, H. ; Haan, M.H.A. De; Oenema, J. ; Hoving-Bolink, A.H. ; Veerkamp, R.F. ; Kamphuis, C. - \ 2019
In: Precision Livestock Farming 2019. - Teagasc (Precision Livestock Farming 2019 - Papers Presented at the 9th European Conference on Precision Livestock Farming, ECPLF 2019 ) - ISBN 9781841706542 - p. 41 - 44.
Boosting - Crop yield - Machine learning - Manure - Phosphorus - Regression tree

An important factor in circular agriculture is efficient application of animal manure. Therefore, input and output of nutrients, like phosphorus (P), need to be balanced. Currently, manure application is regulated with rather fixed P application norms as a generic translation of P yields of grassland and maize. Predicting P yields based on field specific, historical data could be an important step to better balance P input and output. This study's objective was to predict P yields based on field and weather data, using machine learning. The dataset contained 640 records of yearly crop yields per field between 1993-2016 with information on P input and output, irrigation, and soil status at field level as well as local weather data. Generalized boosted regression (GBR) was used to predict P yields for the last five years based on information from all previous years. Model performance was evaluated per year as well as together by plotting observed versus predicted values of all five years in one plot. This final plot was compared to a plot with the currently used generic application norms. Model performance per year showed that GBR could predict the trend from low to high rather well (correlations of ~0.8). Results of the five years together showed that GBR performance was better than the generic application norms (correlation 0.68 vs 0.59; RMSE 7.3 vs 8.2). In conclusion, GBR contributed to defining more flexible P application norms with the aim to realize a phosphate equilibrium.

Large variations in readily-available phosphorus in casts of eight earthworm species are linked to cast properties
Vos, Hannah M.J. ; Koopmans, Gerwin F. ; Beezemer, Lieke ; Goede, Ron G.M. de; Hiemstra, Tjisse ; Groenigen, Jan Willem van - \ 2019
Soil Biology and Biochemistry 138 (2019). - ISSN 0038-0717
Community composition - Earthworms - Phosphorus - Physico-chemical cast properties

Phosphorus (P) is an important nutrient for plant growth. However, P is often poorly available for uptake by roots because it strongly adsorbs to the soil mineral phase. Recent research shows that earthworms can temporally and locally increase P availability to plants. However, the pathways through which they do so are not fully understood, and it remains unclear to what extent this capacity varies among earthworm species. Here we study the variation among earthworm species with respect to readily-available P in casts as well as other physico-chemical cast properties, in a greenhouse pot experiment using a soil with a low P status. The earthworms belong to eight commonly occurring earthworm species in the Netherlands: two epigeic species (a mixture of the compost earthworms Dendrobaena veneta/Eisenia fetida; Lumbricus rubellus); four endogeic species (Allolobophora chlorotica, Aporrectodea caliginosa, Aporrectodea rosea, Octolasion lacteum); and two anecic species (Aporrectodea longa; Lumbricus terrestris). For all species, the pH in water extracts of earthworm cast (pH = 7.4–8.2) was significantly higher (p < 0.001) than for the control bulk soil (pH = 6.6) and differed significantly (p = 0.003) among earthworm species. Similarly, the dissolved organic carbon (DOC) concentration in the same water extracts was an order of magnitude higher in earthworm cast compared to the control bulk soil and varied among species (p < 0.001). The size of the total pool of reversibly adsorbed P in earthworm cast was greater than in the control bulk soil, but no significant differences were found among earthworm species. Differences among species were present for the readily-available P pools extracted from casts, including P-Olsen and water-extractable ortho-P. Water-extractable ortho-P concentrations were much higher in the casts of all species as compared to the control bulk soil (0.9–6.8 vs 0.06 mg l−1 or to 9.0–68 vs 0.6 mg kg−1). Highest ortho-P levels were measured in L. rubellus casts and the lowest in casts of A. chlorotica. A positive correlation between the concentrations of DOC and ortho-P was observed (R2 = 0.72, p < 0.001). The observed variation in all measured physico-chemical cast properties could not be explained by conventional ecological earthworm classifications. Our results show that the nature and magnitude of earthworm-induced increased P availability differs dramatically among earthworm species. This strongly suggests that, apart from its size, species composition of the earthworm community is key to optimizing P availability to plants.

Fertile cities: Nutrient management practices in urban agriculture
Wielemaker, Rosanne ; Oenema, Oene ; Zeeman, Grietje ; Weijma, Jan - \ 2019
Science of the Total Environment 668 (2019). - ISSN 0048-9697 - p. 1277 - 1288.
Fertilizer use - Nitrogen - Organic matter - Phosphorus - Potassium - Urban farming

Cities are increasingly targeted as centers for sustainable development and innovation of food systems. Urban agriculture (UA) is advocated by some as a multi-faceted approach to help achieve urban sustainability goals as it provides possible social, economic and environmental benefits. The role of UA in restoring resource cycles receives increasing attention, especially with regard to assimilating urban waste. However, there is little information on how nutrients are managed in UA in industrialized countries. To examine nutrient management in UA, data was collected from a total of 25 ground-based UA initiatives in the Netherlands on i) preferences for types of fertilizers, and ii) quantity and quality of fertilizers used including nutrient composition and organic matter content. The main inputs at urban farms were compost and manure, high in organic matter content. The total nutrient inputs were compared to nutrient demand, based on crop nutrient uptake, in order to determine nutrient balances. Results show that mean nutrient inputs exceeded mean crop demand by roughly 450% for total nitrogen, 600% for phosphorus and 250% for potassium. Mean inputs for plant-available nitrogen were comparable to crop uptake values. The surpluses, particularly for phosphorus, are higher than fertilizer application limits used for conventional farming in The Netherlands. While nutrient input calculations were subject to several uncertainties, e.g., due to lack of accuracy of the data supplied by the farmers, results show a salient indication of over-fertilization and thus a suboptimal nutrient use. If UA continues to expand across cities these observed nutrient surpluses may pose a risk for local surface waters and groundwater as well as soil quality. The need to improve nutrient management in UA is evident. Soil tests, harvest logging and book keeping of nutrient inputs would improve data quality and may help balance nutrient inputs with nutrient outputs.

Soil bacterial community structure and functional responses across a long-term mineral phosphorus (Pi) fertilisation gradient differ in grazed and cut grasslands
Randall, Kate ; Brennan, Fiona ; Clipson, Nicholas ; Creamer, Rachel ; Griffiths, Bryan ; Storey, Sean ; Doyle, Evelyn - \ 2019
Applied Soil Ecology 138 (2019). - ISSN 0929-1393 - p. 134 - 143.
Agricultural management - Bacteria - Grassland - Phosphorus - Soil
Grasslands form a significant proportion of land used across the globe and future management is important. The objective of this study was to compare the long-term impact of inorganic phosphorus (Pi) fertilisation rates (P0, P15 and P30 ha−1 yr−1) under two grass management trials (grazed vs. cut and removed) on soil physicochemical properties, microbial biomass, phosphomonoesterase activity, bacterial community structure and abundance of a phosphorus (P) mineralising gene (phoD). Under grazing, microbial biomass and soil phosphorus concentrations (total and Pi) generally increased with Pi fertilisation rate, accompanied by significant differences in bacterial community structure between unfertilised (P0) and P30 soil. At the cut and removed site, although Pi was significantly greater in P30 soil, P concentrations (total and Pi) did not increase to the same extent as for grazing, with microbial biomass and bacterial community structures unresponsive to Pi fertilisation. Despite differences in soil P concentrations (total and Pi) and microbial biomass between sites, the abundance of bacterial phoD increased with increasing soil Pi across both sites, while phosphomonoesterase activity decreased. Amplicon sequencing revealed Acidobacteria were the dominant bacterial phylum across both grasslands, but significant differences in relative abundances of bacterial genera were detected at the grazed site only. The bacterial genera Gp6 and Gp16 increased significantly with Pi fertilisation under grazing. Conversely, Bradyrhizobium as well as unclassified genus-type groups belonging to Actinobacteria and Acidimicrobiales significantly decreased with Pi fertilisation, suggesting potential roles in P mobilisation when soil Pi concentrations are low. This study highlights the importance of long-term Pi fertilisation rates and aboveground vegetation removal in shaping soil bacterial community structure and microbial biomass, which in turn may impact soil fertility and plant productivity within agricultural soils.
Recycling nutrients contained in human excreta to agriculture: Pathways, processes, and products
Harder, Robin ; Wielemaker, Rosanne ; Larsen, Tove A. ; Zeeman, Grietje ; Öberg, Gunilla - \ 2019
Critical Reviews in Environmental Science and Technology 49 (2019)8. - ISSN 1064-3389 - p. 695 - 743.
blackwater - carbon - feces - fertilizer - nitrogen - organic matter - Phosphorus - potassium - recovery - resource-oriented sanitation - sewage - soil amendment - source-separation - urine - wastewater

The need for better nutrient management has spurred efforts towards more comprehensive recycling of nutrients contained in human excreta to agriculture. Research in this direction has intensified throughout the past years, continuously unfolding new knowledge and technologies. The present review aspires to provide a systematic synthesis of the field by providing an accessible overview of terminology, recovery pathways and treatment options, and products rendered by treatment. Our synthesis suggests that, rather than focusing on a specific recovery pathway or product and on a limited set of nutrients, there is scope for exploring how to maximize nutrient recovery by combining individual pathways and products and including a broader range of nutrients. To this end, finding ways to more effectively share and consolidate knowledge and information on recovery pathways and products would be beneficial. The present review aims to provide a template that aims to facilitate designing human excreta management for maximum nutrient recovery, and that can serve as foundation for organizing and categorizing information for more effective sharing and consolidation.

Agricultural nitrogen and phosphorus emissions to water and their mitigation options in the Haihe Basin, China
Zhao, Zhanqing ; Qin, Wei ; Bai, Zhaohai ; Ma, Lin - \ 2019
Agricultural Water Management 212 (2019). - ISSN 0378-3774 - p. 262 - 272.
Crop-livestock system - Haihe Basin - Nitrogen - NUFER - Phosphorus - Water pollution

Agricultural nitrogen (N) and phosphorus (P) emissions to water bodies remain largely unknown in China, mainly due to the lack of reliable data sources and quantification tools. In this study, we constructed a grid-based NUFER (NUtrient Flow in food chains, Environment and Resources use) model in order to quantify a high-resolution agricultural N and P emissions to water bodies in Haihe Basin in 2012, based on data collected from county-level statistics, farm interview, and spatial data of topography, climate, soil texture, and land use. We also explored the mitigation strategies in 2030 via scenario analysis. The results showed that total agricultural N emission to water bodies in Haihe Basin was 1079 Gg N in 2012, of which cropland contributed 54%; total agricultural P emission to water bodies was 208 Gg P, livestock contributed 78%. There were large spatial variations in agricultural N and P emissions. Overall, the plain areas accounted for around 80% of the total agricultural N and P emissions to water in 2012. The highest N and P emission intensities were 10 t N km−2 and 2 t P km−2, respectively. N and P emissions were significantly related to anthropogenic factors (such as the livestock density and cropland) in the plain areas; whereas in mountainous areas, both anthropogenic and natural factors (e.g., slope deviation and soil texture) significantly affected N and P emissions. Our scenario analysis suggests that agricultural N and P emissions can be reduced by up to 45% and 77%, respectively for N and P in 2030, via improved agricultural and environmental policies, technologies and managements. The prohibition of direct animal manure discharge to the water system seems to be the most effective measure to mitigate the emissions. Our study provided a high-resolution agricultural N and P emissions to the water bodies of Haihe Basin and identified the most effective options to reduce these emissions in highly intensified agricultural areas.

Testing for complementarity in phosphorus resource use by mixtures of crop species
Li, Chunjie ; Kuijper, T.W.M. ; Werf, Wopke van der; Zhang, Junling ; Li, Haigang ; Zhang, Fusuo ; Hoffland, Ellis - \ 2019
Plant and Soil 439 (2019)1-2. - ISSN 0032-079X - p. 163 - 177.
Competition - Complementarity - Intercrop - Phosphorus - Resource partitioning

Aims: The phosphorus (P) resource partitioning hypothesis assumes that dissimilarity in P acquisition traits among plant species leads to enhanced P uptake by crop combinations compared with their sole crops. We developed and implemented a test for this hypothesis. Methods: Two pot experiments were conducted with quartz sands. In Experiment 1, the ability of the crop species to acquire P from sparingly soluble sources (Ca phosphate (CaP), phytate (PhyP) and P-coated Fe (hydr)oxide (FeP)) was tested. In accordance with the species performances in Experiment 1, combinations of millet/chickpea and cabbage/faba bean (which have dissimilar P acquisition traits) and wheat/maize (which have similar traits) were selected for Experiment 2. The biomass production and P uptake were compared between the sole crops and species combinations as well as between the single and mixed P sources. Results: A dissimilarity in P acquisition traits enhanced P uptake by millet/chickpea on CaP/PhyP (as expected) but not by cabbage/faba bean on FeP/PhyP. Despite their similar P acquisition traits, we found enhanced P uptake by wheat/maize on CaP/PhyP. Conclusions: Because of complicating factors such as unstable P acquisition traits and competitive inequality between species, the conditions under which the P resource partitioning hypothesis can be tested are limited. This challenge complicates designing for complementarity in soil P pools by intercrops.

Nutrient use efficiencies, losses, and abatement strategies for peri-urban dairy production systems
Wei, S. ; Bai, Z.H. ; Qin, W. ; Wu, Z.G. ; Jiang, R.F. ; Ma, L. - \ 2018
Journal of Environmental Management 228 (2018). - ISSN 0301-4797 - p. 232 - 238.
Dairy farms - Manure management - Nitrogen - NUFER model - Nutrient cycling - Phosphorus

Manure management is an important aspect of urban livestock production that has a profound impact on metropolitan living. Data were collected from 28 dairy farms in peri-urban Beijing and analysed to determine farm nitrogen and phosphorus flows and costs associated with various manure management options to reduce nutrient losses. Dairy production in peri-urban Beijing was characterized by its use of high protein diets (16.3–17.0% crude protein), high reliance on imported feeds (92–98%), and low manure recycling (3.0–10.8%). Farms of 900–2000 cattle showed lower use efficiencies than farms of <900 cattle. Costs of manure handling ranged from 0.1 to 1.0 Yuan kg−1 milk. Among various manure treatment options, biogas digesters with aerobic lagoons had the lowest N losses and costs, justifying their investments. In conclusion, peri-urban dairy production systems were contrasting with traditional systems and within their own systems in nutrient use efficiency and losses, which was mainly decided by their farm size. To improve the nutrient use efficiencies and reduce losses, farmers and managers of peri-urban dairy production system should have a full awareness of different feed intake and manure management.

Plant species occurrence patterns in Eurasian grasslands reflect adaptation to nutrient ratios
Roeling, Ineke S. ; Ozinga, Wim A. ; Dijk, Jerry van; Eppinga, Maarten B. ; Wassen, Martin J. - \ 2018
Oecologia 186 (2018)4. - ISSN 0029-8549 - p. 1055 - 1067.
Niche - Nitrogen - Phosphorus - Species composition - Stoichiometry
Previous studies of Eurasian grasslands have suggested that nutrient ratios, rather than absolute nutrient availabilities and associated productivity, may be driving plant species richness patterns. However, the underlying assumption that species occupy distinct niches along nutrient ratio gradients remains to be tested. We analysed plant community composition and nutrient status of 644 Eurasian wet grassland plots. The importance of nutrient ratios driving variation in species composition was analysed using ordination methods (DCA and CCA). Subsequently, we assessed the niche position and width along the most important nutrient ratio gradient [N:P] for each species. We found that the N:P ratio explained part of the variation in species composition independent from conventional explanatory variables. The N:P ratio explained less variation than soil moisture or pH, but more than productivity or the availability of N and P separately, highlighting its importance for grassland species composition. Species occupied distinct niches along the N:P gradient, and species’ niche widths decreased toward extreme nutrient limitation. After correcting for niche position, there was no overall difference in niche width between endangered and non-endangered species. Surprisingly, endangered species with niche optima at the extreme P-limited end of the gradient had broader niches than their non-endangered counterparts. As species occupied distinct niches along a nutrient ratio gradient, future grassland conservation efforts may benefit from targeting changes in nutrient ratios, i.e. the balance between N and P, rather than only focussing on a general reduction in nutrient availability. However, what management interventions can be used for this purpose remains unclear.
Relationships between leaf mass per area and nutrient concentrations in 98 Mediterranean woody species are determined by phylogeny, habitat and leaf habit
Riva, Enrique G. de la; Villar, Rafael ; Pérez-Ramos, Ignacio M. ; Quero, José Luis ; Matías, Luis ; Poorter, Lourens ; Marañón, Teodoro - \ 2018
Trees-Structure and Function 32 (2018)2. - ISSN 0931-1890 - p. 497 - 510.
Functional traits - Leaf economics spectrum - Nitrogen - Phosphorus - Phylogenetic independent contrast (PIC) - Stoichiometry
Key message: This study reinforces the existence of the leaf economics spectrum in Mediterranean woody species, and demonstrates the strong influence of phylogeny, leaf habit and environmental context as main drivers of variability in structural and nutrient traits of leaves. Abstract: Leaf structural and nutrient traits are key attributes of plant ecological strategies, as these traits are related to resource-use strategies and plant growth. However, leaf structure and nutrient composition can vary among different habitats, leaf habits or phylogenetic groups. In this study, we measured 13 leaf traits (one structural—leaf mass per area, LMA—and 12 nutrient traits) in 98 Mediterranean woody species growing over a wide range of environmental conditions, with the final aim of discerning the main causes of leaf trait variability. The variance decomposition results show that phylogeny, leaf habit and habitat type affected in several ways the structural and nutrient traits studied. Leaf nutrient concentrations are strongly positively correlated amongst themselves, and negatively correlated with LMA, in accordance with the “leaf economics spectrum”. We found that leaf habit and phylogeny were important causes of variation in LMA and in a broad number of leaf nutrients (i.e., C, N, Mg, S, K), while other micronutrients seemed to be more dependent on the environment (i.e., Cu and Mn). In summary, our study reinforces the existence of the leaf economics spectrum in a broad pool of Mediterranean woody species, and demonstrates the strong influence of phylogeny, leaf habit and environmental context as the main drivers of variability in some leaf structural and nutrient traits.
The role of complementarity and selection effects in P acquisition of intercropping systems
Li, Xiao Fei ; Wang, Cheng Bao ; Zhang, Wei Ping ; Wang, Le Hua ; Tian, Xiu Li ; Yang, Si Cun ; Jiang, Wan Li ; Ruijven, Jasper van; Li, Long - \ 2018
Plant and Soil 422 (2018)1-2. - ISSN 0032-079X - p. 479 - 493.
Crop diversity - Interspecific facilitation - Niche differentiation - Overyielding - Phosphorus
Background and aims: Enhanced crop productivity by intercropping is commonly assumed to be driven by resource complementarity. However, relatively few studies have directly measured resource acquisition to assess potential mechanisms underlying enhanced performance of intercropping. Methods: A long-term field experiment with three P application rates (0, 40, 80 kg P ha−1 yr.−1) and four maize-based intercropping systems was used to assess P acquisition and P fertilizer recovery efficiency (PRE) for three consecutive years. To identify underlying mechanisms, the additive partitioning method was applied to determine complementarity (CE) and selection effects (SE) in P acquisition of intercropping. Results: Average P acquisition increased by 28.4% and 27.6% compared to their monocultures in faba bean/maize and chickpea/maize intercropping, respectively. However, P acquisition was generally not enhanced and even reduced in the last year in soybean/maize and oilseed rape/maize intercropping. Enhanced P acquisition was due to positive CE in faba bean/maize, and to positive CE and SE in chickpea/maize intercropping. Conclusions: Increased resource acquisition via CE and/or SE depended on the particular crop combination in intercropping systems. Application of the additive partitioning method to intercropping may help to identify underlying mechanisms of overyielding and carefully select crop combinations to enable more efficient resource use.
Can our global food system meet food demand within planetary boundaries?
Conijn, J.G. ; Bindraban, P.S. ; Schröder, J.J. ; Jongschaap, R.E.E. - \ 2018
Agriculture, Ecosystems and Environment 251 (2018). - ISSN 0167-8809 - p. 244 - 256.
Food system - GHG emission - Land use - Nitrogen - Phosphorus - Planetary boundaries - Sustainability
Global food demand is expected to increase, affecting required land, nitrogen (N) and phosphorus (P) inputs along with unintended emissions of greenhouse gasses (GHG) and losses of N and P. To quantify these input requirements and associated emissions/losses as a function of food demand, we built a comprehensive model of the food system and investigated the effects of multiple interventions in the food system on multiple environmental goals. Model outcomes are compared to planetary boundaries for land system change, climate change and the global N and P cycles to identify interventions that direct us towards a safe operating space for humanity. Results show a transgression of most boundaries already for 2010 and a drastic deterioration in the reference scenario for 2050 in which no improvements relative to 2010 were implemented. We defined the following improvements for 2050: reduction of waste, less consumption of animal products, higher feed conversion efficiency, higher crop and grassland yields, reduction of N and P losses from agricultural land and reduction of ammonia (NH3) volatilization. The effects of these measures were quantified individually and in combination. Significant trade-offs and synergies in our results underline the importance of a comprehensive analysis with respect to the entire food system, including multiple measures and environmental goals. The combination of all measures was able to partly prevent transgression of the boundaries for: agricultural area requirement, GHG emission and P flow into the ocean. However, global mineral N and P fertilizer inputs and total N loss to air and water still exceeded their boundaries in our study. The planetary boundary concept is discussed in relation to the selected variables and boundary values, including the additional necessity of eliminating the dependency of our food production on finite P reserves. We argue that total N loss is a better indicator of the environmental impacts of the global N cycle than fertilizer N input. Most measures studied in this paper are also on the agenda of the United Nations for Sustainable Development, which gives added support to their implementation.
Sustainable intensification through rotations with grain legumes in Sub-Saharan Africa : A review
Franke, A.C. ; Brand, G.J. van den; Vanlauwe, B. ; Giller, K.E. - \ 2018
Agriculture, Ecosystems and Environment 261 (2018). - ISSN 0167-8809 - p. 172 - 185.
Biotic factors - Cereals - Nitrogen fixation - Phosphorus - Residual benefits - Smallholder farmers

We conducted a systematic review of literature on the residual effects of grain legumes in cereal-based systems of sub-Saharan Africa (SSA) to quantify the magnitude and variability of rotational effects, to explore the importance of environmental and management factors in determining variability and to evaluate the evidence of the different mechanisms that explain rotational effects. We retrieved 44 unique publications providing 199 observations comparing continuous cereal performance with that of a grain legume-cereal rotation. The overall mean yield increase of 0.49t grainha-1, equal to an increase of 41% of the continuous cereal yield, is highly significant, but the variability in residual effects is large. Effects were more pronounced in southern Africa, the highlands of East Africa and the Guinea savannah, and less in the humid forest/derived savannah of West Africa and the Sudano-Sahelian zone. Maize showed stronger yield responses after a legume than millet and sorghum. Agro-ecological zone and cereal type were however confounded. All grain legume types significantly improved cereal yields, with stronger residual effects observed after soybean and groundnut than after cowpea. Fertiliser N application to cereals reduces the residual effects of legumes, but the response at 60-120kgNha-1 still equalled 0.32tha-1 or 59% of the response when no N is applied. The sustained benefits with large N applications indicate the importance of non-N effects. While mechanisms for improved soil P availability after grain legumes have been studied in some detail, it remains uncertain how important these are in farmers' fields. Grain legumes are unlikely to have a major influence on the availability of nutrients other than N and P, or on soil pH. Beneficial impacts of grain legumes on soil organic matter content can occur if legumes contribute to a greater overall cropping productivity, but studies generally report no such impacts. Evidence of impacts of grain legumes on weeds is limited to striga. Studies on the impacts on nematode pressure in cereals are inconclusive, probably because legumes act as a host for some of the key nematode genera that harm maize. The impact on the pressure of other pests and diseases in cereals is probably important, but evidence on this from SSA is lacking. Future research on N2-fixation by grain legumes and residual N benefits should focus on explaining the wide variability observed among sites. There is a clear need for more detailed mechanistic studies to assess the occurrence and relevance of non-N effects of grain legumes, particularly in relation to common pests and diseases in cereals.

Symbiotic soil fungi enhance ecosystem resilience to climate change
Martínez-García, Laura B. ; Deyn, Gerlinde B. de; Pugnaire, Francisco I. ; Kothamasi, David ; Heijden, Marcel G.A. van der - \ 2017
Global Change Biology 23 (2017)12. - ISSN 1354-1013 - p. 5228 - 5236.
Arbuscular mycorrhizal fungi - Climate change - Nitrogen - Nutrient leaching - Phosphorus - Rainfall regimes

Substantial amounts of nutrients are lost from soils through leaching. These losses can be environmentally damaging, causing groundwater eutrophication and also comprise an economic burden in terms of lost agricultural production. More intense precipitation events caused by climate change will likely aggravate this problem. So far it is unresolved to which extent soil biota can make ecosystems more resilient to climate change and reduce nutrient leaching losses when rainfall intensity increases. In this study, we focused on arbuscular mycorrhizal (AM) fungi, common soil fungi that form symbiotic associations with most land plants and which increase plant nutrient uptake. We hypothesized that AM fungi mitigate nutrient losses following intensive precipitation events (higher amount of precipitation and rain events frequency). To test this, we manipulated the presence of AM fungi in model grassland communities subjected to two rainfall scenarios: moderate and high rainfall intensity. The total amount of nutrients lost through leaching increased substantially with higher rainfall intensity. The presence of AM fungi reduced phosphorus losses by 50% under both rainfall scenarios and nitrogen losses by 40% under high rainfall intensity. Thus, the presence of AM fungi enhanced the nutrient interception ability of soils, and AM fungi reduced the nutrient leaching risk when rainfall intensity increases. These findings are especially relevant in areas with high rainfall intensity (e.g., such as the tropics) and for ecosystems that will experience increased rainfall due to climate change. Overall, this work demonstrates that soil biota such as AM fungi can enhance ecosystem resilience and reduce the negative impact of increased precipitation on nutrient losses.

Modeling sources of nutrients in rivers draining into the Bay of Bengal—a scenario analysis
Pedde, Simona ; Kroeze, Carolien ; Mayorga, Emilio ; Seitzinger, Sybil Putnam - \ 2017
Regional Environmental Change 17 (2017)8. - ISSN 1436-3798 - p. 2495 - 2506.
Bay of Bengal - Coastal eutrophication - Nitrogen - Phosphorus - River pollution - Silica

We model future trends in river export of nutrients to the Bay of Bengal, and the sources of this pollution. We focus on total nitrogen (TN), total phosphorus (TP), and dissolved silica (DSi) inputs to the Bay of Bengal Large Marine Ecosystem (BOB LME) in the years 2000, 2030, and 2050. In 2000, rivers exported 7.1 Tg N and 1.5 Tg P to the BOB LME. Three rivers (Ganges, Godavari, Irrawaddy) account for 75–80% of the total river export of N and P. For 2050, we calculate an increase in river export of N to 8.6 Tg, while P export stabilizes at the 2000 level. Future trends are the net effect of increasing river export of dissolved N (by 40%) and P (by 80%), and decreasing river export of particulate N and P. The increases in dissolved N and P loads are associated primarily with increased N and P losses from agriculture and sewage systems. The decreasing export of particulate N and P is associated with damming of rivers and increased human water consumption. There are large differences in nutrient export among rivers. Rivers draining into the western BOB LME generally export more N and P than eastern BOB LME rivers. Most N and P in western BOB LME rivers are from anthropogenic sources. Future increases in dissolved inorganic N and P (DIN and DIP) export can be large for individual rivers: up to more than a factor of five for DIP and more than a doubling for DIN. The calculated nutrient export ratios (N and P relative to DSi) indicate an increasing risk for blooms of non-siliceous algal species, which can potentially produce toxins and otherwise disrupt coastal ecosystems. Our results indicate that basin-specific management may be the most effective approach towards reducing the risk of coastal eutrophication in the BOB LME.

Determination of pre-cecal phosphorus digestibility of inorganic phosphates and bone meal products in broilers
Harn, J. van; Spek, J.W. ; Vuure, C.A. van; Krimpen, M.M. van - \ 2017
Poultry Science 96 (2017)5. - ISSN 0032-5791 - p. 1334 - 1340.
Bone meal - Broilers - Digestibility - Phosphorus

A broiler study was performed to determine the pre-cecal phosphorus (P) digestibility of 5 P sources, 3 from animal (Delfos, Calfos, and porcine bone meal) and 2 of inorganic (monocalcium phosphate [MCP] and dicalcium phosphate [DCP]) origin. Delfos is processed from bones resulting in a dicalcium phosphate product, and Calfos is processed from bones in which part of the gelatin is removed but in which the hydroxy-apatite matrix is preserved. During the first 14 d, birds were housed in floor pens bedded with wood shavings and received a commercial starter diet. At d 14, broilers were randomly assigned to pens (0.9 m2, 10 birds/pen) with a slatted floor. From d 14 onwards, one of the 6 experimental diets (a basal diet, and 5 diets containing the P sources) was provided. Test diets were replicated 6 times, and the basal diet 8 times. Electron microscopy images of test products were made in order to verify whether the spatial structure of the test products could be related to the pre-cecal P digestibility of the same products. Diets met or exceeded CVB (2011) requirements for all nutrients except for P and were formulated to contain a calcium to total P ratio of between 1.4 and 1.6 and a minimal amount of phytate P. Diets contained 5 g/kg titanium oxide as a marker to determine digestibility of P. At d 24 all birds were euthanized, after which the content of the terminal part of the ileum was sampled. The P digestibility was calculated by linear regression according to World's Poultry Science Association (WPSA) protocol for determination of pre-cecal P digestibility. Pre-cecal P digestibility of MCP, DCP, Delfos, Calfos, and porcine bone meal was 88.5, 82.4, 94.5, 86.9, and 78.2%, respectively. Based on visual inspection of electron microscopy images of test products, the spatial structure of the test products might be related to P digestibility. It is concluded that processing of bone meal increases the pre-cecal P digestibility in broilers.

Endogenous phosphorus losses in growing-finishing pigs and gestating sows
Bikker, P. ; Peet-Schwering, C.M.C. Van der; Gerrits, W.J.J. ; Sips, V. ; Walvoort, C. ; Laar, H. van - \ 2017
Journal of Animal Science 95 (2017)4. - ISSN 0021-8812 - p. 1637 - 1643.
Dietary fiber - Endogenous losses - Feces - Phosphorus - Pigs - Sows

An experiment was conducted to determine the effects of diet composition, feeding level (FL), and BW on endogenous phosphorous losses (EPL) using growing-finishing (GF) pigs and sows. After an adaptation period, 48 GF pigs (initial BW 90.5 kg) and 48 just-weaned sows (initial BW 195 kg), both individually housed, were allotted to 12 dietary treatments in a 2 × 3 × 2 factorial arrangement. Treatments were animal type (GF pigs or sows), diet composition (a semipurified starch (STA), inulin (INU), or lignocellulose (CEL) based low-P diet), and FL (2.0 or 3.0 kg/d). Digestibility of DM, OM, CP, crude fat, and carbohydrates (COH), and fecal P excretion (in g/d, mg/kg DMI, and g/(kg BW·d)) were determined using TiO2 as indigestible marker. Digestibility of OM and COH differed among diets (P < 0.001) and was greatest in both types of pigs fed the STA diet and lowest in those fed the CEL diet. While digestibility of OM and COH was similar in sows and GF pigs that were fed the STA diet and the CEL diet, on the INU diet, sows had, compared with GF pigs, a greater digest- ibility of OM (92.2 vs. 87.2%) and COH (92.5 vs. 88.4%), respectively. Both BW and FL increased fecal P excretion (g/d). When expressed in mg/kg DMI, P excretion was higher in sows than in GF pigs on the STA diet (498 versus 236 mg/kg DMI), the INU diet (526 vs. 316 mg/kg DMI), and the CEL diet (928 vs. 342 mg/kg DMI). When expressed in mg/(kg BW·d), however, P excretion was similar in GF pigs and sows that were fed the STA diet and in those that were fed the INU diet, whereas it was greater in sows than in GF pigs that were fed the CEL diet (11.6 vs. 7.3 mg/ (kg BW·d)). The results of this study indicate that EPL (mg/kg DMI) in pigs substantially increase with increasing BW. Application of EPL (mg/kg DMI) determined in GF pigs may underestimate EPL and therefore P requirements in gestating sows. Moreover, EPL is diet dependent and increases with an increasing content of dietary nonstarch polysaccharides (NSP). The degree of this increase may differ between sows and GF pigs and seems to depend on properties of dietary fiber.

Modeling farm nutrient flows in the North China Plain to reduce nutrient losses
Zhao, Zhanqing ; Bai, Zhaohai ; Wei, Sha ; Ma, Wenqi ; Wang, Mengru ; Kroeze, Carolien ; Ma, Lin - \ 2017
Nutrient Cycling in Agroecosystems 108 (2017)2. - ISSN 1385-1314 - p. 231 - 244.
Farm system - Losses - Nitrogen - North China Plain - NUFER-farm model - Phosphorus - Use efficiency
Years of poor nutrient management practices in the agriculture industry in the North China Plain have led to large losses of nutrients to the environment, causing severe ecological consequences. Analyzing farm nutrient flows is urgently needed in order to reduce nutrient losses. A farm-level nutrient flow model was developed in this study based on the NUFER (NUtrient flows in Food chains, Environment and Resources use) model, and was used to analyze nitrogen (N) and phosphorus (P) flows, use efficiencies, and losses for nine representative farm types in the North China Plain. Data from 401 farms were evaluated for the years 2012–2015. The analysis showed that mixed farms were more efficient in nutrient utilization than crop-based or landless livestock farms. The efficiencies of N and P used in crop production were highest for mixed dairy farms, reaching 67% for N and 68% for P. Consistently, mixed dairy farms had the lowest N and P surpluses and losses in crop production. Mixed swine farms were 5 and 9% higher in N and P efficiency in livestock production than landless swine farms, respectively. Losses of N and P from the animal manure management chain were 20–42% lower for mixed swine and 69–78% lower for mixed poultry farms than for landless farms of the same animal type. This is at least partially due to more frequent manure removal. Integrated crop-livestock production using livestock wastes as crop fertilizer was shown to be the most sustainable model in nutrient use for the agriculture industry in the North China Plain.
Exploring the pathways of earthworm-induced phosphorus availability
Ros, Mart B.H. ; Hiemstra, Tjisse ; Groenigen, Jan Willem van; Chareesri, Anupol ; Koopmans, Gerwin F. - \ 2017
Geoderma 303 (2017). - ISSN 0016-7061 - p. 99 - 109.
Earthworms - pH - Phosphorus - Plant growth - Surface complexation modelling

As many soils are unable to supply sufficient amounts of phosphorus (P) to plants, P availability is often a growth-limiting factor. Literature shows that levels of readily available P can be considerably higher in earthworm casts than in the surrounding bulk soil, possibly resulting in increased plant P uptake. However, the underlying mechanisms through which this increase of readily available P occurs are unclear. In a greenhouse pot experiment with annual ryegrass (Lolium multiflorum) on a soil with low P availability, we tested whether the presence of the anecic earthworm Lumbricus terrestris resulted in increased grass growth and P uptake and explored the possible mechanisms behind such an effect. During the pot experiment, earthworm casts were collected and analysed for water-extractable P as well as for most other relevant ions. The earthworm's presence significantly increased grass yield from 9.80 to 10.80 g dry matter per pot (p = 0.044) and P uptake from 6.32 to 8.04 mg per pot (p = 0.002). Due to increased microbial activity, the solution chemistry in the water extracts of the casts was dramatically changed compared to the bulk soil samples. The concentrations of dissolved inorganic P in cast were enhanced by a factor ~ 30–1000 compared to the levels found in bulk soil. The pH in earthworm casts increased from 5.9 to values between 7.4 and 9.0 and the Ca concentrations decreased by about a factor ~ 2-3 compared to bulk soil samples. In addition, there was an increase in dissolved organic carbon (35 mg L− 1 in casts versus 3 mg L− 1 in soil). Surface complexation modelling, using the Charge Distribution model, suggests that, besides an increase in pH, particularly an enhanced interaction of dissolved organic matter with reactive surface of metal (hydr)oxides is likely to be a major driving force for the augmented release of orthophosphate (PO4) via competitive adsorption and desorption. This competition for adsorption sites is an alternative pathway, next to mineralisation of organic matter, through which earthworms can increase soil fertility.

Long-term trends in nutrient budgets of the western Dutch Wadden Sea (1976–2012)
Jung, A.S. ; Brinkman, A.G. ; Folmer, E.O. ; Herman, Peter M.J. ; Veer, Henk W. van der; Philippart, C.J.M. - \ 2017
Journal of Sea Research 127 (2017). - ISSN 1385-1101 - p. 82 - 94.
Wadden Sea - Coastal North Sea - Nutrient exchange - Nitrogen - Phosphorus - Eutrophication - Nutrient budgets
Long-term field observations of nitrogen [N] and phosphorus [P] concentrations were used to construct nutriënt budgets for the western Dutch Wadden Sea between 1976 and 2012. Nutrients come into the western Dutch Wadden Sea via river runoff, through exchange with the coastal zone of the North Sea, neighbouring tidal basins and through atmospheric deposition (for N). The highest concentrations in phosphorus and nitrogen were observed
in themid-1980s. Improved phosphorus removal atwaste water treatment plants, management of fertilization in agriculture and removal of phosphates from detergents led to reduced riverine nutrient inputs and, consequently, reduced nutrient concentrations in theWadden Sea. The budgets suggest that the period of the initial net import of phosphorus and nitrogen switched to a net export in 1981 for nitrogen and in 1992 for phosphorus. Such different behaviour in nutrient budgets during the rise and fall of external nutriënt concentrations may be the result of different sediment-water exchange dynamics for P and N. It is hypothesized that during the period of increasing eutrophication (1976–1981) P, and to a lesser degree N, were stored in sediments as organic and inorganic nutrients. In the following period (1981–1992) external nutrient concentrations
(especially in the North Sea) decreased, but P concentrations in the Wadden Sea remained high due to prolonged sediment release, whilst denitrification removed substantial amounts of N. From1992 onwards, P andN budgetswere closed by net loss,most probably because P stores were then depleted and denitrification continued. Under the present conditions (lower rates of sediment import and depleted P stores), nutrient concentrations in this area are expected to be more strongly influenced by wind-driven exchange with the North Sea and precipitation-driven discharge from Lake IJssel. This implies that the consequences of climate change will be more important, than during the 1970s and 1980s.
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