Thijs Nest - Academia.edu (original) (raw)

Papers by Thijs Nest

Phosphorus (P) is an essential nutrient for all living organisms. P is present in every living ce... more Phosphorus (P) is an essential nutrient for all living organisms. P is present in every living cell, and no other element can replace it in its vital role in several physiological and biochemical processes. However, its supply in the earth s crust is limited. P is of most concern because of the rate of exploitation of this non-renewable resource to meet current demand. Globally, recycling processes gain in interest to reduce the required amount of mined P.Many agricultural soils around the globe, mainly in tropical regions, are P deficient. However, in many agricultural regions such as Northwestern Europe, several states in the United States of America, the Baltic sea region and several provinces in China, P accumulation took place in the past decades, due to high doses of P fertilization. These are due to (i) the availability of cheap mineral P fertilizers and/or (ii) the large livestock, fed with large amounts of imported feed. These feeds contain large amounts of P, transferred inefficiently by animals to animal products and largely transferred to animal manure, that is mainly applied on the agricultural fields nearby. P is being sorbed to the soil by reactive clay particles, Ca, Al and Fe (hydr)oxides, organic matter and carbonates and is therefore quite immobile in the soil. However, all soils have a finite capacity to retain P and continued application of fertilizers will ultimately reach the environmental limit for safe storage of P. The amount of P lost to the environment with non-point leaching, will be determined by the sorbed amount of P and the P retention capabilities of the soil. This implies that P leaching is mainly determined by the total P fertilization. However in several studies based on long term field trials, it was observed that with the addition of organic amendments to the soil, soil P intensity and P leaching were increased, compared to mineral fertilizers at the same P input level. This means that the eventual P leaching will also be determined by the type of fertilizer and his chemical composition.In Flanders, many intensively managed agricultural soils suffer from decreasing soil organic carbon (SOC) levels, but have also extremely elevated P contents (P-AL >> 180 mg/kg dry soil). One of the strategies to maintain the SOC levels, is growing catch crops during autumn, and incorporating the produced biomass in early spring. Incorporation of catch crops in early spring, can however induce P mineralization, before the next crop is installed and starts taking up P from the soil solution. We hypothesized that in excessively P containing soils thiese catch crop residues increase the P leaching losses. Another strategy is adding organic amendments to the soil by applying a wide variety of organic fertilizers such as animal slurries, farmyard manure, several types of compost, processed digestate products, etc. However, the chemical and organic matter composition of these organic fertilizers is very different, which has an important influence on the potential to increase the SOC level. Furthermore, it is not known which influence these differences have on P leaching. This study was conducted to investigate which organic fertilizers have the highest potential to increase or at least maintain the SOC level without any further increase in P leaching.We investigated whether P leaching was increased by winter/early spring incorporation of catch crop residues from white mustard (Sinapis alba L.), Italian ryegrass (Lolium multiflorum L.), black oats (Avena strigosa L.) and a mixture of perennial ryegrass/white clover (Lolium perenne L./Trifolium repens L.). The incorporation of the catch crop residues was imitated by mixing a sample of the soil where the catch crop was grown, with a plant sample at a dose equal to the biomass crop yield of the catch crop in the field trial and in the state the plant tissue was in early spring. By conducting a leaching experiment with these mixtures, the influence of the incorporated catch crop residue on the P leaching could be compared with the fallow soil. Incorporation of white mustard, Italian ryegrass and perennial ryegrass/white clover crop residues, resulted in an approximately 40% decrease of P concentrations in the leachate, compared to the fallow soil and the soil with incorporation of black oats. We indicated that Italian ryegrass and perennial ryegrass/white clover incorporation reduced the P leaching by P immobilization processes. In contrast, decomposition of the white mustard and black oats was small. Little or no P was mineralized by these catch crop residues. The crop residues of black oats contained however 5 times more soluble P compared to white mustard crop residues. P in the black oats was eventually leaked out of the plant tissue during the leaching experiment, leading to P concentrations in the leachates, comparable to those of the fallow soil. We conclude that incorporation of the studied catch crops do not increase P leaching.…

Environmental Science and Pollution Research, May 14, 2020

Fertilization with animal manure is one of the main routes responsible for the introduction of an... more Fertilization with animal manure is one of the main routes responsible for the introduction of antibiotic residues, antibiotic resistance genes, and zoonotic bacteria into the environment. The aim of this study was to assess the effect of the use of pig (swine) manure as a fertilizer on the presence and fate of six antibiotic residues, nine antibiotic resistance genes, and bacteria (zoonotic bacteria Salmonella spp. and Campylobacter spp. and E. coli as indicator for Gram-negative bacterial species of the microbiota of livestock) on five fields. To the best of our knowledge, the present study is the first to assess a multitude of antibiotic residues and resistance to several classes of antibiotics in pig manure and in fertilized soil over time in a region with an intensive pig industry (Flanders, Belgium). The fields were sampled at five consecutive time points, starting before fertilization up to harvest. Low concentrations of antibiotic residues could be observed in the soils until harvest. The antibiotic resistance genes studied were already present at background levels in the soil environment prior to fertilization, but after fertilization with pig manure, an increase in relative abundance was observed for most of them, followed by a decline back to background levels by harvest-time on all of the fields studied. No apparent differences regarding the presence of antibiotic resistance genes in soils were observed between those fertilized with manure that either contained antibiotic residues or not. With regard to dissemination of resistance, the results presented in this study confirm that fertilization with animal manure directly adds resistance genes to the soil. In addition, it shows that this direct mechanism may be more important than possible selective pressure in soil-dwelling bacteria exerted by antibiotic residues present in the manure. These results also indicate that zoonotic bacteria detected in the manure could be detected in the soil environment directly after fertilization, but not after 1 month. In conclusion, although some antibiotic residues may be present in both manure and soil at concentrations to exert selective pressure, it seems that antibiotic resistance is mostly introduced directly to soil through fertilization with animal manure.

De Vlaamse overheid heeft de randvoorwaarden erosie in 2015 aangescherpt. Verlies van de vruchtba... more De Vlaamse overheid heeft de randvoorwaarden erosie in 2015 aangescherpt. Verlies van de vruchtbare bovenlaag van de bodem is nefast en dit in de eerste plaats voor de teler. Het ruimen van de weggespoelde grond kost de overheid bovendien heel wat geld. Om in ruggenteelten op erosiegevoelige percelen het afspoelen van water, vruchtbare grond, meststoffen en pesticiden te voorkomen, komt het erop aan de bodem in de tussenrug zoveel mogelijk te verruwen om zodoende de infiltratiecapaciteit te verhogen. Dit kan je doen met drempeltjes, zoals in de aardappelteelt. Maar we onderzochten ook andere methoden, zoals tandbewerkingen, op de praktische haalbaarheid en hun erosiereducerend effect. Elke verruwing van de tussenrug leidde in de aangelegde proeven tot minder erosie. Drempeltjes bleken het best bestand tegen hevige regenbuien.

Bodem en bemesting Teelt van erwt weinig erosiegevoelig In vergelijking met teelten zoals mais, u... more Bodem en bemesting Teelt van erwt weinig erosiegevoelig In vergelijking met teelten zoals mais, ui of kolen lijkt de teelt van erwten weinig erosiegevoelig, zowel na ploegen als na een niet-kerende bodembewerking. Na ploegen kan het soms nodig zijn om het zaaibed intensiever te bewerken waardoor de kans op erosie wel wat toeneemt. Kies je voor een niet-kerende bodembewerking dan moet je daar bij de keuze van de voorafgaande groenbedekker al rekening mee houden. De kwaliteit van het zaaibed en de zaadafleg zijn cruciaal voor een goede opbrengst. Het is ook zeer belangrijk om bodemverdichting in de bouwvoor zo veel mogelijk op te heffen. De voorbije drie jaar werden in het GOMEROSproject vier proefpercelen met erwten aangelegd verspreid over hellende percelen in Vlaanderen. De bedoeling was om na te gaan hoe niet-kerende bodembewerking en zaaibedbereiding het best worden uitgevoerd om de teelt van erwten te laten slagen en tegelijkertijd het risico op erosie zoveel mogelijk te beperken. We vatten de ervaringen die we opdeden samen in dit artikel. Dit onderzoek werd uitgevoerd in het kader van het LA-traject 'GOMEROS; De teelt van groenten en mais laten slagen binnen de nieuwe randvoorwaarden erosie'.

PubMed, 2015

Grass seed crops (ryegrass), a minor crop in Belgium, should be managed more intensively and in a... more Grass seed crops (ryegrass), a minor crop in Belgium, should be managed more intensively and in an arable way, comparable with the intensive wheat culture. Even more important than higher seed yields are stable, higher yields over time, Integrated pest management (IPM) forms the framework around this intensification. Two similar seed production field trials--one with perennial ryegrass (Lolium perenne L.) and one with Italian ryegrass (Lolium multiflorum L.)--were conducted in 2014, dealing with 4 SDHI fungicides (bixafen, boscalid, fluxapyroxad and isopyrazam) that were compared with an untreated control and some reference treatments. There were four application times (stages): i.e. early stem elongation--BBCH 33 (T1), ear tips visible--BBCH 51 (T2), full ear, begin of flowering--BBCH 61 (T3) and end of flowering--BBCH 69 (T4). Except for the Italian ryegrass trial, only the last three stages were used. In the Italian ryegrass trial, which had only sporadic incidence of disease, all T3 treatments clearly increased seed yield compared with the untreated control, by 13% on average. For the T2 treatments only Fandango and Adexar clearly out yielded the control. The curative T4 treatment (Tilt + Corbel) tended to increase seed yield, but this was not significant. Seed yield differences could not be explained by variations in thousand seed weight (TSW), leaf withering and NDVI scores (crop reflectance). The disease pressure (crown rust) was very low before flowering, but stem rust developed strongly during the last 2 weeks before harvest of the perennial ryegrass trial. Yield responses were mostly pronounced at the T3 treatment. Except for Fandango and Horizon, all T3 treatments clearly increased yield in comparison with the untreated control, by 18.4% on average. The T4 treatment (Tilt + Corbel) could not repair the crop damage. Further seed yield data are discussed in relation to yield components, TSW, leaf withering and vegetation index (NDVI). An integrated approach for a single, profitable fungicide application in grass seed will be necessary, taking into account the disease development during the season and depending upon grass species and variety.

Phosphorus (P) is an essential nutrient for all living organisms. P is present in every living ce... more Phosphorus (P) is an essential nutrient for all living organisms. P is present in every living cell, and no other element can replace it in its vital role in several physiological and biochemical processes. However, its supply in the earth s crust is limited. P is of most concern because of the rate of exploitation of this non-renewable resource to meet current demand. Globally, recycling processes gain in interest to reduce the required amount of mined P.Many agricultural soils around the globe, mainly in tropical regions, are P deficient. However, in many agricultural regions such as Northwestern Europe, several states in the United States of America, the Baltic sea region and several provinces in China, P accumulation took place in the past decades, due to high doses of P fertilization. These are due to (i) the availability of cheap mineral P fertilizers and/or (ii) the large livestock, fed with large amounts of imported feed. These feeds contain large amounts of P, transferred inefficiently by animals to animal products and largely transferred to animal manure, that is mainly applied on the agricultural fields nearby. P is being sorbed to the soil by reactive clay particles, Ca, Al and Fe (hydr)oxides, organic matter and carbonates and is therefore quite immobile in the soil. However, all soils have a finite capacity to retain P and continued application of fertilizers will ultimately reach the environmental limit for safe storage of P. The amount of P lost to the environment with non-point leaching, will be determined by the sorbed amount of P and the P retention capabilities of the soil. This implies that P leaching is mainly determined by the total P fertilization. However in several studies based on long term field trials, it was observed that with the addition of organic amendments to the soil, soil P intensity and P leaching were increased, compared to mineral fertilizers at the same P input level. This means that the eventual P leaching will also be determined by the type of fertilizer and his chemical composition.In Flanders, many intensively managed agricultural soils suffer from decreasing soil organic carbon (SOC) levels, but have also extremely elevated P contents (P-AL >> 180 mg/kg dry soil). One of the strategies to maintain the SOC levels, is growing catch crops during autumn, and incorporating the produced biomass in early spring. Incorporation of catch crops in early spring, can however induce P mineralization, before the next crop is installed and starts taking up P from the soil solution. We hypothesized that in excessively P containing soils thiese catch crop residues increase the P leaching losses. Another strategy is adding organic amendments to the soil by applying a wide variety of organic fertilizers such as animal slurries, farmyard manure, several types of compost, processed digestate products, etc. However, the chemical and organic matter composition of these organic fertilizers is very different, which has an important influence on the potential to increase the SOC level. Furthermore, it is not known which influence these differences have on P leaching. This study was conducted to investigate which organic fertilizers have the highest potential to increase or at least maintain the SOC level without any further increase in P leaching.We investigated whether P leaching was increased by winter/early spring incorporation of catch crop residues from white mustard (Sinapis alba L.), Italian ryegrass (Lolium multiflorum L.), black oats (Avena strigosa L.) and a mixture of perennial ryegrass/white clover (Lolium perenne L./Trifolium repens L.). The incorporation of the catch crop residues was imitated by mixing a sample of the soil where the catch crop was grown, with a plant sample at a dose equal to the biomass crop yield of the catch crop in the field trial and in the state the plant tissue was in early spring. By conducting a leaching experiment with these mixtures, the influence of the incorporated catch crop residue on the P leaching could be compared with the fallow soil. Incorporation of white mustard, Italian ryegrass and perennial ryegrass/white clover crop residues, resulted in an approximately 40% decrease of P concentrations in the leachate, compared to the fallow soil and the soil with incorporation of black oats. We indicated that Italian ryegrass and perennial ryegrass/white clover incorporation reduced the P leaching by P immobilization processes. In contrast, decomposition of the white mustard and black oats was small. Little or no P was mineralized by these catch crop residues. The crop residues of black oats contained however 5 times more soluble P compared to white mustard crop residues. P in the black oats was eventually leaked out of the plant tissue during the leaching experiment, leading to P concentrations in the leachates, comparable to those of the fallow soil. We conclude that incorporation of the studied catch crops do not increase P leaching.…

Environmental Science and Pollution Research, May 14, 2020

Fertilization with animal manure is one of the main routes responsible for the introduction of an... more Fertilization with animal manure is one of the main routes responsible for the introduction of antibiotic residues, antibiotic resistance genes, and zoonotic bacteria into the environment. The aim of this study was to assess the effect of the use of pig (swine) manure as a fertilizer on the presence and fate of six antibiotic residues, nine antibiotic resistance genes, and bacteria (zoonotic bacteria Salmonella spp. and Campylobacter spp. and E. coli as indicator for Gram-negative bacterial species of the microbiota of livestock) on five fields. To the best of our knowledge, the present study is the first to assess a multitude of antibiotic residues and resistance to several classes of antibiotics in pig manure and in fertilized soil over time in a region with an intensive pig industry (Flanders, Belgium). The fields were sampled at five consecutive time points, starting before fertilization up to harvest. Low concentrations of antibiotic residues could be observed in the soils until harvest. The antibiotic resistance genes studied were already present at background levels in the soil environment prior to fertilization, but after fertilization with pig manure, an increase in relative abundance was observed for most of them, followed by a decline back to background levels by harvest-time on all of the fields studied. No apparent differences regarding the presence of antibiotic resistance genes in soils were observed between those fertilized with manure that either contained antibiotic residues or not. With regard to dissemination of resistance, the results presented in this study confirm that fertilization with animal manure directly adds resistance genes to the soil. In addition, it shows that this direct mechanism may be more important than possible selective pressure in soil-dwelling bacteria exerted by antibiotic residues present in the manure. These results also indicate that zoonotic bacteria detected in the manure could be detected in the soil environment directly after fertilization, but not after 1 month. In conclusion, although some antibiotic residues may be present in both manure and soil at concentrations to exert selective pressure, it seems that antibiotic resistance is mostly introduced directly to soil through fertilization with animal manure.

De Vlaamse overheid heeft de randvoorwaarden erosie in 2015 aangescherpt. Verlies van de vruchtba... more De Vlaamse overheid heeft de randvoorwaarden erosie in 2015 aangescherpt. Verlies van de vruchtbare bovenlaag van de bodem is nefast en dit in de eerste plaats voor de teler. Het ruimen van de weggespoelde grond kost de overheid bovendien heel wat geld. Om in ruggenteelten op erosiegevoelige percelen het afspoelen van water, vruchtbare grond, meststoffen en pesticiden te voorkomen, komt het erop aan de bodem in de tussenrug zoveel mogelijk te verruwen om zodoende de infiltratiecapaciteit te verhogen. Dit kan je doen met drempeltjes, zoals in de aardappelteelt. Maar we onderzochten ook andere methoden, zoals tandbewerkingen, op de praktische haalbaarheid en hun erosiereducerend effect. Elke verruwing van de tussenrug leidde in de aangelegde proeven tot minder erosie. Drempeltjes bleken het best bestand tegen hevige regenbuien.

Bodem en bemesting Teelt van erwt weinig erosiegevoelig In vergelijking met teelten zoals mais, u... more Bodem en bemesting Teelt van erwt weinig erosiegevoelig In vergelijking met teelten zoals mais, ui of kolen lijkt de teelt van erwten weinig erosiegevoelig, zowel na ploegen als na een niet-kerende bodembewerking. Na ploegen kan het soms nodig zijn om het zaaibed intensiever te bewerken waardoor de kans op erosie wel wat toeneemt. Kies je voor een niet-kerende bodembewerking dan moet je daar bij de keuze van de voorafgaande groenbedekker al rekening mee houden. De kwaliteit van het zaaibed en de zaadafleg zijn cruciaal voor een goede opbrengst. Het is ook zeer belangrijk om bodemverdichting in de bouwvoor zo veel mogelijk op te heffen. De voorbije drie jaar werden in het GOMEROSproject vier proefpercelen met erwten aangelegd verspreid over hellende percelen in Vlaanderen. De bedoeling was om na te gaan hoe niet-kerende bodembewerking en zaaibedbereiding het best worden uitgevoerd om de teelt van erwten te laten slagen en tegelijkertijd het risico op erosie zoveel mogelijk te beperken. We vatten de ervaringen die we opdeden samen in dit artikel. Dit onderzoek werd uitgevoerd in het kader van het LA-traject 'GOMEROS; De teelt van groenten en mais laten slagen binnen de nieuwe randvoorwaarden erosie'.

PubMed, 2015

Grass seed crops (ryegrass), a minor crop in Belgium, should be managed more intensively and in a... more Grass seed crops (ryegrass), a minor crop in Belgium, should be managed more intensively and in an arable way, comparable with the intensive wheat culture. Even more important than higher seed yields are stable, higher yields over time, Integrated pest management (IPM) forms the framework around this intensification. Two similar seed production field trials--one with perennial ryegrass (Lolium perenne L.) and one with Italian ryegrass (Lolium multiflorum L.)--were conducted in 2014, dealing with 4 SDHI fungicides (bixafen, boscalid, fluxapyroxad and isopyrazam) that were compared with an untreated control and some reference treatments. There were four application times (stages): i.e. early stem elongation--BBCH 33 (T1), ear tips visible--BBCH 51 (T2), full ear, begin of flowering--BBCH 61 (T3) and end of flowering--BBCH 69 (T4). Except for the Italian ryegrass trial, only the last three stages were used. In the Italian ryegrass trial, which had only sporadic incidence of disease, all T3 treatments clearly increased seed yield compared with the untreated control, by 13% on average. For the T2 treatments only Fandango and Adexar clearly out yielded the control. The curative T4 treatment (Tilt + Corbel) tended to increase seed yield, but this was not significant. Seed yield differences could not be explained by variations in thousand seed weight (TSW), leaf withering and NDVI scores (crop reflectance). The disease pressure (crown rust) was very low before flowering, but stem rust developed strongly during the last 2 weeks before harvest of the perennial ryegrass trial. Yield responses were mostly pronounced at the T3 treatment. Except for Fandango and Horizon, all T3 treatments clearly increased yield in comparison with the untreated control, by 18.4% on average. The T4 treatment (Tilt + Corbel) could not repair the crop damage. Further seed yield data are discussed in relation to yield components, TSW, leaf withering and vegetation index (NDVI). An integrated approach for a single, profitable fungicide application in grass seed will be necessary, taking into account the disease development during the season and depending upon grass species and variety.