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The aim of the project Biobased Fertilisers Achterhoek (‘Kunstmestvrije Achterhoek’ in Dutch) is to make fertilisation practices more sustainable through use of locally available nutrients from renewable sources. The project is part of the Sixth Action Programme of the Netherlands, which serves the Nitrates Directive. One of the objectives is to determine the nitrogen fertiliser replacement value of biobased fertilising products made from animal manure. A second objective is to assess the risk of nitrogen leaching from these biobased fertilising products. These objectives were implemented by WUR-Wageningen Environmental Research in a monitoring programme with field experiments on grassland and on arable land with silage maize. This document reports the results of a field experiment on grassland which was conducted in 2020. The field experiment on grassland points on a similar agronomic effectivity of the biobased nitrogen fertilising product compared to calcium ammonium nitrate. The environmental performances of all fertilising products with equal rates of nitrogen were comparable.

The aim of the project Biobased Fertilisers Achterhoek (‘Kunstmestvrije Achterhoek’ in Dutch) is to make fertilisation practices more sustainable through use of locally available nutrients from renewable sources. The project is part of the Sixth Action Programme of the Netherlands, which serves the Nitrates Directive. One of the objectives is to determine the nitrogen fertiliser replacement value of biobased fertilising products made from animal manure. A second objective is to assess the risk of nitrogen leaching from these biobased fertilising products. These objectives were implemented by WUR-Wageningen Environmental Research in a monitoring programme with field experiments on grassland and on arable land with silage maize. This document reports the results of a field experiment on grassland which was conducted in 2020. The field experiment on grassland points on a similar agronomic effectivity of the biobased nitrogen fertilising product compared to calcium ammonium nitrate. The environmental performances of all fertilising products with equal rates of nitrogen were comparable. De doelstelling van het project KunstmestVrije Achterhoek (KVA) is het verduurzamen van de bemestingspraktijk door de bemesting van grasland en bouwland zo veel mogelijk in te vullen met regionaal beschikbare nutriënten. Het project is onderdeel is van het zesde Nederlandse actieprogramma in het kader van de Nitraatrichtlijn. Een van de doelstellingen betreft het bepalen van de agronomische effectiviteit van stikstof van stikstofhoudende bemestingsproducten geproduceerd uit (co-vergiste) varkensmest. Een tweede doelstelling is het bepalen van risico’s op milieubezwaarlijkheid gelet op stikstof uitspoeling. Deze doelstellingen zijn door WUR-Wageningen Environmental Research uitgewerkt in een monitoringsprogramma met veldproeven op grasland en op maisland. Dit rapport geeft de resultaten van een veldproef op grasland die in 2020 werd uitgevoerd op het proefbedrijf De Marke. De agronomische effectiviteit van de biogebaseerde stikstof meststof was vergelijkbaar met die van kalkammonsalpeter. Na de oogst van de laatste snede was de voorraad minerale stikstof in de bodemlaag 0 – 90 cm bij het biogebaseerde stikstofmeststof eveneens vergelijkbaar met de voorraad bij kalkammonsalpeter.

The aim of the project Biobased Fertilisers Achterhoek (‘Kunstmestvrije Achterhoek’ in Dutch) was to make fertilisation practices more sustainable through use of locally available nutrients that are derived from renewable sources. The project is part of the Sixth Action Programme of the Netherlands which serves the Nitrates Directive. One of the objectives was to determine the nitrogen fertiliser replacement value of biobased fertilising products that are made from animal manure. A second objective was to assess the risk of nitrogen leaching from these biobased fertilising products. These objectives were implemented by WUR- Wageningen Environmental Research in a monitoring programme which included field experiments carried out on grassland and on arable land with silage maize. This document reports the results of a second field experiment on grassland which was conducted in 2021. These results have indicated that the biobased nitrogen fertilisers tested could serve as a replacement for mineral nitrogen fertiliser.

The aim of the project Biobased Fertilisers Achterhoek (‘Kunstmestvrije Achterhoek’ in Dutch) was to make fertilisation practices more sustainable through use of locally available nutrients that are derived from renewable sources. The project is part of the Sixth Action Programme of the Netherlands which serves the Nitrates Directive. One of the objectives was to determine the nitrogen fertiliser replacement value of biobased fertilising products that are made from animal manure. A second objective was to assess the risk of nitrogen leaching from these biobased fertilising products. These objectives were implemented by WUR- Wageningen Environmental Research in a monitoring programme which included field experiments carried out on grassland and on arable land with silage maize. This document reports the results of a second field experiment on grassland which was conducted in 2021. These results have indicated that the biobased nitrogen fertilisers tested could serve as a replacement for mineral nitrogen fertiliser. De doelstelling van het project KunstmestVrije Achterhoek (KVA) is het verduurzamen van de bemestingspraktijk door de bemesting van grasland en bouwland zo veel mogelijk in te vullen met regionaal beschikbare nutriënten. Het project is onderdeel is van het zesde Nederlandse actieprogramma in het kader van de Nitraatrichtlijn. Een van de doelstellingen betreft het bepalen van de agronomische effectiviteit van stikstof van stikstofhoudende bemestingsproducten geproduceerd uit co-vergiste varkensmest. Een tweede doelstelling het bepalen van enig risico op milieubezwaarlijkheid gelet op stikstof uitspoeling. Deze doelstellingen zijn door WUR-Wageningen Environmental Research uitgewerkt in een monitoringsprogramma met veldproeven op grasland en op maisland. Dit rapport geeft de resultaten van een tweede veldproef op grasland die in 2021 werd uitgevoerd op het proefbedrijf De Marke. De agronomische effectiviteit van de biogebaseerde stikstof meststof was vergelijkbaar met die van kalkammonsalpeter

The aim of the project Biobased Fertilisers Achterhoek (‘Kunstmestvrije Achterhoek’ in Dutch) is to make fertilisation practices more sustainable through the use of locally available nutrients from renewable sources. The project is part of the Sixth Action Programme of the Netherlands which serves the Nitrates Directive. One of the objectives was to determine the nitrogen fertiliser replacement value of biobased fertilising products made from animal manure. A second objective was to assess the risk of nitrogen leaching from these biobased fertilising products. These objectives were implemented by WUR-Wageningen Environmental Research in a monitoring programme that included field experiments on grassland and on arable land with silage maize. This document reports the results of a field experiment with silage maize which was conducted in 2020.

In the context of the Sixth Action Program of the Netherlands for the Nitrates Directive, the Pilot Biobased Fertilisers Achterhoek was implemented. Wageningen Environmental Research supported this pilot with a Monitoring Program that was carried out from 2018 until 2021. The subjects of the Monitoring Program were to investigate the risks associated with blending of bio-based fertilising products, to support demonstration fields in practice, and to carry out four, scientifically based field trials and reports on the research into these subjects. This report is the synthesis report of research results obtained from the Monitoring Program.

The aim of the project Biobased Fertilisers Achterhoek (‘Kunstmestvrije Achterhoek’ in Dutch) is to make fertilisation practices more sustainable through the use of locally available nutrients from renewable sources. The project is part of the Sixth Action Programme of the Netherlands which serves the Nitrates Directive. One of the objectives was to determine the nitrogen fertiliser replacement value of biobased fertilising products made from animal manure. A second objective was to assess the risk of nitrogen leaching from these biobased fertilising products. These objectives were implemented by WUR-Wageningen Environmental Research in a monitoring programme that included field experiments on grassland and on arable land with silage maize. This document reports the results of a field experiment with silage maize which was conducted in 2020. De doelstelling van het project KunstmestVrije Achterhoek (KVA) is het verduurzamen van de bemestingspraktijk door de bemesting van grasland en bouwland zo veel mogelijk in te vullen met regionaal beschikbare nutriënten. Het project is onderdeel is van het zesde Nederlandse actieprogramma in het kader van de Nitraatrichtlijn. Een van de doelstellingen betreft het bepalen van de agronomische effectiviteit van stikstof van stikstofhoudende bemestingsproducten gebaseerd op mest. Een tweede doelstelling het bepalen van enig risico op milieubezwaarlijkheid gelet op stikstof uitspoeling. Deze doelstellingen zijn door WUR- Wageningen Environmental Research uitgewerkt in een monitoringsprogramma met veldproeven op grasland en op maisland. Dit rapport geeft de resultaten van een veldproef met snijmais die in 2020 werd uitgevoerd op het proefbedrijf De Marke.

In the context of the Sixth Action Program of the Netherlands for the Nitrates Directive, the Pilot Biobased Fertilisers Achterhoek was implemented. Wageningen Environmental Research supported this pilot with a Monitoring Program that was carried out from 2018 until 2021. The subjects of the Monitoring Program were to investigate the risks associated with blending of bio-based fertilising products, to support demonstration fields in practice, and to carry out four, scientifically based field trials and reports on the research into these subjects. This report is the synthesis report of research results obtained from the Monitoring Program. In het kader van het zesde actieprogramma van Nederland voor de Nitraatrichtlijn werd de gebiedsgerichte Pilot Kunstmestvrije Achthoek uitgevoerd. Wageningen Environmental Research ondersteunde deze pilot met een monitoringsprogramma dat van 2018 tot en met 2021 werd uitgevoerd. Het monitoringsprogramma had als onderwerpen het onderzoeken van risico’s verbonden aan het blenden van bio-gebaseerde bemestingsproducten, ondersteuning van demonstratievelden in de praktijk en uitvoering van een viertal wetenschappelijk gebaseerde veldproeven en rapportages van het onderzoek van deze onderwerpen. Dit rapport is het syntheserapport van verkregen onderzoeksresultaten van het monitoringsprogramma.

The aim of this thesis was to improve understanding of the role of organic inputs and soil organic matter (SOM) for crop production in contemporary arable farming in Europe. For this purpose, long-term experiments were analysed on the additional yield effect of organic inputs and savings in mineral fertiliser. In addition, a farm survey was conducted to find drivers and barriers for the use of organic inputs and to assess if arable farmers in Europe perceive a deficiency of SOM. The findings in this thesis suggest that at least on the shorter term, on average, there seems to be no immediate threat from a deficiency of SOM to crop production in arable farming in Europe. The long-term experiments showed that with sufficient use of only mineral fertilisers, on average, similar yields could be attained over multiple years as with the combined use of organic inputs and mineral fertiliser. This was reflected in the farm survey, in which a large majority of farmers indicated not to perceive a deficiency of SOM. Analysis of long-term experiments also showed that more mineral fertiliser N was saved when using farmyard manure at high N rates (with mineral fertiliser application) than at low N rates (without mineral fertiliser application), based on comparisons at equal yield. Specific crops and environments did benefit from organic inputs and more SOM in terms of crop production. Long-term experiments showed that organic inputs give benefit to crop production in wet climates and on sandy soils. In addition, farmers perceived a higher deficiency of SOM on steep slopes, sandy soils, wet and very dry climates. The additional yield effect of organic inputs was significant for potatoes. More in general, farmers who cultivated larger shares of their land with specialized crops (including potatoes, sugar beets, onions and other vegetables) than cereals perceived a higher deficiency of SOM. It seems that while the functions of SOM can be replaced with technical means to a large extent (e.g. tillage, use of mineral fertilisers), there are limits to this technical potential when environmental conditions are more extreme and crops are more demanding. The farm survey revealed that farmers perceive a trade-off between improved soil quality on the one hand and increased pressures from weeds, pests and diseases and financial consequences on the other hand when using organic inputs. If policies aim to stimulate the maintenance or increase of SOM, more insight is needed into the conditions that regulate the pressures of weeds, pests and diseases in response to organic inputs. Financial consequences (at least on the short term) should also be accounted for. More importantly however, benefits from SOM for crop production cannot be taken for granted. Only in specific situations such benefits will exist. If European policies on SOM aim to include benefits for crop production, focus should be on areas with more extreme environmental conditions (very dry or wet climates, steep slopes, sandy soils), or cropping systems with more specialized or horticultural crops rather than cereals.

Spinach (Spinacia oleracea L.) is one of the most consumed leafy vegetables worldwide and it is considered to be highly nutritious. Spinach is a short-cycle leafy crop that has a high demand for nitrogen in order to rapidly come to a harvestable product that has the required dark green colour within a reasonable harvest window. In commercial production of spinach the recovery of N is poor, which may result in environmental pollution. To increase sustainability of both organic and conventional spinach cultivation there is a need to reduce the dependency on high levels of nitrogen. Growers therefore urgently need cultivars with a satisfactory yield under reduced N input conditions. Nitrogen use efficiency (NUE), defined as the ability to produce high biomass per unit N applied, is low in spinach. The present study aims to evaluate spinach genotypes for selectable traits under varying N supply and provide tools and knowledge to facilitate the development of varieties with good yield, quality and stability under low N input. To minimise environmental variation affecting the identification of traits related to NUE a screening method was developed using a hydroponics system. The genetic diversity for NUE related traits was first studied with 24 commercial cultivars under contrasting levels of N supply based on the Ingestad model with a steady-state N application. This demonstrated that the hydroponics screening strategy as a pre-screening tool enabled reliable detection of heritable variation among cultivars for NUE-related traits under optimal as well as suboptimal N input. Shoot dry weight and leaf area were preferred selectable traits for the detection of heritable differences contributing to NUE in spinach. The effect of N application strategy was examined in seven cultivars grown under hydroponics conditions with low and high N levels supplied either as a single bulk N application resembling N fertilization in field cultivation, or a steady-state N application according to Ingestad. The latter application strategy provided more stable and reproducible conditions for determination of genetic differences in NUE under low N conditions for a short-cycle leafy vegetable crop. Several tools for molecular genetic evaluation of NUE in spinach were provided as well, including a SNP marker set for marker-assisted breeding, a genetic mapping population with a corresponding genetic map, and the identification of two major QTL regions contributing to growth under low N conditions. With these tools, an efficient strategy for breeding for NUE efficiency in spinach would include screening under controlled conditions at high and low N using leaf area, biomass and root to shoot ratio as selectable traits, and QTL identification of genetic factors that can be targeted and combined using marker-assisted selection. An in depth genotype by environment interaction analysis using six field trials showed that environmental factors like temperature, soil, and management strongly influence nitrogen availability in the soil in a short cycle crop like spinach. This severely complicates selection and breeding for NUE of spinach under field conditions, and emphasizes the importance of performing trials under better controllable conditions for genetic dissection of NUE and discovery of genetic factors contributing to NUE. It also underscores the importance of validating these findings in various field trials. Multi-environment field trials with different levels of N fertilization will then allow selection of cultivars that combine stable performance under various low input growing conditions with high yields under more favorable conditions.

This literature review on mineral nutrition of cocoa was commissioned by the Scientific Committee of the Cocoa Fertiliser Initiative to address the following questions: What knowledge is currently available about mineral nutrition of cocoa? What are the current knowledge gaps? What are the key areas for further research?

This literature review on mineral nutrition of cocoa was commissioned by the Scientific Committee of the Cocoa Fertiliser Initiative to address the following questions: What knowledge is currently available about mineral nutrition of cocoa? What are the current knowledge gaps? What are the key areas for further research?

Nitrogen (N) efficiency in arable cropping systems can be improved when the expected N mineralization in soil during the growing season is accounted for in the N fertilizer recommendation. There are yet no standard procedures to estimate the amount o

Key words: Nitrogen, phosphorus, food chain, food pyramid, food system, food security, food cost, environmental impacts, nutrient cycling, nutrient management Nitrogen (N) and phosphorus (P) fertilizer applications have greatly contributed to the increased global food production during the last decades, but have also contributed to decreasing N and P use efficiencies (NUE and PUE) in the food production - consumption chain, and to increased N and P losses to air and water, with major ecological implications. The aim of this thesis is to increase the quantitative understanding of N and P flows and losses in the food production - consumption chain in China at regional level in the past 30 years and to develop strategies to increase NUE and PUE in the food chain. A novel ‘food chain’ approach and the NUFER model were developed to analyse N and P flows in crop production, animal production, food processing and retail, and households. Data were derived from statistical sources, literature and field surveys. Between 1980 and 2005, NUE and PUE decreased in crop production, increased in the animal production and decreased in the whole food chain. Total N losses to water and atmosphere almost tripled between 1980 (14.3 Tg) and 2005 (42.8 Tg), and P losses to water systems increased from 0.5 to 3.0 Tg. There were significant regional differences in NUE, PUE, and N and P losses; regions with high N and P losses were in Beijing and Tianjin metropolitans, Pearl River Delta, and Yangzi River Delta. Urban expansion is a major driving force for change; total N losses increased 2.9 folds, and P losses increased even 37 folds during the development of Beijing metropolitan, between 1978 and 2008. Scenario analyses indicated that implementation of a package of integrated nutrient management measures, combined with diet changes and increased imports of animal food and feed, are the most effective management options for increasing NUE and PUE, and for decreasing N and P losses. Application of the food chain approach and the NUFER model can help policy makers in China to plan food production - consumption chains, and thereby manage N and P flows in this chain at regional level.

A quadratic, a linear exponential and a linear plateau response model were compared in an analysis of the reaction of cauliflower yield to field applied nitrogen. For the pooled experiments the degree of fit with all three models considerably improved when the amount of mineral nitrogen in the soil layer 0?30 cm or 0?60 cm at planting was taken into account. This indicates that the crop can utilize the mineral nitrogen in the soil layer 0?60 cm at planting. With the linear exponential model, too high optima were estimated for the pooled experiments and no optima could be estimated in five out of the seven individual experiments. Application of the quadratic response model resulted in unrealistically high optimum fertilizer rates for both the pooled experiments and individual experiments. Optimum fertilizer rates in the individual experiments were best estimated using the linear plateau model. Excluding one experiment, a significant linear relationship was found between optimum fertilizer application and the amount of mineral nitrogen in the soil layer 0?60 cm at planting

Conservation agriculture (CA) and integrated soil fertility management (ISFM) practices are receiving increased attention as pathways to sustainable high-production agriculture in sub-Saharan Africa. However, little is known about the effects of these practices on arbuscular mycorrhizal fungi (AMF). The study aimed at understanding the long-term effects of (i) ISFM and CA on AMF communities and functioning, and on glomalin concentrations. The study also aimed at understanding the (ii) role of AMF in soil aggregation, plant nutrition and crop yield under field conditions and (iii) combined effect of AMF and earthworms on soil aggregation, plant nutrition and crop yield under greenhouse conditions. The study was conducted in two long-term field trials. The ISFM trial was in Kabete (central Kenya) and compared fertilization (nitrogen and phosphorus) and organic amendments (farmyard manure, crop residue) for 32 years, while the CA trial was in Nyabeda (western Kenya) and compared effect of tillage (conventional versus no-tillage), residue application, cropping system (monocropping versus rotation) and N-fertilization for 5 years. Long-term use of mineral fertilizer and organic amendments, as well as tillage and N fertilization altered AMF species composition, but the changes were relatively minor. Organic amendments alone or in combination with NP fertilization increased AMF incidence, whereas no-tillage in the presence of residue increased spore abundance and root colonization. N fertilization increased root colonization but had a negative effect on spore abundance and species richness. Crop rotation had no effect on AMF. Glomalin was also sensitive to management, but the response was site-specific. Glomalin responded more to CA in Nyabeda than ISFM in Kabete. N fertilization and residue increased glomalin, especially under conventional tillage. Path analysis indicated that AMF symbiosis and glomalin enhanced soil aggregation and crop nutrition and yield in both sites. The positive role of AMF on crop nutrition was stronger in Kabete than Nyabeda. However, yield and nutrient use efficiency were (very) low in Kabete. There was no interaction between AMF and earthworms on soil aggregation, but AMF enhanced soil aggregation. AMF interacted positively with the epigeic earthworm to enhance nutrient uptake and biomass production, but the endogeic earthworm negatively affected AMF symbiosis and function. The study highlights the potential of ISFM and CA practices in enhancing AMF diversity and activity, and indicates factors limiting AMF functioning under ISFM and CA systems. While AMF are important for agro-ecosystem functioning, remedying the non-responsive character of soils, especially Kabete, through judicious management of nitrogen and organic amendments remains a first priority.

The agronomic and environmental impacts of the production of mineral concentrate and its use as mineral nitrogen (N) fertilizer are examined in a pilot. In this pilot, the mineral concentrate is applied as fertilizer above the application standard for manure, but within the total N application standard (i.e. sum of effective N from manure and mineral fertilizer N) of the Nitrates Directive. The research in 2011 included monitoring of the manure treatment installations, incubation studies to assess immobilization and denitrification of soil-applied mineral concentrate, pot experiments to determine N efficiency of mineral concentrate under controlled conditions, and field experiments to determine N efficiency of mineral concentrate when used for grassland and arable crops. This report summarizes the main results of these studies. The research data will serve for consultation with the European Commission on a possible permanent permission to use mineral concentrate as mineral N fertilizer.

Conservation agriculture (CA) and integrated soil fertility management (ISFM) practices are receiving increased attention as pathways to sustainable high-production agriculture in sub-Saharan Africa. However, little is known about the effects of these practices on arbuscular mycorrhizal fungi (AMF). The study aimed at understanding the long-term effects of (i) ISFM and CA on AMF communities and functioning, and on glomalin concentrations. The study also aimed at understanding the (ii) role of AMF in soil aggregation, plant nutrition and crop yield under field conditions and (iii) combined effect of AMF and earthworms on soil aggregation, plant nutrition and crop yield under greenhouse conditions. The study was conducted in two long-term field trials. The ISFM trial was in Kabete (central Kenya) and compared fertilization (nitrogen and phosphorus) and organic amendments (farmyard manure, crop residue) for 32 years, while the CA trial was in Nyabeda (western Kenya) and compared effect of tillage (conventional versus no-tillage), residue application, cropping system (monocropping versus rotation) and N-fertilization for 5 years. Long-term use of mineral fertilizer and organic amendments, as well as tillage and N fertilization altered AMF species composition, but the changes were relatively minor. Organic amendments alone or in combination with NP fertilization increased AMF incidence, whereas no-tillage in the presence of residue increased spore abundance and root colonization. N fertilization increased root colonization but had a negative effect on spore abundance and species richness. Crop rotation had no effect on AMF. Glomalin was also sensitive to management, but the response was site-specific. Glomalin responded more to CA in Nyabeda than ISFM in Kabete. N fertilization and residue increased glomalin, especially under conventional tillage. Path analysis indicated that AMF symbiosis and glomalin enhanced soil aggregation and crop nutrition and yield in both sites. The positive role of AMF on crop nutrition was stronger in Kabete than Nyabeda. However, yield and nutrient use efficiency were (very) low in Kabete. There was no interaction between AMF and earthworms on soil aggregation, but AMF enhanced soil aggregation. AMF interacted positively with the epigeic earthworm to enhance nutrient uptake and biomass production, but the endogeic earthworm negatively affected AMF symbiosis and function. The study highlights the potential of ISFM and CA practices in enhancing AMF diversity and activity, and indicates factors limiting AMF functioning under ISFM and CA systems. While AMF are important for agro-ecosystem functioning, remedying the non-responsive character of soils, especially Kabete, through judicious management of nitrogen and organic amendments remains a first priority.

This report comprises the results of an explorative study on innovative nitrogen recovery from side streams of wastewater treatment plants (WWTPs) in the Netherlands. The main objective of the study was to identify promising new technologies for recovery of nitrogen which can be subsequently used as an artificial fertilizer. This shortcircuits the global nitrogen cycle and thereby reduces the environmental impact of the nitrogen cycle that has been distorted by human influence (eutrophication, greenhouse gases).

This report comprises the results of an explorative study on innovative nitrogen recovery from side streams of wastewater treatment plants (WWTPs) in the Netherlands. The main objective of the study was to identify promising new technologies for recovery of nitrogen which can be subsequently used as an artificial fertilizer. This shortcircuits the global nitrogen cycle and thereby reduces the environmental impact of the nitrogen cycle that has been distorted by human influence (eutrophication, greenhouse gases).

In a series of cutting experiments, average apparent nitrogen recovery of applied fertilizer N by Napier grass was approximately 50%. Incorporation of cattle manure improved nitrogen utilization. Mixtures with Desmodium intortum substantially improved yield and protein content. There was a fair to good relation between morphology and crude protein content and in vitro organic matter digestibility of Napier grass.

In a series of cutting experiments, average apparent nitrogen recovery of applied fertilizer N by Napier grass was approximately 50%. Incorporation of cattle manure improved nitrogen utilization. Mixtures with Desmodium intortum substantially improved yield and protein content. There was a fair to good relation between morphology and crude protein content and in vitro organic matter digestibility of Napier grass.

Data from 36 long-term field trials studying the effects of N on grass swards cut 5-6 times/year, with N fertilizer application split between cuts, were analysed to determine optimum N rates, the apparent soil N supply (ANS) and apparent N recovery i

Nitrogen (N) use in EU countries is regulated by so-called Action Programmes (APs) set by member states in response to the EU Nitrates Directive (ND). APs apply specifically to 'Nitrate Vulnerable Zones' (NVZs) within countries. More generally, the ND asks countries to define a Code of Good Agricultural Practice (GAP), outlining for their entire national territory what is considered responsible management of manures and fertilisers. This paper compares regulations on N use as precipitated in the APs (applicable in 2009) of Belgium (Flanders, FL), Denmark (DK), Germany (GE), France (FR) and The Netherlands (NL). For some countries, the AP includes maximum allowable N rates. Such statutory limits are called N application standards (NASs). NASs were derived from N fertiliser recommendations. Other elements addressed are 'closed periods' for animal manures; and the N fertiliser value (NFV) of manures, representing an equivalent amount of fertiliser-N relative to manure-N. Together, these elements (NASs, closed periods, and NFVs) constitute the core of rules and regulations. FL, DK, GE, and NL have designated their entire territories as NVZ and so their APs apply throughout. Limits to N use differ considerably between respective APs, both in definition and values. DK and NL have fixed, crop specific NASs regulating the sum of N in manures and fertilisers. NASs in FL are specified for total-N and fertiliser-N separately, and apply to crop groups. The German system is based on GAP and holds no NASs. It applies to all states. Nitrogen surplus on arable farms in GE, however, should not exceed 90 (2008) and 60 kg N per ha (2011). Legislation in FR does not hold limits on N input in general, nor in NVZs. Only in zones where the groundwater or surface water is used for drinking water - while nitrate concentration is high - is total N input (manures + mineral fertilisers) limited to 140-210 kg N per ha. Some regions (FL; Baden-Württemberg in GE) have separate limits for inorganic soil mineral N allowed in the autumn. NL, FL, DK, and GE have derogations for animal manures, allowing maximum rates between 200 and 250 kg N per ha. All derogations except for FL refer to grassland-dominated farms only.

Nitrogen (N) use in EU countries is regulated by so-called Action Programmes (APs) set by member states in response to the EU Nitrates Directive (ND). APs apply specifically to 'Nitrate Vulnerable Zones' (NVZs) within countries. More generally, the ND asks countries to define a Code of Good Agricultural Practice (GAP), outlining for their entire national territory what is considered responsible management of manures and fertilisers. This paper compares regulations on N use as precipitated in the APs (applicable in 2009) of Belgium (Flanders, FL), Denmark (DK), Germany (GE), France (FR) and The Netherlands (NL). For some countries, the AP includes maximum allowable N rates. Such statutory limits are called N application standards (NASs). NASs were derived from N fertiliser recommendations. Other elements addressed are 'closed periods' for animal manures; and the N fertiliser value (NFV) of manures, representing an equivalent amount of fertiliser-N relative to manure-N. Together, these elements (NASs, closed periods, and NFVs) constitute the core of rules and regulations. FL, DK, GE, and NL have designated their entire territories as NVZ and so their APs apply throughout. Limits to N use differ considerably between respective APs, both in definition and values. DK and NL have fixed, crop specific NASs regulating the sum of N in manures and fertilisers. NASs in FL are specified for total-N and fertiliser-N separately, and apply to crop groups. The German system is based on GAP and holds no NASs. It applies to all states. Nitrogen surplus on arable farms in GE, however, should not exceed 90 (2008) and 60 kg N per ha (2011). Legislation in FR does not hold limits on N input in general, nor in NVZs. Only in zones where the groundwater or surface water is used for drinking water - while nitrate concentration is high - is total N input (manures + mineral fertilisers) limited to 140-210 kg N per ha. Some regions (FL; Baden-Württemberg in GE) have separate limits for inorganic soil mineral N allowed in the autumn. NL, FL, DK, and GE have derogations for animal manures, allowing maximum rates between 200 and 250 kg N per ha. All derogations except for FL refer to grassland-dominated farms only.

Current systems of potato growing use large amounts of pesticides and fertilizers; these inputs are costly and cause environmental problems. In this paper a strategy for integrated low-input potato production is developed with the aim of reducing costs, improving product quality and reducing environmental damage. The strategy involves crop rotation, the use of cultivars with multiple resistance, modest fertilizer use (preferably based on organic manure) mechanical weed control, mechanical haulm destruction and limited use of pesticides. The prospects for this strategy are discussed

The aim of the present project (2008–2011) is to design selection criteria for high nitrogen use efficiency under low nitrogen conditions to support breeding programs for organic potato varieties.

The aim of the present project (2008–2011) is to design selection criteria for high nitrogen use efficiency under low nitrogen conditions to support breeding programs for organic potato varieties.

This report describes the results of Task 3 Promising measures to decreasing N losses from EU agriculture. The aim of Task 3 was (i) to identify a list of most promising measures to decrease N emissions and to make an in-depth assessment of the costs of these measures, using the models CAPRI and MITERRA-EUROPE

This report describes the results of Task 3 Promising measures to decreasing N losses from EU agriculture. The aim of Task 3 was (i) to identify a list of most promising measures to decrease N emissions and to make an in-depth assessment of the costs of these measures, using the models CAPRI and MITERRA-EUROPE

In a 5-year field experiment, a comparison was made between the manure application practices of two adjacent dairy farms in the north of the Netherlands. Grassland management systems at Drogeham and Harkema contrasted in manure application technique (surface application versus shallow injection, respectively), quality of applied manure (slurry + MX: slurry with Euromestmix® clay mineral additive versus regular slurry), and some relevant site characteristics (high versus low soil organic matter content and soil moisture supply). Effects of manure types and application techniques, and treatment of the soil with a micro-organism supplement, were tested in a factorial experiment at the two sites, two blocks per site, one with and one without additional application of 157 kg N ha−1 year−1 inorganic fertilizer. Apparent N recovery was higher after shallow injection than after surface application. For plots receiving no additional inorganic fertilizer, this difference was largest for slurry + MX applied at site Harkema, since this slurry-site combination resulted in the highest observed average apparent N recovery following shallow injection (47%) and the lowest N recovery following surface application (20%). For plots receiving additional inorganic fertilizer N the contrasts between treatments were less pronounced. Year effects on N uptake and dry matter production could be related to cumulative temperature and precipitation surplus over the growing season. A simple comparison between the grassland management systems was carried out based on the response curves derived from the experiment. This demonstrated that the grassland system where slurry was applied by shallow injection is not necessarily the lowest in actual amount of N not accounted for (i.e., potentially lost). The efficiency of the Harkema system strongly depended on high N recovery, but showed high potential losses in some years and a high herbage crude protein content in other years, due to the low DM production capacity. On the other hand, the Drogeham system was tuned to high DM production and was characterized by higher system stability, as reflected by more stable relationships between DM production and N not accounted for and herbage crude protein content. These differences between the systems were probably to a large extent caused by differences in water balance and soil organic matter content.

A combined conifer growth - soil water and nitrogen balance model was calibrated to simulate dry mass production and partitioning, water and nitrogen demand and nitrogen losses for Thuja occidentalis grown for two years on a sandy soil. Light interception was successfully described by the row-of-cuboids method. A diffusion model was used to describe fine root growth. The combined model was used to explore nitrogen losses under irrigation and fertilization strategies for optimal dry mass production. Irrigation was frequently necessary for optimal dry mass production and depended highly on the actual weather conditions. The recommended fertilizer applications were sufficient. Nitrogen losses always exceed the European nitrate N-limit in the year of planting and by 80% in the second growing season when optimal irrigated and fertilized for dry mass production. Therefore, additional measures are necessary to develop conifer cropping systems on sandy soils within the framework of the EU nitrate-N limit.

A combined conifer growth - soil water and nitrogen balance model was calibrated to simulate dry mass production and partitioning, water and nitrogen demand and nitrogen losses for Thuja occidentalis grown for two years on a sandy soil. Light interception was successfully described by the row-of-cuboids method. A diffusion model was used to describe fine root growth. The combined model was used to explore nitrogen losses under irrigation and fertilization strategies for optimal dry mass production. Irrigation was frequently necessary for optimal dry mass production and depended highly on the actual weather conditions. The recommended fertilizer applications were sufficient. Nitrogen losses always exceed the European nitrate N-limit in the year of planting and by 80% in the second growing season when optimal irrigated and fertilized for dry mass production. Therefore, additional measures are necessary to develop conifer cropping systems on sandy soils within the framework of the EU nitrate-N limit.

Intensive fertilisation practices in the Netherlands make it cumbersome to comply with the EU Nitrate Directive. Over the years, government has adopted increasingly strict environmental legislation, including the farm gate balance system MINAS (MINeral Accounting System) and a compulsory manure surplus contract system. The interactive research project named 'Farming with a future' was started in 2000 in order to assist the arable sector to comply with this legislation while maintaining its economic basis as much as possible. In the project, pilot farmers receive intensive guidance on appropriate ways to reduce their nutrient inputs and consequently nitrate leaching. The paper discusses the setting up of the project, which links commercial pilot farms to experimental farms with intensive process research. It provides results on nitrogen inputs, outputs and surpluses, as well as preliminary figures on nitrate groundwater concentrations, and ends with a short discussion on the prospects of the chosen approach

Intensive fertilisation practices in the Netherlands make it cumbersome to comply with the EU Nitrate Directive. Over the years, government has adopted increasingly strict environmental legislation, including the farm gate balance system MINAS (MINeral Accounting System) and a compulsory manure surplus contract system. The interactive research project named 'Farming with a future' was started in 2000 in order to assist the arable sector to comply with this legislation while maintaining its economic basis as much as possible. In the project, pilot farmers receive intensive guidance on appropriate ways to reduce their nutrient inputs and consequently nitrate leaching. The paper discusses the setting up of the project, which links commercial pilot farms to experimental farms with intensive process research. It provides results on nitrogen inputs, outputs and surpluses, as well as preliminary figures on nitrate groundwater concentrations, and ends with a short discussion on the prospects of the chosen approach

Mexican dairy farmers will face in the near future the challenge of increased competition and the strategy to survive this at farm level will have to be based on competitive free trade world prices. This thesis describes the design of a dairy system based on forages and grazing to reduce production costs in temperate Mexico. This dairy system is based on a sequential cropping system of permanent pastures of alfalfa and orchard grass, winter annual pastures of oats and annual ryegrass and silage maize. Between May and October the cows graze on permanent pastures and between November and April they graze both types of pastures. Between October and April the cows also receive supplementary feeding with maize silage. The cows are supplementarily fed with moderate amounts of concentrates during the lactation. The responses of stocking rate and milk production per hectare to increasing levels supplementary feeding with maize silage and concentrates were studied in two experiments. In both experiments a high and uniform pasture utilisation was targeted irrespective of the level of supplementary feeding. Milk production per hectare was more closely affected by changes in stocking rate than by changes in production per cow. Supplementary feeding with maize silage up to 4.8 kg DM of silage cow -1day -1and 4 kg of concentrate cow -1day -1appeared to be economically feasible. The right economic decision could not have been based on the response in milk production per cow to supplementary feeding. The allowance - intake relationship for dairy cows grazing oats and annual ryegrass pastures is reported. The responses of herbage intake and composition of the ingested herbage to different levels of herbage allowance were used to identify the levels of stocking rate and height of residual herbage that maximised production per unit of area. The number of bites taken per unit of area appeared to be an adequate variable to interpret the responses to herbage allowance. The effects of nitrogen fertilisation and irrigation on herbage and nitrogen yield of oats and ryegrass pastures were evaluated in a cutting trial. Nitrogen fertilisation between 50 and 100 kg N ha -1harvest -1increased herbage production, reduced the cost of produced herbage and improved the efficiency of utilisation of irrigation water. Using a high level of irrigation reduced the efficiency of utilisation of irrigation water and the recovery of fertilizer-N. However, increasing the frequency of irrigation increased the efficiency of use of absorbed N. The results of two years of operation (1998 and 1999) of the Farmlet for Dairy Production Under Grazing of Chapingo University are reported. The average stocking rate was 2.6 cows ha -1, the average production per cow was 6200 kg milk per lactation and the average productivity was 16 Mg milk ha -1year -1. Feeding costs in this dairy system were 43% lower than the average feeding costs in prevailing dairy systems. The net revenues (1273 US $ ha -1year -1) indicate that this dairy system is a feasible option. Based on these results, an improved pasture-crop rotation is proposed with a targeted productivity of 29 Mg milk ha -1year -1.

Mexican dairy farmers will face in the near future the challenge of increased competition and the strategy to survive this at farm level will have to be based on competitive free trade world prices. This thesis describes the design of a dairy system based on forages and grazing to reduce production costs in temperate Mexico. This dairy system is based on a sequential cropping system of permanent pastures of alfalfa and orchard grass, winter annual pastures of oats and annual ryegrass and silage maize. Between May and October the cows graze on permanent pastures and between November and April they graze both types of pastures. Between October and April the cows also receive supplementary feeding with maize silage. The cows are supplementarily fed with moderate amounts of concentrates during the lactation. The responses of stocking rate and milk production per hectare to increasing levels supplementary feeding with maize silage and concentrates were studied in two experiments. In both experiments a high and uniform pasture utilisation was targeted irrespective of the level of supplementary feeding. Milk production per hectare was more closely affected by changes in stocking rate than by changes in production per cow. Supplementary feeding with maize silage up to 4.8 kg DM of silage cow -1day -1and 4 kg of concentrate cow -1day -1appeared to be economically feasible. The right economic decision could not have been based on the response in milk production per cow to supplementary feeding. The allowance - intake relationship for dairy cows grazing oats and annual ryegrass pastures is reported. The responses of herbage intake and composition of the ingested herbage to different levels of herbage allowance were used to identify the levels of stocking rate and height of residual herbage that maximised production per unit of area. The number of bites taken per unit of area appeared to be an adequate variable to interpret the responses to herbage allowance. The effects of nitrogen fertilisation and irrigation on herbage and nitrogen yield of oats and ryegrass pastures were evaluated in a cutting trial. Nitrogen fertilisation between 50 and 100 kg N ha -1harvest -1increased herbage production, reduced the cost of produced herbage and improved the efficiency of utilisation of irrigation water. Using a high level of irrigation reduced the efficiency of utilisation of irrigation water and the recovery of fertilizer-N. However, increasing the frequency of irrigation increased the efficiency of use of absorbed N. The results of two years of operation (1998 and 1999) of the Farmlet for Dairy Production Under Grazing of Chapingo University are reported. The average stocking rate was 2.6 cows ha -1, the average production per cow was 6200 kg milk per lactation and the average productivity was 16 Mg milk ha -1year -1. Feeding costs in this dairy system were 43% lower than the average feeding costs in prevailing dairy systems. The net revenues (1273 US $ ha -1year -1) indicate that this dairy system is a feasible option. Based on these results, an improved pasture-crop rotation is proposed with a targeted productivity of 29 Mg milk ha -1year -1.

The fact that conventional agricultural practices have many detrimental effects is widely acknowledged (Rabbinge, 1997). To mitigate these effects, Dutch policy makers have implemented environmental laws that are essentially based on characteristic indicators for groundwater quality. This has resulted in progressively tighter restrictions on the input of N fertilisers and a consistent reduction of the number of registered pesticides. Enforcement of these laws still creates considerable problems, which is partly caused by their generic character: no provision is made for the significant variation among soil types. As this variation is well known to farmers, their affinity with the imposed rules and regulations is limited. This thesis follows a different approach, in which soil variability is placed at the starting point of research, using the techniques of precision agriculture. The objectives are:Develop a methodology that efficiently describes soil variability at the within-field level. Soil variability should be described in terms of functional properties that are directly relevant to farm management operations. In other words: describe soils in terms of their water regimes, nutrient cycling and sorption characteristics rather than using traditional taxonomic properties such as texture, soil organic matter (SOM) content and colour.Based on the above, develop methods to: (i) optimise the application of N fertiliser and (ii) evaluate and control the environmental risks associated with pesticide use. These methods should be developed through prototyping (Vereijcken, 1997) with ample attention for operational aspects.In line with the desired setting, research was conducted on a commercial arable farm in the central-western part of the Netherlands (51 o17'N, 4 o32'E). The farm covers an area of approximately 100 ha and applies a crop rotation of winter wheat, consumption potatoes and sugar beet. Soils originate from marine deposits, are generally calcareous and have textures ranging from sandy loam to clay. They are characterised as fine, mixed, mesic Typic Fluvaquents (Soil Survey Staff, 1998) or Mn25A-Mn45A on the Dutch 1:50,000 soil map (Vos, 1984). Soil variability is large and mainly expressed through differences in texture, soil organic matter (SOM) content and subsoil composition (peat or mineral matter). Drainage conditions are excellent and in general terms the area is considered prime agricultural land.In order to fully exploit the potential of precision agriculture, an understanding is required of the biophysical processes that govern the growth conditions of a crop. Simulation models provide a powerful tool in this respect and play a crucial role throughout this thesis. To maximize the accuracy of modelling results, much effort was invested in producing high-quality input data. Four methods were compared to derive soil hydraulic parameters from the basic soil properties collected in a 1,5000 soil survey of the study area. Applied methods included: (A) laboratory measurements, (B) class pedotransfer functions, (C) continuous pedotransfer functions and (D) continuous pedotransfer functions combined with simple laboratory measurements. Modelling performance was evaluated by comparing simulated and measured soil moisture contents for three sites and two depths. The combination of continuous pedotransfer functions and simple laboratory measurements (method D) clearly produced best results. Modelling performance was highest overall and results were consistent for individual profiles and depths. Modelling uncertainty was lowest, far lower than the uncertainty resulting from the measured data set. (Chapter 2)With the soil hydraulic parameters available, attention focused on describing soil variability. Soils were characterised in terms of simulated functional properties relating to water regimes and nutrient dynamics. Four properties were considered: water stress, N-stress, N-leaching and residual N-content at harvest. Sensitivity to water stress was evaluated for a dry year (1989); other properties were quantified for a wet year (1987). Based on functional similarity, individual soil profiles were grouped into functional classes. Standard interpolation techniques and a boundary detection algorithm subsequently identified soil functional units in each field. Analysis of variance revealed that over 65% of the spatial variation could thus be accounted for. This confirmed that soil characterisation had been efficient and that the resulting units were suitable entities to be used as management units for precision agriculture. (Chapter 3)Once the management units had been established, two field experiments were conducted to compare precision and conventional N management. The experiments were conducted in consecutive years (1998 and 1999) and on different winter wheat fields ( Triticum aestivum L.). Precision management used real-time simulations to monitor soil mineral N levels in each management unit. Early warning was provided when mineral N concentrations dropped below a critical threshold. Used as a trigger , this information served to optimise the timing of four consecutive N fertilisations. Fertiliser rates were determined through exploratory simulations, which calculated the amount of mineral N required under normal conditions. Compared to conventional management, fertiliser input was reduced by 15-27% without affecting grain yield. Grain quality was either not affected (1999) or significantly increased (1998; P&nbsp

The fact that conventional agricultural practices have many detrimental effects is widely acknowledged (Rabbinge, 1997). To mitigate these effects, Dutch policy makers have implemented environmental laws that are essentially based on characteristic indicators for groundwater quality. This has resulted in progressively tighter restrictions on the input of N fertilisers and a consistent reduction of the number of registered pesticides. Enforcement of these laws still creates considerable problems, which is partly caused by their generic character: no provision is made for the significant variation among soil types. As this variation is well known to farmers, their affinity with the imposed rules and regulations is limited. This thesis follows a different approach, in which soil variability is placed at the starting point of research, using the techniques of precision agriculture. The objectives are:Develop a methodology that efficiently describes soil variability at the within-field level. Soil variability should be described in terms of functional properties that are directly relevant to farm management operations. In other words: describe soils in terms of their water regimes, nutrient cycling and sorption characteristics rather than using traditional taxonomic properties such as texture, soil organic matter (SOM) content and colour.Based on the above, develop methods to: (i) optimise the application of N fertiliser and (ii) evaluate and control the environmental risks associated with pesticide use. These methods should be developed through prototyping (Vereijcken, 1997) with ample attention for operational aspects.In line with the desired setting, research was conducted on a commercial arable farm in the central-western part of the Netherlands (51 o17'N, 4 o32'E). The farm covers an area of approximately 100 ha and applies a crop rotation of winter wheat, consumption potatoes and sugar beet. Soils originate from marine deposits, are generally calcareous and have textures ranging from sandy loam to clay. They are characterised as fine, mixed, mesic Typic Fluvaquents (Soil Survey Staff, 1998) or Mn25A-Mn45A on the Dutch 1:50,000 soil map (Vos, 1984). Soil variability is large and mainly expressed through differences in texture, soil organic matter (SOM) content and subsoil composition (peat or mineral matter). Drainage conditions are excellent and in general terms the area is considered prime agricultural land.In order to fully exploit the potential of precision agriculture, an understanding is required of the biophysical processes that govern the growth conditions of a crop. Simulation models provide a powerful tool in this respect and play a crucial role throughout this thesis. To maximize the accuracy of modelling results, much effort was invested in producing high-quality input data. Four methods were compared to derive soil hydraulic parameters from the basic soil properties collected in a 1,5000 soil survey of the study area. Applied methods included: (A) laboratory measurements, (B) class pedotransfer functions, (C) continuous pedotransfer functions and (D) continuous pedotransfer functions combined with simple laboratory measurements. Modelling performance was evaluated by comparing simulated and measured soil moisture contents for three sites and two depths. The combination of continuous pedotransfer functions and simple laboratory measurements (method D) clearly produced best results. Modelling performance was highest overall and results were consistent for individual profiles and depths. Modelling uncertainty was lowest, far lower than the uncertainty resulting from the measured data set. (Chapter 2)With the soil hydraulic parameters available, attention focused on describing soil variability. Soils were characterised in terms of simulated functional properties relating to water regimes and nutrient dynamics. Four properties were considered: water stress, N-stress, N-leaching and residual N-content at harvest. Sensitivity to water stress was evaluated for a dry year (1989); other properties were quantified for a wet year (1987). Based on functional similarity, individual soil profiles were grouped into functional classes. Standard interpolation techniques and a boundary detection algorithm subsequently identified soil functional units in each field. Analysis of variance revealed that over 65% of the spatial variation could thus be accounted for. This confirmed that soil characterisation had been efficient and that the resulting units were suitable entities to be used as management units for precision agriculture. (Chapter 3)Once the management units had been established, two field experiments were conducted to compare precision and conventional N management. The experiments were conducted in consecutive years (1998 and 1999) and on different winter wheat fields ( Triticum aestivum L.). Precision management used real-time simulations to monitor soil mineral N levels in each management unit. Early warning was provided when mineral N concentrations dropped below a critical threshold. Used as a trigger , this information served to optimise the timing of four consecutive N fertilisations. Fertiliser rates were determined through exploratory simulations, which calculated the amount of mineral N required under normal conditions. Compared to conventional management, fertiliser input was reduced by 15-27% without affecting grain yield. Grain quality was either not affected (1999) or significantly increased (1998; P&nbsp

Keywords: chickweed, early growth, leaf area expansion, light interception, light use efficiency, manure, mineralisation, modelling, organic farming, organic matter, soil nitrogen content , Solanum tuberosum L., specific leaf area , Stellaria media (L.) Vill. , Triticum aestivum L, weed suppression .Understanding how to obtain good yields and farm profits in arable organic farming systems is useful for conventional and integrated farming to decrease the current reliance on pesticides and mineral fertilisers. Two issues are of particular importance for organic farming: organic nitrogen (N) management and weed management.Optimisation of organic N management is complex because N directly affects crop growth and yield, and indirectly affects pests, diseases and weeds. Yields in organic farming are known to be 0-50% lower than in conventional farming, but it is unclear to what extent this is due to direct effects of N on growth. N management may also influence growth and reproduction of late-emerging weeds. Although they do not directly damage the crop, they may cause long-term weed management problems due to replenishment of the seed bank.The direct effects of N management on crop growth and yield of the target crops potato and wheat, and on establishment and reproduction of late-emerging weeds were investigated in a series of field experiments. Yield under organic N management strategies was explored with a model for crop growth and N dynamics in crop and soil. Nitrogen applied by slurry in amounts currently used in organic farming was found to limit growth of potato and wheat from emergence onwards. Early N limitations caused a linear decrease in the rate of early foliar expansion, while the light use efficiencies of the crops were hardly affected. Early foliar expansion rates with sufficient N were studied in more detail because they are an important base to calculate N-limited expansion rates. A combination of experiments and simulations showed that early foliar expansion rates with sufficient N could best be predicted when driven by temperature from emergence onwards up to a leaf area index of 1 for potato and 1.5 for wheat, after which they were driven by radiation. Model explorations showed that potato tuber yields under organic N management varied considerably with timing of slurry application, weather conditions and crop maturity class, and that low yields were associated with early N shortages. Increased N supply decreased reproduction of late-emerging Stellaria media in potato, but increased that in wheat. It is concluded that a basic dressing of an organic N source with a large proportion of mineral N could improve crop yields in organic farming, while row application of such manure may favour the crop relative to the weed.

Keywords: chickweed, early growth, leaf area expansion, light interception, light use efficiency, manure, mineralisation, modelling, organic farming, organic matter, soil nitrogen content , Solanum tuberosum L., specific leaf area , Stellaria media (L.) Vill. , Triticum aestivum L, weed suppression .Understanding how to obtain good yields and farm profits in arable organic farming systems is useful for conventional and integrated farming to decrease the current reliance on pesticides and mineral fertilisers. Two issues are of particular importance for organic farming: organic nitrogen (N) management and weed management.Optimisation of organic N management is complex because N directly affects crop growth and yield, and indirectly affects pests, diseases and weeds. Yields in organic farming are known to be 0-50% lower than in conventional farming, but it is unclear to what extent this is due to direct effects of N on growth. N management may also influence growth and reproduction of late-emerging weeds. Although they do not directly damage the crop, they may cause long-term weed management problems due to replenishment of the seed bank.The direct effects of N management on crop growth and yield of the target crops potato and wheat, and on establishment and reproduction of late-emerging weeds were investigated in a series of field experiments. Yield under organic N management strategies was explored with a model for crop growth and N dynamics in crop and soil. Nitrogen applied by slurry in amounts currently used in organic farming was found to limit growth of potato and wheat from emergence onwards. Early N limitations caused a linear decrease in the rate of early foliar expansion, while the light use efficiencies of the crops were hardly affected. Early foliar expansion rates with sufficient N were studied in more detail because they are an important base to calculate N-limited expansion rates. A combination of experiments and simulations showed that early foliar expansion rates with sufficient N could best be predicted when driven by temperature from emergence onwards up to a leaf area index of 1 for potato and 1.5 for wheat, after which they were driven by radiation. Model explorations showed that potato tuber yields under organic N management varied considerably with timing of slurry application, weather conditions and crop maturity class, and that low yields were associated with early N shortages. Increased N supply decreased reproduction of late-emerging Stellaria media in potato, but increased that in wheat. It is concluded that a basic dressing of an organic N source with a large proportion of mineral N could improve crop yields in organic farming, while row application of such manure may favour the crop relative to the weed.

Nitrogen (N) efficiency in arable cropping systems can be improved when the expected N mineralization in soil during the growing season is accounted for in the N fertilizer recommendation. There are yet no standard procedures to estimate the amount o De stikstof (N-) efficiëntie van akkerbouwsystemen als onderdeel van duurzame landbouw. Verslag van een studie waarin verschillende chemischer en biologische indicatorene voor N-mineralisatie zijn getest voor 15 verwchillende gronden. Gegevens in bijgaande tabellen: karakteristieken van de gronden die in het onderzoek zijn gebruikt; korte beschrijving van de verschillende methoden; mineralisatie in de potproef, incubatieproef en reactorproef, hot KCL extraheerbare NH4, potentiële denitrificatie (DNP) en N-verlies bij verhitten tot 350 graden Celcius; correlatiecoëfficienten voor de verschillende indicatoren voor mineralisatie. Alle waarden zijn logaritmisch getransformeerd

This book contains 10 articles on the EU research project COGANOG (Controlling Gaseous Nitrogen Oxide Emissions from Grassland Farming Systems in Europe). The papers present the results of studies on the effects of liming and N fertilizer application