Across the United States, high tunnels are used as a means of season extension and control over climatic variability in fruit and vegetable production. However, high tunnel systems are an intensive form of agricultural production which may compromise soil and crop quality over time. This study examined the effects of the varying environmental conditions, created in two types of tunnel system, movable and stationary, on the flow of nitrogen from amendment to plant and impact on crop and soil quality parameters. The way nutrients cycled through these systems was different and the nutrient treatments had no consistent effects on soil nutrient parameters, although some microbial groups were affected by the nature of the nutrient amendment. No exposure to rainfall resulted in an accumulation of leachable NO3 in the stationary tunnels. Spinach yields were superior to those in a previous study at the same site however, leaf NO3 levels consistently exceeded EU maximum limits for fresh-sap leaf NO3. We cannot conclude from our data if there was a compromise of crop or soil quality in the high tunnel production systems and further investigation is necessary as high tunnels gain in popularity and make a larger footprint on the agricultural landscape.

Little research has been done in the humid mid-Atlantic region to develop full-season N fertilizer recommendations for dryland no-tillage grain sorghum (Sorghum bicolor L. Moench) production. The objectives of this study were: (i) to determine the optimum rate of band-placed starter N fertilizer needed in combination with side-dress N applications to achieve economic grain yields, (ii) to investigate if pre-plant broadcast N applications are as efficient as band-placed plus side-dress N applications, (iii) to evaluate the response of grain sorghum yield to partitioned side-dress N applications, and (iv) to study the influence of residual soil profile mineral-N (nitrate and ammonium) on sorghum response to applied N fertilization. Multi-location field studies were conducted over three years. A range of N treatments of various starter-band and side-dress N rates were applied. The experimental data indicate that an optimum rate of N fertilization depends on residual soil mineral-N. Little or zero starter-band-N in conjunction with side-dress-N applications of 130 kg of N ha-1 for soils testing high in mineral-N ( 50 kg N ha-1 in the top 0.3m of surface soil) at planting, and a starter-band-N supplement of 40 kg N ha-1 in conjunction with 130 kg N ha-1 side-dress N for soils testing low in mineral-N at planting, optimized the grain sorghum yields in these experiments. Broadcast N applications were observed to be as efficient as band placed N applications when followed by rainfall soon after application. Grain sorghum yields did respond to the partitioned side-dress N applications. However, partitioning of side-dress N application again depends on the residual mineral-N level present in the soil. In order to consider residual soil mineral-N in making N fertilizer recommendations "Associated Nitrogen Fertilizer Equivalency" (ANFE) values were calculated. ANFE is the amount of applied N that has potential to produce the same yield as that produced by the residual soil mineral-N. The N fertilizer recommendations based on ANFE values were quite close for two out of four sites as compared to the N rates at which the maximum yields were obtained in this study. / Ph. D.

L’Agriculture de conservation (AC) repose sur trois principes: le minimum de travail du sol, la couverture permanente du sol et la diversification des espèces cultivées. Elle a été introduite vers la fin des années 90 dans la région du lac Alaotra, Madagascar, dans l’objectif d’augmenter la productivisté de l’agriculture pluviale qui, généralement, pâtit des problèmes liés à la faible fertilité des sols, aux contraintes hydriques et à l’enherbement. L’objectif principal de la thèse consiste à quantifier et caractériser les impacts des fonctions agro-écologiques de l’AC dans l’amélioration du rendement en riz pluvial par rapport aux pratiques conventionnelles (CT). Une revue de la littérature sur les fonctions agro-écologiques du mulch en fonction de leur quantité retenue sur la parcelle a tout d’abord montré que la quantité de couverture nécessaire va dépendre essentiellement des fonctions agro-écologiques attendues. Une quantité de couverture de 2 à 3 t ha-1 permet d’obtenir des effets très nets en ce qui concerne l’amélioration de l’infiltration de l’eau, la limitation du ruissellement et de l’érosion du sol. En revanche, les données sur le contrôle de l’enherbement, la disponibilité des nutriments ainsi que la faune du sol en fonction de la quantité de mulch étaient très variables, suggérant l’interaction de ses fonctions agro-écologiques avec d’autres facteurs, notamment le type de résidus et les conditions pédoclimatiques. Une première expérimentation dont l’objectif était la quantification des effets physiques du mulch sur l’enherbement, avec différentes quantités de résidus de 0 à 45 t ha-1 a montré que l’émergence et la biomasse des adventices sur les parcelles couvertes dépend essentiellement de la quantité et de la distribution de la pluviométrie durant la saison culturale. L’émergence ainsi que la biomasse des mauvaises herbes diminuent en général avec l’augmentation de la quantité de mulch maintenue sur les parcelles. Toutefois, une quantité de résidus de l’ordre de 10 t ha-1 est nécessaire pour réduire significativement la pression des adventices sur le riz par rapport à un sol nu dans les conditions de notre dispositif expérimental. Un deuxième dispositif maintenu durant 6 ans (2009/10 à 2014/15), combinait une rotation biennale de maïs + dolique // riz et une rotation triennale de maïs + stylosanthes // stylosanthes // riz ; trois modes de gestion du sol et des résidus et deux niveaux de fertilisation. Deux niveaux d’enherbement en split plot ont été ajoutés en 2013/14 et 2014/15. L’amélioration du rendement en riz sur les parcelles en AC par rapport aux parcelles en CT est essentiellement liée à une diminution de la pression des adventices sur les parcelles AC pendant la période de végétation du riz. La dynamique de l’eau dans le sol ainsi que la dynamique de l’azote minéral sont fortement influencées par le régime pluviométrique et ne différent généralement pas entre AC et CT. Enfin, l’analyse de stabilité et l’écart de rendement au potentiel utilisés pour étudier les variations de rendements en riz sur les 6 saisons culturales du second dispositif expérimental ont montré que les effets des traitements étaient en interaction avec d’autres facteurs probablement liés à la variabilité spatiale du sol sur le dispositif expérimental. Les résultats de cette étude nous suggèrent de tenir compte aussi bien des fonctions agro-écologiques du mulch attendues que les régimes pluviométriques lors de la promotion d’un système AC pour améliorer la productivité des cultures. L'AC avec une quantité de résidus généralement retenus dans les parcelles de l'agriculteur (i.e. 1 - 2 t ha-1) serait efficace pour lutter contre le ruissellement et l'érosion. Cependant, des quantités supplémentaires de résidus, qui pourraient être produites avec l’introduction de rotations culturales avec une forte production de biomasse, seraient nécessaires pour lutter efficacement contre les adventices et diminuer les charges liées au sarclage. / Conservation agriculture (CA) is based on the principles of minimum soil disturbance, permanent soil cover and diversification of crop species grown in rotations and/or associations. CA was introduced in the late 90s in the Lake Alaotra region, Madagascar, in order to improve rainfed crop productivity which is commonly constrained by low soil fertility, soil water stress and weed infestation. The main objective of this study was to quantify and understand the impact of CA on rainfed rice productivity as compared to the practice of conventional tillage (CT). First, a review of literature was conducted on the agro-ecological functions of mulching with crop residues in relation to their quantity. The literature review showed that the optimal amount of residues required principally depends on the agro-ecological function searched for. Residue amounts of 2 to 3 t ha-1 had clear positive effects in terms of improving water infiltration and limiting water runoff and soil erosion. On the other hand, results on weed control, nutrient availability and soil fauna in relation to the amount of mulch were highly variable, suggesting the interaction of these agro-ecological functions with other factors, including residue type and soil-climate conditions. Second, two field experiments were monitored at the research center of FOFIFA in the Lake Alaotra region. A first experiment aiming at quantifying the physical effect of a mulch of crop residues on weed infestation, with amounts of surface residues ranging from 0 to 45 t ha-1 showed that the emergence and biomass of weeds on mulched plots depend mainly on the quantity and distribution of rainfall during the cropping season. Overall, weed emergence and biomass decreased with increasing amounts of mulch. However, a large quantity of residues, i.e. in the order of 10 t ha-1, was required to significantly (p<0.05) reduce weed pressure as compared to a bare soil under the agro-ecological conditions of our experiments. The second experiment was conducted during six years (2009/10 to 2014/15), and a 2-year rotation of maize + Dolichos lablab // rice and a 3-year rotation of maize + Stylosanthes guianensis // S. guianensis // rice were combined with three soil/residue management practices and two level of fertilization. Two levels of weed pressure were added as split-plot in 2013/14 and 2014/15. Higher rice grain yields on CA plots as compared to CT plots in the fifth and sixth year of the CA practice were mainly related to a decline of weed pressure under CA. Soil water and mineral nitrogen dynamics did not differ markedly between CA and CT and were strongly influenced by the rainfall pattern. Finally, the use of the concept of stability analysis and the yield gap approach to analyze the variation of rice yield under the 6 crop seasons from 2009/10 to 2014/15 showed that the effects of treatments including crop rotation, soil and residue management, and fertilization levels interact with other factors likely related to the spatial variability of the experimental design. Results of our study suggest that both agro-ecological function of mulch searched for and rainfall conditions should be taken into account when promoting CA systems to improve crop productivity in the Lake Alaotra region. Practicing CA with typical amounts of residues that are produced on farmer’s field (i.e. 1 – 2 t ha-1) is sufficient to control water runoff and soil erosion. However, extra amounts of crop residues are required to effectively control weed infestation. These extra amounts could be produced with the introduction of high biomass-producing crop rotations and could decrease the labor pressure from weeding.

L’utilisation des Produits Résiduaires Organiques (PRO) par l’agriculture peut permettre de substituer une partie des engrais minéraux et augmenter les niveaux de matière organique des sols. Elle peut également générer des pollutions azotées via la lixiviation de nitrate ou des émissions gazeuses. Mieux connaitre le devenir du carbone (C) et de l’azote (N) après applications de PRO sur les sols agricoles contribue à améliorer les bénéfices de cette pratique et à en limiter les impacts environnementaux. Cette thèse a pour objectif: (i) de prédire les dynamiques du C et du N en cas d’applications de PRO sur les sols agricoles, (ii) d’étudier les effets de scenarios d’apports de PRO sur les stocks de carbone dans les sols, la substitution des engrais azotés et les pollutions azotées dans le contexte du territoire de la Plaine de Versailles, en prenant en compte la diversité des sols, de leurs teneurs en C et des successions culturales, (iii) d’améliorer ces bénéfices à l’échelon du territoire via une distribution optimale des PRO. Le modèle CERES-EGC a été utilisé pour simuler les effets de 13 ans d’apports de PRO sur les dynamiques de C et de N dans le système sol-plante-atmosphère de l’expérimentation QualiAgro, située au cœur du territoire d’étude. Le sous-modèle NCSOIL a été paramétré à partir de cinétiques de minéralisation de C et N mesurées en conditions contrôlées de laboratoire. Le transfert de ces paramètres dans CERES-EGC a permis de simuler correctement les évolution des stocks de carbone dans les sols, les rendements et les prélèvements de N par les cultures ainsi que l’évolution des stocks de N minéral dans les sols. Les dynamiques de minéralisation de C et N des 18 PRO disponibles sur le territoire ont été déterminées. NCSOIL a été paramétré à partir des caractéristiques analytiques et des résultats de fractions biochimiques des PRO. Les types de sol du territoire n’ont pas impacté significativement le paramétrage. Les PRO ont été classés selon 4 types : (1) composts stables, (2) composts moins matures restant plus réactifs et les fumiers stables, (3) des fumiers très réactifs correspondant à des fumiers de chevaux, (4) des PRO très réactifs tels que des boues et des fientes pouvant plutôt être utilisés comme fertilisants. De nombreux scenarios d’apport de PRO, contraints par les flux de phosphore et de N apportés, ont été simulés sur 20 ans dans tous les contextes de sols, successions culturales et teneurs en C organique des sols du territoire. Le type de sol a impacté le plus le stockage de C et les lixiviations de nitrate tandis que les successions culturales étaient prépondérantes sur la substitution des engrais. Des composts ont permis de stocker 1.1 t C ha- 1 an-1 allant jusqu’63% du C apporté. Des substitutions de 74 kg N ha-1 an-1 ont été atteintes avec une boue mais aussi un compost en prenant en compte la substitution des engrais liée aux augmentations de matière organique dans les sols. La substitution des engrais a pu atteindre plus de 90% du N apporté par les PRO, ceci étant lié aux arrières-effets sur le stockage de matière organique dans les sols et dépendant des hypothèses de calcul de la substitution des engrais azotés. Un modèle d’optimisation a été développé pour sélectionner les scenarios d’apports de PRO pour chaque ilot du territoire (sol x succession de culture x teneur en C organique initiale x surface) tenant compte de la disponibilité des PRO et avec pour objectif de maximiser le stockage de C ou les substitutions en engrais azotés ou de minimiser la lixiviation de nitrate au niveau du territoire. En apportant préférentiellement les PRO les plus stables sur les sols à fort potentiel de stockage de C (fortes teneurs en argile et calcaire), jusqu’à 0.47 t C ha-1 an- 1 pourrait être stocké. En appliquant préférentiellement les PRO fertilisants sur les successions à maïs, et les PRO amendants sur les successions à colza jusqu’à 53 kg N ha-1 an-1 de N de synthèse pourrait être économisés. / The use of Exogenous Organic Matter (EOM) in agriculture could be an efficient way to substitute mineral fertilisation and increase soil organic matter (SOM) enhancing soil fertility and storing carbon (C). It could also cause nitrogen (N) pollutions such as nitrate leaching and gas emissions. Better understanding of C and N fate after EOM applications on cropped soils would allow improving these benefits while limiting environmental impacts. This thesis aims at: (i) predicting EOM impacts when applied on cropped soils, (ii) studying the effects of various scenarios of EOM applications in terms of C storage, synthetic N saving and N pollutions in the context of the Plain of Versailles region (221 km²) and taking into account soil diversity, crop successions and soil organic C contents, (ii) studying the potential for improving these benefits at the regional scale with an optimal distribution of EOM. The CERES-EGC crop model was used to simulate the effects of repeated applications of EOM over 13 years on both soil C and N dynamics in the soil-crop-water-air system of the long-term field experiment QualiAgro located within the region. The sub-model NCSOIL was parameterised from C and N mineralisation kinetics of EOM measured in laboratory conditions. When transposing the parameters into the CERES-EGC model, C storage at the field scale was well simulated, together with crop N uptake and yields, as well as soil mineral N contents. The kinetics of C and N mineralisation of the 18 EOM available in the region were used along with EOM biochemical fractionations for parameterising the NCSOIL model. The soil type did not significantly change EOM parameters. Four groups of EOM were distinguished based on their C and N dynamics: (i) stable composts, (2) more reactive and less mature composts and stable manures, (3) manures with reactive OM corresponding to horse manures and (4) very reactive EOM as sludges, litters that should be used as fertilisers. Numerous scenarios of EOM applications, constrained on the phosphorus and N quantities they bring (and limiting the input in trace elements), were simulated for 20 years in all regional contexts of soil, crop successions and soil organic C contents. The soil type was the main factor controlling C storage and N leaching while it was crop successions for N saving. Some composts allowed C storage up to 1.1 t C ha-1 yr -1 reaching 63% of C applied. N saving of 74 kg N ha-1 yr -1 were possible with a dried sewage sludge and a compost. N substitution could reach more than 90% of N applied with EOM, these high percentages being related with the indirect effect of EOM on soil OM and the hypothesis made for N substitution An optimisation model was developed to select EOM application scenario for each crop plot (soil x crop succession x initial soil OC content x area) accounting for EOM availability in the region with the objectives of maximising C storage or synthetic N saving or minimising N leaching at the regional scale. Applying preferentially the most stable EOM on soils with the highest potential for C storage i.e. with the highest calcareous and clay contents, up to 0.47 t C ha-1 yr-1 could be stored. Applying preferentially fertilising EOM on crop succession with maize and amending EOM on succession with rapeseed, up to 53 kg N ha-1 yr -1 could be saved.

Submitted by Claudia Rocha (claudia.rocha@udesc.br) on 2018-03-08T14:08:25Z No. of bitstreams: 1 PGCS17MA161.pdf: 277204 bytes, checksum: 295ae0923cdfa15e00efc516619613f4 (MD5) / Made available in DSpace on 2018-03-08T14:08:25Z (GMT). No. of bitstreams: 1 PGCS17MA161.pdf: 277204 bytes, checksum: 295ae0923cdfa15e00efc516619613f4 (MD5) Previous issue date: 2016-12-21 / Capes / The revegetation of degraded areas is a fundamental recovery strategy to improve the physical and chemical attributes of the soils, besides providing through the vegetation cover, the necessary protection to reduce the loss of sediments due to water erosion. The present work had the objective of evaluating the revegetation of a degraded area that originated a slope with soil de - tailing within the CAV / UDESC Agroveterinary Sciences Center, from isolated and intercropping of summer forage species in association with organic / mineral fertilization And mineral fertilization. The experimental design was in randomized blocks with subdivided plots, with 9 treatments and 4 replications. The main treatments were arranged in the subplots, being: isolated cultivation of Brachiaria decumbens, isolated Crotalaria spectabilis cultivation, and intercropped Brachiaria + Crotalaria intercrop. The secondary treatments were arranged in the plots, and they refer to fertilization, they are: fertilization with bed of aviary supplemented with mineral fertilization, mineral fertilization (N-P-K) and without fertilization (control). At the beginning and at the end of the experiment, soil samples were collected to verify the changes in their chemical attributes. In the chemical analyzes were determined the pH and the contents of N, P, K, Ca, Mg, Al, Organic matter and organic C. The soil was previously scarified and the pH corrected in all plots, as a result of soil chemical analysis. The fertilizations followed the recommendations of the CQFS (2004) and were applied in the subplots. The sowing was in line with spacing of 20cm between rows, totaling 5 rows per subplot. Plant samples were collected from the three central lines of each subplot. The accumulation of fresh and dry mass of the aerial part and the nutrient contents were determined: nitrogen, phosphorus and potassium (N, P, K, Ca and Mg) present in the dry matter. The results were submitted to analysis of variance and comparison of means by Fisher DMS test, at a significance level of 5%. The isolated cultivation of brachiaria and consortium showed the highest production of biomass and dry mass of aerial part. Crotalaria presented the highest concentrations of N, P, Ca, and Mg in plant tissue. The contents of K in the plant tissue showed interaction between fertilization and species, and the fertilization effect was significant for brachiaria and consortium, which accumulated the highest levels in the plots without fertilization (control). Crotalaria and consortium presented the highest concentrations of K in the fertilized plots with bed of birds and crotalaria had the highest concentration in the plots fertilized with mineral fertilizer (N-P-K). It was verified that the revegetation of the degraded area, associated to liming and fertilization, improved some soil chemical attributes, such as: elevation of pH, increase of Mg, K, P, organic matter and organic carbon; And Al reduction. However, it was not possible to determine differences in terms of improvement of soil chemical conditions related to organic fertilization / A revegetação de áreas degradadas é uma estratégia de recuperação fundamental para melhorar os atributos físicos e químicos dos solos, além de fornecer através da cobertura vegetal, a proteção necessária para diminuir a perda de sedimentos por erosão hídrica. O presente trabalho teve por objetivo avaliar a revegetação de uma área degradada que originou um talude com solo decapeado dentro do Centro de Ciências Agroveterinárias CAV/UDESC, a partir do cultivo isolado e consorciado de espécies forrageiras de verão, em associação com adubação orgânica/mineral e adubação mineral. O delineamento experimental utilizado foi em blocos casualizados com parcelas subdivididas, com 9 tratamentos e 4 repetições. Os tratamentos principais foram dispostos nas subparcelas, sendo eles: cultivo isolado de capim-braquiária (Brachiaria decumbens), cultivo isolado de crotalária (Crotalaria spectabilis) e cultivo consorciado capim-braquiária + crotalária. Os tratamentos secundários foram dispostos nas parcelas, e referem-se à adubação, são eles: adubação com cama de aviário complementada com adubação mineral, adubação mineral (N-P-K) e sem adubação (testemunha). No início e ao final do experimento foram efetuadas coletas de solo para verificar as alterações ocorridas nos seus atributos químicos. Nas análises químicas foram determinados o pH e os teores de N, P, K, Ca, Mg, Al, Matéria orgânica e C orgânico. O solo foi previamente escarificado e o pH corrigido em todas as parcelas, conforme resultado da análise química do solo. As adubações seguiram as recomendações do CQFS (2004) e foram aplicadas nas subparcelas. A semeadura foi em linha com espaçamento de 20cm entrelinhas, totalizando 5 linhas por subparcela. As amostras de plantas foram coletadas das três linhas centrais de cada subparcela. Foi determinado o acúmulo de massas fresca e seca da parte aérea e os teores de nutrientes: nitrogênio, fósforo e potássio (N, P, K, Ca e Mg) presentes na matéria seca. Os resultados foram submetidos à análise de variância e comparação de médias por teste de DMS de Fisher, ao nível de significância de 5%. O cultivo isolado de braquiária e consórcio apresentaram a maior produção de biomassa e de massa seca de parte aérea. A crotalária apresentou as maiores concentrações de N, P, Ca, e Mg no tecido vegetal. Os teores de K no tecido vegetal apresentaram interação entre adubação x espécie, sendo que o efeito adubação foi significativo para braquiária e consórcio que acumularam os maiores teores nas parcelas sem adubação (testemunha). Crotalária e consórcio apresentaram as maiores concentrações de K nas parcelas adubadas com cama de aves e crotalária teve a maior concentração nas parcelas adubadas com fertilizante mineral (N-P-K). Verificou-se que a revegetação da área degradada, associada a calagem e a adubação, melhorou alguns atributos químicos do solo, como: elevação do pH, aumento dos teores de Mg, K, P, matéria orgânica e carbono orgânico; e redução Al. Contudo, não foi possível determinar diferenças em termo de melhoria das condições químicas do solo, relativas a adubação orgânica

Zielsetzung dieser langjährigen experimentellen Untersuchungen war eine komplexe Prüfung folgender ökologischer landwirtschaftlicher Anbauformen mit unterschiedlich hohem Tierbesatz unter den klimatischen Bedingungen von Ostdeutschland: Standorte Spröda (Sandboden, Ackerzahl 30), Methau (Lößboden, Ackerzahl 63); Anbausysteme und Betriebsformen: Marktfruchtbau (Leguminosenaufwüchse werden gemulcht, Koppelprodukte verbleiben auf dem Acker), Futterbau (Leguminosenaufwüchse und Koppelprodukte werden vom Feld abgefahren); Düngemittelarten und -höhe: Stalldung, Grüngut (Mulch) aus Leguminosengras, Rindergülle; organische Düngung mit 0 – 2 DE/ha u. Jahr, mineralische N-Dünger (kleiner Umfang zum Vergleich). In dem vorliegenden Forschungsbericht wurde eine Gesamtauswertung der Dauerversuche über die langfristigen Wirkungen von über 80 Merkmalen zur Entwicklung der Erträge, Qualität und Vitalität der Fruchtarten und Fruchtfolgen, Merkmalen der Bodenfruchtbarkeit der Ackerkrume und im Tiefenprofil sowie bestimmten Umweltwirkungen vorgenommen. Die Versuche haben eine Darstellung der Ergebnisse über ein weites Spektrum an Anbauverfahren ermöglicht, die bewusst auch über das übliche Maß des Ökolandbaus hinausgehen. Das Intensitätsniveau reichte von einer niedrigen Nährstoffversorgung in den viehlosen Marktfruchtvarianten ohne Düngung bis zu einer sehr hohen Versorgung in den intensiven Futterbauvarianten. In einer umfangreichen Diskussion wurden die Grenzen und die Möglichkeiten zur Weiterentwicklung des Ökolandbaus in Folge einer gesteigerten Intensivierung durch Leguminosenanbau (Körner- u. Futterleguminosen) sowie flüssigen und festen organischen Düngern für eine optimale Gestaltung und Ertragsbildung der Fruchtfolgen und der Umweltverträglichkeit detailliert aufgeführt.:1 Einleitung 2 Darstellung und Abgrenzung der Fragestellungen 3 Material und Methoden 3.1 Standortbeschreibung 3.2 Boden 3.3 Witterung 3.4 Versuchsdesign 3.5 Fruchtfolgen 3.6 Düngung 3.7 Versuchsdurchführung und Feldprobenahme 3.8 Bodenuntersuchung 3.9 Düngemitteluntersuchungen 3.10 Pflanzenuntersuchungen 3.11 Berechnungswerkzeuge 4 Ergebnisse und Interpretation 4.1 Erträge der Fruchtarten 4.2 Inhaltsstoffe und Qualitätsparameter der Fruchtarten 4.3 Nährstoffgehalte des Bodens 4.4 Nährstoffbilanzen und -effizienzen 4.5 Ermittlung von zeitlichen Veränderungsraten an Humus und Bodennährstoffen in Relation zur Veränderung der Fruchtartenerträge 4.6 Relationen zwischen Salden und der Bodenveränderung an Nährstoffen sowie Strategien zur Verbesserung der Aussagefähigkeit der Nährstoffbilanzierung im Marktfruchtsystem 4.7 Relation zwischen Nährstoffzufuhr, Nährstoffbereitstellung über Mineralisation und Nährstoffbedarf der Fruchtarten 4.8 Komprimierte Darstellung der Wirkung von Standort, Anbausystem und Düngung 5 Diskussion und Schlussfolgerungen 5.1 Überblick 5.2 Möglichkeiten und Grenzen steigender Intensivierung im Ökolandbau und deren Umweltwirkung 6 Zusammenfassung 7 Danksagung 8 Literatur 9 Anhang