Future prospects for large farms located in lorraine on clayed soils and limestone compounds (rendosols)

From a concrete case located in a small natural area of Lorraine (Haye), the interest of an agro-eco-pedological study was highlighted. After observations of the ground (pedological charts on various scales), physical-chemical and isotopic analyses and output analysis determined by GPS, it became possible : 1) to simulate the potentialities of a farm or of a piece of land located in this area, 2) to determine the importance of compartmentalized heterogeneity on the outputs in order to modulate the use of fertilizers, 3) to outline the socioeconomic consequences according to the foreseeable climate evolutions.A partir d'un cas concret et localisé dans une petite région naturelle de Lorraine (Haye), il a été mis en évidence l'intérêt d'une étude agro-écopédologique. A la suite d'observations de terrain (cartes pédologiques à différentes échelles), d'analyses physico-chimiques et isotopiques et de la détermination des rendements par GPS, il devient possible: 1) de simuler les potentialités d'une exploitation ou d'une parcelle située dans cette région, 2) de déterminer l'importance de l'hétérogénéité parcellaire sur les rendements et donc de moduler les fertilisants, 3) d'esquisser les conséquences socio-économiques sur les exploitations en fonction des évolutions climatiques prévisibles

Influence of the soil climate on the evolution of the nitrogenous compounds in the soils of Lorraine and their consequences on the water quality

In order to establish the influence of the soil climate on the transfer mechanisms of the element N, under naturally constituted forms or industrial syntheses, in soil, water, plant systems, we put in place in the fields two procedures. The first concerned the cultivated sites of the four main types of soil found in Lorraine. The annual lixiviation of nitrates beyond the Ap level can be large and go beyond 100kg / ha of N.NO3 -. It varies according to the soils, the year and the season and we observe that the nitrates are mainly lixiviated in autumn. The values obtained in-situ, compared to those of the potential mineralization in controlled conditions, show the importance of the interaction between climactic parameters and biophysical chemical properties of the soils intervening on the mineralization of the endogenous nitrogen stocks thus the risks of lixiviation notably between crops. Then on a light chalk/clay soil, the burying of a carbon substrate (hop) in end of season, allowed a limitation to the annual lixiviation of the nitrates of about 25%. The use of a fertilizer marked under controlled conditions, allowed us to see the formation of different sections of the internal cycle of the nitrogen and the bio availability of this fertilizer for a spring crop while allowing for the risks of enrichment in nitrate ions in the underlying waters. This study allowed us to establish the participation of the fertilizer in the possible risks of a pollution of nitrates to a level of 21%; also to underline the importance of the duration of the microbic biochemical immobilizations of fertilizers given to these four types of soils; finally, we observe a variety of the kinetic of remineralization from the newly-formed different organic azotes.Afin de préciser l'influence du pédoclimat sur les mécanismes de transfert de l'élément azote (sous formes de composés naturels ou de composés issus de synthèses industrielles) dans les systèmes sols, eaux, plantes, nous avons mis en place plusieurs protocoles. Dans le premier les horizons cultivés des quatre principaux types de sols lorrains ont été pris en considération et soumis aux mêmes contraintes climatiques. La lixiviation des nitrates au-delà de l'horizon Ap est importante et peut dépasser annuellement 100 kg/ha de N.NO-3. Elle varie selon les sols, l'année et la saison et nous constatons que les nitrates sont majoritairement lixiviés en automne. Les valeurs obtenues in situ, comparées à celles du potentiel de minéralisation en conditions contrôlées, montrent toute l'importance de l'interaction entre les paramètres climatiques et les propriétés bio-physico-chimiques des sols sur l'expression de la minéralisation des réserves azotées endogènes, donc de leur potentiel de lixiviation. Un second protocole a permis de mettre en évidence une limitation de la lixiviation des nitrates d'environ 25 % suite à l'enfouissement automnal d'un substrat carboné (paille d'orge). L'utilisation d'un engrais marqué, nous a permis d'observer l'évolution des différents compartiments du cycle interne de l'azote et de leur biodisponibilité pour une céréale de printemps tout en prévoyant les risques d'enrichissement en ions nitrate des eaux sous jacentes. Cette étude a permis de préciser la participation de l'engrais à la pollution nitrique à hauteur de 21% et de souligner toute l'importance de l'immobilisation microbienne des engrais par le sol. Enfin, sous conditions contrôlées, nous montrons les variations de l'immobilisation des engrais apportés et surtout de leur cinétique de reminéralisation en fonction du pédoclimat

Influence de l'apport de composés organiques sur l'adsorption et la désorption des ions phosphates en sol ferrallitique

International audienc

Transformations of nitrogen fertilizers in brazilian amazonia soils

We have compared the effect of15N urea and15N ammonium sulfate on the process of stabilization in organic matter and mineralization in three soils of central Amazonia, classified as Oxisol, Ultisol, and low-humic gley. During the first month of incubation in the laboratory, the nitrogen fertilizer amendment slightly increased mineralization of organic nitrogen in both acid soils (Oxisol and Ultisol). In these soils, 60% of the nitrogen added was recovered as NH4* after 2 months incubation, while in the low- humic gley soil, 50% of the applied nitrogen was nitrified. The incorporation of15N fertilizer in the organic matter of the latter soil was higher (30%) than in the acid soils. Incorporation in the acid soils, though low, was more important for N derived from urea than ammonium sulfate. For the Oxisol, nitrogen incorporation in organic matter values varied between 12% and 19%, and 7-9% for the Ultisol. © 1995 Taylor & Francis Group, LLC

Efficiency of nitrogen-15-labelled fertilizers for rice and rye-grass cultivated in an Ultisol of Brazilian Amazonia

The objective of this study was to determine the efficiency of two N fertilizers, (NH4)2SO4 and urea, for rice (Oryza sativa L.) and rye-grass (Lolium multiflorum L.) cultivated in an Ultisol of central Amazonia using 15N as a tracer. Rice was cultivated in the field, while rye-grass was grown in a phytotron. Fertilization with (NH4)2SO4 caused a 16% increase in the yield of rice grains and urea a 36% increase. In both crops total N uptake and N use efficiency of the fertilizers were higher for urea than for (NH4)2SO4. The low values for N derived from fertilizer showed that the fertilizers contributed little to the total N absorbed by the plants. The 'priming effect' or positive added N interaction (ANI) between the fertilizer N and soil organic N was observed, especially with urea. Immobilization by soil microorganisms was greater in the presence of urea, while losses were always higher with the (NH4)2SO4 treatments. These losses were significant, and their reduction should allow more efficient use of this N fertilizer. It is possible that the N use efficiency was higher for urea due to a pH increase, caused by urea hydrolysis, which in turn may have favoured the activity of nitrifying bacteria in this extremely acid soil