This study aimed at determining the fate of trace elements (TE) following soil organic waste (OW) application. We used a unique combination of X-ray absorption spectroscopy analyses, to determine TE speciation, with incubation experiments for in situ monitoring of TE availability patterns over a time course with the technique of the diffusive gradients in thin films (DGT). We showed that copper (Cu) and zinc (Zn) availability were both increased in OW-amended soil, but their release was controlled by distinct mechanisms. Zn speciation in OW was found to be dominated by an inorganic species, i.e. Zn sorbed on Fe oxides. Zn desorption from Fe oxides could explain the increase in Zn availability in OW-amended soil. Cu speciation in OW was dominated by organic species. Cu release through the mineralization of organic carbon from OW was responsible for the increase in Cu availability. (Résumé d'auteur)

Organic waste (OW) reuse in agriculture is a common practice fostered by benefits in terms of waste recycling and crop production. However, OW amendments potentially affect the fate of pesticide spread on fields to protect the crops from pests and weeds. The influence of OW on the sorption, degradation, and leaching of pesticides is generally studied for each mechanism separately under artificial laboratory conditions. Our study aims at evaluating the balance of these mechanisms under more realistic conditions to clarify the influence of three common OW amendments on the fate, in soil, of the widely used herbicide S-Metolachlor. We performed leaching experiments in large undisturbed soil cores amended with raw sewage sludge, composted sludge, and digested pig slurry (digestate), respectively. We monitored S-Metolachlor and its two main metabolites MET-OA and MET-ESA in the leachates during a succession of 10 rainfall events over 126 days. We also quantified the remaining S-Metolachlor and metabolites in the soil at the end of the experiments. S-Metolachlor leaching didn't exceed 0.1% of the applied dose with or without OW amendment. Despite a soil organic carbon increase of 3 to 32%, OW amendments did not significantly affect the amount of S-Metolachlor that leached through the soil (0.01 to 0.1%) nor its transformation rate (6.0 to 8.6%). However, it affected the degradation pathways with an increase of MET-OA relative to MET-ESA formed after OW amendment (28 to 54%) compared to the controls (8%). Concentration of S-Metolachlor and metabolites in the leachates of all treatments greatly exceeded the regulatory limit for groundwater intended for human consumption in Europe. These high concentrations were probably the consequence of preferential macropore flow. Colloids had comparable levels in the leachates after S-Metolachlor application. Dissolved organic carbon was also comparable in the controls, digestate, and sludge treatments but was 65% higher in the compost-amended cores. These results, along with a great variability among replicates inherent to experiments performed under realistic conditions, partly explain the limited impact of OW on the transport of S-Metolachlor

L’azote, si cher à nos campagnes

High fertilizer input is necessary to sustain high yields in oil palm agroecosystems, but it may endanger neighboring aquatic ecosystems when excess nutrients are transported to waterways. In this study, the hydrochemical dynamics of groundwater and streams under baseflow conditions were evaluated with bi-monthly measurements for 1 year on 16 watersheds. Hydrochemical measurements were related to the spatial distribution of soil and fertilization practices across a landscape of 100 km2, dominated by oil palm cultivation, in Central Sumatra, Indonesia. The low nutrient concentrations recorded in streams throughout the landscape indicated that the mature oil palm plantations in this study did not contribute to eutrophication of aquatic ecosystems. This was ascribed to high nutrient uptake by oil palm, a rational fertilizer program, and dilution of nutrient concentrations due to heavy rainfall in the study area. Soil type controlled dissolved inorganic N and total P fluxes, with greater losses of N and P from loamy-sand uplands than loamy lowlands. Organic fertilization helped to reduce nutrient fluxes compared to mineral fertilizers. However, when K inputs exceeded the oil palm requirement threshold, high K export occurred during periods when groundwater had a short residence time. For higher nutrient use efficiency in the long term, the field-scale fertilizer management should be complemented with a landscape-scale strategy of fertilizer applications that accounts for soil variability. (Résumé d'auteur)

Nitrogen (N) is an input essential to agriculture which produces plant but also animal proteins. N cycle is a biological complex cycle, with biological fixation converting atmospheric unreactive di-nitrogen into many reactive nitrogen forms (Nr), essential for life. Nr forms are implicated in many transformations in air, water and soil, as well as within living organisms, until recovering to the N2 form through denitrification. These natural processes were amplified by the development of industrial husbandry and the massive use of N industrial fertilizers, making N expensive for forffarmers. Furthermore, its management in agriculture and its low efficiency in plant production and even more in animal production lead to losses to the environment. The most mediatized one is nitrate lixiviation with its impacts on water quality. N losses to atmosphere have become a matter of concern for the French public authorities since about twenty years, for their impacts on greenhouse balance (nitrous oxide N2 0), air quality and ecosystems and biodiversity (ammonia NH3 , and nitrogen oxides NOx). The costs of abatement strategies are more or less amortized thanks to the profits realized in economy (N expenses in agriculture) and for society (human health, global changes…). | L’azote (N) est un intrant indispensable à une agriculture productrice de protéines végétales mais surtout animales. Le cycle de l’azote est un cycle biogéochimique complexe, dont l’essentiel des entrées dans la biosphère est constitué par la fixation biologique. Toutes les formes d’azote chimiquement et biologiquement actives constituent l’azote dit réactif. Il l’eau et le sol, ainsi qu’au sein des êtres vivants, allant jusqu’au retour à sa forme diazote par la dénitrification. Ces processus naturels ont été amplifiés par le développement de l’élevage industriel et le recoursmassif aux engrais industriels azotés. Or l’azote coûte cher financièrement aux agriculteurs, et sa gestion en agriculture génère des rejets vers l’environnement liés aux faibles rendements d’utilisation de l’azote par les végétaux et surtout par les animaux. Les rejets les plus médiatisés sont les nitrates, avec les impacts sur la qualité des eaux. Les pertes vers l’atmosphèrepréoccupent les pouvoirs publics français depuis une vingtaine d’années, du fait de leurs impacts sur le réchauffement global de l’atmosphère (protoxyde d’azote, N2 0) mais aussi sur la qualité de l’air (ammoniac NH3 , et oxydes d’azote NOX). Les parades pour réduire les émissions de ces polluants et gaz à effet de serre ont également un coût, plus ou moins amorti selon lescomposés émis et/ou les postes émetteurs concernés grâce aux bénéfices économiques (poste azote en agriculture) et sociaux (santé humaine, changements globaux…) réalisés.

Fertilization plays an essential role in forest management on the site being under air pollution load in last years. The soil acidity due to the acid fall-out is markedly worse and at the same time the concentration of calcium, phosphorous, potassium and magnesium are decreasing. The fertilization besides positive influence on height increment could help in adaptation process of plants establishment after transplanting and it can eliminate negative ifluence of anthropogenic conditions of the environmnet