Les cultures intermédiaires pièges à nitrate (CIPAN) et engrais verts : protection de l'environnement et intérêt agronomique

Autumn cover crops and green manures: environment protection and agronomic interest. Due to the evolution of the environmental policy, practice of green manure cropping has been replaced by autumn cover crops in order to take up nitrate residues of the soil. These crops (mustard, phacelia, rye-grass, rye) show a high ability to take up N (sometimes more than 100 kg N.ha-1), leading to a decreasing threat for nitrate leaching. Such an ability is however related to species, but also to cropping practices mainly sowing date. Subsequent mineralization (measured with labeling 15N technic) of this organic-green manure-N, influenced by physical and chemical characteristics of the ploughed biomass, seems however limited (less than 45% of N ploughed in the soil) and does not lead obviously to a reduction of the N advice for the following crop. Nevertheless, stocking of organic N and C in the soil is expected to have a beneficial long-term effect on both mineralization (providing more N) and soil humus content leading to improve structural properties of soil

Perspectives d'amélioration du conseil prévisionnel de fertilisation azotée à la parcelle en Wallonie par l'utilisation du logiciel AzoFert®

Prospects for improving the provisional nitrogen fertilization recommendation at field scale in Wallonia using the AzoFert® software. The French software AzoFert® for nitrogen fertilization recommendation is currently under adaptation and validation for soil and climatic conditions in Wallonia by the CRA-W within the INTERREG IV project "SUN" (Sustainable Use of Nitrogen). This adaptation has raised the need for a change of values in the parameter tables and catalogs relating to meadow residues, crop residues, catch crop practices, crops, organic amendments and soil type. Data from 25 trials of increasing nitrogen fertilizer rates conducted by CRA-W between 1996 and 2011 in cereal, potato and vegetable crops located on loam and sandy loam soil were used to validate the AzoFert® software adapted for Wallonia. The difference between nitrogen rates recommended on the one hand by AzoFert® or Azobil® (software currently used in the reference lab for Nitrate [Requasud] at CRA-W) and the optimal dose of nitrogen fertilizer assessed in each trial on the other hand shows that, in most cases, AzoFert® gives a recommendation closer to the optimum than Azobil®. The nitrogen uptake measured in the plants collected in the unfertilized control plot also shows a higher correlation with nitrogen supply from the soil assessed by AzoFert® than for plants assessed by Azobil®. The more accurate estimate of the mineralization of organic sources, probably linked to the dynamic soil nitrogen supply approach integrated into AzoFert®, may explain the gain in the greater accuracy of the AzoFert® recommendation in comparison with that of Azobil®

Effet de la date d'épandage sur l'efficience et le devenir de l'azote du lisier appliqué en prairie permanente en Haute Ardenne

Efficiency and fate of slurry N applied to permanent grass in Ardenne (Belgium) – Effect of the choice of spreading period. In Haute Ardenne and Pays de Herve, areas devoted to grass, slurry represents the main source of nitrogen; slurry is applied on permanent pasture. This paper aims to compare the nitrogen efficiency of cattle slurry with that of mineral fertilizers and to determine the influence of the choice of spreading period on N use by grasses. Results from two long terms trials and from one in micro plots using stable 15N are presented. Results show that the fertilizers applied (organic and mineral) only affected at a mean level of 25% N absorbed by grassland. The efficiency of spring slurry applications carried out in favorable spreading conditions matched those of mineral N. From our results, it can be concluded that N losses in grasslands are very low and are due to volatilization just after the spreading of slurry

Optimization of extracellular catalase production from Aspergillus phoenicis K30 by a linear regression method using date flour as single carbon source and purification of the enzyme

Aspergillus phoenicis K30 is the selected mutant which produces an amount of extracellular catalase. To amplify the extracellular catalase production by the strain, a fermentation optimization was performed. To select the factors affecting the production, nine active variables (factors) consisting of 12 experiments were analyzed by Plackett-Burman design. Each variable was tested at two levels, a higher and a lower level. The studies of the effect of each variable and the establishment of a correlation between the response of enzyme activity and variables revealed that the link is a multiple linear regression form. The optimization was carried out through a simplex algorithm. The amount of extracellular catalase produced by the strain in the optimized medium was about four times higher than that obtained in non optimized medium corresponding to 3820 mg/L of extracellular proteins including 59500 U/L of extracellular catalase activity after 96 h of fermentation. The steps of purification were allowed to improve enzyme activity by 305-fold. From an analytical gel electrophoresis under native conditions, an apparent molecular mass of 158 kDa was determined suggesting that the enzyme is a homodimer. The isoelectric point of the protein was found to be 5 ± 0.1 as determined by a Pharmacia Phast-system.Keywords: Aspergillus phoenicis, extracellular catalase purification, dates flour, optimization, multiple linear regression.African Journal of Biotechnology Vol. 12(19), pp. 2646-265

L'isotope stable 15N et le lysimètre, des outils complémentaires pour l'étude de la lixiviation de l'azote dans les sols agricoles

Stable 15N isotope and lysimeter, complementary tools in order to study the nitrogen leaching in agricultural soils. Stable 15N was used in lysimetric trials conducted with the aim to study nitrate leaching of agricultural soils. At Gembloux, a rate of 200 kg N.ha-1 as 15NH4 15NO3 with an isotopic abundance of 2.161 At%15N was applied in two lysimeters before a spinach crop, followed by beans and winter wheat; in the first lysimeter, total recovery by crops was less than 39.8% while in second lysimeter, recovery was 62.2%. Concentrations of N-NO3 - in leached water were always higher in lysimeter 2 than lysimeter 1, probably due to less microbial immobilization of nitrogen. At Remicourt and Omal, a simulated mineral residue of 150 kg N.ha-1 (rate of 15NH4 15NO3 applied in autumn) has completely disappeared from the soil profile (0-90 cm) already in July of the following year. At Omal, a winter crop has recovered no more than 9% of nitrogen rate applied in autumn. Measurement of N-NO3 - concentration in leached water has shown clearly higher levels at Remicourt (even more than 70 mg N.l-1 probably caused by an application of high rate of compost rich in nitrogen) than is Omal. Stable 15N isotope could not be analyzed in leaching water probably due to a leak of sensitiveness of the analytical equipment

Etude des paramètres opératoires de pressage mécanique des amandes de Vitellaria paradoxa Gaertn C.F. (karité)

Study of the operational parameters of mechanical pressing of almonds of Vitellaria paradoxa Gaertn C.F. (shea tree). Sheabutter is one of the most difficult oleaginous resources to extract by traditional way. In Burkina Faso, where production of sheanuts is estimated at 70000 tons per year, presses manufactured locally are used to improve the production. In order to optimize the handcraft process of sheabutter production, extraction parameters of Vitellaria paradoxa Gaertn C.F. were studied under laboratory controlled conditions on 3 g samples of ground almonds using a uni-axial compression test machine specifically instrumented for this purpose. The studied operational parameters were the grinding (unsieved sample 0.5 mm<Ø<5 mm ; sieved samples 0.5 mm<Ø<1 mm ; 1 mm<Ø<2 mm ; 2 mm<Ø<4 mm ; 4 mm<Ø<5 mm), the heating temperature (30; 50; 70; 90; 110; 130; 150°C) and the extraction pressure (7; 10; 13.4; 15; 16.17; 17.44; 20; 22.43 and 25 MPa). The grinding has favourably influenced the extraction rate. The finest sieved fraction (0.5 mm<Ø<1 mm) presented the highest extraction rate, 84%. When using unsieved samples, the best results were obtained with a heating temperature of 90°C and an extraction pressure of 20 MPa. In these conditions, the extraction rate reached 78% and the chemical characteristics of the sheabutter were not altered. As a result, a significant increase of the handcrafted presses efficiency could be reached by simple and inexpensive modifications as an increase of the pressure applied to the product, by a decrease of the pressing chamber diameter