Robert Oliver

Prediction by near infrared spectroscopy of the composition of plant raw materials from the organic fertiliser industry and of crop residues from tropical agrosystems

The dynamics of carbon (C) and nitrogen (N) of plant residues and organic fertilisers are of great interest for agricultural and global warming studies. The proportion of the fractions obtained from biochemical analyses (fibres by sequential Van Soest analysis) can be used for predicting both C and N transformation of organic materials in soils. Considering the expensive and time-consuming Van Soest method, the principal aim of this study was to elaborate near infrared (NIR) calibrations for fibres, in order to use them for consecutive studies (for example, our works on transformation of added organics or TAO model). A wide set of organic fertilisers and their raw materials was sampled, including plant materials originating from temperate (especially Mediterranean) and tropical regions. The particular objective of this work was to build NIR calibrations for fibre fractions, along with C and N content, in plant materials used in the organic fertiliser industry and green house gases mitigating strategies. The second particular objective was to test for two levels of validation of the equations previously elaborated: (1) validation with a set of randomly chosen samples that was not considered during the calibration step, (2) extrapolation of the predictive capacity of the equations when applying them to outliers that were previously discarded. The fibres were the best predicted parameters, as R² = 0.95, 0.91, 0.97, 0.97 for neutral detergent soluble, hemicelluloses, cellulose and lignin, respectively, whereas the characteristics of total organic matter had R² varying from 0.87 (N Kjeldahl) to 0.94 (C Dumas). The accuracy of the calibrations developed for fibres was confirmed by the first level of validation, since the standard errors of prediction were close to the corresponding standard errors of cross-validation and the standard errors of calibration. Nevertheless, the calibrations developed for ash and C Dumas were not so good. Surprisingly, at the second level of validation, some outliers were not so badly predicted. This can illustrate the robustness of the calibrations for cellulose, lignin and, to a lesser extent, N Dumas which are key parameters for our modelling works on C and N transformation of added organics in soils.

Efficiency of nitrogen fertilizer in the sugarcane-vertical system in Guadeloupe according to growth and ratoon age of the cane

Sugarcane is one of the main economic resources of Guadeloupe (France). Cane grown on the islands vertisols shows nitrogen deficiency which is accentuated with each successive ratoon. This deficiency could partially explain the observed decrease in yield. The present study, based on the isotopic N method applied to different ratoons in the field, was aimed at: (i) diagnosing the problem in the crop environment itself; and (ii) quantifying the fertilizer-N balance. The results indicated that decrease in yield and N absorption by the cane was related to ratoon number. The real utilization coefficient for the fertilizer (RUC%) ranged from 6 and 34%, and a high proportion (30–40%) of fertilizer-N was immobilized in the soil (NiS%) after the annual crop cycle. The N absorbed by the cane was essentially derived from the soil. Rainfall at the beginning of (re)growth determined crop development and N supply to the crop. When the water requirements of the crop are satisfied, nitrogen supply and cane yield can be improved in two ways: (i) by increasing the efficiency of the applied N fertilizer (RUC% and NiS%); and (ii) by maintaining the soils capacity to supply cane with N. This implies maintaining and, if necessary, upgrading the structural state of the vertisols.

Carbon Sequestration in a Savannah Soil in Southwestern Burkina as Affected by Cropping and Cultural Practices

Soil organic matter (SOM) plays a dominant role in soil fertility and in the reduction of greenhouse gas emissions. The way in which land is managed directly influences SOM. The objective of this work was twofold: (1) to evaluate the potential storage of C in a plinthic luvisol in southwest Burkina Faso under three different management methods—natural savannah vegetation, continuous cropping without manure and continuous cropping with manure; and (2) to examine the factors (chemical, physical and management) determining C storage in the soil. The methodology used in the field was characterization of the environment by soil mapping, measurement of bulk density, and soil sampling. In the laboratory, the determination of the soil physical and chemical characteristics and measurement of C and N contents and particle size distribution of the SOM were accomplished. The results show that the C content in the top 30 cm was 61 Mg ha−1 under savannah as compared to 16 Mg ha−1 under continuous cropping, with the C being present mainly in the surface layer. Cow manure applied at 2 Mg DM ha−1 yr−1 for 13 years led to an increase of 9 Mg C ha−1. Particle size analysis showed that: (a) the carbon content was highest in the clay size fraction, and (b) the method of soil management mainly influenced the C content of the coarse fractions (200–2000 μm) and the fine fractions (0–20 μm) at the surface.

Litter Production and Soil Fertility in a Vitellaria paradoxa Parkland in a Catena in Southern Mali

Many authors have expressed concerns about the evolution of soil fertility under cotton and cereal cultivation in southern Mali. Nevertheless, farmers have now cropped some of their fields for more than 30 years and still obtain fair yields. Our hypothesis is that the trees (mainly Vitellaria paradoxa) that farmers keep in their cropped fields help to maintain soil fertility. Consequently, we studied the relationships between the trees associated with crops and soil fertility on a sloped catena. On the lower section, 24 trees ha−1 cover 8% of the surface. They produce annually ∼56.7 kg of leaves per tree. Corresponding mineral recyclings, under the crown, are, per m2 and per year: 19 g N; 1 g P; 19 g K; 29 g Ca; 10 g Mg. The soil contains significantly more C and N under the crown of the trees than outside this area. V. paradoxa trees are less numerous on the middle section (3 ha−1) and on the top section (1.5 ha−1) of the catena than on the lower section, and consequently, their effect on the soil is decreasing from the lowlands to the uplands. On the lower section of the catena, the trees have an impact on the fertility of the whole field. Therefore, farmers intensify the cultivation in this section, which is the more favorable section of the catena.

Changes in organic matter of a ferrallitic tropical soil degraded by cropping systems: the case of southern Senegal.

Understanding of the mechanisms involved in the restoration of degraded soils is necessary in order to assess the sustainability of a cropping system. For this purpose, an 8-year experiment was set up to test the efficiency of four cropping systems involving applications of fertilizer and/or manure and incorporation of crop residues and/or fallows on the regeneration of a Haplic Acrisol degraded by about 90 years of traditional cropping (groundnut-millet rotation without any input). The supply of nitrogen by the soil and particle size and chemical distribution were measured and used to characterize the soil organic matter (SOM) after 2 and 8 years of treatments, and then related to nutrients uptake. Two of the four cropping systems tested that were expected to regenerate soil fertility (Q1 and Q2: 4-year rotations including a plowed-in fallow, incorporation of crop residues, and mineral fertilization) both had a depressive effect on SOM content, although the losses of total C and N observed during the experiment (e.g .,-23% N and -20% N for Q1 and Q2, respectively) were less than that for the control (traditional cropping B, -33% N). Only the multiyear fallow did not result in further degradation of SOM, without, however, enriching the soil. On the other hand, an annual application of 10 Mg dry matter of manure ha -1 , combined with fertilizer, markedly increased the SOM (total N increased by factor 2 after only 2 years), an effect that seemed, however, stabilized at the end of the 8 years. Only a strong (10 Mg dry matter ha -1 ) and annual supply of manure, associated with mineral fertilization, had a positive effect on SOM, but its durability is not established.

Alley cropping of maize and Gliricidia sepium in the Sudanese Sahel region: some technical feasibility aspects.

An association in an alley cropping experiment of a short-term maize variety and a tree legume (Gliricidia sepium) adapted to the Sudanese Sahel region was studied from the point of view of the nitrogen balance and plot yields. Isotopic labelling applied in the field enabled the contribution to maize nitrogen nutrition from different nitrogen sources (fertilizer, prunings, and soil) to be quantified. For equal cultivated areas, alley cropping provides a maize yield greater than that of maize grown in pure stand without nitrogen fertilizer. However this yield is only 40% of that obtained in pure stands with fertilizer nitrogen. Alley cropping gives a very favourable Land Equivalent Ratio (LER) of 0.90 and 1.58 compared with N-fertilized and non-N-fertilized plots, respectively. These LERs demonstrate the increased biological efficiency of the cultivated soil in an agroforestry system. The percentage of the total nitrogen in the maize coming from prunings (Nfdp) varies between 30 and 35% and the true coefficient of nitrogen utilization of the prunings (TCUp) varies from 15-25%. In the environment of central Senegal, the percentage of total nitrogen of G. sepium coming from N 2 fixation is quite low (Ndffix = 25%), and consequently, in the maize, the nitrogen coming from N 2 fixation (Ndffix) is only 8%. It is therefore necessary to improve the efficiency of nitrogen fixation of G. sepium in this zone to assure the sustainability of the agroforestry system.

Developing Indicators for Soil and Fertilizer Nitrogen Use Efficiency for Maize Using On-Farm Experiments in Burkina Faso

Measurement of recovery of fertilizer N and soil mineral N by maize must be improved in the western semiarid tropics for maximizing crop yield and reducing environmental pollution. The relevant variables for characterizing this N use are the N uptake by the plant from the applied fertilizer (NdfF) and that from the soil (NdfS). The direct measurement of these two variables requires the use of 15 N labeled fertilizer, a difficult and expensive technique. It would therefore be useful to have sensitive indicators for these variables. This study was conducted to measure the variability in the N use from soils. The experiments were carried out with maize at 24 sites in a 3000 ha area of village land with Luvisols located in the central zone of Burkina Faso. Each site had two treatments with two replicates: 0 and 80 kg N ha −1 applied as urea labeled with 15 N. Statistical analysis of the results identified three groups of fields differing in soil fertility, each corresponding to a certain distance from the farmstead, and provided a relationship between the variables NdfF, NdfS, and easily measured indicators. The most pertinent indicators (r 2 >0.9) were: (a) for NdfS, the total N in plant without fertilizer (Nplt0) and the apparent crop recovery of N fertilizer (ACR %), and (b) for Nplt0, Nav (available N) as measured by the Waring Bremner test, exchangeable K, and (c) the clay content. The coefficients of determination improved when the regressions were calculated for each soil fertility group. These results have two important applications: (a) the possibility of estimating easily the part of N taken up by maize that comes, respectively, from the soil and the fertilizer; and (b) the identification of two factors limiting soil fertility, that is, the mineral N and exchangeable K + content of the soil before cropping.

Phase II screening study of a LHRH analogue, dexamethasone and somatostatin analogue versus LHRH analogue with dexamethasone in HRPC

15579 Background: As far as prostatic cancer is concerned, we know that somatuline (SMS) blocks GH, PRL, tissular growth factors (TGF) and that it has a direct antiproliferative cellular growth effect. The simultaneous administration of depot forms of SMS and LHRH analogues induced the greatest decrease in tumor growth. Methods: A randomised Phase II trial was carried out in M0 (PSA ≥ 20 ng/ml) and M1 patients with hormone refractory prostate cancer to simultaneously screen decapeptyl and dexamethasone, both with and without SMS (120 mg every 4 weeks), with respect to the PSA response rate, time to PSA progression, duration of survival and toxicity. Results: 72 patients with a median PSA of 77 ng/ml were randomised by 3 centers, 35 to decapeptyl, dexamethasone, both with and without SMS (DDS) and 37 to decapeptyl and dexamethasone (DD). 18 of 33 (54%) patients on DDS and 13 of 32 on DD (43%) had a PSA response (a decrease of at least 50% as compared to baseline). The median time to PSA was 5.5 months in t...