Search

In coffee, fruit production on a given shoot drops after some years of high yield, triggering pruning to induce resprouting. The timing of pruning is a crucial farmer’s decision affecting yield and labour. One reason for fruit production drop could be the exhaustion of resources, particularly the non-structural carbohydrates (NSC). To test this hypothesis in a Coffea L. arabica agroforestry system, we measured the concentrations of NSC, carbon (C) and nitrogen (N) in leaves, stems and stumps of the coffee plants, 2 and 5 years after pruning. We also compared shaded vs full sun plants. For that purpose, both analytical reference and visible and near infrared reflectance spectroscopy (VNIRS) methods were used. As expected, concentrations of biochemical variables linked to photosynthesis activity (N, glucose, fructose, sucrose) decreased from leaves to stems, and then to stumps. In contrast, variables linked more closely to plant structure and reserves (total C, C:N ratio, starch concentration) were higher in long lifespan organs like stumps. Shading had little effect on most measured parameters, contrary to expectations. Concentrations of N, glucose and fructose were higher in 2-year-old organs. Conversely, starch concentration in perennial stumps was three times higher 5 years after pruning than 2 years after pruning, despite high fruit production. Therefore, the drop in fruit production occurring after 5–6 years was not due to a lack of NSC on plant scale. Starch accumulation in perennial organs concurrently to other sinks, such as fruit growth, could be considered as a ‘survival’ strategy, which may be a relic of the behaviour of wild coffee (a tropical shade-tolerant plant). This study confirmed that VNIRS is a promisingly rapid and cost-effective option for starch monitoring (coefficient of determination for validation, R2val = 0.91), whereas predictions were less accurate for soluble sugars, probably due to their too similar spectral signature.

Made available in DSpace on 2019-10-06T15:31:04Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-03-15 Mixing N-fixing trees with eucalypts is an attractive option to improve the long-term soil N status in fast-growing plantations established in tropical soils. A randomized block design was replicated at four sites in Brazil to compare the biogeochemical cycles in mono-specific stands of Eucalyptus (100E) and Acacia mangium (100A) with mixed-species plantations in a proportion of 1:1 (50A50E). Our study aimed to assess the effects of introducing A. mangium trees in Eucalyptus plantations on atmospheric N 2 fixation, N cycling and soil organic matter stocks. Litterfall and soil N mineralization were measured over the last two years of the rotation (4–6 years after planting). Aboveground N accumulation in the trees and C and N stocks in the forest floor and in the top soil were intensively sampled at harvesting age. N 2 fixation rates were estimated using the natural abundance of 15 N as well as by the difference between total N stocks in 100A and 50A50E relative to 100E (accretion method). While the 15 N natural abundance method was unsuitable, the accretion method showed consistently across the four sites that atmospheric N fixation reached about 250 and 400 kg N ha −1 rotation −1 in 50A50E and 100A, respectively. Except at one site with high mortality, N contents within trees at harvesting were approximately 40% higher in 100A than in 100E. Mean N contents in litterfall and N mineralization rates were about 60% higher in 100A than in 100E, with intermediate values in 50A50E. The amounts of N in litterfall were much more dependent on soil N mineralization rates for acacia trees than for eucalypt trees. Soil C and N stocks were dependent on soil texture but not influenced by tree species. N budgets over a 6-year rotation were enhanced by about 65 kg N ha −1 yr −1 in 100A and 40 kg N ha −1 yr −1 in 50A50E relative to monospecific eucalypt plantations. Introducing N-fixing trees in eucalypt plantations might therefore contribute to reducing the need for mineral N fertilization in the long-term. USP ESALQ Forest Science Department UNESP Departamento de Solos e Recursos Ambientais Universidade Estadual Paulista ‘Júlio de Mesquita Filho’ CIRAD UMR Eco&Sols Eco&Sols INRA CIRAD IRD Montpellier SupAgro University of Montpellier USP CENA, Av. Centenário, 303 CENIBRA Coordenação de Pesquisa Florestal, 35196-972 Belo Oriente Department of Forest Science and Wood UFES, 29550-000 Jerônimo Monteiro UNESP Departamento de Solos e Recursos Ambientais Universidade Estadual Paulista ‘Júlio de Mesquita Filho’

In the buffer zone of the Lamto Reserve, a protected area located in the forest-savannah transitional zone in central Ivory Coast, the exotic shrub Chromolaena odorata has invaded abandoned fields and degraded forests. As a result, they have turned into thickets that are used by local farmers as natural fallows to enhance soil fertility for food production. However, information about their impact on soil is scanty and investigations focusing exclusively on baseline data on C. odorata fallows in humid savannahs are still lacking. This study was designed to assess changes in soil physical, chemical and biological properties after the establishment of C. odorata fallows in humid savannahs of Ivory Coast. Sampling sites were selected such that a portion of C. odorata fallow was located next to the shrub savannah, the most common natural ecosystem in the area. Results revealed a rise of soil organic carbon (+ 27.9%), total nitrogen (+ 36.7%), total phosphorus (+ 56.8%), extractable calcium (+ 68.3) and magnesium (+ 140.3%) in the first 10 cm of soil beneath the C. odorata fallow relative to the savannah. Furthermore, the fallow was associated with high N-mineral pool as N-NO3− and N-NH4+ content increased at + 72.5% and + 71.5%, respectively. The infiltration capacity of water under C. odorata-based fallow was markedly high and soil macroinvertebrates, mainly earthworms, showed significant increases in density and biomass. The large quantity of good quality standing biomass produced by C. odorata is likely the main factor controlling the improvement of soil quality. The results suggest that there are merits for the integration of C. odorata fallow in a cropping system for sustainable food production in the buffer zone of Lamto Reserve. This can also help to reduce pressure on forest islands.

Near-infrared reflectance spectroscopy (NIRS) has been accepted as a fast method to evaluate various soil constituents. However, very few studies have used NIRS as a predictor of the textural and mineralogical content of tropical soils. The objective of this study was to investigate the potential use of NIRS as a tool for assessment of diverse soil properties, with specific attention to the prediction of properties related to the mineralogy of a wide range of Latosols from the Cerrado region of central Brazil. The reflectance of the soil samples, 148 in total, taken from 0.0 to 0.2 and 0.6 to 0.8-m depth, was determined in the near-infrared region between 1100 and 2500 nm at 2-nm intervals with a NIRS spectrophotometer. Our results show that for soil sampling corresponding to a large-scale map and taking into account the variability of Latosols over a wide region, NIRS can predict most of the mineralogical properties of the Latosols accurately. Near-infrared spectroscopy did not predict most of the physico-chemical characteristics of soils accurately, in particular those that are largely dependent on agricultural practice, such as pH or CEC. However, the main characteristics that correspond to soil constituents (organic matter and clay content) were relatively well predicted.

International audience; Although freshly formed or unaltered biogenic aggregates are easily recognized, identifying the origin of aggregates altered by physical and biological processes remains empirical and prone to error. The aim of this study was to distinguish between biogenic (BIO) and physicogenic (PHYS) aggregates in various states of fragmentation or size classes using visual, physical and chemical characteristics. Casts produced by Amynthas khami (BIO) and surrounding soil aggregates without visible biological activity (PHYS) were left to disaggregate by natural rainfall events and then separated into five size classes of >10, 10–5, 5–2, 2–0.5 and

Increasing attention is being paid to near-infrared reflectance (NIR) spectroscopy for the rapid and cost-effective determination of soil carbon (C) and nitrogen (N) contents. The objective of the present paper was to compare the performances of two spectrometers: one covered the visible and NIR ranges (Vis–NIR, 350–2500 nm) and included a fibre-optic probe and the other covered the NIR range only (1100–2500 nm) and included a sample transport module. The comparison was carried out on two sets of clayey (n=97) and sandy (n=72) soil samples from tropical Africa and America. On the whole, both technologies provided good calibrations (R2>0.74) and predictions (R2>0.62) of soil C and N contents. The most accurate calibrations were achieved with the NIR spectrometer (R2>0.86), which also yielded the most accurate predictions for the sandy soils (R2=0.90 and standard error of prediction

Air and precipitation samples were collected and analyzed for 91 pesticides or metabolites from May to September 2004 at St. Damase, an agricultural site located in Yamaska basin in Québec, Canada. A broad range of pesticides was detected during this experiment where 40 different compounds were measured. Most of the samples showed more than 10 simultaneous pesticide detections and sometimes reaching 19 simultaneous detections. The most detected pesticides in air were trifluralin, metolachlor and captan, which were found in all the samples during the 5 months of measurements. For the detected compounds, the average concentrations ranged from 4 pg/m3 to 8 ng/m3. Some of the pesticides detected in air were found in precipitation samples as well showing that wet deposition can occur and have an impact on aquatic ecosystems. The most important pesticides detected were related to corn and soya cultivations, the two main cultures in this region highlighting that the major sources come from local applications. On the other hand, the detection of some pesticides in precipitation which were undetectable in air implies that some compounds may have a long range transport origin.

The aim of this study, which was conducted in a humid savannah zone of central Cote d’Ivoire, was to examine changes in the quality of soil cultivated with herbaceous legume cover crops as a function of initial soil characteristics. Mucuna pruriens var utilis and Pueraria phaseoloides were used in a two side-by-side location experiment: a shrubby savannah (the savannah site or “SAV”) and a natural fallow dominated by Chromolaena odorata (the fallow site or “FAL”). The latter was mainly characterized by higher organic matter [organic carbon (C) 10 vs. 7.5 mg kg−1; total nitrogen (N) 0.8 vs. 0.5 mg kg−1) and total phosphorus (P) (282.3 vs. 168.3 mg kg−1) contents in the upper soil layer (0–10 cm). After 8 months of growth, biomass production by M. pruriens was found to be 6.5 and 4.9 t dry matter (DM) ha−1 at FAL and SAV, respectively. For P. phaseoloides, the values were 7.2 and 6.4 t DM ha−1, respectively, in approximately the same period. The quantities of nutrients released by decomposing legume litter were higher at FAL than at SAV. Between-site differences in soil quality improvement were most noticeable in terms of available P, microbial biomass carbon (MBC) and MBC:total carbon (TC) ratio. The FAL site experienced a faster improvement of soil parameters under both legume species: available P increased from 18 to 58 mg kg−1 under M. pruriens, and from 19 to 52 mg kg−1 under P. phaseoloides; MBC increased from 88 to 185 mg kg−1 under M. pruriens, and from 127 to 192 mg kg−1 under P. phaseoloides. In contrast, the parameters remained constant over time at SAV. Soil C and N contents as well as C mineralization showed similar trends at both sites. Based on these results, we conclude that soil quality improvement under cover crops appears to be faster when the initial soil organic C, total N and P contents are adequate. These findings will be useful in assisting governmental decision-making on approaches to be taken for restoring soil fertility in low-input agricultural systems in West Africa.

Previous studies (Ertlen et al., 2010) have shown that near infrared (NIR) spectroscopy of soil organic matter (SOM) can be used successfully to discriminate between SOM from topsoils under forest vs. grassland following establishment of a referential. We have now extended this referential of topsoils, and the derived model was used to characterize SOM within three soil profiles in order to test if vegetation changes throughout these profiles can be detected using NIR spectra from buried soil organic matter. Comparison between the results from this new proxy based on NIR measurements and other historical and pedoanthracological data documenting soil occupation shows no major contradiction in terms of vegetation cover and its evolution with time. These promising results will need further development in order to provide a new palaeoenvironmental tool that is far less time consuming and easier to handle than other methods like pedoanthracology or soil lipid analysis.

Near infrared (NIR) reflectance spectroscopy has been receiving increased attention for the rapid and inexpensive determination of soil properties and of total carbon (Ct) and nitrogen content (Nt) in particular. However, methodological aspects such as sample grinding and drying or replication have not been addressed extensively. The objectives of the paper were, thus, to assess how NIR predictions of Ct and Nt were affected by sample grinding (2 mm sieving vs. 0.2 mm grinding), drying (air-drying vs oven-drying at 40°C during 24 h) and replication (use of one to six sub-samples to determine average spectra). This was performed on a range of tropical soils that differed widely in mineralogy (low and high activity clay soils, allophanic soils) and texture (sandy to clayey). The accuracy of the NIR predictions of Ct and Nt was higher with oven-dried compared to air-dried samples and, more markedly, with 0.2 mm ground compared to 2 mm sieved samples. Replication had a positive effect on NIR predictions when 2 mm sieved samples were used, especially for air-dried samples, but this effect was not clear with 0.2 mm ground samples. Thus, the most accurate predictions of Ct and Nt were obtained with oven-dried finely ground samples, with limited response to sample replication. Accurate predictions were, however, also obtained with four replicates on oven-dried 2 mm sieved samples. Acceptable and less tedious results could, thus, be achieved when replacing fine grinding by replication. Even with this procedure, the r2 between predicted (NIR) and measured (reference) values was 0.9 and the ratio of standard error of prediction to mean ( CV%) was 20% which can be considered satisfactory for the heterogeneous sample set under study.

Background and objective To evaluate the impact of a solid nutritional supplement on the weight gain of institutionalised older adults>70 years with protein-energy malnutrition. The innovation of these high-protein and high-energy cookies was the texture adapted to edentulous patients (Protibis®, Solidages, France). Design An open, multicentre, randomised controlled trial. Setting Seven nursing homes. Participants One hundred and seventy-five malnourished older adults, aged 86±8 years. Intervention All participants received the standard institutional diet. In addition, Intervention group participants received eight cookies daily (11.5 g protein; 244 kcal) for 6 weeks (w0-w6). Measurements Five visits (w-4, w0, w6, w10 and w18). Main outcome Percentage of weight gain from w0 to w6 (body mass in kg). Secondary outcomes Appetite, rated using a numerical scale (0: no appetite to 10: extremely good appetite); current episodes of pressure ulcers and diarrhea. Results Average weight increased in Intervention group (n=88) compared with Control group (n=87) without cookies supplementation (+1.6 versus -0.7%, P=0.038). Weight gain persisted 1 month (+3.0 versus -0.2%, P=0.025) and 3 months after the end of cookies consumption (+3.9 versus -0.9%, P=0.003), with diarrhea reduction (P=0.027). There was a synergistic effect with liquid/creamy dietary supplements. Subgroup analysis confirmed the positive impact of cookies supplementation alone on weight increase (P=0.024), appetite increase (P=0.009) and pressure ulcers reduction (P=0.031). Conclusion The trial suggested that, to fight against anorexia, the stimulation of touch (finger food; chewing, even on edentulous gums) and hearing (intra-oral sounds) could be valuable alternatives to sight, smell and taste alterations.

Nowadays, near infrared (NIR) and mid-infrared (mid-IR) reflectance spectroscopy are recognised useful approaches for quantifying soil properties, cost and time effectively. The aim of this work was to compare predictions of soil carbon (C) and nitrogen (N) content, C/N ratio, substrate-induced respiration (SIR) and denitrifying enzyme activity (DEA) using NIR and mid-IR spectroscopy over a diverse set of 360 Malagasy topsoils. Partial least square regression was used for fitting NIR and mid-IR spectra to conventional data through procedures of calibration either global (one prediction model for all samples) or LOCAL (one prediction model per sample). Prediction accuracy was assessed according to validation ( r2), standard error of prediction ( SEP) in proportion to the mean and ratio of standard deviation to SEP ( RPD). Using both NIR and mid-IR spectroscopy, global calibration over the whole sample set yielded predictions that were excellent for C and N ( r2 > 0.9, SEP 2 > 0.9, SEP < 20%, RPD > 3). In contrast, LOCAL calibration over the coarse-textured sub-set was clearly not useful for improving prediction accuracy. NIR outperformed mid-IR spectroscopy whatever the variable, the calibration procedure and the sample set (except for SIR over the coarse-textured sub-set, where both similar), suggesting its possible superiority for tropical soils.

We have synthesized series of comb-like polyimides with mesogenic units in their side groups. Such comb-like polyimides were obtained by polycondensation of aromatic diamines bearing biphenyl-based mesogenic moieties with bicyclo[2,2,2]oct-7-ene 2,3,5,6-tetracarboxylic dianhydride (BCDA). The different diamines, with two lengths of spacer (with 6 and 11 methylene groups), were synthesized in three steps using as mesogenic groups: biphenyl, 4-cyanobiphenyl and 4-(2-methyl-1-butoxy)biphenyl. The synthesis of the polyimides was performed in two steps: polycondensation of a dianhydride with a diamine in N-methyl-2-pyrrolidone at room temperature giving the corresponding polyamic acid, followed by thermal cyclization into the corresponding polyimide. The comb-like polyimides were studied by X-ray diffraction between room temperature and 250°C. Two types of smectic structure were established: SmA1 for the long spacer and SmC1 for the short spacer.

Understanding the pattern in spatial distribution of soil microbial processes is critical to understand the environmental factors that regulate them as well as to scale up these processes to ecosystem. Soil samples from a I ha tropical rainforest plot (Paracou, French Guiana) were analyzed according a nested sampling approach using different separation distances ranging from 0.4 to 40 m. The variability of substrate induced respiration (SIR) and of denitrification enzyme activity (DEA) was characterized in relation to various soil properties (total C and N contents, NIRS related index of soil organic matter quality, SOMQ and index of tree influence potential, IP). The variability of SIR and DEA was higher than that of environmental properties. The patterns of accumulated variance as a function of distance varied among the soil properties. The variability of SIR and DEA mainly occurred at small (1 m) scale (and at the 10-40 m-scales for SIR), probably reflecting the quality of litter input that results of the influence of local assemblage of different tree species, though changes in the soil N and C contents. Indeed, total soil C and N contents explained the microbial properties at every scale. Coefficients of codispersion showed that neither SOMQ nor IP did correlate with SIR and DEA, and confirmed that total C and N contents explained microbial properties in a scale dependent and complex manner. Such spatial dependency underlines the importance of soil heterogeneity in this tropical forest with implications for sampling strategies when studying the microbial processes and their response to disturbances. (C) 2012 Elsevier B.V. All rights reserved.

In the state of Tabasco, South-eastern, Mexico, land-use changes such as the conversion of natural into agricultural systems, modify soil quality and the abundance of soil macrofauna, including earthworms. The aim of this study was to characterize by near-infrared spectroscopy (NIRS) the earthworms' fingerprint in soil, in six sites including natural and agricultural ecosystems with low and high earthworm biomass and low and high earthworm diversity, in order to identify specific wavelengths that discriminate the presence/abundance of earthworm species and functional groups. The spectral region of 1860-1870 nm was significantly correlated with total earthworm density, particularly at one of the sites (Cedar polyculture; r=0.8, p < 0.05). Earthworm biomass had a specific NIRS wavelength according to the earthworm species and feeding category: 1820 and 1860-1870 nm wavelengths were significantly correlated with Polypheretima elongata (r(2) = 0.7, p

The objectives of this study were: (i) to test whether near infrared reflectance spectroscopy (NIRS) can be used to assess site fertility in sandy and ferralitic soils of the Congo; (ii) to evaluate the comparative advantages of this methodology with respect to classical regressions with chemical and physical analysis of soils; and (iii) to assess the ability of NIRS to predict concentrations of individual nutrients. Sixty-two plots were sampled in 20 selected forest stands with varying wood production. Site indices (Hlim) were estimated from the measured dominant height in the plots. Soil samples (N = 353) were analysed by NIRS, while physical and chemical analyses were carried out on 210 subsamples. Partial Least Squares regression (PLS) was used to model the site index from NIRS, while Variable Importance in Projection (VIP) allowed relating the main explicative frequencies to nutrient availability. A validation was performed based on an independent field trial (not used in the calibration set) in which soils were collected and analysed by NIRS. The measured dominant height growth was compared with the dominant height growth simulated from the site indices predicted using NIR spectra. Multiple regressions between site indices (Hlim) and soil properties failed to explain the variability in Hlim (R-2 = 0.36). This variability was better predicted by NIR spectra, with an R-2 = 0.64 and a predicted Root Mean Square Error of 7% for the mean value of Hlim. Based on analysis of VIP frequencies, the most important factors determining the site indices were organic matter, phosphorus, CEC, clay content, and pH. The comparison between measured and simulated dominant height in the validation set gave similar R-2 (0.61) than in the calibration set. These results demonstrate that mapping of site indices could be performed at an affordable cost in this region. The methodology developed here, which links PLS and VIP to assess the main factors determining soil fertility, is not specific to this study and could be used elsewhere. (C) 2011 Elsevier B.V. All rights reserved.

Raw, mixed and composted organic materials (OM) from agricultural and urban wastes were subjected to biochemical analyses, near infrared (NIR) reflectance spectroscopy and laboratory incubations. Respiration during incubations was accurately predicted using a decomposition model [transformation of added organic materials, (TAO)] of very labile, intermediary resistant, and stable OM fractions. Calibrations using NIR spectra were developed to determine the very labile and stable fractions of OM used to predict three-month OM mineralisation in soil. This study has confirmed that OM decomposition is mainly driven by OM quality on a short-term basis. The wavelengths contributing heavily to the prediction of very labile and stable OM components and molecular functions of these fractions were identified. The resulting TAO–NIR spectroscopy model is an efficient tool to study the degradation of natural molecules and its management for plant growth and sustainability of ecosystems. As a sub-model of a more complex C cycle model, it can instantaneously simulate labile and stable fractions of various organic inputs in soil and, as a non-destructive and easily portable spectroscopic method, could be used to assess C dynamics on a regional scale.

We studied the black carbon (BC) content of ca. 405 samples from French topsoil and artificial soil and carbonate mixtures. Our protocol involved three main steps: (i) decarbonation by HCl, (ii) elimination of non-pyrogenic organic carbon in a furnace at 375 °C, and (iii) quantification of residual carbon by CHN analysis. BC content increased for calcareous soils according to their carbonates content. Subsequent analyses confirmed the existence of a methodological artefact for BC determination only in calcareous soils. Decarbonation changes the thermal properties of organic matter, creating more recalcitrant carbon than in the initial sample. Higher CaCO3 and organic carbon content results in a more pronounced artefact. The reversal of the first two steps of the chemo-thermal oxidation method (i.e. thermal oxidation before soil decarbonation) eliminates this artefact. Overall, our results suggest that BC content may have been overestimated in a large number of studies on calcareous soils.

In addition to total organic carbon and nitrogen, potential organic carbon mineralization under controlled laboratory conditions and indicators such as the indicator of remaining organic carbon in soil (I-ROC), based on Van Soest biochemical fractionation and short-term carbon mineralization in soil, are used to predict the evolution of exogenous organic matter (EOM) after its application to soils. The purpose of this study was to develop near infrared reflectance spectroscopy (NIRS) calibration models that could predict these characteristics in a large dataset including 300 EOMs representative of the broad range of such materials applied to cultivated soils (plant materials, animal manures, composts, sludges. etc.). The NIRS predictions of total organic matter and total organic carbon were satisfactory (R(2)p = 0.80 and 0.85, ratio of performance to deviation, RPDp = 2.2 and 2.6, respectively), and prediction of the Van Soest soluble, cellulose and holocellulose fractions were acceptable (R(2)p = 0.82, 0.73 and 0.70. RPDp = 2.3, 1.9 and 1.8, respectively) with coefficients of variation close to those of the reference methods. The NIRS prediction of carbon mineralization during incubation was satisfactory and indeed better regarding the short-term results of mineralization (R(2)p = 0.78 and 0.78, and RPDp = 2.1 and 2.0 for 3 and 7 days of incubation, respectively). The I-ROC indicator was predicted with fairly good accuracy (R(2)p = 0.79, RPDp = 2.2). Variables related to the long-term C mineralization of EOM in soil were not predicted accurately, except for I-ROC which was based on analytical and well-identified characteristics, probably because of the increasing interactions and complexity of the factors governing EOM mineralization in soil as a function of incubation time. This study demonstrated the possibility of developing NIRS predictive models for EOM characteristics in heterogeneous datasets of EOMs. However. specific NIRS predictive models still remain necessary for sludges, organo-mineral fertilizers and liquid manures.

This study tests the potential of near infrared reflectance spectroscopy (NIRS) for predicting soil fertility and management history from topsoil (0-10 cm deep) spectra. Soil fertility was assessed by measuring the growth of a test plant, and soil management history was determined through inquiries with farmers. Moreover, NIRS predictive value was compared with that of a group of topsoil parameters: total carbon and nitrogen, nitrate, potential respiration and denitrification, and microbial biomass. Modelling used partial and modified partial least square regressions to ensure comparisons between predictions by NIRS versus by soil parameters. Soil fertility and management history were well predicted by NIRS (Q2 = 0.78 and R2 = 0.89 both; Q2 and R2 are cross-validation and calibration coefficients of determination, respectively), as were the soil parameters (Q2 = 0.79-0.92 and R2 = 0.86-0.98). Soil fertility and management history were more accurately predicted by NIRS than by the set of soil parameters. © Taylor & Francis Group, LLC.

International audience; Studying soil nematofauna provides useful information on soil status and functioning but requires high taxonomic expertise. Near infrared reflectance (NIR) spectroscopy (NIRS) has been reported to allow fast and inexpensive determination of numerous soil attributes. Thus the present study aimed at assessing the potential of NIRS for determining the abundance and diversity of soil nematodes in a set of 103 clayey topsoil samples collected in 2005 and 2006 from agricultural soils in the highlands of Madagascar. The morphological characterization of soil nematofauna involved extraction through elutriation then counting under binoculars and identification at family or genus level using microscopy, on ca. 150-g fresh soil samples. Taxa were assigned to five trophic groups, namely bacterial feeders, fungal feeders, obligate plant feeders, facultative plant feeders, and omnivores and predators (together). In addition, four ecological indexes were calculated: the Enrichment index, Structure index, Maturity index, and Plant parasitic index. Oven-dried (40 degrees C) < 2-mm sieved 5-g soil subsamples were scanned in the NIR range (1100-2500 nm), then spectra were fitted to nematofauna data using partial least square regression. Depending on the sample set considered (year 2005, year 2006, or both years), NIRS prediction of total nematode abundance was accurate (ratio of standard deviation to standard error of cross validation, i.e. RPD >= 2) or acceptable (RPD >= 1.6). Predictions were accurate, acceptable, or quasi-acceptable (RPD >= 1.4) for several of the six most abundant taxa, and to a larger extent, for most trophic groups (except facultative plant feeders); but they could not be made for taxa present in a small number of samples or at low abundance. By contrast, NIRS prediction of relative abundances (in proportion of total abundance), was poor in general, as was also the prediction of ecological indexes (except for the 2006 set). On the whole, these results were less accurate than NIRS predictions of soil attributes often reported in the literature. However, though not very accurate, NIRS predictions were worthwhile considering the labor-intensity of the morphological characterization. Most of all, NIRS analyses were carried out on subsamples that were probably too small (5 g) to allow representative sampling of nematofauna. Using larger samples for NIRS (e.g. 100 g) would likely result in more accurate predictions, and is therefore recommended. Scanning un-dried samples could also help improve prediction accuracy, as morphological characterization was carried out on samples not dried after sampling. Examining wavelengths that contributed most to NIRS predictions, and chemical groups they have been assigned to, suggested that NIRS predictions regarding nematofauna depended on constituents of both nematodes and preys' food. Predictions were thus based on both nematofauna and soil organic properties reflected by nematofauna.

Microbial denitrification plays a central role in nitrous oxide (N2O)-emitting processes, which are involved in ecosystem services such as crop production and climate regulation. Field characterization of N2O-emitting processes being time-consuming due to great variability, laboratory determination of potential denitrification (upon incubation) is often used as a valuable test. Near infrared reflectance spectroscopy (NIRS) is a time- and cost-effective approach that has been reported to allow accurate determination of several soil properties. The objective of the present study was to assess the interest of NIRS for determining potential denitrification over a set of 460 topsoils sampled under crops, tree plantations, savanna or rainforest, originating from Madagascar, Congo-Brazzaville, Brazil, and French Guiana. Prediction of potential denitrification using NIRS was satisfying over the total set, especially with LOCAL calibration, which builds a model for each sample separately using its spectral neighbours in the calibration subset (R-2=0.79 for validation). For the other sets, either textural or geographical, global calibration only was performed, involving for each set a unique prediction model built with all calibration samples. The accuracy of NIRS determination depended on the sample set, decreasing in the following order: Malagasy clayey set > total set approximate to. Brazilian sandy loam set > coarse-textured set (Congo-Brazil) approximate to Guianese sandy clay loam set approximate to Congolese sandy set > non-clayey set (Congo-Brazil-Guiana), with cross-validation R-2 ranging from 0.88 to 0.44 (external validation was not carried out for small-sized sets). Thus NIRS prediction was more accurate over the clayey homogeneous set than over the non-clayey heterogeneous set. As a result of global calibration, potential denitrification was expressed as a linear combination of absorbance at every wavelength. Wavelengths that contributed most to NIRS prediction of soil potential denitrification corresponded to wavelengths that literature has assigned to organic nitrogenous compounds, amide-containing ones especially, and to carbonaceous compounds such as cellulose or including CH3 or CH2 groups. This related to the importance of amides in soil organic nitrogen and microbial biomass, and to the dependence of denitrification on soil organic matter. In short, NIRS is a time- and cost-effective approach that proved relevant for determining soil potential denitrification with acceptable accuracy, especially for clayey samples or when LOCAL calibration was performed.

The objective of this laboratory study was to determine the influence of a tropical endogeic earthworm, Pontoscolex corethrurus , on CO 2 and N 2 O fluxes from a tropical Ferralsol and microorganisms potentially involved in these gases emissions. CO 2 and N 2 O fluxes were measured during 35 days from soil mesocosms with and without earthworms. At the end of the incubation, 7% of soil was egested as cast in the earthworm treatment. Then, casts which may be aged from few hours to 35 days old were isolated from non-ingested soil. Different descriptive parameters (activity, density, and structure) of the microbial communities were investigated in the control, the non-ingested soils, and the casts. Quantitative PCR of denitrification genes encoding the nitrite ( nirK ) and nitrous oxide ( nosZ ) reductases was used to study denitrifier density in the earthworm casts. The presence of P. corethrurus induced a significant increase in CO 2 emissions but did not affect N 2 O fluxes when measured at mesocosm level. Despite the absence of significant differences in C and N contents between soils and casts, the near infra-red spectra analysis clearly underlined a specific organic signature for the casts. Fungal and bacterial biomass significantly decreased (∼2-fold) in casts compared to parent soil, but the fungal-to-bacterial ratio was not modified by the earthworm casting activity. Data suggested that bacterial communities, especially denitrifiers, were modified in casts. The relative abundance of nirK and nosZ genes increased in the casts while the genetic structures of total bacteria and denitrifying communities were slightly modified in the casts. This study highlighted the importance of earthworm casts as a specific soil habitat where a subset of soil functional bacterial communities (such as denitrifiers) found favourable condition for their growth. However the effect of P. corethrurus was less evident when up-scaling from casts to mesocosm level.

International audience; Sub-adult individuals of Aporrectodea caliginosa were incubated for 16 weeks under laboratory cultures in a soil treated with 0%, 10% or 50% of a Populus nigra halfdecomposed leaves, respectively. Growth was maximum in the 50% organic matter treatment and cocoon production occurred. Average soil ingestion rates decreased from 1.56 g/g−1 fresh weight of worm per day−1 in control soil to 1.17 and 0.5 g, respectively, in treatments with 10% and 50% half-decomposed litter. Surface casts never comprised more than 10% of total cast production. Near-infrared spectrometry (NIRS)signatures of digested and noningested soil significantly differed and showed a rather constant effect of digestion, independent of the organic matter content (p

Integrated crop–livestock management systems (ICLS) have been increasingly recommended in Brazilian agroecosystems. However, knowledge of their effect on soil organic carbon (SOC) and total nitrogen (TN) concentrations and stocks is still limited. The study was undertaken to evaluate the effects of ICLS under two tillage and fertilization regimes on SOC and TN concentrations and stocks in the 0–30 cm soil layer, in comparison with continuous crops or pasture. The following soil management systems were studied: continuous pasture; continuous crop; 4 years’ crop followed by 4 years’ pasture and vice-versa. The adjacent native Cerrado area was used as a control. Under the rotation and continuous crop systems there were two levels of soil tillage (conventional and no-tillage) and fertility (maintenance and corrective fertility). The stock calculations were done using the equivalent soil mass approach. The land use systems had a significant effect on the concentrations of SOC and TN in the soil, but no effect was observed for the soil tillage and fertilizer regimes. For these two latter, some significant discrepancies appeared in the distribution of SOC and TN concentrations in the 0–30 cm layer. Carbon storage was 60.87 Mg ha −1 under Cerrado, and ranged from 52.21 Mg ha −1 under the ICLS rotation to 59.89 Mg ha −1 with continuous cropping. The decrease in SOC stocks was approximately 8.5 and 7.5 Mg ha −1 , or 14 and 12%, for continuous pasture and ICLS respectively. No-tillage for 10 years after the conversion of conventional tillage to no-tillage under the continuous crop system, and 13 years of conventional tillage in continuous cropping did not result in significant changes in SOC stocks. The SOC and TN stocks in surface layers, using the equivalent soil mass approach rather than the equivalent depth, stress the differences induced by the calculation method. As soil compaction is the principal feature of variability of stocks determinations, the thickness should be avoid in these types of studies.

International audience; Soil bulk density values are needed to convert organic carbon content to mass of organic carbon per unit area. However, field sampling and measurement of soil bulk density are labour-intensive, costly and tedious. Near-infrared reflectance spectroscopy (NIRS) is a physically non-destructive, rapid, reproducible and low-cost method that characterizes materials according to their reflectance in the near-infrared spectral region. The aim of this paper was to investigate the ability of NIRS to predict soil bulk density and to compare its performance with published pedotransfer functions. The study was carried out on a dataset of 1184 soil samples originating from a reforestation area in the Brazilian Amazon basin, and conventional soil bulk density values were obtained with metallic "core cylinders". The results indicate that the modified partial least squares regression used on spectral data is an alternative method for soil bulk density predictions to the published pedotransfer functions tested in this study. The NIRS method presented the closest-to-zero accuracy error (-0.002 g cm-3) and the lowest prediction error (0.13 g cm-3) and the coefficient of variation of the validation sets ranged from 8.1 to 8.9% of the mean reference values. Nevertheless, further research is required to assess the limits and specificities of the NIRS method, but it may have advantages for soil bulk density predictions, especially in environments such as the Amazon forest.

International audience; Chlordecone is a toxic organochlorine insecticide that was used in banana plantations until 1993 in the French West Indies. This study aimed at assessing the potential of near infrared reflectance spectroscopy (NIRS) for determining chlordecone content in Andosols, Nitisols and Ferralsols from Martinique. Using partial least square regression, chlordecone content conventionally determined through gas chromatography-mass spectrometry could be correctly predicted by NIRS (Q² = 0.75, R² = 0.82 for the total set), especially for samples with chlordecone content 12 mg kg(-1), nevertheless ca. 80% samples were correctly predicted when the set was divided into three or four classes of chlordecone content. Thus NIRS could be considered a time- and cost-effective method for characterising soil contamination by chlordecone.

This study aimed at assessing the potential of near-infrared reflectance spectroscopy (NIRS) for determining the distribution of soil organic matter (SOM) in particle size fractions, which has rarely been attempted. This was done on sandy soils from Burkina Faso (three sites) and Congo-Brazzaville (one site). Over the total sample set, NIRS accurately predicted carbon (C) and nitrogen (N) concentrations (g kg(-1) fraction) in the fraction

As soil engineers, earthworms and ants play major roles in soil functioning, especially in modifying soil physical and chemical properties. This study was conducted in a very constraining environment, i.e., paddy fields which have anoxic conditions (approximately four months per year), and which are affected by soil salinisation during the dry period (approximately eight months per year). This study points out that despite those very adverse conditions, soil invertebrates must be taken into account in the dynamic of soil organic and mineral properties in paddy fields. The effects of one earthworm species, Glyphodrillus sp., and an ant species, Epelysidris sp., on soil physical and chemical properties were determined through elemental soil physical and chemical properties (texture, pH, conductivity, C and N contents) and near infrared reflectance spectroscopy (NIRS) in order to evaluate their ability to influence soil organic matter quality. PCA processed with NIRS data clearly showed that biogenic structures (ant sheetings and earthworm casts) were separated from the control surrounding soil. Earthworms and ants affected differently soil properties. Glyphodrillus sp. increased the SOM content and decreased the pH on the surface of the soil. These effects were attributed to an increase in fine particle content (clay). Conversely, Epelysidris sp. only increased the content of coarse particles (sand) and did not influence either soil pH or SOM content. Soil conductivity was found to be very variable but was not significantly affected by soil invertebrates. These results show the potential of soil macro-fauna to create heterogeneity at small spatial scale and to modify the quality of surface soils even under adverse conditions like saline paddy fields.

International audience; In many coarse textured soils, limited root development and biomass production are attributed to adverse physical conditions in the subsoil. The current study was undertaken on an Arenic Acrisol located in Northeast Thailand (i) to assess whether subsoil physical characteristics influence crop rooting depth, and (ii) to compare the benefits associated with conventional tillage with that of localised subsoil loosening on crop performance and selected soil attributes. Control plots consisted of disk ploughing; the implemented treatments were conventional deep-ripping and localised slotting below the planting line. A crop rotation consisting of a legume followed by maize was established annually to assess the impact of these treatments on crop performance. In the control treatment, root development was restricted to the topsoil (0-20 cm) due to high subsoil bulk density (> 1.6 Mg m(-3)). After deep-ripping, no improvement was observed in bulk density, rooting depth and in crop performance. The implementation of a slotting treatment systematically improved root development in the slotted subsoil, root impact frequency increasing from < 0.2 to 0.6-0.8 (P = 0.01) despite no change in the bulk densities of the subsoil. This systematic improvement in root development could be explained by (i) reduced slumping that enable root development prior to recompaction and/or (ii) preferential drainage in the slot and therefore decreased resistance to root penetration. In a dry year maize yield was improved by 78% (P = 0.01); the deep-rooting legume Stylosanthes was tested only a wet year and its biomass production increased by > 40% (P = 0.03). This study highlights the detrimental impact of subsoil compaction on root development and the potential role of slotting in coarse textured soils as a long-term management tool in addressing adverse subsoil physical characteristics that limit deep-rooting.

International audience; Near infrared reflectance spectroscopy (NIRS) is a rapid and low-cost method that has been reported to provide accurate prediction of soil total carbon (Ct) and nitrogen (Nt) contents. However, methodological aspects such as sample preparation and set homogeneity have not been addressed extensively. The main objective of the paper was to assess how NIRS determination of Ct and Nt was affected by sample preparation (0.2 mm grinding vs. 2 mm sieving) and set heterogeneity (i.e. using the total set vs. texture or localised sets). The study was performed on a range of African and Brazilian Alfisols, Oxisols and Ultisols (297 samples, with 6-80% clay). The total set could be divided into a coarse-textured set, including samples from Burkina Faso and Benin mainly, and a clayey set, including samples front Brazil mainly. Calibration and validation procedures were carried out within the total set and within each of the two texture sets and the three localised sets (Burkina Faso, Benin, and Brazil).Prediction of Ct using first derivatives with SNV (standard normal variate) scatter correction, which was the most appropriate spectrum preprocessing method, was in general more accurate for ground than for sieved samples. The difference was decisive when the determination was carried out on the localised clayey set, moderate on total and texture sets, and unclear on localised coarse-textured sets. Prediction of Nt was less clearly affected by sample preparation, though grinding was useful for the localised clayey set and harmful for localised coarse-textured ones. Thus the effect of sample preparation on prediction accuracy depended on soil texture, which may explain the contradictory results reported in the literature, often referring to narrow soil ranges. Using the same preprocessing method, the accuracy of Ct prediction generally increased with set homogeneity (i.e. from total to texture sets and from texture to localised sets), providing that clayey sets were ground. This agreed with deductions drawn from comparison between earlier studies carried out with either homogeneous or heterogeneous sets. The effect of set homogeneity on Nt prediction could not, however, be clearly demonstrated by this study. In conclusion, the study confirmed the interest of NIRS for the rapid and accurate determination of Ct and Nt, especially when homogeneous sets including ground samples were used.

International audience; Macroaggregation is a highly dynamic attribute of soils that is claimed to have a significant impact on their ability to store C and conserve nutrients. A major obstacle to the description and modelling of macroaggregate dynamics, and of the associated processes, is an almost complete ignorance of the real origin of the different types of aggregates found in soils, their turnover times and positions in the soil matrix. We present here a general methodological approach in which the origin of aggregates separated according to visual criteria could be determined by comparing their specific organic matter signatures assessed by Near Infrared Spectrometry (NIRS) to signatures of biogenic structures produced by soil ecosystem engineers (invertebrates and roots) living in the same soil. Macroaggregates and other soil components were separated visually from samples taken at 61 locations regularly distributed across a watershed in Nicaragua and representing crops, pastures, forests, coffee plantations and fallows. Coinertia analyses among soil macroinvertebrate communities and the matrix of soil morphological variables showed highly significant relationships. In Amazonian forest patches and pastures from the state of Pará in Brazil, 75 different types of biogenic structures were collected at the soil surface and on tree trunks, and analysed by the NIRS spectral method. Significant differences among the different types of structures allowed grouping according to their broad phylogenetic origin with large interspecifc differences. In a field experiment conducted at the same site, soils previously under pastures were planted in 16 possible combinations of four plant species, in a fully randomized design replicated three times in different sites. Surface casts of the earthworm species Andiodrilus pachoensis and soil macroaggregates separated by our visual technique had significantly different spectral signatures depending on the location of the plot and the composition of plant cover. However, the comparison of NIRS signatures of soil macroaggregates and casts suggested that Andiodrilus pachoensis was not responsible for the production of the biogenic aggregates that comprised a large proportion on the soil volume in this soil.

Eur. J. Soil Sci. ISI Document Delivery No.: 569XC Times Cited: 7 Cited Reference Count: 34 Ertlen, D. Schwartz, D. Trautmann, M. Webster, R. Brunet, D. Parc Regional des Ballons des Vosges; Institut National des Sciences de l'Univers We thank the Parc Regional des Ballons des Vosges and the Institut National des Sciences de l'Univers for supporting our study and Dr R. Viscarra Rossel for his comments and suggestions. Wiley-blackwell publishing, inc Malden; The absorbance of near-infrared (NIR) radiation by plants depends on the overtones of vibration, bending and stretching of the chemical bonds within their organic components. The wide variety of these bonds gives rise to characteristic NIR spectra, or ‘fingerprints', of plant materials. Do these fingerprints remain in the soil when the plants decompose and allow discrimination between soils that have supported different types of vegetation? We have compared the NIR spectra of grassland soil with those of soil under forest in the Vosges mountains in France. Near-infrared reflectances, R, from 370 samples of soil were recorded as A = log10(1/R) at wavelengths between 1100 and 2500 nm and averaged over 10-nm intervals to give spectra each with 140 values. A canonical variate analysis (CVA) of the raw spectra discriminated well, but not perfectly, between grassland and forest soil, with Mahalanobis distance, D, of 4.87. Standardization along the spectra to remove effects of varied mineral composition achieved complete separation between the two sources with D = 9.81. Canonical variate analysis of first and second derivatives of the spectra distinguished the two groups even better, with D = 12.27 and D = 16.65, respectively. The results show much promise for inferring past vegetative cover from NIR spectra deriving from the organic matter in the soil. The next step will be to extend these studies to see how well we can distinguish other types of vegetation from such spectra.