Evaluation of the space-time variability of soil salinity by statistical, geostatistical and bayesian maximum entropy methods

This thesis aims to the development of statistical and geostatistical methods for the analysis of space time data and their application to soil salinity. Special emphasis was put on how to characterize soil salinity. Also, the focus was on three groups of methods, i.e. statistical, geostatistical and Bayesian maximum entropy (BME) approaches. Although, the methods were applied to soil salinity, they can be applied to other fields of research as well. In summary, the two main objectives of this study were: - monitoring the temporal change of the spatial pattern of soil salinity using classical statistical methods; - mapping of soil salinity at unobserved space locations and time instants using classical and modern geostatistical methods like the BME

Effect of tillage practices on the soil carbon dioxide flux during fall and spring seasons in a Mediterranean Vertisol

In this study, we assessed the effect of conventional tillage (CT), reduced (RT) and no tillage (NT) practices on the soil CO2 flux of a Mediterranean Vertisol in semi-arid Morocco. The measurements focused on the short term (0 to 96 h) soil CO2 fluxes measured directly after tillage during the fall and spring period. Soil temperature, moisture and soil strength were measured congruently to study their effect on the soil CO2 flux magnitude. Immediately after fall tillage, the CT showed the highest CO2 flux (4.9 g m-2 h-1); RT exhibited an intermediate value (2.1 g m-2 h-1) whereas the lowest flux (0.7 g m-2 h-1) was reported under NT. After spring tillage, similar but smaller impacts of the tillage practices on soil CO2 flux were reported with fluxes ranging from 1.8 g CO2 m-2 h-1 (CT) to less than 0.1 g CO2 m-2 h-1 (NT). Soil strength was significantly correlated with soil CO2 emission; whereas surface soil temperature and moisture were low correlated to the soil CO2 flux. The intensity of rainfall events before fall and spring tillage practices could explain the seasonal CO2 flux trends. The findings promote conservation tillage and more specifically no tillage practices to reduce CO2 losses within these Mediterranean agroecosystems. (Résumé d'auteur

Soil salinity related to physical soil characteristics and irrigation management in four Mediterranean irrigation districts

25 Pag., 6 Tabl., 1 Fig. The definitive version is available at: http://www.sciencedirect.com/science/journal/03783774Irrigated agriculture is threatened by soil salinity in numerous arid and semiarid areas of the Mediterranean basin. The objective of this work was to quantify soil salinity through electromagnetic induction (EMI) techniques and relate it to the physical characteristics and irrigation management of four Mediterranean irrigation districts located in Morocco, Spain, Tunisia and Turkey. The volume and salinity of the main water inputs (irrigation and precipitation) and outputs (crop evapotranspiration and drainage) were measured or estimated in each district. Soil salinity (ECe) maps were obtained through electromagnetic induction surveys (ECa readings) and district-specific ECa–ECe calibrations. Gravimetric soil water content (WC) and soil saturation percentage (SP) were also measured in the soil calibration samples. The ECa–ECe calibration equations were highly significant (P 0.1) with WC, and was only significantly correlated (P Morocco (2.2 dS m−1) > Spain (1.4 dS m−1) > Turkey (0.45 dS m−1). Soil salinity was mainly affected by irrigation water salinity and irrigation efficiency. Drainage water salinity at the exit of each district was mostly affected by soil salinity and irrigation efficiency, with values very high in Tunisia (9.0 dS m−1), high in Spain (4.6 dS m−1), moderate in Morocco (estimated at 2.6 dS m−1), and low in Turkey (1.4 dS m−1). Salt loads in drainage waters, calculated from their salinity (ECdw) and volume (Q), were highest in Tunisia (very high Q and very high ECdw), intermediate in Turkey (extremely high Q and low ECdw) and lowest in Spain (very low Q and high ECdw) (there were no Q data for Morocco). Reduction of these high drainage volumes through sound irrigation management would be the most efficient way to control the off-site salt-pollution caused by these Mediterranean irrigation districts.This study was supported by the European Commission research project INCO-CT-2005-015031.Peer reviewe

ASSESSMENT OF IMPORTANT TECHNOLOGICAL PARAMETERS OF NEW MOROCCAN DOMESTICATED TETRAPLOID OAT LINES OF AVENA MAGNA

Results of studying the oat collection of the N. I. Vavilov All-Russian Institute of Plant Genetic Resources are presented. Field and Nine tetraploid oat lines of Avena magna Murph. et Terr. were assessed for their technological performance. Physicochemical analyses were performed, including moisture, ash, proteins, fibre fractions, lipids, carbohydrates, and minerals. Statistical analysis revealed noteworthy differences in the chemical composition between the cultivars

Variation of some physical and chemical quality traits of Moroccan domesticated tetraploid oat lines of <i>Avena murphyi</i> Ladiz.

A potential in improving nutrition and health is the consumption of high balanced whole grains. A breeding program was launched by the National Institute for Agricultural Research (INRA-Morocco), aiming to develop new domesticated tetraploid oat lines of Avena murphyi Ladiz., with high nutritional benefits. A sequence-based diversity study was conducted on ten tetraploid oat lines of A. murphyi to shed light not only on the importance of domesticating wild oat species for crop improvement but also to highlight the nutritional traits of those oat lines. In this study, we assessed the lines for some grain nutritional traits, such as groat contents of proteins and lipids as well as ash, fiber fractions, carbohydrates, and minerals.The obtained results showed a wide range of chemical contents among lines. The results revealed a high significant difference (P &lt; 0.001) in the groat contents of proteins (11.46–15.12%), fat (4.14–10.14%), carbohydrates (48.68–57.38%), and ash (2.71–5.18%). Analysis of total fiber fractions (NDF, ADF, ADL and CF), showed the presence of significant differences between the assessed lines. The lines A. murphyi 8 and 9, recorded the highest groat protein contents of 15.12% and 13.66%, with an interesting macroelement profile, mainly magnesium and phosphorus, and iron and manganese as minor mineral profile.Due to their biochemical composition, Moroccan domesticated tetraploid oat lines of A. murphyi offer many opportunities to improve oat cultivation in Morocco and serve as an excellent raw material for foodstuffs formulation

Tolerance of chickpea (Cicer arietinum L.) lines to root-knot nematode, Meloidogyne javanica (Treub) Chitwood

The root-knot nematode, Meloidogyne javanica (Treub) Chitwood is an important parasite of chickpea (Cicer arietinum L.). Four chickpea genotypes were evaluated for tolerance to M. javanica in naturally infested fields at three locations. Each genotype was evaluated for number of galls, gall size, root area covered with galls and number of egg masses produced. All the cultivars were susceptible or highly susceptible. Seed yield, weight of 100 undamaged seeds, total dry matter and plant height were compared with checks. Chickpea cultivar Annigeri and a local check were used as nematode susceptible checks in all locations. The four promising nematode tolerant genotypes produced significantly greater yield and total dry matter than the checks in fields naturally infested with M. javanica at three locations. These M. javanica tolerant lines represent new germplasm and they are available in the chickpea genebank at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) bearing the identification numbers ICC 8932, ICC 11152, ICCV 90043 and ICCC 4

Improving Estimations of Spatial Distribution of Soil Respiration Using the Bayesian Maximum Entropy Algorithm and Soil Temperature as Auxiliary Data

This study was supported by the NSF China Programs (Grant No. 31300539 and 31570629) and the Public Welfare Technology Application Research Program of Zhejiang province (Grant No. 2015C31004).Soil respiration inherently shows strong spatial variability. It is difficult to obtain an accurate characterization of soil respiration with an insufficient number of monitoring points. However, it is expensive and cumbersome to deploy many sensors. To solve this problem, we proposed employing the Bayesian Maximum Entropy (BME) algorithm, using soil temperature as auxiliary information, to study the spatial distribution of soil respiration. The BME algorithm used the soft data (auxiliary information) effectively to improve the estimation accuracy of the spatiotemporal distribution of soil respiration. Based on the functional relationship between soil temperature and soil respiration, the BME algorithm satisfactorily integrated soil temperature data into said spatial distribution. As a means of comparison, we also applied the Ordinary Kriging (OK) and Co-Kriging (Co-OK) methods. The results indicated that the root mean squared errors (RMSEs) and absolute values of bias for both Day 1 and Day 2 were the lowest for the BME method, thus demonstrating its higher estimation accuracy. Further, we compared the performance of the BME algorithm coupled with auxiliary information, namely soil temperature data, and the OK method without auxiliary information in the same study area for 9, 21, and 37 sampled points. The results showed that the RMSEs for the BME algorithm (0.972 and 1.193) were less than those for the OK method (1.146 and 1.539) when the number of sampled points was 9 and 37, respectively. This indicates that the former method using auxiliary information could reduce the required number of sampling points for studying spatial distribution of soil respiration. Thus, the BME algorithm, coupled with soil temperature data, can not only improve the accuracy of soil respiration spatial interpolation but can also reduce the number of sampling points.Yeshttp://www.plosone.org/static/editorial#pee