Effect of cropping strategies on irrigation water productivity of durum wheat

The interest of irrigation for durum wheat is often questionable because of possible spring rainfalls in the SE of France. In this study cropping strategies i.e. plant density (PD), sowing date and irrigation management were analysed for improving irrigation water productivity (IWP). An experiment was carried out for calibrating and validating PILOTE model. An adaptation of the potential harvest index to PD was implemented in PILOTE. The latter satisfactory simulates different model outputs with coefficients of efficiency greater than 0.97. The model was employed for simulating the impact of cropping strategies on IWP for a long climatic series. According to model simulations, the necessity of irrigation is questionable under our conditions. IWP was notably lower under high PD than under low PD for the same sowing date. Under low PD and without irrigation it would be possible to obtain a yield similar to that obtained under high PD with irrigation

Adapting PILOTE model for water and yield management under direct seeding system: The case of corn and durum wheat in a Mediterranean context

Crop models are useful tools for integrating knowledge of biophysical processes governing the plant-soil-atmosphere system. But few of them are easily usable for water and yield management especially under specific cropping systems such as direct seeding. Direct seeding into mulch (DSM) is an alternative for conventional tillage (CT). DSM modifies soil properties and creates a different microclimate from CT. So that, we should consequently consider these new conditions to develop or to adapt models. The aim of this study was to calibrate and validate the PILOTE [Mailhol, J.C., Olufayo, A.A., Ruelle, P., 1997. Sorghum and sunflower evapotranspiration and yield from simulated leaf area index. Agric. Water Manag. 35, 167-182; Mailhol, J.C., Zaïri A., Slatni A., Ben Nouma, B., El Amami, H., 2004. Analysis of irrigation systems and irrigation strategies for durum wheat in Tunisia. Agric. Water Manag. 70, 19-37], an operative crop model based on the leaf area index (LAI) simulation, for corn and durum wheat in both DSM and CT systems in Mediterranean climate. In DSM case, simple model modifications were proposed. This modified PILOTE version accounts for mulch and its impact on soil evaporation. In addition root progression was modified to account for lower soil temperatures in DSM for winter crops. PILOTE was calibrated and validated against field data collected from a 7-year trial at the experimental station of Lavalette (SE of France). Results indicated that PILOTE satisfactorily simulates LAI, soil water reserve (SWR), grain yield, and dry matter yield in both systems. The minimum coefficient of efficiency for SWR was 0.90. This new version of PILOTE can thus be used to manage water and yield under CT and DSM systems in Mediterranean climate

Adapting PILOTE model for water and yield management under direct seeding system: The case of corn and durum wheat in a Mediterranean context

Crop models are useful tools for integrating knowledge of biophysical processes governing the plant-soil-atmosphere system. But few of them are easily usable for water and yield management especially under specific cropping systems such as direct seeding. Direct seeding into mulch (DSM) is an alternative for conventional tillage (CT). DSM modifies soil properties and creates a different microclimate from CT. So that, we should consequently consider these new conditions to develop or to adapt models. The aim of this study was to calibrate and validate the PILOTE [Mailhol, J.C., Olufayo, A.A., Ruelle, P., 1997. Sorghum and sunflower evapotranspiration and yield from simulated leaf area index. Agric. Water Manag. 35, 167-182; Mailhol, J.C., Zaïri A., Slatni A., Ben Nouma, B., El Amami, H., 2004. Analysis of irrigation systems and irrigation strategies for durum wheat in Tunisia. Agric. Water Manag. 70, 19-37], an operative crop model based on the leaf area index (LAI) simulation, for corn and durum wheat in both DSM and CT systems in Mediterranean climate. In DSM case, simple model modifications were proposed. This modified PILOTE version accounts for mulch and its impact on soil evaporation. In addition root progression was modified to account for lower soil temperatures in DSM for winter crops. PILOTE was calibrated and validated against field data collected from a 7-year trial at the experimental station of Lavalette (SE of France). Results indicated that PILOTE satisfactorily simulates LAI, soil water reserve (SWR), grain yield, and dry matter yield in both systems. The minimum coefficient of efficiency for SWR was 0.90. This new version of PILOTE can thus be used to manage water and yield under CT and DSM systems in Mediterranean climate.GESTION DE L'EAU;MODELISATION;PRODUCTION VEGETALE;SEMIS DIRECT;MAIS;BLE;CROP MODEL;SOIL WATER BALANCE;DIRECT SEEDING;CONVENTIONAL TILLAGE

Semis direct sous couverture végétale (SCV) en climat méditerranéen

According to Labreuche et al. (2007) there are almost no data on long-term practice of direct seeding into mulch (DSM) in France. The motivation caused by the common agricultural policy in the early 90s has promoted the development of DSM. The reduction of working time caused by the DSM is a major source of motivation in France. Whatever the country, the no tillage or minimum tillage are not without technical problems. Some agronomic consequences must also be managed as weed control. The results of our study can improve our knowledge about DSM by comparing it to conventional tillage (CT). These two systems are compared on a field scale related to crop yield, water balance, nitrogen balance, and water use efficiency (WUE). The results from our experiments show that the yield of DSM for irrigated durum wheat decreased due to plant density and pest attack; however we had almost the same yield for without nitrogen and rainfed treatments. For a summer crop such as corn, we had the same yield with both systems. Regarding WUE for corn WUE was not significantly different even if it has the tendency to be higher on DSM. In agreement with literature, DSM reduces evaporation by the presence of residues on the soil surface. The analysis of nitrogen (N) balance shows that despite lower N losses, N use efficiency has declined in DSM. This militates in favor of a nitrogen management change in DSM.D'après Labreuche et al. (2007) il n'y quasiment pas de données sur la pratique à long terme du semis direct sous couverture végétale (SCV) en France. La motivation provoquée par la PAC au début des années 90 a favorisé le développement du SCV. La réduction du temps du travail occasionnée par le SCV est une source importante de motivation en France. Quel que soit le pays, la suppression ou la réduction du travail du sol n'est pas sans poser de problèmes techniques. Certaines conséquences agronomiques doivent également être gérées, comme la maîtrise des adventices. Les résultats du travail présenté ici, nous permettent d'améliorer notre connaissance du SCV par rapport au système conventionnel (CT). Ces deux systèmes, sont comparés à l'échelle parcellaire au niveau du rendement, du bilan hydrique, du bilan d'azote, et de l'efficience d'utilisation de l'eau (WUE : Water Use Efficiency). Les résultats issus de nos expérimentations montrent qu'en SCV, pour le blé dur irrigué, le rendement baisse (en raison de problèmes de levée, et d'attaques de ravageurs) en revanche on a obtenu presque le même rendement pour les traitements sans azote et aussi le traitement pluvial. Pour une culture d'été comme le maïs, on a obtenu le même rendement en SCV qu'en CT. En ce qui concerne la WUE pour maïs, elle n'est pas significativement différente même si elle a la tendance à être plus élevée sur SCV. En accord avec les résultats de la littérature, le SCV réduit l'évaporation du fait de la présence des résidus à la surface du sol. L'analyse du devenir de l'azote montre qu'en dépit d'un déficit de bilan plus faible, l'efficience d'utilisation de l'azote a diminué en SCV. Cela milite en faveur d'un changement de gestion d'azote en SCV

Est-ce que le sol est homogène et uniforme à une échelle très réduite ?

Soil is a complex system and is naturally heterogeneous. Due to these heterogeneities, soil properties change in time and space. Therefore, many samples are needed to obtain the average hydrodynamic properties. Moreover, the methods used for calculating these properties are expensive and time consuming. It is accepted that soil is homogeneous at a small scale (m2) and that its properties are uniform at that scale, allowing the use of the Darcy's law and the Richard's equation. To test this assumption, an infiltration-runoff experiment was conducted at the 1m2 scale under simulated rainfall. Soil is classified as a Calcosol with a clay loam texture and a high structural stability. The slope was equal to 5% and two rainfall intensities were used, 15 mm h-1 applied on a dry soil, and 32 mm h-1 applied on a wet soil 48h after the first experiment. 24 micro-tensiometers were installed at two depths (8 and 13 cm) for the monitoring of soil matric potentials every 10 s. Runoff was measured manually. Evolution of soil matric potentials are very heterogeneous whatever the depth of insertion : the rate of front wetting (calculated from time reaction of tensiometers) ranges from 126 mm h-1 to 376 mm h-1 at 8 cm depth, and from 165 mm h-1 to 365 mm h-1 at 13cm depth. After the experiments, 12 cores samples were taken from the A horizon for the determination of the hydrodynamic properties using the Wind's evaporation method and the constant head permeameter. The hydraulic conductivity at saturation Ks ranges from 5 to 220 mm h-1 and the hydrodynamic properties in the unsaturated range are also highly variable. A 2D infiltration model based on the Richard's equation was then developed to quantify the influence of the variability of soil properties on the infiltration rate and pattern

Besoins en rendement et énergie du blé dur sans labour et en conventionnel en climat méditerranéen

International audienceA key principle of no-tillage (NT) system is the retention of crop residues on the soil surface to preserve soil water for crop growth. In response to the negative impact of soil degradation processes under conventional tillage (CT) systems that are based on soil tillage, NT system without tillage practices and with protective cover of crop residue are being developed in many parts of the world. Apart from the positive effects on soil conservation and sustained land productivity, another major impact of NT is decreasing labor costs, generally leading to higher income and a better standard of living for the farmers. However NT is a successful system especially in the South of America, but the impacts of this system in the Mediterranean climate especially in the south of France is less well known; so that this study has been carried out within the scope of a European project. Durum wheat was sown for two years under two tillage treatment i.e. CT and NT. Time requirement and fuel consumption in these two systems were measured. The results show that the crop production is higher in CT system, while work duration and energy requirement is lower in NT system

The impacts of direct seeding into mulch on the CO2 mitigation

The development of agricultural systems with low input of energy could help to reduce agricultural greenhouse gas emissions. Tillage consumes nearby 50% of the direct energy in conventional tillage system (CT). Current agricultural policies seek to promote crop production systems that minimize fossil energy input for a high level of output. One possible solution can be the conservation tillage, where tillage will be reduced or even completely eliminated such as direct seeding into mulch (DSM). Conservation tillage can both reduce diesel consumption and sequestrate C into soil, resulting CO2 mitigation. The present study assessed the impact of DSM on CO2 mitigation compared with CT. An experimental study has been carried out at Lavalette experimental station in Montpellier in south-east France. The diesel consumption for field operations was measured in both DSM and CT. Soil C concentration was measured too. CO2 emission was calculated considering CO2 emission from diesel combustion and organic carbon variations in soil during the field trial. The results showed that using DSM resulted in less diesel consumption compared with CT (about 50%). Furthermore, DSM did increase C content of soil (1671 kg/year/ha). The consequence of these two positive impacts of DSM ended up in a considerable CO2 mitigation

Impact du sans labour sur les propriétés hydrauliques du sol comparé au labour conventionel

International audienceSoil hydraulic properties are very important in precision irrigation, water and solute transport and irrigation scheduling. Tillage can change near surface soil hydraulic properties. In this study Beerkan methodwas used to better understand tillage and no-tillage impacts on transmission properties of topsoil. Beerkan is a simple in situ method using a single ring to measure infiltration rate. This method depends on an algorithm namely BEST to estimate soil hydraulic properties. This study was carried out at Cemagref experimental station in Montpellier in the South-eastern France. Three different infiltration measurement series were done in both no-tillage and conventional tillage treatments. The first infiltration measurement series was performed after harvest of durum wheat; the second one was performed after sowing of corn and finally the last one was performed after the harvest of corn. By using those three series as input data, BEST model estimated saturated hydraulic conductivity (Ks), sorptivity, the mean characteristics of hydraulically functional pore size and capillary length. The results indicate that after harvest, hydraulic properties were not significantly different; however after sowing of corn, Ks was significantly higher in CT system (pLes propriétés hydrauliques du sol jouent un rôle important en irrigation de précision et dans le transfert de l'eau et des solutés ainsi que pour le pilotage des irrigations.Le labour affecte ces propriétés au voisinage de la surface du sol. La méthode Beerkan est ici utilisée pour mieux comprendre l'impact du labour et du non-labour sur le transfert des propriétes de la partie supérieure du sol. Cette étude a été réalisée sur la parcelle expérimentale de l'IRSTEA de Montpellier.Le résultat indique qu'aprés récolte les propriétés hydrauliques ne sont pas significativement différentes ; cependant aprés semis du maïs , Ks est significativement plus élevé en CT . Cet état de fait devrait être pris en compte pour irriguer et fertiliser

Les changements de la rugosité de la surface du sol sous des pluies simulées évaluées par photogrammétrie

Erosion and runoff processes are influenced mainly by the soil surface characteristics. Among them, soil surface roughness is a key parameter. As this parameter is usually anisotropic, it can not be calculated from elevation measurements along one direction (1D). The close-range photogrammetric method is a rapid and flexible tool to obtain digital elevation models (DEM) at the 1m2 scale but it still needs to be evaluated against a reference method such as the laser relief-meter. The objective of this study was first to validate photogrammetry by comparing roughness indices extracted from a DEM obtained using this method with indices calculated from 1D laser relief-meter measurements, and then to monitor rainfall induced changes of the soil surface roughness with photogrammetry. Two experimental plots were subjected to successive simulated rainfall events. Plot 1 is a seedbed plot with a random roughness, whereas plot 2 is a harrowed plot with an oriented roughness. Comparison was made between the two soil roughness measurement techniques with regard to data acquisition, computation efforts, resolution, precision and capability to represent soil surface features and especially to monitor the evolution of soil surface roughness. Horizontal resolution for the laser scanner was approximately 1mm along a 1m long transect while it was about 0.5 mm for the photogrammetric method for a 1m2 plot. Elevation data were extracted from the DEMs on the same profile as the one measured with the laser method. We compared roughness indices calculated on these profiles, namely Random Roughness (RR) and Tortuosity (T). Results obtained using the two methods were closely related: after a 160 mm cumulative rainfall, RR was found to be reduced from about 7.0 to 4.8 using the laser technique and from 7.6 to 5.5 with the photogrammetric method for the seedbed plot. The T index was reduced from 2.41 to 1.99 (laser method) and from 1.64 to 1.34 (photogrammetry). Both measurements methods detect the evolution of soil surface roughness and yield very close RR indexes. However T index is lower when it is measured using photogrammetry then when the reference method is used. Overall, results show that the photogrammetric data were useful for soil surface characterization and can detect the soil surface evolution: they can therefore be helpful for soil erosion and runoff processes study. Moreover, photogrammetry can be used under rainfall, it is very flexible, data acquisition is quick, and DEM calculated from this method provide more information on the spatial structure of the soil roughness than a 1D method

Impacts of direct seeding into mulch on the yield, water use efficiency and nitrogen dynamics of corn, sorghum and durum wheat

International audienceDirect seeding into mulch (DSM) is a cropping system that is increasingly used in the world. The major concern among producers is the possible yield penalties associated with DSM compared to conventional tillage (CT). The aim of our study was to assess the effects of DSM on the yields of corn, sorghum and durum wheat, as well as water use efficiency (WUE) and nitrogen dynamics. An experimental study was carried out at the Lavalette experimental station from 2001 to 2007. Corn, sorghum and durum wheat were sown in two tillage treatments (CT and DSM). Yield and some yield components, nitrogen dynamics and WUE were determined. The results showed that DSM could maintain the crop production of corn and sorghum, however, for durum wheat, CT performed better. DSM improved WUE and irrigation water use efficiency (IWUE) of corn and sorghum and decreased crop evapotranspiration from 5 to 27%. These results suggest that DSM is a relevant alternative to the CT system for corn and sorghum in the SE of France. Adopting DSM with a relevant crop rotation and cover crop resulting in a better IWUE for this system compared with CT can effectively address water scarcity issues in this region