• Authors:
    • Laurent, F.
    • Ruelland, D.
  • Source: Journal of Hydrology
  • Volume: 409
  • Issue: 1-2
  • Year: 2011
  • Summary: The SWAT model was used to model the impacts of climate, soils and agricultural practices on nitrate flows in a 1310 km 2 catchment in western France. Spatialized data were used for natural features (climate, soil, topography), while agricultural activities, finely represented by crop sequences over 3 years, and their associated cultural practices were mapped by remote sensing. The model was calibrated and validated for discharge and nitrate flows at a gauging station. Results are analyzed with respect to leaching for each crop sequence and for each soil type, as nitrate leaching is highly sensitive to the soil and the crop sequence. The lowest risks were found in clayey soils and the highest in sandy soils and/or in sequences including maize. In collaboration with local stakeholders, five scenarios of alternative practices were simulated to evaluate their consequences for nitrogen flows: reduced fertilization, catch crops, shallow cultivation, no-till with catch crops and filter strips. The impacts of the conversion of a pasture into wheat and rapeseed were also assessed. At the catchment gauging station, our 9-year simulations showed a reduction in nitrate flow of 8% with filters strips, 11% with catch crops, 12% with no-till with catch crops, and 15% with reduced fertilization. Shallow cultivation had no impact on nitrate flow. Inversely, the conversion of temporary pastures, which accounts for 32% of the catchment area, to cereals and rapeseed increased nitrate flow by 18%. The impacts of each scenario varied in accordance with leaching at the parcel scale and with the proportion of area affected by the practice. The results show that modelling can improve our understanding of the impacts of agricultural practices on water quality at different scales.
  • Authors:
    • Labreuche, J.
    • Richard, G.
    • Roger-Estrade, J.
  • Source: Cahiers Agricultures
  • Volume: 20
  • Issue: 3
  • Year: 2011
  • Summary: In this paper, we present a review of the literature on the effects of no-ploughing on soil structure, porosity and stability. In the second part, we discuss the consequences on soil erosion in a temperate environment. The effect of reduced tillage on soil physical properties has firstly to be evaluated on soil structure. If carbon accumulation on the soil surface improves aggregate stability, no-ploughing also greatly affects soil porosity. Not only does it decrease during the period following adoption of no-ploughing, but it also changes in nature and connectivity due to weathering, roots and biological activity. However, the efficiency of these factors is site-dependent and varies with the duration of no-ploughing and the crop sequence. Under tropical climates, reduced tillage systems have been proposed to prevent soil erosion while in temperate areas the present increase of no-till is motivated firstly by the decrease of production and mechanization costs. However, the efficiency of the numerous no-plough tillage systems on erosion control is not systematic. The soil must be sufficiently covered by crop residues and the infiltration rate has to remain high enough. This note critically assesses the available results on these two aspects of the effect of reduced tillage on soil physics.
  • Authors:
    • Bedoussac, L.
    • Justes, E.
  • Source: Field Crops Research
  • Volume: 124
  • Issue: 1
  • Year: 2011
  • Summary: There are many indices available to evaluate the potential advantages of intercrops and species interactions but correct choice of index is crucial in making accurate interpretations. This study compared and evaluated the relevance in understanding intercrop functioning of some well-known indices (aggressivity, AG; cumulative relative efficiency index, REIc; land equivalent ratio, LER) and other potentially useful indices (change in contribution, CC; interspecific and intraspecific interaction index, IE and IA; comparative absolute growth rate, CGR). Data collected from a two-year field experiment in SW France with different fertiliser N levels comparing wheat ( Triticum turgidum L., cv. Nefer) and pea (winter pea, Pisum sativum L., cv. Lucy) grown as sole crops or intercrops in a row substitutive design were used to calculate, compare and evaluate the relevance of the selected indices for understanding intercrop functioning. It was found that AG indices (calculated with or without considering sowing density or actual plant density) did not provide the information generally claimed in the literature (i.e. whether a crop is dominant or dominated). Consequently, their use is clearly unadvisable except when analysed jointly with partial land equivalent ratios. The LER index proved to be clearly relevant, versatile and helpful in illustrating the pattern of competitive outcomes in intercropping experiments, in particular when plotting partial LER values of wheat as a function of those of pea. However, LER cannot identify intraspecific and interspecific interactions. To do so we suggest using the intraspecific and interspecific interaction indices, which can also reveal possible facilitation phenomena and allow description of species change in the contribution index (CC). Interaction dynamics between crops that determine the final balance and the outcome of all competitive interactions occurring between the two crops can be evaluated using the CGR index, which is preferable to REIc, particularly when crops differ greatly in their dry weight. Careful choice of index and interpretation of the results are thus essential in correctly understanding species interactions (globally and dynamically) and intercrop efficiency compared with sole crops. Such indices can help highlight and reveal cereal and legume traits suited to intercropping and also appropriate cropping sequences and management techniques, allowing efficient intercropping. However, the results must always be related to actual data values (yield, dry weight or N accumulated) because the indices used cannot evaluate intrinsically quantitative performance but only the relative performance of intercrops compared with that of sole crops.
  • Authors:
    • Montfort, F.
    • Faloya, V.
    • Schlaunich, E.
    • Aubree, N.
    • Breton, D.
  • Source: 4eme Conference Internationale sur les Methodes Alternatives en Protection des Cultures.
  • Year: 2011
  • Summary: To study the interest and the limits of the insertion of various cover crop with biofumigation potential in a crop succession, three trials, one in Aquitaine (40), one in Normandy (50) and one in Rheu (35) were performed on two important soilborne diseases of carrot: cavity-spot due to Pythium sulcatum or the brown rot disease due to Rhizoctonia solani. Intercrop plants were cultivated then crushed and incorporated in the soil one month before carrot crop. In the three trials, the effect of the mustard Brassica juncea on the incidence and the severity of the diseases is studied and compared with bare soil. In the Normandy trial, two other cover crops are also studied: oat and rye crop. In Le Rheu trial, regular observations allow to compare the development of cavity-spot over time after insertion then incorporation of a mustard crop or after a bare soil. The results are presented; the technical feasibility and the impact of method on disease development are discussed.
  • Authors:
    • Alletto, L.
    • Coquet, Y.
    • Justes, E.
  • Source: Agricultural Water Management
  • Volume: 102
  • Issue: 1
  • Year: 2011
  • Summary: Effects of two tillage treatments and two fallow period managements under continuous maize cropping on soil temperature, soil water dynamics and maize development were evaluated over a 4-year period (2005–2008). Tillage treatments were conventional tillage with mouldboard ploughing and conservation tillage with disk harrowing. The fallow period managements were bare soil or soil sown with a cover crop after maize harvest. For each year, topsoil temperature (0–20 cm-depth) was lower under conservation tillage systems at sowing, from 0.8 to 2.8 °C. This difference persisted several weeks after sowing, and disappeared afterwards. Under conservation tillage, higher soil water content was generally measured at sowing and during the growing season strong fluctuations were observed at 40 cm-depth. Under conventional tillage, soil water content varied mainly in the tilled layer (20 cm-depth). Tillage and fallow period management affected water flow rate at 40 cm-depth. During the maize growing season, the lowest drainage volumes were measured in 2006 and 2008 under conservation tillage in cover cropped plots. No effect of fallow period management on maize development and yield was observed but significantly higher yields were measured under conservation tillage in 2005 and 2007. From this 4-year experiment under continuous maize cropping, using cover crop and reducing tillage intensity enhanced water use efficiency while maintaining or increasing maize yields.
  • Authors:
    • Blanco-Canqui, H.
  • Source: Soil Use and Management
  • Volume: 27
  • Issue: 1
  • Year: 2011
  • Summary: Soil water repellency (SWR) is an intrinsic and dynamic soil property that can influence soil hydrology and crop production. Although several land use systems have been shown to induce water repellency in soil, the specific effects of no-till cropping on SWR are poorly understood. This article reviews the impacts of no-till on SWR and identifies research needs. No-till cropping generally induces 1.5 to 40 times more SWR than conventional tillage, depending on soil type. This may result from near-surface accumulation of hydrophobic organic C compounds derived from crop residues, microbial activity and reduced soil disturbance. While large SWR may have adverse impacts on soil hydrology and crop production, the level of SWR under no-till relative to conventional tillage may contribute to aggregate stabilization and intra-aggregate C sequestration. More research is needed to discern the extent and relevance of no-till induced SWR. This includes: (1) further assessment of SWR under different tillage systems across a wide range of soil textures and climates, (2) comparison of the various methods for measuring SWR over a range of water contents, (3) inclusion of SWR in routine soil analysis and its use as a parameter to evaluate management impacts, (4) assessment of the temporal and spatial changes in SWR under field conditions, (5) further assessment of the impacts of the small differences in SWR between no-till and conventionally tilled soils on crop production, soil hydrology and soil C sequestration, and (6) development of models to predict SWR for different tillage systems and soils.
  • Authors:
    • Heddadj, D.
    • Cloarec, M.
  • Source: Options Mediterraneennes. Serie A, Seminaires Mediterraneens
  • Issue: 96
  • Year: 2011
  • Summary: An experimental device has been set up for ten years at the Kerguehennec Experimental Station (Chambre Regionale d'Agriculture de Bretagne) located in Brittany (western France) on the basis of a corn/wheat/rape/wheat rotation. The study, in the western context of France, compares three tillage practices (moldboard plowing, surface tillage and no-tillage) and two nutrient sources (mineral and poultry manure), each management systems repeated three times. The aim of this study was to evaluate the effect of reduced tillage and manure fertilization on the evolution of soil characteristics: porosity, aggregate stability, organic carbon, hydraulic conductivity and earthworm populations. The results show that treatments without plowing know a decline of global porosity on the layer 0-25 cm, particularly in the case of the no-till. Although the abundance and biomass of earthworms are increased in reduced tillage, the decrease of porosity is not compensated. The consequence is the decline of hydraulic conductivity, in the case of the no-till. Surface tillage seems to constitute the best compromise, because it maintains or improves the infiltrability thanks to the improvement of aggregate stability in the surface layer and the protection of soil surface by the presence of a mulch.
  • Authors:
    • Attard, E.
    • Recous, S.
    • Chabbi, A.
    • Berranger, C. de
    • Guillaumaud, N.
    • Labreuche, J.
    • Philippot, L.
    • Schmid, B.
    • Roux, X. le
  • Source: Global Change Biology
  • Volume: 17
  • Issue: 5
  • Year: 2011
  • Summary: Land-use practices aiming at increasing agro-ecosystem sustainability, e.g. no-till systems and use of temporary grasslands, have been developed in cropping areas, but their environmental benefits could be counterbalanced by increased N2O emissions produced, in particular during denitrification. Modelling denitrification in this context is thus of major importance. However, to what extent can changes in denitrification be predicted by representing the denitrifying community as a black box, i.e. without an adequate representation of the biological characteristics (abundance and composition) of this community, remains unclear. We analysed the effect of changes in land uses on denitrifiers for two different agricultural systems: (i) crop/grassland conversion and (ii) cessation/application of tillage. We surveyed potential denitrification (PD), the abundance and genetic structure of denitrifiers (nitrite reducers), and soil environmental conditions. N 2O emissions were also measured during periods of several days on control plots. Time-integrated N 2O emissions and PD were well correlated among all control plots. Changes in PD were partly due to changes in denitrifier abundance but were not related to changes in the structure of the denitrifier community. Using multiple regression analysis, we showed that changes in PD were more related to changes in soil environmental conditions than in denitrifier abundance. Soil organic carbon explained 81% of the variance observed for PD at the crop/temporary grassland site, whereas soil organic carbon, water-filled pore space and nitrate explained 92% of PD variance at the till/no-till site, without any residual effect of denitrifier abundance. Soil environmental conditions influenced PD by modifying the specific activity of denitrifiers, and to a lesser extent by promoting a build-up of denitrifiers. Our results show that an accurate simulation of carbon, oxygen and nitrate availability to denitrifiers is more important than an accurate simulation of denitrifier abundance and community structure to adequately understand and predict changes in PD in response to land-use changes.
  • Authors:
    • Ortega-Farias, S.
    • Selles, G.
  • Source: ISHS Acta Horticulturae
  • Issue: 889
  • Year: 2011
  • Summary: These proceedings contain 79 papers on irrigation systems for horticultural crops. Specific topics covered include the following: improvement of water use for agriculture at catchment level under drought conditions; impact of climatic change on irrigated fruit tree production; effects of the irrigation regime and partial root zone drying on grape cv. Vermentino in Sardinia, Italy; effects of canopy exposure changes on plant water status in grape cv. Syrah; water use by drip-irrigated early-season peach trees; soil water content variations as water stress indicator in peach trees; reduction in the number of fruits in peach (T204) due to postharvest deficit irrigation; effects of irrigation management and N fertilizer on the yield and quality of apple cv. Gala; canopy temperature as an indicator of water status in citrus trees; effects of root anatomy on sap flow rate in avocado trees; influence of rootstock on the response of avocado cv. Hass to flooding stress; methods of selection for drought tolerance in potato; and drip irrigation for the establishment of strawberry transplants in southern California.
  • Authors:
    • Pires, L. F.
    • Nova, N. A. V.
    • Pereira, A. B.
    • Alfaro, A. T.
  • Source: Revista Brasileira de Meteorologia
  • Volume: 26
  • Issue: 2
  • Year: 2011
  • Summary: The uptake of water from the roots of crops comes to being a physiological response of the plant to the water loss process through its stomata. Getting to know the daily transpiration rates throughout the phenological cycle allows for the application of the ideal amount of irrigation water at the right moment to maximize production with environmental protection. Since transpiration direct measurements at the field, mainly for trees in general, are to be of operational difficulty and relatively high cost we came up with a methodology that allows one to calculate the daily transpiration rates of apple trees and citrus orchards from variables of both the physical environment and the crop. The input data of the proposed model are air temperature, air relative humidity, photoperiod duration, and leaf area. Estimated transpiration rates based on the water potential gradient between the air and leaf approach were comparable in apple trees and citrus orchards. Sap flow daily values were obtained by means of the heat balance method at Bordeaux, France, and Piracicaba, SP, Brazil. All the coefficients of determination of the regression equations obtained herein were higher than 0.93. This allows one to calculate the amount of irrigation water to be applied throughout the crop growing seasons with a high precision as a function of meteorological data and crop covering density at the sites in the study.