Crop protection forecasting models currently use meteorological data observed at stations to produce pest infection and development indices. The indices are then extrapolated to the regional level by assuming that the weather conditions at the stations are similar to those in neighbouring fields in the region, which is not necessarily the case. Hence, this has a significant impact on the quality of the recommendations and diagnoses based on computerized plant protection models. The regionalization of model outputs between the stations comprising the weather network, using geostatistical techniques such as cokriging in conjunction with satellite data, is a worthwhile approach for addressing this need. The objective of this study is to develop and apply a methodology for regionalization of infection indices produced by two crop protection models contained in the CIPRA (Computer Centre for Agricultural Pest Forecasting) system, using geostatistical tools and NOAA-AVHRR images. This approach will help enhance our crop pest management and forecasting capabilities while optimizing the use of pest control products in vegetable crops in Quebec. To achieve our objective, a cokriging method was applied to regionalize the model outputs using air temperature and relative humidity estimated from NOAA-AVHRR images. The results were then validated against a regionalization approach using ordinary kriging and two conventional interpolation techniques.
In France, the obligate root parasite O. ramosa L. (broomrape) causes significant decreases in yields in several crops such as Brassica napus L., Cannabis saliva L. and Nicotiana tabacum L. Over the past few years, the broad distribution and the continuous expansion of this parasitic plant have been pointed out. The diversity of its host plants and the increase in its locations in France led us to investigate the virulence of some O. ramosa populations against their potential host plants. Significant variation in their aggressiveness was observed. These results are therefore consistent with the existence of at least two O. ramosa pathovars throughout populations scattered in France. A study by PCR of inter-simple sequence repeat (ISSR) of these two populations allowed us to characterize each of them by specific molecular markers.
In addition to its environmental implications, ammonia volatilization is the principal source of variation of fertilizer efficiency. In a larger study estimating the effect of the dissolution step of fertilizer pellets on ammonia volatilization, we analyzed the sources of uncertainties in measuring low ammonia fluxes. The air humidity, and above all the air flow rate, are important contributors to the variation in fluxes. An exponential curve obtained from a set of 35 data points is proposed to normalize the ammonia emission rates according to the air flow rate (R 2 = 0.52). Modifications of the standard laboratory method are also proposed to improve the estimation of the low ammonia fluxes over a short timescale. However, the system was kept simple to manage, and reproducible to perform a statistical analysis of the results.
The Joint Research Centre (JRC), in collaboration with the Food Agriculture Organization (FAO), has developed for East Africa an operational crop yield monitoring and forecasting system (CYMFS). The CYMFS integrates into a Geographical Information System (GIS): the meteorological information of the European Centre for Medium-Range Weather Forecast (ECMWF), the Crop-Specific Water Balance (CSWB) model, and the Crop Production System Zones database (CPSZ). Additional and independent real-time satellite data from SPOT VEGETATION were analyzed using a specific crop mask to concentrate the analysis only on agricultural areas. This approach gives to the food analyst a qualitative picture of crop yield expectation for rain-fed crops at different stages of the growing season. The proposed methodology was applied to the first crop season of 2001 and 2002 and demonstrated a clear potential in crop monitoring and yield forecasting. The results obtained during the extremely dry year of 2002 proved that the crop monitoring system was timely and geographically precise. A new crop cycle progress index (CCPI) was developed to take into consideration the agro-ecological heterogeneity of the region.
A spectrally derived cellulose absorption index (CAI) was tested to determine its value as a remote sensing method for detecting crop residue ground coverage for soil erosion control in soybean (Glycine max (L.) Merr.). Soybean produces inadequate crop residue for soil conservation purposes in many production years. Crop residues left on the soil surface after harvest slow soil erosion rates. The CAI remote sensing technique was tested over field plots of conventional and large biomass soybean (LBS) with known above ground crop residue biomass and surface coverage. New LBS types are being bred and tested at the Beltsville Agricultural Research Center (BARC), Beltsville, Maryland, US, and can grow to heights of 1.8 m and produce increased amounts of crop residue compared to conventional cultivars. The highest performing LBS line for these traits provided 2963 kg/ha more crop residue biomass and provided a maximum increase of 42% more crop residue cover than the poorest performing conventional soybean. The comparison of LBS versus conventional soybean provided a wide range of soybean residue coverage for testing the CAI remote sensing algorithm. Spectrally derived CAI measures of crop residue were significantly associated with physical ground measurements of crop biomass at harvest and % cover after over wintering. Significant correlations were found between, the CAI and at harvest biomass (r 2 = 0.66), between, the CAI and the line point transect measurement (r 2 = 0.74), and between, CAI and the analysis of red-green-blue digital imagery (r 2 = 0.74) for measuring crop residue cover. These findings indicate that LBS can increase crop residue biomass and crop residue soil coverage by soybean litter and these factors can be detected by remote sensing methods in the field.
With the aim of evaluating the possibility of recycling industrial orange wastes as soil conditioners, a research was carried out to study the effects of different doses of this orange wastes on soil parameters, some growth parameters and production of durum wheat in a Mediterranean environment where the soils are generally poor in organic matter. Three doses were used in the first year; in the second year the same doses and the residual effects of the previous treatments were studied. Soil characteristics, crop growth and yield were determined. Conditioning positively influenced some parameters of the soil. The organic matter had only partly modified its own structure due to the decomposition process during the year after the conditioning. The processes of degradation of the organic matter were predominant as compared with the humification ones under the pedologic and climatic conditions of the trials (sandy soil and dry hot climate). Conditioning carried out with doses higher than the minimum had a depressive effect on the crop productivity due to the excessive vegetation vigour.
In recent years models have become an integral part of the pesticide registration processes. However, there are still no validated models which can adequately describe the specific conditions of rice paddies. Accordingly, this study aimed to evaluate the capability of a proposed model, the RICEWQ-VADOFT model, to simulate leaching of propanil. Model performance was evaluated with a data set derived from a field study (1993-1994) carried out in five paddy fields in the southern part of the Axios river basin. Predicted and measured concentrations of propanil leaching to the deeper soil layer were in good agreement. The Root Mean Square Error (RMSE) and Modeling Efficiency (EF) values calculated for three of the five studied fields varied between 39.4-46.1 and 0.813-0.867, respectively, indicating good model performance. However, little agreement between predicted and observed pesticide concentrations was evident in the remaining two paddies. This was attributed to the presence of preferencial flow mechanisms in these particular fields, which facilitated the rapid transport of high concentrations of propanil into the deeper soil layers, and which the model was not able to predict.
An analysis of the dissipation of herbicides was done in paddy water and in drainage channels of farm paddies as well as in experimental plots. A field study was conducted in three selected paddy farms of Higashi Hiroshima and an experiment was carried out in the Hiroshima Prefecture Agriculture Research Center in the paddy season of the year 2002. The herbicides were mefenacet, thiobencarb, pyributicarb and cyhalofop -butyl. The sample water was analyzed by using gas chromatography after solid phase extraction. The maximum concentration of all herbicides was detected within 1 to 3 days after herbicide application and became trace level after 21 to 28 days. The highest amount of herbicide detected was 338 μg/L mefenacet in Farm B. No cyhalofop-butyl was detected in the experiment but was found in farm paddies until 7 days. Thiobencarb was detected until 21 and 28 days, respectively, in farm paddies and in the experiment. Pyributicarb was detected until 28 days in farm paddies and in the experiment. We found that the concentration of all herbicides in drainage channels was comparable with the paddy field at 1 day and 3 days and thiobencarb at 1 day.
Downy mildew, caused by Plasmapora viticola, is one of the endemic cryptogamic diseases of northern Spain that most commonly affects grapevines. Indeed, it is one of the diseases best known to viticulturalists worldwide. When climatic conditions are favourable, it attacks all organs of the plant, causing very serious crop losses and affecting the profitability and cost of wine. Given the climatic conditions of northern Spain, downy mildew attacks occur every year without exception, obliging growers to apply several treatments during the vine growth cycle. This not only increases cultivation costs enormously but causes environmental pollution and leads to problems during the fermentation of the must. Although the economic losses caused by downy mildew can be severe, greater knowledge of the pathogen’s biology, the availability of systemic treatments, and the better training of growers have helped reduce the risk of such damage. In recent years, several integrated programmes have been launched in the fight against this disease. Taking into account climatic conditions, the point in the vine growth cycle, and the development of the fungus, the aim is to reduce the number of treatments that need be applied to a minimum. Wine-producing countries are trying to develop disease prediction models for each of their growing regions. The German “Pro” [6] & “Freiburg” [8] models, and the Swiss “Winemild” model [1] are among the most well known. Infection with Plasmapora viticola leads to different symptoms depending on the organs attacked and the stage of its development: young leaves, adult leaves, or flowering stage, veraison, or ripening. Although the leaves can be affected even when very small, maximum sensitivity occurs when they are about 3 cm in diameter. The first symptoms are seen on the leaf lamina as ‘oil spots’. In the last phases of leaf disease, these spots become reddish-brown and acquire a typical mosaic pattern. Leaves become less sensitive as they age [3]. Vitis vinifera L. is very sensitive to downy mildew [4, 5, 10], although there are differences between different varieties and possibly even between different clones [10] . Many authors [4, 10, 7, 11] have reported that several factors appear to determine the degree of resistance possessed. Several laboratory studies [12] have investigated the resistance of different varieties of vine to downy mildew, but such results cannot always be extrapolated to the field. Different climatic, soil and cultivation conditions, etc., can all have great influence on whether the disease will appear and how it will develop. The qualitative methods currently used to measure resistance to disease have the problem of inherent subjectivity [5, 12]. A method is therefore required that can quantify the resistance of different varieties and clones in the field, which takes into account the factors that affect both plant and pathogen development, and which reduces as much as possible the subjectivity of current methods.
Leaf and crop water measurements were analysed dynamically throughout the cycle of two crops of durum wheat subjected to contrasting conditions of water supply. The objectives were to compare short- and long-term crop reactions to water deficit, based on some hypotheses from the literature. Water status measurements were of the first type and phenological or morphological measurements of the second type. The droughted crop under a rainout shelter received no water between emergence and harvest, while the open-air crop was irrigated. Dynamic plant morphological measurements consisted of leaf area index and specific leaf area, and those characterising plant water status dynamics included predawn leaf water potential, bulk osmotic potential and the ratio of crop water uptake to evaporative demand. Continuous measurement of the surface temperature on the two plots served to calculate a degree-days temperature scale, allowing comparison of the two crops. We found that the droughted crop developed mechanisms of resistance to water deficit: the leaf area index and specific leaf area were reduced (from 6 to 1.5 m(2) m(-2) and from 300 to 260 cm(2) g(-1) for the maximum values of, respectively, the LAI and the SLA), the bulk osmotic potential was lower (from -2 to -3 MPa) and the soil layer affected by root uptake was deeper (from 50 to 100 cm) than that of the irrigated crop. The amount of water evapo-transpired by both crops was similar when related to climatic demand. Yet no clear relationship appeared between the specific leaf area index and osmotic potential. Furthermore, there appeared to be a clear difference between the vegetative and reproductive phases of both crops in terms of water functioning. The osmotic potential decreased markedly after anthesis and a peak of water uptake was observed in both crops during the grain-filling phase, which may have been linked to the specific functioning of the flag leaf or the ear. While this study demonstrated the efficiency of drought adaptive features in durum wheat, it also showed that the difference in the water behaviours of two contrasted durum wheat crops could be of the same order of magnitude as the differences between the vegetative and reproductive phases.
Consumptive water use of the rubber/banana intercropping systems was assessed. Five systems were tested; sole rubber (R) and banana (B) crops and three intercrops comprising additive series of one (BR), two (BBR) and three (BBBR) rows banana to one row of rubber. Planting density of rubber remained constant across the treatments, hence the rate of transpiration associated closely with the planting density of banana with ca. 140% increase from banana-rubber to banana-banana-banana-rubber intercrops. Although water use efficiency (WUE) at whole stand basis was comparable among treatments, water use efficiency of component rubber during the latter part of the experiment increased by 118% in intercrops compared to that of the sole crop. Amount of water transpired even in the banana-banana-banana-rubber intercrops was small by comparison to the water received from rainfall, hence in wet tropics with heavy rainfall, agricultural systems should be designed to enhance the productivity through increase water use with less emphasis on water use efficiency.
Barley (Hordeum vulgare) grown in Mediterranean regions undergoes drought stress during the grain-filling period. A greenhouse experiment was conducted to study the effect of drought stress on grain growth and yield of barley. Plants were exposed to three drought treatments at the beginning of grain filling: (1) well-watered at 100% field capacity, (2) mild drought stress at 60% field capacity, and (3) severe drought stress at 20% field capacity until grain maturity. Grain moisture content and dry weight were determined for grains harvested at 3, 10, 17, 23 and 31 days after the beginning of grain filling. Grain dry weight for severe drought stress plants reached a maximum value earlier than grains from mild drought stress and well-watered plants, indicating that grains from severe drought stress plants had a higher growth rate than those of mild drought stress and well-watered plants. Drought-stressed plants had shorter duration of grain filling than well-watered plants. Drought stress treatments reduced grain yield by reducing the number of tillers, spikes and grains per plant and individual grain weight. In conclusion, postanthesis drought stress was detrimental to grain yield regardless of the stress severity.
The analysis of meteorological data recorded since 1972 at the INRA Station in Colmar (Alsace, France) reveals a significant increase in temperatures. Phenological data recorded on INRA grapevine collections over the same period show that the period between budburst and harvest has become both earlier and shorter. A comparison of climatic and phenological data shows that ripening is occuring under increasingly warm conditions. The climatic water demand after flowering tends to increase and, as there is no clear evidence for a change in rainfall, the risks associated with dry summers are likely to increase in the future. Quantified data on climate evolution, development stages and bioclimatic indices during the main development phases are presented and discussed.
We evaluated the economic and environmental interests of a balance-sheet method recently developed for calculating N fertilizer doses for oil-seed rape. The evaluation was performed using simple models of yield, grain oil content, and residual soil mineral nitrogen responses to applied N. The models were fitted to 53 fertilizer trials carried out in France between 1993 and 1999. The results show that the use of the balance-sheet method decreases the variability of farmers' income, increases grain quality, and decreases the risk of water pollution by nitrate.
A Europe-wide survey was conducted by sending questionnaires to weed scientists in order to evaluate currently troublesome weeds and those which may cause problems in the future. Recipients were asked to list species that are spreading and cause problems in agroecosystems, and to rate these according to three scores (degree of weediness, degree of spread potential, and degree of control success), with three levels for each score (low, medium and high). In total, 281 species were reported from 26 European countries. Most of them were annuals (48%), followed by perennials (34%) and biennials (14%). There were significant differences in weed scores among these life forms. Weed scores were unrelated to each other, implying that they have different meanings with respect to the biology of the species. Weed scores did not correlate with European range size, implying that they indicate the weediness of the species independently of the geographical distribution and can be used to prioritize weed species for management.
In a context of rationalised agriculture integrating the principles of sustainable development, preventive measures for crop protection are called upon to play a dominant role. These preventive measures are based on close knowledge of the functioning of agroecosystems. They are aimed at managing biological pests and their natural enemies, first through action on their habitats both in crop fields and in the non-cultivated part of the farm. A balance of the biological control possibilities available is drawn up and attention paid to the application of recent knowledge in conservation biology. The bases of pest control with a ranking of the various intervention techniques are then set out. Implementation means the development of cropping systems and therefore increased participation by agronomists and also a break with certain agronomic practices commonly used by farmers today.
Wastewaters are increasingly used for irrigation of cropping systems in Tunisia. However, to develop environmentally sound practices the contribution of wastewater to crop N nutrition needs to be clarified, especially in cropping systems already receiving mineral fertilizers. For a better understanding of the interaction between fertilizer N and N originating from wastewater, experiments using N-15 were conducted. N-15-labeled fertilizer was applied at different rates (0, 60, 100 and 140 kg N.ha(-1)) and with different water irrigation qualities (tap water or treated wastewater) to sorghum grown in lysimeters during 1998 and 1999. Recovery of N-15-labeled fertilizer in the above-ground crop at final harvest in treated wastewater irrigation was higher at the lowest rate of fertilizer application (54%), with the amount recovered in the crop increasing as the rate of N-15-labeled fertilizer application increased up to the rate of 100 kg N.ha(-1). Nevertheless, in spite of this increase in N-15-labeled fertilizer in the crop, total plant N uptake did not differ between rates. Treated wastewater irrigation had no negative effect on the recovery of N-15-labeled fertilizer. About 62 and 55% of N-15-labeled fertilizer was removed by Sudangrass in either tap water or treated wastewater. Neither fertilizer N rate nor water quality had an effect on the N-15-labeled fertilizer remaining in the soil at final harvest. On average 20% in the wastewater treatment (19-24%) and 30% in the tap water treatment (26-31%) of the N-15 fertilizer applied were in the 0-60 cm layer of soil at final harvest in 1998 and 1999, respectively, and mostly present in the 0-20 cm layer. The proportion of applied N-15-labeled fertilizer remaining in the soil at final harvest increased with increasing N rates. About 60, 69 and 72% of N-15 left in the soil at final harvest was in the surface 0-20 cm layer. Residual N-15 was greatly higher in soil following the first harvest than after the final harvest, with the greatest value (38%) measured at the lowest rate of N-15-labeled fertilizer (30 kg N.ha(-1)). Losses of N-15-labeled fertilizer increased with application rate, but were unaffected by water quality irrigation. Approximately 13% of the applied N-15 fertilizer was lost following the application of 100 kg N.ha(-1) with either treated wastewater or tap water irrigation.
Biodiversity has become a central concept in agronomical research since the Rio de Janeiro summit in 1992. Agricultural areas include a unique biological diversity which is the basis of human activities. Conservation of this biodiversity in agricultural and protected areas is therefore fundamental and requires an operational approach. Biodiversity is a complex entity which can be spread over several levels (genes, species, ecosystems and ecological processes) and can be related to three main functions: (a) patrimonial functions, (b) agronomical functions and (c) ecological functions. The patrimonial function concerns conservation of aesthetic of landscape and threatened species. Biodiversity function according to relationships with agricultural activities describes the biotic and abiotic stress resistance, and the production of cultivated ecosystems. Biodiversity is also involved in ecological functioning by the existence of typical habitats with particular species. The relevance of assessment tools is required in order to understand and evaluate the impact of farm practices on the different compartments of biodiversity at the patch scale to the landscape scale. Different methods, like direct measurements with biodiversity indexes, biotic indicators and models are described and their suitability and limits are discussed.
