Nitrogen management of organic winter wheat Decision-making through model-based explorations

In organic wheat, nitrogen is one of the key limiting factors responsible for irregular productivity and low quality (David et al, 2005b), 5 to 50 % less than conventionally managed crops (Nieberg and Schulze Pals, 1996). On arable farms, the decreasing use of N-organic sources such as forage legumes, manures and composts relative to mixed-farms requires the development of suitable fertility strategies based on the use of off-farm organic fertilizers. Numerous mechanistic crop models simulating the dynamics of crop requirements and N supply in the soil (e.g. CERES, EPIC, APSIM, ARCWHEAT STICS) have previously been developed (Whisler et al, 1996). Although these models are highly used in research, their complexity and input requirements have limited their practical use for farmers and advisers. The aim of this study was to develop an engineering approach (Passioura, 1996) by the development of a decision-making tool for assessing N management of organic wheat on commercial farms. Azodyn-Org crop model was developed in organic agriculture to predict the influence of spring N fertilization strategies on grain yield, grain protein content, mineral N in the soil at harvest and gross margin (David et al., 2004). This simpler model requires little input data, which are easily measured in farmers’ fields (soil characteristics, climatic data, crop biomass and mineral N in the soil at the end of winter). The performance of Azodyn-Org was relevant for selecting appropriate strategies in a large range of environment and crop management conditions (David et al., 2005a). This paper focuses on the potential contribution of model-based explorations from Azodyn-Org for managing N fertilization in organic wheat crops at the regional scale

Indicators of weed competition on Organic Winter Wheat

Organic winter wheat production is limited by climatic and agronomic factors, including weed competition. The incidence of weeds on yield limitation can be characterized through various early indicators to predict weed occurrence and competition. A network of 10 fields of organic winter wheat was implemented in the South East of France in 2005-2006. Results showed that weed density, dynamics and diversity are good indicators for weed occurrence and competition

Improvement of the soil-crop model AZODYN under conventional, low-input and organic conditions

The use of mechanistic crop modelling, simulating the dynamics of crop N requirements and nitrogen supply from the soil and fertilizers, can provide sound advice to users. This paper describes a methodological way to improve soil-crop modeling used for N management of conventional and organic wheat

Wheat/forage legume intercropping in organic grain system: an answer to both weed and nitrogen deficiency issues

Organic grain system managers have to find solutions to nitrogen deficiency and weed infestation. It is especially true when no animals are present on the farm to justify the use of forage legumes despite their interests in the crop succession. Our study focused on the role of four legume cover crop species inserted in a succession of winter wheat and maize on both problems. This insertion consisted in relay-intercropping the legumes under the canopy of wheat. Cover crops were maintained on the field after the harvest of the cereal until the sowing of the subsequent maize crop. The performance of the three crops of the succession was monitored as well as weed development and nitrogen dynamic in the soil-plant system. On the one hand, our results showed that black medic and red clover, that supported the best the competition of wheat, were likely to decrease its grain protein content at harvest (-0.3 to -0.4 %). On the other hand, the four species did not decrease intercropped wheat grain yield. They were able to control weed infestation during the intercropping period and between the two cash crops. Finally, nitrogen restitution to the subsequent maize crop was efficient and allowed a significant 30 % increase of maize grain yield

Agronomical techniques to improve technological and sanitary quality

In spite of variable grain protein contents, baking quality of organic wheat was found to be acceptable to good. Mycotoxin (DON) infestation was generally low on tested grain samples. Choice of wheat cultivar was the most efficient way to obtain higher grain quality. Fertilization with readily available nitrogen and, to a lower extent, association with legumes and green manures with mixtures containing fodder legumes also improved grain quality. Reduced tillage affected soil quality and wheat yield but had little effects on grain quality

Ambitious environmental and economic goals for the future of agriculture are unequally achieved by innovative cropping systems

International audienceAgriculture has to face huge challenges in the decades ahead. Four innovative cropping systems were assessed ina “cropping system experiment” in the Ile-de-France region (France) from 2009 to 2014. Three were designed tomeet ambitious goals: the total elimination of pesticides (No-Pest), reducing fossil energy consumption by 50%(L-EN), or decreasing greenhouse gas (GHG) emissions by 50% (L-GHG). They were also required to satisfy awide range of environmental criteria and to maximize yields whilst respecting the major constraint on the systemand the environmental targets set. A fourth system (PHEP), in which the environmental and yield targets wereachieved with no major constraint, was also assessed. After completion of the first full crop sequence for theseinnovative systems, the results obtained indicated that it was possible to design and implement innovativesystems achieving multiple goals. In our field trial conditions, the pesticide and energy constraints were almostsatisfied, whereas the GHG target was missed by a considerable margin. All four innovative systems satisfiedenvironmental criteria in terms of N management, pesticide use, energy consumption and crop diversity.However, herbicide treatment frequency index (TFIH) was higher than expected in the two systems with no-plowpractices, L-EN and L-GHG. In the pesticide-free system, soil organic matter content was lower than expected,due to frequent plowing (every 2 years) and low residue levels as a result of the lower yields obtained. Yieldswere lower for the L-EN system than for the reference system, and yield was variable in the L-GHG system. Theseinnovative systems had better environmental performances than the systems currently used in the Ile-de-Franceregion, with no decrease in gross margins

Techniques to improve technological and sanitary quality

The demand for high quality organic bread cereals is increasing. In spite of variable grain protein contents, baking quality of organic wheat was found to be acceptable to good. Mycotoxin (DON) contents were generally low on tested grain samples. Choice of the wheat cultivar is the most efficient way to obtain higher grain quality. Fertilization with readily available nitrogen and, to a lower extent, association with legumes and green manuring with mixtures containing fodder legumes can also improve grain quality. Reduced tillage affects soil quality and wheat yield but has little effects on grain quality

Technological quality of organic wheat in Europe

The demand for high quality organic bread wheat is increasing. The quality level of organic wheat harvested in EU is mainly dependant on variety, environmental conditions and agronomic practices. In some countries, protein content and composition, influencing technological value, are equivalent to those produced under conventional practices. Beside agronomical techniques, technological processes can help to maintain a good quality. Pre-treatments before milling such as debranning were found to be efficient in reducing DON contamination. The project highlighted the necessity to redefine the methods to assess the quality of organic wheat

Genèse de la recherche sociologique en Allemagne

On s’interrogera ici sur la dynamique d’un groupe de recherche et de promotion de la recherche, l’« Association de politique sociale » (Verein für Sozialpolitik). On envisagera notamment comment elle sélectionne et conditionne des chercheurs et comment le développement de cette association conduit à lancer une série d’enquêtes. Max Weber est membre de cette association, co-directeur des enquêtes sur les ouvriers d’industrie, enquêteur dans une fabrique textile. On se propose de montrer quel c..