Diagnosis of limiting factors of organic oilseed rape yield. A survey of farmers’ fields

Abstract

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Diagnosis of limiting factors of organic oilseed rape yield. A survey of farmers' fieldsMuriel Valantin-Morison, J.M. Meynard To cite this version: Muriel Valantin-Morison, J.M. Meynard. Diagnosis of limiting factors of organic oilseed rape yield. A survey of farmers' fields. Agronomy for Sustainable Development, Springer Verlag/EDP Sci-Abstract -The yield of organic winter oilseed rape (WOSR) crop is low and variable in organic farming, but the reasons responsible for this problem are not clear. Aiming to identify the factors affecting organic oilseed rape yields, we carried out a diagnostic study on a network of 19 farmers' fields in four contrasting regions of France over a two-year period. Weed density and biomass, nitrogen absorption by the crop and by weeds, and nutrient availability in the soil, as well as the occurrence of pests and diseases, were assessed at four developmental stages. A range of possible limiting factors throughout the crop cycle led us to use a regression procedure for different periods, using the yield components during spring and biomass during autumn as dependent variables. We identified factors limiting yield and the critical time points at which they acted, which has never been done. Yield variation was strongly correlated with number of grains.m −2 . Dry biomass of weeds, nitrogen uptake by weeds and density of weeds appeared to explain 39% of variation in crop biomass in early winter, while pollen beetle and rape stem weevil damage explained 4.5% and 12% of variation in the number of flowers.m −2 and the number of branches.m −2 , respectively. Crop nitrogen deficiencies occurring before branching were strongly correlated with weed biomass in flowering. Analysis of covariance showed that sowing date, soil management and the quantity of organic manure application may have significantly affected the nitrogen nutrition index, nitrogen uptake by plants and ratio of weed biomass: a late sowing date and shallow soil tillage were related to a low crop nitrogen nutrition index and high ratio of weed biomass. From a practical point of view, this study demonstrated that it should be possible to reduce weed competition by ensuring that the amount of nitrogen in soil before sowing is around 100 kg/ha. winter oilseed rape / organic farming / yield variability / yield components / diagnosis / farmers' fields / nitrogen deficiencies / weed competitio * Corresponding authors: morison@grignon.inra.fr, meynard@grignon.inra.fr Article published by EDP Sciences and ava...

Occurrence of fungal and pesticides contamination in rapeseeds depending on the cultivars and systems of farming

“…In our experiments only in case of A. brassicicola and L. maculans were observed differences between seed infestation in both cultivation systems. This observation could be connected with cultivation system but also it is possible that other characteristics connected of given cultivar may be of importance such as genetic resistance, response to weather condition or fertilization (Valantin-Morison and Meynard 2008). Our results confirm also variation in cultivar susceptibility to infestation and colonisation by individual fungal species.…”

Potential for oilseed rape resistance in pollen beetle control

“…Since pollen beetle resistance to pyrethroids, the main insecticides used against this species, has been increasing in natural populations over the last 40 years (Lakocy 1977;Hansen 2003;Slater et al 2011;Heimbach and Müller 2012;Wrzesińska et al 2014;Zimmer et al 2014), research has been ongoing in order to develop a number of alternative control strategies within the framework of integrated pest management. Strategies tested include trap cropping using early-flowering plants (Cook et al 2004a(Cook et al , 2006(Cook et al , 2007Nerad et al 2004;Nilsson 2004;Frearson et al 2005) or companion plants (Veromann et al 2012;Kaasik et al 2014a, b), enhancement of biological control through the attraction of larval parasitoids (Büchi 2002;Scheid et al 2011;Kovács et al 2013;Kaasik et al 2014a, b) or spraying of entomopathogenic fungi (Hokkanen 1993;Husberg and Hokkanen 2001) or nematodes (Nielsen and Philipsen 2005), adapting agronomical practices (Valantin-Morison et al 2007;Valantin-Morison and Meynard 2008;Veromann et al 2009Veromann et al , 2013, diffusing repellent volatile compounds (Mauchline et al 2005(Mauchline et al , 2008(Mauchline et al , 2013Pavela 2011) or using botanical insecticides (Pavela 2011;Dorn et al 2014).…”

Reframing the Debate Surrounding the Yield Gap between Organic and Conventional Farming

“…Insect herbivory is the limiting factor in this case, and there are no effective organic methods of pest control available, especially with regards to the pollen beetle (Meligethes aeneus). Weed pressure at sensitive developmental stages also affects yields [65], but the yield gap is primarily explained by the differences in plant protection agents. Here, it would make little sense to first try to increase nutrient availability to make organic oilseed rape cultivation more feasible; research into organic pest control methods must be prioritized.…”