Impact of spatio-temporal shade dynamics on wheat growth and yield, perspectives for temperate agroforestry

Abstract

a b s t r a c tA stumbling block to the adoption of silvoarable agroforestry systems is the lack of quantitative knowledge on the performance of different crops when competing for resources with trees. In North-Western Europe, light is likely to be the principal limiting resource for understorey crops, and most agronomic studies show a systematic reduction of final yield as shade increases. However the intensity of the crop response depends on both the environmental conditions and the shade characteristics. This study addressed the issue by monitoring winter wheat (Triticum aestivum L.) growth, productivity and quality under artificial shade provided by military camouflage shade-netting, and using the Hi-sAFe model to relate the artificial shade conditions to those applying in agroforestry systems.The field experiment was carried out over two consecutive years (2013-14 and 2014-15) on the experimental farm of Gembloux Agro-Bio Tech, Belgium. The shade structures recreated two shade conditions: periodic shade (PS) and continuous shade (CS), with the former using overlapping military camouflage netting to provide discontinuous light through the day, and the latter using conventional shade cloth. The experiment simulated shading from a canopy of late-flushing hybrid walnut leaves above winter wheat. Shading was imposed 16 (2013-14) and 10 (2014-15) days before flowering and retained until harvest. The crop experienced full light conditions until the maximum leaf area index stage (LAI max ) had been reached. In both years, LAI followed the same dynamics between the different treatments, but in 2013-2014 an attack of the take-all disease (Gaeumannomyces graminis var. tritici) reduced yields overall and prevented significant treatment effects. In season 2014-15 the decrease in global radiation reaching the crop during a period of 66 days (CS: -61% and PS: -43%) significantly affected final yield (CS: -45% and PS: -25%), mainly through a reduction of the average grain weight and the number of grain per m 2 . Grain protein content increased by up to 45% under the CS treatment in 2015. Nevertheless, at the plot scale, protein yield (t/ha) did not compensate for the final grain yield decrease.The Hi-sAFe model was used to simulate an agroforestry plot with two lines of walnut trees running either north-south or east-west. The levels of artificial shade levels applied in this experiment were compared to those predicted beneath trees growing with similar climatic conditions in Belgium. The levels used in the CS treatment are only likely to occur real agroforestry conditions on 10% of the cropped area until the trees are 30 years old and only with east-west tree row orientation.

How does STICS crop model simulate crop growth and productivity under shade conditions?

“…Field observations showed that applying a shade treatment during a pre-(7-10 days) and post-flowering period of winter wheat leads to a decrease of the overall plant biomass as well as a decrease of the grain number per m 2 and the final grain weight. This is in accordance with a large body of literature on the subject (Artru et al, 2017;Demotes-Mainard and Jeuffroy, 2004;Dufour et al, 2013;Fischer, 1985;Sinclair and Jamieson, 2006). The literature suggests that the final grain yield depends on the grain number determination and on the remobilization of the pre-flowering reserve as well as on the photosynthesis occurring during the grain filling period (Bijanzadeh and Emam, 2010;Boiffin and Caneill, 1981;Gate, 1995).…”

“…The measurements were performed on dried samples. More details on the experimental setup are published in Artru et al (2017).…”

“…Typically, in such models the radiation received by the crop is summarized by the daily cumulated global radiation. Nevertheless, several studies highlighted that a decrease in vegetative growth is observed under a fluctuating and heterogeneous light environment, the decrease in biomass being however not proportional to the light reduction (Artru et al, 2017;Dufour et al, 2013;Liu, 1991;Pearcy et al, 1996;Peri et al, 2002). From a physiological point of view, daily biomass growth of plants growing in a complex light environment can therefore not be estimated correctly from a daily cumulated value of the global radiation.…”

Spatial diversification of agroecosystems to enhance biological control and other regulating services: An agroecological perspective

“…The presence of trees within fields would also create a microclimate with potential benefits, but also deficits for ecosystem functioning. Shade due to trees for example, may protect crops from the sun improving their nutritive quality as it was reported for forage species in the USA (Lin et al, 2001), but was also shown to reduce yield of associated wheat in Belgium (Artru et al, 2017).…”

Análisis comparativo del funcionamiento de distintas tecnologías de paneles solares operando en las mismas condiciones

“…It requires the proper balance that the PV system and agriculture activities avoid interaffecting each other dramatically. The negative influence on durum wheat quality such as grain size due to heavy shade has been justified in some agroforestry works (Artru et al, 2017;Dufour et al, 2013). Therefore, the recommended AV farm configuration for durum wheat is The levelized cost of electricity (LCOE) is an economic assessment of the overall cost of the generated electricity over lifetime considering subsidies (i.e., feed-in tariff, net-metering) and incentives (i.e., free or low interest loan).…”