Contrasting yield responses at varying levels of shade suggest different suitability of crops for dual land-use systems. A meta-analysis.

Abstract

Despite the large body of research studying crop growth parameters, there is still a lack of systematic assessments on how harvestable yields of different crop types respond to varying levels of shading. However, with the advent of agrivoltaic (AV) systems, a technology that combines energy and food production, and the new focus on agroforestry (AF), shade tolerance is becoming an important parameter for crop production systems. To address this research gap, a meta-analysis with data from two experimental approaches (intercropping and artificial shading with cloths, nets or solar panels) was performed to quantitatively assess the susceptibility of different temperate crop types to increasing levels of shading. Crop type specific yield response curves were estimated as a function of reduction in solar radiation (RSR), by estimating relative crop yields compared to the unshaded controls. Only studies that reported RSR and crop yield per area in temperate and subtropical areas were included. Using a random slope effect for each study, the specific variance components were accounted for. The results suggested a nonlinear relationship between achieved crop yields and RSR for all crop types. Most crops tolerate RSR up to 15%, showing a less than proportionate yield decline. However, significant differences between the response curves of different crop types existed: Berries, fruits and fruity vegetables benefited from shading up to RSR of 30%. Forages, leafy vegetables, tubers/root crops and C3 cereals showed initially less than proportionate crop yield loss. In contrast, maize and grain legumes experienced strong crop yield losses even at low RSR levels. The results provide first indicators for differences in crop type suitability to shading, and thus for AV and AF systems. Detailed yield response curves, as provided in this study, are valuable tools to optimize the output of annual crop components in AV and AF systems.

Relay intercropping of maize with common dry beans to rationalize nitrogen fertilizer

“…Furthermore, the higher yield and yield components of common beans under sole cropping system may be related to the absence of shading effect of maize, and then plants can intercept light to their potential and grow vigorously opposite to intercropped beans. The results corroborate previous maize-beans intercrop studies (Alemayehu et al, 2018;Nassary et al, 2020;Laub et al, 2021).…”

“…Sowing date of maize in relay intercropping systems affects the growth mostly through its determination of the shading duration, where two crop species in the early sown maize system suffer from shading for a longer period of time (Ahmed et al, 2018(Ahmed et al, , 2020. Laub et al (2021) stated that maize and grain legumes experienced strong crop yield losses even at low RSR (reduction in solar radiation) levels.…”

Experimental results, integrated model validation, and economic aspects of agrivoltaic systems at northern latitudes

“…The crop output depends on the APV configuration, such as the PV modules density per hectare and related shading levels, geographical location of the system, specific weather conditions, and crop type. The yield Y that can be lower or higher than the crop yield in the reference agricultural land, i.e., Y crop production can be lower or higher than 100% (Laub et al, 2021). For example, a typical case of higher crop production under an APV system is connected to the installation in arid or semi-arid regions (Barron-Gafford et al, 2019).…”