Darwinian agriculture (also called Evolutionary agroecology) which focuses on the trade-off between individual fitness and community performance, can provide an efficient approach to enhance crop production. However, evolutionary or ecological processes, in particular the tragedy of the commons in crops, remain poorly understood. We used a pot experiment to examine whether wheat plants fell into this ‘tragedy’ when confronted with roots of an intra-variety neighbour and how the magnitude was influenced by soil fertility. Two varieties (old landrace Monkhead and modern variety 92-46) were selected for this study. Root competition scenarios were set by growing two plants of the same variety with a mesh or plastic partition. Soil fertility gradients were set by adding nutrient solutions with low or high application frequency. Biomass were tested and allometric relationship were analyzed to reveal resource allocation pattern. Old Monkhead had similar relative allocation to root biomass with modern 92-46, but had greater relative allocation to stem&leaf biomass and lower relative allocation to seed biomass. The presence of neighbour affected allometric relationships only in 4 out of 24 allometic comparisons, which all appeared in low fertility treatments. Fertilizer addition increased stem&leaf biomass allocation of Monkhead and decreased root and seed biomass allocation at the same time. By contrast, stem&leaf and seed allocation of 92-46 was not changed by fertilizer addition although root allocation was decreased. Our results demonstrated that there was a trade-off between non-reproductive and reproductive allocation for wheat varieties. There was not notable tragedy of the commons in wheat varieties, although a small degree was observed in Monkhead. Moreover, the occurrence and magnitude of the tragedy was dependent on resource availability and variety resource-use strategy. Our results underlie the importance of understanding the mechanisms behind the tragedy of the commons in crop varieties with different ecological strategies, and provide insights into the role of Darwinian agriculture in global food production.

Facilitation events were mostly reported in two modes of mutual promotion (+/+) and unilateral benefit (+/0) in cultivated plant populations, yet few investigations showed the third mode, i.e. +/-. We investigated the maize-faba bean intercropping system as the third mode which was little documented. Land equivalent ratio in intercropping system was significantly greater than in monocropping one, with faba bean as superior species (+), and maize as inferior species (-). For inferior species, interspecific competition restricted its substance remobilization and seed filling, and caused a relatively low pollen fertilization rate and high kernel abortion rate. This trend resulted from lower soil water availability in maize strip of intercropping system, and lower leaf chlorophyll content and photosynthetic rate in maize. Yield loss of inferior species provided mechanical explanation on the concurrent +/- facilitation. The findings enriched our understandings on asymmetric facilitation and the relationship between plant diversity and productivity in agroecosystems.

Nanoscale zero-valent iron (FeNPs) can affect plant growth and water uptake positively or negatively. Yet, its mechanism is still unclear, particularly for differentiate functional roles of FeNPs in plant-soil interaction. To address this issue, we first confirmed 1.0 and 1.5 g·kg-1 FeNPs as growth-promotion concentrations and 1.5 g·kg-1 as optimal one, while 2.0 g·kg-1 turned to restrict growth in maize seedlings, comparing with CK. When AM fungus (Funneliformis mosseae) was inoculated and cultured with FeNPs, 1.0 and 1.5 g·kg-1 FeNPs further evidently enhanced water uptake and biomass accumulation (P<0.05). ), as affected by the activated AMF colonization carrier. Contrarily, FeNPs turned to promote AMF colonization and development, achieving greater iron translocation efficiency in mycorrhiza (P < 0.05). Yet, 2.0 g·kg-1 FeNPs restricted AMF infection in roots, a negative effect. To investigate the mycorrhizal-FeNPs symbiosis, scanning electron microscopy was used to scan the extraradical hyphae, showing that hyphae intercepted excessive iron nanoparticles, alleviating the blockage of root surface apertures and ultimately restoring root activity. Therefore, dual effects of FeNPs on maize physiology were actively mediated by AMF via rhizosphere interactions. The findings provided new insights into safe and efficient utilization of nanomaterials in agro-ecosystems.