Crop yield mainly depends on environment and cultivation practices that vary according to a growing environment. However, an oat (Avena sativa L.)-common vetch (Vicia sativa L.) intercrop system has not been fully developed in the agro-pastoral ecotone of Inner Mongolia, China. This study evaluated the effects of seven treatments, including five oat-common vetch intercropping patterns, sole oat, and sole vetch on yield and quality performance at different growth periods [75 days after sowing (DAS), 90 DAS, 105 DAS], on the basis of field experiments conducted in the agro-pastoral ecotone of Inner Mongolia in 2015 and 2016. The OV3:1 (oat intercropped with common vetch at seeding ratios 3:1) treatment at 105 DAS in 2016 was superior to other treatments, as it achieved the highest shoot dry matter, increasing by 24.1% and 37.1% compared to sole oat and common vetch. The crude fat (CF) contents, CF yield, and crude protein (CP) yield increased under OV3:1, and acid detergent fiber (ADF) decreased under OV3:1, compared to monoculture. The results indicate that intercropping is an efficient cropping system for the agro-pastoral ecotone of Inner Mongolia. The appropriate proportion of oat and common vetch intercropping at 3:1 and harvesting time not only increases crop yield but also improves the crop quality.

Plant growth and production are more severely inhibited by alkalinity than by salinity. However, the metabolites responsible for the reduced growth caused by alkalinity are largely unknown. Here, the Illumina RNA-Seq analysis and targeted metabolome were used to identify the differentially expressed genes and metabolites responding to salt and alkali stresses. The expression levels of eight genes related to photosynthesis and some genes related to chlorophyll synthesis decreased under alkali stress, whereas no changes were detected under salt stress, which may explain the observed lower level of photosynthetic rate in alkalinity than in salinity. Under alkali stress, significant decreases in the relative abundances of cis-cinnamic acid and scopoline were observed, which correlated with the high levels of reactive oxygen species (ROS). The levels of protocatechuic acids decreased, correlating with the observed decrease in the chlorophyll content. Alkalinity markedly increased the production of o-coumaric acid, which contributes to growth inhibition. No significant changes in cis-cinnamic acid, scopoline, and o-coumaric acid were detected in salinity, which may be the reason for the stronger growth inhibition due to alkali stress than salt stress. The accumulation of citric acid, serotonin, pyroglutamic acid, L-citrulline, ferulic acid, and caffeic acid was detected under salt and alkali stress conditions, indicating high free radical scavenging capacity. The enhancement of mevalonic acid and salicylic acid levels was detected under alkali stress, which could have facilitated chlorophyll accumulation. Salt and alkali stress conditions also led to the accumulation of cyclic AMP related to inorganic ion regulation and betaine-related osmoregulation. Benzamide, phenethylamine, N-feruloyltyramine, chrysoeriol 6-C-hexoside, 1,3-o-di-p-coumaroyl glycerol, cordycepin, and 1-o-p-cumaroylglycerol were identified to be accumulated in response to alkali stress.