Since the introduction of mechanized production in both developed and developing countries, crops and their management have undergone significant adaptation resulting in increased productivity. Historical yield increases in wheat have occurred across most regions of the world (20–88 kg ha⁻¹ year⁻¹), but climate trends threaten to dampen or reverse these gains such that yields are expected to decrease by 5–6% despite rising atmospheric CO₂ concentrations. Current and projected climatic factors are temporally and spatially variable in dryland cereal production systems throughout the world. Productivity gains in wheat in some locations have been achieved from traditional agronomic practices and breeding. Continued improvement in all cereal production regions and locations of the world requires technical advances, including closer monitoring of soils, water conservation strategies, and multiple sowing times using different crops to reduce risks. The management of disease, pests, and weeds will be an added challenge, especially in areas of higher precipitation. Excellent progress has been achieved in Asia and there is much potential in Sub-Saharan Africa. Technical solutions seem within our grasp but must be implemented in the context of variable social, economic, regulatory, and administrative constraints, providing opportunities for cross fertilization and global collaboration to meet them.

China is a major producer of green tea, and most of its green tea production comes from small farmers. Accessing the carbon emission status of this group can provide data support and a decision-making basis for the realization of carbon neutrality in China’s tea industry. In this study, the life cycle assessment method was used to analyze the carbon footprint of green tea produced by smallholder farmers in Liugou Village, Hanzhong City, Shaanxi Province. The results showed that the carbon emission intensity of green tea for its entire life cycle was 32.90 kg CO₂eq kg⁻¹ dry tea, and the carbon emission intensities of its consumption, processing, and cultivation were 14.90, 7.94, and 6.97 kg CO₂eq kg⁻¹, respectively. In the processing stage, emissions during steaming and drying accounted for 57%. The use of coal, complicated processing procedures, and older equipment were the main reasons for the high emissions in the processing stage. In the cultivation process, emissions mainly came from fertilizer production and its application in the field. The energy consumption of boiling water resulted in high carbon emissions in the consumption stage. This study suggests that building a scientific fertilization system for tea gardens, optimizing processing equipment and energy utilization structure, and cultivating the concept of low-carbon consumption will be the keys to promoting smallholder farmers to reduce carbon emissions. This study further emphasizes that we should focus on carbon emissions caused by the production processes of small farmers.

The elevated atmospheric CO₂ concentration (eCO₂) is expected to increase the labile C input to the soil, which may stimulate microbial activity and soil N₂O emissions derived from nitrification and denitrification. However, few studies studied the effect of eCO₂ on N₂O emissions from maize field under the free-air CO₂ enrichment (FACE) conditions in the warm temperate zone. Here, we report a study conducted during the 12th summer maize season under long-term eCO₂, aiming to investigate the effect of eCO₂ on N₂O emissions. Moreover, we tested zero and conventional N fertilization treatments, with maize being grown under either eCO₂ or ambient CO₂ (aCO₂). We hypothesized that N₂O emissions would be increased under eCO₂ due to changes in soil labile C and mineral N derived from C-deposition, and that the increase would be larger when eCO₂ was combined with conventional N fertilization. We also measured the activities of some soil extracellular enzymes, which could reflect soil C status. The results showed that, under eCO₂, seasonal N₂O and CO₂ emissions increased by 12.4–15.6% (p < 0.1) and 13.8–18.5% (p < 0.05), respectively. N fertilization significantly increased the seasonal emissions of N₂O and CO₂ by 33.1–36.9% and 17.1–21.8%, respectively. Furthermore, the combination of eCO₂ and N fertilization increased the intensity of soil N₂O and CO₂ emissions. The marginal significant increase in N₂O emissions under eCO₂ was mostly due to the lower soil water regime after fertilization in the study year. Dissolved organic C (DOC) and microbial biomass C (MBC) concentration showed a significant increase at most major stages, particularly at the tasseling stage during the summer maize growth period under eCO₂. In contrast, soil mineral N showed a significant decrease under eCO₂ particularly in the rhizospheric soils. The activities of C-related soil extracellular enzymes were significantly higher under eCO₂, particularly at the tasseling stage, which coincided with concurrent increased DOC and MBC under eCO₂. We conclude that eCO₂ increases N₂O emissions, and causes a higher increase when combined with N fertilization, but the increase extent of N₂O emissions was influenced by environmental factors, especially by soil water, to a great extent. We highlighted the urgent need to monitor long-term N₂O emissions and N₂O production pathways in various hydrothermal regimes under eCO₂.

Wheat is a target crop within the food security context. The responses of wheat plants under elevated concentrations of CO₂ (e[CO₂]) have been previously studied; however, few of these studies have evaluated several organs at different phenological stages simultaneously under free-air CO₂ enrichment (FACE) conditions. The main objective of this study was to evaluate the effect of e[CO₂] in two cultivars of wheat (Triumph and Norin), analyzed at three phenological stages (elongation, anthesis, and maturation) and in different organs at each stage, under FACE conditions. Agronomic, biomass, physiological, and carbon (C) and nitrogen (N) dynamics were examined in both ambient CO₂ (a[CO₂]) fixed at 415 µmol mol⁻¹ CO₂ and e[CO₂] at 550 µmol mol⁻¹ CO₂. We found minimal effect of e[CO₂] compared to a[CO₂] on agronomic and biomass parameters. Also, while exposure to 550 µmol mol⁻¹ CO₂ increased the photosynthetic rate of CO₂ assimilation (An), the current study showed a diminishment in the maximum carboxylation (V_c,max) and maximum electron transport (J_max) under e[CO₂] conditions compared to a[CO₂] at physiological level in both cultivars. However, even if no significant differences were detected between cultivars on photosynthetic machinery, differential responses between cultivars were detected in C and N dynamics at e[CO₂]. Triumph showed starch accumulation in most organs during anthesis and maturation, but a decline in N content was observed. Contrastingly, in Norin, a decrease in starch content during the three stages and an increase in N content was observed. The amino acid content decreased in grain and shells at maturation in both cultivars, which might indicate a minimal translocation from source to sink organs. These results suggest a greater acclimation to e[CO₂] enrichment in Triumph than Norin, because both the elongation stage and e[CO₂] modified the source–sink relationship. According to the differences between cultivars, future studies should be performed to test genetic variation under FACE technology and explore the potential of cultivars to cope with projected climate scenarios.

Recently, several reports have suggested that the growth and grain yield of wheat are significantly influenced by high atmospheric carbon dioxide concentration (CO₂) because of it photosynthesis enhancing effects. Moreover, it has been proposed that plants with large carbon sink size will benefit more from CO₂ enrichment than those with small carbon sink size. However, this hypothesis is yet to be test in winter wheat plant. Therefore, the aim of this study was to examine the effect of elevated CO₂ (eCO₂) conditions on the quantum efficiency of photosystem II (PSII) photochemistry in large ear-type (cv. Shanhan 8675; greater ear C sink strength) and small multiple ear-type (cv. Early premium; greater vegetative C source strength) winter wheat varieties. The experiment was conducted in a free air CO₂ enrichment (FACE) facility, and three de-excitation pathways of the primary reaction of PSII of flag leaf at the anthesis stage were evaluated under two CO₂ concentrations (ambient [CO₂], ∼415 μmol⋅mol^–1, elevated [CO₂], ∼550 μmol⋅mol^–1) using a non-destructive technique of modulated chlorophyll fluorescence. Additionally, the grain yield of the two varieties was determined at maturity. Although elevated CO₂ increased the quantum efficiency of PSII photochemistry (Φ_PSII) of Shanhan 8675 (SH8675) flag leaves at the anthesis stage, the grain number per ear and 1,000-kernel weight were not significantly affected. In contrast, the Φ_PSII of early premium (ZYM) flag leaves was significantly lower than that of SH8675 flag leaves at the anthesis stage, which was caused by an increase in the regulatory non-photochemical energy dissipation quantum (Φ_NPQ) of PSII, suggesting that light energy absorbed by PSII in ZYM flag leaf was largely dissipated as thermal energy. The findings of our study showed that although SH8675 flag leaves exhibited higher C sink strength and quantum efficiency of PSII photochemistry at the anthesis stage, these factors alone do not ensure improved grain yield under eCO₂ conditions.

The effects of elevated CO₂ concentration (eCO₂) on the utilization of carbohydrates in wheat cultivars with different ear types remain poorly understood, despite the critical role of wheat ears as major carbohydrate sinks and the importance of ear type as a key growth trait influencing crop yield. In this study, a free-air CO₂ enrichment (CAAS-FACE) facility was utilized to investigate the effects of eCO₂ on the non-structural carbohydrate (NSC) utilization in two wheat cultivars: a large-ear cultivar (cv. Shaanhan 8675) and a multiple-ear cultivar (cv. Triumph). The findings demonstrated that under eCO₂ conditions, Shaanhan 8675 exhibited enhanced NSC availability and more efficient remobilization from vegetative organs to grains. This improvement was associated with sustained photosynthetic activity in the leaves during the grain-filling period, which contributed to better grain filling. Consequently, both grain NSC accumulation and kernel weight were significantly increased in Shaanhan 8675 under eCO₂. In contrast, the grain NSC accumulation in Triumph was constrained by limited translocation of NSC from the stem and ear to the grain under eCO₂ environment. Overall, our findings suggest that CO₂ enrichment has a pronounced positive effect on NSC utilization in large-ear wheat cultivars. These results contribute to strategies aimed at ensuring stable and high wheat yields under future climatic conditions.