Elevated atmospheric CO
2
(eCO
2
) enhances the yield of vegetables and could also affect their nutritional quality. We conducted a meta-analysis using 57 articles consisting of 1,015 observations ...and found that eCO
2
increased the concentrations of fructose, glucose, total soluble sugar, total antioxidant capacity, total phenols, total flavonoids, ascorbic acid, and calcium in the edible part of vegetables by 14.2%, 13.2%, 17.5%, 59.0%, 8.9%, 45.5%, 9.5%, and 8.2%, respectively, but decreased the concentrations of protein, nitrate, magnesium, iron, and zinc by 9.5%, 18.0%, 9.2%, 16.0%, and 9.4%. The concentrations of titratable acidity, total chlorophyll, carotenoids, lycopene, anthocyanins, phosphorus, potassium, sulfur, copper, and manganese were not affected by eCO
2
. Furthermore, we propose several approaches to improving vegetable quality based on the interaction of eCO
2
with various factors, including species, cultivars, CO
2
levels, growth stages, light, O
3
stress, nutrient, and salinity. Finally, we present a summary of the eCO
2
impact on the quality of three widely cultivated crops, namely, lettuce, tomato, and potato.
Aims
Studies dealing with plants’ mineral nutrient status under elevated atmospheric CO
2
concentration (eCO
2
) are usually conducted in closed hydroponic systems, in which nutrient solutions are ...entirely renewed every several days. Here, we investigated the contribution of the fluctuation of concentrations of N (N), P (P), and K (K) in nutrient solutions in this short period on their concentrations in cucumber plants exposed to different CO
2
and N levels.
Methods
Cucumber (
Cucumis sativus
L.) plants were hydroponically grown under two CO
2
and three N levels. N, P, and K in nutrient solutions and cucumber plants were analyzed.
Results
The transpiration rate (Tr) was significantly inhibited by eCO
2
, whereas Tr per plant was increased due to the larger leaf area. Elevated CO
2
significantly decreased N in low N nutrient solutions, which imposed an additional decrease in N in plants. P in nutrient solutions fluctuated slightly, so the change of P in plants might be attributed to the dilution effect and the demand change under eCO
2
. K in moderate and high N nutrient solutions were significantly decreased, which exacerbated the K decrease in plants under eCO
2
.
Conclusions
The short-term fluctuation of N and K in nutrient solutions is caused by the asynchronous uptakes of N, K, and water under eCO
2
, which has an appreciable influence on N and K in plants besides the dilution effect. This defect of the closed hydroponic system may let us exaggerate the negative impact of eCO
2
itself on N and K in plants.
•Elevated CO2 (ECO2) decreased amoA-AOB, nxrA copy numbers and nitrification rate.•Elevated soil temperature (EST) increased mineralization and nitrification rates.•EST increased chiA and amoA-AOB ...gene copy numbers and alpha diversity.•ECO2 and EST promoted mineralization, nitrification, and immobilization rates.•ECO2 and EST accelerated N circulation and mitigated N loss in greenhouse soil.
Climate change scenarios forecast both increase in atmospheric CO2 concentration (CO2) and temperature. Elevated CO2 (eCO2) and soil temperature (eST) significantly increased plant growth and nitrogen (N) uptake. However, studies on the combined effect of these factors on soil N transformation and microbial community are scarce in agricultural intensification. In the present work, we cultivated cucumber plants under eCO2 or/and eST, followed by a paired labeling 15N tracer experiment (15NH4NO3 and NH415NO3) to quantify soil gross N transformation rates. Results showed that eCO2 decreased soil gross N nitrification rate, indicated by a decline in ammonia-oxidizing bacteria (amoA-AOB) and nitrite oxidoreductase alpha subunit (nxrA) gene copy numbers, and changed microbial taxonomic composition under ambient soil temperature (aST). Furthermore, eST increased chitinase gene (chiA) and amoA-AOB gene copy numbers and alpha diversity and changed the microbial taxonomic composition to improve soil gross N mineralization and nitrification rates. The combination of eCO2 and eST promoted soil gross N mineralization, nitrification, and immobilization rates compared with ambient CO2 and aST. The study showed that the combination of eCO2 and eST increased the primary gross N transformation rates and accelerated soil N circulation, which could ensure plant N demand. Therefore, combining eCO2 and eST provided a promising way to help cultivators promote vegetable growth in winter, mitigate soil N loss, and achieve sustainable development in greenhouse vegetable cultivation.
The accumulation of cadmium in rice (
L.) and wheat (
L.) is a serious threat to the safe use of farmland and to the health of the human diet that has attracted extensive attention from researchers. ...In this review, a bibliometric analysis was performed using a VOS viewer (1.6.18, Netherlands) to investigate the status of cadmium contamination in rice and wheat growing systems, human health risks, mechanisms of Cd uptake and transport, and the corresponding research hotspots. It has a certain reference value for the prevention and control of cadmium pollution in rice and wheat planting systems in China and abroad. The results showed that the Cd content in rice and wheat planting systems in the Yangtze River Basin was significantly higher than that in other areas of China, and the Cd content in rice and wheat grains and the hazard quotient (
) in Hunan Province was the highest. The average Cd concentration exceeded the recommended limit by about 62% for rice and 81% for wheat. The main reasons for the high Cd pollution in rice and wheat growing areas in Hunan are mining activities, phosphate fertilizer application, sewage irrigation, and electronic equipment manufacturing. In this review, we demonstrate that cadmium toxicity reduces the uptake and transport of essential elements in rice and wheat. Cadmium stress seriously affected the growth and morphology of plant roots. In the shoots, Cd toxicity was manifested by a series of physiological injuries, such as decreased photosynthesis, soluble protein, sugar, and antioxidant enzyme activity. Cadmium that accumulates in the shoots is transferred to grains and then passes up the food chain to people and animals. Therefore, methods for reducing cadmium content in grains of rice and wheat are urgently needed, especially in Cd-contaminated soil. Current research on Cd pollution in rice and wheat planting systems focuses on the bioavailability of Cd, soil rhizosphere changes in wheat and rice, and the role of antioxidant enzyme systems in alleviating heavy metal stress in rice and wheat.
Fulvic acids are organic compounds widely distributed in soils, and the application of fulvic acids is thought to increase crop yield and quality. However, the effects vary among various sources and ...doses of fulvic acids and environmental and growth conditions of crops. Here, we investigated the effects of bioresource-derived (corn straw) fulvic acids on plant production and quality of tomato plants and soil chemical properties in soil cultures while experiments on seed germination and hydroponics were conducted to explore the underlying mechanism. Base dressing with 2.7 g kg
–1
increased the yield of tomato by 35.0% at most as increased fruit number. Fulvic acids increased the concentrations of minerals, such as Ca, Fe, and Zn and the concentrations of citric, malic, and some amino acids in berries of tomato but did not affect the concentrations of soluble sugars and aromatic substances in tomato fruits. Similarly, fulvic acids at 80–160 mg L
–1
increased germination rate, growth vigor, and radicle elongation of tomato seeds while it increased plant biomass, concentrations of nutrients, and root length of tomato plants in hydroponics to the greatest extent in general. The increases in yield and quality can be attributed to the improvement in root growth and, thus, increased nutrient uptake. In addition, the base application of fulvic acids improved soil cation exchange capacity and soil organic matter to an extent. In conclusion, base dressing and the addition into solution of fulvic acids at moderate doses facilitate root growth and nutrient uptake and, thus, vegetable production and quality; therefore, fulvic acids can be an effective component for designing new biofertilizers for sustainable agricultural production.
Oxamide is a potential slow-release nitrogen (N) fertilizer, especially under waterlogged conditions, due to its low solubility in water and the slow-release of ammonium by soil amidases. To ...investigate the effects of oxamide granules (2.00-2.38 mm in diameter) as a single basal fertilizer (180 or 144 kg N ha−1) on rice growth, soil properties, and N use efficiency in terms of N recovery efficiency (NRE), we conducted field experiments on two different types of paddy soils over two rice-growing seasons. Results showed that the fertilization effects of oxamide granules varied between the two types of paddy soils. In the red clayey paddy soil, the grain yields for both rice-growing seasons were high with a significantly higher NRE in the oxamide treatment than in the urea treatment. However, in the alluvial sandy paddy soil, the grain yields in the oxamide treatment were slightly lower than those in the urea treatment. Furthermore, oxamide produced little improvement in NRE in the alluvial sandy paddy soil. Soil incubation experiments over 98 d were also carried out to evaluate the factors affecting the N release behavior of oxamide granules in the two types of paddy soils. We found that the amidase activity was higher and, therefore, the oxamide hydrolysis rate was faster in the alluvial sandy paddy soil, which had a higher soil pH value and organic matter content, compared to the red clayey paddy soil. The faster N release and the longer growth period resulted in a mismatch between N supply by oxamide and rice demand, which, in turn, led to little improvement in NRE and a decreased grain yield in the alluvial sandy paddy soil, especially in the reduced oxamide treatment. These results could help select the appropriate size of oxamide granules for use as a slow-release N fertilizer depending on the soil properties and growth period of rice.
Cadmium (Cd) contamination is a global environmental challenge that threatens human food security. Lime combined with five different organic materials (rape seed cake, mushroom residue, straw, ...sawdust, and corn cobs) (LOM) at application ratios of 1:1 and lime sawdust combined with nitro-compound fertilizer (Ca(NO3)2·4H2O, KH2PO4, KNO3) (LSF) at different application rates were applied to Cd-contaminated soil. The present study investigates the effects of these organic–inorganic compound amendments on Cd bioavailability in soil, and Cd uptake and accumulation by edible Artemisia selengensis parts. A. selengensis was cultivated for three consecutive seasons in Cd-contaminated soil. LOM and LSF treatments obviously reduced the uptake and accumulation of Cd. Compared with the control soil, contents of Cd in edible parts of A. selengensis decreased by 19.26–33.33% and 26.67–32.78% in the first season, 18.60–32.79% and 18.37–32.79% in the second season, and 20.45–40.68% and 34.32–37.27% in the third season, respectively. The addition of Lime + Mushroom Residue and 70% Nitro-compound Fertilizer + Lime + Sawdust most significantly reduced Cd concentrations in the edible parts of the third A. selengensis season. LOM and LSF application increased soil pH and improved soil fertility, including available nitrogen, available phosphorus, available potassium, organic matter, and cation exchange capacity. Lime + Mushroom Residue improved plant yield the most. In addition, Lime + Mushroom Residue and 70% Nitro-compound Fertilizer + Lime + Sawdust had the lowest Cd accumulation and health risk indices, respectively. In conclusion, the Lime + Mushroom Residue and 70% Nitro-compound Fertilizer + Lime + Sawdust amendments significantly reduced health risks, enhanced A. selengensis growth, and promoted sustainable development of arable land under Cd-contaminated soil remediation.
The nutrient uptake and allocation of cucumber (Cucumis sativus L.) seedlings at different root-zone temperatures (RZT) and different concentrations of nitrogen (N), phosphorus (P), and potassium (K) ...nutrients were examined. Plants were grown in a nutrient solution for 30 d at two root-zone temperatures (a diurnally fluctuating ambient 10°C-RZT and a constant 20°C-RZT) with the aerial parts of the plants maintained at ambient temperature (10°C–30°C). Based on a Hoagland nutrient solution, seven N, P, and K nutrient concentrations were supplied to the plants at each RZT. Results showed that total plant and shoot dry weights under each nutrient treatment were significantly lower at low root-zone temperature (10°C-RZT) than at elevated root-zone temperature (20°C-RZT). But higher root dry weights were obtained at 10°C-RZT than those at 20°C-RZT. Total plant dry weights at both 10°C-RZT and 20°C-RZT were increased with increased solution N concentration, but showed different responses under P and K treatments. All estimated nutrient concentrations (N, P, and K) and uptake by the plant were obviously influenced by RZT. Low root temperature (10°C-RZT) caused a remarkable reduction in total N, P, and K uptake of shoots in all nutrient treatments, and more nutrients were accumulated in roots at 10°C-RZT than those at 20°C-RZT. N, P, and K uptakes and distribution ratios in shoots were both improved at elevated root-zone temperature (20°C-RZT). N supplies were favorable to P and K uptake at both 10°C-RZT and 20°C-RZT, with no significantly positive correlation between N and P, or N and K uptake. In conclusion, higher RZT was more beneficial to increase of plant biomass and mineral nutrient absorption than was increase of nutrient concentration. Among the three element nutrients, increasing N nutrient concentration in solution promoted better tolerance to low RZT in cucumber seedlings than increasing P and K. In addition, appropriately decreased P concentration favors plant growth.
The agro-pastoral transitional zone (APTZ) in northern China is a typical ecologically vulnerable zone and a comprehensive geographical transitional zone. Its land use pattern has significant type ...diversity and spatial interlocking, which is always related to the play of ecological barrier functions and the sustainability of social-ecological systems. Accurately grasping the spatial competition relationship and comprehensive geographical effects of land types of APTZ in northern China is a key proposition for achieving coordinated and sustainable development between humans and land. To explore the spatial competition mechanism and comprehensive geographical effects of land use in the research area, this study focuses on revealing the evolutionary characteristics of land use patterns based on the center of gravity migration model. Based on the process of land use center of gravity migration, the spatial competition relationship of land types is explored to reveal the evolutionary trend and basic characteristics of land use in the APTZ. The results show the following: (1) Cultivated land and meadow are the main land types of the APTZ in northern China, accounting for up to 70% of the total regional area. The spatial competition between the two land types is the main contradiction in regional land use competition. (2) Drifting of the center of gravity of cultivated land towards the northwest direction is an important land use migration feature of the APTZ in northern China. Between 1980 and 2020, the center of gravity of cultivated land shifted by about 2 km to the northwest, and the center of gravity of grassland shifted by 8–10 km to the southwest. (3) The center of gravity of arable land and grassland in the entire region is constantly approaching, which has decreased from 70.95 km in 1980 to 61.38 km in 2020. The intensification of their interweaving has led to more intense land use competition. Grasping the basic characteristics and driving mechanisms of land type competition is an important means to achieve sustainable spatial governance. (4) The scale differentiation and regional differentiation characteristics of gradient effects are significant, and it is essential to prevent the risk of mismatch between land use and natural endowments in the northeast and north China sections. The research has surpassed the traditional method of analyzing land use competition, and by introducing a centroid model to analyze the spatial mechanism of land use competition, it has expanded the methodology for expanding research in the field of land science and provided basic references for regional sustainable development.
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