Carbon footprint of synthetic nitrogen under staple crops: A first cradle-to-grave analysis.

More than half of the world's population is nourished by crops fertilized with synthetic nitrogen (N) fertilizers. However, N fertilization is a major source of anthropogenic emissions, augmenting the carbon footprint (CF). To date, no global quantification of the CF induced by N fertilization of the main grain crops has been performed, and quantifications at the national scale have neglected the CO2 assimilated by plants. A first cradle-to-grave life cycle assessment was performed to quantify the CF of the N fertilizers' production, transportation, and application to the field and the uses of the produced biomass in livestock feed and human food, as well as biofuel production. We quantified the direct and indirect inventories emitted or sequestered by N fertilization of main grain crops: wheat, maize, and rice. Grain food produced with N fertilization had a net CF of 7.4 Gt CO2eq. in 2019 after excluding the assimilated C in plant biomass, which accounted for a quarter of the total CF. The cradle (fertilizer production and transportation), gate (fertilizer application, and soil and plant systems), and grave (feed, food, biofuel, and losses) stages contributed to the CF by 2%, 11%, and 87%, respectively. Although Asia was the top grain producer, North America contributed 38% of the CF due to the greatest CF of the grave stage (2.5 Gt CO2eq.). The CF of grain crops will increase to 21.2 Gt CO2eq. in 2100, driven by the rise in N fertilization to meet the growing food demand without actions to stop the decline in N use efficiency. To meet the targets of climate change, we introduced an ambitious mitigation strategy, including the improvement of N agronomic efficiency (6% average target for the three crops) and manufacturing technology, reducing food losses, and global conversion to healthy diets, whereby the CF can be reduced to 5.6 Gt CO2eq. in 2100.

The progression of obstructive renal fibrosis in rats is regulated by ADAMTS18 gene methylation in the embryonic kidney through the AKT/Notch pathway.

This study aimed to explore the mechanism by which postembryonic renal ADAMTS18 methylation influences obstructive renal fibrosis in rats. After exposure to transforming growth factor (TGF)-ß1 during the embryonic period, analysis of postembryonic renal ADAMTS18 methylation and expression levels was conducted. Histological analysis was performed to assess embryonic kidney lesions and damage. Western blot analysis was used to determine the expression of renal fibrosis markers. Rats with ureteral obstruction and a healthy control group were selected. The methylation levels of ADAMTS18 in the different groups were analyzed. Western blot analysis and immunohistochemistry were performed to analyze the expression of renal fibrosis markers, and kidney-related indicators were measured. Treatment with TGF-ß1 resulted in abnormal development of the postembryonic kidney, which was characterized by rough kidney surfaces with mild depressions and irregularities on the outer surface. TGF-ß1 treatment significantly promoted ADAMTS18 methylation and activated the protein kinase B (AKT)/Notch pathway. Ureteral obstruction was induced to establish a renal hydronephrosis model, which led to renal fibrotic injury in newborn rats. Overexpression of the ADAMTS18 gene alleviated renal fibrosis. The western blot results showed that compared to that in the control group, the expression of renal fibrosis markers was significantly decreased after ADAMTS18 overexpression, and there was a thicker renal parenchymal tissue layer and significantly reduced p-AKT/AKT and Notch1 levels. TGF-ß1 can induce ADAMTS18 gene methylation in the postembryonic kidney, and the resulting downregulation of ADAMTS18 expression has long-term effects on kidney development, potentially leading to increased susceptibility to obstructive renal fibrosis. This mechanism may involve activation of the AKT/Notch pathway. Reversing ADAMTS18 gene methylation may reverse this process.

Biochar of invasive plants alleviated impact of acid rain on soil microbial community structure and functionality better than liming.

Acid rain and invasive plants have quintessential adverse impacts on terrestrial ecosystems. As an environmentally safe method for disposal of invasive plants, we tested the effect of biochar produced from these plants in altering soil deterioration under acid rain as compared with lime. Given the impacts of the feedstock type and soil properties on the response of soil to the added biochar, we hypothesized that the microbial community and functions would respond differently to the charred invasive plants under acid rain. A pot experiment was conducted to examine the response of soil microbiomes and functions to the biochar produced from Blackjack (Biden Pilosa), Wedelia (Wedelia trilobata), and Bitter vine (Mikania micrantha Kunth), or quicklime (CaO) at a rate of 1 % (w/w) under acid rain. Like soil pH, the nutrient contents (nitrogen, phosphorus, and potassium), calcium, and cation exchange capacity (CEC) were important as dominant edaphic factors affecting soil microbial community and functionality. In this respect, lime decreased nutrients availability, driven by 11-fold, 44 %, and 2-fold increments in calcium content, pH, and C/N ratio. Meanwhile, biochar improved nutrients availability under acid rain owing to maintaining a neutral pH (∼6.5), increasing calcium (by only 2-fold), and improving CEC, water repellency, and aggregation while decreasing the C/N ratio and aluminum content. Unlike biochar, lime decreased the relative abundance of Nitrosomonadaceae (the dominant ammonia-oxidizing bacteria) while augmenting the relative abundance of some fungal pathogens such as Spizellomycetaceae and Sporormiaceae. Given the highest nitrogen and dissolved organic carbon content than other biochar types, Wedelia-biochar resulted in the greatest relative abundance of Nitrosomonadaceae; thus, the microbial carbon and nitrogen biomasses were maximized. This study outlined the responses of the soil biogeochemical properties and the related microbial community structure and functionality to the biochar produced from invasive plants under acid rain. This study suggests that biochar can replace lime to ameliorate the effects of acid rain on soil physical, chemical and biological properties.

Influence of nitrogen substitution at an equivalent total nitrogen level on bacterial and fungal communities, as well as enzyme activities of the ditch bottom soil in a rice-fish coculture system.

BACKGROUND: Rice-fish coculture system (RFS) operates through effectively utilizing water and land resources in a complementary form, but it requires more efficient utilization of fertilizer and feed without compromising rice yield. However, the knowledge of how to regulate the proportion of nitrogen (N) supplied from fertilizer and feed at an equivalent total N level to improve the benefits of RFS remains limited. Therefore, four treatments (S0: RFS with 0% N from fertilizer and 100% N from feed; S25: RFS with 25% N from fertilizer and 75% N from feed; S50: RFS with 50% N from fertilizer and 50% N from feed; S75: RFS with 75% N from fertilizer and 25% N from feed) were conducted to assess the variation of ditch bottom soil properties, microbial communities and enzyme activities, as well as to obtain the optimal ratio of N supplied from fish feed and fertilizer. RESULTS: The experiments showed that the contents of soil organic matter, total carbon and total N, and the activities of urease, N-acetyl-ß-D-glucosaminidase, protease, ß-1,4-glucosidase and catalase in the ditch bottom soil significantly reduced in S25 treatment, compared with the other three treatments. Ammonium N content decreased with increasing percentage of the basal fertilizer, whereas nitrate N content and pH value showed an adverse trend. However, the bacterial and fungal communities were unaffected by the ratio shifts between fertilizer-N and feed-N, but their dominant phyla were influenced by the ditch bottom soil N level. Moreover, the bacterial community composition was positively related to nitrate N, whereas fungal diversity was positively correlated with pH, ammonium N and nitrate N, and urease. We also found that the treatment of N input with 25% N from fertilizer and 75% N from feed can reduce N deposition in the ditch bottom soil in the rice-fish coculture system. CONCLUSION: Our findings indicate that under the equivalent total N input level, the relative higher ratio of N from fish feed increased (S0 treatment) or reduced (S25 treatment) the deposition of N in the ditch bottom soil, and improved fish production, but decreased rice yield; while the higher ratio of N from basal fertilizer increased the transportation of nutrients into the ditch bottom soil and rice yield, but reduced fish production. So when considering multi-balance and multiple benefits, we recommend that a selective substitution ratio within 50% ~ 75% from fish feed to substitute for the basal fertilizer under the equivalent total N input may achieve a good balance of rice and fish production improvement, and reduce nutrients wastage to the ditch bottom, as well as alleviate the potential of non-point source pollution. This study also provides an evidence for regulating and optimizing the ratio of N supplied from fertilizer and fish feed at an equivalent total N level through monitoring the nutrient accumulation in ditch bottom soil in the rice-fish coculture system. © 2024 Society of Chemical Industry.

Mixed cropping with duck co-culture: an agroecological system to improve grain quality and farm profitability.

BACKGROUND: Previous studies found that mixed cropping combined with duck co-culture (MCDC) system could improve the efficiency of grain production and positively affect soil nutrient contents. However, the effects on grain quality, and profitable income have not been evaluated yet. In this study, a field experiment with four combinations of different rice varieties and ducks was conducted during both the early and late rice growing seasons. RESULTS: The field survey demonstrated that MCDC system significantly decreased the grain appearance of chalky rice rate and the chalkiness degree with an average of 56.82%, and 54.28%, respectively. Leaf SPAD value, photosynthetic rate, and aboveground dry weight were all improved in the MCDC and mixed-cropping systems, relative to the mono-cropping system. The net income obtained from the mono-cropping, mixed cropping (no ducks), and MCDC (with ducks) systems (from grain and ducks' meat) was 581.2 USD ha-1 yr-1 , 1001.8 USD ha-1 yr-1 , and 5242.1 USD ha-1 yr-1 in both growing seasons, respectively. CONCLUSION: Planting genetically diverse rice varieties and co-culture with ducks increased rice growth rates, productivity and grain quality. The MCDC system would provide more ecological and economic benefits compared with the conventional mono-cropping system. © 2022 Society of Chemical Industry.

Suitable stocking density of fish in paddy field contributes positively to 2-acetyl-1-pyrroline synthesis in grain and improves rice quality.

BACKGROUND: Fragrant rice is increasingly popular with the public owing to its fresh aroma, and 2-acetyl-1-pyrroline (2-AP) is the main characteristic component of the aroma in fragrant rice. Rice-fish co-culture is an environmentally friendly practice in sustainable agriculture. However, the effect of rice-fish co-culture on 2-AP in grains has received little study. A conventional fragrant rice (Meixiangzhan 2) was used, and a related field experiment during three rice growing seasons was conducted to investigate the effects of rice-fish co-culture on 2-AP, as well as the rice quality, yield, plant nutrients, and precursors and enzyme activities of 2-AP biosynthesis in leaves. This study involved three fish stocking density treatments (i.e. 9000 (D1), 15 000 (D2), and 21 000 (D3) fish fries per hectare) and rice monocropping. RESULTS: Rice-fish co-culture increased the 2-AP content in grains by 2.5-49.4% over that of the monocropping, with significant increases in the early and late rice seasons of 2020. Rice-fish co-culture treatments significantly promoted seed-setting rates by 3.39-7.65%, and improved leaf nutrients and rice quality. Notably, the D2 treatment significantly increased leaf total nitrogen (TN), total phosphorus (TP), and total potassium (TK) contents and the head rice rate at maturity stage, while significantly decreased chalkiness degree. There was no significant difference in rice yield. CONCLUSION: Rice-fish co-culture had positive effects on 2-AP synthesis, rice quality, seed-setting rates, and plant nutrient contents. The better stocking density of field fish for rice-fish co-culture in this study was 15 000 fish ha-1 . © 2023 Society of Chemical Industry.

Meta-analysis reveals differential impacts of microplastics on soil biota.

Contamination of microplastics (MPs) is a global environmental issue that has received much attention from the scientific and public communities due to ecological concerns in recent decades. Comparing with aquatic ecosystems, soil systems, regardless of the high importance and complexity, have been less studied under widely existing and increasing MP contamination. This review, combined with data assimilation and meta-analysis methods, has summarized current contamination conditions of soil MPs across different sites reported in earlier studies. While performing this meta-analysis, we investigated the effects of MPs on soil biota including their numbers, biomass, diversity, and physiological properties. The results showed that abundance of soil MPs ranged from 0.34 to 410958.9 items kg-1 and concentration ranged from 0.002 to 67500 mg kg-1 across sites, with agricultural soils containing significantly lower abundance and concentration of MPs than others. Presence of MPs significantly decreased the individual number of soil biota, operational taxonomic unit, diversity index (Simpson), movement index and reproduction rate, whereas the mortality rate was significantly increased by the soil MPs. Despite these significant effects, MPs did not significantly alter the biomass of soil biota, which could be due to a counteraction of their negative and positive effects on different groups of soil organisms. Moreover, we observed that soil MPs could significantly increase the Chao1 index, suggesting that MPs may act as a food resource for the soil rare biosphere. Based on the existing knowledge, we suggest that future studies should focus on research areas that include but are not limited to methodological improvements, intensive field investigations, risk assessment from the perspective of soil food web and bioaccumulation, MPs induced antibiotic resistance, and restoration strategies to reduce their concentrations in soil.

Increasing acid rain frequency promotes the microbial community dissimilarities of forest soil rather than agricultural soil in southern China.

Soil microbial community drives the terrestrial carbon (C) cycling by C sources metabolism (i.e., organic C decomposition), however, the microbial response to changing acid rain frequency remains less studied, thus hampering global warming projection. Here, we manipulated a simulated experiment to decipher the impact of acid rain frequency (0, 30%, and 100%) on microbial community and C sources metabolism in the agricultural and forest soils of southern China, based on the phospholipid fatty acids (PLFAs) analysis and BIOLOG method, respectively. We found that changing acid rain frequency did not affect the microbial biomass and community structure of agricultural soil during the whole experiment period, while the 30% and 100% acid rain frequencies significantly decreased the microbial biomass, and altered the microbial community structure of forest soil at the early stage. However, changing acid rain frequency did not influence the microbial C sources metabolism in the agricultural soil, but 30% acid rain frequency significantly reduced the microbial utilization of carboxylic acids in the forest soil. Moreover, increasing acid rain frequency promoted the microbial community dissimilarities of forest soil. The microbial community structure and C sources utilization of agricultural soil were significantly related to soil available phosphorus content, while that of forest soil correlated with the soil available potassium content and temperature. Changes in soil environmental condition, soil acidification parameters and soil nutrients explained most of the variance of microbial community and C sources utilization (81% and 57%, respectively) in the forest soil, whereas great uncertainties of microbial community and C sources utilization existed in the agricultural soil with the explanatory proportion being 20% and 10%, respectively. Our findings suggest that the microbial community of forest soil is more sensitive to changing acid rain frequency than that of agricultural soil in a short term. These results support the prediction of microbes-driven C cycling dynamics in specific soil ecosystems in the context of changing acid rain frequency.

Physiological response and oxidative stress of grass carp (Ctenopharyngodon idellus) under single and combined toxicity of polystyrene microplastics and cadmium.

The harm of microplastics (MPs) to aquatic ecosystems is caused by their stable and non-degradable properties. Additionally, the pollutants such as heavy metals in the water are easy to be adsorbed on their surface with their small particle size and large specific surface area, resulting in environmental pollution. Therefore, the study on the mixture toxicity of MPs and heavy metals has theoretical significance for the risk assessment of aquatic ecosystems. In the present study, 10 nm polystyrene (PS) and cadmium (Cd) were used, and their individual and mixture acute toxicities on grass carp (Ctenopharyngodon idellus) were examined. The results indicated that the mortality of the fish increased with the concentration from 10 mg L-1 to 20 mg L-1, and the existence of PS-MPs elevated the Cd concentrations in the fish and accelerated the death. Whether the Cd and/or the PS-MPs concentrations caused varying degrees of damage to the gills, kidney, liver, and muscles of the grass carp, especially under the highest concentrations (20 mg L-1 Cd + 300 µg L-1 PS-MPs). Moreover, low concentrations of PS-MPs alone (30 µg L-1 PS-MPs) significantly increased the superoxide dismutase (SOD) activity in the kidney and liver, reaching 12.43% and 14.38%, respectively (P < 0.05). The peroxidase (POD) activity was increased only in the kidney, up to 25.95% (P < 0.05). Also, significant reductions in SOD and POD activities were observed in the combination of high concentration of Cd (20 mg L-1) and 300 µg L-1 PS-MPs (P < 0.05). To the best of our knowledge, there are few studies on the impact of combined toxicity of PS-MPs and Cd on grass carp under laboratory conditions. Therefore, these findings may provide a theoretical guarantee for pollution prevention and control in the aquatic ecosystem.

Maintaining higher grain production with less reactive nitrogen losses in China: A meta-analysis study.

Managing reactive nitrogen (Nr) in agricultural production is crucial for addressing the triple challenges of food security, climate change and environmental degradation. Intensive work has been conducted to investigate the effects of mitigation strategies on reducing Nr losses by ammonia emission (Nr-NH3), nitrous oxide emission (Nr-N2O) and nitrate leaching (Nr-NO3-) separately. This meta-analysis evaluated the efficiency of each strategy in mitigating Nr losses coupled with grain yield responses. The results indicate that producing one Megagram (Mg) of wheat grains caused higher Nr losses, twice that of rice and 17% that of maize. The Nr-NH3 and Nr-NO3- were the dominant sources of Nr losses of the three crops (96%), while Nr-NH3 only presented 86% of the total Nr losses for rice. Reducing the N rate strategy decreased the yield by 33% and the Nr losses by 62% compared with the conventional rate (150-250 kg N ha-1) as an average of the three crops. In contrast, increasing the N rate higher than 250 kg N ha-1 amplified the yield by 15% but also caused a 71% increase in Nr losses compared with the conventional rate. Although subsurface application decreased Nr losses by 5%, this study rejected this approach as an effective strategy due to a 4% yield decline on average of the grain crops. Slow-release fertilizers decreased Nr-NH3 and Nr-N2O losses by 41-58% and 54-89%, respectively, of the highest losses under urea in the three crops, but also led to yield reductions. Organic amendments achieved the highest drop in Nr-NO3- loss by 66% in maize coupled with yield declines. Biochar increased wheat and maize yields by 0.3 and 0.1 Mg, respectively, coupled with 1 kg reduction in Nr losses. On average, inhibitors augmented the grain yields by 0.2 Mg ha-1 for each 1 kg decline in Nr losses. In conclusion, for sustainable agricultural intensification, biochar (for wheat only) and inhibitors (for the three crops) are strongly recommended as mitigation strategies for Nr losses from grain crop production systems in China.

Water mimosa (Neptunia oleracea Lour.) can fix and transfer nitrogen to rice in their intercropping system.

BACKGROUND: Cereal-legume intercropping systems are an environmentally friendly practice in sustainable agriculture. However, research on the interspecific interaction of nitrogen (N) between rice and aquatic legumes has rarely been undertaken. To address this issue, a pot experiment was conducted to investigate N utilization and the N interaction between rice and water mimosa (Neptunia oleracea Lour.) in an intercropping system. The root barrier patterns consisted of solid barrier (SB), mesh barrier (MB), and no barrier (NB) treatments. The N fertilizer application rates were low, medium, and high N rates. RESULTS: The results showed that the NB treatment better facilitated rice growth compared with the MB and SB treatments. And the nitrate N content and urease activity of rice rhizospheric soil in the NB treatment were the highest of the three separated patterns. The ammonium N content in water mimosa rhizospheric soil and N2 fixation of water mimosa ranked as NB > MB > SB. CONCLUSIONS: The amount of N fixation by water mimosa was 4.38-13.64 mg/pot, and the N transfer from water mimosa to rice was 3.97-9.54 mg/pot. This can promote the growth of rice and reduce the application of N fertilizer. We suggest that the rice-water mimosa intercropping system is a sustainable ecological farming approach and can be applied in the field to facilitate rice production. © 2021 Society of Chemical Industry.

Mix-cropping of rice and water mimosa (Neptunia oleracea Lour.) increases rice photosynthetic efficiency, yield, grain quality and soil available nutrients.

BACKGROUND: Cereal cultivation with legumes plays an important role in improving biodiversity and productivity. However, there are limited references concerning rice/legume mix-cropping in paddy fields. An aquatic leguminous plant, water mimosa (Neptunia oleracea Lour.), was introduced and a related field experiment of two seasons (early and late seasons in 2019) was carried out to explore the effects of rice/water mimosa mix-cropping on rice growth, yield, grain quality and soil nutrients in the present study. Three treatments - rice monocropping, rice/water mimosa intercropping and mix-cropping - were employed in this study. RESULTS: Results showed that rice grew better with greater height, tiller number, chlorophyll content, actual photosynthetic efficiency [Y(II)], maximum photochemical efficiency (Fv /Fm ) and photochemical quenching coefficient (qP) in the intercropping and mix-cropping treatments. In addition, the intercropping and mix-cropping treatments increased nutrient uptake of nitrogen (N) by11.89-24.42%, phosphorous (P) by 17.75-36.61% and potassium (K) by 19.22-47.44%, and rice yield by 19.9% and 21.8%. Conversely, the non-photochemical quenching coefficient (NPQ), chalkiness degree and chalky rate of rice were lower in the intercropping and mix-cropping treatments relative to those in the monocropping treatments. Notably, soil alkali-hydrolysable N (AN), available P (AP) and K (AK) contents were the highest in the mix-cropping treatments among the three cropping systems. CONCLUSION: We suggest that rice/water mimosa mix-cropping is an environmentally friendly agroecological system with a higher output and can be extended for green rice production and largely applied in the paddy field. © 2021 Society of Chemical Industry.

Preservation of the genetic diversity of a local common carp in the agricultural heritage rice-fish system.

We examined how traditional farmers preserve the genetic diversity of a local common carp (Cyprinus carpio), which is locally referred to as "paddy field carp" (PF-carp), in a "globally important agricultural heritage system" (GIAHS), i.e., the 1,200-y-old rice-fish coculture system in Zhejiang Province, China. Our molecular and morphological analysis showed that the PF-carp has changed into a distinct local population with higher genetic diversity and diverse color types. Within this GIAHS region, PF-carps exist as a continuous metapopulation, although three genetic groups could be identified by microsatellite markers. Thousands of small farmer households interdependently obtained fry and parental carps for their own rice-fish production, resulting in a high gene flow and large numbers of parent carps distributing in a mosaic pattern in the region. Landscape genetic analysis indicated that farmers' connectivity was one of the major factors that shaped this genetic pattern. Population viability analysis further revealed that the numbers of these interconnected small farmer households and their connection intensity affect the carps' inherent genetic diversity. The practice of mixed culturing of carps with diverse color types helped to preserve a wide range of genetic resources in the paddy field. This widespread traditional practice increases fish yield and resource use, which, in return, encourages famers to continue their practice of selecting and conserving diverse color types of PF-carp. Our results suggested that traditional farmers secure the genetic diversity of PF-carp and its viability over generations in this region through interdependently incubating and mixed-culturing practices within the rice-fish system.

Seasonality regulates the effects of acid rain on microbial community in a subtropical agricultural soil of Southern China.

Acid rain alters soil carbon (C) cycling by influencing the soil microbial community structure and functions. However, the response of soil microbial communities to acid rain with time and underlying mechanisms are still poorly understood. Herein, we conducted a one-year intact soil core experiment to investigate the temporal changes of soil microbial community composition and C sources metabolism under acid rain (pH 5.0, pH 4.0, and pH 3.0) in an agricultural soil of southern China. We found that pH 3.0 acid rain increased the total, bacterial, gram-positive bacterial, and actinomycetal PLFAs at the early stage, but this effect diminished with time. Conversely, the gram-negative bacterial PLFAs contents were reduced under pH 3.0 acid rain at the later stage. Interestingly, pH 5.0 acid rain increased the total, bacterial, gram-positive bacterial, and actinomycetal PLFAs contents at the later stage. In addition, pH 3.0 and pH 5.0 acid rain treatments accordingly altered the soil microbial community structure at the early and later stage. However, acid rain did not change the microbial C sources utilization pattern. The principal response curve analysis revealed that the seasonal variation exerted a greater effect on the overall variance of soil microbial community structure than the acidity of acid rain. Our results demonstrate the asynchronous response of soil microbial community structure and function, which implies that the microbial functional redundancy may exist in the subtropical agricultural soil under acid rain.

Effects of acid rain on plant growth: A meta-analysis.

Anthropogenic driven acid gases emission has caused acid rain in many regions globally. Although efforts have been made to assess the effects of acid rain on terrestrial ecosystems, a systematic assessment of growth-related traits across plant aboveground and belowground is lacking. Hence, we performed a phylogenetically controlled meta-analysis of 755 observations from 69 independent studies to quantify the effects of acid rain on six growth-related traits of plant. We estimated the inhibitory effects of acid rain on plant growth in general and found that aboveground and belowground plant parts responded differently. The acidity of acid rain and acid rain interval had direct modulation effects on plant growth. We also found that there were interactions between acid rain pH and other acid rain characteristics (i.e., acid rain interval, mole ratio of S:N, and acid rain rate) and experimental characteristics (i.e., initial soil pH and plant exposure part), indicating that there were pH-dependent interaction patterns. Thus, an effective approach to evaluate and predict the effects of acid rain on plant growth is to fully consider the direct effects of acid rain pH and the interactions between acid rain pH and other factors.

Characterization and utilization of biochars derived from five invasive plant species Bidens pilosa L., Praxelis clematidea, Ipomoea cairica, Mikania micrantha and Lantana camara L. for Cd2+ and Cu2+ removal.

Exotic invasive plants endanger the integrity of agricultural and natural systems throughout the world. Thus, the development of cost-effective and economic application of invasive plants is warranted. Here, we characterized fifteen biochars derived from five invasive plants at different temperatures (300, 500, and 700 °C) by determining their yield, ash content, pH, CEC, surface area, elementary composition, functional groups, and mineral composition. We conducted batch adsorption experiments to investigate the adsorption capacity and efficiency for Cd2+ and Cu2+ in wastewater. Our results suggest that all invasive plants are appropriate for biochar production, temperature and plant species had interacting effects on biochar properties, and the biochars pyrolyzed at 500 and 700 °C exhibited high metal adsorption capacity in neutral (pH = 7) solutions. The adsorption kinetics can be explained adequately by a pseudo-second-order model. BBC500 (Bidens pilosa L. derived biochar at 500 °C) and MBC500 (Mikania micrantha) exhibited higher metal equilibrium adsorption capacities (38.10 and 38.02 mg g-1 for Cd2+, 20.01 and 20.10 mg g-1 for Cu2+) and buffer abilities to pH than other biochars pyrolyzed at 500 °C. The Langmuir model was a better fit for IBC500 (Ipomoea cairica), MBC500, and LBC500 (Lantana camara L.) compared to the Freundlich model, whereas the opposite was true for BBC500 and PBC500 (Praxelis clematidea). These results suggest that the adsorption of metals by IBC500, MBC500, and LBC500 was mainly monolayer adsorption, while that by BBC500 and PBC500 was mainly chemical adsorption. Our results are important for the utilization and control of invasive plants as well as the decontamination of aqueous pollution.

Reduced pests, improved grain quality and greater total income: benefits of intercropping rice with Pontederia cordata.

BACKGROUND: Intercropping, which is growing two or more different crops in the same field simultaneously, is an effective traditional agricultural practice for productivity, resource utilization, and pest control. However, study on intercropping in paddy fields is limited. So in this study, field experiments of 2 years/four seasons (early and late seasons in 2016 and 2017) were conducted to examine the effects of rice-Pontederia cordata intercropping on rice plant growth, pest control, yield, income, and grain quality. RESULTS: We found rice-P. cordata intercropping significantly decreased the occurrence of rice diseases and pests, with a 22.0-45.9% reduction in sheath blight and a 33.8-34.4% reduction in leaf folders. The mean land equivalent ratio (LER) (1.09) result indicates that intercropping rice and P. cordata generated positive yield effects. In addition, due to the economic profit from the replacement stripe of P. cordata in the rice paddy field, intercropping rice with P. cordata could greatly enhance farmer income. The average total income of rice intercropped with P. cordata was 2.5-fold higher than that of rice monoculture. Furthermore, intercropping significantly improved grain quality compared with the rice monoculture. It significantly increased the milled rice rate and whole milled rice rate by 11.2% and 12.8%, respectively, but decreased the chalky rice rate by 30.9-39.8% and chalkiness degree by 32.2%. CONCLUSIONS: We suggest that rice-P. cordata intercropping provides an environmentally effective way to control rice diseases and pests, results in higher overall productivity and total income, and improves grain quality. © 2021 Society of Chemical Industry.

Effects of the integration of mixed-cropping and rice-duck co-culture on rice yield and soil nutrients in southern China.

BACKGROUND: Biodiversity-based agricultural systems can improve production efficiency and sustainability, with fewer negative environmental impacts and lower use of external inputs. Mixed-cropping and rice-duck co-culture have been shown to produce ecological benefits and to have positive effects on paddy soil. However, the effects of a combination of mixed cropping with different rice cultivars and duck co-culture on soil nutrients availability and grain yields have not been evaluated. A paddy field experiment was carried out over two rice growing seasons to test these effects. RESULTS: Several combinations of rice cultivars, when integrated with duck co-culture, significantly increased the soil organic matter and total nitrogen contents during the rice growing seasons, as compared to mono-cropping systems. In mixed-cropping combined with duck co-culture (MCDC) systems, the soil alkali-hydrolyzable nitrogen content ranged from 4.33% to 17.86% higher than that in mono-cropping systems. Similar increases were found for soil available phosphorus (8.71-15.91%) and soil available potassium (8.65-39.43%) contents. Furthermore, MCDC produced higher grain yields and harvest indexes for both study seasons. CONCLUSION: The integration of MCDC systems had positive effects on soil nutrient contents of paddy fields, which could, in turn, lead to yield enhancements, as well as additional income for farmers in the form of organic duck meat. © 2019 Society of Chemical Industry.

Tobacco Cutworm (Spodoptera Litura) Larvae Silenced in the NADPH-Cytochrome P450 Reductase Gene Show Increased Susceptibility to Phoxim.

Nicotinamide adenine dinucleotide phosphate (NADPH)-cytochrome P450 reductases (CPRs) function as redox partners of cytochrome P450 monooxygenases (P450s). CPRs and P450s in insects have been found to participate in insecticide resistance. However, the CPR of the moth Spodoptera litura has not been well characterized yet. Based on previously obtained transcriptome information, a full-length CPR cDNA of S. litura (SlCPR) was PCR-cloned. The deduced amino acid sequence contains domains and residues predicted to be essential for CPR function. Phylogenetic analysis with insect CPR amino acid sequences showed that SlCPR is closely related to CPRs of Lepidoptera. Quantitative reverse transcriptase PCR (RT-qPCR) was used to determine expression levels of SlCPR in different developmental stages and tissues of S. litura. SlCPR expression was strongest at the sixth-instar larvae stage and fifth-instar larvae showed highest expression in the midgut. Expression of SlCPR in the midgut and fat body was strongly upregulated when fifth-instar larvae were exposed to phoxim at LC15 (4 µg/mL) and LC50 (20 µg/mL) doses. RNA interference (RNAi) mediated silencing of SlCPR increased larval mortality by 34.6% (LC15 dose) and 53.5% (LC50 dose). Our results provide key information on the SlCPR gene and indicate that SlCPR expression levels in S. litura larvae influence their susceptibility to phoxim and possibly other insecticides.

Mixed-cropping systems of different rice cultivars have grain yield and quality advantages over mono-cropping systems.

BACKGROUND: A mixed-cropping system that enhances farmland biodiversity has the potential to improve grain yield and quality; however, the impacts of growing different rice cultivars simultaneously has been rarely investigated. In the present study, five popular rice cultivars were selected and ten mixture combinations were made according to the growth period, plant height, grain yield and quality, and pest and disease resistance. Seedlings of the five cultivars and ten mixture combinations (mixed-sowing of the seeds in an equal ratio, then mixed-transplanting and finally mixed-harvesting) were grown in plastic pots in a glasshouse during the early and late growing seasons in 2016. RESULTS: Compared with the mono-cropping systems in the early and late growing seasons in 2016 (paired t-test), the mixed-cropping systems increased the rice leaf photosynthetic rate, soil plant analysis development (SPAD) index and total aboveground dry weight. Moreover, mixed-cropping systems improved the number of spikelets per panicle, seed-setting rate, and grain weight per pot and harvest index by 19.52% and 5.77%, 8.53% and 4.41%, 8.31% and 4.61%, and 10.26% and 6.98% in the early and late growing seasons, respectively. In addition, mixed-cropping systems reduced chalky rice rate and chalkiness degree by 33.12% and 43.42% and by 30.11% and 48.13% in the early and late growing seasons, respectively. CONCLUSION: The SPAD indexes and photosynthetic rates enhanced at physiology maturity in mixed-cropping systems may result in higher grain yield and better grain quality. In general, it was found that mixed-cropping with different rice cultivars has the potential for increasing grain yield and improving grain quality. © 2018 Society of Chemical Industry.