The effect of pH increases following lime (Ca(OH) 2 ) addition on soil cadmium (Cd) availability is examined in three soils. The effect of Ca(OH) 2 addition (0–7.5 t ha −1 ) on crop Cd uptake and microbial community composition is evaluated in pot experiments with Chinese cabbage ( Brassica chinensis L.) and rice ( Oryza sativa L.). The soil pH increases significantly (by 1.21–2.57) after Ca(OH) 2 addition, which may be caused by both biological and chemical factors. The soil water‐exchangeable Cd content decreases substantially from 11.7 to 1.4% with Ca(OH) 2 application, and the iron and manganese oxide Cd fractions increase from 24.7 to 37.5%. Ca(OH) 2 significantly reduces the exchangeable Cd in acidic soil but has limited effects in neutral soil. Ca(OH) 2 can inhibit soil Cd activity and plant Cd absorption in acid soil. With increasing Ca(OH) 2 addition, the abundance of microorganisms tends to decrease, especially in the acidic soil, whereas it tends to increase in neutral soil. Principal components analysis and redundancy analysis among the soil environmental factors and the soil microbial phospholipid fatty acids show highly variable microbial community composition among soils and treatments. Soil pH has substantial effects on soil fungi, actinomycetes, and other microorganisms, the abundance of which decreases with increasing soil pH. The continuous use of Ca(OH) 2 has no significant effects on the abundance and distribution of soil microorganisms.
Abstract. Conservation tillage has attracted increasing attention over recent decades, mainly due to its benefits for improving soil organic matter content and reducing soil erosion. However, the effects of long-term straw mulching under a no-till system on soil physicochemical properties and bacterial communities at different soil depths are still unclear. In this 12-year experiment of straw removal (CK) and straw mulching (SM) treatments, soil samples were collected at 0â5, 5â10, 10â20, and 20â30âcm soil depths. The results showed that the contents of organic carbon (C), nitrogen (N), and phosphorus (P) fractions, and bacterial abundance significantly decreased, whereas pH significantly increased with soil depth. Compared with CK, SM significantly increased total N, inorganic N, available P, available potassium, and soil water content at 0â5âcm, total organic C content at 0â10âcm, and dissolved organic C and N contents at 0â20âcm. Regarding bacterial communities, SM increased the relative abundances of Proteobacteria, Bacteroidetes, and Acidobacteria but reduced those of Actinobacteria, Chloroflexi, and Cyanobacteria. Bacterial Shannon diversity and Shannon's evenness at 0â5âcm were reduced by SM treatment compared to CK treatment. Furthermore, SM increased the relative abundances of some C-cycling genera (such as Terracidiphilus and Acidibacter) and N-cycling genera (such as Rhodanobacter, Rhizomicrobium, Dokdonella, Reyranella, and Luteimonas) at 0â5âcm. Principal coordinate analysis showed that the largest difference in the composition of soil bacterial communities between CK and SM occurred at 0â5âcm. Soil pH and N and organic C fractions were the major drivers shaping soil bacterial communities. Overall, SM treatment is highly recommended under a no-till system because of its benefits to soil fertility and bacterial abundance.
Introduction The rapid global population growth and limitations of traditional agricultural practices have resulted in inadequate nutrient supply. Nano-agricultural technology presents significant potential for enhancing crop growth and resistance, reducing stresses, and providing economic benefits with lower environmental risks. Methods In this study, a bibliometric analysis of nano-agricultural applications was conducted using the Web of Science Core Collection, and 2,626 publications from 2000 to 2023 were identified, with an exponential increase in both publications and citations. Results and discussion European and Asian countries and institutions are more actively involved, although USA produces the highest-quality papers. Additionally, this field has evolved through two stages: the first stage (2000-2016) focused on the toxicology of nanomaterials (NMs), while the second stage (2017-present) emphasizes NMs as nanofertilizers to promote crop growth, and as nanoregulators or nanopesticides to enhance crop resistance against biotic stress and abiotic stress. Finally, future research perspectives were also proposed, including the optimalizations of NMs, the investigations of the behavior and bioavailability of NMs driven by rhizosphere and phyllosphere process, interdisciplinary collaboration across various fields, the application of NMs from laboratory to the field, and the long-term environmental behaviors and assessments of NMs in diverse ecosystems. Overall, this bibliometric study provides a valuable reference for understanding the development of this field and pinpointing research frontiers.
With growing concerns about global warming, it is crucial to adopt agronomic practices that enhance rice yields from paddy fields while reducing greenhouse gas (GHG) emissions for sustainable agriculture. An optimal nitrogen (N) fertilization rate and planting density are vital to ensure high rice yields, minimize GHG emissions, and understand emission behavior for better field management. We hypothesized that optimizing N application rates and planting density to improve nitrogen use efficiency (NUE) in rice cultivation would reduce resource losses and GHG emissions. To test this hypothesis, we implemented five treatments with a rice straw return cultural system: two planting densities (16 hills m−2 (traditional density, D1) and 20 hills m−2 (25% higher density, D2)) and three N application rates (no N fertilizer (N0), 180 kg N ha−1 (N1), and 144 kg N ha−1 (N2)). The control treatment (CK) was traditional planting density with no N fertilizer. The four new cropping modes were N1D1, N1D2, N2D1, and N2D2. We investigated the effects of N application rates and planting density on rice grain yield, NUE, and GHG emissions in multiple rice-growing seasons. The N1D2 treatment exhibited the highest grain yield over the three years, with a value of 10,452 kg ha−1, representing an increase of 12.2% compared to CK. Moreover, N uptake in N1D2 was the highest, averaging 39.2% (p < 0.05) higher than CK, and 8.5%, 3.5%, and 2.8% (p < 0.05) higher than N1D1, N2D1 and N2D2, respectively. N2D2 exhibited the highest NUE, with a value of 58.99 kg kg−1, surpassing all other treatments over the three years. GHG emissions, global warming potential (GWP), and greenhouse gas intensity (GHGI) in N2D2 were lower than in N1D1, N1D2, and N2D1. Additionally, reducing N application (comparing N1D1 to N2D1) and increasing plant density (comparing N1D1 to N1D2) improved N agronomic efficiency (NAE) and N partial productivity (PFPN). The negative correlation between the NAE and PFPN with GWP and GHG emissions further supports the potential for optimized N management and denser planting density to reduce environmental impact. These findings have important implications for sustainable rice cultivation practices in Southwest China and similar agroecosystems, emphasizing the need for integrated nutrient management strategies to achieve food security and climate change mitigation goals.
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