Impacts of Fertilization Optimization on Soil Nitrogen Cycling and Wheat Nitrogen Utilization Under Water-Saving Irrigation

Liquid fertilizers produced by microwave-assisted acid hydrolysis of livestock and poultry wastes and their effects on hot pepper cultivation

Liquid fertilizers (LFs) produced by microwave-assisted acid hydrolysis of livestock and poultry wastes were applied to potted hot pepper (Capsicum annuum L.) to evaluate their potential to be used as amino acid LFs. A preliminary experiment was conducted to determine the optimum acid-hydrolysis conditions for producing LFs from a mixture of pig hair and faeces (P) and another mixture of chicken feathers and faeces (C). Two LFs were produced under the optimum acid-hydrolysis conditions (acidification by sulphuric acid (7.5 mol L-1) in a microwave (200 W) for 90 minutes), and a commercial amino acid LF (Guo Guang (GG)) was used for comparison. P, C and GG fertilizers were tested in potted hot pepper cultivation at two doses, whereas no fertilizer application served as the control (CK). P and C fertilizers significantly increased the fruit yield compared with GG fertilizer, particularly at the higher dose. Moreover, the treatments improved the fruit vitamin C and soluble sugar contents in the order of C > P > GG compared with CK. These results could be attributed to more types of amino acids in C fertilizer than in P and GG fertilizers. The results also indicated that the prepared fertilizers could significantly increase the shoot and root dry weight, soil available nitrogen and phosphorus contents and nitrogen, phosphorus, and potassium (NPK) uptake by plants compared with CK. In conclusion, microwave-assisted acid hydrolysis could effectively convert unusable wastes into valuable fertilizers comparable or even superior to commercial fertilizers.

TaCDPK1-5A positively regulates drought response through modulating osmotic stress responsive-associated processes in wheat (Triticum aestivum)

KEY MESSAGE

Wheat TaCDPK1-5A plays critical roles in mediating drought tolerance through regulating osmotic stress-associated physiological processes. Calcium (Ca2+) acts as an essential second messenger in plant signaling pathways and impacts plant abiotic stress responses. This study reported the function of TaCDPK1-5A, a calcium-dependent protein kinase (CDPK) gene in T. aestivum, in mediating drought tolerance. TaCDPK1-5A sensitively responded to drought and exogenous abscisic acid (ABA) signaling, displaying induced transcripts in plants under drought and ABA treatments. Yeast two-hybrid and co-immunoprecipitation assays revealed that TaCDPK1-5A interacts with the mitogen-activated protein kinase TaMAPK4-7D whereas the latter with ABF transcription factor TaABF1-3A, suggesting that TaCDPK1-5A constitutes a signaling module with above partners to transduce signals initiated by drought/ABA stressors. Overexpression of TaCDPK1-5A, TaMAPK4-7D and TaABF1-3A enhanced plant drought adaptation by modulating the osmotic stress-related physiological indices, including increased osmolyte contents, enlarged root morphology, and promoted stomata closure. Yeast one-hybrid assays indicated the binding ability of TaABF1-3A with promoters of TaP5CS1-1B, TaPIN3-5A, and TaSLAC1-3-2A, the genes encoding P5CS enzyme, PIN-FORMED protein, and slow anion channel, respectively. ChIP-PCR and transcriptional activation assays confirmed that TaABF1-3A regulates these genes at transcriptional level. Moreover, transgene analysis indicated that these stress-responsive genes positively regulated proline biosynthesis (TaP5CS1-1B), root morphology (TaPIN3-5A), and stomata closing (TaSLAC1-3-2A) upon drought signaling. Positive correlations were observed between yield and the transcripts of TaCDPK1-5A signaling partners in wheat cultivars under drought condition, with haplotype TaCDPK1-5A-Hap1 contributing to improved drought tolerance. Our study concluded that TaCDPK1-5A positively regulates drought adaptation and is a valuable target for molecular breeding the drought-tolerant cultivars in T. aestivum.

Regulating Leaf Photosynthesis and Soil Microorganisms through Controlled-Release Nitrogen Fertilizer Can Effectively Alleviate the Stress of Elevated Ambient Ozone on Winter Wheat

The mitigation mechanisms of a kind of controlled-release nitrogen fertilizer (sulfur-coated controlled-release nitrogen fertilizer, SCNF) in response to O3 stress on a winter wheat (Triticum aestivum L.) variety (Nongmai-88) were studied in crop physiology and soil biology through the ozone-free-air controlled enrichment (O3-FACE) simulation platform and soil microbial metagenomics. The results showed that SCNF could not delay the O3-induced leaf senescence of winter wheat but could enhance the leaf size and photosynthetic function of flag leaves, increase the accumulation of nutrient elements, and lay the foundation for yield by regulating the release rate of nitrogen (N). By regulating the soil environment, SCNF could maintain the diversity and stability of soil bacterial and archaeal communities, but there was no obvious interaction with the soil fungal community. By alleviating the inhibition effects of O3 on N-cycling-related genes (ko00910) of soil microorganisms, SCNF improved the activities of related enzymes and might have great potential in improving soil N retention. The results demonstrated the ability of SCNF to improve leaf photosynthetic function and increase crop yield under O3-polluted conditions in the farmland ecosystem, which may become an effective nitrogen fertilizer management measure to cope with the elevated ambient O3 and achieve sustainable production.

Integrating NDVI, SPAD, and Canopy Temperature for Strategic Nitrogen and Seeding Rate Management to Enhance Yield, Quality, and Sustainability in Wheat Cultivation

This study explores the interplay between nitrogen doses and seeding rates on wheat yield, biomass, and protein content. Utilizing tools such as the Normalized Difference Vegetation Index (NDVI), Soil Plant Analysis Development (SPAD) measurements, and canopy temperature (CT), we conducted experiments over five growing seasons. The treatments included three nitrogen levels (0, 60, 120 kg/ha) and three seeding rates (300, 400, 500 seeds/m2) in a split-plot design with 90 plots and two replications. Our results show that an intermediate nitrogen dose (60 kg/ha) combined with a moderate seed rate (400 seeds/m2) enhances wheat yield by 22.95%. Reduced nitrogen levels increased protein content, demonstrating wheat's adaptive mechanisms under nitrogen constraints. NDVI analysis highlighted significant growth during the tillering phase with high nitrogen, emphasizing early-stage nutrient management. SPAD measurements showed that early nitrogen applications boost chlorophyll content, essential for vigorous early growth, while CT data indicate that optimal nitrogen and seed rates can effectively modulate plant stress responses. As crops mature, the predictive capacity of NDVI declines, indicating the need for adjusted nitrogen strategies. Collectively, these findings advocate for refined management of nitrogen and seeding rates, integrating NDVI, SPAD, and CT assessments to enhance yields and promote sustainable agricultural practices while minimizing environmental impacts.

The response of nutrient cycle, microbial community abundance and metabolic function to nitrogen fertilizer in rhizosphere soil of Phellodendron chinense Schneid seedlings

Nitrogen (N) as an essential macronutrient affects the soil nutrient cycle, microbial community abundance, and metabolic function. However, the specific responses of microorganisms and metabolic functions in rhizosphere soil of Phellodendron chinense Schneid seedlings to N addition remain unclear. In this study, four treatments (CK, N5, N10 and N15) were conducted, and the soil physicochemical properties, enzyme activities, microbial community abundances and diversities, metabolism, and gene expressions were investigated in rhizosphere soil of P. chinense Schneid. The results showed that N addition significantly decreased rhizosphere soil pH, among which the effect of N10 treatment was better. N10 treatment significantly increased the contents of available phosphorus (AP), available potassium (AK), ammonium nitrogen (NH4+-N), nitrate nitrogen (NO3--N) and sucrase (SU) activity, as well as fungal diversity and the relative expression abundances of amoA and phoD genes in rhizosphere soil, but observably decreased the total phosphorus (TP) content, urease (UR) activity and bacterial diversity, among which the pH, soil organic matter (SOM), AP, NH4+-N and NO3--N were the main environmental factors for affecting rhizosphere soil microbial community structure based on RDA and correlation analyses. Meanwhile, N10 treatment notably enhanced the absolute abundances of the uracil, guanine, indole, prostaglandin F2α and γ-glutamylalanine, while reduced the contents of D-phenylalanine and phenylacetylglycine in rhizosphere soil of P. chinense Schneid seedlings. Furthermore, the soil available nutrients represented a significant correlation with soil metabolites and dominant microorganisms, suggesting that N10 addition effectively regulated microbial community abundance and metabolic functions by enhancing nutrient cycle in the rhizosphere soil of P. chinense Schneid seedlings.

The Inhibiting Effects of High-Dose Biochar Application on Soil Microbial Metagenomics and Rice (Oryza sativa L.) Production

Biochar is usually considered as an organic improver which can improve soil and increase crop yields. However, the unrestricted application of biochar to normal-fertility farmland will cause chemical stress on crops and affect agricultural production. At present, the effects and mechanisms of high-dose applications of biochar on rice (Oryza sativa L.) production and soil biological characteristics have not been fully studied. In this greenhouse pot experiment, combined with soil microbial metagenomics, three treatments in triplicates were conducted to explore the responses of rice production, soil chemical properties, and soil biological properties to high-dose applications of biochar (5%, w/w) prepared using peanut waste (peanut hulls and straw). The results show that peanut hulls, with a loose texture and pore structure, are a raw material with stronger effects for preparing biochar than peanut straw in terms of its physical structure. In a rice monoculture system, high-dose applications of biochar (5%, w/w) can slightly increase the grains per spike, while significantly inhibiting the spike number per pot and the percentage of setting. High-dose applications of biochar also have significant negative effects on the diversity and stability of soil bacterial and archaeal communities. Moreover, the microbial metabolism and nutrient cycling processes are also significantly affected by changing the soil carbon/nitrogen ratio. This study discusses the response mechanisms of rice production and soil biology to high-dose biochar applications, and complements the understanding of irrational biochar application on agricultural production and land sustainability.

UVB-Pretreatment-Enhanced Cadmium Absorption and Enrichment in Poplar Plants

The phenomenon of cross adaptation refers to the ability of plants to improve their resistance to other stress after experiencing one type of stress. However, there are limited reports on how ultraviolet radiation B (UVB) pretreatment affects the enrichment, transport, and tolerance of cadmium (Cd) in plants. Since an appropriate UVB pretreatment has been reported to change plant tolerance to stress, we hypothesized that this application could alter plant uptake and tolerance to heavy metals. In this study, a woody plant species, 84K poplar (Populus alba × Populus glandulosa), was pretreated with UVB and then subjected to Cd treatment. The RT-qPCR results indicated that the UVB-treated plants could affect the expression of Cd uptake, transport, and detoxification-related genes in plants, and that the UVB-Pretreatment induced the ability of Cd absorption in plants, which significantly enriched Cd accumulation in several plant organs, especially in the leaves and roots. The above results showed that the UVB-Pretreatment further increased the toxicity of Cd to plants in UVB-Cd group, which was shown as increased leaf malonaldehyde (MDA) and hydrogen peroxide (H₂O₂) content, as well as downregulated activities of antioxidant enzymes such as Superoxide Dismutase (SOD), Catalase (CAT), and Ascorbate peroxidase (APX). Therefore, poplar plants in the UVB-Cd group presented a decreased photosynthesis and leaf chlorosis. In summary, the UVB treatment improved the Cd accumulation ability of poplar plants, which could provide some guidance for the potential application of forest trees in the phytoremediation of heavy metals in the future.