Given the worsening global climate change that drives drought frequency and irrigation water shortages, implementing water-conserving practices like alternate wetting and drying (AWD) is now critically urgent. Biochar is widely used for soil carbon sequestration. However, there is limited information on the effects of biochar on soil organic carbon (SOC) and its labile fractions in paddy fields, especially under AWD. A two-year field experiment was conducted with two irrigation regimes (CF: continuous flooding irrigation; AWD) as the main plots and 0 (B₀) and 20 t ha⁻¹ (B₁) biochar as sub-plots. AWD had no effect on the SOC and particulate organic carbon (POC) content, but increased the dissolved organic carbon (DOC), microbial biomass carbon (MBC), easily oxidizable organic carbon (EOC), light fraction organic carbon (LFOC), and carbon pool management index (CPMI) at 0–10 cm depths, by 24.4–56.4%, 12.6–17.7%, 9.2–16.8%, 25.6–28.1%, and 11.3–18.6%, respectively. Biochar increased SOC while also increasing DOC, MBC, EOC, LFOC, POC, and CPMI at 0–20 cm depths, by 18.4–53.3%, 14.7–70.2%, 17.4–22.3%, 10.2–27.6%, 95.2–188.3%, 46.6–224%, and 5.6–27.2, respectively, making SOC more labile under AWD. Our results highlight that biochar still holds great potential for improving soil quality and carbon sequestration under AWD, and the combination of biochar and AWD can achieve the synergistic optimization of the food–water–carbon sequestration trade-off, which is beneficial to sustainable agricultural production.

With the continuous rise in global temperatures, heat stress has become a significant threat to rice (Oryza sativa L.) growth and yield. MYB transcription factors, the largest family of genes in plants, play a crucial role in mediating responses to various abiotic stresses. However, the specific functions of MYB genes in rice under heat stress remain largely unexplored. In this study, we conducted a comprehensive genome-wide characterization of the MYB transcription factor family and performed an RNA-seq analysis to identify OsMYB genes that are responsive to heat stress. We identified 229 MYB genes in rice, 134 of which exhibited significant expression changes under heat treatment. An RT-qPCR analysis validated the RNA-seq results for 15 MYB genes, confirming significant expression changes, such as the upregulation of Os02g0685200 after heat stress and the downregulation of Os05g0579600. Six highly responsive genes were selected for further analysis. Cis-acting elements associated with hormone response and abiotic stress were identified in the promoter regions of these genes. A subcellular localization analysis revealed that, except for Os05g0579600, which located to both the nucleus and cytoplasm, the other MYB genes (Os01g0192300, Os02g0685200, Os06g0637500, Os06g0669700, and Os09g0106700) were predominantly located in the nucleus. In yeast, Os01g0192300, Os06g0637500, and Os06g0669700 exhibited transcriptional activation activity, while Os02g0685200 and Os09g0106700 showed transcriptional repression activity. Notably, these genes responded not only to heat stress but also to other abiotic stresses, such as cold, salt, and heavy metal cadmium. This study provides valuable insights into the functional roles of OsMYB family genes in the heat stress response, identifying Os01g0192300, Os02g0685200, Os05g0579600, Os06g0637500, Os06g0669700, and Os09g0106700 as potential key genes involved in heat tolerance in rice.

Nitrogen (N) and potassium (K) co-management is critical for optimizing grain yield in rice. However, the interactive effects of N supply and K application timing on cultivars with contrasting N efficiencies remain poorly understood. Here, we conducted a two-year field experiment (2020 and 2021) using two japonica rice cultivars, Shennong 265 (SN265) and Meifengdao 61 (MFD61), under three N rates (180, 225, and 270 kg ha⁻¹) and three K application ratios (basal: panicle = 3:7, 5:5, and 7:3). SN265 exhibited a 20.31% higher average grain yield than MFD61, primarily attributable to increased crop growth rates during the tillering–booting (14.08%) and grain-filling–maturity phases (31.88%). Under moderate N supply (N₁₈₀ and N₂₂₅), increasing the proportion of basal K application (K_7:3) consistently improved dry matter accumulation, enzyme activity, and grain yield in both cultivars. However, under high-N conditions (N₂₇₀), excessive early-season K application reduced grain yield in MFD61 by 7.69%. For SN265, further yield improvement required an enhanced net assimilation rate during the tillering–booting phase. Although this study was conducted at a single site with only two cultivars, it provides a physiological and agronomic framework for cultivar-specific N–K co-management strategies to improve grain yield and nutrient use efficiency.

Introduction: Straw biochar can significantly increase the content of available potassium (K) in soil, whereas its regulatory effect on soil K supply capacity remains unclear and lacks long-term field verification. To clarify the response mechanism of soil K supply capacity to long-term straw biochar amendment, a 9-year continuous field experiment was carried out to explore the improvement effect of straw biochar on soil K supply characteristics and K uptake by maize. Methods: This study was conducted based on a long-term field experiment in Shenyang Agricultural University under a humid and sub-humid monsoon climate, with Haplic Luvisols as the tested soil. After 9 consecutive maize growing seasons, soil samples at the 0–20 cm depth were collected. A two-factor randomized block design was set up with four treatments, including B0K0 (no biochar and no K fertilizer), B0K1 (K fertilizer only), B1K0 (biochar only), and B1K1 (biochar with K fertilizer). Results: 9 consecutive years of straw biochar application significantly increased illite content. Compared to B ₀ K ₀ , the illite proportion in B ₁ K ₀ and B ₁ K ₁ increased by 16.15% and 19.84%, respectively. The soil K quantity/intensity (Q/I) curve and K release kinetic curves showed that biochar significantly improved soil K supply pool (−ΔK ₀ ) and K supply intensity (ARe) by 60.76% and 36.06%. In addition, biochar reduced the content of exclusively adsorbed K (K _x ) and the free exchange energy of K (−ΔG), and effectively increased the cumulative release of soil K. Discussion: These variations induced by biochar application effectively alleviated the negative K balance of farmland soil, comprehensively improved soil K supply capacity, and facilitated K uptake and utilization of maize, which further promoted the accumulation of plant dry matter. This long-term field study confirms that the combined application of straw biochar and K fertilizer is an effective measure to improve soil K availability, which provides reliable scientific basis for K nutrient regulation in farmland soil.

To investigate the effects of long-term biochar application on different forms of potassium (K) content in maize rhizosphere soil and maize growth, two biochar application rates (B0: 0 t ha⁻¹ yr⁻¹, B1: 2.625 t ha⁻¹ yr⁻¹) and two K fertilizer application rates (K0: 0 kg ha⁻¹ yr⁻¹, K1: 60 kg ha⁻¹ yr⁻¹) to create four treatments (B0K0, B0K1, B1K0, B1K1). In this long-term field trial, we investigated various forms of K in the maize rhizosphere soil, together with soil physicochemical properties and maize growth indicators. Results indicate that biochar significantly increased microbial biomass carbon (MBC), cation exchange capacity (CEC), and electrical conductivity (EC) in the rhizosphere soil, while also improving rhizosphere soil pH. Compared with the treatment without biochar, biochar application significantly increased the content of water-soluble potassium (WSK), exchangeable potassium (EK), and non-exchangeable potassium (NEK) in the rhizosphere soil by 18.57% (2021) and 11.18% (2022), 13.49% (2021), and 11.43% (2022), 14.65% (2021), and 17.06% (2022), respectively. Maize roots were more developed, and plant height, stem diameter, and leaf area index were significantly increased. With above-ground dry weight and K uptake significantly increasing by 13.87% (2021) and 12.04% (2022), and 41.84% (2021) and 43.87% (2022), respectively. Compared with B0K0, the B1K1 treatment—which combined biochar with K fertilizer—exhibited the highest K content in all forms within the rhizosphere soil, along with the greatest maize aboveground dry weight and K uptake. This study demonstrates biochar’s potential in meeting crop root K demands, laying the foundation for its application in enhancing soil K fertility.

As an organic soil amendment, biochar can effectively increase the contents of soil nutrients such as nitrogen (N), phosphorus (P), and potassium (K). However, few studies have focused on the effects of biochar on K fractions and contents in maize rhizosphere soil. To investigate the effects of biochar on different K fractions in maize rhizosphere soil and on maize growth, four treatments were established in this experiment: B₀K₀ (control, no biochar and no K fertilizer), B₀K₁ (no biochar, K fertilizer at 60 kg ha⁻¹ yr⁻¹), B₁K₀ (biochar at 2.625 t ha⁻¹ yr⁻¹, no K fertilizer), and B₁K₁ (biochar at 2.625 t ha⁻¹ yr⁻¹ combined with K fertilizer at 60 kg ha⁻¹ yr⁻¹). Results indicate that biochar significantly increased microbial biomass carbon (MBC), cation exchange capacity (CEC), and electrical conductivity (EC) in the rhizosphere soil, while also improving rhizosphere soil pH. Compared with the treatment without biochar, biochar application significantly increased the content of water-soluble potassium (WSK), exchangeable potassium (EK), and non-exchangeable potassium (NEK) in the rhizosphere soil by 18.57% (2021) and 11.18% (2022), 13.49% (2021) and 11.43% (2022), 14.65% (2021) and 17.06% (2022), respectively. However, the increases in different K fractions were not accompanied by significant changes in total K (TK) content across the two years. In addition, biochar application significantly improved maize root development, plant height, stem diameter, and leaf area index. Meanwhile, aboveground dry weight and K uptake increased significantly by 13.87% (2021) and 12.04% (2022), and 41.84% (2021) and 43.87% (2022), respectively. Compared with B₀K₀, the B₁K₁ treatment—which combined biochar with K fertilizer—exhibited the highest K content in all forms within the rhizosphere soil, along with the greatest maize aboveground dry weight and K uptake. This study demonstrates biochar’s potential in meeting crop root K demands, laying the foundation for its application in enhancing soil K fertility.