Li Wen

Lodging is a major constraint limiting grain yield in dry direct seeding rice (DDSR), yet the key traits and phenotypic relationships governing lodging resistance in japonica varieties adapted to this system remain poorly understood. This study evaluated 79 japonica accessions over two years in Shenyang, Northeast China, to dissect phenotypic variation in lodging index and identify ideotypes for breeding. Based on hierarchical clustering, varieties were classified into strong lodging resistance (SLR), medium lodging resistance (MLR), and weak lodging resistance (WLR) types, with SLR varieties achieving lodging indices 27.4–31.8% lower than those of MLR and 63.2–83.8% lower than those of WLR varieties. SLR varieties reduced lodging risk by coordinately balancing whole-plant bending moment and stem breaking resistance: plant height and center-of-gravity height were 5.2–10.7% lower, while basal internode bending stress was 27.9–81.9% higher than in other types. Structural equation modeling identified culm dry weight, inner diameter, and culm phenotype index as primary determinants of lodging variation. Notably, despite 11.0–13.7% fewer spikelets per panicle, SLR varieties maintained grain yields comparable to those of WLR varieties through compensatory increases in grain-filling rate (6.7–7.3%) and 1000-grain weight (8.1–8.7%). These findings demonstrate that optimizing basal internode structure and enhancing culm tissue density can simultaneously improve lodging resistance and preserve yield potential, providing a practical framework for breeding lodging-resistant, high-yielding japonica varieties for DDSR systems in Northeast China.

Weed control in rice remains a critical challenge in direct-seeded rice cultivation. This study combined field and laboratory experiments to compare the efficacy of nine herbicide combinations against weeds in dryland rice fields and to evaluate their impact on rice economic traits. A model was constructed using principal component analysis for comprehensive evaluation, aiming to identify optimal herbicide combinations for direct-seeded rice under shallow drip irrigation in Hinggan League. The results indicate that pendimethalin provides better pre-emergence control compared to oxadiargyl and pretilachlor. The combination of florpyrauxifen-benzyl + benzobicyclon provided optimal weed control efficacy and rice economic performance when applied as a foliar treatment. Forty-five days after application, weed control efficacy against Echinochloa crus-galli (L.) P. Beauv. and Amaranthus retroflexus L. was 72% and 85%, respectively, with fresh weight reduction of 63%. Theoretical yield reached 4285.48 kg·ha⁻¹. At rice harvest, no herbicide residues were detected in rice straw or grains across all treatments, confirming the safety of the applied treatment for rice. Principal component analysis (PCA) was used to evaluate the comprehensive scores of each treatment, with pendimethalin + florpyrauxifen-benzyl + benzobicyclon achieving the highest score of 0.65. The study indicates that the combination of pendimethalin as a pre-emergence and florpyrauxifen-benzyl + benzobicyclon offers significant advantages in weed control efficacy and rice growth, achieving the highest comprehensive evaluation score. This combination holds important application value for weed control and grain yield assurance in direct-seeded rice fields.

This study assessed the impact of planting techniques and short-term organic additions on soil quality, enzyme activity, and bacterial community composition. Biochar (BC) amendment substantially enhanced the ACE, Chao 1, and Shannon indices in direct-seeded rice (DS). Principal coordinate analysis (PCoA) and dissimilarity distances confirmed significant differences in the rhizosphere bacterial community composition associated with planting methods and organic applications. At the phylum level, transplanting (TT) significantly increased the abundance of Proteobacteria, Planctomycetes, Bacteroidetes, Firmicutes, and Verrucomicrobia, whereas DS significantly reduced the abundance of Acidobacteria, Chloroflexi, Actinobacteria, Gemmatimonadetes, and WPS-2. Rice straw (RS) application was associated with increased Proteobacteria, Acidobacteria, Chloroflexi, and Gammaproteobacteria, while BC application improved Bacteroidetes, Firmicutes, and Verrucomicrobia. Planting methods and organic amendments were also observed to affect soil enzyme activities and physicochemical properties. DS was associated with an increase in microbial biomass nitrogen (MBN) and carbon (MBC), cellulase activities (CA), total phosphorus (TP), available nitrogen (AN), and available potassium (AK), while TT significantly increased urease activities (UA). Compared to BC and the control (CK), RS significantly increased CA, AN, and available phosphorus (AP). RDA ordination plots were used to examine the interactions between soil bacterial communities and soil physicochemical properties; planting techniques and organic additions had different effects on soil bacterial communities. Compared to RS and CK, BC enhanced MBN, MBC, UA, and AK. According to Pearson’s correlation analysis, Chloroflexi levels were positively associated with those of organic carbon (OC), MBN, and MBC. OC, TP, MBN, and CA positively correlated with gemmatimonadetes. In conclusion, these data reveal that planting practices and short-term organic inputs alter soil’s physicochemical parameters, enzyme activity, and microbial community composition.