Optimizing Deep Nitrogen Placement and Silicon Fertilizer Use for Enhanced Rice Productivity and Lodging Resistance Under Different Irrigation Modes

Optimization of nitrogen–silicon (N-Si) fertilization for grain yield and lodging resistance of early-season indica fragrant rice under different planting methods

Characteristics of lodging resistance of high-yield winter wheat as affected by nitrogen rate and irrigation managements

Reducing nitrogen fertilizer application, selecting a reasonable planting density, and adding silicon fertilizer can be used together to decrease excessive nitrogen fertilizer inputs in rice fields, reduce production costs, and ensure stable rice yield. However, the dynamics of the stem and internodes, as well as the changes in the physical and physiological characteristics of rice under a combination of these three strategies, are still unclear. In this study, we aimed to clarify these effects to improve the efficiency of rice production in northeastern China. A 2-year field experiment was conducted using five treatments: a conventional densification treatment (DM), a densification combined with reduced N input (−20%) treatment (DLM), and three densifications combined with reduced N input (−20%) and basal silicon fertilizer treatments (low fertilizer: DLMS1; medium fertilizer: DLMS2; and high fertilizer: DLMS3). This study revealed that the addition of silicon fertilizer improved rice yield compared to that under reduced nitrogen or increased density treatments alone, prevented excessive ineffective tillering after a density increase, and increased the number of productive panicles. Among the treatments, the DLMS3 treatment had the highest yields of 10.53 t/ha and 10.73 t/ha over the 2 years. Reducing nitrogen and increasing density reduced the weight and length of single panicles, while the addition of silicon fertilizer was beneficial for improving stem toughness, improving the physical and physiological characteristics of the plants and panicles, and enhancing plant bending resistance. Among the treatments, DLMS3 had the highest bending resistance, which increased by 440.1 g and 503.8 g compared to the lowest values in the DM treatment in 2020 and 2021, respectively. Nitrogen reduction resulted in the lowest lodging index values, with DLMS3 having the lowest values in both years, which decreased by 19.6% and 22.5% compared to the highest values in DM (2020) and DLM (2021), respectively. This study indicates that the application of 150.0 kg/ha silicon fertilizer in combination with reduced nitrogen and increased density (DLMS3) reduces the lodging index while ensuring rice yield, preventing a tradeoff between yield reduction and lodging due to a density increase or due to nitrogen reduction combined with a density increase and allowing for a reduction in nitrogen fertilizer input, which could ensure a uniform yield and an increase in lodging resistance. These results provide a scientific basis for rice cultivation measures that lead to high yield and lodging resistance while protecting the environment.

Lodging in crops seriously restricts plant growth and grain production. The genetic modification of cell walls to enhance plant mechanical strength has been suggested as a promising approach toward improving lodging resistance. However, because of the complexity of the plant cell wall, the exact effects of its polymers on plant lodging resistance remain elusive. To address this issue, we performed large-scale analyses of a total of 56 rice (Oryza sativa L.) varieties that displayed distinct cell wall component and lodging index. Lignin was identified as the key cell wall polymer that positively determines lodging resistance in rice. Correlation analysis between cell wall composition and plant morphological characteristics revealed that lignin enhanced rice lodging resistance by largely increasing the mechanical strength of the basal stem and reducing plant height. Further characterization of four representative rice varieties, ShenNong9903, YanJian218, KongYu131, and ShenNongK33, displaying varied levels of lodging resistance, revealed the multiple candidate genes (PAL, CoMT, 4CL3, CAD2, CAD7 and CCR20) responsible for increasing lignin level. Hence, our results demonstrate that the high lignin level in the cell wall predominately improves lodging resistance and suggest target genes for the genetic modification of lignin towards breeding rice with high lodging resistance.

High grain yields of rice (Oryza sativa) under dry cultivation are primarily obtained through high levels of nitrogen (N) input. However, excessive inputs of N increase the risk of lodging. This study aimed to clarify the effect of N application rates on crop morphology, mechanical mechanisms of the stem, and chemical components in the basal stems of rice and their underlying mechanism in association with lodging resistance under dry cultivation. In this study, field experiments on rice were conducted under dry cultivation in early May to early October 2019 and 2020. Six rates of N applied at 0, 70, 140, 210, 280 and 350 kg ha−1 were set at a sowing rate of 150 kg ha−1 with Suijing 18 as the test material. The increased risk of lodging represented by lodging index (LI) and lodging rate with increasing N application was observed under both growing seasons. The plant height, basal internode length, particularly the second internode, and center of gravity height, which positively correlated with the LI, increased significantly with the increase in N application rates. In contrast, internode fullness and carbohydrate content of the basal second (S2) internode, which negatively correlated with LI, decreased significantly with increasing N application rates. A quadratic regression model between N application rates and grain yield showed that better grain yield could be achieved under an N application rate ranging from 210 to 228 kg ha−1. Therefore, the N application rate of (i.e., 210–228 kg N ha−1) could be recommended for the Suijing18 variety under dry cultivation in central Jilin Province for achieving high grain yield and great lodging resistance.

Genetic progress in stem lodging resistance of the dominant wheat cultivars adapted to Yellow-Huai River Valleys Winter Wheat Zone in China since 1964

Rice is an important crop that significantly contributes to food security. Lodging is considered an important factor limiting rice yield and quality. The objective of this study was to investigate the effects of carbon and nitrogen on lodging in fragrant rice. A 2-year field experiment (2021 to 2022) was conducted with the fragrant rice cultivars Meixiangzhan 2 and Xiangyaxiangzhan grown under nine carbon and nitrogen co-application treatments (CK: 0 mg/L glucose + 0 mg/L urea; T1: 0 mg/L glucose + 50 mg/L urea; T2: 0 mg/L glucose + 100 mg/L urea; T3: 150 mg/L glucose + 0 mg/L urea; T4: 150 mg/L glucose + 50 mg/L urea; T5: 150 mg/L glucose + 100 mg/L urea; T6: 300 mg/L glucose + 0 mg/L urea; T7: 300 mg/L glucose + 50 mg/L urea; and T8: 300 mg/L glucose + 100 mg/L urea). The lodging index and stem characteristics of fragrant rice were investigated. Compared with the CK treatment, the T5 and T7 treatments significantly increased the pushing resistance force by 22.22–127.78% and 50.00–77.50%, respectively. Compared with the other fertilization treatments, the T5 treatment kept the lodging index at a low level and reduced the plant height. The stem characteristics were regulated under the carbon and nitrogen co-application treatments, and the internode length and dry weight significantly influenced the plant height and the pushing resistance force and then regulated the lodging index. Structural equation modeling and random forest modeling analyses suggest that carbon and nitrogen co-application treatments may further improve the resistance of rice to lodging by increasing the dry weight of the third and fourth internodes. Overall, optimized carbon and nitrogen co-application could regulate stem internode morphology and improved lodging resistance. Furthermore, the T5 treatment (150 mg/L glucose + 100 mg/L urea) improved lodging resistance. This study provides guidelines for enhancing lodging resistance by regulating internode characteristics via the co-application of carbon and nitrogen at the booting stage in fragrant rice.

An improvement in oilseed rape (Brassica napus L.) productivity through optimization of rice-straw quantity and plant density

IntroductionImbalanced N–K ratios reduce nutrient uptake efficiency while increasing lodging susceptibility, thereby destabilizing yield potential. Optimizing N–K ratios is therefore crucial for improving nutrient efficiency, lodging resistance, and yield potential.MethodsThis study employed the hybrid indica rice cultivar F-you 498 as experimental material. Two K management strategies (basal:panicle = 10:0 and 5:5, denoted as K1 and K2) and three N application regimes (basal:tiller:panicle = 7:3:0, 5:3:2, and 3:3:4, denoted as N1, N2, and N3) were tested. Both fertilizers were applied at identical total rates of 150 kg ha-¹ for N and K to investigate N–K interactions on rice growth and nutrient utilization.ResultsN–K interactions significantly affected dry matter accumulation, nutrient uptake, lodging resistance, and yield. Split potassium application (K2) increased grain yield by 3.06% compared with basal-only application (K1), by increasing productive panicles, spikelets per panicle, total spikelets, and seed-setting rate. K2 enhanced post-heading dry matter translocation and improved N–K uptake, elevating panicle N and K accumulation by 5.01% and 13.70%, respectively. K2 also significantly improved lodging resistance. Under K2, the N3 treatment further increased yield by enhancing the number of effective panicles, grains per panicle, and total spikelets, with average yield increases of 12.17% and 4.77% compared with N1 and N2, respectively. Post-heading dry matter accumulation, remobilization ratio, and contribution rate in N3 were higher than in N1 and N2, with two-year average increases of 25.54%, 5.37%, and 7.42% compared with N1, and 12.68%, 2.76%, and 2.57% compared with N2. N3 also promoted the translocation of N and K. Compared with N1 and N2, N3 increased whole-plant N translocation and N transferred to the panicle by 38.09% and 27.45%, and by 14.53% and 12.45%, respectively; whole-plant K translocation and K transferred to the panicle increased by 11.46% and 28.26%, and by 13.35% and 18.35%, respectively. Additionally, N3 improved lodging resistance by thickening internodes and stem-sheath walls. The lodging index was significantly negatively correlated with N and K accumulation in stem-sheaths.DiscussionOverall, the K2N3 combination enhances post-heading assimilate allocation and nutrient translocation in machine-transplanted rice, strengthens stem mechanical properties, optimizes panicle traits, and ultimately achieves stable and high yields.

This study was aimed to investigate the effects of organic carbon and silicon fertilizers on the lodging resistance, yield, and economic performance of rapeseed. Two cultivars, namely Jayou (lodging-resistant) and Chuannongyou (lodging-susceptible), were selected to evaluate the effects of various fertilizer treatments on rapeseed culm morphology, lignin accumulation, and their relationships with their lodging resistance indices. The results showed that both organic carbon and silicon fertilizer applications increased the plant height, basal stem diameter, internode plumpness, and bending strength of rapeseed in both the studied years. The bending strength was significantly and positively correlated with the lodging resistance index and lignin content. It was found that both organic carbon and silicon fertilizers had improved the activities of lignin biosynthesis enzymes (phenylalanine ammonia-lyase, 4-coumarate:CoA ligase, cinnamyl alcohol dehydrogenase, and peroxiredoxins) and their related genes to increase lignin accumulation in the culm, which ultimately improved the lodging resistance. At the same time, the thickness of the stem cortex, vascular bundle area, and xylem area was increased, and the stem strength was improved. The effect of silicon fertilizer was better than that of organic carbon fertilizer, but there was no significant difference with the mixed application of silicon fertilizer and organic carbon fertilizer. Similarly, silicon fertilizer increased the number of pods, significantly increased the yield, and improved the economic benefit, while organic carbon fertilizer had no significant effect on the yield. Therefore, we believe that organic carbon and silicon fertilizer can improve the lodging resistance of rape stems by improving the lignin accumulation and the mechanical tissue structure. Still, the effect of silicon fertilizer is the best. Considering the economic benefits, adding silicon fertilizer can obtain more net income than the mixed application of silicon fertilizer and organic carbon fertilizer.

Rice yield could be increased by apply higher level of nitrogen fertilizer, but excessive use of nitrogen fertilizer will cause plant lodging. This study aimed to investigate the effect of nitrogen application rate on lodging resistance of rice stems. Four japonica rice varieties with different lodging resistance were used, and six nitrogen fertilizer levels were set up to analyze the morphological structure, mechanical properties, and chemical components of rice stems under such treatments. The dynamic changes of lodging resistance of rice stems under different nitrogen fertilizer application rates were exanimated. The study provide valuable insights for improving lodging resistance and subsequently increasing rice yield. The results indicated that WYD4 exhibited the highest yield under the N1 treatment, whereas JYJ, JJ 525, and JND 667 achieved the highest yield under the N2 treatment. The lodging index of rice varieties fluctuated at the filling stage, peaking 30 days after heading. Moreover, the lodging index increased progressively with higher nitrogen fertilizer application rates, reaching its maximum under the N5 treatment, which corresponded to an increased lodging risk. Specifically, the lodging index under the N5 treatment increased by 0.63–1.21 times compared to the optimal nitrogen fertilizer level. Concurrently, the fracture bending point (s) and lodging resistance of the rice stem exhibited a gradual decline. Additionally, plant height, internode length, and barycenter height significantly increased with rising nitrogen application rates and were positively correlated with the lodging index. Conversely, the wall thickness of the second basal node decreased and showed a negative correlation with the lodging index. Furthermore, the contents of lignin, cellulose, soluble sugar, and starch in the second internode diminished with increasing nitrogen rates, and were positively correlated with the breaking moment.

Lodging is a limiting factor for rice production in the Sichuan Basin, China. However, the mechanisms of stem lodging resistance, especially its regulation by plant growth regulators are still unclear. A two-year field study, by using the three foliar application rates of uniconazole with two rice varieties, Yuxiang203 (YX203) and C-Liangyouhuazhan (CLYHZ), was conducted to determine stem lodging resistance and its morphological and anatomical mechanisms in rice plants. The results revealed that, compared with that in 2019, the grain yield in 2020 significantly decreased, whereas the lodging index (LI) significantly increased. Uniconazole treatment increased the rice yield by 4.6%−11.2% and 2.1%−7.0%, and decreased LI by 21.1%−33.9% and 11.4%−29.6% in YX203 and CLYHZ, respectively. Uniconazole treatment shortened the length of the basal internodes by 19.5%−33.0% (YX203) and 24.7%−40.7% (CLYHZ), resulting in a significant reduction in plant height. Uniconazole treatment increased the mechanical tissue thickness, areas of small and larger vascular bundles, and culm diameter and further increased the breaking strength of the two varieties. Cell wall components, including cellulose and lignin, were increased by foliar application of uniconazole, thereby creating denser sclerenchyma cells and increasing the thickness of the mechanical tissue and area of the vascular bundle. These results suggest that the application of uniconazole enhances stem mechanical strength via increased mechanical tissue thickness and larger areas of small and large vascular bundles, thereby improving the lodging resistance of rice plants.

Although the introduction of semi-dwarf trait into rice has led to improved lodging resistance making it capable of supporting high grain yield, lodging still remains a concern when attempting to further increase the grain yield of rice. However, improving the lodging resistance in rice by depending on the semi-dwarf trait alone is possible only up to a certain limit, beyond which other traits may be needed for reinforcement. To search for alternative traits relating to high lodging resistance, we identified 9 rice mutant lines possessing improved culm strength. To evaluate whether such lines can be useful for breeding lodging resistant rice, small organ size1 (smos1) mutant having increased lodging resistance but low tiller number and low grain yield, was chosen as a representative for a breeding trial. smos1 was crossed with ST-4 (from the Stock rice collection of Nagoya University Togo field #4), a cultivar with high tiller number and high grain yield, and from their progeny, LRC1 (lodging resistance candidate-1) was selected. Although the low tiller number trait of smos1 was not fully reversed in LRC1, this was compensated by an increase in grain weight per panicle, thereby resulting in high grain yield per plant. This important attribute of LRC1 was further enhanced by the improved lodging resistance trait inherited from smos1. Such improved lodging resistance in LRC1 and smos1 was revealed to be mainly due to increased culm diameter and culm thickness, which led to a high section modulus (SM) value, a parameter defining the physical strength of the culm. Since smos1 possesses high breaking-type lodging resistance which is different from semi-dwarf plants with high bending-type lodging resistance, an alternative approach of using thick culm lines for the creation of rice with increased lodging resistance is hereby proposed.

Poor light stress causes lodging risks in hybrid indica rice (Oryza sativa L.) in Sichuan Basin, China. However, the effective way of improving lodging resistance of hybrid indica rice by plant regulation strategy under poor light stress has not yet been investigated. A 2‐yr field study, comparing the three foliar application uniconazole rates under normal light and shading condition, was conducted to determine the lodging resistance and its physiological mechanism by using two hybrid rice varieties (Yuxiang203 [YX203] and Cliangyouhuazhan [CLYHZ]). The results showed that shading significantly decreased grain yield, but, increased lodging index (LI) due to poor stem breaking strength (M). Also, shading increased the non‐structural carbohydrates (NSC), but reduced structural carbohydrate (SC), especially for lignin in basal culm and thus, weakened the stem stiffness. Grain yield was first increased, and then declined with increasing foliar uniconazole rates. And, LI decreased sharply owing to improvement of M while reduction of bending moment by whole plant (WP). Larger section modulus (SM) of YX203 and higher bending stress (BS) of CLYHZ were contributed to higher M. Correlation analysis showed that M was significantly correlated with culm diameter, culm wall thickness and SC content for YX203, and that with SC content for CLYHZ, respectively. The results indicated that foliar application of uniconazole increased lodging resistance of hybrid indica rice for larger M and SC accumulation in basal stem. Uniconazole foliar application at 40 mg L–1 can increase lodging resistance while maintaining grain yield of hybrid indica rice in the Sichuan Basin, China.

By using a newly developed 'Shooting hill-seeder', it is easy to adjust the hill space within a row or the seeding depth, and change the hill-seeding form in the submerged direct seeding rice cultivation. In this study, the effects of these seeding conditions on the lodging resistance of hill-seeded rice were examined. It was suggested that the increased hill space within a row resulted in lower lodging resistance because of the elongation of culm and decrease in pushing resistance of the hill. These results show the importance to adopt a variety with high lodging resistance, or to control the nitrogen uptake by improvement of fertilizer application or water management, when a large hill space is necessary. On the other hand, the hill-seeding form did not seem to affect the lodging resistance. Furthermore, in hill-seeded rice, the chance of shallow seeding is rare, and the degree of lodging due to shallow seeding is extremely small as compared with broadcast-seeded rice. These characteristics are very important for the stabilization of the submerged direct seeding cultivation, in which unification of the seeding depth is difficult, and the stabilization of seedling emergence is important.