Recent progress on defect-engineering in ferroelectric HfO2: The next step forward via multiscale structural optimization.

The discovery of unconventional scale-free ferroelectricity in HfO2-based fluorite thin films has attracted great attention in recent years for their promising applications in low-power logic and nonvolatile memories. The ferroelectricity of HfO2 is intrinsically originated from the widely accepted ferroelectric metastable orthorhombic Pca21 phase. In the last decade, defect-doping/solid solution has shown excellent prospects in enhancing and stabilizing the ferroelectricity via isovalent or aliovalent defect-engineering. Here, the recent advances in defect-engineered HfO2-based ferroelectrics are first reviewed, including progress in mono-ionic doping and mixed ion-doping. Then, the defect-lattice correlation, the point-defect promoted phase transition kinetics, and the interface-engineered dynamic behaviour of oxygen vacancy are summarized. In addition, thin film preparation and ion bombardment doping are summarized. Finally, the outlook and challenges are discussed. A multiscale structural optimization approach is suggested for further property optimization. This article not only covers an overview of the state-of-art advances of defects in fluorite ferroelectrics, but also future prospects that may inspire their further property-optimization via defect-engineering.

No-tillage with straw mulching promotes the utilization of soil nitrogen by rice under wheat-rice and oilseed rape-rice cropping systems.

Introduction: To investigate the effects of no-tillage with straw mulching on the absorption and utilization of soil nitrogen (N), fertilizer N, and straw N by rice under paddy-upland rotations. Methods: A field experiment with three cropping systems: fallow-rice rotation without straw mulching (FRN), wheat-rice rotation with wheat mulching in rice season (WRS), and oilseed rape-rice rotation with oilseed rape straw mulching in rice season (ORS) was conducted from 2015 to 2017, along with a mini-plot experiment with 15N-labeled urea and straws, which was conducted in 2017. Results: No-tillage with straw reduced rice N uptake up to 20 days after transplanting, the total amount of fertilizer N uptake of WRS and ORS rice plants was 46.33 and 61.67 kg/ha, respectively, which was 9.02 and 45.10% higher than that of FRN plants. Soil N was the main source for rice growth, followed by fertilizer N. Soil N uptake by WRS and ORS rice plants was 21.75 and 26.82% higher than that of FRN plants, accounting for 72.37 and 65.47%, respectively, of the total N accumulated in rice plants. Straw mulching increased the N utilization efficiency of tillering, panicle, and total fertilizer by 2.84-25.30%; however, base fertilizer was dependent on straw mulching. The total amount of N released from WRS and ORS straw mulching in the rice season was 34.97 and 24.82 kg/ha, respectively; however, only 3.04 and 4.82% of it was absorbed by the rice plants, accounting for only 0.62 and 0.66% of the total accumulated N. Discussion: No-tillage with straw mulching under paddy-upland rotations increased the N utilization of rice, especially for the absorption of soil N. These results provide theoretical information for the effective utilization of straw and rational N application practices in rice-based cropping systems.

Nitrogen Application Rate Affects the Accumulation of Carbohydrates in Functional Leaves and Grains to Improve Grain Filling and Reduce the Occurrence of Chalkiness.

Chalkiness, which is highly affected by nitrogen (N) management during grain filling, is critical in determining rice appearance quality and consumer acceptability. We investigated the effects of N application rates 75 (N1), 150 (N2), and 225 (N3) kg ha-1 on the source-sink carbohydrate accumulation and grain filling characteristics of two indica hybrid rice cultivars with different chalkiness levels in 2019 and 2020. We further explored the relationship between grain filling and formation of chalkiness in superior and inferior grains. In this study, carbohydrates in the functional leaves and grains of the two varieties, and grain filling parameters, could explain 66.2%, 68.0%, 88.7%, and 91.6% of the total variation of total chalky grain rate and whole chalkiness degree, respectively. They were primarily concentrated in the inferior grains. As the N fertilizer application rate increased, the chalky grain rate and chalkiness degree of both the superior and inferior grains decreased significantly. This interfered with the increase in total chalky grain rate and chalkiness. Moreover, the carbohydrate content in the functional leaves increased significantly in N2 and N3 compared with that in N1. The transfer of soluble sugar from the leaves to the grains decreased the soluble sugar and increased total starch contents, accelerated the development of grain length and width, increased grain water content, and effectively alleviated the contradiction between source and sink. These changes promoted the carbohydrate partition in superior and inferior grains, improved their average filling rate in the middle and later stages, optimized the uniformity of inferior grain fillings, and finally led to the overall reduction in rice chalkiness.