Hybrid rice has a higher yield potential than inbred rice, but the difference in nitrogen (N) use efficiency between hybrid rice and inbred rice remains unclear. The objective of this study was to examine the effects of hybrid rice on yield and N use efficiency through meta-analysis techniques.

The peer-reviewed articles were collected, which included inbred rice as the control in comparison with a hybrid rice treatment. In total, the dataset included 56 studies involving 367 paired observations. Then, the meta-analysis was conducted to identify the response of grain yield and N use efficiency to hybrid rice as affected by hybrid type, N rate, the number of N application, soil total N content, the ratio of soil organic carbon to N, and soil texture.

Overall, the hybrid rice significantly increased rice yield (+11%) and biomass (+14%), but did not affect harvest index compared with inbred rice. Hybrid rice could improve rice yield relative to inbred rice under various N rates. However, the increase in rice yield under hybrid rice reduced with increasing N application rates. Moreover, the hybrid rice significantly increased N uptake, N physiological efficiency, and N recovery efficiency by 8.1%, 2.9%, and 3.6 units, respectively.

Hybrid rice could improve yield and N use efficiency relative to inbred rice, which provided an insight to evaluate the effect of hybrid rice on grain yield and N use efficiency in China.

Compared with continuous flooding, the water-saving irrigation can increase water use efficiency. However, the effects of water-saving irrigation on yield and quality in rice paddies have not been clearly defined. The objective of this study was to identify the systematic effects of water-saving irrigation on rice yield and quality through Meta-analysis techniques.

In the present study, a total of 34 studies that adapted a water-saving treatment and continuous flooding as the control involving 263 paired observations were included across this dataset. The meta-analysis was conducted to identify the responses of yield and quality to water-saving irrigation as affected by experimental type, water-saving irrigation type, cropping system, rice type, the period of water-saving irrigation, soil total nitrogen (N), soil texture, N rate, and the number of N application.

Overall, the water-saving irrigation did not significantly affect grain yield and quality relative to continuous flooding. In terms of water-saving irrigation type, the moderate water-saving irrigation increased brown rice rate (+0.9%), milled rice rate (+1.5%), and head milled rice rate (+2.3%), but did not affect grain yield, chalkiness percentage, chalkiness degree, length/width ratio, amylose content, gel consistency, and protein content relative to continuous flooding. However, the severe water-saving irrigation significantly decreased grain yield (-22.1%), brown rice rate (-2.7%), milled rice rate (-2.7%), and head milled rice rate (-3.6%), and increased chalkiness percentage (+28.0%) and chalkiness degree (+46.7%), while no marked differences were observed on length/width ratio, amylose content, gel consistency, and protein content. Furthermore, compared with continuous flooding, the water-saving irrigation reduced protein content (-9.8%) of late rice, but did not affect that of early rice, middle rice, and single rice.

Compared with continuous flooding, the moderate water-saving irrigation could improve rice milling quality, and did not affect grain yield, appearance quality, cooking and eating quality, and nutrition quality. The severe water-saving irrigation significantly reduced rice yield, milling quality, and appearance quality, while no significant effects were found on cooking and eating quality and nutrition quality. The results provided an insight to evaluate the responses of grain yield and quality to water-saving irrigation.

This study aimed to provide the theoretical and technical support for the innovation of green, high-yield, high-quality and high-efficiency unmanned dry direct-seeded (UDDS) cultivation technology of rice.

Medium-maturing medium japonica rice (Nanjing 5718) was selected as the experimental material, with unmanned carpet seedling mechanical transplantated (UCSMT), and conventional carpet seedling mechanical transplantated (CSMT) serving as control methods. A three-year field experiment was conducted to assess the impact of UDDS on growth, yield formation, quality characteristics of rice, and its economic benefits.

(1) Although UDDS was carried out with 2-3 days earlier than the control, it exhibited a full growth cycle that was 12-13 days shorter than those of UCSMT and CSMT, primarily due to the shortened period from sowing to jointing stage. (2) The average yield under UDDS from 2020 to 2022 was 10.5 t·hm^-2, representing a 3.0% increase than that of CSMT, although this difference was not statistically significant. In comparison with UCSMT, UDDS exhibited a significant yield reduction of 5.4%, and this decrease could be attributed to a reduction in the spikelet number per panicle, resulting in fewer total spikelet numbers and a decrease in dry matter accumulation and transport capacity from heading to maturity. (3) Compared with CSMT, UDDS exhibited slightly reduced processing quality, amylose, and protein contents, with no significant differences were observed. However, the significant reductions in chalkiness percentage and degree were noted, while the taste value increased, though not significantly. Compared with UCSMT, UDDS demonstrated a significant decrease in head milled rice rate, chalkiness percentage, degree, and amylose content, and protein content also decreased, though not significantly. Additionally, UDDS exhibited higher RVA peak viscosity and a significant improvement in taste value. (4) Under the UDDS mode, the cost of rice planting decreased, and the net income increased by 1.15 × 10³ yuan·hm^-2 and 0.93 × 10³ yuan·hm^-2, than that under UCSMT and CSMT, respectively.

In the rice-wheat rotation system, UDDS realized the synergy of high yield and income increase, and improved the appearance quality and cooking and eating quality of rice, the UDDS cultivation technology should be optimized in terms of improving the total spikelet number, accumulation and translocation of dry matter during filling stage, thereby getting the goals of high rice yield, great quality, and efficient synergy, simultaneously.