Strategies for indica rice adapted to high-temperature stress in the middle and lower reaches of the Yangtze River

High temperatures caused by climate warming severely affect the grain yield and quality of rice. In this study, the rice cultivars Longliangyou Huazhan (LLYHZ) and Quanliangyou 2118 (QLY2118) were selected as the experimental materials for investigation of an optimal cultivation system under high-temperature treatment. In addition, the heat-resistant cultivar Huanghuazhan (HHZ) and heat-sensitive cultivar Huiliangyou 858 (HLY858) were chosen as the experimental materials to study the effects of exogenous plant growth regulators on heat stress responses under high-temperature treatment. The results showed that mechanical transplanting of carpet seedlings and delayed sowing effectively increased the leaf area index and reduced the canopy temperature of LLYHZ and QLY2118. Furthermore, carpet seedling mechanical transplantation and delayed sowing improved grain yield and quality. Spray application of five plant growth regulators revealed that brassinolide and salicylic acid had the strongest effects on significantly improving antioxidant enzyme activities in the panicle, which would reduce the damage caused by the accumulation of reactive oxygen species and enhance plant tolerance of high-temperature stress. In addition, brassinolide and salicylic acid enhanced the percentage of anther dehiscence and percentage seed set. In this study, a set of simplified eco-friendly cultivation techniques for single-season indica rice adaptation to high-temperature stress was established. These results will be of great importance in alleviating the effects of high-temperature stress on rice production

Border Effect on Ratoon Crop Yield in a Mechanized Rice Ratooning System

Yield loss of ratoon crops caused by the rolling damage to the left stubble from mechanically harvesting main crops has been reported in previous studies. However, limited attention has been paid to identify the effect of the mechanical harvesting of the main crop on the yield of a non-rolled zone (NRZ) of a ratoon crop. A two-year field experiment on ratoon rice with two harvest methods (mechanical harvesting: MEH; manual harvesting: MAH) of a main crop was conducted to identify whether there is a border effect on the yield of the NRZ, and to evaluate whether the border effect will compensate for the yield loss of the ratoon crop. On average, MEH reduced the grain yield of the ratoon crop by 17.6% compared with MAH. The yield of the rolled zone (RZ) in MEH was 66.1–70.3% lower than that of MAH, which was attributed to the lower panicle m−2, grain filling percentage, total dry weight, and harvest index. In contrast, the yield of the NRZ in MEH was 2.7–10.8% higher than that of MAH. The yield differences of the non-rolled single row (R1), side row (R2), and middle row (R3) in the NRZ compared with MAH were 22.9%, 8.5%, and −10.1%, respectively, which were mainly explained by the panicle m−2, spikelets m−2, total dry weight, and regeneration rate. These results suggest that rolling during the mechanical harvesting of the main crop induced a border effect on the yield of the NRZ, which reduced the yield loss of the ratoon crop. The yield gain of the NRZ was attributed to the increased yield of R1 and R2 rather than R3

Effect of Temperature and Radiation on Indica Rice Yield and Quality in Middle Rice Cropping System

Rice (Oryza sativa L.) is cultivated in a wide range of climatic conditions, thereby inducing great variations in the rice growth, yield and quality. However, the comprehensive effects of temperature and solar radiation under different ecological regions on the rice growth, yield and quality are not well understood, especially in a middle rice cropping system. The rice growth, yield- and quality-related traits were investigated under different ecological regions. Among different areas, the days before the heading stage and after the heading stage of six cultivars ranged from 80 to 120 and from 30 to 50. The gaps of the grain yield, head rice rate, chalky grain rate and chalkiness level were about 1.2–52.4%, 1.0–3.0%, 2.7–12.7% and 0.3–4.5%, respectively. This study demonstrated that in these regions, temperature is a limiting factor compared with radiation. Moreover, the rice growth, yield and quality were closely associated with daily air (DT), maximum (MaT), minimum (MiT) and effective accumulated temperatures (EAT). An excellent rice growth, a high grain yield and an excellent quality could be achieved if the EAT was higher than 1592 °C·d and the MiT was lower than 23.1 °C before the heading stage, and if the DT, MiT and MaT were lower than 25.7 °C, 22.0 °C and 30 °C after the heading stage, respectively. These findings served as an important reference for optimizing cultivar selection for a specific area and determining suitable areas for a certain variety

Variations of Rice Yield and Quality in Response to Different Establishment Methods at Farmers’ Field

Mechanized production plays an important role in fulfilling food security demands during the period of labor shortage. Despite its benefits, the mechanical transplanted method (MET) has not been widely adopted due to a lack of awareness. Thus, this study aimed to evaluate the effect of the MET, the manual transplanted method (MAT), and the directed seeded method (DS) on rice yield and quality in farmers’ fields. A two-years field experiment (2016 and 2017) and a one-year survey (2020) were conducted to compare rice yield and quality among the MAT, MET, and DS methods. MET exhibited a higher-yielding population, increased biomass production, enhanced yield, and improved grain quality, compared with MAT. Moreover, japonica rice in MET (MET-JR) produced the maximum yield, 0.6 t hm−2 to 3.1 t hm−2 higher than in other treatments. However, japonica rice showed a poorer appearance quality than indica rice, as well as large panicle size (grains number per panicle ≥ 190); hybrid indica rice (HIR) also presented a high yield with poor appearance quality. These results confirmed that the application of MET could be useful in attaining high panicles per m2, high biomass production, high rice yield, and considerably improved rice quality in farmers’ fields under labor shortage circumstances. Furthermore, it is also imperative to consider balancing the yield and quality of japonica rice and large panicle HIR and employing MET at a broader scale in China, as well as other developing countries having rice–based cropping systems