Rice In South China Research Articles

Yield Difference between Different Cultivation Techniques under Ultrasonic Treatment Driven by Radiation Use Efficiency.

Ultrasonic treatment and optimal cultivation techniques are both conducive to the high yield of super rice in South China. Many previous studies have shown that the increase in intercepted photosynthetically active radiation (IPAR) and radiation use efficiency (RUE) is an important reason for high rice yield. Field experiments were conducted over two years to evaluate the effects of IPAR and RUE on the yield under different treatments (CK: conventional cultivation technique without ultrasonic treatment; T1: conventional cultivation technique with ultrasonic treatment; T2: super rice-specific cultivation technique without ultrasonic treatment and T3: super rice-specific cultivation technique with ultrasonic treatment), with two representative rice varieties, Wufengyou-615 (WFY) and Jingnongsimiao (JNSM) during the late seasons of rice cultivation in South China. The super rice-specific cultivation technique and the ultrasonic treatment could significantly increase the yield, which was significantly (p < 0.01) and positively correlated with panicle number, grain-filling rate, and aboveground total dry weight. The higher grain yield depended more highly on higher RUE in the mid-tillering stage and maturity stage. The results of multiple-regression models also showed that the contributions of IPAR and RUE to yield were significant (p < 0.01). Conclusively, IPAR and RUE contributed a lot to yield progress of super rice in both super rice-specific cultivation techniques with fewer times of topdressing and ultrasonic treatment in South China. It is worth further studying how to reasonably improve the RUE of high-RUE varieties through other means.

Experimental Warming Reduces the Grain Yield and Nitrogen Utilization Efficiency of Double-Cropping indica Rice in South China

The effect of climate warming on rice production in China is profound, yet there has been limited research on how it affects the grain yield, nitrogen (N) uptake, and N utilization efficiency (NUtE) of the double-cropping indica rice in South China. To address this gap, we conducted a free air temperature increase (FATI) experiment in Guangdong province during 2020 and 2021. Our findings revealed that warming led to a significant reduction in grain yield, with early rice (ER) and late rice (LR) experiencing average decreases of 5.2% and 6.3%, respectively, compared to control treatments. This decline was primarily attributed to the reduced grain weight of ER and the fewer spikelet numbers per panicle of LR under warming conditions. Although the dry matter translocation, harvest index, and N translocation efficiency of ER remained unchanged under warming conditions, these of LR decreased by an average of 58.1%, 8.8%, and 22.3%, respectively. Additionally, while warming did not affect the N uptake in ER at maturity, it significantly increased the N uptake in LR by an average of 11.0%. Therefore, under warming conditions, the NUtE of both ER and LR was markedly decreased by 6.9% and 15.5% over the two years. These results indicate that climate warming may have significant negative impacts on the grain yield and the NUtE of indica rice within double-rice cropping systems in South China. Understanding these dynamics is vital for maintaining the stability of rice yields in anticipation of future climate warming.

Post-heading dry-matter transport and nutrient uptake differentiate hybrid and inbred indica rice in the double-cropping system in South China.

Hybrid rice demonstrated superior performance in enhancing yield and efficiency in rice production compared to inbred rice. Nevertheless, the underlying mechanism responsible for the increased yield and efficiency of hybrid rice in South China's double-cropping rice region remains understudied. Field experiments over two consecutive years were conducted. Firstly, yield variations among 20 inbred and 15 hybrid rice cultivars prevalent in South China's double-cropping rice system were examined. Secondly, selecting representative hybrid and inbred rice cultivars with significant yield disparities were carried out on further analyzing dry-matter production, source-sink relationships, and nutrient absorption and utilization in both rice types. Hybrid rice displayed an average grain yield of 8.07 and 7.22t hm-2 in the early and late seasons, respectively, which corresponds to a 12.29% and 13.75% increase over inbred rice with statistically significant differences. In comparison to inbred rice, hybrid rice exhibited enhanced nitrogen concentration in leaves at the heading stage (15.48-16.20%), post-heading dry matter accumulation (52.62-73.21%), post-heading dry matter conversion rate (29.23-34.12%), and harvest index (17.31-18.37%). Additionally, grain nitrogen and phosphorus uptake in hybrid rice increased by 11.88-22.50% and 16.38-19.90%. Hybrid rice mainly improved post-heading nitrogen and phosphorus uptake and transport, while not total nitrogen and phosphorus uptake. Internal nitrogen and phosphorus use efficiency enhanced by 9.83%-14.31% and 10.15%-13.66%, respectively. Post-heading dry matter accumulation, harvest index, grain nitrogen and phosphorus uptake, and internal nitrogen and phosphorus use efficiency exhibited significant positive linear correlations with grain yield. The period from heading to maturity is critical for enhancing hybrid rice yield and efficiency. Improving photosynthetic capacity during this period and promoting nutrient transport to grains serve as crucial pathways for increasing grain yield and efficiency. This study is of great significance for further improvement grain yield and breeding rice cultivars with high-yield and high nutrients use efficiency for South China's double-cropped rice system.

Assessing the yield difference of double-cropping rice in South China driven by radiation use efficiency

Double-cropping rice in South China continues to break the total yield record, but the yield potential of single-cropping rice is not being realized. Radiation use efficiency (RUE) has been singled out as an important determinant of grain yield in many cereal species. However, there is no information on whether the yield gaps in double-cropping rice involve differences in RUE. Field experiments were performed over two years to evaluate the effects of intercepted radiation (IP) and RUE on the above-ground biomass production, crop growth rate (CGR), and harvest index (HI), in four representative rice varieties, i.e., Xiangyaxiangzhan (XYXZ), Meixiangzhan 2 (MXZ2), Nanjingxiangzhan (NJXZ), and Ruanhuayoujinsi (RHYJS), during the early and late seasons of rice cultivation in South China. The results revealed that grain yield in the early season was 8.2% higher than in the late season. The yield advantage in the early season was primarily due to higher spikelets per panicle and above-ground biomass resulting from a higher RUE. The spikelets per panicle in the early season were 6.5, 8.3, 6.9, and 8.5% higher in XYXZ, MXZ2, NJXZ, and RHYJS, respectively, than in the late season. The higher early season grain yield was more closely related to RUE in the middle tillering stage (R2=0.34), panicle initiation (R2=0.16), and maturation stage (R2=0.28), and the intercepted photosynthetically active radiation (IPAR) in the maturation stage (R2=0.28), while the late season grain yield was more dependent on IPAR in the middle tillering stage (R2=0.31) and IPAR at panicle initiation (R2=0.23). The results of this study conclusively show that higher RUE contributes to the yield progress of early season rice, while the yield improvement of late season rice is attributed to higher radiation during the early reproductive stage. Rationally allocating the RUE of double-cropping rice with high RUE varieties or adjustments of the sowing period merits further study.

Changes in planting methods will change the potential distribution of rice in South China under climate warming

Evaluation of and adaptation to climate warming have become major challenges, given the profound impacts of climate warming and technical advances in rice cropping systems. However, the dual influences of climate warming and planting methods on rice production remain unclear. Here, we developed a methodological framework based on temperature-based rice growth season determination and GIS spatial analysis to quantify the effect of climate warming and improvements in planting methods (transplanting to direct seeding) on the potential distribution of rice cropping systems in South China from 1960 to 2017. The accumulated temperature during the potential growing period of rice increased significantly, and the safe season for rice production extended substantially, which resulted in northward and westward expansions of the planting boundaries for rice cropping systems over the past few decades. Significant changes in planting boundaries and potential planting areas were observed for early maturity double rice (DR_Early) because of climate warming. Since transplanting requires less thermal time compared to direct seeding in the main field, the planting boundaries of DR would shift southward because of planting methods change. The planting boundaries of DR_Early and medium maturity double rice (DR_Medium) changed significantly, moving on average 267 and 159 km southward, resulting in a 13.3% decrease in the study area. The dual analysis showed that the change in planting methods would shift the rice planting boundaries southward, offset the impact of climate warming, and reduce the rice planting areas by 4.0%. Therefore, improvements in planting methods should be considered when evaluating the effects of climate warming on agricultural systems. This research provides new insights that could be used to optimize rice cropping systems, improve the utilization efficiency of thermal resources and adapt to climate warming.

Artificially Selected Grain Shape Gene Combinations in Guangdong Simiao Varieties of Rice (Oryza sativa L.)

BackgroundGrain shape is a key trait in rice breeding. Although many QTLs and genes of grain shape have been identified, how different combinations of alleles of these genes affect grain shape is largely unknown. It is important to understand the effects of grain shape gene combinations for breeding by design. In the present study, we performed genetic dissection of the grain shapes in Guangdong Simiao varieties, a popular kind of rice in South China, to identify the effective alleles and their combination for breeding.ResultsWe selected two hundred nineteen indica accessions with diverse grain shapes and fifty-two Guangdong Simiao varieties with long and slender grain shapes for genome-wide selection analysis. The results showed that four (GS3, GS5, GW5 and GL7) of the twenty grain shape genes fall into the regions selected for in Guangdong Simiao varieties. Allele analysis and frequency distribution of these four genes showed that GS3allele3 and GW5allele2 accounted for 96.2%, and GL7allele2 and GS5allele2 accounted for 76.9% and 74.5% of the Simiao varieties, respectively. Further analysis of the allelic combinations showed that 30 allelic combinations were identified in the whole panel, with 28 allelic combinations found in the international indica accessions and 6 allelic combinations found in Guangdong Simiao varieties. There were mainly three combinations (combinations 17, 18 and 19) in the Guangdong Simiao varieties, with combination 19 (GS3allele3 + GW5allele2 + GL7allele2 + GS5allele2) having the highest percentage (51.9%). All three combinations carried GS3allele3 + GW5allele2, while combinations 17 (GL7allele1) and 19 (GL7allele2) showed significant differences in both grain length and length/width ratio due to differences in GL7 alleles. Pedigree analysis of Guang8B, the maintainer of the first released Simiao male sterile line Guang8A, showed that the parent lines and Guang8B carried GS3allele3 + GW5allele2 + GS5allele2, while the GL7 allele differed, resulting in significant differences in grain size.ConclusionThe results suggest that specific alleles of GS3, GS5, GW5 and GL7 are the key grain shape genes used in the Guangdong Simiao varieties and selected for grain shape improvement. Combination 19 is the predominant allelic combination in the Guangdong Simiao varieties. Our current study is the first to dissect the genetics of grain shape in Guangdong Simiao varieties, and the results will facilitate molecular breeding of Guangdong Simiao varieties.

Continuous Monitoring Analysis of Rice Quality in Southern China Based on Random Forest

Rice quality has received more attention, so monitoring and analysis are of great significance to rice quality. General quality indexes of rice in southern China from 2011 to 2020 were determined, including processing quality (brown rice yield, milled rice recovery, head rice yield), appearance quality (grain length, length-width ratio, chalky rice percentage, chalkiness degree, transparency), and cooking quality (alkali spreading value, gel consistency, amylose). Principal component analysis was used to distinguish the regional quality of southern rice. The results showed that amylose and chalkiness were the main contributory quality indexes of rice in South China, the upper reaches of the Yangtze River, and the middle and lower reaches of the Yangtze River. In the past decade, the total high-quality rate of rice in the South has improved. The random forest was used to determine the important influence index of rice quality. The results showed that chalkiness degree, alkali spreading value, and gel consistency were important indexes affecting the quality of southern rice, and random forest could be used as an effective approach for continuous monitoring and analysis of rice quality.

Effects of Early Rice Straw Returning with Reducing Potassium Fertilizer on Late Rice Yield and Soil Fertility

Rice straw is an important organic fertilizer in the region for double-cropping rice in South China. To reveal the effects of early rice returning with reducing potassium fertilizer on the yield of late rice and soil fertility, field experiments were carried out in Baiyun and Huiyang district in Guangdong province. The biomass, K content, and yield of late rice and the soil fertility properties, such as soil available potassium, soil organic carbon, bacterial diversity, and bacterial community structure were analyzed under three treatments (CK, conventional fertilization; RS, straw returning with conventional fertilization; RS-K, straw returning with reducing 20% potassium fertilizer). The results showed no significant differences in the biomass and yield of late rice between the RS-K treatment and CK treatment. Compared with that in CK, the RS treatment significantly increased the K contents of rice by 3.97% (Baiyun) and 6.91% (Huiyang). The K contents of late rice under the RS-K treatment were significantly lower than that under the CK treatment during the early growth period in rice, but there was no significant difference between them during the late growth period. Compared with that in CK, the soil available K in the RS treatment increased by 13.90% (Baiyun) and 21.67% (Huiyang) (P<0.05), and the soil available K in the RS-K treatment also increased by 3.56% (Baiyun) and 4.23% (Huiyang). Compared with that in the CK treatment, the soil dissolved organic carbon increased significantly in the RS and RS-K treatments (P<0.05). Compared with that in CK, the straw returning treatments (RS and RS-K) significantly improved the Chao1 and Shannon indexes of soil bacteria (P<0.05). Straw returning treatments (RS and RS-K) increased the relative abundance of Proteobacteria, Actinobacteria, and Nitrospirae compared with that in CK, whereas they decreased the relative abundance of Acidobacteria, Bacteroidetes, and Firmicutes. Redundancy analysis showed that the soil bacterial community was mainly influenced by soil organic carbon, dissolved organic carbon, microbial biomass carbon, available P, and available K. In summary, early rice returning could increase soil available K and K content in late rice. Early rice straw returning with reducing potassium fertilizer had no negative impacts on the growth and yield of late rice and could also improve soil organic carbon and the diversity of soil bacteria. Therefore, early rice straw returning with reducing potassium fertilizer can guarantee the grain yield of late rice and improve soil fertility.

Effects of Different Concentrations of Micro-Nano Bubbles on Grain Yield and Nitrogen Absorption and Utilization of Double Cropping Rice in South China

Micro-nano bubble (MNB) irrigation can effectively improve the hypoxia stress caused by conventional irrigation and shows great potential in plant development, yield improvement, and saving of water and fertilizer, and has been recognized as a new and high-efficiency technology in crop planting. However, former research on MNB concentration had no clear segmentation, and other MNB concentrations can achieve better or worse effects. This remains to be further explored in order to explore the optimal concentration of MNBs for the yield and nitrogen absorption and utilization of the double cropping rice. With early rice Ganxin203 and late rice WufengyouT025 as the experimental cultivars, the effects of MNBs on growth, yield, and nitrogen absorption and utilization of the potted double cropping rice were analyzed by setting three concentrations of MNBs (LM, low concentration; MM, middle concentration; HM, high concentration), compared with the ordinary running water (CK). Compared with CK, grain yield of the early rice under the MNB treatment increased by 4.84~10.95% and the late rice increased by 6.10~14.31%. It was found that the higher the concentration of the MNBs, the higher the yield of the rice. This is due to that the MNBs improved the tiller-bearing rate, increased the SPAD and Pn values of the flag leaves in the whole growth period, slowed down the drop of the leaf SPAD and Pn from heading stage to maturity, increased the number of the adventitious roots, improved the α-NA oxidation of the root, and simultaneously promoted the nitrogen accumulation, absorption, and utilization. The HM treatment obtained the best benefits, and the effect of the MNBs on the late rice was better than the early rice.

Unveiling a Novel Source of Resistance to Bacterial Blight in Medicinal Wild Rice, Oryza officinalis.

Bacterial blight (BB) caused by Xanthomonas oryzae pv. oryzae (Xoo) is among the oldest known bacterial diseases found for rice in Asia. It is the most serious bacterial disease in many rice growing regions of the world. A total of 47 resistance (R) genes (Xa1 to Xa47) have been identified. Nonetheless, these R genes could possibly be defeated to lose their qualitative nature and express intermediate phenotypes. The identification of sources of novel genetic loci regulating host plant resistance is crucial to develop an efficient control strategy. Wild ancestors of cultivated rice are a natural genetic resource contain a large number of excellent genes. Medicinal wild rice (Oryza officinalis) belongs to the CC genome and is a well-known wild rice in south China. In this study, O. officinalis was crossed with cultivated rice HY-8 and their hybrids were screened for BB resistance genes deployed through natural selection in wild rice germplasm. The molecular markers linked to R genes for BB were used to screen the genomic regions in wild parents and their recombinants. The gene coding and promoter regions of major R genes were inconsistently found in O. officinalis and its progenies. Oryza officinalis showed resistance to all thirty inoculated Xoo strains with non-availability of various known R genes. The results indicated the presence of novel genomic regions for BB resistance in O. officinalis. The present study not only provides a reference to investigate medicinal rice for R gene(s) identification against BB but also identified it as a new breeding material for BB resistance.

Effects of Different Irrigation Management on the Textural Properties of Double-Cropping Late Indica Rice in South China

In order to investigate the effects of different irrigation management on the textural properties of two different double-cropping late <i>Indica</i> rice, the effects of three irrigation management including conventional irrigation (CK), constant irrigation (CI) and alternate wetting and drying (AWD) on textural properties has been researched under field conditions of two years. The results indicated that the firmness, cohesiveness and chewiness were decreased under AWD treatment, and the stickiness was increased compared with CK, while the textural properties under CI treatment showed the opposite trend with AWD treatment. Additionally, AWD treatment signifi- cantly improved the springiness of TY871 compared with CK and CI treatment, but had no significant effect in RYHZ, suggesting improvement of the cooking and eating quality of TY871 under AWD treatment. Correlation analysis showed that the chewiness was positively correlated with the firmness and cohesiveness, and the cohesiveness was positively correlated with the firmness. AWD could promote the textural properties of high-quality late <i>Indica</i> rice in South China whereas CI treatment has shown the disadvantage of the textural properties, which will provide useful information for the improvement of cooking and eating quality of rice.

The story of grain self‐sufficiency: China's food security and food for thought

AbstractGrain self‐sufficiency (GSS) is gaining increased attention throughout the world, and this holds particularly true for China. This study, therefore, investigated spatial and temporal patterns of GSS at the county level in China from 1980s to the 2010s; then explored future GSS changes in the 2035s according to China's 2016 dietary nutrition guidelines, under the circumstances of maximum, average and minimum grain yield increase rate; and finally discussed the ability of a county to purchase grain to meet its demands. The results indicate that the number of counties with self‐insufficiency for total grain and ration decreased, and the amount of counties with high‐level self‐sufficiency for total grain and ration increased. However, the change in the number of counties with feed grain self‐insufficiency and high‐level self‐sufficiency is opposite to that of ration and total grain. Eastern China was characterised by high GSS of total grain, ration and feed grain. As for different kinds of grain, high level of GSS distributed in main grain producing areas, such as rice in south China, wheat in western China and Huang Huai Hai Plain, maize in north and northwest China and soybean in northeast China. Qinghai‐Tibet plateau has undergone poor food security in the last 30 years. In the 2035s, China's total GSS level and ration self‐sufficiency level will be improved under the maximum and average grain yield increase rate, whilst for feed grain, the self‐sufficiency level will be improved only under the maximum grain yield increase rate. The Qinghai‐Tibet plateau has always been a fragile area of food security. This study plays the vital function in understanding China's food security and contributes to the optimisation of agricultural production as well as the utilisation of both internal and external markets.

Innovative furrow ridging fertilization under a mechanical direct seeding system improves the grain yield and lodging resistance of early indica rice in South China

• Furrow ridging fertilization increased grain yield of direct-seeded early indica rice in South China. • Higher yield in furrow ridging fertilization was attributed to high panicle and biomass production. • Furrow ridging fertilization improved the stem lodging resistance compared with surface fertilization and whole-layer fertilization. • Furrow ridging fertilization had the significantly highest lignin content among the fertilization methods. Precision hill-drop direct seeding via mechanical drilling is a novel planting pattern that provides benefits such as high grain yields and lodging resistance in direct-seeded rice in South China, however, the effects of different fertilization methods on yield performance and lodging resistance capacity under mechanical direct seeding systems are still unclear. Hence, a field experiment was conducted over two years with two early indica cultivars to determine the grain yield formation and lodging characteristic of the rice plants under three fertilization methods, including furrow ridging fertilization (FRF), surface fertilization (SF), and whole-layer fertilization (WLF). We found that FRF significantly increased the grain yields of the two cultivars by 6.04 %–28.25 % compared with SF and WLF; this result was attributed to the high panicle and biomass production. FRF also significantly improved the seedling emergence rate of the early indica rice cultivars and increased the aboveground total dry weight and harvest index. In addition, compared with SF and WLF, FRF significantly enhanced the stem lodging resistance of direct-seeded rice cultivars and reduced the lodging index, especially at the third internode. The physical parameters of the stem, including the internode length, thickness and wall thickness, dry weight of internode, and lignin content of the test internodes, improved under FRF due to the high associated breaking-resistance strength and lodging index. These results indicate that furrow ridging fertilization was beneficial for increasing the grain yield and lodging resistance of direct-seeded early indica rice.

Effects of Different Fertilization Methods on Grain Yield, Photosynthetic Characteristics and Nitrogen Synthetase Enzymatic Activities of Direct-seeded Rice in South China

Effects of Different Fertilization Methods on Grain Yield, Photosynthetic Characteristics and Nitrogen Synthetase Enzymatic Activities of Direct-seeded Rice in South China

Effects of different mechanical direct seeding methods on grain yield and lodging resistance of early indica rice in South China

Direct seeding of rice has become a main planting method due to the low labor input and high economic benefit in South China. Dry direct seeding (DDS) has been widely used for single-season rice planting establishment. However, few studies have examined the performance of early-season indica rice under mechanical dry direct seeding. A two-year field experiment was conducted with two indica rice cultivars (i.e., Zhongjiazao 17 and Zhuliangyou 819) to study lodging characteristics and grain yield formation under DDS, flooded direct seeding (FDS) and wet direct seeding (WDS) patterns. The results showed that the annual grain yield in DDS was higher by 14.42–26.34% for cultivar ZLY819 and 6.64–24.58% for cultivar ZJZ17 than in WDS and FDS, respectively, and these increases were mainly attributed to the improvement of the panicles. The DDS pattern significantly increased the seedling emergence rate of early indica rice cultivars, and increased total dry weight and crop growth rate. Meanwhile, shorter basal internodes, better stem diameter and stem wall thickness and lower lodging index were found in DDS in contrast to FDS and WDS. In particular, DDS improved the stem lodging resistance. Our results suggested that the appropriate direct seeding method was beneficial for improving the grain yield and lodging resistance of early indica rice.

Productivity and profitability of mechanized deep nitrogen fertilization in mechanical pot‐seedling transplanting rice in South China

AbstractThe deep nitrogen (N) fertilization coupled with mechanical pot‐seedling transplanting rice (DNF‐MPT) is an effective alternative to traditional transplanted rice (Oryza sativa L.) with broadcasting fertilizer; however, little is known about its effects on grain yield, nutrient accumulation, and economic profitability. In present study, a 2‐yr field experiment was conducted in early seasons (Mar.–July) of 2019 and 2020. All seedlings were transplanted by DNF‐MPT, whereas four treatments were designed as mechanized deep placement of all fertilizers as basal fertilizer (MD); mechanized deep placement of 70% basal fertilizer and 30% broadcasting fertilizers at panicle initiation (MDB); manual broadcasting of 40, 30, and 30% fertilizers at the transplanting, tillering, and panicle initiation stages, respectively (MB); and no fertilizer (CK). The results indicated that the MD treatment substantially improved the grain yield by 33.48–36.35%, total N accumulation by 26.38–44.15%, total phosphorus (P) accumulation by 28.72–30.23%, and total potassium (K) accumulation by 25.61–37.33% compared with MB. Deep placement of N fertilization treatments, that is, MD and MDB, remarkably promoted root morphological indexes including total root volume, total root length, and root superficial area. Furthermore, nitrate reductase, glutamine synthetase activities, and total chlorophyll content of leaves were also enhanced under deep placement of N fertilizer. Overall, the MD treatment had the highest benefit/cost ratio due to high gross returns and low input costs. Therefore, deep placement of N fertilizer coupled with mechanical pot‐seedling transplanting rice could be better alternative to conventional rice production system with more economic benefits.

Potential applicability of a cyanobacterium as a biofertilizer and biopesticide in rice fields

This study aimed to evaluate the potential applicability of Anabaena variabilis SCAU30 as a biofertilizer and biopesticide in rice fields. The effects of A. variabilis SCAU30 inoculation on disease severity, plant growth, rice yield, and soil nutrients were investigated by microchamber, micro-area, and field experiments. The nitrogen fixation ability was estimated by acetylene reduction activity. Hormones were analyzed using liquid chromatography-tandem mass spectrometry. In microchamber experiments, the control efficacies of A. variabilis SCAU30 against rice sheath blight and bacterial blight were 62.3 ± 8.9% and 45.3 ± 5.6%, respectively. The cell extracts of A. variabilis SCAU30 exhibited high antagonistic effects on corresponding pathogens, whereas volatile compounds only showed inhibition on Xanthomonas oryzae. The results of pond experiments showed that inoculation with A. variabilis SCAU30 could promote the growth of rice plants, increase yield, control diseases, and decrease chemical nitrogen fertilizer input. Moreover, in field experiments, the combined treatment of A. variabilis SCAU30 and 50% topdressing fertilizer increased rice yields by 13.9%–22% compared with the conventional fertilizer treatment. This potentially represents economic gains of 26,753 ~ 38,987 Chinese Yuan ha−1 season−1 if sold as a green food. The present study suggests that A. variabilis SCAU30 may act as a fertilizer and pesticide in developing green rice in South China.

Improving grain yield, nitrogen use efficiency and radiation use efficiency by dense planting, with delayed and reduced nitrogen application, in double cropping rice in South China

Improving both grain yield and resource use efficiencies simultaneously is a major challenge in rice production. However, few studies have focused on integrating dense planting with delayed and reduced nitrogen application to enhance grain yield, nitrogen use efficiency (NUE) and radiation use efficiency (RUE) in rice (Oryza sativa L.) in the double rice cropping system in South China. A high-yielding indica hybrid rice cultivar (Yliangyou 143) was grown in field experiments in Guangxi, South China, with three cultivation managements: farmers’ practice (FP), dense planting with equal N input and delayed N application (DPEN) and dense planting with reduced N input and delayed N application (DPRN). The grain yields of DPRN reached 10.6 and 9.78 t ha–1 in the early and late cropping seasons, respectively, which were significantly higher than the corresponding yields of FP by 23.9–29.9%. The grain yields in DPEN and DPRN were comparable. NUE in DPRN reached 65.2–72.9 kg kg–1, which was 61.2–74.1% higher than that in FP and 24.6–30.2% higher than that in DPEN. RUE in DPRN achieved 1.60–1.80 g MJ–1, which was 28.6–37.9% higher than that in FP. The productive tiller percentage in DPRN was 7.9–36.2% higher than that in DPEN. Increases in crop growth rate, leaf area duration, N uptake from panicle initiation to heading and enhancement of the apparent transformation ratio of dry weight from stems and leaf sheaths to panicles all contributed to higher grain yield and higher resource use efficiencies in DPRN. Correlation analysis revealed that the agronomic and physiological traits mentioned above were significantly and positively correlated with grain yield. Comparison trials carried out in Guangdong in 2018 and 2019 also showed that DPRN performed better than DPEN. We conclude that DPRN is a feasible approach for simultaneously increasing grain yield, NUE and RUE in the double rice cropping system in South China.

Effects of Nitrogen Forms and Application Rates on Nitrogen Uptake, Photosynthetic Characteristics and Yield of Double-Cropping Rice in South China

Nitrogen is an important element that affects the growth and yield of rice obviously. To explore the effects of nitrogen (N) on the growth of double-cropping rice, four consecutive trials were conducted in South China Agricultural University. Four N forms and five N application rates were set up. Rice N uptake, leaf anatomic structure, leaf fluorescence parameters and yield were studied. The results showed that rice leaf SPAD value and N content with urea treatment were the highest among 4 N forms at the heading and flowering stage. The order of rice yield and N use efficiency treated with different N forms were urea &gt; ammonium sulfate &gt; ammonium nitrate &gt; sodium nitrate. The N application rate test showed that photochemical quantum efficiency and chemical quenching coefficient of rice leaves showed an inverted-V-type changing tendency with the highest value at 180 kg/hm2 N treatment. Treatment with less than 180 kg/hm2 N decreased the area and perimeter of small vascular bundles of the lateral leaves. Yield of early rice and later rice with 180 kg/hm2 urea treatment was 17.42 to 33.28% and 6.17 to 21.28% higher than those of other N levels, respectively. The above results suggested that 180 kg/hm2 of urea N are suitable and recommended for double-cropping rice planting in South China.

Modeling the Impact of Atmospheric Warming on Staple Crop Growth in China in the 1960s and 2000s

Responses of crop growth to climate warming are fundamental to future food security. The response of crops to climate change may be subtly different at their growing stages. Close insights into the differentiated stage-dependent responses of crops are significantly important in making adaptive adjustments of crops’ phenological optimization and cultivar improvement in diverse cropping systems. Using the Agro-C model, we studied the influence of past climate warming on crops in typical cropping systems in China. The results showed that while the temperature had increased distinctly from the 1960s to 2000s, the temperature frequency distributions in the growth season of crops moved to the high-temperature direction. The low temperature days during the crop growth periods that suppress crop growth decreased in the winter wheat area in North and East China, rice and maize areas in Northeast China, and the optimum temperature days increased significantly. As a result, the above ground biomass (AGB) of rice and maize in Northeast China and winter wheat in North and East China increased distinctly, while that of rice in South China had no significant change. A comparison of the key growth periods before and after heading (silking) showed that the warming before heading (silking) made a great contribution to the increase in the AGB, especially for winter wheat.