Rice Ratooning Research Articles

On-farm comparison in grain quality between main and ratoon crops of ratoon rice in Hubei Province, Central China.

While ratoon rice has been increasingly practiced by farmers recently in China, on-farm performance in grain quality of main and ratoon crops in the mechanized rice ratooning system is less studied and remains poorly understood. Therefore, a multi-location on-farm survey was conducted to collect rice grain samples from farmers' fields to determine grain quality of main and ratoon crops of ratoon rice at 12 locations across Hubei Province, central China, in 2016. On average, milled and head rice percentage in the ratoon crop was 70.2% and 65.7%, which was significantly higher than in the main crop, whereas chalky grain percentage and grain chalkiness in ratoon crop (10.1% and 2.8%, respectively) were significantly lower than those in the main crop (36.6% and 14.2%, respectively). The differences in these quality traits between the two crops were consistent at all locations. Averaged across 12 locations, scores of translucency and gel consistency were significantly lower but amylose content and alkali spreading value were significantly higher in the ratoon crop than in the main crop, with the difference between the two crops varying in gel consistency by location. Overall, grain quality, especially milling and appearance of the ratoon crop, was superior to the main crop in the mechanized rice ratooning system. As a result, this study emphasizes the potential role of the rice ratooning system in other regions with a similar biophysical background producing high-quality rice. © 2022 Society of Chemical Industry.

Stubble height affects the grain yield of ratoon rice under rainfed conditions

Rice ratooning system is becoming an important rice planting system to ensure food security in China, and improvement of grain yield and yield stability has always been the primary goal in the development of ratoon rice. Here, field experiments were conducted in central China from 2020 to 2021 to explore the effects of water management (flooded vs rainfed) and stubble height (45, 20 and 0 cm; abbreviated as SH45, SH20 and SH0, respectively) on the yield performance of ratoon rice. The results demonstrated that water management during the main season had no effect on the grain yield of either main crop (MC) and ratoon crop (RC). However, rainfed treatment during the ratoon season significantly decreased the RC yield by 14.4% and 9.2% in 2020 and 2021, respectively. The reduction of stubble height prolonged the growth duration, decreased the panicle number, and increased the spikelets panicle−1, total spikelets and leaf area index. Compared with SH45, SH20 and SH0 increased the RC yield by 20.7% and 6.8% in 2020, respectively, whereas no significant difference in RC yield was observed among different stubble heights in 2021. Moreover, the grain yield of RC at low stubble heights was more susceptible to rainfed treatment. Specifically, rainfed treatment averagely decreased the RC yield by 4.9%, 12.7% and 17.2% at SH45, SH20 and SH0, respectively. The grain yield of RC was positively correlated with the panicle number, total spikelets and biomass accumulation, while low stubble heights, particularly SH20, had a greater magnitude of slope. Furthermore, panicle number exhibited stronger correlations with spikelets panicle−1 and biomass accumulation at low stubble heights. Overall, our results suggest that more attention should be paid to water management in the ratoon season, and increasing the panicle number is crucial to the improvement of yield and yield stability of RC at low stubble heights.

Metabolomic analysis reveals differential metabolites and pathways involved in grain chalkiness improvement under rice ratooning

Metabolomic approaches provide new insights into studying changes in yield traits and grain chalkiness under a ratoon cropping system. In this study, when rice plants were grown as ratooning season rice, seed setting percentage, chalky grain percentage and chalkiness degree were highly improved, as compared to their counterparts in main-cropping season rice and late-cropping season rice. Furthermore, such improvements were proven to be associated with a shift in the metabolomic composition of the grain, especially regarding variations in sugar components in carbohydrate metabolism. Moreover, rice ratooning specifically increased the total ascorbate content combined with an enhancement of oxidative stress tolerance in grains. Finally, a potential mechanism was revealed: rice ratooning caused compositional changes in sugar metabolism in addition to promoting starch synthesis during the early stage of grain filling, ultimately improving the level of grain chalkiness.

Nonstructural carbohydrate content in the stubble per unit area regulates grain yield of the second crop in rice ratooning

AbstractRice (Oryza sativa L.) ratooning has attracted attention due to its higher yield potential. In the present study, a field experiment on rice ratooning using two rice genotypes, near isogenic line (NIL)‐GN1ATakanari and Koshihikari, was conducted in 2019 and 2020 in southwestern Japan to obtain direct evidence for the role of stubble nonstructural carbohydrate (NSC) concentration and/or content per unit area on grain yield of the second crop and to determine the effectiveness of a gene producing more spikelets. NIL‐GN1ATakanari is a near isogenic line carrying an allele of GN1A, which is a gene regulating the number of spikelets per unit area derived from an indica cultivar Takanari in the genetic background of a japonica cultivar Koshihikari, and it can produce more spikelets than Koshihikari. NIL‐GN1ATakanari did not produce a higher grain yield of the first crop than Koshihikari in both years because NIL‐GN1ATakanari had more spikelets m−2 but fewer filled spikelets and a lower grain weight. NIL‐GN1ATakanari produced a lower grain yield of the second crop than Koshihikari because NIL‐GN1ATakanari had fewer spikelets m−2 due to the fewer panicles. Also, NIL‐GN1ATakanari had a lower NSC content than Koshihikari due to the lower leaf sheath plus stem weight in the stubble in 2019. Thus, the lower grain yield in the second crop of NIL‐GN1ATakanari may result from the lower NSC content in the stubble. Additionally, the ability to produce more spikelets per unit area of NIL‐GN1ATakanari was not demonstrated in ratoon crop under the condition of low NSC content in the stubble.

Development of a new index for automated mapping of ratoon rice areas using time-series normalized difference vegetation index imagery

Over recent decades, the global demand for food has continued to grow, owing to population growth and the loss of arable land. Rice ratooning offers new opportunities for increasing rice production and has received renewed interest because of the minimal additional labor input required for its adoption. Regular, regional-scale monitoring of the spatial patterns of both traditional and ratoon rice cropping systems provides essential information for agricultural resource management and food security studies. However, the similar phenological characteristics of traditional double rice and ratoon rice cropping systems make it challenging to accurately classify these cropping practices based on satellite observations alone. In this study, we first proposed an improved phenology-based rice cropping area detection algorithm using moderate resolution imaging spectroradiometer (MODIS) normalized difference vegetation index (NDVI) imagery. A new index, ratoon rice index, was then developed to automatically delineate ratoon rice cropping areas with the aid of a base map of rice in Hubei Province, China. The accuracy assessment using ground truth data showed that our approach could map both traditional and ratoon rice cropping areas with high user accuracy (91.25% and 91.43%, respectively). The MODIS-retrieved rice cropping areas were validated using annual agricultural census data, and coefficient of determination ( R 2 ) values of 0.60 and 0.41 were recorded for traditional and ratoon rice cropping systems, respectively. The total area of ratoon rice was estimated to be 1 283.6 km 2 , 5.0% of the total rice cropping area, in Hubei Province in 2016. These demonstrated the feasibility of extracting the spatial patterns of both traditional and ratoon rice cropping systems solely from time-series NDVI and field survey data and strides made in facilitating the timely and routine monitoring of traditional and ratoon rice distribution at subnational level. Given sufficient historical satellite and phenology records, the proposed algorithm had the potential to enhance rice cropping area mapping efforts across a broad temporal scale ( e.g ., from the 1980s to the present).

Field greenhouse gas emission characteristics and carbon footprint of ratoon rice

It is of great significance to understand the effects of different rice cultivation methods in southeast China on greenhouse gas emission characteristics and carbon footprint of paddy fields during rice cultivation for rice sustainable production. In this study, the popular conventional rice 'Jiafuzhan' and hybrid rice 'Yongyou 2640' were used as materials to establish four rice cultivation patterns suitable for different ecological types in Fujian Province: 1) double-cropping system, early rice and late rice with Jiafuzhan (D-J); 2) early maturing ratooning system, first season rice and ratooning season rice with Jiafuzhan (R-J); 3) middle-maturing ratooning system, first season rice and ratooning season with Yongyou 2640 (R-Y); and 4) single cropping system with Yongyou 2640 (S-Y), which should be synchronized in heading time with the counterpart (the ratooning season rice). Greenhouse gas emissions from paddy soil were measured by the closed static black box observation method and the gas chromatography method, respectively. The total direct and indirect greenhouse gas emissions (carbon footprints) from different rice farming patterns were evaluated by using the life cycle analysis. The results showed that greenhouse gas emissions in different rice cropping systems were lower in the early growth stage, then decreased after reaching the peak at the booting stage, demonstrating a double peak curve in the whole growth stage, in which the first peak was higher in early season or first season than the second peak in the late season or ratooning season in the cropping patterns. Moreover, the total greenhouse gas emissions were significantly different among cropping systems. The global warming potential (GWP) of different cropping patterns was in order of R-Y>D-J>S-Y>R-J, while the annual greenhouse gas emission intensity (GHGI) was D-J>S-Y>R-Y>R-J. GWP and GHGI of the ratooning system decreased by 26.1% and 14.1%, respectively, compared with those of the double-cropping system. The same pattern was observed in the ratooning rice of Yongyou 2640, which were decreased by 74.3% and 56.7%, respectively, compared with the counterpart, Yongyou 2640 in a single-cropping system synchronized heading. Carbon footprint of rice per unit yield ranged from 0.38-1.08 kg CO2-eq.·kg-1 under the different cropping systems, of which the carbon footprint of rice per unit yield was the highest under the double cropping system compared with that under other cropping systems. The reverse was true in the case of carbon footprint of rice per unit yield under the ratooning system with Yongyou 2640. Additionally, the main source of carbon footprint of different rice cropping patterns was CH4, contributing 44.2%-71.5%, suggesting that rice ratooning system could significantly reduce global warming potential and carbon emission intensity of rice in comparison with other cropping patterns. Therefore, it is key to select rice varieties with high yield and low carbon emission and to establish the supporting scientific cultivation techniques for effective reduction of CH4 emission and carbon footprint of paddy fields and promotion of ratooning rice production.

再生稻机收碾压稻茬扶正机设计与试验

For rice ratooning, the lateral bud germination of the rice stubble after the first harvesting can be used to continue the next growing season, but the first harvesting machinery will crush and damage the rice stubble, resulting in the reduction of yield in the ratooning season. Lifting the rolled stubble can reduce this loss, and thus a double-chain finger grain lifter was designed in this study. Then, a kinematic model and motion trajectory curve of the grain lifter was established. The influence law of the chain speed, chain spacing and the number of fingers of the rear lifting chain was determined. Furthermore, taking into account the success rate and the rate of secondary damage of the lifting, a full-factor bench test was performed. The best operating characteristics of the grain lifter are: chain speed of 345 r/min, adjacent chain spacing of 300 mm, and the number of gears and fingers on the rear lifting chain of 3. The success rate and the secondary damage rate of the lifting is 90.05% and 1.72%, respectively. A field verification test was conducted, with an average success rate of 55%. The results of this study can provide valuable reference for the lifting technology of rolled rice stubble and promote the whole mechanized production of ratoon rice.

Genetic Dissection of Rice Ratooning Ability Using an Introgression Line Population and Substitution Mapping of a Pleiotropic Quantitative Trait Locus qRA5.

Ratooning ability is a key factor that influences ratoon rice yield, in the area where light and temperature are not enough for second season rice. In the present study, an introgression line population derived from Minghui 63 as the recipient parent and 02428 as the donor parent was developed, and a high-density bin map containing 4568 bins was constructed. Nine ratooning-ability-related traits were measured, including maximum tiller number, panicle number, and grain yield per plant in the first season and ratoon season, as well as three secondary traits, maximum tiller number ratio, panicle number ratio, and grain yield ratio. A total of 22 main-effect QTLs were identified and explained for 3.26–18.63% of the phenotypic variations in the introgression line population. Three genomic regions, including 14.12–14.65 Mb on chromosome 5, 4.64–5.76 Mb on chromosome 8, and 10.64–15.52 Mb on chromosome 11, were identified to simultaneously control different ratooning-ability-related traits. Among them, qRA5 in the region of 14.12–14.65 Mb on chromosome 5 was validated for its pleiotropic effects on maximum tiller number and panicle number in the first season, as well as its maximum tiller number ratio, panicle number ratio, and grain yield ratio. Moreover, qRA5 was independent of genetic background and delimited into a 311.16 kb region by a substitution mapping approach. These results will help us better understand the genetic basis of rice ratooning ability and provide a valuable gene resource for breeding high-yield ratoon rice varieties.

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.

Grain yield response to cultivar and harvest time of the first crop in rice ratooning in southwestern Japan

AbstractRice (Oryza sativa L.) ratooning has attracted attention due to its higher yield potential compared with conventional methods. Here, field experiments were conducted in southwestern Japan in 2019 and 2020 to determine the effects of cultivar (‘Takanari’, an indica cultivar, and ‘Koshihikari’, a japonica cultivar) and harvest time of the first crop (early and late) on the grain yields of the first and second crops in rice ratooning. For Koshihikari in 2019, grain yield of the second crop did not differ between harvest times. However, Takanari produced a lower grain yield at late harvest. Takanari had fewer spikelets, fewer filled spikelets, and a lower 1,000‐grain weight at late harvest. However, for Takanari in 2020, grain yield did not differ between harvest times. In 2019, the stubble nonstructural carbohydrate (NSC) content did not increase from early to late harvest, whereas the stubble leaf area index (LAI) decreased between harvest times; this difference was more apparent in Takanari than in Koshihikari. Contrastingly, in 2020, the NSC content increased from early to late harvest, but the stubble LAI did not differ between harvest times. Thus, the lower grain yield of late‐harvested Takanari in 2019 might be attributed to the lower stubble LAI resulting in fewer spikelets. In contrast, the maintained grain yield from early to late harvest in 2020 might be attributed to the maintenance of spikelet numbers via the higher stubble NSC content. Therefore, the sufficient stubble LAI and NSC could be essential for improving grain yield of the second crop.

Effects of nitrogen fertilization for bud initiation and tiller growth on yield and quality of rice ratoon crop in central China

Rice ratooning is an ancient technology, known as harvesting twice after one sowing. In recent years, ratoon rice has drawn much attention and been widely practiced by farmers in central China because of its advantages in saving labor and increasing profit. For ratoon crop (RC), nitrogen (N) application for promoting bud initiation (Nbud) and for promoting regenerated tiller growth (Ntiller) are two common N management practices. However, it is still obscure about their effects on grain yield and quality of RC. Field experiments were conducted to compare the effects of Nbud (75 kg N ha−1 application at 12 days after heading of main crop, MC) and Ntiller (75 kg N ha−1 application at 2 days after harvesting of MC) on the grain yield and quality of RC in 2018 and 2019. Compared to Nbud, Ntiller had an evident and positive effect on grain yield, head rice percentage (HRP) and chalkiness degree (CD) of RC. Averaged across years, Nbud and Ntiller increased grain yield of RC by 5.5 % and 30.5 %, respectively. Moreover, Ntiller improved grain quality with an increase of 10.5 % in HRP and a decrease of 10.2 % in CD. Ntiller significantly increased sink size like spikelets m-2, and source ability including leaf area index, leaf N content, and crop growth rate in ratoon crop. The positive effect of Nbud on grain yield of RC was positively correlated with the increase in panicles m-2, but negatively correlated with the panicles m-2 of MC. Nbud has no effect on stubble dry weight, and significantly increased stubble N concentration, but significantly decreased stubble non-structural carbohydrate concentration at maturity in the main season. Overall, our results indicated that nutrient status of straw and panicle number in MC affected the roles of Nbud on RC yield, and more attention should be paid on Ntiller in future RC production.

Grain yield response to stubble leaf blade clipping in rice ratooning in southwestern Japan

AbstractRice (Oryza sativa L.) ratooninghas recently attracted attention due to its higher yield potential compared with that of conventional methods. Field experiments were conducted in southwestern Japan in 2019 and 2020 to determine the effect of rice type (Hokuriku 193 and high‐yielding line [HYL]) and stubble leaf treatment (clipping and control) on the grain yields of the first and second crops in rice ratooning. In 2019, both rice types produced lower grain yields of the second crop in the leaf clipping treatment than the control treatment due to the lower spikelet number m−2. Therefore, increasing the leaf area index (LAI) in the stubble may improve the grain yield of the second crop by increasing the spikelet number per area. In 2020, HYL produced a lower grain yield of the second crop in the leaf clipping treatment than the control treatment due to the lower spikelet number m−2. However, the grain yields of Hokuriku 193 did not differ between the two leaf clipping treatments. Although the nonstructural carbohydrate (NSC) content in the stubble did not differ between the two rice types in 2019, Hokuriku 193 had a higher NSC content than HYL in 2020 due to the lower spikelet number m−2 and lower percentage of filled spikelets of the first crop. These results suggest that the stubble leaf blade contribution may be reduced when the NSC content is high as the leaf blades may compensate for the lack of NSC content when the NSC content is low.

Comparisons between main and ratoon crops in resource use efficiencies, environmental impacts, and economic profits of rice ratooning system in central China

Rice production in China is constrained by excessive water consumption, labor shortage, large environmental footprint, and low economic profit. Rice ratooning is a promising practice to increase famers' profit with higher resource use efficiency and less environmental impact compared with other rice cropping systems. However, there is limited information on the differences in energy use efficiency, water and labor productivity, environmental footprint, and economic return between main crop (MC) and ratoon crop (RC) in this cropping system. This study was conducted to compare the system performance between the two crops of ratoon rice using on-farm survey data. Average grain yield was 8.40 and 4.55 t ha−1 for MC and RC, respectively. Although RC produced 45.9% lower grain yield, it had 57.3% less total energy input and 71.0% lower total production cost than MC, which resulted in a significantly higher energy use efficiency, net energy ratio, net economic return and benefit-to-cost ratio. Lower total energy input and production cost of RC was mainly attributed to the reduction in fertilizer application and labor input, respectively compared with MC. In addition, both labor and water productivity of RC was significantly higher than those of MC. Furthermore, the global warming potential (GWP) and yield-scaled GWP of RC was 59.3% and 23.4% lower than those of MC, respectively, due to lower agronomic inputs and GHGs emissions. Overall, our results suggested that RC had higher resource use efficiency, better economic performance, and less environment impact compared with MC.

Heavy soil drying during mid-to-late grain filling stage of the main crop to reduce yield loss of the ratoon crop in a mechanized rice ratooning system

Yield loss (YLoss) in the ratoon crop due to crushing damage to left stubble from mechanical harvesting of the main crop is a constraint for wide adoption of mechanized rice ratooning technology. Soil drying before the harvest of the main crop has been proposed to overcome this problem. The objective of this study was to determine the effect of soil drying during the mid-to-late grain filling stage of the main crop on grain yield of the ratoon crop in a mechanized rice ratooning system. Field experiments were conducted to compare YLoss between light (LD) and heavy (HD) soil drying treatments in Hubei province, central China in 2017 and 2018. YLoss was calculated as the percentage of yield reduction in the ratoon crop with the main crop harvested mechanically, relative to the grain yield of the ratoon crop with the main crop harvested manually. In comparison with LD, soil hardness was increased by 42.8%–84.7% in HD at the 5–20 cm soil depth at maturity of the main crop. Soil hardness at 5 and 10 cm depths reached respectively 4.05 and 7.07 kg cm−2 in HD. Soil drying treatment did not significantly affect the grain yield of the main crop. Under mechanical harvesting of the main crop, HD increased the grain yield of the ratoon crop by 9.4% relative to LD. Consequently, YLoss was only 3.4% in HD, in contrast to 16.3% in LD. The differences in grain yield and YLoss between the two soil drying treatments were explained mainly by panicles m−2, which was increased significantly by HD in the track zone of the ratoon crop compared with LD. These results suggest that heavy soil drying practice during the mid-to-late grain filling stage of the main crop is effective for reducing YLoss of the ratoon crop in a mechanized rice ratooning system.

The comparison between conventional and rice ratoon system on soil properties, rice productivity and nutrient status

<p>Ratoon system is a method of rice cultivation that produces new tillers after the mother plant is harvested and is continued by maintaining and caring for the shoots of the mother plant. In Indonesia, SALIBU and SINGGANG, which are types of rice ratooning, have been developed for Sumatra and Java regions, respectively. SALIBU is an innovation or a modification of the rice ratoon system that focuses on maintaining the time of fertigation and cutting of plant height. SINGGANG, on the other hand, is a rice ratoon system in which the management of fertigation and cutting is not considered. Both systems have not yet been implemented outside their places of origin. This study aims to compare the conventional and modified rice ratoon systems considering parameters such as soil properties, nutrient uptake, and the growth and yield of rice. The effects of rice ratoon systems (SALIBU and SINGGANG,), soil types (Inceptisols, Alfisols, and Vertisols), and cultivars (Pandan Wangi and Mekongga) were evaluated. All treatments were evaluated in a completely randomized design with three replicates in the net house. The results showed that the soil porosity in SINGGANG (48.89%) and SALIBU (46.78%) systems was higher than the conventional system (43.17%) in the Inceptisol soil and Pandan Wangi cultivars. Moreover, SINGGANG had a positive effect on the physical properties of soil (porosity and permeability); whereas, SALIBU had a positive effect on the chemical properties of soil (pH and organic carbon). In contrast, the agronomic parameters showed that the weights of dry matter and dry yield for SINGGANG were 44.96 and 23.09 g per plant clump, respectively, while those for SALIBU were 55.54 and 25.74 g per plant clump, respectively. These were lower than the conventional system (63.18 and 31.21 g per plant clump, respectively). Thus, we concluded that the SINGGANG and SALIBU ratoon systems had a positive impact on soil properties, but both systems could not promote higher rice production than the mother plant in all soil types and cultivars.</p>

Effects of nitrogen management on the ratoon crop yield and head rice yield in South USA

Ratoon rice cropping has been an important component of the rice cropping system in Texas, South Louisiana, USA and expanding in Asian countries. Two field studies were conducted with widely planted rice (Oryza sativa L.) cultivars at Eagle Lake, Texas, USA to determine the effects of nitrogen (N) management in main (first) crop (MC) and ratoon (second) crop (RC) on RC yield. In 2012 and 2013, one cultivar (Presidio) was adopted to determine the effects of RC N management on ratoon yield and head rice yield. In 2016 and 2017, CL153, CL163 and CL272 in addition to Presidio were adopted to examine the effect of MC N management on ratoon yield and head rice yield. N applied at preflood after MC harvest considerably improved RC yield. Application of 99 kg N ha−1 at preflood after MC harvest was practically adequate for RC regrowth, development and approaching the yield potential for Presidio. RC could produce quite high average grain yields of 5.90 to 6.53 t ha−1 in 2012 and 2013, respectively. Main crop N rate only significantly affected MC yield; however, given N applied of 99 kg ha−1 at preflood after MC harvest, ratoon yield was not significantly affected by MC N rate. Neither the main nor ratoon crop N management had a significant effect on RC head rice yield. Considerable RC head rice yields (55–65%) were observed in all of the four cultivars and 4 years except for CL272 in 2016. These results indicat that without very high N fertilizer application, rice ratoon crop could produce a considerable grain yield and an expectative head rice yield. Rice ratooning could be a practical way to increase rice yields with the minimal input in south Texas and regions with a similar climate.

Amylose Content, Morphology, Crystal Structure, and Thermal Properties of Starch Grains in Main and Ratoon Rice Crops

Rice ratooning, or the production of a second rice crop from stubble after the harvest of the main crop, is considered to be a green and resource-efficient rice production system. The present study was conducted to examine v... | Find, read and cite all the research you need on Tech Science Press

Developing germplasms and genetic analysis of strong ratooning ability in <italic>indica</italic> rice

Ratooning rice can efficiently utilize temperature and heat resources from the sun to increase multiple cropping index and grain yield while benefiting from one sowing and two harvests. Therefore, it is very important to rice production and food security in China. The high-yield germplasms of ratoon rice are the material basis for breeding varieties with strong ratooning ability. The lack of rice varieties with robust ratooning ability is a key factor restricting the development of ratoon rice. At present, the germplasm with strong ratooning ability is lack, and ratoon rice varieties are mainly selected from the varieties popularized in production. Therefore, it is important to apply direct breeding strategies to select for varieties of ratoon rice. The breeding technology of ratooning rice is continuously improving, and there are two methods to breed new varieties of ratoon rice. One approach is to employ combining ability to select for elite parents with strong ratooning ability and estimate the heritability of ratooning ability, which can be used to decide on selecting varieties or combinations with strong ratooning ability from its offspring. The second approach is to screen for characteristics closely related to ratooning ability of the 1st season rice. With the improvement of breeding technology, researching and solving the problem of rice ratooning ability from pedigree breeding and genetic effects will provide technical support and guarantee the direct breeding of new rice varieties with ratooning abilities. Using eight restorers applied in a large area of production as materials, directional selection and germplasm innovation were carried out by the pedigree method. In order to study the genetic characteristics of ratooning ability, the ratio of stems of ratooning bud to total stems were analyzed in a 4×4 incomplete diallel design by using the additive-dominant model. The results showed the following: (1) Genetic expression of ratooning ability was mainly controlled by both additive and dominant effects, but they were easily influenced by environmental conditions and cultivation techniques. (2) Predicted value of heritability of the ratooning ability traits were significant or extremely significant, and broad heritability ( h 2 B ) was significantly higher than broad heritability ( h 2 N ). (3) The ratooning ability was significantly different among rice restoring lines, and the ratooning ability traits of the restoring lines, Minhui 3301 and Yahui 627 had significant positive additive effects and negative dominant effects, which were suitable for screening parents with strong regeneration ability. (4) The new germplasm resources of Ra201, Ra202 and Ra212 had a higher ratio of stems of ratooning buds to total stems and strong ratooning ability, among which Ra202 had obvious advantages of low-node germination and could be used as parents for the gene mining and utilization of the ratooning ability in indica rice. (5) The study on breeding methods of ratoon rice cultivars has further improved the classical breeding techniques, and has the advantages of indirect identification and early screening. The effect of new germplasm creations and new breeding varieties were useful and insightful.

Changing the nervous mind of small‐scale farmers who are reluctant to invest for their development*

AbstractRecent increases in rice consumption in Sub‐Saharan Africa are noteworthy. Most of the rice production in these countries depends on an enormous number of small‐scale rice farmers. Because they have a poor investment capacity to follow the green revolution, that is, high‐yield variety with fertilizer and irrigation, it is necessary to raise the annual production by increasing the number of annual cropping and to improve the water productivity drastically. Salibu rice ratooning technology allows harvesting paddy rice seven times in two years by cultivating ratoon crops with high yield and dramatically low consumption of irrigation water. The authors have conducted a series of cultivation tests in Ghana for over a year and found that the average annual production of rice under the Salibu system was higher than that of the conventional rice cultivation system with much higher water productivity. The authors have also conducted a social experiment on commercial finance by rural banks to farmer‐based organizations (FBOs), organized by small‐scale rice farmers. The first target of the scheme is group purchasing of small agricultural machinery, which most of the members of the group eagerly want to obtain. We introduced special collateral systems in order to persuade rural banks reluctant to make finance to rice farmers. After realizing the first commercial finance by rural bank to FBO the path to realizing future investment in irrigation was set out in a scenario of gradual solidarity and development.

Breaking rice yield barrier with the ratooning method under changing climatic conditions: A paradigm shift in rice‐cropping systems in southwestern Japan

AbstractRice (Oryza sativa L.) ratooning has recently attracted attention since it possesses higher yield potential compared to conventional rice‐growing methods; however, it requires a longer growing season. Field experiments were conducted in southwestern Japan in 2017 and 2018 to determine the effect of harvest time (early and normal) and cutting height (high and low) of the first crop on grain yield of the first and second crops using a high‐yielding line under high N application and high air temperature conditions in rice ratooning. The highest total yield of the first and second crops was produced when the first crop was harvested at the normal time with the high cutting height in 2018. This yield reached 14.4 t ha−1, which is equivalent to threefold the average yield achieved by Japanese farmers. Plants harvested at the high cutting height produced higher grain yield of the second crop because of the larger spikelet number m−2 and better grain filling using abundant leaf area index (LAI) and nonstructural carbohydrate (NSC) in the stubble. In southwestern Japan, the daily mean air temperatures during the early growth stage of the first crop and the late ripening stage of the second crop have been increasing over time. Our results suggest that increasing LAI and NSC in the stubble by harvesting at the normal time harvest with the high cutting height under high level N application conditions may provide an adaptive strategy to increase yield with a rice‐ratooning system as growing seasons extend due to global climate change.