Ratoon Rice Research Articles

Root-zone fertilization of controlled-release urea reduces nitrous oxide emissions and ammonia volatilization under two irrigation practices in a ratoon rice field

The ratoon rice system is one method to increase grain yield in areas where the annual accumulation of temperature and light resources are significantly greater than that required for single-cropping rice but insufficient for double-season rice. Rice fields are important sources of N 2 O and NH 3 emissions. Root-zone fertilization (RF) and controlled-release urea (CRU) show promise in decreasing the amount of emissions of N 2 O and NH 3 . However, the effects of their application on rice-ratoon rice (RR) are currently poorly understood. The effect of a combination of RF and CRU on the emissions of N 2 O and NH 3 from RR fields merits clarification. Therefore, a field experiment was conducted for 2 years. Five treatments were established with 280 kg N ha −1 (CK: no N fertilizer; FFP: urea with 5-split surface broadcasting; RF1: RF of CRU applied once into 5 cm deep holes positioned 5 cm from the rice root as basal fertilizer; RF2: RF of CRU applied once into 10 cm deep holes positioned 5 cm from the rice root as basal fertilizer; and RF3: RF of CRU layered once into 5 cm and 10 cm deep holes positioned 5 cm from the rice root as basal fertilizer), and the plants were subjected to continuous flooding (CF) and alternate wetting and drying (AWD). The results showed that over a 2-year period, the RF treatments significantly reduced N 2 O emissions by 55–82 % (under CF) and 52–82 % (under AWD) compared with FFP and significantly reduced the loss owing to NH 3 volatilization by 47–69 % (under CF) and 43–65 % (under AWD) compared with FFP. RF2 and RF3 increased the 2-year average total yield of RR by 5–10 % (under CF) and 7–11 % (under AWD). In addition, the distribution of NH 4 + -N in the root-zone soil of RF3 was more consistent with the rule of nutrient requirement during the long growth period of RR and had a higher ability to increase yield and stronger environmental benefits than FFP. Soil NH 4 + -N and NO 3 - -N in field water are the main factors for N 2 O emissions and NH 3 volatilization, respectively. AWD did not reduce N 2 O emissions and NH 3 volatilization but saved water resources. Therefore, the combination of RF technology and AWD is a promising strategy to simplify the sustainable cultivation of RR. • RF of CRU reduced N 2 O emissions and NH 3 volatilization in RR. • Layered RF of CRU had highest rice yield due to reasonable NH 4 + - N distribution. • The N 2 O fluxes were related to the NO 3 -N concentrations in the 4–20 cm soil. • RF of CRU reduced NH 3 volatilization due to lower NH 4 + -N concentration.

Alternate wetting and moderate soil drying could increase grain yields in both main and ratoon rice crops

AbstractAlternate wetting and drying irrigation is a widely used irrigation method for water‐savings and high‐yielding in rice (Oryza sativa L.) production; however, its effect on grain yield (GY) in the main and ratoon crops is unclear. With two rice cultivars as materials, the effects on GY in the main and ratoon crop of three irrigation regimes, that is, conventional flooding irrigation (CI), alternate wetting and moderate soil drying irrigation (WMD), and alternate wetting and severe soil drying irrigation (WSD), during grain filling of the main crop were investigated. Compared with CI, WMD increased GY by 6.0∼6.5% in the main crop by increasing the 1,000‐grain weight and filled grain rate, whereas the ratoon crop GY increased by 13.3∼14.6% via increased panicle number. The WSD had no significant effects on the main crop GY, but significantly decreased ratoon crop GY by decreasing panicle number. A higher leaf photosynthetic rate, leaf area index, root oxidation activity, dry matter accumulation and nonstructural carbohydrate (NSC) translocation under WMD primarily drove the increased 1,000‐grain weight and filled grain rate in the main crop. Under WMD, higher soluble sugar contents catalysed by high amylase activity and higher zeatin + zeatin riboside in stems of the main crop promoted the growth of regenerated buds and increased the ratoon crop panicle number. In conclusion, WMD during grain filling of the main crop improved the growth and development of the main crop and promote the germination of regenerated buds, thereby increasing the GY of both main and ratoon crops.

Design and test of smashing and scattering device of double-channel feeding ratoon rice harvester

Since it is requested that the smashed straw should not be scattered onto the stubble in the first season harvest, a smashing and scattering device matched with the first season harvester of ratoon rice was designed in this paper to smash and scatter the straw into the rolling area. The main structural parameters affecting the straw scattering performance were determined by theoretical analysis of the deflecting performance of the straw deflector. EDEM software was used to simulate and analyze the straw scattering situation under the action of the deflector. Taking the qualified rate of straw scattering as the performance index, the optimal parameter combination of the straw deflector was determined by L27 (313) orthogonal test, and the operating performance of the device was verified by bench test and field comparison test. The test results show that: The optimal parameter combination was 45° between the straw deflector and the vertical direction, 200 mm height difference between straw deflector and outlet, 0° inclination angle of inner deflector and 35° inclination angle of outer deflector. The qualified rate of straw scattering was 72.2% in the corresponding simulation test, 93.6% in the bench test and 95.2% in the field test, which could meet the demand of first season harvest of ratoon rice.

Exploration of feasible rice-based crop rotation systems to coordinate productivity, resource use efficiency and carbon footprint in central China

Resource scarcity, large environmental footprint and low economic profits are great challenges faced by global crop production. Development of feasible cropping systems that can coordinate productivity and sustainability is critical for addressing these challenges. Here, field experiments were conducted from 2017 to 2020 to compare the energy equivalent yield, energy use efficiency, labor and water productivity, carbon footprint, and net ecosystem economic benefits of the six rice-based crop rotation systems in central China, including rice-wheat (RW), rice-rapeseed (RRs), double-season rice (DR), ratoon rice (RR), maize-rice (MR), and rice-fallow systems (RF). The results demonstrated that MR had the highest energy equivalent yield of 20.3 Mg ha−1 among all the tested rotation systems, which was significantly increased by 28.0%, 32.8%, 18.9%, 26.9%, and 99.5% compared with that of RW, RRs, DR, RR, and RF, respectively. MR and RR achieved higher energy use efficiency than RW, RRs and DR due to their higher total energy output and lower total energy input, respectively. Meanwhile, MR and RR also exhibited the highest water and labor productivity among these rotation systems, respectively. Furthermore, their carbon footprint per area and per energy output were comparable to those of RW and RRs, but significantly lower than those of DR. Overall, MR and RR increased the net ecosystem economic benefits by 12.6–76.8% and 25.1–188.3% relative to other four traditional systems (RRs, RW, DR and RF), respectively. These results suggest that MR and RR are the recommended feasible rice-based crop rotation systems to coordinate high productivity, resource use efficiency, and economic benefit with lower carbon footprint in central China.

Ratoon rice with direct seeding improves soil carbon sequestration in rice fields and increases grain quality.

Increasing both carbon (C) sequestration and food production is essential for a sustainable future. However, increasing soil C sequestration or graining yield/quality in rice (Oryza sativa L.) systems has been a tradeoff in that pursuing one goal may compromise the other goal. Field experiments were designed to evaluate methane emission and grain yield in two rice systems in southern China, including the traditional double rice with a seedling transplanting system and innovative ratoon rice with a direct seeding system. Grain yield, grain quality, methane (CH4) emission, and total organic carbon (TOC) loss rate were investigated, and yield-scaled CH4 gas emission was assessed. It is found that double rice has a higher grain yield than ratoon rice. However, the grain quality (processing, appearance of chalkiness degree and chalky grain percentage, and nutritional quality) of ratoon rice is superior to double rice, especially the ratoon crop. The yield-scaled CH4 emission of ratoon rice (0.06kgkg-1) decreased by 49.29% than double rice (0.12kgkg-1) throughout the growth period. Compared with the TOC loss rate of double rice (2.95gkg-1), the rate of ratoon rice was lower (1.97gkg-1). As a result, ratoon rice with direct seeding can not only improve grain quality but also mitigate yield-scaled CH4 gas emission and TOC loss rate of rice fields. Therefore, we suggest to use ratoon rice with a direct seeding technique to promote agricultural C sequestration.

Effects of skip-row planting on grain yield and quality of mechanized ratoon rice

Decreases in grain yield and milling quality in the ratoon crop due to crushing damage to stubbles from mechanical harvesting of the main crop constrain the further extension of mechanized rice ratooning technology. Skip-row planting (SP), where the track zone is left untransplanted in the main crop to provide traffic paths for harvest machines, might be effective to alleviate these constraints by avoiding the crushing damage. However, it is remains unclear if border effects could compensate for the yield loss due to decreased planting density from SP in both the main and ratoon crops, and if SP could improve the milling quality of the ratoon crop. To address these questions, a SP pattern with 33.3% decrease in planting density was compared to conventional planting (CP) pattern in field experiments on mechanized ratoon rice in 2018 and 2019. Compared with CP, the grain yield of the main and ratoon crops in SP was reduced by 4.8% and increased by 4.6%, respectively. The large decrease in planting density from SP did not affect grain yield substantially because of the border effects on grain yield in the rows next to traffic paths in both crops. Panicle number, spikelet number panicle −1 , and total dry weight were responsible for the border effects on grain yield in the main crop, whereas panicle number and total dry weight were responsible for the border effects on grain yield in the ratoon crop. Milling quality of the ratoon crop was improved by SP, and the improvement in head rice rate was 2.5–7.0% compared with CP. Our results suggest that SP is effective for improving milling quality of the ratoon crop in mechanized rice ratooning system by avoiding the crushing damage, while maintaining high grain yield of the two crops due to the border effects. • Skip-row planting did not affect grain yield substantially in mechanized rice ratooning system due to border effects. • Panicle number, spikelet number panicle −1 , and total dry weight were responsible for border effect in main crop. • Panicle number and total dry weight were responsible for border effect in ratoon crop. • Skip-row planting improved the milling quality of ratoon crop by avoiding the crushing damage.

Border effects of the main and ratoon crops in the rice ratooning system

The border effect (BE) is widely observed in crop field experiments, and it has been extensively studied in many crops. However, only limited attention has been paid to the BE of ratoon rice. We conducted field experiments on ratoon rice in Qichun County, Hubei Province, Central China in 2018 and 2019 to compare the BE in the main and ratoon crops, and to quantify the contribution of BE in the main crop to that in the ratoon crop. The BE of two hybrid varieties was measured for the outermost, second outermost, and third outermost rows in each plot of both crops. To determine the contribution of BE between the two crops, portions of hills in the outermost and second outermost rows were uprooted during the harvest of the main crop so that the second and third outermost rows then became the outermost rows in the ratoon crop. Overall, the BE on grain yield was greater in the main crop than in the ratoon crop. In the main crop, the BE on grain yield was 98.3% in the outermost row, which was explained by the BE on panicles m−2, spikelets/panicle, spikelets m−2, and total dry weight. In the ratoon crop, the BE on grain yield was reduced to 60.9 and 27.6% with and without the contribution of the BE in the main crop, respectively. Consequently, 55.1% of the BE on grain yield in the ratoon crop was contributed from the main crop. High stubble dry weight and non-structural carbohydrate (NSC) accumulation at the harvest of the main crop were responsible for the contribution of BE in the main crop to that in the ratoon crop. Our results suggest that increases in stubble dry weight and NSC accumulation at the harvest of the main crop could be important strategies for developing high-yielding cropping practices in the rice ratooning system.

Evaluation of the Effects of Cutting Height and Application of Bio-Chemical Fertilizers on Yield and Nutritional Quality of Ratoon Rice

Evaluation of the Effects of Cutting Height and Application of Bio-Chemical Fertilizers on Yield and Nutritional Quality of Ratoon Rice

Impact of Tillage and Straw Treatment Methods on Rice Growth and Yields in a Rice–Ratoon Rice Cropping System

The rice–ratoon rice cropping system has the advantages of saving labor and imparting economic benefits. Optimizing tillage and straw management is beneficial for improving ratoon rice growth and yield. In this study, field experiments were conducted to examine the effects of four tillage and straw managements on the growth and yield of a rice–ratoon rice cropping system in central China in 2020 to 2021. The managements included no-till with main-season and ratoon-season rice residues retained on the soil’s surface (NT+S), plow tillage with residue retention (CT+S), no-till with residues removed (NT-S), and plow tillage with residues removed (CT-S). Compared to NT, CT significantly increased yield by 33.70% and 29.12% in the main and ratoon seasons, respectively. Compared to straw removal, straw returning significantly increased yield by 13.37% and 27.29% in the main and ratoon seasons, respectively. In general, both CT and straw returning improved root function (root activity and root dry weight) and photosynthetic capacity (leaf area index, net photosynthetic rate, and leaf chlorophyll content). CT combined with straw returning was able to achieve the highest annual rice yield.

Damage of brown planthopper (BPH) Nilaparvata lugens and rice leaf folder (LF) Cnaphalocrocis medinalis in parent plants lead to distinct resistance in ratoon rice

ABSTRACT Herbivore-induced defense responses are often specific, whereas plants could induce distinct defense responses corresponding to infestation by different herbivorous insects. Brown plant hopper (BPH) Nilaparvata lugens, a phloem-feeding insect, and rice leaf folder (LF) Cnaphalocrocis medinalis, a chewing insect, are both specialist herbivores on rice. To characterize the distinct resistance primed by prior damage to these two specialist herbivores, we challenged rice plants with two herbivores during vegetative growth of parent plants and assessed plant resistance in subsequent ratoons. Here, we show that LF and BPH induce different suites of defense responses in parent rice plants, LF induced higher level of JA accumulation and OsAOS, OsCOI1 transcripts, while BPH induced higher accumulation of SA and OsPAL1 transcripts. Moreover, an apparent loss of LF resistance was observed in OsAOS, OsCOI1 RNAi lines. Ratoon plants generated from parents receiving prior LF infestation exhibited higher jasmonic acid (JA) levels and elevated levels of transcripts of defense-related genes associated with JA signaling, while ratoon generated from parents receiving prior BPH infestation exhibited higher salicylic acid (SA) levels and elevated levels of transcripts of defense-related genes associated with SA signaling. Moreover, previous LF infestation obviously elevated ratoons resistance to LF, while previous infestation by BPH led to enhanced resistance in ratoons to BPH. Pre-priming of ratoons defense to LF was significantly reduced in OsAOS and OsCOI1 RNAi plant, but silencing OsAOS and OsCOI1 did not attenuate ratoons resistance to BPH. These results suggest that infestation of two specialist herbivores with different feeding styles in parent crop led to distinct defense responses in subsequent rations, and the acquired resistance to LF in ratoons is associated with priming of jasmonic acid-dependent defense responses.

Optimizing Nitrogen Application for Chinese Ratoon Rice Based on Yield and Reactive Nitrogen Loss

Ratoon rice (RR) has been regarded as a labor-saving and beneficial production system. Nitrogen (N) surplus and reactive N losses (Nr losses) are effective environmental indicators used to evaluate the performance of N management. Few studies have assessed N surplus and Nr losses for Chinese RR. In this study, Chinese RR planting areas were divided into South China (SC), the southern part of East China (SEC), Central China (CC), the northern part of East China (NEC), and Southwest China (SW). N surplus and Nr losses were also calculated based on 782 studies using a quadratic model under optimized N management for the highest yield (OPT-yield), the highest N-use efficiency (NUE) (OPT-NUE), and the highest grain N uptake (OPT-N uptake). The RR yields in the five regions ranged from 9.98 to 13.59 t ha−1. The high-yield record was observed in SEC, while the low-yield record was observed in NEC. The highest and the lowest Nr losses were found in NEC and SC, respectively. N surplus was reduced, while the yield was maintained in SEC, CC, NEC, and SW under OPT-yield and OPT-N uptake, and N surplus and Nr losses were reduced in the five regions when targeting the highest NUE. Farmers should be encouraged to plant RR in SEC and CC. RR was also a good choice when N management measures were conducted in three other regions. To achieve a win–win situation for both yield and the environment, OPT-yield could serve to improve the N management of current conventional practices.

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.

The Design and Test of the Chassis of a Triangular Crawler-Type Ratooning Rice Harvester

Due to the high rolling rate of a regular crawler paddy harvester and the absence of mature first season harvester products of ratooning rice, combined with the planting mode and harvest requirements of ratooning rice, a triangular crawler ratooning rice harvester is specifically designed. The structure and steering principle of the triangular crawler chassis are described. The hydraulic system is simulated and analyzed by AMESim2020 (Guangzhou, China) to verify the rationality of its design; RecurDynV9R4 (Guangzhou, China) is used to simulate and analyze the field straight/turning situation of differential steering chassis and rear-axle steering chassis. The results show that the rear axle steering chassis has a smaller turning radius and lower rolling loss rate and the change of track tension is more stable during steering. The field test is conducted to verify the reliability of the simulation results. The field test shows that the rolling loss rate of the rear axle steering chassis is reduced by 27.9% compared with the differential steering chassis. The machine’s operating speed is 2.8 km/h, the minimum turning radius is 780 mm, and the straight rolling rate is 26.8%. The operating performance is stable, and the operational process is smooth. Compared with the existing conventional harvester, the linear rolling rate of the first harvest of ratooning rice is reduced by 26.1%, and the test results are consistent with the RecurDyn simulation results. The results are reliable, providing a reference for the theoretical research of the chassis of the later ratoon rice harvester.

Productivity and water use of ratoon rice cropping systems with water‐saving, drought‐resistant rice

AbstractWater‐saving, drought‐resistant rice (WDR) (Oryza sativa L.) is a type of new rice cultivars with high drought resistance and low water consumption in the production phase. Ratoon rice cropping is regarded as a resource‐efficient rice production system with low cost and high profit. The development of ratoon rice system with WDR is conducive to the sustainable production of rice and the expansion of rice plantation; however, no such attempt has been made. In this study, a field experiment was conducted for 2 yr to evaluate the feasibility of developing new ratoon rice cropping systems using WDR compared with using common lowland rice (CLR). The productivity, regenerative capacity, and water use efficiency (WUE) were investigated in the water‐saving cultivation system using two WDR cultivars—Jieyou 652 and Jieyou 804—and in the conventional flooding cultivation system using the CLR cultivar Fengliangyouxiang 1. The irrigation WUE for the WDR systems was 89.8–214.8% and 243.4–765.6% higher than for the CLR system in the main and ratoon cropping seasons, respectively. The grain yield was not significantly different in the main cropping season between the WDR and CLR systems; nevertheless, it was lower in the WDR systems because of shorter growth duration and smaller panicles in the ratoon season. Higher accumulations of dry matter (DM), nonstructural carbohydrates (NSCs), and nitrogen in the stubble of main‐season crops is helpful to the promotion of regenerative capacity of WDR in the ratoon season.

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).

Shifting Rice Cropping Systems Mitigates Ecological Footprints and Enhances Grain Yield in Central China.

Intensive cereal production has brought about increasingly serious environmental threats, including global warming, environmental acidification, and water shortage. As an important grain producer in the world, the rice cultivation system in central China has undergone excessive changes in the past few decades. However, few articles focused on the environmental impacts of these shifts from the perspective of ecological footprints. In this study, a 2-year field trial was carried out in Hubei province, China, to gain insight into carbon footprint (CF), nitrogen footprint (NF), and water footprint (WF) performance. The three treatments were, namely, double-rice system (DR), ratoon rice system (RR), and rice-wheat system (RW). Results demonstrated that RR significantly increased the grain yield by 10.22–15.09% compared with DR, while there was no significant difference in the grain yield between RW and DR in 2018–2019. All of the calculation results by three footprint approaches followed the order: RR < RW < DR; meanwhile, RR was always significantly lower than DR. Methane and NH3 field emissions were the hotspots of CF and NF, respectively. Blue WF accounts for 40.90–42.71% of DR, which was significantly higher than that of RR and RW, primarily because DR needs a lot of irrigation water in both seasons. The gray WF of RW was higher than those of DR and RR, mainly due to the higher application rate of N fertilizer. In conclusion, RR possesses the characteristics of low agricultural inputs and high grain yield and can reduce CF, NF, and WF, considering the future conditions of rural societal developments and rapid demographic changes; we highlighted that the RR could be a cleaner and sustainable approach to grain production.

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.

Research Progress and Prospect of Mechanized Harvesting Technology in the First Season of Ratoon Rice

The first seasonal harvest technology of ratoon rice requires the least rolling with suitable stubble height required by agronomy when the ratoon rice is nearly mature. Mechanized harvesting in the first season of ratoon rice needs to finish harvesting, threshing, cleaning, straw treatment, grain transportation, grain collection and other processes at one time with a low rolling rate and low rolling degree. Limited by the production conditions such as wet and soft fields, and wet, thick and strong straw, harvest technology with high efficiency and a low rolling rate of ratoon rice in the first season has become the key technology and research focus affecting the yield of ratoon rice. In this paper, we analyzed the planting and popularization of ratoon rice in China, summarized the planting mode and agronomic characteristics of ratoon rice, highlighted the research status of mechanized harvesting equipment for the first season of ratoon rice, especially the specialized harvesters, and illustrated in detail the technical characteristics and research trends of key segments such as chassis, header, and processes such as threshing and cleaning, and straw and stubble treatment of ratoon rice harvesters. In addition, we summarized the application status and value of lightweight technology, performance monitoring and fault diagnosis technology, grain quality detection technology and automatic navigation technology of mechanized harvest in the first season, explained the main problems and reasons affecting the development of ratoon rice harvest mechanization in China, and illustrated the prospect of its research focus and tendency.