Plant Ideotype at Heading for Super High-Yielding Rice in Double-Cropping System in South China

The newly released super high-yielding hybrid rice combinations, Yueza 122, Fengyou 428, Peiza 67, and the super high-yielding conventional cultivars, Guangchao 3 and Shengtai 1, were grown in both early and late seasons. The morphological characters of each population were investigated at the heading stage, and the data were analyzed by using ANOVY and other statistic methods. The plant ideal morphological characters at the heading stage were established as follows： 1 ） for the early-season cropping, 90-105 cm plant height; 11-12 tillers per plant; 35-40 em length and 2.1-2.2 cm width of flag leaf; 46-50 cm length and 1.8-2.1 cm width of the second leaf from the top （L2）; 59-64 cm length and 1.4-1.9 cm width of the third leaf from the top （L3）; 7°-14°, 18° and 200-33° for the ideal leaf angles of the flag leaf, L2 and L3, respectively; 2） for the late-season cropping, 90-100 cm plant height; 9-15 tillers per plant; 30-41 cm length and 1.8-2.0 cm width of flag leaf; 53-61 cm length and 1.3-1.8 cm width of L2; 52-58 cm length and 1.2-1.5 cm width of L3; 9°-19°, 15°-37° and 16°-49° for the ideal leaf angles of the flag leaf, L2 and L3, respectively. The main physiological characteristics of these varieties were also analyzed.

CLIMATIC RISK ZONING OF DOUBLE CROPPING SUPER RICE CULTIVATION IN HUNAN PROVINCE

Based on meteorological data including daily sunshine duration, temperature and precipitation from 97 meteorological stations in Hunan province during the period of 1981—2010, in combination with the field experiment in different places at different sowing dates, the precise climatic risk zoning of double cropping super rice cultivation has been studied by using the spatial interpolation method and other Geographical Information System(GIS)technologies. Three key climatic factors were selected including chilling in May, high temperature heat damage during July to early August and low temperature damage in autumn in this study. Furthermore, based on the analysis of climatic conditions suitable for double cropping super rice cultivation and climatic disasters, 8-22 ℃ active accumulated temperature, sunshine duration from late March to October, climatic risk index of the low temperature in autumn, and climatic risk index of chilling in May were selected as key climatic factors to study the precise agro-meteorological regionalization of double cropping super rice in Hunan province. The results showed that: the high-yielding zones of double cropping super rice in Hunan were mainly located in Zhuzhou, Hengyang, Yongzhou and Chenzhou City, the moderate-yielding zones were primarily located in the east and north reaches of Dongting Lake,together with most of Changsha, Zhuzhou and Xiangtan City, and other regions in Hunan were not suitable for double cropping super rice. These findings can provide valuable information for the large-scale cultivation of double cropping super rice in Hunan province.

Studies on the Morphological Characters of South China Double Cropping Super Rice at the Active Tillering Stage

The morphological characters of the newly released super hybrid rice in South China, Yueza 122, Fengyou 428, Peiza 67, and super conventional varieties, Guangchao 3, Shengtai 1 at the active tillering stage in both early and late crops were investigated. Using the analysis of variance and other statistic methods, the ideal morphological characteristics of South China double cropping super-rice at the active tillering stage were determined. They are 55-60 cm in the early crop and 60-76 cm in the late crop for the ideal plant height, about 15 tillers in the early crop and 14-19 tillers in the late crop for the ideal tiller number per plant, 40-44 cm in the early crop and 42-60 cm in the late crop for the ideal length of the first leaf under the top leaf, 1.2-1.4 cm in the early crop and 1.2-1.3cm in the late crop for the ideal width of the first leaf under the top leaf, 39- 44 cm in the early crop and 37-43 cm in the late crop for the ideal length of the second leaf under the top leaf, 1.1-1.4 cm in the early crop and about 1.1 cm in the late crop for the ideal width of the second leaf under the top leaf, 22-58o in the early crop and 4- 12o in the late crop for the ideal top leaf angle at the active tillering stage. Based on these results, a new concept of “dynamic plant type structure” for South China double cropping super rice breeding was suggested.

Cold Damage Risk Assessment of Double Cropping Rice in Hunan, China

Combined with remote sensing data and meteorological data, cold damage risk was assessed for planting area of double cropping rice （DCR） in Hunan Province, China. A new methodology of cold damage risk assessment was built that apply to grid and have clear hazard-affected body. Each station cold damage annual frequency and average annual intensity of cold damage was calculated by using 1951-2010 station daily mean temperature and simple cold damage identification index. On this basis, average annual cold damage risk index was obtained by their product. The spatial analysis models of cold damage risk index about double-season early rice （DSER） and double-season later rice （DSLR） were established respectively by the relation of average annual cold damage risk index and its geographic factors. Critical threshold of level of average annual cold damage risk index for DSER and DSLR were respectively divided by the correlative equation of cold damage annual frequency and average annual intensity of cold damage. 2001-2010 planting area of DCR, acquired by time series analysis of MOD09AI 8-d composite land surface reflectance product, was as target of assessment. The results show average annual intensity of cold damage is exponential function of cold damage annual frequency, average annual cold damage risk index is directly proportional to cold damage cumulant and cold damage annual frequency, and is inversely proportional to happen times of cold damage and the square of statistical time sequence length. Cold damage risk of DSER is higher than DSLR in Hunan Province. In the 10-yr stacking map, DCR planting in low risk area accounted for 11.92% of total extraction area, in moderate risk area accounted for 69.62%, in high risk area accounted for 18.46%. According to the cold damage risk assessment result, DCR production can be guided to reduce cold damage losses.

Integration of Growing Milk Vetch in Winter and Reducing Nitrogen Fertilizer Application Can Improve Rice Yield in Double-Rice Cropping System

To study whether integrative fertilization [growing milk vetch in winter and reducing the dose of chemical nitrogen(N) fertilizer] can improve rice yield, and to reveal the underlying regulatory mechanisms for integrative fertilization, a three-year field trial including two treatments, milk vetch-rice-rice(MRR) and winter fallow-rice-rice(FRR), was conducted in 2010, 2011 and 2012.Our results demonstrated that the MRR treatment could significantly improve rice yield compared with the FRR treatment, especially when the application ratio of milk vetch and chemical fertilizer was 1:2.MRR treatment increased the effective panicle number and the spikelet number per panicle.In addition, a higher tillering number, leaf area index, photosynthetic-potential and photosynthetic-potential to grain ratio were observed in MRR treatment, which could provide enough dry matter for yield formation.Moreover, in MRR treatment, we discovered a higher transportation ratio and transformation ratio of dry matter in culm and leaves, and a stronger total sink capacity and spikelet-root bleeding intensity at the heading stage and 15 d after heading.Furthermore, the MRR treatment showed higher total N, phosphorus and potassium uptakes than FRR treatment, which was associated with the higher root dry weight in each soil layers.These results suggest that growing milk vetch in winter can improve rice yield under less chemical N fertilizer application, which is due to the improvement of soil nutrient status and the increased of rice root growth and development.

Substitution of chemical fertilizer by Chinese milk vetch improves the sustainability of yield and accumulation of soil organic carbon in a double-rice cropping system

The double-rice cropping system is a very important intensive cropping system for food security in China. There have been few studies of the sustainability of yield and accumulation of soil organic carbon (SOC) in the double-rice cropping system following a partial substitution of chemical fertilizer by Chinese milk vetch (Mv). We conducted a 10-year (2008–2017) field experiment in Nan County, South-Central China, to examine the double-rice productivity and SOC accumulation in a paddy soil in response to different fertilization levels and Mv application (22.5 Mg ha^–1). Fertilizer and Mv were applied both individually and in combination (sole chemical fertilizers, Mv plus 100, 80, 60, 40, and 0% of the recommended dose of chemical fertilizers, labeled as F100, MF100, MF80, MF60, MF40, and MF0, respectively). It was found that the grain yields of double-rice crop in treatments receiving Mv were reduced when the dose of chemical fertilizer was reduced, while the change in SOC stock displayed a double peak curve. The MF100 produced the highest double-rice yield and SOC stock, with the value higher by 13.5 and 26.8% than that in the F100. However, the grain yields increased in the MF80 (by 8.4% compared to the F100), while the SOC stock only increased by 8.4%. Analogous to the change of grain yield, the sustainable yield index (SYI) of double rice were improved significantly in the MF100 and MF80 compared to the F100, while there was a slight increase in the MF60 and MF40. After a certain amount of Mv input (22.5 Mg ha^–1), the carbon sequestration rate was affected by the nutrient input due to the stimulation of microbial biomass. Compared with the MF0, the MF100 and MF40 resulted in a dramatically higher carbon sequestration rate (with the value higher by 71.6 and 70.1%), whereas the MF80 induced a lower carbon sequestration rate with the value lower by 70.1% compared to the MF0. Based on the above results we suggested that Mv could partially replace chemical fertilizers (e.g., 40–60%) to improve or maintain the productivity and sustainability of the double-rice cropping system in South-Central China.

Inter-provincial Differences in Rice Multi-cropping Changes in Main Double-cropping Rice Area in China: Evidence from Provinces and Households

Since the early 1980 s, the multi-cropping index for rice has decreased significantly in main double-cropping rice area in China, which is the primary double-cropping rice(DCR) production area. This decline may bring challenges to food security in China because rice is the staple food for more than 60% of the Chinese population. It has been generally recognized that rapidly rising labor costs due to economic growth and urbanization in China is the key driving force of the ‘double-to-single' rice cropping system adaption. However, not all provinces have shown a dramatic decline in DCR area, and labor costs alone cannot explain this difference. To elucidate the reasons for these inter-provincial distinctions and the dynamics of rice cropping system adaption, we evaluated the influencing factors using provincial panel data from 1980 to 2015. We also used household survey data for empirical analysis to explore the mechanisms driving differences in rice multi-cropping changes. Our results indicated that the eight provinces in the study can be divided into three spatial groups based on the extent of DCR area decline, the rapidly-declining marginal, core, and stable zones. Increasing labor cost due to rapid urbanization was the key driving force of rice cropping system adaption, but the land use dynamic vary hugely among different provinces. These differences between zones were due to the interaction between labor price and accumulated temperature conditions. Therefore, increasing labor costs had the greatest impact in Zhejiang, Anhui, and Hubei, where the accumulated temperature is relatively low and rice multi-cropping index declined dramaticly. However, labor costs had little impact in Guangdong and Guangxi. Differences in accumulated temperature conditions resulted in spatially different labor demands and pressure on households during the busy season. As a result, there have been different profits and rice multi-cropping changes between provinces and zones. Because of these spatial differences, regionally appropriate policies that provide appropriate subsidies for early rice in rapidly-declining marginal zone such as Zhejiang and Hubei should be implemented. In addition, agricultural mechanization and the number of agricultural workers have facilitated double-cropping; therefore, small machinery and agricultural infrastructure construction should be further supported.

EFFECTS OF SOIL MOISTURE CONTENT ON DRY NURSERY SEEDLING QUALITY OF LATE DOUBLE CROPPING RICE IN SOUTH CHINA

In the present paper, an experiment was conducted to study the effects of soil moisture content on dry nursery seedling quality in Guangzhou in 1995. Through comparing the difference of dry nursery seedlings and wet nursery seedlings, we found a close relationship between soil moisture content and seedling growth. The seedling emergence of dry nursery seedling was more even, tidy and faster, and the survival rate was higher than that of wet nursery seedling. Dry nursery seedlings had small plant stature, slow leaf stretching speed and low individual seedling dry weight, but had high dry/fresh weight ratio. This was abeneficial factor for seedlings to recover from transplanting shock more quickly. As com-pared with the wet nursery seedlings, dry nursery seedlings had poor rooting ability,but had more vigorous white roots and fewer rust roots. It was the possibly important reasonfor dry nursery seedlings to form strong“explosive force”.

EFFECTS OF SEEDING DENSITY AND BASIC MANURE ON THE GROWTH OF DRY NURSERY SEEDLINGS IN LATE DOUBLE CROPPING RICE IN SOUTH CHINA

During the period of dry nursery seedling raising of late double cropping indica rice in South China, both chemical fertilizer and farmyard manure did not show obvious effect on the growth of shoot and root in young seedlings at 4-leaf stage （18-day-old seedling）, but had significant effects on root growth in old seedlings with 6-7 leaves （27-day-old seedling） at suitable seeding densities (65-125g m-2). There were satistically significant differences （at 0.01 or 0.05 levels）between treatments in root number and rooting ability of root-pruned seedlings.

Non-leguminous winter cover crop and nitrogen rate in relation to double rice grain yield and nitrogen uptake in Dongting Lake Plain, Hunan Province, China

Annual ryegrass（Lolium multiflorum Lam.）, a non-leguminous winter cover crop, has been adopted to absorb soil native N to minimize N loss from an intensive double rice cropping system in southern China, but a little is known about its effects on rice grain yield and rice N use efficiency. In this study, effects of ryegrass on double rice yield, N uptake and use efficiency were measured under different fertilizer N rates. A 3-year（2009–2011） field experiment arranged in a split-plot design was undertaken. Main plots were ryegrass（RG） as a winter cover crop and winter fallow（WF） without weed. Subplots were three N treatments for each rice season： 0（N_0）, 100（N_（100）） and 200 kg N ha–1（N_（200））. In the 3-year experiment, RG reduced grain yield and plant N uptake for early rice（0.4–1.7 t ha–1 for grain yield and 4.6–20.3 kg ha–1 for N uptake） and double rice（0.6–2.0 t ha–1 for grain yield and 6.3–27.0 kg ha–1 for N uptake） when compared with WF among different N rates. Yield and N uptake decrease due to RG was smaller in N_（100） and N_（200） plots than in N_0 plots. The reduction in early rice grain yield in RG plots was associated with decrease number of panicles. Agronomic N use efficiency and fertilizer N recovery efficiency were higher in RG plots than winter fallow for early rice and double rice among different N rates and experimental years. RG tended to have little effect on grain yield, N uptake, agronomic N use efficiency, and fertilizer N recovery efficiency in the late rice season. These results suggest that ryegrass may reduce grain yield while it improves rice N use efficiency in a double rice cropping system.

The Possible Effect of Climate Warming on Northern Limits of Cropping System and Crop Yield in China

Significantly increasing temperature since the 1980s in China has become a consensus under the background of global climate change and how climate change affects agriculture or even cropping systems has attracted more and more attention from Chinese government and scientists. In this study, the possible effects of climate warming on the national northern limits of cropping systems, the northern limits of winter wheat and double rice, and the stable-yield northern limits of rainfed winter wheat-summer maize rotation in China from 1981 to 2007 were analyzed. Also, the possible change of crop yield caused by planting limits displacement during the periods 1950s-1981 and 1981-2007 was compared and discussed. The recognized calculation methods of agricultural climatic indices were employed. According to the indices of climatic regionalization for cropping systems, the national northern limits of cropping systems, winter wheat and double rice, and the stable-yield northern limits of rainfed winter wheat-summer maize rotation during two periods, including the 1950s-1980 and 1981-2007, were drawn with ArcGIS software. Compared with the situation during the 1950s- 1980, the northern limits of double cropping system during 1981-2007 showed significant spatial displacement in Shaanxi, Shanxi, Hebei, and Liaoning provinces and Beijing municipality, China. The northern limits of triple cropping system showed the maximum spatial displacement in Hunan, Hubei, Anhui, Jiangsu, and Zhejiang provinces, China. Without considering variety change and social economic factors, the per unit area grain yield of main planting patterns would increase about 54-106% if single cropping system was replaced by double cropping system, which turned out to be 27- 58% if double cropping system was replaced by triple cropping system. In Liaoning, Hebei, Shanxi, Shaanxi, Gansu, and Qinghai provinces, Inner Mongolia and Ningxia autonomous regions, China, the northern limits of winter wheat during 1981-2007 moved northward and expanded westward in different degrees, compared with those during the 1950s-1980. Taking Hebei Province as an example, the northern limits of winter wheat moved northward, and the per unit area grain yield would averagely increase about 25% in the change region if the spring wheat was replaced by winter wheat. In Zhejiang, Anhui, Hubei, and Hunan provinces, China, the planting northern limits of double rice moved northward, and the per unit area grain yield would increase in different degrees only from the perspective of heat resource. The stable- yield northern limits of rainfed winter wheat-summer maize rotation moved southeastward in most regions, which was caused by the decrease of local precipitation in recent years. During the past 50 yr, climate warming made the national northern limits of cropping systems move northward in different degrees, the northern limits of winter wheat and double rice both moved northward, and the cropping system change would cause the increase of per unit area grain yield in the change region. However, the stable-yield northern limits of rainfed winter wheat-summer maize rotation moved southeastward due to the decrease of precipitation.

Analysis on Dry Matter Production Characteristics of Super Hybrid Rice

Six middle-season indica hybrid rice combinations, including five super hybrid rice combinations with the high yield about 10.5 t/ha and a check hybrid rice combination Shanyou 63 with a yield potential about 9.5 t/ha, were used as materials to study the dry matter production characteristics. The super hybrid rice showed a high ability in dry matter production and accumulation and its yield enhanced with the increase of dry matter accumulation. The advantage period of dry matter production in the super hybrid rice was mainly at the middle and late growth stages compared with the check. The grain yield had no significant correlation with the dry matter accumulation before the elongation stage while had a significantly positive correlation with the dry matter accumulation from the elongation to maturity stages in super hybrid rice. There were more dry matter in vegetative organs at the heading stage in the super hybrid rice but its contribution to yield （apparent conversion percentage） was averagely 4.3 percent points lower than that in the check. For crop growth rate （CGR）, the comparative advantage of super hybrid rice was at the middle and late stages, especially after flowering. Moreover, as the rising of leaf area index （LAI） and leaf area duration （LAD）, CGR enhanced. The total LAD and the mean of lAD per day of super hybrid rice was about 14.79% and 10.31% higher than those of the check, respectively. The results indicate that the high yield of super hybrid rice mostly comes from the products of photosynthesis after heading, which is shown by the increased CGR at middle and later stages. It is suggested that LAD character might be used to better explain the advantage in the dry matter production of super hybrid rice than LAI.

Research Advances in High-Yielding Cultivation and Physiology of Super Rice

In 1996,China launched a program to breed super rice or super hybrid rice by combining intersubspecific heterosis with ideal plant types.Today,approximately 80 super rice varieties have been released and some of them show high grain yields of 12-21 t/hm2 in field experiments.The main reasons for the high yields of super rice varieties,compared with those of conventional varieties,can be summarized as follows：more spikelets per panicle and larger sink size （number of spikelets per square meter）;larger leaf area index,longer duration of green leaf,greater photosynthetic rate,higher lodging resistance,greater dry matter accumulation before the heading stage,greater remobilization of pre-stored carbohydrates from stems and leaves to grains during the grain-filling period;and larger root system and greater root activity.However,there are two main problems in super rice production：poor grain-filling of the later-flowering inferior spikelets （in contrast to earlier-flowering superior spikelets）,and low and unstable seed-setting rate.Here,we review recent research advances in the crop physiology of super rice,focusing on biological features,formation of yield components,and population quality.Finally,we suggest further research on crop physiology of super rice.

高标准农田建设提升了农户种粮积极性吗?——基于双季稻种植的考察

高标准农田建设是增强粮食综合生产能力,强化国家粮食安全保障的重要举措。基于江西省1556份微观农户调查数据,采用双季稻种植行为来衡量农户种粮积极性,实证分析高标准农田建设对传统双季稻主产区农户种粮积极性的影响及其作用机制。研究发现:(1)高标准农田建设显著提高了农户种粮积极性,促进传统双季稻主产区农户种植双季稻,并扩大双季稻种植规模,该结论在进行稳健性检验后依然成立。(2)机制分析表明,促进农业社会化服务发展、降低农业生产成本、诱导农地转入是高标准农田建设提高农户种粮积极性的三个重要路径。(3)异质性分析发现,高标准农田建设对农地调整、低细碎化与非平原地区农户的双季稻种植行为有更明显的促进作用。为进一步强化粮食安全保障,更好地发挥高标准农田建设的种粮激励效应,应持续大力推进高标准农田建设,优化高标准农田建设模式,着力降低高标准农田的细碎化程度。

华南地区早晚兼用型水稻产量和氮素吸收在早、晚季的差异特征

为明确华南双季稻区早晚兼用型水稻产量和氮素吸收在早、晚季的差异特征,以6个早晚兼用型水稻品种为试验材料,按当地高产栽培条件在早、晚季种植,测定其产量、产量构成、干物质积累和氮素吸收等。结果表明,早晚兼用型水稻在早、晚季种植时产量分别为6.68~7.91 t/hm^(2)和5.72~6.11 t/hm^(2);早季产量显著高于晚季,平均增幅为1.53 t/hm^(2)。相关分析表明,较高的早季产量与其有效穗数和粒重的提高有关。早、晚季干物质积累量和氮素吸收差异显著;相对于晚季,早季成熟期干物质积累量和氮素吸收平均提高25.0%和29.5%。另外,早、晚季产量与其干物质积累量和氮素吸收显著正相关。早晚兼用型水稻在早季种植时具有较高的产量、物质生产和氮素吸收能力。研究结果可为华南地区早晚兼用型水稻的丰产栽培提供理论依据。

Dynamics of decadal changes in the distribution of double-cropping rice cultivation in China

Quantitative description of changes in the distribution of paddy rice cultivation in response to recent climate change provides a reference for rice cultivation patterns and formulation of countermeasures to cope with future climate change in China. This study analyzes the dynamics of decadal changes in distribution of double-cropping rice in China during 1961-2010 in relation to climate change based on the maximum entropy method. Decadal changes in the double-cropping rice cultivation area and climatic suitability in China were apparent. The total area of climatically suitable regions was highest in the 1960s, and subsequently showed an increasing trend at first and then a decreasing trend from the 1970s to 2000s. However, the low climatic suitability area decreased, which implied that the moderate and high climatic suitability areas increased. Among the latter, the high climatic suitability area showed the highest increase in extent to 4.4 times that of the 1990s and four times that of the 1960s. The areas of double-cropping rice cultivation most sensitive to climate change are mainly located in central Jiangsu, central Anhui, the eastern Sichuan Basin, southern Henan and central Guizhou. Transformation of areas between low and moderate climatic suitability was observed in northern Zhejiang, southern Anhui and Hubei, and northern Guangxi. Transformation of areas between moderate and high climatic suitability was observed in central Jiangxi and Leizhou Peninsula. The northern boundary of double-cropping rice cultivation in China shifted southwards and contracted eastwards in the 1970s, and extended northwards in the 1980s. However, the northern boundary did not shift northwards in response to climate warming in the 2000s.

CH_4 and N_2O emissions from double-rice cropping system as affected by Chinese milk vetch and straw incorporation in southern China

Chinese milk vetch(CMV) and rice straw(RS)were incorporated into soil to substitute for synthetic N fertilizers and to maintain soil fertility. However, little is known about the integrated impacts of CMV and RS incorporation on CH_4 and N_2O emissions in double-rice cropping systems in southern China. A field experiment was conducted to estimate the integrated impacts of CMV and RS incorporation in the early-and late-rice seasons on CH_4 and N_2O emissions. All treatments received uniform N inputs, 6%–37% of which was replaced by CMV and RS crop residue. CMV and/or RS incorporation produced equivalent or slightly more grain yield, while reducing N2 O emissions by 3%–43%. However, both CMV and RS incorporation increased CH_4 emissions. Annual CH_4 emissions ranged from 321 to 614 kg·hm^(–2)from CMV and RS amendment treatments, which were 1.5–2.9 times higher than that from synthetic N. Compared with single synthetic N fertilizer, incorporation of CMV and/or RS increased GWP and yield-scaled GWP by 45%–164% and45%–153%, respectively. Our results demonstrate CMV and RS amendments replacing N fertilizer, maintained stable yield, mitigated N_2O emission, but enhanced CH_4 emission. Further study is needed on crop residue management in double-cropping rice systems.

Reconstructing rice phenology curves with frequency-based analysis and multi-temporal NDVI in double-cropping area in Jiangsu, China

Crop phenology retrieval in the double-crop- ping area of China is of great significance in crop yield estimation and water management under the influences of global change. In this study, rice phenology in Jiangsu Province, China was extracted from multi-temporal MODIS NDVI using frequency-based analysis. Pure MODIS pixels of rice were selected with the help of TM images. Discrete Fourier Transformation （DFT）, Discrete Wavelet Transformation （DWT）, and Empirical Mode Decomposition （EMD） were performed to decompose time series into components of different frequencies. Rice phenology in the double-cropping area is mainly located on the last 2 IMFs of EMD and the first 2-3 frequencies of DFT and DWT. Compared with DFT and DWT, EMD is limited to fewer frequencies. Multi-temporal MODIS NDVI data combined with frequency-based analysis can retrieve rice phenology dates with on average 79% valid estimates. The sorting result for effective estimations from different methods is DWT （85%） 〉 EMD （80%） 〉 DFT （74%）. Planting date （88%） is easier to estimate than harvesting date （70%）. Rice planting date is easily affected by the former cropping mode within the same year in a double-cropping region. This study sheds light on under- standing crop phenology dynamics in the frequency domain of multi-temporal MODIS data.

安徽稻油两熟制不同种植方式下气候资源配置和演变

安徽沿江地区稻-油复种模式下茬口衔接紧密、光温资源紧张,季节间气候资源配置备受关注。移栽和直播是补充和调配气候资源的有效种植方式,而稻油两熟制中不同种植方式下不同作物生长季气候资源配置、演变特征以及对未来气候变化的适应性尚不清晰。本研究以安徽沿江地区27个气象站1992—2022年的气温、日照时数、总辐射和降水等气象资料为基础,分析了不同种植方式下稻-油复种季节间气候资源配置与演变特征以及光温生产潜力。结果表明,近30年稻-油复种模式下季节间总辐射量、日照时数和光合生产潜力均呈下降趋势,气温、降水量和光温生产潜力呈上升趋势。水稻季移栽和直播方式下总辐射量倾向率分别为-27.9 MJ·m^(-2)·(10a)^(-1)和-28.8MJ·m^(-2)·(10a)^(-1),油菜季分别为-40.5 MJ·m^(-2)·(10a)^(-1)和-26.6 MJ·m^(-2)·(10a)^(-1)。水稻季移栽和直播方式下平均日最高气温倾向率分别为0.30℃·(10a)^(-1)(P<0.05)和0.24℃·(10a)^(-1),最高达32.70℃(2022年,青阳)。油菜季移栽和直播方式下平均气温倾向率分别为0.36℃·(10a)^(-1)(P<0.01)和0.39℃·(10a)^(-1)(P<0.01),移栽方式下平均气温较直播方式高0.96~1.43℃。稻油两熟制两季均面临光资源持续下降和气温不断上升等问题,采用移栽方式可通过延长作物生育期优化光、温资源配置,提高光温生产潜力。同时,适当推迟移栽期将有利于应对油菜苗期和水稻花期的高温。直播方式下宜采用高光效品种和构建光资源高效利用作物群体。