A phenology-based vegetation index for improving ratoon rice mapping using harmonized Landsat and Sentinel-2 data

Ratoon rice,which refers to a second harvest of rice obtained from the regenerated tillers originating from the stubble of the first harvested crop,plays an important role in both food security and agroecology while requiring minimal agricultural inputs.However,accurately identifying ratoon rice crops is challenging due to the similarity of its spectral features with other rice cropping systems(e.g.,double rice).Moreover,images with a high spatiotemporal resolution are essential since ratoon rice is generally cultivated in fragmented croplands within regions that frequently exhibit cloudy and rainy weather.In this study,taking Qichun County in Hubei Province,China as an example,we developed a new phenology-based ratoon rice vegetation index(PRVI)for the purpose of ratoon rice mapping at a 30 m spatial resolution using a robust time series generated from Harmonized Landsat and Sentinel-2(HLS)images.The PRVI that incorporated the red,near-infrared,and shortwave infrared 1 bands was developed based on the analysis of spectro-phenological separability and feature selection.Based on actual field samples,the performance of the PRVI for ratoon rice mapping was carefully evaluated by comparing it to several vegetation indices,including normalized difference vegetation index(NDVI),enhanced vegetation index(EVI)and land surface water index(LSWI).The results suggested that the PRVI could sufficiently capture the specific characteristics of ratoon rice,leading to a favorable separability between ratoon rice and other land cover types.Furthermore,the PRVI showed the best performance for identifying ratoon rice in the phenological phases characterized by grain filling and harvesting to tillering of the ratoon crop(GHS-TS2),indicating that only several images are required to obtain an accurate ratoon rice map.Finally,the PRVI performed better than NDVI,EVI,LSWI and their combination at the GHS-TS2 stages,with producer's accuracy and user's accuracy of 92.22 and 89.30%,respectively.These results demonstrate that the proposed PRVI based on HLS data can effectively identify ratoon rice in fragmented croplands at crucial phenological stages,which is promising for identifying the earliest timing of ratoon rice planting and can provide a fundamental dataset for crop management activities.

The underlying mechanism of variety–water–nitrogen–stubble damage interactions on yield formation in ratoon rice with low stubble height under mechanized harvesting

Agronomic measures are the key to promote the sustainable development of ratoon rice by reducing the damage from mechanical crushing to the residual stubble of the main crop, thereby mitigating the impact on axillary bud sprouting and yield formation in ratoon rice. This study used widely recommended conventional rice Jiafuzhan and hybrid rice Yongyou 2640 as the test materials to conduct a four-factor block design field experiment in a greenhouse of the experimental farm of Fujian Agricultural and Forestry University, China from 2018 to 2019.The treatments included fertilization and no fertilization, alternate wetting and drying irrigation and continuous water flooding irrigation, and plots with and without artificial crushing damage on the rice stubble. At the same time, a 13C stable isotope in-situ detection technology was used to fertilize the pot experiment. The results showed significant interactions among varieties, water management, nitrogen application and stubble status.Relative to the long-term water flooding treatment, the treatment with sequential application of nitrogen fertilizer coupled with moderate field drought for root-vigor and tiller promotion before and after harvesting of the main crop, significantly improved the effective tillers from low position nodes. This in turn increased the effective panicles per plant and grains per panicle by reducing the influence of artificial crushing damage on rice stubble and achieving a high yield of the regenerated rice. Furthermore, the partitioning of 13C assimilates to the residual stubble and its axillary buds were significantly improved at the mature stage of the main crop, while the translocation rate to roots and rhizosphere soil was reduced at the later growth stage of ratooning season rice. This was triggered by the metabolism of hormones and polyamines at the stem base regulated by the interaction of water and fertilizer at this time. We therefore suggest that to achieve a high yield of ratoon rice with low stubble height under mechanized harvesting, the timely application of nitrogen fertilizer is fundamental,coupled with moderate field drying for root-vigor preservation and tiller promotion before and after the mechanical harvesting of the main crop.

Integrated assessment of yield,nitrogen use efficiency and ecosystem economic benefits of use of controlled-release and common urea in ratoon rice production

Controlled-release urea(CRU)is commonly used to improve the crop yield and nitrogen use efficiency(NUE).However,few studies have investigated the effects of CRU in the ratoon rice system.Ratoon rice is the practice of obtaining a second harvest from tillers originating from the stubble of the previously harvested main crop.In this study,a 2-year field experiment using a randomized complete block design was conducted to determine the effects of CRU on the yield,NUE,and economic benefits of ratoon rice,including the main crop,to provide a theoretical basis for fertilization of ratoon rice.The experiment included four treatments:(i)no N fertilizer(CK);(ii)traditional practice with 5 applications of urea applied at different crop growth stages by surface broadcasting(FFP);(iii)one-time basal application of CRU(BF1);and(iv)one-time basal application of CRU combined with common urea(BF2).The BF1 and BF2 treatments significantly increased the main crop yield by 17.47 and 15.99%in 2019,and by 17.91 and 16.44%in 2020,respectively,compared with FFP treatment.The BF2 treatment achieved similar yield of the ratoon crop to the FFP treatment,whereas the BF1 treatment significantly increased the yield of the ratoon crop by 14.81%in 2019 and 12.21%in 2020 compared with the FFP treatment.The BF1 and BF2 treatments significantly improved the 2-year apparent N recovery efficiency,agronomic NUE,and partial factor productivity of applied N by 11.47-16.66,27.31-44.49,and 9.23-15.60%,respectively,compared with FFP treatment.The BF1 and BF2 treatments reduced the chalky rice rate and chalkiness of main and ratoon crops relative to the FFP treatment.Furthermore,emergy analysis showed that the production efficiency of the BF treatments was higher than that of the FFP treatment.The BF treatments reduced labor input due to reduced fertilization times and improved the economic benefits of ratoon rice.Compared with the FFP treatment,the BF1 and BF2 treatments increased the net income by 14.21-16.87 and 23.76-25.96%,respectively.Overall,the one-time blending use of CRU and common urea should be encouraged to achieve high yield,high nitrogen use efficiency,and good quality of ratoon rice,which has low labor input and low apparent N loss.

RSD防控设施土壤和蔬菜连作障碍机制及应用的研究进展

强还原土壤灭菌法(Reductive soil disinfestation,RSD)作为一种环境友好型方法,能够杀灭土传病原菌并改善土壤理化性质,已成功用于设施土壤和蔬菜连作障碍防控。为给RSD防控土壤连作障碍的机制与应用研究提供理论参考,综述了RSD防控土壤连作障碍机制研究进展,介绍了近年来RSD在设施土壤与蔬菜生产方面的具体应用,并对今后RSD的研究与应用进行了展望。

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.

Improved Yield Prediction of Ratoon Rice Using Unmanned Aerial Vehicle-Based Multi-Temporal Feature Method

Pre-harvest yield prediction of ratoon rice is critical for guiding crop interventions in precision agriculture.However,the unique agronomic practice(i.e.,varied stubble height treatment)in rice ratooning could lead to inconsistent rice phenology,which had a significant impact on yield prediction of ratoon rice.Multi-temporal unmanned aerial vehicle(UAV)-based remote sensing can likely monitor ratoon rice productivity and reflect maximum yield potential across growing seasons for improving the yield prediction compared with previous methods.Thus,in this study,we explored the performance of combination of agronomic practice information(API)and single-phase,multi-spectral features[vegetation indices(VIs)and texture(Tex)features]in predicting ratoon rice yield,and developed a new UAV-based method to retrieve yield formation process by using multi-temporal features which were effective in improving yield forecasting accuracy of ratoon rice.The results showed that the integrated use of VIs,Tex and API(VIs&Tex+API)improved the accuracy of yield prediction than single-phase UAV imagery-based feature,with the panicle initiation stage being the best period for yield prediction(R^(2) as 0.732,RMSE as 0.406,RRMSE as 0.101).More importantly,compared with previous multi-temporal UAV-based methods,our proposed multi-temporal method(multi-temporal model VIs&Tex:R^(2) as 0.795,RMSE as 0.298,RRMSE as 0.072)can increase R^(2) by 0.020-0.111 and decrease RMSE by 0.020-0.080 in crop yield forecasting.This study provides an effective method for accurate pre-harvest yield prediction of ratoon rice in precision agriculture,which is of great significance to take timely means for ensuring ratoon rice production and food security.

皖中不同类型再生稻品种产量与温光资源利用特征分析

为探究皖中地区不同类型再生稻的生长发育与温光资源利用特征,为再生稻品种选择和周年稻作模式搭配提供参考,本研究以早熟籼型常规稻、早熟籼型杂交稻、中熟籼型杂交稻和籼粳杂交稻4个类型的8个代表品种为供试材料,监测不同类型再生稻的产量和全生育期气象要素情况。结果显示,中熟籼型杂交稻品种作再生稻时产量[(12.47±0.24)t·hm^(-2)]、光能生产效率[(0.40±0.01)g·MJ^(-1)]和有效积温(≥10℃)生产效率[(4.35±0.10)kg·hm^(-2)·℃^(-1)·d^(-1)]最高,可通过较高的日产量和适度较长的生育期促进高产形成。早熟籼型常规稻和早熟籼型杂交稻较中熟籼型杂交稻和籼粳杂交稻的再生季成熟期提前24~47 d,可用于后茬作物的温光资源更充裕。综上,选择中熟籼型杂交稻品种做再生稻时,温光资源利用效率和产量最高;选择早熟籼型常规稻和早熟籼型杂交稻作再生稻时,可搭配的轮作模式最多。

冬水田轻简化栽培杂交稻蓄留再生稻产量形成特点

【目的】轻简化栽培水稻因具有良好的社会、经济和环境效益而受到了广泛的关注。探明再生稻系统下轻简化栽培对杂交稻头季、再生季产量形成特点的影响,可为再生稻轻简化栽培提供理论依据。【方法】于2021-2022年在四川省典型再生稻区泸州进行大田试验,以7个杂交稻(益两优94、德优6699、泰优1060、蓉7优680、乐3优2275、德优727、锦丰优727)和1个常规稻(金农丝苗)为材料,研究两种栽培方式(免耕直播、免耕抛秧)对杂交稻头季、再生季产量形成特点的影响。【结果】栽培方式和品种基因型对杂交稻头季、再生季及两季总产量影响显著。与免耕抛秧相比,免耕直播头季、再生季及两季总产量分别增加了3.52%~7.37%、18.94%~47.37%、7.04%~14.93%,免耕直播杂交稻蓄留再生稻的增产优势主要表现在有效穗数、结实率、干物质积累量和收获指数上。不同基因型杂交稻头季产量以泰优1060、锦丰优727较高,再生季产量及两季总产量则以泰优1060最高。从2年平均值来看,高产杂交稻(德优6699、泰优1060、德优727、锦丰优727)头季、再生季以及两季总产量分别为8.80、2.53、11.33t/hm^(2),较中低产杂交稻(益两优94、蓉7蓉680、乐3优2275)分别增加了13.54%、6.03%、11.76%;比高产常规稻(金农丝苗)分别增加了9.97%、21.87%、12.41%。与高产常规稻相比,中低产杂交稻头季产量平均降低了3.15%,但其再生季及两季总产量则分别平均增加了14.94%、0.58%。从产量构成来看,高产杂交稻头季、再生季的有效穗数、千粒重均高于高产常规稻。从干物质生产来看,与高产常规稻相比,高产杂交稻头季和再生季成熟期的干物质量、收获指数分别平均增加3.82%和11.16%、5.45%和5.70%。中低产杂交稻头季成熟期干物质积累量低于高产常规稻是其减产的主要原因。【结论】再生稻系统下免耕直播相对于免耕抛栽有明显的增产优势,是其源库协调的一种良好响应。综合考虑再生季产量与两季总产量,四川省冬水田区再生稻轻简化高产栽培适宜选用分蘖能力强、千粒重大的杂交稻品种。

强宿根高产高糖甘蔗新品种云蔗101666的选育与评价

【目的】适应蔗糖产业发展的需求,选育宿根性好的高产高糖甘蔗新品种,保障蔗农和糖企利益,为云南和中国蔗糖产业的可持续发展提供品种支持。【方法】以‘桂糖96-167’为母本、‘崖城93-26’为父本进行甘蔗有性杂交,通过“五圃制”选育程序,经区试试验综合考察‘云蔗101666’的形态特征和生产性状。【结果】‘云蔗101666’蔗茎均匀,株型紧凑直立,中至中大茎,脱叶性好;2017—2019年区试试验中11—3月的蔗糖分分别为:12.80%、14.97%、16.26%、17.09%、17.37%,全期平均蔗糖分达15.46%,比‘新台糖22号’高出0.71个百分点;平均蔗茎产量121.32 t/hm^(2),较‘新台糖22号’增产22.50%;平均糖产量18.67 t/hm^(2),比‘新台糖22号’增产29.20%。该品种中抗黑穗病和条纹花叶病,感高粱花叶病,于2020年7月获植物新品种权。【结论】‘云蔗101666’为中早熟、高产、高糖品种,其抗旱性强,宿根性好,脱叶性佳,适宜在云南德宏、版纳、临沧、富宁蔗区海拔900~1400 m甘蔗产区中等以上肥力的的旱坡地、台地种植。

江汉平原典型种植模式稻田土壤中农药残留特征

在江汉平原中稻-油菜/小麦轮作田、一季中稻田及再生稻田3种种植模式稻田采集土壤样品86个。调查了土壤样品中滴滴涕(DDTs,包括o,p′-DDT、p,p′-DDT、p,p′-DDE、p,p′-DDD)、六六六(HCHs,包括α-HCH、β-HCH、γ-HCH、δ-HCH)、甲胺磷、甲基对硫磷、氧乐果、乐果、敌敌畏、乙酰甲胺磷、毒死蜱、氯虫苯甲酰胺、吡蚜酮、吡虫啉、啶虫脒、三环唑、戊唑醇、氰氟草酯、二氯喹啉酸、乙草胺及异丙甲草胺等25种农药及其代谢产物的残留。结果表明,检出率最高的3种农药为当前常用杀虫剂氯虫苯甲酰胺(87.21%),杀菌剂三环唑(91.86%)及戊唑醇(72.09%),其残留均值分别为0.0397、0.0734 mg/kg及0.0276 mg/kg;已经禁用的有机氯农药滴滴涕(o,p′-DDT、p,p′-DDT、p,p′-DDE、p,p′-DDD)仍能检出,检出率为36.05%~66.28%。3种模式田块中检出的滴滴涕主要来源于历史上滴滴涕的使用。杀虫剂吡蚜酮及杀菌剂三环唑在再生稻田的残留量均值显著高于中稻-油菜/小麦轮作田及一季中稻田;但其他农药在不同种植模式稻田中的残留没有显著差异。本研究为江汉平原农药残留的治理及农药的合理使用提供了参考信息。

气候变化对川渝地区再生稻产业的影响与建议——以富顺县为例

2022—2023年以田间调查、电话访谈、文献查阅和专家座谈等方式对川渝地区再生稻生产情况进行了调研,统计分析了气候变化下川渝再生稻种植区生产格局变化和发展趋势,以富顺县为例,剖析了川渝地区再生稻产业发展的潜力和面临的挑战,并就如何提升再生稻气候韧性提出5条建议。调研显示,在气候变暖情况下,川渝地区秋季热量资源更加丰富,再生稻种植呈现适生区、优生区面积不断增加、产量稳步提高等有利变化;但气象灾害呈重发趋势,再生稻生产气候风险增高。富顺县为再生稻种植优生区,具有自然条件、技术、品种、历史、品牌、需求和政策等优势。随着再生稻产业的迅猛发展和极端天气频发重发,提高应对气候变化能力、加强再生稻气候韧性建设,对加快推进川渝地区再生稻产业发展和品牌建设具有重要的现实意义。

福建省再生稻的生产现状及其增产潜力与发展对策

再生稻播一茬收两茬,具有生长期短、病虫害少、米质好等优点,是提高复种指数、增加粮食产量和种粮收入的重要措施。福建是中国最适宜种植再生稻的省份之一,绝大部分县市都可以种植再生稻。本研究分析了福建省再生稻发展现状及存在的主要问题,阐述了福建省发展再生稻的优势所在与增产潜力,提出了促进再生稻发展与粮食产能的思路与对策建议,以求为优化福建省再生稻产业高质量发展体系提供参考与借鉴。

谷优676在尤溪县作再生稻种植的特征特性及高效栽培技术

谷优676是福建兴禾种业科技有限公司、福建省农业科学院水稻研究所、福建禾丰种业股份有限公司用谷丰A与福恢676杂交选育的品种,2017年通过福建省农作物品种审定委员会审定。谷优676连续3 a在尤溪县作再生稻示范种植,具有高产、抗病、熟相好、抗逆性和再生力强等特点。总结了谷优676作再生稻种植的高产高效生产关键技术。

稻—再生稻—小龙虾稻田综合种养经济效益分析

为充分利用光温资源,在稻—小龙虾种养模式的基础上,进行稻虾综合种养,与再生稻种植相结合,开展稻—再生稻—小龙虾综合种养技术模式研究。设置4种种养模式,分别是种植中稻(MR)、种植再生稻(RR)、中稻—小龙虾综合种养(MRC)和稻—再生稻—小龙虾综合种养(RRC),分析不同种养模式对稻虾产量和经济效益的影响。结果表明,(1)RR的全年水稻产量均高于MR产量,再生季稻的产量约为头季稻产量的1/4,RRC模式水稻产量最高。(2)MRC和RRC模式养虾田水稻产量的提高主要通过较高的穗粒数和千粒重来实现。(3)稻—再生稻—小龙虾综合种养模式的产值、利润和产投比均最高,分别为102754元//hm^(2)、64704元//hm^(2)和2.70。综合来看,稻虾综合种养模式与再生稻模式相结合,能提高稻谷总产量,降低生产成本,具有较好的经济效益,是一种资源高效型、环境友好型的种养方式。

甘蔗宿根关键性状及其在宿根性快速评价中的应用

甘蔗重要性状宿根性因甘蔗生长周期长,其高效评价一直是研究的难点。本研究以国内外不同地区引进的212份甘蔗种质资源为研究材料,分别在广西隆安和云南开远开展基于2个重要宿根关键性状(宿根发株率和地上部蔗株生物量)两季宿根力的快速评价。结果表明甘蔗宿根力受环境影响较大,两个试验点所有宿根力指标均存在极显著差异,且指标之间均呈极显著正相关。主成分分析在两个试验点(云南开远和广西隆安)均仅提取到1个主成分,贡献率分别为80.25%和62.68%。聚类分析将212份种质分为5个类群,第Ⅰ类4个宿根力指标均处于高水平,有9份种质,可作为强宿根第一梯队资源;第Ⅱ类群、第Ⅲ类群共有38份种质,各宿根力指标均处于较高水平或个别宿根力指标非常突出,可作为强宿根第二梯队资源;第Ⅳ类群、第Ⅴ类共有165份种质资源,各宿根力指标均一般或较差。综合以上,利用筛选出来的强宿根资源改良甘蔗品种宿根性,降低甘蔗生产成本对于产业的可持续发展具有重要意义。

甘蔗宿根矮化病(RSD)温水脱菌研究

为寻求甘蔗宿根矮化病（RSD）的有效防控技术和方法，本研究根据甘蔗RSD的传播危害特点，选择五大主栽品种，采用温水处理设备对带菌蔗种进行温水（50±0．2℃）脱菌处理2h，分析研究温水处理对甘蔗RSD的脱菌效果。结果表明：温水（50±0．2℃）脱菌处理2h能有效去除甘蔗RSD，去除率为90％以上。与常规种苗相比，脱菌种苗在整个生长期中都表现出明显的生长优势，早生快发、伸长拔节早、长相健壮。粤糖93／159、ROC25号、ROC10号、闽糖69／421、桂糖17号5大主栽品种经温水脱菌处理均具有显著的增产增糖效果：新植增产甘蔗5．01～49．83t／hm^2，增幅5．97％-91．31％；甘蔗蔗糖分提高0．07％～0．86％（绝对值）。可见，种植温水脱菌种苗是防治甘蔗RSD最经济有效的措施，在生产上应加快推广，使之制度化，可大幅度提高甘蔗的产量和糖分，延长宿根年限，从而显著提高甘蔗生产的经济效益。

RSD开关在脉冲电源中的应用研究

该文提出应用RSD(Reversely Switched Dynistor)设计脉冲功率电源的方法,并在应用RSD设计脉冲电源过程中对两种关键元件磁开关和脉冲变压器进行了重点设计,确定回路参数配合原则。在3种典型触发方式的RSD脉冲电源基础上,提出了RSD端电压翻转式触发电路,以提高RSD的触发效率,采用了阻尼衰减模型的设计方法消除主回路放电过程中出现的振荡。对该电源放电脉冲压缩形成回路模型进行了设计分析,并对其和共触发电路进行了设计仿真。对所提出的触发RSD方式的脉冲电源设计方法进行了试验验证分析和仿真验证分析,证明了设计方法的正确性。

超高速半导体开关RSD的开通机理与大电流特性研究

基于反向注入控制RSD(ReverselySwitchedDynistor)的大面积快速均匀开通、可无限串联、功率大、换流效率高、寿命长的特点,新开通机制的RSD将在脉冲功率技术中获得重要应用。本文研究了RSD的开通机理和开通条件,为器件开通特性的改进和预充电路的合理设计提供了依据;实验还表明,由小直径RSD的极限电流测试结果,可以用经验公式得到同类结构的任意通流面积RSD脉冲大电流耐量。

甬优籼粳杂交稻作再生稻种植的再生特性及产量形成分析

为探究甬优籼粳杂交稻作再生稻种植时的再生特性及产量形成特点,以生产上应用广泛的甬优籼粳杂交稻品种甬优1540和甬优4949为试验材料、籼型杂交稻品种隆两优534为对照材料作再生稻种植进行了田间试验。结果显示:籼粳杂交稻和籼型杂交稻2个类型品种的再生特性存在显著差异;籼粳杂交稻甬优1540和甬优4949的优势再生节位为低节位的倒5节和倒4节,2个节位的再生苗有效穗占比之和分别为81.9%和68.9%,产量贡献率之和分别为89.6%和72.5%;2个节位再生稻的穗长、每穗粒数显著高于倒3节和倒2节,并呈现出从下往上节位逐步变小的趋势;而籼型杂交稻品种隆两优534的优势再生节位则是高节位的倒2节和倒3节,2个节位的有效穗占比和产量贡献率之和分别为71.5%和72.5%;甬优4949头季稻收割后1~7 d内的再生苗的成穗率、有效穗占比和产量贡献率分别为89.4%、74.6%和79.2%,均显著高于收割后8~12 d和12 d以上的再生苗;甬优1540和甬优4949再生稻的穗长、每穗粒数均要显著大于隆两优534,产量分别增产21.6%和17.3%。结果表明甬优籼粳杂交稻的低节位强再生力和再生苗穗大粒多的再生特性是其作再生稻种植时易获得高产的主要因素。

空心线圈用于RSD开关电流测量

首先分析了高压大功率RSD开关电流的特点,确认了空心线圈测量方法。在比较空心线圈传感器自积分和外积分主要性能的基础上,对测量中相位误差的影响作了进一步研究分析。针对上升时间为微秒量级且含有低频分量的RSD开关电流,提出了调控相差的外积分测量方案。实际测量证明:调控相差的外积分测量法能较好地满足RSD开关电流测量的要求。