齐穗后遮阴时长对西北稻区粳稻产量和品质的影响

灌浆期光照强度对保障水稻产量和稻米品质至关重要。本研究以常规高产水稻品种(新稻41、吉粳88)和优质水稻品种(粮粳10号、吉粳515)作为研究对象,以不遮阴作为对照,于2018和2019年在新疆乌鲁木齐研究了齐穗后不同遮阴时长处理(遮阴10 d、20 d和持续遮阴)对水稻产量及稻米品质的影响。结果表明,齐穗后遮阴延长了水稻灌浆进程,降低了结实率、千粒重和产量;遮阴同时导致了籽粒直链淀粉含量显著降低,蛋白质含量显著增加,进而导致水稻垩白粒率和垩白度增加,淀粉糊化特性和食味值变差。与不遮阴相比,齐穗后遮阴10 d、20 d和持续遮阴处理2年平均水稻结实率和千粒重分别下降了3.5%、9.7%、11.1%和3.7%、7.1%、13.1%,进而导致产量分别下降了11.3%、16.5%和31.7%。直链淀粉含量和食味值受齐穗后0~10 d遮阴的影响不大,齐穗后遮阴20 d和持续遮阴处理较对照2年平均籽粒蛋白质含量分别增加了20.5%和30.8%,直链淀粉含量降低了3.6%和4.6%,崩解值和食味值分别降低了15.2%、26.1%和3.9%、7.7%。籽粒垩白粒率受齐穗后遮阴的影响因灌浆期背景光照强度而异, 2018年齐穗后遮阴10 d水稻垩白粒率增幅最大,达152.1%, 2019年为齐穗后遮阴20 d增幅最大,达345.5%。高产水稻品种对齐穗后遮阴时长的敏感程度大于优质水稻品种,其结实率和千粒重下降幅度更大,产量更易受遮阴的影响;并且高产水稻品种垩白粒率增加幅度明显大于优质水稻品种,导致其更易受遮阴影响。综上,齐穗后20d是遮阴影响稻米外观品质的关键时期,且遮阴时长的影响取决于背景光照强度;遮阴时间越长,稻米蒸煮食味品质越差。本研究将为我国优质粳稻生产应对未来气候变化提供科学依据。

长期有机无机肥配施降低黄淮海区域小麦-大豆复种系统净温室效应

【目的】小麦-大豆系统是黄淮海区域重要的禾豆复种系统,综合评价该系统的净碳排放对于我国农田固碳减排具有重要意义。借助30年的长期定位试验,综合评价不同施肥处理下小麦-大豆复种系统的产量和净碳排放,旨在为该系统丰产低碳排放的施肥制度创新提供理论依据。【方法】试验包括单施牛粪(M)、氮磷钾平衡施肥(NPK)、氮磷钾加牛粪(NPKM)、氮磷加秸秆(NPS)、氮磷钾加饼肥(NPKC)、氮磷钾加牛粪及饼肥(NPKMC)以及不施肥对照(CK),共7个处理。综合分析了各处理田间直接温室气体排放(N2O和CH4)、农田投入导致的间接碳排放与土壤有机碳固定,估算了单施牛粪、单施化肥以及化肥与不同有机物料配施的净碳排放,同时将碳排放与作物产量和土壤有机质相结合,综合评价了不同施肥措施下的净温室效应。【结果】小麦-大豆复种系统中,小麦季施肥对大豆产量有显著后效,与单施NPK相比,NPKM、NPKC和NPKMC处理分别使大豆产量提高了31.0%、16.8%和24.0%,而M和NPS处理不利于大豆、小麦产量的提高。与NPK处理相比,M、NPKM、NPKMC处理的农田直接温室气体排放分别增加了49.4%、17.7%和12.4%,土壤有机碳年固定量分别显著提高了282.2%、137.3%和169.1%。M及NPKM处理的间接碳排放与NPK处理没有明显差异,而其他施肥处理的间接碳排放低于NPK处理。在各施肥处理中,由肥料投入导致的碳排放占总间接碳排放的比例最大,其次是灌溉用电和机械用柴油导致的碳排放。对净碳排放的估算结果表明,M处理的净碳排放为负值(表现为碳汇),而其他处理下小麦-大豆复种系统均表现为碳源,NPK与有机物料配施的处理净碳排放显著低于NPK处理。此外,与NPK处理相比,NPK与有机物料配施使碳排放强度显著降低了36.5%~113.2%,使单位土壤有机质提升的温室气体排放(δGHG/δSOM)降低了69.4%~93.2%。【结论】黄淮海区域小麦-大豆复种系统中,氮磷钾配施有机肥(牛粪或饼肥)可在保证小麦和大豆产量的同时,降低小麦-大豆复种系统的净温室效应。

我国作物生产碳排放特征及助力碳中和的减排固碳途径

作物生产不仅保障了国家粮食安全,也是农业碳排放的主要源,以及碳固定的重要汇。阐明主要农区作物生产碳排放特征,探讨其达峰与中和途径,可以为全国及地方作物生产绿色高质量发展和农业“双碳”目标的战略制定提供重要科学依据。本文基于国家统计数据,比较分析了我国各地区作物生产碳排放特征,探讨了助力碳中和的农田减排固碳途径。2018年我国作物生产碳排放占全国农业碳排放总量45.5%,其中农田甲烷(CH_(4))、氧化亚氮(N_(2)O)以及农用柴油消费的二氧化碳(CO_(2))排放分别占农业碳排放总量的22.9%、14.7%和7.9%。从区域排放来看,作物生产碳排放总量和单位播种面积排放量均呈现南高北低特征,其中以华东和华中地区最高,减排潜力大。在作物生产碳排放中,稻田CH_(4)占50.3%,是减排重点。我国作物生产碳排放总量于2015年出现峰值,之后呈现下降趋势,这与水稻播种面积、农田氮肥用量和农用柴油消费等减少趋势相一致。可见,如果我国农产品进口不受显著影响,作物生产碳排放已经呈现达峰趋势。情景推算发现,仅靠农地土壤固碳很难实现作物生产的碳中和,需要农田减排与固碳的兼顾。在丰产稳产前提下,作物生产碳中和要以稻田CH_(4)和旱地N_(2)O减排优先,在增强土壤碳汇功能的同时,充分挖掘秸秆资源化利用、用地养地结合和农田林网建设等农田生态系统的综合固碳潜力。

田间开放式增温对东北水稻氮素利用的影响

东北地区是全球气候变暖趋势最为显著的地区之一,研究预期增温对东北水稻氮素吸收利用的影响,可为区域水稻可持续生产与氮肥优化管理提供借鉴。本研究于2019—2020年在黑龙江省哈尔滨市设置田间开放式增温(free air temperature increase,FATI)系统,大田与盆栽试验相结合,采用^(15)N同位素示踪技术,模拟预期增温(+1.5℃)对水稻产量、氮素利用以及氮肥去向的影响。结果表明,增温促进了水稻地上部干物质积累,与对照相比,大田与盆栽的水稻产量2年平均分别提高10.4%和10.8%;增温显著提高了水稻氮素吸收总量,与对照相比,2年平均增幅达21.3%,但增温处理的氮素籽粒利用效率呈降低趋势;增温处理下水稻从肥料中吸收的氮素显著下降,但从土壤中吸收的氮素显著增加31.1%,导致氮肥回收率降低12.5%,而氮肥损失率增加14.2%。总体来看,增温有增加水稻籽粒产量的趋势,但降低了水稻对肥料氮的吸收比例,导致氮素利用效率降低,氮肥损失率显著增加。在气候变暖背景下,建议合理增加水稻移栽密度,以充分利用温度升高对水稻产量的正向效应,适当减少氮肥施用量、优化氮肥运筹管理,提高水稻氮素利用效率。

农艺措施减控稻田甲烷和氧化亚氮排放的研究进展

综述了秸秆还田、生物炭还田、水分管理、施肥管理和种植制度等农艺措施对CH4和N2O两种气体排放影响的研究成果,不同农艺措施对其影响各不相同;分析了造成促进或抑制效应的可能机理,不同农艺措施均是通过影响CH4和N2O的产生、转化过程来影响CH4和N2O排放;并提出了进一步的研究展望,以期为减控稻田温室气体排放和实现资源高效利用与环境友好型耕作制度提供参考依据。

How plant density affects maize spike differentiation, kernel set, and grain yield formation in Northeast China?

A two-year field experiment was conducted to evaluate the effects of plant density on tassel and ear differentiation, anthesissilking interval(ASI), and grain yield formation of two types of modern maize hybrids(Zhongdan 909(ZD909) as tolerant hybrid to crowding stress, Jidan 209(JD209) and Neidan 4(ND4) as intolerant hybrids to crowding stress) in Northeast China. Plant densities of 4.50×104(D1), 6.75×104(D2), 9.00×104(D3), 11.25×104(D4), and 13.50×104(D5) plants ha-1had no significant effects on initial time of tassel and ear differentiation of maize. Instead, higher plant density delayed the tassel and ear development during floret differentiation and sexual organ formation stage, subsequently resulting in ASI increments at the rate of 1.2–2.9 days on average for ZD909 in 2013–2014, 0.7–4.2 days for JD209 in 2013, and 0.5–3.7 days for ND4 in 2014, respectively, under the treatments of D2, D3, D4, and D5 compared to that under the D1 treatment. Total florets, silking florets, and silking rates of ear showed slightly decrease trends with the plant density increasing, whereas the normal kernels seriously decreased at the rate of 11.0–44.9% on average for ZD909 in 2013–2014, 2.0–32.6% for JD209 in 2013, and 9.7–28.3% for ND4 in 2014 with the plant density increased compared to that under the D1 treatment due to increased florets abortive rates. It was also observed that 100-kernel weight of ZD909 showed less decrease trend compared that of JD209 and ND4 along with the plant densities increase. As a consequence, ZD909 gained its highest grain yield by 13.7 t ha-1on average at the plant density of 9.00×104 plants ha-1, whereas JD209 and ND4 reached their highest grain yields by 11.7 and 10.2 t ha-1at the plant density of 6.75×104 plants ha-1, respectively. Our experiment demonstrated that hybrids with lower ASI, higher kernel number potential per ear, and relative constant 100-kernel weight(e.g., ZD909) could achieve higher yield under dense planting in high latitude area(e.g., Northeast China).

Super Rice Cropping Will Enhance Rice Yield and Reduce CH_4 Emission:A Case Study in Nanjing,China

A pot experiment was performed to learn the differences in plant productivity and OH4 emission between two rice cultivars, super rice variety Ningjing 1 and traditional variety Zhendao 11, which were currently commercially appUed in Nanjing, China. Similar seasonal changes of CH4 emission fluxes and soil solution CH4 contents were found between the tested cultivars. Although there was no significant difference in plant biomass production between the cultivars, the grain yield of Ningjing 1 was significantly higher by 35.0% （P 〈 0.05） than that of Zhendao 11, whereas the total CH4 emission from Ningjing 1 was 35.2% lower （P 〈 0.05）. The main difference in the amounts of CH4 emission between the cultivars occurred in the period from the tillering stage to the heading stage. The biomass-scaled and yield-scaled CH4 emissions were respectively 3.8 and 5.2 mg/g for Ningjing 1, significantly lower than those for Zhendao 11 （7.4 and 12.8 mg/g, respectively）. According to the relationships between the plant growth characteristics and the CH4 emission, a stronger root system contributed mainly to the lower CH4 emission of Ningjing 1, as compared with Zhendao 11. Our results demonstrated that super rice has advantages not only in grain productivity but also in CH4 emission mitigation. Further expansion of super rice cropping will enhance rice yield and reduce greenhouse gas emission in China.

Estimation of soil organic carbon stock and its controlling factors in cropland of Yunnan Province,China

Soil organic carbon(SOC)is the most important indicators of soil quality and health.Identifying the spatial distribution of SOC and its influencing factors in cropland is crucial to understand the terrestrial carbon cycle and optimize agronomic management.Yunnan Province,characterized by mountainous topography and varied elevation,is one of the highest SOC regions in China.Yet its SOC stock of cropland and influencing factors has not been fully studied due to the lack of adequate soil investigation.In this study,the digital mapping of SOC at 1 km resolution and the estimation of total SOC stock in cropland of Yunnan Province was undertaken using 8637 topsoil(0-20 cm)samples and a series of spatial data through Random Forest(RF)model.It was showed that across the cropland of Yunnan Province,the mean SOC density and total stock were 4.84 kg m^(-2) and 337.5 Mt,respectively.The spatial distribution indicated that relatively high SOC density regions resided in the northwest and northeast parts of Yunnan Province.Elevation(19.5%),temperature(17.3%),rainfall(14.5%),and Topographic wetness index(9.9%)were the most important factors which controlled spatial variability of SOC density.Agronomic practices(e.g.,crop straw treatments,fertilizer management)should be optimized for the sustainable development of crop production with high SOC sequestration capacity in Yunnan Province.

Impacts of Nighttime Warming on the Soil Nematode Community in a Winter Wheat Field of Yangtze Delta Plain, China

Changes in the soil nematode community induced by global warming may have a considerable influence on agro-ecosystem functioning. However, the impacts of predicted warming on nematode community in farmland （e.g., winter wheat field） have not been well documented. Therefore, a field experiment with free air temperature increase （FATI） was conducted to investigate the responses of the soil nematode community to nighttime warming in a winter wheat field of Yangtze Delta Plain, China, during 2007 to 2009. Nighttime warming （NW） by 1.8~C at 5-cm soil depth had no significant impact on the total nematode abundance compared to un-warmed control （CK）. However, NW significantly affected the nematode community structure. Warming favored the bacterivores and fungivores, such as Acrobeles, Monhystera, Rhabditis, and Rhabdontolaimus in bacterivores, and Filenchus in fungivores, while the plant-parasites were hindered, such as Helicotylenchus and Psilenchus. Interestingly, the carnivores/ omnivores remained almost unchanged. Hence, the abundances ofbacterivores and fungivores were significantly higher under NW than those under CK. Similarly, the abundances of plant-parasites were significantly lower under NW than under CK. Furthermore, Wasilewska index of the nematode community was significantly higher under NW than those under CK, indicating beneficial effect to the plant in the soil. Our results suggest that nighttime warming may improve soil fertility and decrease soil- borne diseases in winter wheat field through affecting the soil nematode community. It is also indicated that nighttime warming may promote the sustainability of the nematode community by altering genera-specific habitat suitability for soil biota.

丛枝菌根真菌对豆科作物生长和生物固氮及磷素吸收的影响

本研究以大豆为材料,采用盆栽和田间试验,探讨丛枝菌根真菌(AMF)对豆科作物生长的影响。盆栽试验设置了接种(+AMF)和不接种(-AMF)丛枝菌根真菌处理,田间试验设置了AMF菌丝非限制与限制处理。盆栽试验结果表明:接种AMF显著提高了大豆地上部生物量(16.5%)和大豆根瘤数(131.4%),地上部磷含量、磷吸收量、氮含量和氮吸收量也显著增加。田间试验中,AMF菌丝非限制处理下大豆的地上部生物量、根系生物量、根瘤数量分别比限制处理下显著提高了123.6%、61.5%和212.5%,地上部和根系磷吸收量、氮含量、氮吸收量均显著高于限制处理,大豆根际土壤速效氮和有效磷含量也均显著高于限制处理。本研究可为进一步认识豆科作物与AMF的共生关系及田间磷肥高效利用提供理论参考。