种植密度对两种穗型冬小麦旗叶氮代谢酶活性及籽粒蛋白质含量的影响

目的分析晚播对弱筋小麦氮素积累与利用的影响。方法以弱筋小麦品种扬麦13和宁麦13为材料,在不同氮素水平下(N210：210 kg/hm²、N270：270 kg/hm²)设置适播与晚播处理,分析弱筋小麦氮素积累与利用情况。结果弱筋小麦开花期植株氮素积累量主要来源于土壤氮(70.48%~85.51%);成熟期籽粒氮素积累量主要来源于土壤氮(74.35%~86.86%);成熟期营养器官氮素积累主要来源于肥料氮(52.88%~82.12%)。与适期播种相比,晚播显著增加了小麦成熟期单株氮素积累量、开花期来源于土壤氮的积累量、成熟期营养器官和籽粒来源于土壤氮及肥料氮的积累量。弱筋小麦花前营养器官积累氮素向籽粒的转运率为55.52%~79.78%,氮素积累转移的贡献率为38.91%~77.99%。适期播种处理下,花前营养器官氮素积累转运量、转运率与贡献率分别为23.47 mg/株、75.23%和71.46%,而晚播显著降低花前营养器官氮素积累转运量、转运率与贡献率(分别为19.87 mg/株、59.74%和50.31%)。各处理小麦氮肥生产效率为25.25~44.27 kg/kg,氮素利用效率为15.75%~41.43%,氮素收获指数为0.730~0.844。同一因素下不同水平比较表明：晚播显著降低籽粒产量、氮肥生产效率、氮素利用效率及氮素收获指数,但播期对籽粒蛋白质含量无显著影响。在相同品种和氮水平处理下,晚播较适期播种籽粒产量降低。结论弱筋小麦晚播不利于籽粒产量的提高和氮素利用效率的提高,因此为获得较高产量水平与氮素利用效率,应尽量保证弱筋小麦适宜播种期。     

施用生物炭对华北平原冬小麦土壤水分和籽粒产量的影响

为探究施用生物炭对华北平原农田土壤水分和冬小麦籽粒产量的影响,于2014—2017年在中国农业大学吴桥实验站设置施用生物炭7 200(BH)、3 600(BM)、1 800(BL)和0kg/hm~2(CK)4个处理。结果表明:与CK处理相比,BH、BM和BL处理3年平均增产分别为1.84%、7.28%和5.03%,并且降低了耗水量,水分利用效率分别提高5.96%～14.86%、9.42%～19.18%和5.96%～13.50%。同时施用生物炭增加了土壤含水量,与CK处理相比,土壤上层0～60cm BM处理增幅最大;中层60～120cm和下层120～200cm均为BL处理增幅最大(P0.05)。综上所述,施用生物炭可以增加土壤含水量和籽粒产量。统计分析表明,当施炭量分别为3 389～3 882和3 500～4 357kg/hm~2,0～60cm土层土壤含水量和籽粒产量均最高,且0～60cm土层土壤含水量与籽粒产量间存在显著的正相关关系(P0.05)。因此,施用生物炭可以增加土壤含水量,降低水分消耗,提高冬小麦籽粒产量和水分利用效率,在本试验条件下以施用3 000～4 500kg/hm~2为宜。     

Nitrate leaching of winter wheat grown in lysimeters as affected by fertilizers and irrigation on the North China Plain

Proper application of nitrogen(N) fertilizers and irrigation management are important production practices that can reduce nitrate leaching into groundwater and improve the N use efficiency(NUE). A lysimeter/rain shelter facility was used to study effects of the rate of N fertilization, type of N fertilizer, and irrigation level on key aspects of winter wheat production over three growing seasons(response variables were nitrate transport, N leaching, and NUE). Results indicated that nitrate concentration in the soil profile and N leaching increased with the rate of N fertilization. At the end of the third season, nitrate concentration in the top 0–75 cm layer of soil was higher with manure treatment while urea treatments resulted in higher concentrations in the 100–200 cm layer. With normal irrigation, 3.4 to 15.3% of N from applied fertilizer was leached from the soil, yet no leaching occurred under a stress irrigation treatment. The manure treatment experienced less N leaching than the urea treatment in all cases except for the 180 kg N ha-1 rate in 2011–2012(season 3). In terms of grain yield(GY), dry matter(DM) or NUE parameters, values for the manure treatment were lower than for the urea treatment in 2009–2010(season 1), yet were otherwise higher for urea treatment in season 3. GY and crop nitrogen uptake(NU) were elevated when the rate of N fertilizer increased, while the NUE decreased; GY, DM, and NU increased with the amount of irrigation. Data indicated that reduced rates of N fertilization combined with increased manure application and proper irrigation management can lower nitrate levels in the subsoil and reduce potential N leaching into groundwater.     

烤烟节水灌溉的研究进展

目的明确云南玉溪烟区烤烟大田生育期适宜滴灌定额。方法2017年通过田间控水试验,以作物蒸散量(ET₀)为基础,设置4个参考需水量水平(50% ET₀、60% ET₀、80% ET₀和100% ET₀)和3个设计湿润比(P,0.4、0.5和0.6),共12个滴灌定额处理,考察不同滴灌定额对烤烟生长发育和水肥利用效率的影响。结果参考需水量水平对烤烟株高、茎干物质量以及氮肥和钾肥利用率有显著影响(P<0.05),对除株高以外的农艺性状、叶和全株干物质量以及灌溉水利用率有极显著影响(P<0.01);设计湿润比对烤烟叶干物质量、根冠比和灌溉水利用率有显著影响(P<0.05),对烤烟主要农艺性状、茎和全株干物质量有极显著影响(P<0.01);两者对烤烟叶片和全株干物质量以及灌溉水利用率的影响存在显著交互效应(P<0.05),对烤烟叶片数和株高的影响存在极显著交互效应(P<0.01)。不同灌溉定额处理中,以80% ET₀-0.5P处理烤烟成熟期生物量和农艺性状表现较优,氮、磷和钾肥及灌溉水利用率相对较高;与其他处理相比,其成熟期烤烟叶片和全株干物质量分别增加了14.6%~97.5%和4.3%~72.8%,氮肥和磷肥利用率分别提高了9.4%~84.2%和11.3%~178.1%。结论本试验条件下,该区域较为适宜的烤烟大田生育期滴灌灌溉定额为200 mm。     

Effects of water application uniformity using a center pivot on winter wheat yield,water and nitrogen use efficiency in the North China Plain

In recent years, the use of fertigation technology with center pivot irrigation systems has increased rapidly in the North China Plain(NCP). The combined effects of water and nitrogen application uniformity on the grain yield, water use efficiency(WUE) and nitrogen use efficiency(NUE) have become a research hotspot. In this study, a two-year field experiment was conducted during the winter wheat growing season in 2016–2018 to evaluate the water application uniformity of a center pivot with two low pressure sprinklers(the R3000 sprinklers were installed in the first span, the corresponding treatment was RS; the D3000 sprinklers were installed in the second span, the corresponding treatment was DS) and a P85 A impact sprinkler as the end gun(the corresponding treatment was EG), and to analyze its effects on grain yield, WUE and NUE. The results showed that the water application uniformity coefficients of R3000, D3000 and P85 A along the radial direction of the pivot(CU_H) were 87.5, 79.5 and 65%, respectively. While the uniformity coefficients along the traveling direction of the pivot(CU_C) were all higher than 85%. The effects of water application uniformity of the R3000 and D3000 sprinklers on grain yield were not significant(P0.05); however, the average grain yield of EG was significantly lower(P0.05) than those of RS and DS, by 9.4 and 11.1% during two growing seasons, respectively. The coefficients of variation(CV) of the grain yield had a negative correlation with the uniformity coefficient. The CV of WUE was more strongly affected by the water application uniformity, compared with the WUE value, among the three treatments. The NUE of RS was higher than those of DS and EG by about 6.1 and 4.8%, respectively, but there were no significant differences in NUE among the three treatments during the two growing seasons. Although the CU_H of the D3000 sprinklers was lower than that of the R3000, it had only limited effects on the grain yield, WUE and NUE. However, the cost of D3000 sprinklers is lower than that of R3000 sprinklers. Therefore, the D3000 sprinklers are recommended for winter wheat irrigation and fertigation in the NCP.     

Yield and water use responses of winter wheat to irrigation and nitrogen application in the North China Plain

With increasing water shortage resources and extravagant nitrogen application, there is an urgent need to optimize irrigation regimes and nitrogen management for winter wheat(Triticum aestivum L.) in the North China Plain(NCP). A 4-year field experiment was conducted to evaluate the effect of three irrigation levels(W1, irrigation once at jointing stage; W2, irrigation once at jointing and once at heading stage; W3, irrigation once at jointing, once at heading, and once at filling stage; 60 mm each irrigation) and four N fertilizer rates(N0, 0; N1, 100 kg N ha~(-1); N2, 200 kg N ha~(-1); N3, 300 kg N ha~(-1)) on wheat yield, water use efficiency, fertilizer agronomic efficiency, and economic benefits. The results showed that wheat yield under W2 condition was similar to that under W3, and greater than that under W1 at the same nitrogen level. Yield with the N1 treatment was higher than that with the N0 treatment, but not significantly different from that obtained with the N2 and N3 treatments. The W2 N1 treatment resulted in the highest water use and fertilizer agronomic efficiencies. Compared with local traditional practice(W3 N3), the net income and output-input ratio of W2 N1 were greater by 12.3 and 19.5%, respectively. These findings suggest that two irrigation events of 60 mm each coupled with application of 100 kg N ha~(–1) is sufficient to provide a high wheat yield during drought growing seasons in the NCP.     

Improved simulation of winter wheat yield in North China Plain by using PRYM-Wheat integrated dry matter distribution coefficient

The accurate simulation of regional-scale winter wheat yield is important for national food security and the balance of grain supply and demand in China. Presently, most remote sensing process models use the “biomass×harvest index(HI)” method to simulate regional-scale winter wheat yield. However, spatiotemporal differences in HI contribute to inaccuracies in yield simulation at the regional scale. Time-series dry matter partition coefficients(Fr) can dynamically reflect the dry matter partition...     

Improving water use efficiency in grain production of winter wheat and summer maize in the North China Plain: a review

Reducing irrigation water use by improving water use efficiency (WUE) in grain production is critical for the development of sustainable agriculture in the North China Plain (NCP). This article summarizes the research progresses in WUE improvement carried out at the Luancheng station located in the Northern part of NCP for the past three decades. Progresses in four aspects of yield and WUE improvement are presented, including yield and WUE improvement associated with cultivar selection, irrigation management for improving yield and WUE under limited water supply, managing root system for efficient soil water use and reducing soil evaporation by straw mulch. The results showed that annual average increase of 0.014 kg·m^-3 for winter wheat and 0.02 kg·m^-3 in WUE were observed for the past three decades, and this increase was largely associated with the improvement in harvest index related to cultivar renewal and an increase in chemical fertilizer use and soil fertility. The results also indicated that deficit irrigation for winter wheat could significantly reduce the irrigation water use, whereas the seasonal yield showed a smaller reduction rate and WUE was significantly improved. Straw mulching of summer maize using the straw from winter wheat could reduce seasonal soil evaporation by 30–40 mm. With new cultivars and improved management practices it was possible to further increase grain production without much increase in water use. Future strategies to further improve WUE are also discussed.     

精准农业对华北平原冬小麦温室气体排放和产量的短期影响

本试验以京郊冬小麦田为研究对象,采用大田试验设置4个处理:CTF(常规整地+常规施肥)、PF(精准施肥)、LL(激光平地)、PF+LL(精准施肥+激光平地),采用静态箱-气相色谱法分析了不同农业措施下的土壤温室气体(CO_2、N_2O、CH_4)排放特征。结果表明:和CTF相比,LL冬小麦产量显著提高7.10%;降雨、灌溉后表层土壤含水率显著提高,冬小麦季土壤CH_4吸收量显著增加22%,土壤CO_2、N_2O累计排放量分别显著增加27.20%、8.81%。PF产量与CTF无显著差异;土壤N_2O排放峰出现在追肥后,PF排放峰值显著较CTF低15.41%,精准施肥至收获期间PF土壤N_2O显著减排15.05%,但整个冬小麦生长季PF土壤CO_2、N_2O累计排放量和CH_4累计吸收量与CTF均无显著差异。和CTF相比,PF+LL小麦产量显著提高8.2%,同时PF+LL土壤具备较好的持水性,雨季及灌溉后表层土壤含水率分别显著提高8.81%、7.63%,冬小麦生长季土壤CO_2累计排放量显著增加33.53%,CH_4吸收量显著增加31.5%,N_2O累计排放量无显著差异,但在精准施肥至收获期间土壤N_2O显著减排10.22%。综上,激光平地技术可显著增产但综合增温潜势较强,精准施肥技术对产量无显著影响,但降低了N_2O排放峰值,减少了精准施肥后的N_2O累计排放量,表现出一定的N_2O减排潜力。     

Identifying the limiting factors driving the winter wheat yield gap on smallholder farms by agronomic diagnosis in North China Plain

North China Plain(NCP) is the primary winter wheat production region in China, characterized by smallholder farming systems. Whereas the winter wheat average yield of smallholder farmers is currently low, the yield potential and limiting factors driving the current yield gap remain unclear. Therefore, increasing the wheat yield in NCP is essential for the national food security. This study monitored wheat yield, management practices and soil nutrient data in 132 farmers' fields of Xushui County, Baoding City, Hebei Province during 2014–2016. These data were analyzed using variance and path analysis to determine the yield gap and the contribution of yield components(i.e., spikes per hectare, grain number per spike and 1 000-grain weight) to wheat yield. Then, the limiting factors of yield components and the optimizing strategies were identified by a boundary line approach. The results showed that the attainable potential yield for winter wheat was 10 514 kg ha~(–1). The yield gaps varied strongly between three yield groups(i.e., high, middle and low), which were divided by yield level and contained 44 farmers in each group, and amounted to 2 493, 1 636 and 814 kg ha~(–1), respectively. For the three yield components, only spikes per hectare was significantly different(P0.01) among the three yield groups. For all 132 farmers' fields, correlation between yield and spikes per hectare(r=0.51, P0.01), was significantly positive, while correlations with grain number per spike(r=–0.16) and 1 000-grain weight(r=–0.10) were not significant. The path analysis also showed that the spikes per hectare of winter wheat were the most important component to the wheat yield. Boundary line analysis showed that seeding date was the most limiting factor of spikes per hectare with the highest contribution rate(26.7%), followed by basal N input(22.1%) and seeding rate(14.5%), which indicated that management factors in the seeding step were the most important for affecting spikes per hectare. For desired spikes per hectare(6.598×10~6 ha~(–1)),the seeding rate should range from 210–300 kg ha~(–1), seeding date should range from 3th to 8th October, and basal N input should range from 90~(–1)80 kg ha~(–1). Compared to these reasonable ranges of management measures, most of the farmers' practices were not suitable, and both lower and higher levels of management existed. It is concluded that the strategies for optimizing yield components could be achieved by improving wheat seeding quality and optimizing farmers' nutrient management practices in the NCP.     

华北冬小麦开花及成熟期变化特征分析

利用华北平原59个农业气象观测站1981—2010年冬小麦生育期资料,分析了该区域冬小麦在气候变暖背景下开花期和成熟期的变化趋势特征。研究结果表明：近30年来,华北平原冬小麦开花期和成熟期均发生了明显变化。相对1980s而言,1990s开花期普遍提前2～5 d,成熟期提前1～6 d左右,2000s开花期则一般提前3～9 d,成熟期提前1～7 d左右。因此,随着年代推进,华北平原冬小麦开花期和成熟期提前趋势在进一步加剧。相对1980s而言,1990s生育期等值线普遍北移,而2000s等值线进一步北移的趋势更加明显。研究发现,3—5月月平均气温升高是开花期和成熟期提前的一个重要影响因素。     

Stand establishment,root development and yield of winter wheat as affected by tillage and straw mulch in the water defi cit hilly region of southwestern China

Good crop stand establishment and root system development are essential for optimum grain yield of dryland wheat(Triticum aestivum L.). At present, little is known about the effect of tillage and straw mulch on the root system of wheat under dryland areas in southwestern China. The aim of this study was to evaluate the effect of three tillage treatments(no-till, NT; rotary till, RT; conventional till, CT) and two crop residue management practices(straw mulch, ML; non-straw mulch, NML) on stand establishment, root growth and grain yield of wheat. NT resulted in lower soil cover thickness for the wheat seed, higher number of uncovered seeds, lower percentage of seedling-less ridges and lower tiller density compared to RT and CT; ML resulted in higher tiller density compared to NML. Straw mulching resulted in more soil water content and root length density(RLD) at most of the growth stages and soil depths. The maximum RLD, root surface area density and root dry matter density were obtained under NT. In the topmost 10 cm soil layer, higher RLD values were found under NT than those under RT and CT. There were no significant differences in the yield or yield components of wheat among the tillage treatments in 2011–2012, but NT resulted in a significant higher yield compared to RT and CT in 2012–2013. Grain yield was significantly higher in ML compared to in NML. A strong relationship was observed between the water-use efficiency and the grain yield. Both NT and ML proved beneficial for wheat in term of maintaining higher tiller density, better soil water status and root growth, leading to a higher grain yield and enhanced water-use efficiency, especially in a low rainfall year.     

Impacts of climate change on drought risk of winter wheat in the North China Plain

Drought is a major natural disaster causing crop yield losses, while its occurrence mechanism and spatiotemporal variations in a changing climate are still not clear. Based on a long-term climatic dataset(during 1958–2015) from weather stations in the North China Plain(NCP), the influencing mechanism of various climatic factors on drought risk of winter wheat was quantified by using sensitivity analysis, Mann-Kendall trend test and slope estimation. The results indicated that climatic factors have changed considerably over the past six decades in the growth season of winter wheat. As a result, winter wheat suffered from severe droughts(with 350 mm of water deficit during its growth season), particularly at the jointing–heading and heading–mature stages, which were critical to crop yield formation. There were large spatial and temporal variations in drought risk and climatic change factors at different growth stages of winter wheat. Despite precipitation playing a vital role in determining the spatiotemporal patterns of drought risk, high temperature and low humidity along with other climatic factors at key growth stages of winter wheat aggravated drought risk. Particularly, temperature at nearly 90% weather stations showed a notablely upward trend, which exacerbated water deficit and drought risk of winter wheat. Given the complexity and high uncertainty of climate change, these findings provide important information for adapting crop production to future climate change and accompanied droughts while ensuring food security and agricultural sustainability.     

硫素对冬小麦品质和产量的影响

在高氮低硫地块施用硫肥提高了冬小麦的群体光合速率 ,鲁麦 2 2群体光合速率随施硫量的增加而提高 ,烟农 15的S3 处理和S2 处理之间差异不显著。施硫肥显著提高两品种旗叶硝酸还原酶活性 ,两品种植株体在各个时期的氮素含量及积累量均增加。施硫肥后 ,两品种籽粒容重、出粉率、蛋白质含量、湿面筋含量和面团稳定时间均显著提高 ,其中S2 处理显著高于S1处理和S0 处理。施硫肥增加两品种的产量 ,鲁麦 2 2穗数、穗粒数和千粒重随施硫量的增加显著增加 ,S3 处理的产量最高 ;硫肥对烟农 15的穗数和穗粒数有提高作用 ,但对千粒重影响较小     

有机无机复混肥对冬小麦产量及其水分利用效率的影响

对农业废弃物采用生物发酵腐解,进行无害化、矿化和腐殖化处理,经干燥后添加一定比例的化肥以调节养分,加入成粒剂制成颗粒状有机无机复混肥。对获得的有机无机复混肥进行冬小麦田间试验,结果表明,有机无机复混肥可以促进冬小麦分蘖,改善冬小麦产量结构,提高冬小麦产量756.0～901.5kg/hm2;还可降低冬小麦耗水系数,提高冬小麦水分利用效率1.311～1.675kg/(mm·hm2)。     

华北平原不同年代冬小麦品种灌浆特性对水分亏缺的响应

选取华北平原20世纪50年代以来的代表品种碧蚂1号、济南2号、泰山1号、冀麦26、冀麦38和济麦22,通过田间试验的方法研究了灌溉和雨养条件下不同年代小麦品种籽粒千粒重和灌浆特性的差异.结果表明:1)在灌溉和雨养条件下,小麦籽粒千粒重随品种的更替均呈逐渐增加的趋势,灌浆期天数和平均灌浆速率逐渐增加,其中速增期天数和灌浆速率的增加是当前小麦品种济麦22籽粒千粒重较高的主要原因;2)与灌溉条件相比,在雨养条件下不同年代小麦品种的籽粒千粒重、灌浆期天数和平均灌浆速率、速增期天数和灌浆速率均有所下降,但下降幅度存在差异,当前品种济麦22的下降幅度高于以前品种,对水分亏缺的敏感性较强.因此,在未来的小麦育种中,应更多地选育速增期天数多和灌浆速率高的品种,并提高其对水分亏缺的适应性.     

Effects of deep vertical rotary tillage on the grain yield and resource use efficiency of winter wheat in the Huang-Huai-Hai Plain of China

Tillage represents an important practice that is used to dynamically regulate soil properties,and affects the grain production process and resource use efficiency of crops.The objectives of this 3-year field study carried out in the Huang-Huai-Hai(HHH) Plain of China were to compare the effects of a new deep vertical rotary tillage (DVRT) with the conventional shallow rotary tillage (CT) on soil properties,winter wheat (Triticum aestivum L.) grain yield and water and nitrogen use efficiency at different productivity levels,and to identify a comprehensive management that optimizes both grain yield and resource use efficiency in the HHH Plain.A split-plot design was adopted in field experiments in the winter wheat growing seasons of 2016–2017 (S1),2017–2018 (S2) and 2018–2019 (S3),with DVRT (conducted once in June 2016) and CT performed in the main plots.Subplots were treated with one of four targeted productivity level treatments (SH,the super high productivity level;HH,the high productivity and high efficiency productivity level;FP,the farmer productivity level;ISP,the inherent soil productivity level).The results showed that the soil bulk density was reduced and the soil water content at the anthesis stage was increased in all three years,which were due to the significant effects of DVRT.Compared with CT,grain yields,partial factor productivity of nitrogen (PFP_N),and water use efficiency (WUE) under DVRT were increased by 22.0,14.5 and 19.0%.Path analysis and direct correlation decomposition uncovered that grain yield variation of winter wheat was mostly contributed by the spike numbers per area under different tillage modes.General line model analysis revealed that tillage mode played a significant role on grain yield,PFP_N and WUE not only as a single factor,but also along with other factors(year and productivity level) in interaction manners.In addition,PFP_N and WUE were the highest in HH under DVRT in all three growth seasons.These results provided a theoretical basis and technical support for coordinating the high yield with high resource use efficiency of winter wheat in the resource-restricted region in the HHH Plain of China.     

Growth and nitrogen productivity of drip-irrigated winter wheat under different nitrogen fertigation strategies in the North China Plain

Excessive application of nitrogen (N) fertilizer is the main cause of N loss and poor use efficiency in winter wheat (Triticum aestivum L.) production in the North China Plain (NCP).  Drip fertigation is considered to be an effective method for improving N use efficiency and reducing losses, while the performance of drip fertigation in winter wheat is limited by poor N scheduling.  A two-year field experiment was conducted to evaluate the growth, development and yield of drip-fertigated winter wheat under different split urea (46% N, 240 kg ha^–1) applications.  The six treatments consisted of five fertigation N application scheduling programs and one slow-release fertilizer (SRF) application.  The five N scheduling treatments were N0–100 (0% at sowing and 100% at jointing/booting), N25–75 (25% at sowing and 75% at jointing and booting), N50–50 (50% at sowing and 50% at jointing/booting), N75–25 (75% at sowing and 25 at jointing/booting), and N100–0 (100% at sowing and 0% at jointing/booting).  The SRF (43% N, 240 kg ha^–1) was only used as fertilizer at sowing.  Split N application significantly (P<0.05) affected wheat grain yield, yield components, aboveground biomass (ABM), water use efficiency (WUE) and nitrogen partial factor productivity (NPFP).  The N50–50 and SRF treatments respectively had the highest yield (8.84 and 8.85 t ha^–1), ABM (20.67 and 20.83 t ha^–1), WUE (2.28 and 2.17 kg m^–3) and NPFP (36.82 and 36.88 kg kg^–1).  This work provided substantial evidence that urea-N applied in equal splits between basal and topdressing doses compete economically with the highly expensive SRF for fertilization of winter wheat crops.  Although the single-dose SRF could reduce labor costs involved with the traditional method of manual spreading, the drip fertigation system used in this study with the N50–50 treatment provides an option for farmers to maintain wheat production in the NCP.     

The water-saving potential of using micro-sprinkling irrigation for winter wheat production on the North China Plain

The shortage of groundwater resources is a considerable challenge for winter wheat production on the North China Plain. Water-saving technologies and procedures are thus urgently required. To determine the water-saving potential of using micro-sprinkling irrigation(MSI) for winter wheat production, field experiments were conducted from 2012 to 2015. Compared to traditional flooding irrigation(TFI), micro-sprinkling thrice with 90 mm water(MSI1) and micro-sprinkling four times with 120 mm water(MSI2) increased the water use efficiency by 22.5 and 16.2%, respectively, while reducing evapotranspiration by 17.6 and 10.8%. Regardless of the rainfall pattern, MSI(i.e., MSI1 or MSI2) either stabilized or significantly increased the grain yield, while reducing irrigation water volumes by 20–40%, compared to TFI. Applying the same volumes of irrigation water, MSI(i.e., MSI3, micro-sprinkling five times with 150 mm water) increased the grain yield and water use efficiency of winter wheat by 4.6 and 11.7%, respectively, compared to TFI. Because MSI could supply irrigation water more frequently in smaller amounts each time, it reduced soil layer compaction, and may have also resulted in a soil water deficit that promoted the spread of roots into the deep soil layer, which is beneficial to photosynthetic production in the critical period. In conclusion, MSI1 or MSI2 either stabilized or significantly increased grain yield while reducing irrigation water volumes by 20–40% compared to TFI, and should provide water-saving technological support in winter wheat production for smallholders on the North China Plain.     

Mapping winter wheat using phenological feature of peak before winter on the North China Plain based on time-series MODIS data

By employing the unique phenological feature of winter wheat extracted from peak before winter(PBW) and the advantages of moderate resolution imaging spectroradiometer(MODIS) data with high temporal resolution and intermediate spatial resolution,a remote sensing-based model for mapping winter wheat on the North China Plain was built through integration with Landsat images and land-use data. First,a phenological window,PBW was drawn from time-series MODIS data. Next,feature extraction was performed for the PBW to reduce feature dimension and enhance its information. Finally,a regression model was built to model the relationship of the phenological feature and the sample data. The amount of information of the PBW was evaluated and compared with that of the main peak(MP). The relative precision of the mapping reached up to 92% in comparison to the Landsat sample data,and ranged between 87 and 96% in comparison to the statistical data. These results were sufficient to satisfy the accuracy requirements for winter wheat mapping at a large scale. Moreover,the proposed method has the ability to obtain the distribution information for winter wheat in an earlier period than previous studies. This study could throw light on the monitoring of winter wheat in China by using unique phenological feature of winter wheat.