Effects of Reduced Nitrogen Fertilization and Biochar Application on CO_2 and N_2O Emissions from a Summer Maize-Winter Wheat Rotation Field in North China

This experiment was conducted in Xinxiang, Henan from June 2013 to June 2014. Total four treatments were designed including farmers ’ common practice （F, 250 kg/hm^2）, 80% F （LF, 200 kg/hm^2）, 80% F＋biochar （LFC） and no fertilizer （CK） to measure the dynamic emissions of CO2 and N2O from a summer maize-winter wheat field by static chamber-gas chromatography method. The results showed that the soil CO2 emission was 21.8-1 022.7 mg/（m^2·h）, and was mainly influenced by soil temperature and moisture content. During the growth of summer maize, the soil CO2 emission was more significantly affected by soil moisture con-tent; and in winter wheat growing season, it was more significantly affected by soil temperature in the top 5 cm. The LF and LFC treatments significantly reduced the soil cumulative CO2 emission, especial y during the growth of winter wheat. Fertiliza-tion and irrigation were the main factors influencing the soil N2O emission. The soil N2O emission during the fertilization period accounted for 73.9%-74.5% and 40.5%-43.6% of the soil cumulative N2O emission during the summer maize-and winter wheat-growing season, respectively. The peak of emission fluxes was determined by fertilization amount, while the occurrence time of emission peak and emission re-duction effect were influenced by irrigation. The LF treatment reduced the soil cu-mulative N2O emission by 15.7%-16.8% and 18.1%-18.5% during the growth period of summer maize and winter wheat, respectively. Reduced nitrogen fertilization is an effective way for reducing N2O emission in intensive high-yielding farmland. Under a suitable nitrogen level （200 kg/hm^2）, the application of biochar showed no significant effect on the soil N2O emission in a short term. The N2O emission factors of the L and LF treatments were 0.60% and 0.56%, respectively. ln the intensive high-yield-ing farmland of North China, reducing the nitrogen application amount is an appro-priate measure to mitigate greenhouse gas emissions without crop yield loss.

Effects of Continuous Nitrogen Application on Grain Yield and Nitrogen Uptake and Utilization in Winter Wheat-Summer Maize Rotation System

[Objective] This study aimed to achieve high yield and stable yield of win- ter wheat-summer maize rotation system and provide basis for rational application of nitrogen fertilizer. [Method] Effects of continuous nitrogen application on grain yield, economic profit, nitrogen uptake and utilization efficiency, and soil inorganic nitrogen accumulation in winter wheat-summer maize rotation system were investigated. [Re- sult] Nitrogen application could significantly increase the y（eld of the winter wheat- summer maize rotation system, which increased by 17.76%-30.32% and 22.24%- 46.63% in two rotation cycles, respectively. The yield of the winter wheat-summer maize rotation system was the maximum in two rotation cycles with nitrogen appli- cation amount of 660.0 kg/hm2, which reached respectively 23 391.19 and 23 444.35 kg/hm2, the yield and economic benefit were the highest, the nitrogen fertilizer use efficiency was 22.2% and 30.7%, the agronomic efficiency was 8.3 and 11.3 kg/kg. However, the nitrogen fertilizer use efficiency and agronomic efficiency between ni- trogen application amount of 540.0 and 660.0 kg/hm2 showed no significant differ- ence. After two rotation cycles, inorganic nitrogen accumulation in 0-40 cm soil with nitrogen application amount of 540.0 kg/hm2 was almost equal to that before experi- ment. [Conclusion] Under the experimental conditions, comprehensively considering the grain yield, economic profit, nitrogen fertilizer efficiency and soil inorganic nitro- gen balance, the optimal nitrogen application amount was 625.3-660.0 kg/hm2 in high-yield winter wheat-summer maize rotation system.

Effects of saline irrigation on soil salt accumulation and grain yield in the winter wheat-summer maize double cropping system in the low plain of North China

In the dominant winter wheat （WW）-summer maize （SM） double cropping system in the low plain located in the North China, limited access to fresh water, especially during dry season, constitutes a major obstacle to realize high crop productivity. Using the vast water resources of the saline upper aquifer for irrigation during WW jointing stage, may help to bridge the peak of dry season and relieve the tight water situation in the region. A field experiment was conducted during 2009-2012 to investigate the effects of saline irrigation during WW jointing stage on soil salt accumulation and productivity of WW and SM. The experiment treatments comprised no irrigation （T1）, fresh water irrigation （T2）, slightly saline water irrigation （T3：2.8 dS m-l）, and strongly saline water irrigation （T4：8.2 dS m-1） at WW jointing stage. With regard to WW yields and aggregated annual WW-SM yields, clear benefits of saline water irrigation （T3 ＆ T4） compared to no irrigation （T1）, as well as insignificant yield losses compared to fresh water irrigation （T2） occurred in all three experiment years. However, the increased soil salinity in eady SM season in consequence of saline irrigation exerted a negative effect on SM photosynthesis and final yield in two of three experiment years. To avoid the negative aftereffects of saline irrigation, sufficient fresh water irrigation during SM sowing phase （i.e., increase from 60 to 90 mm） is recommended to guarantee good growth conditions during the sensitive early growing period of SM. The risk of long-term accumulation of salts as a result of saline irrigation during the peak of dry season is considered low, due to deep leaching of salts during regularly occurring wet years, as demonstrated in the 2012 experiment year. Thus, applying saline water irrigation at jointing stage of WW and fresh water at sowing of SM is most promising to realize high yield and fresh irrigation water saving.

Water consumption in summer maize and winter wheat cropping system based on SEBAL model in Huang-Huai-Hai Plain, China

Crop consumptive water use is recognized as a key element to understand regional water management performance. This study documents an attempt to apply a regional evapotranspiration model（SEBAL） and crop information for assessment of regional crop（summer maize and winter wheat） actual evapotranspiration（ET a） in Huang-Huai-Hai（3H） Plain, China. The average seasonal ET a of summer maize and winter wheat were 354.8 and 521.5 mm respectively in 3H Plain. A high-ET a belt of summer maize occurs in piedmont plain, while a low ET a area was found in the hill-irrigable land and dry land area. For winter wheat, a high-ET a area was located in the middle part of 3H Plain, including low plain-hydropenia irrigable land and dry land, hill-irrigable land and dry land, and basin-irrigable land and dry land. Spatial analysis demonstrated a linear relationship between crop ET a, normalized difference vegetation index（NDVI）, and the land surface temperature（LST）. A stronger relationship between ET a and NDVI was found in the metaphase and last phase than other crop growing phase, as indicated by higher correlation coefficient values. Additionally, higher correlation coefficients were detected between ET a and LST than that between ET a and NDVI, and this significant relationship ran through the entire crop growing season. ET a in the summer maize growing season showed a significant relationship with longitude, while ET a in the winter wheat growing season showed a significant relationship with latitude. The results of this study will serve as baseline information for water resources management of 3H Plain.

Evaluation of Pathway of Nitrogen Loss in Winter Wheat and Summer Maize Rotation System

The nitrogen loss pathway in winter wheat and summer maize rotation system was studied based on field experimental data. The results showed that nitrogen recovery rate was significantly decreased with nitrogen fertilization rate increased, while residual rate and losses rate had an increasing trend. Accumulated ammonia volatilization loss in winter wheat and summer maize rotation was 12. 8(N0), 22.0(N120), 33. 0(N240) and 64. 5 kg N ha-1 (N360) respectively and rate of ammonia volatilization loss was 3.8, 4.2 and 7.2% respectively while urea was mixed with 0 -10 cm soil or spread before irrigation. Denitrification loss with acetylene-soil core incubation method in winter wheat was lower than 1 kg N ha-1 and rate of denitrification loss was 0. 21 - 0. 26% or trace. Denitrification loss in summer maize was 1 - 14 kg N ha-1 and rate of denitrification loss was 1-5%. The total gaseous loss in winter wheat and summer maize rotation system was less than 10%, and the main nitrogen fertilizer loss way was leaching below 0 - 100 cm soil profile and accumulated in deeper soil.

Fate of ^(15)N-Labeled Urea Under a Winter Wheat-Summer Maize Rotation on the North China Plain

A field experiment was conducted to investigate the fate of ^15N-labeled urea and its residual effect under the winter wheat （Triticum aestivum L.） and summer maize （Zea mays L.） rotation system on the North China Plain. Compared to a conventional application rate of 360 kg N ha^-1 （N360）, a reduced rate of 120 kg N ha^-1 （N120） led to a significant increase （P 〈 0.05） in wheat yield and no significant differences were found for maize. However, in the 0-100 cm soil profile at harvest, compared with N360, N120 led to significant decreases （P 〈 0.05） of percent residual N and percent unaccounted-for N, which possibly reflected losses from the managed system. Of the residual fertilizer N in the soil profile, 25.6%-44.7% and 20.7%-38.2% for N120 and N360, respectively, were in the organic N pool, whereas 0.3%-3.0% and 11.2%-24.4%, correspondingly, were in the nitrate pool, indicating a higher potential for leaching loss associated with application at the conventional rate. Recovery of residual N in the soil profile by succeeding crops was less than 7.5% of the applied N. For N120, total soil N balance was negative; however, there was still considerable mineral N （NH4^＋-N and NO3^--N） in the soil profile after harvest. Therefore, N120 could be considered ngronomically acceptable in the short run, but for long-term sustainability, the N rate should be recommended based on a soil mineral N test and a plant tissue nitrate test to maintain the soil fertility.

Effects of mulches on water use in a winter wheat/summer maize rotation system in Loess Plateau, China

Limited water resources often result in reduced crop yield and low water productivity（WP）. In northwestern China, crop production is generally dependent on precipitation. Therefore, a variety of agricultural rainwater harvesting（ARH） techniques have been used for conserving soil moisture, ameliorating soil environment, increasing crop yield, and improving water use efficiency. A two-year（2013–2015） field experiment was conducted under a typical sub-humid drought-prone climate in Yangling（108°24′E, 34°20′N; 521 m a.s.l.）, Shaanxi Province, China, to explore the effects of mulching（same for summer maize and winter wheat） on soil moisture, soil temperature, crop water consumption, and crop yield with a winter wheat/summer maize rotation. Crops were planted in a ridge-furrow pattern and the treatments consisted of a transparent film mulch over the ridges（M1）, a crop straw mulch in the furrows（M2）, a transparent film mulch over the ridges and a crop straw mulch in the furrows（M3）, a black film mulch over the ridges and a crop straw mulch in the furrows（M4）, and a control with no mulch（CK）. Results showed that M4 was the best treatment for improving soil water storage and content, and decreasing crop water consumption during the summer maize and winter wheat rotation. In both maize and wheat seasons, M1 had a higher soil temperature than M2 and CK, and M3 had a higher soil temperature than M4. In the maize seasons, M4 had the highest yield, WP, and precipitation productivity（PP）, with the average values for these parameters increasing by 30.9%, 39.0%, and 31.0%, respectively, compared to those in CK. In the wheat seasons, however, M3 had the highest yield, WP, and PP, with the average values for these parameters being 23.7%, 26.7%, and 23.8% higher, respectively, than those in CK. Annual yield（maize and wheat yields combined） and WP did not differ significantly between M3 and M4. These results suggested that M3 and M4 may thus be the optimal ARH practices for the production of winter wheat and summer maize, respectively, in arid and semi-arid areas.

Effect of Limited Single Irrigation on Yield of Winter Wheat and Spring Maize Relay Intercropping

A field experiment was conducted during the 2002/2003 cropping season of winter wheat （Triticum aestivum） and spring maize （Zea mays） to evaluate the effect of limited single drip irrigation on the yield and water use of both crops under relay intercropping in a semi-arid area of northwestern China. A controlled 35 mm single irrigation, either early or late, was applied to each crop at a certain growth stage. Soil water, leaf area, final grain yield and yield components such as the thousand-grain weight, length of spike, fertile spikelet number, number of grains per spike, and grain weight per spike were measured, and water use efficiency and leaf area index were calculated for the irrigated and non-irrigated relay intercropping treatments and sole cropping controls. The results showed that yield, yield components, water use efficiency, and leaf area index in the relay intercropping treatments were affected by limited single drip irrigation during various growth stages of wheat and maize. The total yields in the relay intercropping treatment irrigated during the heading stage of wheat and the heading and anthesis stage of maize were the highest among all the treatments, followed by that irrigated during the anthesis stage of wheat and silking stage of maize; so was the water use efficiency. Significant differences occurred in most yield components between the irrigated and non-irrigated relay-intercropping treatments. The dynamics of the leaf area index in the relay-intercropped or solely cropped wheat and maize showed a type of single-peak pattern, whereas that of the relay intercropping treatments showed a type of double-peak pattern. Appropriately, limited single irrigation and controlled soil water content level could result in higher total yield, water use efficiency, and leaf area index, and improved yield components in relay intercropping. This practice saved the amount of water used for irrigation and also increased the yield. Therefore, heading stage of wheat and heading and anthesis stage of maize were suggested to be the optimum limited single irrigation time for relay-intercropped wheat and maize in the semi-arid area.

The Effect of Organo-Mineral Fertilizer Applications on the Yield of Winter Wheat, Spring Barley, Forage Maize and Grass Cut for Silage

Biosolids were applied with urea to produce a granulated organo-mineral fertiliser (OMF) for application by farm fertiliser equipment to a range of agricultural crops. The recommended rates of nitrogen, phosphate and potash were calculated for the test crops using “The Fertiliser Manual”, which assesses the nutrient requirement based on previous cropping, rainfall and soil index. The OMF produced similar crop yields compared to ammonium nitrate fertiliser when applied as a top-dressing to winter wheat, forage maize and grass cut for silage in the cropping years 2010 to 2014. In 2012 the grain yield of spring barley top-dressed with OMF was significantly lower than the conventional fertiliser treatment, due to dry conditions following application. For this reason it is recommended that OMF is incorporated into the seedbed for spring sown crops and The Safe Sludge Matrix guidelines followed. The experimental work presented shows that OMF can be used in sustainable crop production systems as a source of nitrogen and phosphorus for a range of agricultural crops.

Identifying the critical phosphorus balance for optimizing phosphorus input and regulating soil phosphorus effectiveness in a typical winter wheat-summer maize rotation system in North China

Phosphorus(P)is a nonrenewable resource and a critical element for plant growth that plays an important role in improving crop yield.Excessive P fertilizer application is widespread in agricultural production,which not only wastes phosphate resources but also causes P accumulation and groundwater pollution.Here,we hypothesized that the apparent P balance of a crop system could be used as an indicator for identifying the critical P input in order to obtain a high yield with high phosphorus use efficiency(PUE).A 12-year field experiment with P fertilization rates of 0,45,90,135,180,and 225 kg P_(2)O_(5)ha^(-1)was conducted to determine the crop yield,PUE,and soil Olsen-P value response to P balance,and to optimize the P input.Annual yield stagnation occurred when the P fertilizer application exceeded a certain level,and high yield and PUE levels were achieved with annual P fertilizer application rates of 90-135 kg P_(2)O_(5)ha^(-1).A critical P balance range of 2.15-4.45 kg P ha^(-1)was recommended to achieve optimum yield with minimal environmental risk.The critical P input range estimated from the P balance was 95.7-101 kg P_(2)O_(5)ha^(-1),which improved relative yield(>90%)and PUE(90.0-94.9%).In addition,the P input-output balance helps in assessing future changes in Olsen-P values,which increased by 4.07 mg kg^(-1)of P for every 100 kg of P surplus.Overall,the P balance can be used as a critical indicator for P management in agriculture,providing a robust reference for limiting P excess and developing a more productive,efficient and environmentally friendly P fertilizer management strategy.

Evapotranspiration and ratio of soil evaporation to evapotranspiration of winter wheat and maize in north China

Evapotranspiration （ETc） is an important quantity for hydrological cycle. This study shows evapotranspiration, the ratio of evaporation to evapotranspiration （E/ETc） of winter wheat and maize in north China. Several relationships, namely, E/ET0 and soil surface moisture, E/ET0 and leaf area index （LAI）, are also analyzed. The average seasonal ETc values for winter wheat, maize （2008） and maize （2009） are 431.21,456.3 and 341.4mm. The value of E/ET0 varied from 1 at initial growth stage to 0.295 at the later growth for winter wheat, and from 1 to 0.492, from 1 to 0.566 for maize （2008） and maize （2009）. The relationship between E/ET0 and surface soil water content, and E/ET0 and LAI are fitted to a quadratic parabola equation with significant correlation coefficients, respectively, for wheat and maize. These results should help the precise planning and efficient management of irrigation for these crops in this region.

Study on Soil Denitrification in Wheat-Maize Rotation System

Soil denitrification was studied in wheat-maize rotation cropping system on an aquic cambisol. Results showed that the N loss amount by denitrification ranged from 4.7 to 9.7 kg per hectare with different levels of nitrogen application and the key stage for denitification was during summer maize-growth-period, especially within 1-2 weeks after fertilizer nitrogen was applied. Similar trend was found between soil N2O production/emission dynamic and denitrification dynamic in the rotation system, which may indicate that mainly N2O is produced in nitrification process.

播期调整对华北北部冬小麦、夏玉米产量和品质的影响

【目的】基于田间分期播种试验,研究华北北部冬小麦、夏玉米播期调整,其生长发育、光合生理特性、籽粒灌浆和产量形成及品质对气候变暖的不同响应,为华北平原农业生产采取措施应对气候变化提供科学依据。【方法】采用分期播种方法,于2017—2023年在华北北部的河北固城农业气象国家野外科学观测研究站开展冬小麦和夏玉米的大田分期(早播10 d、正常播期、晚播10 d、晚播20 d)播种试验,获取冬小麦和夏玉米的生育进程、地上干物质累积和分配、叶片光合特性、籽粒灌浆速率以及产量农艺性状和籽粒营养成分等资料。【结果】冬小麦全生育期随播期推迟而缩短,主要原因在于冬前幼苗期缩短;夏玉米全生育期与播期呈抛物线关系,播期每推迟10 d,幼苗期缩短1.3 d,花粒期和籽粒形成-灌浆期分别延长1.5和1.6 d。冬小麦、夏玉米籽粒灌浆过程对播期调整的响应完全不同,冬小麦籽粒灌浆特征在播期间反应并不敏感,夏玉米籽粒灌浆速率在播期间差异较小,但籽粒形成期、灌浆结束日期和峰值日期因播期推迟顺次延后,且灌浆持续日数因播期每推迟10 d,灌浆持续日数缩短4 d。北方麦区在秋暖和冬暖背景下,冬小麦播种期界限延宽,播期对产量的影响明显减弱,播期推迟配套增加播种量,产量不减且会小幅增产;夏玉米产量随播期推迟明显递减,理论产量播期每推迟10 d递减率1381.50 kg·hm^(-2),但冬小麦和夏玉米晚播20 d产量都凸显跳跃变小。播期每推迟10 d,冬小麦籽粒分配率递增1.67%,夏玉米则递减1.57%,冬小麦收获指数提高0.017,而夏玉米降低0.016。冬小麦和夏玉米叶片光合速率(Pn)对播期的响应亦不同,冬小麦播期间的Pn较为相近,而夏玉米播期每推迟10 d Pn递减率1.21μmol·m^(-2)·s-1。播期调整对华北北部冬小麦、夏玉米籽粒品质不会产生明显影响。【结论】气候变暖背景下我国北方冬小麦延迟播种,延宽适宜播种期是适应气候变暖的积极有效措施,华北平原夏玉米适期早播可避免高温热害影响,有助于稳产增产。

冬小麦-夏玉米轮作田沟金针虫垂直活动特征

基于河北固城农业气象国家野外科学观测研究站2019—2020年、2021—2022年冬小麦-夏玉米轮作田沟金针虫在土壤中分层调查数据,引入虫口重量指标,结合虫口密度指标,揭示沟金针虫在冬小麦-夏玉米轮作田为害-休眠动态变化,讨论沟金针虫在土壤中垂直活动特征、气象条件与其相关性以及对冬小麦产量影响。结果表明:沟金针虫在冬小麦-夏玉米轮作田存在3个为害期和3个休眠期,且交替出现。3个为害期出现在冬小麦返青-拔节期、夏玉米幼苗期、冬小麦秋苗期,3个休眠期出现在冬小麦越冬期、冬小麦成熟-收获期、夏玉米灌浆-成熟期,3个为害期中以冬小麦返青-拔节期最为严重。冬季偏暖及春季回暖早,沟金针虫表现出晚下早上特征,使得沟金针虫冬季休眠期缩短而为害活动期延长;土壤温度、湿度以及食源关系共同影响沟金针虫为害、休眠以及取食活动,其为害适宜土壤重量含水率约为15%~18%,适宜土壤温度为14~18℃。分析沟金针虫为害与冬小麦减产率可知,虫口密度每增加10 m^(-2)或虫口重量每增加1.0 g·m^(-2),可导致减产率增加5.1%。

西北旱塬免耕的产量效应受降水特征和施肥显著影响

【目的】在冬小麦-夏春玉米轮作体系,研究不同降水年型条件下西北雨养农业区耕作与施肥对作物产量的影响,为西北旱塬作物高产稳产提供理论依据。【方法】基于2005年甘肃陇东旱塬设置的土壤耕作与培肥长期定位试验(3年冬小麦—1年春玉米),主处理为传统耕作和免耕,副处理为不施肥(CK)、单施氮肥(N)、单施磷肥(P)、单施农家肥(M)、氮磷配施(NP)和氮磷配施农家肥(NPM)。结合对冬小麦和玉米产量的分析,探究不同耕作与施肥处理下作物产量在不同降水年型的差异机制。【结果】降水年型、耕作和施肥方式显著影响冬小麦和玉米产量。无论何种降水年型或耕作方式,配施有机肥的NPM处理作物产量(冬小麦3441 kg/hm^(2),春玉米8991 kg/hm^(2))均显著高于其他施肥处理,并且NPM处理对作物的增产效果在丰水年型更为明显。在丰水年型,相对于传统耕作,免耕处理的作物产量无明显差异,但在干旱及平水年型下,免耕冬小麦平均产量分别下降了15.6%和25.7%,玉米平均产量分别下降了17.9%和4.6%;与传统耕作相比,免耕处理下的冬小麦和玉米水分利用效率在干旱年型分别下降了6.7%和17.0%,冬小麦水分利用效率在平水年型下降了24.0%。免耕处理下土壤有机质、全氮、全钾、速效氮、速效磷和速效钾含量显著高于传统耕作。【结论】在西北半干旱雨养农业区,干旱及平水年型免耕虽然提高了土壤养分含量,但降低了作物水分利用效率,这是导致作物产量降低的主要原因。因此,需要根据降水情况选择耕作方式,提高西北黄土旱塬作物产量的稳定性。

施用生物炭和秸秆还田对农田温室气体排放及增温潜势的影响

【目的】农业生态系统增温潜势是影响全球气候变化的重要部分。本研究通过田间试验明确施用生物炭和秸秆还田对农田增温潜势的影响,以期为减缓气候变化和农业废弃物资源化利用提供理论依据。【方法】在山东省桓台县农业生态系统试验站的冬小麦-夏玉米轮作农田中开展了3年田间定位试验,试验共设置4个处理:①对照(CK);②施用生物炭9.0t·hm^(-2)·a^(-1)(C);③全量秸秆还田(S);④秸秆还田配施9.0 t·hm^(-2)·a^(-1)生物炭(CS)。4个处理均施等量的氮磷钾化肥,其中氮肥为尿素,用量为200 kg·hm^(-2)·a^(-1),磷肥为过磷酸钙,用量为55 kg·hm^(-2)·a^(-1),钾肥为硫酸钾,用量为40 kg·hm^(-2)·a^(-1)。采用静态暗箱-气相色谱法测定各处理温室气体(CO_(2)、N_(2)O和CH_4)的排放通量并计算净全球增温潜势(NGWP)和温室气体排放强度(GHGI),分析连续施用生物炭和秸秆还田对农田温室气体排放及增温潜势的影响。【结果】(1)综合3年的温室气体排放情况,与CK处理相比,S和CS处理的年平均生态呼吸排放量(Re)分别增加了47.8%和67.9%(P<0.05);C处理的年平均N_(2)O累积排放量降低了20.3%(P<0.05),而S和CS处理的N_(2)O年平均累积排放量分别增加了23.6%和41.4%(P<0.05)。(2)与CK处理相比,C、S和CS处理的土壤有机碳年平均变化量(ΔSOC)均有显著增加,其中CS处理增幅最大,增加了150.6%(P<0.05)。与第1年相比,C、S和CS处理第3年的ΔSOC均有显著增加(P<0.05),分别增加了21.7%、20.8%和17.8%。各处理的NGWP和GHGI均存在显著差异,与CK相比,C、S和CS处理的年平均NGWP分别降低了163.5%、171.7%和273.0%(P<0.05),与第1年相比,C、S和CS处理第3年的NGWP均有显著降低(P<0.05),分别降低了73.4%、58.8%和54.7%。与CK相比,C、S和CS处理的年平均GHGI分别降低了236.2%、253.3%和388.9%(P<0.05),C、S和CS处理第3年的GHGI较第1年分别降低了126.3%、98.2%和108.6%(P<0.05)。就产量而言,C、S和CS处理的作物产量保持相对稳定,有轻微增长,但与CK相比无显著差异。【结论】与单施化肥相比,在施化肥的基础上添加生物炭、秸秆还田、秸秆还田配施生物炭的措施均能够在不影响作物产量的前提下抑制增温潜势,其中秸秆还田配施生物炭能够最大程度地降低农田增温潜势,因此秸秆还田配施生物炭是增加农田固碳、缓解气候变化的一项有效措施。

华北平原冬小麦-夏玉米农田生态系统土壤自养和异养呼吸模型构建

土壤呼吸是陆地生态系统碳循环的重要过程,准确估算土壤呼吸对估算陆地生态系统碳源汇具有重要意义。通过在华北平原典型农田内开展土壤呼吸及其组分的原位观测实验,构建了适用于华北平原冬小麦-夏玉米轮种制农田生态系统的半经验半机理土壤异养呼吸和土壤自养呼吸模型。结果表明,冬小麦-夏玉米农田土壤异养呼吸模型可表达为土壤温度和土壤水分的函数,其中,土壤温度对土壤异养呼吸的影响适合用Arrhenius方程描述,而土壤水分的影响适合用对称的倒抛物线描述。验证表明,该模型的R^(2)和RMSE分别为0.68和0.52μmol m^(-2)s^(-1)。土壤自养呼吸模型包括维持呼吸和生长呼吸两个模块,其中,维持呼吸表达为土壤温度和叶面积指数的函数,其形式分别为Van′t Hoff指数方程和米氏方程;生长呼吸表达为总初级生产力与维持呼吸之差的线性函数。冬小麦季和夏玉米季土壤自养呼吸模型的结构相同,但是两种作物的模型参数差异较大。验证表明,冬小麦季土壤自养呼吸模型的R2和RMSE分别为0.64和0.50μmol m^(-2)s^(-1),夏玉米季土壤自养呼吸模型的R2和RMSE分别为0.67和0.37μmol m^(-2)s^(-1)。相比于不区分土壤异养呼吸和土壤自养呼吸的土壤总呼吸模型,本研究构建的土壤异养呼吸和土壤自养呼吸模型能够更加准确地模拟土壤呼吸的季节变化和年际变化过程,可为华北平原冬小麦-夏玉米轮种制农田生态系统的土壤呼吸估算提供方法依据。

减氮下不同肥料配施对麦玉复种体系作物氮素积累分配及产量的影响

为探索陕西关中地区冬小麦-夏玉米复种体系氮肥减量增效潜力,构建适宜的作物养分管理体系,于2018-2019年采用田间试验研究了减氮并配施不同肥料对麦玉复种体系作物生长状况、植株氮素积累分配、作物产量以氮素利用效率的影响。试验设置5个处理:常规施氮(225 kg·hm^(-2),N 100);减氮20%(180 kg·hm^(-2),N 80);减氮配施生物炭(180 kg·hm^(-2),生物炭22500 kg·hm^(-2),N 80+BC);减氮配施缓释肥(180 kg·hm^(-2),尿素∶缓释肥=1∶1,N 80+S);减氮配施微生物菌肥(180 kg·hm^(-2),微生物菌肥3600 kg·hm^(-2),N 80+BF)。结果表明:减氮及其配施不同肥料对夏玉米大喇叭口期后株高、干物质和氮素积累没有显著影响;而N 80+BF促进了夏玉米氮素向籽粒中的分配;N 80+BC提高了夏玉米产量和收获指数,且较N 80处理分别显著提高8.3%和20.1%;减氮下三种配施处理均能提高夏玉米氮农学利用率和氮肥偏生产力,且以N 80+BC处理表现最佳,较N 100分别显著提高43.3%和29.0%,较N 80分别显著提高45.8%和8.3%;N 80+BC和N 80+BF还能显著提高夏玉米氮肥表观表观回收率,二者较N 100显著增加18.1%和10.7%,较N 80处理显著增加26.9%和19.0%。与N 80相比,N 80+BF有效提高了冬小麦扬花期和成熟期分蘖数、茎蘖成穗率以及成熟期干物质和氮素积累量,并能显著提高冬小麦穗数和产量,增幅分别为13.7%和16.2%。减氮下3种配施处理均能提高冬小麦氮农学利用率、氮肥偏生产力和氮素利用率,其中氮农学利用率和氮肥偏生产力在N 80+BF处理表现最佳,较N 100分别显著提高了31.2%和28.4%,较N 80分别显著提高了33.7%和16.2%,氮素利用率在N 80+S处理表现最佳。综上所述,减氮及其配施处理中,180 kg·hm^(-2)配施生物炭(22500 kg·hm^(-2))和180 kg·hm^(-2)配施微生物菌肥(3600 kg·hm^(-2))更有利于作物生长,促进氮素积累与分配,提高作物产量和氮素利用效率,实现关中地区麦玉复种体系氮肥管理的“减量增效”。

不同锌源叶面喷施对冬小麦和夏玉米产量及籽粒营养品质的影响

为探明不同锌源叶面肥喷施对小麦和玉米产量、籽粒矿质元素含量及锌、铁生物有效性的影响,对冬小麦-夏玉米轮作体系开展不同叶面肥喷施试验。小麦季设置去离子水(CK1)、尿素(CK2)、尿素+纳米氧化锌(U+ZnO)、尿素+壳聚糖纳米锌(U+ZnCNP)、尿素+普通七水硫酸锌(U+Zn)5种叶面肥处理;玉米季增加尿素与锌铁硒多元混合喷施处理(U+Zn/Fe/Se)。结果表明:各叶面肥喷施处理对小麦和玉米籽粒产量均无显著影响,但对籽粒微量元素含量有显著影响。不同锌源与尿素混合叶面肥对小麦籽粒锌含量强化效果由弱到强依次为U+ZnCNP<U+ZnO<U+Zn。与CK2处理相比,处理U+Zn使小麦籽粒锌含量显著提高77.7%(从22.80 mg·kg^(-1)增加至40.52 mg·kg^(-1))、籽粒植酸与锌(PA/Zn)摩尔比显著下降42.1%,使籽粒锌生物有效性(TAZ)显著提高74.5%。对于玉米,与CK2处理相比,处理U+Zn/Fe/Se使籽粒锌含量提高32.3%(从14.93 mg·kg^(-1)增加至19.60 mg·kg^(-1))、硒含量显著提高12.7倍(从17.66μg·kg^(-1)增加至242.04μg·kg^(-1))、籽粒PA/Zn摩尔比显著下降27.0%,使籽粒TAZ显著提高36.9%,使整个植株或玉米秸秆磷与锌(P/Zn)和磷与铁(P/Fe)摩尔比降低。研究表明,叶面喷施普通七水硫酸锌是提高小麦、玉米籽粒锌含量和生物有效性的最佳形式,其强化小麦籽粒锌效果优于玉米。叶面喷施尿素与锌铁硒混合溶液可同时提高玉米籽粒锌、硒含量及锌、铁生物有效性(籽粒、全株、秸秆),是解决人体或动物微量元素营养缺乏的有效农艺强化措施。

水氮耦合对地下滴灌冬小麦和夏玉米水氮利用效率影响研究

【目的】探索冬小麦、夏玉米地下滴灌条件下最佳灌水施氮制度。【方法】采用田间试验方法,分别设置4个灌水水平,冬小麦:W1:2580 m^(3)/hm^(2)、W2:2240 m^(3)/hm^(2)、W3:2020 m^(3)/hm^(2)、W4:1560 m^(3)/hm^(2),夏玉米:W1:1306 m^(3)/hm^(2)、W2:1088 m^(3)/hm^(2)、W3:814 m^(3)/hm^(2)、W4:650 m^(3)/hm^(2),2个施氮水平,冬小麦、夏玉米均为:F1:180 kg/hm^(2)、F2:100 kg/hm^(2),研究水氮耦合对冬小麦、夏玉米水氮利用效率及产量影响。【结果】W2F1处理冬小麦产量最大,继续增加灌水量冬小麦产量并未增加,而夏玉米产量随灌水量增加而增加;土壤氮素残留量均表现为F1处理>F2处理,且冬小麦氮素残留量随灌水量增加先减少后增加,W1处理夏玉米氮素残留量最大,冬小麦、夏玉米氮肥偏生产力均与产量变化趋势一致;冬小麦、夏玉米耗水量均随灌水量增加而增加,水分利用效率均随灌水量增加呈先增大后减小趋势。【结论】拟合优化表明,冬小麦的适宜灌水量为214 mm,适宜施氮量100 kg/hm^(2);夏玉米适宜灌水量为103 mm,适宜施氮量100 kg/hm^(2)。