Nitrogen absorption by alpine forage species based on 15N tracer technique in a hydroponic culture

Based on 15N tracer technique,absorption of different concentrations of ammonium nitrogen(N-NH^(4+)),nitrate nitrogen(N-NO^(3-))and glycine(NGly)by root of six species of alpine forage(Puccinellia tenuiflora,Poa crymophila,Festuca sinensis,Elymus nutans,Elymus sibiricus and Bromus inermis)was studied in a hydroponic culture.The uptake kinetic parameter was analyzed according to Michaelis-Menten equation.The Michaelis-Menten equation represents the velocity equation for the relationship between the initial rate of an enzymatic reaction and the substrate concentration.The result showed that the absorption range of ammonium nitrogen,nitrate nitrogen and glycine by root of six species of alpine plant were 1.1-20.9μmol·g^(-1)·h^(-1),0.4-3.4μmol·g^(-1)·h^(-1) and 0.1-3.7μmol·g^(-1)·h^(-1),which accounts for 68.8%-74.7%,12.0%-27.0%and 4.3%-13.4%of total absorptivity,respectively.The six kinds of P.tenuiflora,P.crymophila,F.sinensis,E.nutans,E.sibiricus and B.inermis showed significant difference in nitrogen absorption.At the same concentration,the absorption of nitrogen in different forms of the same herbage is different.The absorptive amount of ammonium nitrogen was the highest among them,then the glycine,the nitrate nitrogen was least absorbed.The results could provide a theoretical basis for nitrogen utilization in alpine forages.For example,P.tenuiflora showed a much higher ability of absorbing nitrogen nutrition in a high salt environment and could be a more suitable herbage to be planted in saline-alkali soil in the Qinghai-Tibet Plateau as compared with E.nutans.

Long-term impacts of land-use change on dynamics of tropical soil carbon and nitrogen pools

Land-use changes, especially the conversion of native forest vegetation to cropland and plantations in tropical region, can alter soil C and N pools and N availability for plant uptake. Deforestation, followed by shifting cultivation and establishment of rubber tree plantation, is a common land-use change in Xishuangbanna, southwest China. However the influence of this kind of land-use change on soil C and N dynamics in this region remains poorly understood. This study was conducted to assess the effects of land-use change on soil C and N pools. Soil samples were collected on five adjacent plots, which belong to three land-use types including secondary forest-an acuminate banana(Musa itinerans) secondary forest and a male bamboo(Dendrocalamus membranaceae) secondary forest, shifting cultivation, and rubber tree (Hevea brasiliensis (H.B.K.) Muell. Arg.) plantation(one plot is 3-year-old, and another is 7-year-old). We measured soil bulk density (BD), pH value, moisture content and concentrations of soil organic carbon(SOC), total soil nitrogen(TSN), and inorganic N(NO - 3-N and NH + 4-N ) at 0—3, 3—20, 20—40 and 40—60 cm depths, and calculated C and N pools in 0—20, 20—40, 40—60, and 0—60 cm soil layers. Compared with the adjacent secondary forests, shifting cultivation and establishment of rubber tree plantations resulted in significant decline in concentrations and stocks of SOC and TSN in 0—20 and 0—60 cm soil layers, and increase in pH and bulk density at 0—3, 3—20, and 20—40 cm depths. Soil moisture content decreased only in 0—20 cm surface soils in shifting cultivation and plantations. The dynamics of mineral N was much more complex, which had different trends among depths and ecosystems. Compared with the secondary forests, SOC stocks in 0—20 cm surface soils in shifting cultivation and rubber tree plantations(3-year-old plantation and 7-year-old plantation) decreased by 34.0%, 33%, and 23%; and TSN stocks decreased by 32 2%, 20.4%, and 20.4%, respectively, whereas the decreases of SOC and TSN stocks in 0—60 cm soil layers were much less. The results indicated that C and N losses were mainly occurred in 0—20 cm surface soil, followed by 20—40 cm layer.

Effects of Integrated Organic and Inorganic Fertilizers on Yield and Growth Parameters of Rice Varieties

We investigated the effects of integrated organic and inorganic fertilizers on the growth and yield of indica rice variety Manawthukha and japonica rice variety Genkitsukushi.In a split-plot design,the two rice varieties were assigned as main plot factors,and the integrated treatments were the subplot factors,including no-N fertilizer(N0),50%chemical fertilizer(CF)(CF50),100%CF(CF100),50%CF+50%poultry manure(PM)(CF50PM50),50%CF+50%cow manure(CM)(CF50CM50),and 50%CF+50%compost(CP)(CF50CP50).CF100 was equivalent to N at 85 kg/hm2.Manure was applied based on the estimated mineralizable nitrogen(EMN)level,which is dependent on total N(%)of each manure type.Manawthukha rice plants were taller with higher tiller number and dry matter content.However,higher soil-plant analysis development(SPAD)values were measured in Genkitsukushi throughout the crop growth period,resulting in higher seed-setting rate(%)and greater yield.At the same N level,CF50PM50 application in both rice varieties resulted in higher SPAD values,plant height and tiller number than CF100.CF50PM50 containing total N more than 4%supplied synchronized N for the demands of the rice plants,resulting in maximum dry matter,yield and yield components.CF50CM50 and CF50CP50 treatments containing total N less than 4%resulted in lower yields which were similar to CF100.These results indicated that integrating organic and inorganic fertilizers enhanced growth parameters and yields of Manawthukha and Genkitsukushi,while reducing the dose of chemical fertilizer.

Effects of Nitrogen Forms on Carbon and Nitrogen Accumulation in Tomato Seedling

Utilization of organic nitrogen （N） is an important aspect of plant N assimilation and has potential application in sustainable agriculture. The aim of this study was to investigate the plant growth, C and N accumulation in leaves and roots of tomato seedlings in response to inorganic （NH4^＋-N, NO3^-N） and organic nitrogen （Gly-N）. Different forms of nitrogen （NH4^＋-N, NO3^--N, Gly-N） were supplied to two tomato cultivars （Shenfen 918 and Huying 932） using a hydroponics system. The plant dry biomass, chlorophyll content, root activity, total carbon and nitrogen content in roots and leaves, and total N absorption, etc. were assayed during the cultivation. Our results showed that no significant differences in plant height, dry biomass, and total N content were found within the first 16 d among three treatments; however, significant differences in treatments on 24 d and 32 d were observed, and the order was NO3^--N 〉 Gly-N 〉 NH4^＋-N. Significant differences were also observed between the two tomato cultivars. Chlorophyll contents in the two cultivars were significantly increased by the Gly-N treatment, and root activity showed a significant decrease in NHa^＋-N treatment. Tomato leaf total carbon content was slightly affected by different N forms; however, total carbon in root and total nitrogen in root and leaf were promoted significantly by inorganic and organic N. Among the applied N forms, the increasing effects of the NH4^＋-N treatment were larger than that of the Gly-N. In a word, different N resources resulted in different physiological effects in tomatoes. Organic nitrogen （e.g., Gly-N） can be a proper resource of plant N nutrition. Tomatoes of different genotypes had different responses under organic nitrogen （e.g., Gly-N） supplies.

Effects of freezing intensity on soil solution nitrogen and microbial biomass nitrogen in an alpine grassland ecosystem on the Tibetan Plateau,China

The change of freeze-thaw pattern of the Tibetan Plateau under climate warming is bound to have a profound impact on the soil process of alpine grassland ecosystem;however,the research on the impact of the freeze-thaw action on nitrogen processes of the alpine grassland ecosystem on the Tibetan Plateau has not yet attracted much attention.In this study,the impact of the freezing strength on the soil nitrogen components of alpine grassland on the Tibetan Plateau was studied through laboratory freeze-thaw simulation experiments.The 0–10 cm topsoil was collected from the alpine marsh meadow and alpine meadow in the permafrost region of Beilu River.In the experiment,the soil samples were cultivated at –10℃,–7℃,–5℃,–3℃ and –1℃,respectively for three days and then thawed at 2℃ for one day.The results showed that after the freeze-thaw process,the soil microbial biomass nitrogen significantly decreased while the dissolved organic nitrogen and inorganic nitrogen significantly increased.When the freezing temperature was below –7℃,there was no significant difference between the content of nitrogen components,which implied a change of each nitrogen component might have a response threshold toward the freezing temperature.As the freeze-thaw process can lead to the risk of nitrogen loss in the alpine grassland ecosystem,more attention should be paid to the response of the soil nitrogen cycle of alpine grasslands on the Tibetan Plateau to the freeze-thaw process.

Temperature Sensitivity of Nitrogen Dynamics of Agricultural Soils of the United States

Soil temperature controls gaseous nitrogen losses through nitrous oxide (N2O) and ammonia (NH3) fluxes. Eight surface soils from agricultural fields across the United States were incubated at 10°C, 20°C, and 30°C, and N2O and NH3 flux were measured twice a week for 91 and 47 d, respectively. Changes in cumulative N2O and NH3 flux and net N mineralization at three temperatures were fitted to calculate Q10 using the Arrhenius equation. For the majority of soils, Q10 values for the N2O loss ranged between 0.23 and 2.14, except for Blackville, North Carolina (11.4) and Jackson, Tennessee (10.1). For NH3 flux, Q10 values ranged from 0.63 (Frenchville, Maine) to 1.24 (North Bend, Nebraska). Net soil N mineralization-Q10 ranged from 0.96 to 1.00. Distribution of soil organic carbon and total soil N can explain the variability of Q10 for N2O loss. Understanding the Q10 variability of soil N dynamics will help us to predict the N loss.

秸秆还田与氮肥运筹对农田土壤可溶性氮组分的影响

为探究秸秆还田配施氮肥对农田土壤可溶性氮转化特征的影响,研发东北冷凉区土壤氮素供应能力提高的秸秆还田技术,采用田间连续定位试验,对比分析了秸秆还田方式(不还田、粉碎翻压还田、堆腐旋耕还田)与氮肥运筹(N 180、210、240 kg/hm^(2);氮肥基施、氮肥后移)作用下农田土壤无机氮(IN)、可溶性有机氮(DON)及可溶性全氮(DTN)的动态变化。结果表明,秸秆还田配施氮肥影响农田土壤可溶性氮组分含量,其作用行为受秸秆还田方式、施氮模式和生育时期的多重制约。秸秆还田配施低量氮肥(N 180 kg/hm^(2))土壤IN和DTN均低于无秸秆处理,而配施高量氮肥(N 240 kg/hm^(2))时高于无秸秆处理;秸秆还田土壤DON于生育前期(播种-拔节期)较无秸秆处理显著增加,而在生育中后期无规律性变化。随着施氮量增加,秸秆还田土壤IN和DTN显著增加,而DON仅于春玉米旺盛生长期(拔节期-灌浆期)显著增加。随着生育期推进,除秸秆堆腐旋耕还田土壤DON呈三峰曲线变化外,秸秆还田土壤IN、DON和DTN均呈双峰曲线变化,且峰值越来越低。由此可见,在东北农业产区,N 210 kg/hm^(2)用量下秸秆粉碎翻压还田配施15%氮肥的秸秆还田技术具有优化氮素管理、提高土壤肥力的潜力。

等氮量有机替代对水稻田面水氮素动态变化特征研究

为了防控高原湖泊流域稻田氮素径流流失,保护受纳水体生态环境。在洱海流域水旱轮作种植模式下,设置不施肥(CK)、单施化肥(NPK)、有机无机配施(NPKS)、有机肥全量替代(SS)4个等氮量有机替代处理,研究水稻田面水氮素浓度的动态变化特征,探讨有机肥替代化肥施用对田面水氮素流失的影响。试验结果表明:基肥施用后田面水NH_(4)^(+)-N、NO_(3)^(-)-N、Org-N和TN浓度迅速升高,在3~7 d内达到峰值,施肥后7 d是防止田面水氮素大量流失的关键风险期。等氮量有机替代种植,田面水中NH_(4)^(+)-N/TN浓度占比为39.01%~54.01%,NO_(3)^(-)-N/TN浓度占比为11.33%~21.62%,Org-N/TN浓度占比为33.85%~41.94%。化肥氮施用增加田面水NH_(4)^(+)-N/TN浓度占比,有机肥施用增加田面水NO_(3)^(-)-N/TN和Org-N/TN浓度占比。等氮量有机替代对田面水氮素浓度的响应随施肥天数的增加而减弱,田面水NH_(4)^(+)-N、NO_(3)^(-)-N、Org-N、TN的浓度变化呈一元二次多项式下降,基肥施氮后35~40 d田面水氮素浓度趋于稳定低水平。在3种有机替代种植方式中,NPKS处理可降低田面水氮素浓度,降低稻田氮素流失风险。

有机无机氮配施对高芥酸油菜绵油309产量及品质的影响

为探究有机无机氮配施对高芥酸油菜产量及品质的影响,本试验研究了6个不同处理(纯施有机肥、纯施无机肥、20%、30%、40%、50%有机肥替代量)对高芥酸工业型油菜(绵油309)产量、品质、土壤养分及经济效益的影响,以期为高芥酸工业型油菜的高产、提质、增效生产提供理论依据。结果表明:与单施化肥相比,一定比例有机无机氮配施可以显著提升油菜产量,30%有机氮配施处理产量最高,达3501.63 kg/hm^(2),较纯施有机肥显著增产24.84%,较纯施无机肥显著增产23.47%;有机无机氮配施促进油菜主序和分枝的生长发育。30%有机氮肥替代处理下在不影响芥酸含量的同时增加含油量,进而达到显著增加单位面积芥酸和食用油脂产量的目的;还能够提高土壤氮储量,从而使土壤维持较高肥力水平,实现油菜的减肥增效,以获得更高的经济效益和环境效益。

太湖地区稻麦轮作系统有机氮肥替代率的演变特征及其影响因素

有机肥替代化肥是化肥减量的关键措施。本研究的主要目标是明确太湖地区稻麦轮作体系中有机氮肥替代率的主要限制因素,为提高有机氮肥替代率提供理论基础。依托40 a长期定位观测试验,分别选择不施肥(CK)、单施化肥(NPK)和单施有机肥(OM)3个处理,研究有机氮肥替代率与土壤碳氮关系。其中,化肥采用尿素、过磷酸钙和氯化钾,年均施氮225~300 kg/hm^(2),年均施磷(P2O5)119.4 kg/hm^(2),年均施钾(K2O)179.1 kg/hm^(2);有机肥采用猪粪和菜籽饼,年均折合施氮103.1 kg/hm^(2),折合施磷(P2O5)82.7 kg/hm^(2),折合施钾(K2O)70.1 kg/hm^(2)。测定指标包括土壤有机碳、总氮,计算有机氮肥替代率和土壤碳氮比。结果表明,长期施肥提高了土壤有机碳水平,OM、NPK和CK处理土壤有机碳含量可用米氏方程拟合,且前10 a内快速累积、后30 a趋近平衡,平均含量分别为16.8、15.8、15.1 g/kg。长期施肥处理线性提高了土壤总氮含量,OM、NPK和CK处理土壤平均总氮含量分别为1.71、1.64、1.47 g/kg。有机氮肥替代率的时序演变可用分段线性模型拟合,有机氮肥替代率前期略降低后期增加,稻麦两季有机氮肥替代率的时间拐点分别出现在第11年和第15.5年。线性回归分析表明,有机氮肥替代率与土壤总有机碳无显著关系,但与土壤总氮和碳氮比显著线性相关。在太湖地区稻麦轮作系统中,长期施用有机肥可有效提高土壤碳氮库容,具有较高水平土壤有机碳(>17.0 g/kg)是提升有机氮肥替代率的前提,但在有机碳趋近饱和后,土壤总氮和碳氮比是限制有机氮肥替代率提升的主要因素。

基于APSIM模型的旱地春玉米施肥类型及氮肥用量研究

为探究玉米高产和减少硝态氮残留的合理施肥模式,通过山西寿阳旱地春玉米田间试验和APSIM模型模拟,研究不同施肥类型和施氮量对春玉米产量、硝态氮残留量和氮肥利用率的影响。田间试验设置3个施肥类型主处理,包括化肥单施、有机无机肥配施(配施比例1∶1)和有机肥单施;7个施肥梯度副处理,分别为0、50、100、150、200、250、300 kg·hm-2,并利用2019—2021年试验站点数据对模型进行校准验证。结果表明:APSIM模型可以较好地模拟当地玉米产量和硝态氮残留量状况。各降水年型下,随氮肥施用量的增加,玉米产量先增加后减少,硝态氮残留量显著增加,氮肥利用率有所降低;相同施肥类型及施肥量下,丰水年的春玉米作物产量最高,硝态氮残留量最低,氮肥利用率最高;相同降水年型及施肥量下,有机无机肥配施方式的春玉米产量最高,硝态氮残留量居中,氮肥利用率最高。相较于化肥单施和有机肥单施方式,有机无机肥配施对于干旱地区玉米产量提升效果更好,其土壤硝态氮残留量对降水变化的敏感性相对较低,其氮肥利用率受降水影响也更小。综上,当施氮量介于148~168 kg·hm-2时,有机无机肥配施方式下土壤硝态氮残留量维持在阈值内,春玉米产量可达到理论产量的95%左右,适宜在研究区域推广应用。

有机无机肥配施对西北地区不同土壤类型氮素矿化影响

为揭示不同施肥措施和土壤类型对我国西北地区典型农田土壤氮素矿化特征的影响,通过室内恒温好气培养法,分别研究不施肥(CK)、单施尿素(U)、单施有机肥(M)和尿素配施有机肥(U+M)施肥模式对土壤氮素矿化动态过程的影响,并对土壤累积矿化氮量进行一级动力学方程拟合及相关性分析。结果表明,施肥和土壤类型均显著影响土壤铵态氮含量、硝态氮含量和累积矿化氮量,且两者之间存在显著的交互作用。不同类型土壤累积矿化氮量和矿化速率由大到小依次为塿土、黄绵土、黄河灌淤土、灰棕漠土。与CK处理相比,不同施肥处理显著增加土壤累积矿化氮量、矿化速率常数(k)和矿化势(N0),处理间差异显著(P<0.05)。单施尿素和尿素配施有机肥处理的累积矿化氮量和矿化速率分别较CK处理增加2.83~6.71倍和3.83~7.70倍。相关分析表明,土壤累积矿化氮量与土壤有机质含量和全氮含量呈显著正相关关系。研究结果表明,有机无机肥配施处理可显著促进西北地区不同土壤类型氮素矿化,提高氮素有效性和供氮能力,有利于保持土壤矿质氮含量,对农田氮素高效利用有重要作用。

磷肥有机替代、秸秆还田对棉花养分吸收和磷肥利用效率的影响

为探究磷肥有机替代、秸秆还田对棉花养分吸收、磷肥利用效率及棉花产量的影响,本研究基于国家灰漠土肥力与肥料效益监测站5年田间微区棉花连作定位试验,以7种施肥措施为样本,于2022年棉花成熟期开展棉田土壤田间调查研究。结果表明,磷肥有机替代和秸秆还田均能提升棉株氮磷钾养分吸收,各器官氮素平均含量在1.75~40.90 g·kg^(-1)之间,磷素平均含量在1.46~11.28 g·kg^(-1)之间,钾素平均含量在3.11~25.03 g·kg^(-1)之间。综合肥料投入和养分吸收,50%的磷肥有机替代和秸秆还田最能增强棉株吸氮能力和促进干物质积累,50%的磷肥有机替代对棉株吸磷能力最强且最有利于实现棉花节肥增钾的效果。棉株各器官N:P变化范围为1.20~12.01,磷肥有机替代和秸秆还田使茎、叶、蕾/铃/壳的N∶P明显降低,棉株生物量、籽棉产量随茎、叶、蕾/铃/壳N∶P的降低而增加,本试验棉花生长更倾向于受N、P共同限制。磷肥利用率随有机替代量的增加从12.54%提升到33.04%,土壤磷素盈余量随有机替代量的增加从28.20 kg·hm^(-2)降低到19.66 kg·hm^(-2)。研究表明,在北疆灰漠土棉区采用50%磷肥有机替代,即施磷(P2O5)60.0 kg·hm^(-2)和配施羊粪9 784.8 kg·hm^(-2),对棉花产量、生物量、养分吸收的综合效应最优,值得推广应用。

减氮及有机替代对新疆棉田土壤氮素有效性和利用效率的影响

【目的】“连作+棉秆全量还田+高氮肥投入”是新疆绿洲棉花生产的主要技术措施之一。研究该体系下减少化肥用量对棉田土壤氮素转化和有效性的影响,以及等量有机肥替代化肥的效果,为优化施肥方案,提高氮肥利用率提供依据。【方法】于2021和2022年在新疆石河子市二连农试场开展棉花连续定位施肥试验,设置常规施氮量(CF),减施常规氮量的8%(CF-8%)、16%(CF-16%)和24%(CF-24%),在常规氮量下以有机肥替代其中8%(8%OF)、16%(16%OF)和24%(24%OF)的化肥,以及不施氮肥对照(CK),共8个处理。分析不同土层p H、电导率(EC)值、有机质、无机氮和活性有机氮含量、氮转化相关酶活性变化,计算氮肥利用率,并测定棉花产量。【结果】2021和2022年在CF处理基础上减少化肥施氮量,0—20、20—40 cm土层颗粒有机氮(PON)、轻组有机氮(LFON)含量无明显变化,而CF-16%处理可溶性有机氮(DON)和微生物量氮(MBN)占全氮(TN)的比例较CF处理分别提升14.79%和19.88%,0—20 cm土层土壤蛋白酶活性也得到显著增强。CF-24%处理0—20 cm土层微生物量氮(MBN)含量、土壤硝酸还原酶、亚硝酸还原酶活性较CF处理分别下降了10.78%、16.88%、6.25%。随着化肥施用量的减少,深层土壤中累积的NH_(4)^(+)-N与NO_(3)^(-)-N含量降低,减氮处理中CF-16%处理较CF处理的增产率最高,达6.59%。与CF处理相比,16%OF、24%OF处理显著提高了20—40 cm土层土壤p H,0—20和20—40 cm土层有机质含量分别提升了23.44%和12.99%、31.74%和20.14%,土壤EC值分别下降了7.74%和4.72%、5.64%和7.02%,能够改善棉田土壤环境。16%OF处理0—40 cm各土层颗粒有机氮和可溶性有机氮含量两年平均较CF处理分别增加了24.01%和29.15%、18.95%和55.32%,颗粒有机氮和可溶性有机氮在全氮中的占比分别增加了16.32%和32.42%,而24%OF处理的轻组有机氮含量、LFON/TN、MBN/TN、C/N在3个有机替代处理中均为最高。16%OF处理的氮肥农学利用率、氮肥偏生产力、氮肥贡献率、单铃重与产量均高于8%OF和24%OF处理,增产率达17.16%。【结论】适量减施无机氮肥能够减少土壤中无机氮的累积,提升棉花氮肥利用率和产量,以CF-16%处理表现较佳。有机肥替代部分化肥能够增加土壤中活性有机氮的含量和土壤氮转化酶活性,提高土壤供氮潜力,改善棉田土壤微环境,并通过降低20—60 cm深层土壤中的NO_(3)^(-)-N含量提升棉花氮肥利用率,增加棉花单铃重与籽棉产量,其中16%OF处理为本试验最优处理,棉花增产17.16%。

有机肥部分替代化肥对河套灌区土壤有机碳和向日葵产量的影响

【目的】揭示河套灌区不同种类和比例有机肥替代化肥对土壤肥力和向日葵产量的影响,筛选土壤有机碳与向日葵产量协同提升的有机无机肥配施模式。【方法】设置不施肥(CK)、常规施化肥氮(MN)、20%羊粪有机肥氮+80%化肥氮(SN1)、40%羊粪有机肥氮+60%化肥氮(SN2)、20%牛粪有机肥氮+80%化肥氮(CN1)、40%牛粪有机肥氮+60%化肥氮(CN2)、20%猪粪有机肥氮+80%化肥氮(PN1)、40%猪粪有机肥氮+60%化肥氮(PN2)8个处理,分析不同种类和比例有机肥替代化肥对土壤有机碳含量、全氮含量、铵态氮浓度、硝态氮浓度、无机氮浓度、团聚体组成以及向日葵植株性状、地上部生物量、产量、氮肥利用率的影响。【结果】与MN处理相比,施用羊粪有机肥氮对土壤有机碳含量无显著影响(P>0.05),牛粪或猪粪有机肥氮可显著提高土壤有机碳含量(P<0.05),且提升效应随有机肥用量的增加而增加;CN1处理土壤铵态氮、硝态氮和总无机氮浓度分别显著增加9.7%、6.0%和7.6%(P<0.05);PN2处理土壤大团聚体质量比例显著提高29.3%(P<0.05)。与MN处理相比,CN1和PN1处理向日葵盘径和千粒重显著提高5.8%和4.0%(P<0.05);向日葵地上部生物量显著增加4.6%和12.8%(P<0.05);产量和氮肥利用率显著提高(P<0.05),其中CN1处理增幅最高,为14.3%和66.1%。【结论】20%牛粪/猪粪有机肥氮+80%化肥氮处理有利于土壤有机碳含量的提高以及向日葵盘径、千粒重、产量、氮肥利用率的增加,能够实现土壤有机碳含量和向日葵产量的同步提升,可作为河套灌区低肥力耕地的适宜有机无机肥配施技术模式。

不同比例有机肥替代化肥对夏玉米氮肥利用率及N_(2)O排放的影响

2022—2023年连续2 a设置不施肥(CK)、常规施肥(CF)、有机肥替代10%化肥(FM1)、有机肥替代30%化肥(FM2)和有机肥替代50%化肥(FM3),共5个处理,探究有机肥替代不同比例化肥对玉米产量和植株氮素吸收利用的影响。结果表明,与CF处理相比,FM1、FM2、FM3处理的2 a平均土壤容重分别降低1.43%、2.15%、4.67%,2 a平均土壤孔隙度分别增加2.07%、2.60%、5.51%,2 a平均硝态氮含量分别增加9.67%、14.86%、11.01%。与CF处理相比,FM1处理玉米植株2 a平均干物质累积量和产量分别增加3.41%、3.42%,FM3处理分别减少3.25%、6.73%。与CF处理相比,FM1处理2 a平均氮素累积量增加4.49%,2 a平均氮肥利用率和氮肥农学利用率分别增加13.62%、6.11%,2 a平均经济效益增加2.87%,2 a平均一氧化二氮(N_(2)O)排放量减少16.41%,且FM1处理增加了茎秆、叶片的氮素累积量。当有机肥替代化肥比例在30%及以上时(FM2、FM3处理),产量和氮肥利用率明显降低,经济效益减少。综上,有机肥替代10%化肥可以显著提高氮肥利用率,减少N_(2)O排放量,是实现氮肥减施和农业绿色高产的推荐有机肥替代化肥比例。

有机氮部分替代化学氮对烤烟产质量及化学成分的影响

为明确有机氮(腐熟牛粪中的有机氮)替代化学氮的最佳比例,减少化学氮肥施用量,该研究采用田间试验,分析了有机氮部分替代化学氮对烤烟农艺性状、产质量以及烤后烟常规化学成分的影响。结果表明:在农艺性状方面,20%和40%的替代比例能够显著促进烟株的生长发育,综合农艺性状优于对照常规施肥CK和60%替代比例;在经济性状方面,40%替代比例的综合经济性状最优,20%替代比例次之,但2个处理差异不显著;在烤后烟化学成分方面,20%替代比例处理的化学成分及各成分之间的协调性较好。综合农艺性状、经济性状、化学成分协调性3个方面的表现,20%有机氮替代化学氮的综合表现最佳,40%替代比例次之。

有机肥部分替代化肥对玉米产量和氮素利用率的影响

为明确浙南地区黄红壤土玉米有机肥替代化肥方案,进行有机肥替代化肥对玉米产量及氮素利用率的影响试验。田间试验分别设置不施肥处理(CK)、氮磷钾肥处理(NPK)、磷钾肥处理(PK)、15%基施有机肥等氮替代化肥处理(T15)、30%基施有机肥等氮替代化肥(T30)处理。结果表明:与NPK处理相比,T30处理的秸秆产量降低17.11%,T15和T30处理的籽粒氮含量分别降低16.73%和17.83%,T15和T30处理的籽粒吸氮量分别降低15.00%和20.30%,T30处理的秸秆吸氮量降低31.75%,T15和T30处理的氮素内部利用率分别提高23.10%和28.61%,T30处理的土壤铵态氮含量降低24.61%。本研究表明,有机肥氮替代15%~30%化肥氮可保持玉米不减产,提高土壤肥力和氮素利用率,减少化肥施用量,适宜在浙南玉米生产中推广应用。

陇东旱塬覆膜玉米产量和氮肥利用率对秸秆还田与减氮的响应

为探索秸秆还田与减氮对旱地覆膜玉米(Zea mays)产量、土壤氮素形态及氮肥利用率(NUE)的影响,开展了连续5年的玉米连作定位试验,处理包括常规施氮(225 kg·hm^(-2), F)、秸秆还田(9 000 kg·hm^(-2), TS)、F+TS、80%F+TS、60%F+TS和不施肥+不还田(CK)。结果表明:与F+TS处理相比,80%F+TS处理显著提高玉米产量(P <0.05),表现为第2年增产率最高达22.1%,第3年开始增产率逐年降低;而60%F+TS处理前3年增产,第4年增产率减少,甚至减产。5年累积产量显著增加6.8%(P <0.05)。同时,80%F+TS处理显著提高表层(0-20 cm)土壤碱解氮含量,显著降低有机质和硝态氮含量(P <0.05),全氮含量无显著变化(P> 0.05),但显著降低了深层(20-40 cm)土壤全氮和硝态氮含量,显著增加有机质和碱解氮含量,而且80%F+TS处理也显著提高了氮肥利用率,2019和2020年较F+TS处理分别提高了23.7%和22.1%(P <0.05)。因此,秸秆还田9 000 kg·hm^(-2)替代20%的化肥氮是陇东黄土旱塬区秸秆还田减氮增效的优化组合模式,研究结果为陇东黄土旱塬区农业减氮增效绿色发展提供了依据。