春玉米产量、氮素利用及矿质氮平衡对施氮的响应

通过在辽宁省昌图县的田间试验,研究了不同施氮水平(0、60、120、180、240和300 kg hm-2)对春玉米产量、氮素利用及农田矿质氮平衡的影响。结果表明:春玉米产量随施氮量增加而显著提高,当施氮量高于N 240 kg hm-2时,产量有减少趋势;氮素当季利用率随施氮量增加先增加后降低,在施氮量180 kg hm-2时达到最大,为27.95%。随着施氮量增加,氮肥农学利用率、氮素吸收效率和氮素偏生产力均显著降低,而氮肥生理利用率和氮肥表观残留率均先增加后降低,这与氮肥表观损失率的变化正好相反。作物吸氮量随施氮量增加而显著增加,氮盈余主要以土壤残留为主,表观损失在氮盈余中的比例虽小,但随着施氮量增加而明显增加。低量施氮(<180 kg hm-2)主要引起土壤矿质氮残留量的显著增加,而高量施氮(240 kg hm-2和300 kg hm-2)主要引起土壤氮素表观损失量的显著增加。在本试验条件下,合理施氮量应控制在180～209 kg hm-2左右。     

尼日利亚两个农业生态区施用氮肥和杂草干扰对热带玉米基因型的影响

Low soil nitrogen (N) and weed infestations are some of the major constraints to maize production in Nigeria.A split-split plot experiment in a randomized complete block design with three replicates was established at two sites with different agroecological zones,Ikenne (Typic Paleudalf) and Shika (Typic Tropaquept),in Nigeria in 2002 and 2003 rainy seasons to investigate the responses of four maize genotypes (Oba super II,Low N pool C2,TZB-SR,and ACR 8328 BN C7) to N fertilizer applied at four rates,0,30,60,and 90 kg N ha^-1,and three weed pressure treatments,no weed pressure (weekly weeding),low weed pressure (inter-row weekly weeding),and high weed pressure (no weeding throughout the growing season).Growth and yield parameters of maize and weeds were taken at flwering and harvest.The results indicated that there was a significant reduction in maize leaf area,leaf area index,and photosynthetically active radiation due to weed interference at both sites.The application of nitrogen at 90 kg N ha^-1 significantly increased maize leaf area.Reductions in maize growth and yield at flowering and harvest were significant due to weed interference at both Ikenne and Shika,thus showing that the reductions in maize growth and yield due to weed interference were not ecological zone specific even though weed species and their seed banks may differ.Ameliorative management options could thus be the same in the two agroecological zones.Application of 90 kg N ha^-1 led to a significant increase in maize grain yield at Shika while there was no fertilizer effect at Ikenne on grain yield.There was no significant difference between 60 and 90 kg N ha^-1,suggesting that 60 kg N ha^-1 could be a possible replacement for the higher fertilizer rate at least for the identified maize genotypes.Low weed pressure treatment led to 26% and 35% reductions in maize grain yield at Ikenne and Shika,respectively,while 22% and 51 % reductions,respectively,were observed due to high weed pressure.Generally,maize grain yield was higher at Ikenne than Shika.The maize genotypes Low N pool C2 and ACR 8328 BN C7 performed better than the other genotypes at Ikenne while the maize genotype Oba super II had the best performance at harvest at Shika.Application of nitrogen increased weed biomass at flowering at Ikenne.The maize grain yield was highest in the N-efficient genotypes,Oba super II and Low N pool C2;the susceptible genotype TZB-SR had the least yield at Shika.There existed a negative and significant correlation between maize grain yield and weed biomass at both sites.     

Assessment of nitrogen uptake and utilization in drought tolerant and Striga resistant tropical maize varieties

Maize (Zea mays L.) is an important food crop in the Guinea savannas of Nigeria. Despite its high production potential, drought, Striga hermonthica parasitsim, and poor soil fertility particularly nitrogen deficiency limit maize production in the savannas. Breeders at IITA have developed drought- and Striga-tolerant cultivars for testing, dissemination, and deployment in the region. Information on the response of these cultivars to N fertilization is, however, not available. This study evaluated grain yield, total N uptake (TNU), N uptake (NUPE), N utilization (NUTE), and N use efficiency (NUE) of selected maize cultivars along with a widely grown improved maize cultivar at two locations in the Guinea savannas of northern Nigeria. Maize grain yield increased with N application. The average grain yield of the maize cultivars was 76% higher at 30, 156% higher at 60, and 203% higher at 120 kg N ha^?1 than at 0 kg N ha^?1. This suggests that N is a limiting nutrient in the Nigerian savannas. Five drought-tolerant cultivars produced consistently higher yields when N was added at all levels. These cultivars had either high NUPE or NUTE confirming earlier reports that high N uptake or NUTE improves maize grain yield. The study also confirms earlier reports that maize cultivars that are selected for tolerance to drought are also efficient in uptake and use of N fertilizer. This means that these cultivars can be grown with application of less N fertilizer thereby reducing investment on fertilizers and reduction in environmental pollution.     

Responses by earthworms to reduced tillage in herbicide tolerant maize and Bt maize cropping systems

Genetically modified (GM) crops may affect earthworms either directly through the plant, its root exudates and litter, or indirectly through the agricultural management changes that are associated with GM plant production. In order to investigate such possible effects, we established two field studies of Bacillus thuringiensis (Bt) maize and a glufosinate ammonium tolerant maize and included a reduced tillage (RT) treatment and a conventional tillage (CT) treatment as examples of a likely concomitant change in the agricultural practise. At a French study site at Varois, (Bourgogne), a field grown with the Bt-toxin producing transgenic maize line MON810 was studied for 1 year. At a Danish study site, Foulum (Jutland), 1 year of Bt maize was followed by 2 years of herbicide tolerant (HT) maize. At the French study site, the most prominent effects observed were due to the tillage method where RT significantly reduced the earthworm populations to levels about half of CT. At the Danish study site effects of CT complied with known reduction of anecic earthworms due to this technique and likewise effects of RT were observed for endogeic earthworms. Earthworm populations were diminished with the HT crop, probably due to exposure to the herbicide Basta^® during the two consecutive autumn seasons. This study confirms the importance of including the tillage techniques and pesticide usage when evaluating the environmental effects of new agricultural technologies.     

施氮量对潮土区冬小麦-夏玉米轮作农田氮磷淋溶的影响

潮土是我国华北地区主要土壤类型之一,潮土区是我国冬小麦-夏玉米作物的主要产区,研究不同施氮量潮土氮磷淋溶特征对于指导区域农田面源污染防控具有重要意义。本研究设置3个施肥处理,即传统施氮(CON)、优化施氮(OPT)和优化再减氮(OPTJ),利用田间渗漏池法,研究潮土冬小麦-夏玉米轮作农田硝态氮及总磷淋溶特征。结果表明:2016—2018年,冬小麦-夏玉米轮作周年不同施肥处理90cm土层年淋溶水量79.0～102.5 mm,不同淋溶事件间土壤淋溶液硝态氮浓度波动较大, CON、OPT和OPTJ处理单次淋溶事件硝态氮浓度分别为18.9～208.7(平均为72.7) mg·L~(-1)、9.0～99.2 (平均为33.8) mg·L~(-1)、4.7～55.5 (平均为15.4) mg·L~(-1)。本研究区域冬小麦-夏玉米轮作模式的氮素淋溶风险较高,磷素淋溶风险较低。传统施氮处理(CON)下农田硝态氮的平均淋溶量和表观淋失系数分别为66.4 kg·hm~(-2)和10.3%,而总磷(TP)为0.06 kg·hm~(-2)和0.04%。氮肥减施会显著降低氮素淋失,OPT和OPTJ处理的氮素淋溶减排率可达56.3%和78.9%。两个年度CON、OPT和OPTJ处理硝态氮平均表观淋失系数分别为10.3%、6.2%和4.9%,随着施氮量的增加,硝态氮淋失系数动态增加。氮淋溶具有较大的年际变化,降雨量高的2018年比降雨少的2017年硝态氮淋溶量多57.0%。两个年度CON、OPT和OPTJ处理总磷平均淋溶量分别为0.06 kg·hm~(-2)、0.06 kg·hm~(-2)和0.08 kg·hm~(-2)。适量减施氮肥会增加作物产量, OPT处理的作物产量是CON处理的1.08倍。然而,过量减施则会带来减产风险, OPTJ处理氮肥减施56%,作物产量比CON处理降低2.0%～8.1%。总之,潮土区农田硝态氮淋溶风险较大,适量减施氮肥能够在保证作物产量的基础上显著降低氮素淋失损失。     

滴灌水肥一体化条件下施氮量对夏玉米氮素吸收利用及土壤硝态氮含量的影响

河北山前平原夏玉米高产区施肥不合理现象普遍存在,农业面源污染严重。研究华北山前平原水肥一体化条件下夏玉米适宜的氮肥运筹,可为该区氮素优化施用技术及提高氮肥利用效率提供依据。本研究以‘郑单958’玉米品种为材料,于2014—2015年2个玉米生长季,在滴灌条件下设置4个施氮水平(N0:不施氮;N1:120 kg·hm~(-2);N2:240 kg·hm~(-2);N3:360 kg·hm~(-2)),研究滴灌水肥一体化下施氮量对玉米氮素吸收利用和土壤硝态氮含量的影响。结果表明:N0处理的玉米干物质重及产量较其他处理显著降低,N1、N2和N3处理间无显著差异;N1处理的玉米氮含量和氮累积量较N0处理显著增加,施氮量在N1~N3范围内,不同年份间玉米植株氮含量和氮累积量存在一定差异,总体表现为随施氮量的增加而上升的趋势,但随施氮量的增加,植株氮含量和氮累积量上升幅度逐渐降低。N2处理的氮肥收获指数最高。随施氮量增加,氮肥当季回收利用率、氮肥农学效率、氮肥生产效率和氮肥利用效率显著降低;2014年,在0~100 cm土层范围内,4种施氮处理的土壤硝态氮含量均表现为随土层加深逐渐降低;2015年N2和N3处理的土壤硝态氮在80~100 cm土层达到累积峰,经过2年种植后,年施氮量超过240 kg·hm~(-2)的处理,土壤硝态氮淋洗加剧。利用一元二次方程拟合产量与施氮量之间的关系,明确了玉米最高产量的施氮量为199~209 kg·hm~(-2),经济施氮量为174~187 kg·hm~(-2)。综合考虑经济效益和生态效益,该条件下夏玉米滴灌水肥一体化的适宜施氮量为174~187 kg·hm~(-2)。     

Response of baby corn genotypes to soil and foliar nitrogen application schedule

Responsive genotypes, timing and mode of nitrogen application are important for realizing potential yield of winter baby corn. Soil application of nitrogen is a common practice. Foliar application enhances absorption and utilization of nitrogen particularly after anthesis. We investigated combined approach in management of nitrogen for the first time including soil applications followed by foliar urea spray to enhance baby corn yield and profitability. To determine these, 2-year study conducted with three genotypes and six schedules of recommended dose of nitrogen (RDN). Growth characters, productivity traits, harvest period and yields recorded. Nitrogen content and uptake, protein content and harvest were determined. Genotype HM-4 produced 4.6% and 4.1% more cobs and corn weight over HQPM-1. Combined approach resulted higher yield attributes, yields, N uptake, protein harvest and monetary returns. RDN in 4 splits with more basal (B) dose increased cob and corn yield by 4.8% and 5.1% than 3 splits (50% B). Results suggest that HM-4 be grown using RDN 50% as B, 25% at knee height stage, 20% at tassel emergence followed by 5% foliar spray after first picking as urea solution (3%) for achieving higher yield and net returns. More studies needed under diverse conditions.     

减量施氮与间作大豆对华南地区甜玉米农田氮平衡的影响

本文在广东广州华南农业大学试验中心,通过大田定位试验(2015—2016年两年4季)对比了两种施氮水平[减量施氮(300 kg·hm~(-2),N1)和常规施氮(360 kg·hm~(-2),N2)]、3种种植模式[甜玉米单作(SS)、甜玉米//大豆2∶3间作(S2B3)、甜玉米//大豆2∶4间作(S2B4)]农田生态系统的氮素输入、输出和平衡状况,旨在为减少化学氮肥投入水平,提高氮素利用效率,在华南地区发展环境友好型的玉米可持续生产模式提供科学依据。结果表明:1)减量施氮与甜玉米//大豆间作降低了系统氮素总输入量,大豆固氮和秸秆还田降低了化肥氮输入的比重,与常规施氮相比,减量施氮下SS、S2B3和S2B4的化肥氮输入占年均氮素总输入的比例分别下降3.24%、3.64%和3.77%。2)间作大豆增加了系统籽粒氮素累积量,N1和N2处理甜玉米//大豆间作的年均籽粒氮素累积量分别是单作甜玉米的2.43倍和2.18倍;减量施氮与甜玉米//大豆间作能降低甜玉米农田氮素损失,N1和N2处理甜玉米//大豆间作的年均氨挥发量分别比单作甜玉米低39.02%和27.26%;间作甜玉米的氮淋溶量比单作低13.85%。3)减量施氮与间作大豆显著降低了系统氮素盈余量,S2B3-N1、S2B3-N2和S2B4-N1、S2B4-N2年均氮素盈余量分别为71.03 kg·hm~(-2)、133.7 kg·hm~(-2)和42.87 kg·hm~(-2)、100.64 kg·hm~(-2),分别比SS处理N1和N2的平均值减少81.27%、64.75%和88.69%、73.47%。因此,减量施氮甜玉米//大豆间作模式能维持系统作物产量、减少生产成本、降低环境污染风险,具有较高的经济和生态效益。     

玉米氮高效品种的生物学特征

提高氮肥利用率依赖于氮肥优化管理及作物氮素营养效率的遗传改良。本文分析了作物氮高效的定义,并以玉米为例,分析了氮高效的生物学机制,提出了玉米氮高效品种的生物学特征。本文认为,玉米氮高效品种的生物学特征为:(1)在开花前,维持稳定的氮吸收,并将所吸收的氮素高效利用于穗的发育,提高小花结实率,为产量形成过程中的碳、氮积累提供较大的库;根系生长发育能力强,能建成较大的根系,以满足籽粒生长期氮素吸收的要求;有较强的叶片扩展能力,保持较大的叶面积。(2)在开花后,充分利用前期建成的根系,高效吸收土壤中的矿化氮,用于籽粒生长所需,从而减少叶片中氮素的输出,减缓叶片衰老(保绿性强),维持叶片较高的光合效率,为籽粒灌浆提供碳化合物。因此,在氮高效育种中,应注重穗部性状(大穗,结实能力强)、根系性状(发达的根系,功能期长)与叶片性状(保绿性好)的结合。     

红芪氮素吸收和多糖积累规律及施肥响应

田间试验研究了红芪氮素吸收分配动态和多糖含量的变化规律, 以及增施3 种水平坡缕石(P1, 750kg·hm^-2; P2, 1 500 kg·hm^-2; P3, 2 250 kg·hm^-2)对红芪吸氮和多糖积累的影响。结果表明: 6 月下旬至7 月下旬是红芪茎叶对氮的营养临界期, 而红芪根在8 月下旬以后对氮的需求量增大, 9 月下旬至10 月下旬为氮素从茎叶向根系转移的时期, 6 月下旬至8 月下旬是红芪多糖含量的快速积累期。在红芪收获期, NPK+P3、NPK+P2 和NPK+P1 处理的全株氮素积累量分别比NPK 对照提高45.22%、29.45%和20.06%, NPK+P3 处理的茎叶氮素积累量比NPK 对照提高71.99%, NPK+P3、NPK+P2 处理的根氮素积累量分别比NPK 对照提高38.72%和26.07%;NPK+P1、NPK+P2 和NPK+P3 处理的多糖含量分别较NPK 对照提高50.74%、62.95% 和 40.63%。坡缕石配施用量对红芪吸氮的促进效果综合表现为高用量>中用量>低用量, 但其配施用量与多糖产量的关系还需进一步研究确定。     

Seasonal changes in periphyton nitrogen fixation in a protected tropical wetland

Cyanobacteria are important for global nitrogen cycle and often form complex associations referred to as cyanobacterial mats or periphyton that are common in tropical, limestone-based wetlands. The objective of this study was to monitor the nitrogen fixation rate using the acetylene reduction assay of these cyanobacterial mats in a tropical, unfertilized, and protected wetland. To account for temporal and spatial variation of nitrogenase activity, we were interested in seasons in a hydrological cycle (dry, rains, and end of rains), sites with different vascular vegetation, and rates of nitrogenase activity in a 24-h cycle. The annual average of nitrogenase activity was 22 nmol C₂H₄ cm⁻² h⁻¹, with a range of <6 to 35 nmol C₂H₄ cm⁻² h⁻¹, and the annual nitrogen fixation rate of our study site (9.0 g N m⁻² year⁻¹) is higher than similar estimates from other freshwater wetlands. There was a clear temporal pattern in nitrogenase activity with a maximum rate occurring during the rainy season (August) and a maximum nitrogenase activity occurring between 0600 and 1200 hours. We found spatial differences in nitrogenase activity among the four sites that could be attributed to variations in species composition within the periphyton.     

氮肥用量对玉米体内养分浓度和养分分配的影响

通过5年的田间试验,研究了不同施氮量对玉米产量、玉米体内养分浓度、养分分配及对每形成单位籽粒产量的吸收养分量的影响。结果表明,玉米籽粒和秸秆中P、K浓度随氮肥用量的增加有逐渐降低的趋势。玉米收获产品中N、K含量在籽粒和秸秆中的分配比与产量均呈现较好的相关性。玉米生长愈好(单产愈高),每形成单位经济产量的磷、钾消耗量愈少,说明良好的作物生长条件有利于提高作物体内养分的转化效率。     

施氮模式对夏玉米产量和籽粒灌浆的影响

为进一步明确夏玉米在基肥和拔节期施肥的基础上增施吐丝肥的增产机理,于2011年在中国农业大学吴桥试验站布置了田间试验。共设置4种施氮模式:即模式Ⅰ,施氮量90 kg·hm-2(播前90 kg·hm-2);模式Ⅱ,施氮量190 kg·hm-2(播前150 kg·hm-2+拔节40 kg·hm-2);模式Ⅲ,施氮量250 kg·hm-2(播前90 kg·hm-2+拔节160kg·hm-2);模式Ⅳ,施氮量300 kg·hm-2(播前50 kg·hm-2+拔节150 kg·hm-2+吐丝100 kg·hm-2)。本研究对比分析了不同施氮模式对夏玉米产量和籽粒灌浆的影响。结果表明,在施基肥和拔节肥的基础上,再追施吐丝肥,与不施吐丝肥的模式相比,其吐丝后11~20 d、21~30 d、31~40 d内,每天增加的枯叶数分别减少0.01~0.02片、0.01~0.05片、0.02~0.04片;吐丝后穗位叶SPAD值的峰值有所提高,灌浆中后期SPAD值下降延缓;模式Ⅳ与模式Ⅲ相比灌浆速率峰值提高8.5%,籽粒体积得到显著提高。夏玉米吐丝后籽粒的吸氮量显著提高(模式Ⅳ籽粒吸氮峰值分别是模式Ⅰ、Ⅱ、Ⅲ的1.65倍、1.45倍、1.31倍),氮收获指数增加2.5~13.3个百分点,穗粒数增加。与穗粒数相比,吐丝期增施氮肥(模式Ⅳ)对千粒重的促进更显著,可改善夏玉米产量因子和部分穗部性状,与模式Ⅰ、Ⅱ、Ⅲ相比,分别增产200 kg·hm-2、300 kg·hm-2、400 kg·hm-2。夏玉米增施吐丝肥可以延缓吐丝后光合面积下降,从而为籽粒灌浆提供较多的源,最终提高粒重和产量。     

半湿润农田杂草及施氮对夏玉米产量及氮素利用的影响

以土垫旱耕人为土为供试土壤,采用大田试验,研究了半湿润农田两种杂草处理方式下(成熟后期清除杂草-A区和苗期开始清除杂草-B区),不同施氮量对夏玉米产量及氮素利用效率的影响。结果表明,当施氮量为0、45、90、135、180 kg/hm2时,B区玉米子粒产量比A区分别增加了8.7%、12.1%、9.4%、5.0%和12.5%;吸氮量分别增加了1.5、2.9、4.8、5.2和4.3 kg/hm2。A区和B区全生育期0―100 cm土层矿质氮（Nmin）累积量变化趋势基本一致,但B区比A区变幅较大。当施氮量为45、90、135和180 kg/hm2时,B区氮肥利用率、氮肥农学利用率、氮肥生理利用率均高于A区。研究还发现,在A区,当施氮量为180 kg/hm2时,杂草干生物量最大,为1518.3 kg/hm2,不施氮时,杂草的生物量最低,为845.7 kg/hm2;杂草的吸氮量随施氮量的增加而增加。可见,清除玉米农田杂草不仅可以提高作物产量和氮肥利用率,而且在减少氮素损失方面具有一定作用。     

不同灌溉处理对夏玉米氮素吸收及转移的影响

通过田间试验, 研究了两个生长季夏玉米4 个不同水分处理(灌溉1 水、灌溉2 水、灌溉3 水、灌溉4 水)对其各个生育阶段氮素吸收、分配、转移的影响。结果表明, 拔节抽雄期灌水可以增加夏玉米茎叶的氮素积累量和氮分配比, 生育后期灌水各处理之间单株氮素积累量无显著差异; 穗部的氮素积累75%来源于扬花后期氮素同化吸收, 25%来自营养器官茎叶的氮素转移, 说明灌浆至成熟期穗部氮素主要吸收利用土壤中的氮, 充足的水分可以保证营养器官积累更多的氮素, 但后期同化氮素比率随着灌水的增加而减小。因此, 灌浆至成熟期需要维持适中的水分条件, 在保证吸收利用土壤氮素的同时, 增加储存在茎叶中的氮素向籽粒的转移, 从而提高氮素利用效率。     

Changes in an Alfisol under long-term application of manure and inorganic fertilizer

Abstract. Changes in surface soil properties of a savanna Alfisol under cultivation with applications of manure and inorganic NPK fertilizer were evaluated after 45 years of annual cropping. Soils from treatments with fertilizer only, fertilizer in combination with farmyard manure (FYM) at both high and low rates were compared to soil from a control receiving neither fertilizer nor manure. The high rate of FYM and fertilizer significantly improved soil aggregation, increased C, N and P status, while reducing soil penetration resistance. The results showed that there is a need to use both manure and inorganic fertilizer to maintain soil fertility in savanna soils under continuous cultivation.     

玉米苗期根系对氮胁迫反应的配合力分析

研究利用7个玉米自交系,采用NC-Ⅱ设计,分析了玉米苗期根系性状对氮胁迫反应的配合力及遗传参数变化。结果表明,在2个氮水平下,玉米苗期根系性状的一般配合力、特殊配合力都存在显著的基因型差异,而且不同的基因型在氮胁迫下的反应也不尽相同。高氮下,根系性状除轴根长以外均以非加性遗传为主;氮胁迫下,除轴根数以外的根系性状以加性遗传为主。2个氮水平下,根干重、总根长和侧根长的广义遗传力均较高;与高氮处理相比,在低氮胁迫下,根系性状的广义遗传力表现为下降趋势,根干重、总根长和侧根长的狭义遗传力有上升的趋势。     

施氮对不同基因型夏玉米干物质累积转移的影响

在黄土高原南部的红油土上,以陕单16、陕单9号、户单4号、陕资1号、掖单19号、中单2号、豫玉22号、陕单902号、农大108号和户单2000等10个当地常用的夏玉米品种为试材进行田间试验;在低氮（0 kg/hm2）和高氮（240 kg/hm2）水平下研究了不同夏玉米品种在子粒灌浆成熟期间干物质累积、转移及分配规律的差异。结果表明,夏玉米干物质累积及其转移效率受品种与氮素调控共同影响。不论施氮与否,各器官干物质量在不同品种间差异显著,施氮能明显提高各器官的干物质量,且其提高幅度因品种不同而明显差异。各个器官的干物质转移量、干物质转移效率和转移量对子粒的贡献率因品种和施氮量不同而异。不施氮处理下叶和茎转移量最大的是户单2000,转移量分别达到53.2和28.2 g/株,叶转移量最小的是中单2号,茎转移量最小的是陕资1号;施氮后叶转移量最高的是掖单19号,转移量分别达到54.7 g/株,茎转移量最高的是中单2号,转移量为52.4 g/株。不施氮处理下,除豫玉22号和陕资1号外,其它品种子粒干物质中50％以上来自于开花前期储存同化物的再转移;施氮后则所有品种的子粒干物质中50％以上均来自于开花前期储存同化物的再转移。干物质转移量对子粒的贡献率不施氮处理下穗部（苞叶和穗轴）大多数为负值,施氮后则为正值。对子粒的建成,叶干物质转移量贡献最大,其次为茎,穗部(穗轴和苞叶)最小。总体来说,干物质转移量、干物质转移率和干物质转移量对粒重的贡献率在不同品种间的差异大于施氮处理间的差异,施氮后的转移因品种而异。     

华北平原氮肥周年深施对冬小麦-夏玉米轮作体系土壤氨挥发的影响

氮肥深施能有效减少土壤氨挥发,然而目前国内外关于小麦-玉米轮作体系氮肥深施缺乏周年系统性研究。本试验于2018年10月—2019年10月在中国科学院栾城农业生态系统试验站小麦-玉米轮作农田进行,利用动态箱法研究不同深施模式氨挥发损失率、氨挥发特征,旨在探讨冬小麦-夏玉米轮作体系下土壤氨排放对氮肥深施的响应,为减少农业源氨排放和优化农田施肥提供理论依据。试验设置5个处理：不施肥（CK）、常规肥料表施（T₁）、缓释肥表施（T₂）、缓释肥基追肥分层深施（T₃）、缓释肥一次性分层深施（T₄）。结果表明：氨挥发主要发生在玉米追肥季,占全年氨挥发量的84.84%;T₁、T₂、T₃和T₄处理的周年氨挥发累积量分别为22.75 kg·hm^-2、6.17 kg·hm^-2、2.25 kg·hm^-2和0.55 kg·hm^-2,分别占总施肥量的4.86%、1.32%、0.48%和0.13%。与常规肥料表施（T₁）相比,缓释肥处理（T₂、T₃和T₄）分别降低72.88%、90.11%和97.32%的氨挥发损失;一次性深施处理（T₄）能避开土壤氨高挥发期,周年氨挥发累积量与不施肥处理（0.43 kg·hm^-2）没有显著差异,且显著低于表施处理。CK、T₁、T₂、T₃和T₄全年产量分别为8.31 t·hm^-2、13.20 t·hm^-2、12.66 t·hm^-2、14.42 t·hm^-2和14.22 t·hm^-2;与常规肥料表施（T₁）相比,缓释肥深施（T₃和T₄）均可提高作物产量,分别增产9.25%和7.75%。而缓释肥表施（T₂）产量略有降低。综合考虑土壤氨排放和作物产量,缓释肥表施（T₂）可以显著降低土壤氨挥发,但是作物产量不稳定;而氮肥深施（T₃、T₄）能在保证作物高产的基础上显著降低土壤氨排放,是一种高效、简便、环境友好的施肥方式。     

氮肥基施深度对夏玉米产量、 氮素利用及氮残留的影响

【目的】研究华北平原区底施氮肥深度对夏玉米产量、 氮素吸收量、 氮肥利用率以及氮素在土壤中残留的影响,以期为夏玉米的氮肥施用提供依据。【方法】采用小区试验和15N示踪试验的方法。小区试验设对照(CK),常规垄侧施氮(T-side),垄内8 cm深(T-8)、 16 cm深(T-16)、 24 cm深(T-24)施氮和垄内3层施氮(T-all)6个处理,养分施用量为N 180 kg/hm2,P2O5 120 kg/hm2,K2O 150 kg/hm2。示踪试验采用原位原状土柱法,设3个处理: 15N尿素施在8 cm深,另两层16 cm、 24 cm施用普通尿素(N8); 15N尿素施在16 cm深,另两层8 cm、 24 cm施用普通尿素(N16); 15N尿素施在24 cm深,另两层8 cm、 16 cm施用普通尿素(N24); 养分用量与小区试验相同。【结果】大田试验结果表明,T-all处理的玉米产量最高,比T-24提高了8.45%,达显著水平; T-all、 T-8、 T-16处理的夏玉米产量均高于T-side,分别比T-side提高了6.65%、 3.29%和5.43%,所有施肥处理中以T-24的玉米产量最低。玉米各生育期的氮素吸收量也以T-24处理最低; 与T-side处理相比,T-all处理的玉米氮吸收量在吐丝以前偏低,收获时稍高。夏玉米带状施肥主要影响垄内(施肥部位)土壤碱解氮含量,对垄间(非施肥带)土壤碱解氮含量影响不大; 与T-16、 T-24深层施氮相比,T-side、 T-8浅层施氮处理显著提高了玉米生育前期垄内表层土壤的碱解氮含量。示踪试验结果表明,施于8 cm、 16 cm、 24 cm的氮素利用率分别为37.24%、 31.33%、 18.75%。玉米收获后0100 cm土层N24处理的氮素残留量显著高于N8和N16处理,并且N24处理的氮素残留主要分布在4080 cm土层。【结论】本区域夏玉米底施尿素的适宜深度为816 cm。