NITROGEN NUTRIENT MECHANISM IN SECONDARY SUCCESSION PROCESS OF THE MIXED BROAD-LEAVED/ KOREAN PINE (PINUS KORAIENSIS) FOREST

Chemical and biochemical analysis methods were used to monitor the vedations of nitrogen nutrient among the dominance trees species in secondary succession process of the mixed broad - leaved/Korean pine forest on Changbai Mountains, Northeast China. Amounts of total nitrogen, anunonium and NRA in soils of virgin broad-leaved/Korean pine forest which is in climax were higher than those of secondary birch forests those are in succession Stage. The amount of nitrate was in the other hand. In climax, dominance trees species are tolerant mesophytic trees such as Pinus Koraiensis, Tilia amurensis, Acer mono and also Fraxinus mandshurica, they are all ammonium + nitrate adapted species, but they show a preference for the anunonium rather than those of the pioneer trees species in secondary birch forest, such as Populus davidiava and Betula platyphylla. Because they have more ammonium in their leaves and roots, especially Pinus koraiensis. Populus davidvana and Betula plaaphlla are intolerant trees, amounts of nitrate and total nitrogen is higher in their leaves and roots and also NRA in their leaves, so they preference for the nitrate rather than the others.In secondary birch forest, the regeneration trees species adapt their nitroggn nutrient to the variation of nitrogen nutrient situation in soil, finally they could survival well and the secondary birch forest would succession to climax. In climax, dominance trees species adapt their Nitrogen nutrient to the situation in soil and there are not strong competition in nitrogen nutrient among them, so they can coexist well and keep the climax as stable vegetation.

A study on the spatial difference of farmland nitrogen nutrient budget in the Bohai Rim region, China

The Bohai Rim region is one the most important bases for commodity grain production in China. With the rapid pace of agricultural industrialization, nitrogenous fertilizer has been used at an ever increasing rate, which resulted in the trace of accumulative nitrogen in the soil and caused serious environmental problems. In this study we made use of the farmland nitrogen balance model to assess the spatial difference of farmland nitrogen nutrient budget in the Bohai Rim region in 2008 with the assistance of GIS. Our results indicated that： 1） Farmland in this region has a nitrogen surplus totaling 5.0822 million tons, or an average of 288.54 kg/ha. 2） In the Bohai Rim region, farmland nitrogen input and farmland nitrogen budget both show a spatial differentiation. Major grain-producing areas have a higher nitrogen input than that of the grazing-farming areas. The main sources of nitrogen input include chemical fertilizer, organic fertilizer, deposition from atmospheric drying and wetting, and biological fixation, which account for 79.47%, 9.53%, 4.62%, and 3.58% of the total input, respectively. Therefore, chemical fertilizer is the predominant source of nitrogen input to farmland. 3） A total of 3.3398 million tons of nitrogen were output from the farmland via harvested crops and it accounts for 52.36% of the total nitrogen output from farmland in this region. On average, the amount of nitrogen output from unit farmland is equal to 176.65kg/ha. This study has shed light on farmland nitrogen budget and its spatial variation in the study area, may provide scientific evidences for rationalizing the use of chemical fertilizer and managing agricultural operation on the regional scale and is also valuable for improving the economic and ecological efficiency of fertilizer use at the regional scale.

Effects of Nitrogen Application Level on Rice Nutrient Uptake and Ammonia Volatilization

The effects of different nitrogen application levels on nutrient uptake and ammonia volatilization were studied with the rice cultivar Zheyou 12 as a material.The accumulative amounts of nitrogen,phosphorus and potassium in rice plants across all growth stages showed a trend to increase with increasing nitrogen application levels from 0 to 270 kg/hm 2,but decreased at nitrogen application levels exceeding 270 kg/hm 2.Moreover,the accumulative uptake of nitrogen,phosphorus and potassium by the rice plants was increased by application of organic manure in combination with 150 kg/hm 2 nitrogen.The nitrogen uptake was high during the jointing to heading stages.Correlation analysis showed that rice yield was positively correlated with the accumulative uptake of nitrogen,phosphorus and potassium by the rice plants.The highest correlation coefficient observed was between the amount of nitrogen uptake and rice yield.The rate and accumulative amounts of ammonia volatilization increased with increasing nitrogen fertilizer application level.Compared with other stages,the rate and accumulative amount of ammonia volatilization were higher after base fertilizer application.The ammonia volatilization rates in response to the nitrogen application levels of 270 kg/hm 2 and 330 kg/hm 2 were much higher than those in the other treatments.The loss of nitrogen through ammonia volatilization accounted for 23.9% of the total applied nitrogen at the nitrogen application level of 330 kg/hm 2.

Effects of temperature,algae biomass and ambient nutrient on the absorption of dissolved nitrogen and phosphate by Rhodophyte Gracilaria asiatica

Gracilaria asiatica,being highly efficient in nutrient absorption,is cultivated in sea cucumber ponds to remove nutrients such as nitrogen and phosphate.It was cultured in a laboratory simulating field conditions,and its nutrient absorption was measured to evaluate effects of environmental conditions.Ammonia nitrogen(AN),nitrate nitrogen(NN),total inorganic nitrogen(TIN),and soluble reactive phosphorus(SRP) uptake rate and removal efficiency were determined in a 4×2 factorial design experiment in water temperatures(T) at 15℃ and 25℃,algae biomass(AB) at 0.5 g/L and 1.0 g/L,total inorganic nitrogen(TIN) at 30 μmol/L and 60 μmol/L,and soluble reactive phosphorus(SRP) at 3 and 6 μmol/L.AB and ambient TIN or SRP levels significantly affected uptake rate and removal efficiency of AN,NN,TIN,and SRP(P<0.001).G.asiatica in AB of 0.5 g/L showed higher uptake rate and lower removal efficiency relative to that with AB of 1.0 g/L.Nitrogen and phosphorus uptake rate rose with increasing ambient nutrient concentrations;nutrient removal efficiency decreased at higher environmental nutrient concentrations.The algae preferred to absorb AN to NN.Uptake rates of AN,NN,and SRP were significantly affected by temperature(P<0.001);uptake rate was higher for the 25℃ group than for the 15℃ group at the initial experiment stage.Only the removal efficiency of AN and SRP showed a significant difference between the two temperature groups(P<0.01).The four factors had significant interactive effects on absorption of N and P,implying that G.asiatica has great bioremedial potential in sea cucumber culture ponds.

Evaluation of nutrient limitation in aquatic ecosystems with nitrogen fixing bacteria

There has always been a great need for simple and accurate bioassays for evaluating nutrient limitation in aquatic ecosystems. Whereas organic carbon is usually considered to be the limiting nutrient for microbial growth in many aquatic ecosystems, there are, however, many water sources that are limited by phosphorus or nitrogen. A method named ＂nitrogen fixing bacterial growth potential＂ （NFBGP） test, which is based on pre-culturing of autochthonous （target） microorganisms was described. The method was applied to evaluate phosphorus or nitrogen nutrient limitation in lake and sewage water samples using an isolate of the nitrogen fixing bacterium, Azorhizobium sp. WS6. The results corresponded well to those from the traditional algal growth potential （AGP） test and the bacterial regrowth potential （BRP） test, suggesting that the NFBGP test is a useful supplementary method for evaluating the limiting nutrient, especially phosphorus, in an aquatic environment.

Biomass,nutrient uptake and fatty acid composition of Chlamydomonas sp.ICE-L in response to different nitrogen sources

Nitrogen removal from media by microalgae provides the potential benefit of producing lipids for biodiesel and biomass. However, research is limited on algal growth and biomass under different nitrogen sources and provides little insight in terms of biofuel production. We studied the influences of nitrogen sources on cell growth and lipid accumulation of Chlamydomonas sp. ICE-L, one of a promising oil rich micro algal species. Chlamydomonas sp.ICE-L grown in NH_4 Cl medium had maximum growth rate. While the highest dry biomass of 0.28 g/L was obtained in media containing NH_4NO_3, the highest lipid content of 0.21 g/g was achieved under nitrogendeficiency condition with a dry biomass of 0.24 g/L. In terms of total polyunsaturated fatty acids（PUFAs）production, NH_4NO_3 and NH_4 Cl media performed better than nitrogen-deficiency and KNO_3 media.Furthermore, NH_4NO_3 and NH_4 Cl media elucidated better results on C18：3 and C20：5 productions while KNO_3and-N conditions were better in C16：0, C18：1 and C18：2, comparatively.

秸秆还田及不同比例控失尿素对华北平原小麦产量及潮土性质影响

为探讨不同控失尿素比例和秸秆还田对华北平原小麦产量及潮土化学性质的影响,本研究以华北潮土区小麦-玉米轮作体系为研究对象,采用裂区试验设计,以秸秆还田为主区,控失尿素比例为副区。秸秆还田模式设秸秆全量还田(S1)、秸秆不还田(S0)2种;控失尿素比例设不施肥(CK)以及控失尿素占总施氮量比例为0、40%、70%和100%(LCU0、LCU40、LCU70、LCU100)5个处理。在作物收割后进行产量测定,并采集0~20 cm耕层土壤进行常规土壤养分含量测定。结果表明:与S0处理相比,S1处理显著提高土壤有机质和速效钾含量。控失尿素显著提高土壤硝态氮含量,其他土壤养分含量无显著变化。秸秆不还田条件下,施用化肥显著降低了土壤pH值。控失尿素比例为70%时土壤养分含量最高。秸秆还田对小麦产量及吸氮量无显著影响,控失尿素对小麦产量及吸氮量增加具有极显著影响。在所有处理中,S1-LCU40处理的籽粒和秸秆产量最高,籽粒产量达7009.26 kg·hm^(-2),秸秆产量达11361.38 kg·hm^(-2)。秸秆还田对土壤氮素依存率具有显著影响,不同比例控失尿素对氮素收获指数具有显著影响,对氮肥表观利用率、土壤氮素依存率具有极显著影响。控失尿素比例为40%或70%时氮素吸收利用指标较优。综上,在华北平原潮土区,秸秆还田与40%控失尿素比例配施可以显著提升土壤供氮能力,提高小麦产量和氮素吸收与利用指标,是较为适宜的管理措施,但其机理及长期效应还需进一步研究。

海水多品种养殖池塘沉积物-水界面氮磷通量

为探明生源要素氮、磷在沉积物与水体间的迁移过程,比较3种不同养殖模式下、不同时间养殖池塘沉积物-水界面的氮、磷通量变化,2014年6—10月,在3种综合养殖池塘:海蜇+凡纳滨对虾+菲律宾蛤仔、海蜇+凡纳滨对虾+缢蛏和海蜇+凡纳滨对虾的整个养殖周期内,采集检测3口池塘沉积物-水界面样品中的亚硝态氮、硝态氮、氨氮和活性磷酸盐含量,分析沉积物-水界面的亚硝态氮+硝态氮、氨氮和活性磷酸盐的通量变化。试验结果显示,6—10月,3种综合养殖池塘沉积物上覆水中亚硝态氮和硝态氮均以向沉积物中扩散为主,仅10月海蜇+凡纳滨对虾池塘沉积物中亚硝态氮和硝态氮向上覆水释放。海蜇+凡纳滨对虾+菲律宾蛤仔、海蜇+凡纳滨对虾+缢蛏池塘沉积物上覆水中氨氮向沉积物扩散,6月海蜇+凡纳滨对虾+缢蛏池塘沉积物中氨氮向上覆水扩散;与海蜇+凡纳滨对虾+菲律宾蛤仔和海蜇+凡纳滨对虾+缢蛏池塘相比,海蜇+凡纳滨对虾池塘氨氮通量变化幅度较大,6—7月上覆水中氨氮向沉积物扩散,且扩散速率逐渐降低,9—10月沉积物中氨氮向上覆水释放,释放速率逐渐上升。6、7、10月海蜇+凡纳滨对虾+菲律宾蛤仔池塘沉积物中活性磷酸盐向上覆水释放,8—9月上覆水中活性磷酸盐向沉积物扩散;6—10月,海蜇+凡纳滨对虾+缢蛏池塘沉积物中活性磷酸盐向上覆水释放;海蜇+凡纳滨对虾池塘上覆水中活性磷酸盐向沉积物扩散,10月沉积物中活性磷酸盐向上覆水释放。试验结果表明,配养底栖贝类,可以通过改变综合养殖池塘沉积物-水界面的氮、磷通量,改善池塘的底质和水质环境。

氮沉降对城市森林凋落物养分元素含量及其耦合性的影响

目前,氮沉降增加呈现全球化趋势,影响森林生态系统生物地球化学循环过程,已成为生态和环境研究的热点内容之一。为探讨氮沉降增加对城市森林凋落物养分含量的影响,进一步认识城市森林养分循环过程,为区域城市化进程的生态风险评估提供科学依据,本研究以安徽省合肥市蜀山国家森林公园凋落物为研究对象,在连续3年模拟氮沉降实验后(氮添加设置3种水平,分别为对照组:0 kg·hm^(–2)·a^(–1)、CK;低氮:50 kg·hm^(–2)·a^(–1)、LN;高氮:100 kg·hm^(–2)·a^(–1)、HN),研究氮沉降对城市森林凋落物(枝叶果碎)养分元素含量及其耦合性的影响。结果表明:(1)不同施氮水平下,凋落果内CK与HN中C元素含量,凋落叶中CK与LN、碎中LN与HN两组中N元素含量差异显著(P<0.05)。(2)凋落物不同组分间,N沉降显著影响Ca元素含量(P<0.05),对C元素含量无显著影响;凋落枝组分间K含量差异显著(P<0.05),凋落叶与其他各组间N含量差异显著(P<0.05),凋落果与其他各组间P含量差异显著(P<0.05);凋落叶与凋落果间Mg元素差异显著。(3)N沉降对各组分间的C/N、C/P、N/P等生态化学计量比无显著性影响,但对凋落叶、凋落果中C/N值有显著抑制作用(P<0.05)。(4)N沉降显著影响C、N间相关性及Ca、Mg间相关性,且均表现为LN显著增强相关性,HN显著抑制相关性;N沉降显著增强了P、K间的相关性,而显著降低了K与Ca、Mg的相关性。(5)N沉降对C/N与N/P、C/P与N/P间的耦合性有显著影响,且均表现为LN显著增强生态化学计量比间的耦合性,HN显著降低二者耦合性。研究结果为城市森林凋落物养分循环过程对N沉降的响应提供了理论依据。

有机肥氮部分替代化肥氮对间作珠芽魔芋生长及养分积累利用的影响

为探索胶园间作珠芽魔芋的合理施氮方法,对有机肥氮部分替代化肥氮对珠芽魔芋生理特性、产量、品质及养分积累利用的影响进行了研究。研究设6个处理,分别为不施氮对照(T1)、当地习惯化肥氮用量(N 450kg/hm^(2))(T2)、80%习惯化肥氮用量+20%有机肥氮用量(T3)、80%习惯化肥氮用量(T4)、60%习惯化肥氮用量+20%有机肥氮用量(T5)、30%习惯化肥氮用量+50%有机肥氮用量(T6)。成熟期测定珠芽魔芋叶片形态指标、叶面球茎数量及倒伏株数、地下球茎产量、可溶性糖、淀粉、葡甘聚糖含量、氮磷钾含量及氮肥利用率。结果表明:与纯施化肥氮相比,有机肥代替部分化肥珠芽魔芋株高、茎粗、叶面球茎数量、繁殖系数增加,抗倒伏能力增强,提高了地下球茎氮肥利用率、产量、单株鲜重、膨大系数及氮、磷、钾吸收量。胶园间作珠芽魔芋的合理施氮模式为80%化肥氮+20%有机肥氮或者30%化肥氮+50%有机肥氮。

不同株型小花生品种氮素养分吸收利用特性

南方小花生植株高大的地方良种与矮化改良的品种并存。为探明其需氮规律,实现差异化施肥的高产管理,以湖南主栽的高秆地方良种安化小籽、矮秆现代品种湘黑小果为材料,设置4个基施复合肥用量0、450、600、750 kg/hm^(2),分别代表土壤背景(CK)、低肥(F30)、中肥(F40)、高肥(F50)水平,于4个生育时期测定并分析植株各器官氮含量、积累与分配状况。结果表明:氮含量以高秆品种果>叶>根>茎为序;矮秆品种则以叶>果>根>茎为序。叶、根氮含量表现为高秆<矮秆,而茎、果反之。增施肥料对氮含量的影响程度总体趋势为茎>叶>根>果,利于营养器官的氮素同化吸收。氮积累量两品种各器官以叶>果>茎>根为序。除苗期外,其余时期的全株、叶、茎氮积累量表现为高秆>矮秆;根在苗期、结荚期为高秆<矮秆,其余时期相反;果则为高秆<矮秆。施肥利于营养器官前期的氮素积累。氮素分配率两品种均以叶最高,荚果和茎其次,根最少。地上部为高秆>矮秆,而地下部反之,说明矮秆植株吸收的氮素更利于转运到荚果。氮素利用效率均为矮秆>高秆,氮素生产效率、氮肥偏生产力两品种均以F40、F30最高,过度施肥降低氮素利用效率。综上,矮秆品种氮素积累量对增肥的响应度较低,总积累量虽然较少而在荚果中分配较多,并具有更高的氮素利用效率;品种株型特点应作为南方典型贫瘠酸性红壤区小籽花生生产上确定施肥量的主要依据。

茭虾共作对土壤氮磷含量和茭白干物质积累及氮磷钾吸收分配的影响

为探究茭白种养模式的施肥策略,设置茭虾共作(ZC)、茭白单作(Z)2个处理,研究茭虾共作对土壤氮磷含量、茭白产量和茭白干物质积累及氮磷钾吸收分配的影响。2021-2022年的研究结果显示,茭虾共作模式较茭白单作模式采茭期土壤中全氮、全磷、速效磷的含量分别提高了10.85%~38.89%、5.45%~13.79%、6.19%~61.79%,净茭产量提高了5.10%~19.54%,采茭期茭白茎、叶、净茭的干物质积累量分别增加14.41%~16.58%、10.28%~15.15%、10.57%~21.45%。2021年茭虾共作处理较茭白单作处理在采茭期叶的氮含量显著增加了25.74%,但在孕茭期茎中磷含量显著减少了16.76%;2022年氮肥减量、减量投喂下,茭虾共作处理较茭白单作处理在孕茭期茎的氮含量显著减少了23.75%,在分蘖期叶中磷含量显著减少了12.08%,2a全生育期同一器官的钾含量在2个处理间差异不显著。对于养分积累,2021年茭虾共作处理在分蘖期叶的氮、磷、钾积累量较茭白单作处理分别减少26.04%、27.27%、30.11%,但在采茭期茎的氮、钾积累量和叶的氮、磷积累量较茭白单作处理分别增加18.80%、38.41%和44.77%、35.71%;2022年在氮肥减量、饲料减量投喂下,茭虾共作处理在采茭期叶的磷积累量和茎的钾积累量较茭白单作处理显著增加30.0%和30.77%。关于养分分配,2种处理的茭白在孕茭期和采茭期氮素的分配均以茎、叶为主,而磷、钾元素的分配均以茎为主,茎分配比例在42%~66%。对于养分转运,2021年2种处理茭白的根、茎、叶在氮、磷转运上大多为表现为“库”器官,而在钾转运上大多表现为“源”器官;2022年氮肥减量、减量投喂下,茭白的根、茎、叶在氮、磷、钾转运量上大多表现为“源”器官。因此,在茭虾共作模式中适当减少肥料、饲料的投入,能促进形成合理的源库关系,有利于茭白产量的形成。

施氮量对川东南冬水田稻鱼共作系统下杂交稻产量和土壤养分的影响

【目的】利用川东南冬水田区连续多年稻鱼共作系统,研究施氮(N)量对免耕栽培杂交稻产量形成和土壤养分的影响,为制定稻鱼共作系统下免耕栽培杂交稻长期、合理的氮肥管理策略提供理论依据。【方法】于2018—2022年在川东南冬水田区开展了5年大田定位试验,供试杂交稻品种为蓉优1015和内6优103,耕作方式为免耕。设置N 0、45、90、135 kg/hm^(2)4个施氮水平,分别记作N_(0)、N_(45)、N_(90)、N_(135)。在水稻收获期,调查杂交稻产量及产量构成因素,分析0—20 cm土层土壤全量和速效氮、磷、钾含量,以及有机质含量和pH,通过回归分析,研究施氮量与水稻产量和土壤养分因子含量变化之间的关系。【结果】稻鱼共作系统下,年份、施氮量对杂交稻产量及产量构成的影响达极显著水平。5年间,杂交稻产量与施氮量均呈极显著正相关(r=0.9070^(**)~0.9720^(**)),与低氮量处理N_(45)相比,N_(90)和N_(135)处理杂交稻产量分别增加了6.37%~26.53%、9.11%~25.11%,单位面积有效穗数和每穗粒数也显著增加。而N_(90)处理杂交稻产量与N_(135)处理相当或更高。逐步回归分析结果表明,杂交稻产量构成(单位面积有效穗数、每穗粒数、结实率和千粒重)与产量的偏相关系数达显著或极显著水平(t=2.20*~9.17^(**))。通径分析结果表明,杂交稻单位面积有效穗数和每穗粒数对产量的直接贡献(分别为0.8754和0.4987)和总贡献(分别为0.6364和0.3598)较大,表明单位面积有效穗数和每穗粒数是影响产量的主要因素。在N_(0)、N_(45)处理下,土壤全氮、碱解氮含量随稻鱼共作年限的增加而下降,而在N_(90)、N_(135)处理下随稻鱼共作年限的增加而增加。土壤全氮、碱解氮含量随施氮量增加而提高,而全磷、全钾、速效磷、速效钾含量则随施氮量增加而下降。杂交稻产量与土壤养分含量呈极显著正相关,可见提高磷素、钾素供给能力是稻鱼共作系统杂交稻高产的重要基础。【结论】川东南冬水田区稻鱼共作系统下,年施氮90 kg/hm^(2)可以提高杂交水稻的单位面积有效穗数和每穗粒数,进而维持甚至提高水稻产量。连续施用中、高量氮肥还可以提升土壤有机质、全氮、全磷、全钾、碱解氮、速效磷和速效钾含量,且随稻鱼共作年限延长呈增加趋势;土壤pH值则随稻鱼共作年限延长呈下降趋势。

不同氮营养盐对赫氏颗石藻和三角褐指藻中DMSP含量的影响

二甲基巯基丙酸内盐(dimethylsulfoniopropionate,DMSP)是地球上重要的有机硫化合物之一,在全球硫循环和气候调节等方面发挥着重要作用。浮游植物是海洋环境中DMSP的主要生产者,而氮营养盐是影响浮游植物产生DMSP的重要因素之一。本研究以赫氏颗石藻(Emiliania huxleyi)(DMSP高产量藻)与三角褐指藻(Phaeodactylum tricornutum)(DMSP中等产量藻)为对象,通过室内培养实验,对比分析了在不同氮营养盐浓度及不同氮营养盐类型条件下,2种藻培养液中颗粒态DMSP(DMSPp)的含量及其与藻密度、单细胞DMSPp含量的关系。研究发现,不同氮营养盐浓度或氮营养盐类型对赫氏颗石藻单细胞DMSPp含量影响较小(P>0.05),培养液中的DMSPp浓度主要受藻细胞密度影响;而不同氮营养盐浓度或氮营养盐类型对三角褐指藻单细胞的DMSPp含量影响显著(P<0.05),培养液中的DMSPp浓度主要受藻的单细胞DMSPp含量影响。例如,对于三角褐指藻来说,低NO_(3)^(-)浓度(0μmol/L)培养组单细胞DMSPp平均含量是高NO_(3)^(-)浓度(1764μmol/L)培养组的11倍;在不同氮营养盐类型下,NaNO_(3)培养组中总DMSPp的平均浓度分别为NH4Cl和CH4N2O培养组的3~4倍。推测以上差异可能与DMSP在不同藻类中的生理作用存在差异有关。

连作棉田土壤养分、棉花产量对减施氮肥的响应

【目的】研究多年连作棉田减氮量对棉花产量和土壤氮磷钾养分的影响,以及减氮与棉花产量、土壤氮磷钾养分有效性间的关联,为科学减施氮肥、维持新疆棉花的高产高效提供理论支撑。【方法】2020年和2021年在连作10年的棉田进行定位田间试验,供试棉花品种为新农大棉4号。设置常规施氮(375 kg/hm^(2),CK)、减氮20%(300 kg/hm^(2),N2)、减氮40%(225 kg/hm^(2),N4)和减氮100%(0 kg/hm^(2),N0)4个处理。调查了棉花产量,分析了0—20、20—40 cm土层土壤全量和速效氮、磷、钾含量。【结果】在北疆棉田300 kg/hm^(2)氮肥用量处理提高了土壤全磷、速效磷和速效钾含量,两年均值分别比CK处理高出4.04%、44.58%、9.94%(0—20 cm)和2.05%、44.47%、22.60%(20—40 cm);促进了棉花干物质积累,两年棉花平均干物质积累量较对照提高15.66%,利于产量形成,较对照处理分别增产了13.88%(籽棉)和18.10%(皮棉),有效提高了氮素利用效率。灰色关联分析可知,与减氮密切关联的土壤养分指标为土壤硝态氮、铵态氮含量,但与作物产量密切关联的土壤养分指标为土壤速效钾、全磷含量。【结论】在北疆长期连作棉田,将施氮量由375 kg/hm^(2)减至300 kg/hm^(2)可有效提升土壤有效态氮磷含量,进而增加棉花的干物质积累,提高籽棉和皮棉产量,实现节氮增产。

施肥模式对菜-稻轮作周年氮素吸收及产量的影响

为探明不同施肥模式对菜-稻轮作体系周年氮素吸收及其产量的影响,以长期定位试验中菜-菜-稻轮作和菜-菜-菜轮作各季作物为研究对象进行田间试验。2种轮作体系分别采用推荐施肥和习惯施肥2种施肥模式,于2020—2022年对各季作物氮含量和产量进行测定,研究不同施肥模式和轮作下各季作物周年氮素吸收积累量、氮肥偏生产力及其对产量效益的影响。结果表明,2个轮作周年内菜-菜-稻轮作方式下推荐施肥模式第二季作物(芥菜)和第三季作物(水稻)氮素年均吸收积累量为415.71 kg/hm^(2),显著高于习惯施肥模式(381.43kg/hm^(2))。第一和第二轮作周年,不同轮作施肥方式下四季豆作物的氮素收获指数为0.61~0.65,各处理之间无显著差异;推荐施肥处理水稻作物氮素收获指数分别为0.72和0.73,显著高于习惯施肥处理(0.62和0.62)。通过各季作物氮素吸收量与产量的相关分析表明推荐施肥处理能够提高作物氮素吸收利用率。菜-菜-稻轮作结合推荐施肥处理的年均产投比(1.79)高于习惯施肥处理(1.47),菜-菜-菜轮作结合推荐施肥处理的年均产投比(1.56)高于习惯施肥处理(1.36)。因此,推荐施肥处理作物的周年氮素吸收积累量和产量均高于习惯施肥,该施肥模式有利于菜-菜-稻轮作方式实现作物高产和氮肥高效利用,可获得较好的经济效益。

林火强度对兴安落叶松林土壤氮循环功能基因的影响

为了探究林火强度对土壤氮素循环的影响,本研究以内蒙古大兴安岭兴安落叶松林火烧迹地为研究对象,通过DNA提取及定量PCR分析测定了不同火烧强度样地内土壤氮循环功能基因丰度以及土壤基本的理化性质。结果表明:固氮nifH功能基因丰度随着火烧强度的增加而减少,而硝化amoA-AOA和amoA-AOB功能基因丰度呈相反变化趋势;反硝化nirS,nirK和nosZ功能基因丰度在重度火烧后显著降低,在轻度火烧后显著升高。火烧同样也会对土壤基本理化性质产生显著影响,RDA分析和Pearson相关性分析表明土壤氮循环功能基因与土壤理化因子之间存在密切的联系,有机碳、速效磷、全氮含量和pH值是影响火后土壤氮循环功能基因差异变化的主要因子。本研究为火干扰对土壤氮素循环的影响机制和火后植被快速更新提供数据支撑。

有机肥配施生物质炭对根际/非根际土壤氮赋存形态的影响

阐明化肥和有机肥配施生物质炭对根际/非根际土壤养分和氮赋存形态的影响,有助于农田氮的高效利用及科学管理。采用盆栽试验方法,设置不施肥(CK)、单施化肥(CF)、施有机肥(M)、化肥配施生物质炭(CFB)、有机肥配施生物质炭(MB)、新鲜有机肥配施生物质炭(FMB)6个处理,通过测定根际及非根际土壤养分含量和土壤氮赋存形态,阐明不同施肥处理对氮形态转化的影响。结果表明:与CK处理相比,MB处理提高非根际及根际土壤pH 0.32和0.28个单位,FMB处理提高根际土壤pH 0.63个单位;MB和FMB处理分别提高根际土壤有机质含量25.4%和84.9%,同时显著提高根际土壤全氮含量25.4%和50.9%,表现出明显的根际效应。施肥能显著提高土壤离子交换态氮(IEF-N)含量,以CF和CFB处理的效果最好。施用有机肥和生物质炭能显著提高土壤碳酸盐结合态氮(CF-N)含量,以M和MB处理效果最好,且CF-N存在根际富集效应。配施生物质炭(CFB、MB和FMB)处理能促进土壤非可转化态氮(NTF-N)向铁锰氧化物结合态氮(IMOF-N)和有机硫化物结合态氮(OSF-N)这两种活性更高的氮形态转化,其中IMOF-N和OSF-N分别占可转化态氮的35.9%~61.7%和26.7%~46.6%,是根际及非根际土壤可转化态氮(TF-N)的主要成分。因此,有机肥配施生物质炭是改善根际及非根际土壤养分和调控氮转化有效的方式。