共查询到20条相似文献，搜索用时 750 毫秒
1.
石灰性土壤供氮能力几种化学测定方法的评价研究 总被引：2，自引：0，他引：2
以采自于黄土高原差异较大的25个农田耕层石灰性土壤为供试土样,以淋洗和未淋洗土壤起始NO3--N小麦和玉米两季盆栽试验作物累积吸氮量为参比,对8种反映旱地土壤供氮能力的化学方法进行比较研究。结果表明,在一定程度上,可用有密切关系的土壤全氮或有机质,反映有机氮或全氮存在较大差异的土壤供氮能力,但其灵敏性较差。石灰性土壤矿质氮,特别是NO3--N与未淋洗土壤起始NO3--N作物吸氮量之间有较高相关性(r=0.884,P0.01),而与淋洗土壤起始NO3--N作物吸氮量间相关系数仅为0.472(P0.05),说明矿质氮可反映土壤当前供氮水平,而不能反映土壤潜在供氮能力;石灰性土壤起始NO3--N对各化学方法与作物吸氮量之间相关性影响较大。酸性高锰酸钾法既可反映土壤潜在供氮能力,也可反映土壤总供氮能力;酸性高锰酸钾法的修订方法,即硫酸高锰酸钾法提取出的NH4+-N值接近于KCl水浴法提取出的NH4+-N值,该方法在反映土壤总供氮能力方面与酸性高锰酸钾法相当,但在反映土壤潜在供氮能力方面不及酸性高锰酸钾法优越。KCl水浴法在评价石灰性土壤供氮能力方面,与酸性高锰酸钾法的效果基本相同;沸水浸取法和NaHCO3-UV法在评价石灰性土壤供氮能力方面效果较差。总结以上发现,在以盐类溶液提取法中,酸性高锰酸钾法、硫酸高锰酸钾法和KCl水浴法可作为反映石灰性土壤供氮能力的化学方法,其中以酸性高锰酸钾法最优,其次为KCl水浴法和硫酸高锰酸钾法。这3种方法在不包括起始NO3--N时,可反映石灰性土壤潜在供氮能力;包括起始NO3--N后,可反映土壤总供氮能力(当前供氮能力+潜在供氮能力)。 相似文献
2.
石灰性土壤起始NO3——N对土壤供氮能力测定方法的影响 总被引：11，自引：2，他引：11
在陕西省的澄城、永寿、杨陵 3地区选取有机质、全N、硝态N含量差异较大的 17个石灰性土壤 ,分别在淋洗与未淋洗土壤起始NO3--N后 ,利用盆栽试验探讨土壤NO3--N淋洗前、后 ,不同方法测定的已矿化N和可矿化N与小麦吸N量之间的相关性。结果表明 ,未淋洗土壤起始NO3--N ,用KCl直接浸取、KCl煮沸法所浸取以及通气培养前CaCl2 所淋洗的起始NO3--N均与小麦吸N量密切相关 ,相关系数 (r)分别为 0.934 ,0.856和 0.862 ,均达1%显著水准。与此相反 ,通气培养、淹水培养、沸水煮沸、碱性高锰酸钾、酸性高锰酸钾及碱解扩散等方法所提取的可矿化N与小麦吸N量间无显著相关。淋洗土壤起始NO3--N后 ,用KCl直接浸取、KCl煮沸法浸取以及通气培养前CaCl2 所淋洗的起始NO3--N与小麦吸N量之间的相关系数明显降低 ,达不到 5%的显著水准。而通气培养、淹水培养、沸水煮沸、碱性高锰酸钾、酸性高锰酸钾及碱解扩散等方法所提取的可矿化N与小麦吸N量之间相关系数却明显提高 ,都达到 5%或 1%的显著水平。其中变化最明显的是淹水培养 1周矿化出的NH4+-N、通气正式培养 2周矿化出的NO3--N及碱解扩散出的NH4+-N ,其与小麦地上部吸N量之间的相关系数 (r)分别由淋洗前的0.443,0.119,0.259增加到淋洗后的 0.866 ,0.767,0.763。说明可矿化N反映土壤供N能力不佳是因为受起始NO3--N的干扰和影响，在土壤NO3--N含量较高的情况下，要正确评价可矿化N测定方法必须考虑NO3--N的作用。 相似文献
3.
土壤矿质氮和可矿化氮对当季作物的贡献 总被引：2，自引：0，他引：2
从土壤矿质氮－硝态氮和铵态氮，土壤可矿化氮3个指标研究了土壤剖面不同层次有效氮对作物吸氮的贡献，结果表明，不同指标反映土壤供氮能力状况不一。土壤硝态氮和土壤可矿化氮与作物吸氮有较好的相关关系，而土壤铵态氮与作物氮关系不密切，在深度120cm之上的土层的土壤可矿化氮对作物吸氮有较大的贡献，在考虑土壤供氮能力时，建议应该考虑120cm深层以上的土壤。 相似文献
4.
秸秆与地膜覆盖条件下旱作玉米田土壤氮组分生长季动态 总被引：3，自引：2，他引：1
研究不同覆盖措施下农田土壤全氮及其活性和半活性组分在作物生长季的动态变化,有助于深入理解农田土壤氮循环过程。基于黄土高原8年春玉米覆盖定位试验,系统分析了土壤全氮、矿质氮、微生物量氮、潜在可矿化氮以及颗粒有机氮在玉米不同生育期的动态特征。试验包括全生育期9 000kg/hm2秸秆覆盖、全生育期地膜覆盖和不覆盖对照3个处理。结果表明:(1)除硝态氮和铵态氮在苗期上升外,秸秆和地膜覆盖下土壤全氮及其组分含量在春玉米生育期基本呈苗期下降、拔节期上升、大喇叭口—抽雄期下降、灌浆和收获期回升的变化趋势;(2)与对照相比,秸秆覆盖提高了大多数生育时期0—40cm土层全氮和硝态氮含量及0—20cm土层铵态氮含量,提高各生育时期0—40cm土层微生物量氮、潜在可矿化氮以及颗粒有机氮含量;(3)地膜覆盖较对照提高大多数生育时期0—40cm土层硝态氮和0—20cm土层铵态氮含量,降低作物生育后期0—20cm土层全氮和0—40cm土层颗粒有机氮含量,降低大多数时期0—40cm土层微生物量氮和10—20cm土层潜在可矿化氮含量;(4)除了地膜覆盖下20—40cm土层颗粒有机氮相对含量在作物不同生育期差异不显著外,秸秆和地膜覆盖下0—40cm土层微生物量氮、潜在可矿化氮、颗粒有机氮对土壤全氮的动态均有重要贡献。总之,黄土高原的春玉米田秸秆覆盖具有明显的提升土壤全氮及其组分含量的作用,有助于培肥地力和土壤固氮;地膜覆盖则降低了作物生育后期土壤全氮及其组分含量,同时显著提高了土壤硝态氮水平,导致农田土壤氮素淋溶风险提高。 相似文献
5.
氮肥与有机肥配施对设施土壤净矿化氮动态变化的影响 总被引：4，自引：0，他引：4
研究设施栽培条件下氮肥与有机肥配施对土壤净矿化氮含量及其速率的动态变化的影响,以评估净矿化氮在设施土壤供氮能力方面的作用,为设施番茄生产的合理施肥提供重要的理论依据。以设施番茄栽培连续7年定位施肥田间试验为依托,选择不同施氮量（N0、N1、N2、N3）和不同氮量配施有机肥（MN0、MN1、MN2、MN3）8个处理土壤,采用室内连续好氧培养方法,研究了各施肥处理土壤净矿化氮含量及净氮矿化速率,分析了土壤净矿化氮含量与可溶性有机氮、微生物量氮含量之间的联系。研究结果表明:在0 ~ 20 cm土层,氮肥与有机肥配施处理土壤全氮和无机氮含量均显著高于单施氮肥处理（P < 0.05）,施氮量对土壤全氮含量无显著影响,但对土壤无机氮含量则有显著影响,随施氮量的增加呈显著增加趋势。在培养过程中,各处理土壤净矿化氮含量随着培养时间延长呈先逐渐增加而后下降趋势,各处理土壤净氮矿化速率在培养7 d时最大,7 ~ 70 d期间快速下降,70 d后呈缓慢下降趋势,氮肥与有机肥配施处理土壤净矿化氮量和净氮矿化速率均显著高于单施氮肥处理（P < 0.05）,氮肥与有机肥配施处理土壤净矿化氮含量和净氮矿化速率随施氮量增加呈下降趋势;与单施氮肥相比,氮肥与有机肥配施显著提高土壤可溶性有机氮与微生物量氮含量（P < 0.05）,但受施氮量影响不显著;土壤净矿化氮含量与可溶性有机氮、微生物量氮之间有密切联系,但与可溶性有机氮之间的密切程度更大。综合来看,MN1、MN2处理可显著提高土壤供氮能力（无机氮 + 净矿化氮）。在设施番茄栽培条件下,连续7年氮肥与有机肥配施可显著提高设施土壤供氮能力,也可较好地协调设施土壤氮素供应与固持的关系。 相似文献
6.
采用盆栽试验和短期矿化培养相结合的方法,研究了施入15N标记氮肥(+N)及其与秸秆配施(+1/2N+1/2S)在3种长期(19年)不同培肥土壤(即:No-F,长期不施肥土壤;NPK,长期施用NPK化肥土壤;MNPK,长期有机无机肥配施土壤)中的残留及其矿化和作物吸收特性。结果表明,第一季小麦收获后,+1/2N+1/2S处理下三供试土壤和+N处理下的NPK和MNPK土壤残留肥料氮(残留15N)中有82.6%~95.1%以有机态存,而+N处理下No-F土壤残留15N有47.7%以矿质态存在。经过28 d矿化培养后,与NPK土壤相比,MNPK土壤氮素净矿化量显著增加,增幅为39%~49%;NPK和MNPK土壤残留肥料氮(残留15N)矿化量为1.23~1.90 mg kg-1,占总残留15N的2.78%~5.53%,均显著高于No-F土壤。与+N处理相比,+1/2N+1/2S处理显著提高了3供试土壤氮素净矿化量,但两施肥处理对NPK和MNPK土壤残留15N矿化量无显著影响。+N处理下No-F土壤残留15N的利用率为20%,显著高于NPK(9%)和MNPK(12%)土壤。两种施肥处理下,MNPK土壤残留15N的利用率均显著高于NPK土壤。短期培养期间土壤氮素矿化量和第二季小麦生育期作物吸氮量呈显著性正相关,而残留15N矿化量和第二季小麦吸收残留15N量间无显著性相关关系。长期有机无机配施可以提高土壤残留肥料氮的矿化量及有效性。 相似文献
7.
为评价栽培年限对新建日光温室土壤供氮能力的影响,采用盆栽生物耗竭试验和间歇淋洗好气培养法相结合的方法研究了陕西杨凌不同年限新建日光温室(温室建造前的大田及温室建造后第2年和第3年取样)耕层(0~20 cm)土壤供氮能力的变化。结果表明:随着温室栽培年限的增加,番茄生物量和吸氮量与温室栽培前相比均显著增加,其中栽培年限为第2年和第3年的番茄株高、茎粗、地上及根系生物量、叶片SPAD值均显著高于温室建造前,而第2年和第3年间各指标无显著差异;第2年和第3年温室的番茄吸氮量分别是建造前大田的2.53倍和3.01倍;与种植前土壤相比,第3年温室土壤有机质、全氮和速效养分含量均显著增加,第2年及第3年温室土壤可矿化氮量分别是建造前大田的2.84倍和2.96倍,说明随栽培年限的增加,温室土壤供氮能力显著增强。相关分析表明,土壤有机质、全氮、初始矿质氮及累积矿化氮量与番茄吸氮量间呈极显著正相关关系,其中以土壤累积矿化氮量与番茄吸氮量间的相关系数最大,说明这些指标均可用于评价土壤供氮能力。随栽培年限的增加,日光温室土壤供氮能力显著提高,生产中应随温室栽培年限增加适当降低氮肥用量。 相似文献
8.
黄土区不同类型土壤微生物量碳、氮和可溶性有机碳、氮的含量及其关系 总被引：20，自引：1，他引：20
研究了黄土高原南部地区不同土壤类型及不同利用方式下土壤微生物摄碳、氮和可溶性有机碳、氮的含量。结果表明：不同土地利用方式下，土壤微生物量碳、氮和可溶性有机碳、氮含量均为林地〉农田，其中林地枯枝落叶层〉林地O～20cm土层。农田土壤微生物量碳、氮的含量均为红油土〉黑垆土〉淋溶褐土；农田土壤中可溶性有机碳含量为淋溶褐土〉红油土〉黑垆土，而可溶性有机氮含量则为黑垆土〉红油土〉淋溶褐土。方差分析表明，不同土壤类型土壤微生物量氮含量之间的差异达显著水平，而不同土壤类型间土壤微生物量碳、可溶性有机碳、氯含量之间的差异未达显著水平。土壤微生物量碳、氮占土壤有机碳和全氮的比例明显高于可溶性有机碳、氮占土壤有机碳和全氮的比例。相关分析发现，土壤微生物量碳与可溶性有机碳之间以及土壤微生物量氮与可溶性有机氮之间的相关性达显著或极显著水平，说明土壤微生物量碳、氮和土壤可溶性有机碳、氮之间有密切联系。 相似文献
9.
旱地土壤矿质氮和可矿化氮与土壤供氮能力的关系 总被引：17，自引：3，他引：14
在具有典型半干旱气候特征的陕西永寿选取22个不同肥力水平的田块,分层采集0－100cm土样,研究矿质氮、可矿化氮和土壤供氮能力之间的关系。结果表明,NH4－M与可矿化氮之间没有明显关系;15－80cmNO3－N与各层可矿化氮显著相关,0－15cm和80－100cmNO3－N与之大多相关不显著。通径分析表明,30－45cm的可矿化氮和NO3－N对作物吸氮量的直接贡献最大（后者稍低于前者）;其次是60－80cm的NO3－No0-100cmNO3-N总的直接和间接贡献均大于可矿化氮。作为土壤供氮指标,0－45cm可矿化氮和0-100cmNO3-N都可靠,尤以后者效果更好。 相似文献
10.
秸秆和生物质炭添加对陇中黄土高原旱作农田土壤氮素矿化的影响 总被引：1，自引：1，他引：0
通过采集2014年设置于甘肃省定西市李家堡镇的不同碳源配施氮素田间定位试验土壤进行120天的室内培养试验,利用Stanford间歇淋洗培养法研究了无碳素和氮素添加(N0)、只施氮素(N100)、秸秆配施氮素(SN100)和生物质炭配施氮素(BN100) 4种施肥方式对陇中黄土高原旱作农田土壤氮素矿化的影响。结果表明:秸秆和生物质炭配施氮素提升了表层土壤氮素矿化量,分别比只施氮素显著提升16.5%和15.4%;土壤氮素矿化呈现先快速增加而后迅速下降,降速逐渐转为慢速直至稳定的趋势,硝化速率,氨化速率分别在7,15天时达到最大,45,30天时趋于稳定。秸秆和生物质炭配施氮素均可显著提升上层土壤氮素矿化速率,硝化速率和氨化速率则处于一种相对平衡的状态。土壤各有机氮组分在培养前后的变化量与土壤氮素矿化量之间的冗余分析结果表明,对土壤可矿化氮贡献最大的是氨基酸态氮,酸解未知氮次之;矿质态氮与未酸解氮呈负相关,与各酸解有机氮组分均呈正相关。此外,相比于不施氮,在施氮条件下添加秸秆和生物质炭增加了表层土壤各有机氮组分的变化量,说明添加秸秆和生物质炭可通过改变各有机氮组分占全氮的比例来增加易矿化氮的含量,从而促进有机氮组分的矿化,以提升土壤供氮潜力。 相似文献
11.
《Communications in Soil Science and Plant Analysis》2012,43(20):2371-2382
Application of nitrogen (N) fertilizers without knowing the N-supplying capacity of soils may lead to low N use efficiency, uneconomical crop production, and pollution of the environment. Based on the results from pot experiments treated with soil initial nitrate leaching and native soil, long-term alternate leaching aerobic incubation was conducted to study the disturbed and undisturbed soil N-supplying capacity of surface soil samples in 11 sites with different fertilities on the Loess Plateau. The results indicated that the entire indexes and ryegrass (Lolium perenne) uptake N with soil initial nitrate leaching showed a better correlation than that without soil initial nitrate leaching. Except the correlation coefficients for soil initial nitrate (NO3 ?)-N and mineral N extracted by calcium chloride (CaCl2) before aerobic incubation with ryegrass uptake without soil initial nitrate leaching, the correlation coefficients for soil initial NO3 ?-N and mineral N extracted by CaCl2 before aerobic incubation with ryegrass uptake with soil initial nitrate leaching and those for mineralizable N extracted by aerobic incubation, soil initial mineral N and mineralizable N extracted by aerobic incubation, potentially mineralizable N (N0) and soil initial mineral N + N0 with ryegrass uptake N under the two cases in disturbed treatment were all higher than those in undisturbed treatment. We concluded that NO3 ?-N in soil extracted by CaCl2 before aerobic incubation can reflect soil N-supplying capacity but cannot reflect soil potential N-supplying capacity. Without soil initial nitrate leaching, the effect of disturbed and undisturbed soil samples incubated under laboratory conditions for estimating soil N-supplying capacity was not good; however, with soil initial nitrate leaching, this method could give better results for soil N-supplying capacity. Based on the results from pot experiments treated with soil initial nitrate leaching and native soil, the mineralization of disturbed soil samples can give provide better results for predicting soil N-supplying capacity for in situ structure soil conditions on the Loess Plateau than undisturbed soil samples. 相似文献
12.
《Communications in Soil Science and Plant Analysis》2012,43(21-22):3399-3419
Interval leaching long‐term water‐logged incubation and interval leaching long‐term aerobic incubation were carried out to study the changes of different soil organic nitrogen (N) forms and their contributions to mineralized N during N‐mineralization process on 10 kinds of farmland soils with markedly different physical and chemical properties on the Loess Plateau. The results showed that the N‐mineralization capability and capacity using the two incubation methods were evidently different. After 217 days, cumulative mineralized N, the decreased amounts of total acid‐hydrolyzable N, acid‐hydrolyzable ammonia N, and acid‐hydrolyzable amino acid N in the water‐logged incubation were about twice those in the aerobic incubation. Soluble organic N leached in the aerobic incubation was four times that in the water‐logged incubation, which implied that organic N in the aerobic incubation mineralized more thoroughly than that in the water‐logged incubation. The correlation analysis of the changes of soil organic N forms with crop N uptake showed that the reduced amount of total acid‐hydrolyzable N in the water‐logged incubation was closely associated with total N uptake by two successive‐season crops (winter wheat and summer maize), and the decreased amounts of total acid‐hydrolyzable N and amino acid N in the aerobic incubation were highly significantly related to the N uptake of both the first season crop (winter wheat) and successive‐season maize. Multiple regression analysis, path analysis, and partial correlation analysis of the changes of soil organic N forms with mineralized N indicated that ammonia N was a main contribution to mineralized N in the water‐logged incubation, whereas both acid‐hydrolyzable amino acid and ammonia N were main contributions to mineralized N in the aerobic incubation. These results suggested that acid‐hydrolyzable ammonia was the primary contribution to mineralized N during N mineralization process with the two incubation methods. 相似文献
13.
冬小麦/夏玉米轮作中高肥力土壤的持续供氮能力 总被引：11，自引：4，他引：11
通过连续3年的冬小麦.夏玉米轮作试验研究高肥力土壤的供氮能力。结果表明,在本试验的高肥力土壤上,存在土壤供氮能力随时间延长而下降的趋势。但在连续3年3个轮作周期6季作物生长过程中,土壤都保持了较高的供氮能力,其中夏玉米季高于冬小麦季,不施氮处理在冬小麦季的相对产量保持在46%～76%,夏玉米季为69%～81%,轮作周期中土壤氮素的表观矿化量为125～184kg.hm2,而供氮能力为123～190kg.hm2。在考虑土壤供氮能力的基础上,基于土壤植株测试的氮肥优化管理,在连续6季作物中较大幅度地降低了氮肥用量,但却获得了同传统施氮处理一致的产量,保持了较低的土壤无机氮残留量,避免了过量施氮对环境的不良影响。 相似文献
14.
Crop rotations and tillage practices influence the quantity and quality of soil organic N (SON). We evaluated the impact of crop rotations and tillage practices on SON and mineralizable N at a depth of 0–15 cm in six field experiments, varying in duration over 8–25 years, that were being conducted in three Chernozemic soil zones in Saskatchewan, Canada. In a Brown Chernozem, continuous wheat increased SON at 0–15 cm by 7–17 kg N ha–1year–1 more than fallow/wheat. In a Dark Brown Chernozem, continuous cropping increased SON by 30 kg N ha–1year–1, compared with cropping systems containing fallow once every 3 years; and, in a Rego Black Chernozem, the increase in SON was 29 kg N ha–1 year–1, compared with cropping systems containing fallow once every 4 years. The increase in SON due to increased cropping frequency was accompanied by an increase in the proportion of mineralizable SON in the Brown Chernozem, but not in the Dark Brown and Black Chernozems. In the Brown Chernozemic soil zone, no-tillage management increased SON, compared with conventional tillage, varying from 16 kg N ha–1year–1 to 28 kg N ha–1year–1. In the Dark Brown Chernozemic soil zone, it increased SON by 35 kg N ha–1year–1 and, in the Black Chernozemic soil zone, by about 40 kg N ha–1year–1. Increases in SON at a depth of 0–7.5 cm due to no-tillage management was accompanied by a greater increase in the mineralizable N for Hatton fine sandy loam, Melfort silty clay and Indian Head clay than for other soils, indicating that the material responsible for the increased SON due to no-tillage was more labile than the soil humus N. However, the increased SON under no-till in Swinton loam, Sceptre clay and Elstow clay loam was not associated with an increase in the mineralizable N, indicating that this increased SON was no more susceptible to decomposition than the soil humus N. Therefore, increases in SON under improved management practices, such as conservation tillage and extended crop rotations, do not necessarily increase the potential soil N availability. 相似文献
15.
Predicting soil N mineralization: Relevance of organic matter fractions and soil properties 总被引：1，自引：0，他引：1
Gerard H. Ros Marjoleine C. Hanegraaf Willem H. van Riemsdijk 《Soil biology & biochemistry》2011,43(8):1714-1722
Distinct extractable organic matter (EOM) fractions have been used to assess the capacity of soils to supply nitrogen (N). However, substantial uncertainty exists on their role in the N cycle and their functional dependency on soil properties. We therefore examined the variation in mineralizable N and its relationship with EOM fractions, soil physical and chemical properties across 98 agricultural soils with contrasting inherent properties and management histories. Mineralizable N was determined by aerobic incubation at 20 °C and optimum moisture content for 20 weeks. We used multivariate statistical modelling to account for multi-collinearity, an issue generally overlooked in studies evaluating the predictive value of EOM fractions. Mineralization of N was primarily related to the size of OM pools and fractions present; they explained 78% of the variation in mineralizable N whereas other soil variables could explain maximally 8%. Both total and extractable OM expressed the same soil characteristic from a mineralization perspective; they were positively related to mineralizable N and explained a similar percentage of the variation in mineralizable N. Inclusion of mineralizable N in fertilizer recommendation systems should be based on at least one OM variable. The most appropriate EOM fraction can only be identified when the underlying mechanisms are known; regression techniques are not suitable for this purpose. Combination of single EOM fractions is not likely to improve the prediction of mineralizable N due to high multi-collinearity. Inclusion of texture-related soil variables or variables reflecting soil organic matter quality may be neglected due to their limited power to improve the prediction of mineralizable N. 相似文献
16.
R. Otto R. L. Mulvaney S. A. Khan P. C. O. Trivelin 《Biology and Fertility of Soils》2013,49(7):893-904
Intensive use of synthetic nitrogen (N) fertilizers for sugarcane (Saccharum spp.) production presents environmental challenges for water and air quality as well as impacts profitability for producers. Central to these concerns is a widespread reliance on yield-based recommendations that invoke generic models of crop N response but lack any means to account for variations in soil N-supplying power, a critical determinant of fertilizer N need for cereal, fiber, and tuber crops. The work reported herein was designed to ascertain the impact of soil N mineralization on sugarcane response to N fertilization and was carried out in conjunction with eight N-response trials conducted between 2006 and 2010 at field sites in the largest sugarcane-cultivated area in Brazil. Soil samples were utilized in categorizing the sites as highly responsive, moderately responsive, or nonresponsive to fertilizer N, based on two chemical indices of soil N availability, the Illinois Soil Nitrogen Test (ISNT) and direct steam distillation (DSD), and assessments of (1) net mineralization during aerobic incubation for 12 weeks and (2) incubation-induced changes in soil N fractions obtained by acid (total hydrolyzable N, hydrolyzable NH4 +-N, amino sugar N, and amino acid N) or alkaline (ISNT-N) hydrolysis. Sugarcane varied widely in response to N fertilization, indicating that yield-based recommendations would often under- or overestimate N requirement and thus adversely impact sustainability of sugarcane-based ethanol production. In studies to evaluate feasibility of soil N testing to improve fertilizer N recommendations, mineral N production upon aerobic incubation was accompanied by significant decreases in hydrolyzable NH4 +-N and ISNT-N, indicating that both fractions were liberating mineralizable forms of soil N. Test values by the ISNT and DSD were highly correlated, and both showed promise for differentiating soil responsiveness to fertilizer N. 相似文献
17.
《Communications in Soil Science and Plant Analysis》2012,43(6):451-462
Abstract Many methods of evaluating organic soil nitrogen (N) mineralization and N availability indexes have been proposed. Chemical methods are more rapid but they do not measure the soil microorganisms and plant root activities. Incubation‐leaching procedure may remove some of the readily mineralizable soil organic N compounds. Continuous‐incubation procedure may sometimes increase soil acidity or cause toxins accumulation. The objective of this study was to determine, in a greenhouse experiment, the relative capabilities of 10 soils with organic matter (O.M.) content ranging from 2.38 to 8.63% to supply plant‐available N by combining two procedures, i.e., soil incubation and plant N‐uptake. In method one (M1), N‐uptake by 3 successive oat crops of 8 weeks each, without soil preincubation was studied. Method two (M2) involved a soil preincubation of 8 weeks, and the subsequent determination of N‐uptake by two successive crops of oats (Avena sativa L.) of 8 weeks each. No soil‐leaching was used. The results show that there was a large difference in plant N‐uptake according to soil organic matter. The highest correlation between soil O.M. and plant N‐uptake (r = 0.91**) was given by the first crop following incubation. The N‐uptake by the first crop in M1 (without soil incubation) was much less correlated with soil O.M. (r = 0.74*) and was significantly influenced by soil initial NO3 and NH4‐N. The results of this study show that the preincubation of soil samples minimized the influence of soil initial mineral N and that a preincubation was necessary before the plant N‐uptake measurement, even on a 8‐week cropped soil period. 相似文献
18.
Very few studies have been related to soluble organic nitrogen (SON) in forest soils. However, this nitrogen pool could be a sensitive indicator to evaluate the soil nitrogen status. The current study was conducted in temperate forests of Thuringia, Germany, where soils had SON (extracted in 0.5 M K2SO4) varying from 0.3 to 2.2% of total N, which was about one-third of the soil microbial biomass N by CFE. SON in study soils were positively correlated to microbial biomass N and soil total N. Multiple regression analysis also showed that mineral N negatively affected SON pool. The dynamics of the SON was significantly affected by mineralization and immobilization. During the 2 months of aerobic incubation, the SON were significantly correlated with net N mineralization and microbial biomass N. SON extracted by two different salt solution (i.e. 1 M KCl and 0.5 M K2SO4) were highly correlated. In mineral soil, SON concentrations extracted by 1 M KCl and 0.5 M K2SO4 solutions were similar. In contrast, in organic soil layer the amount of KCl-extractable SON was about 1.2-1.4 times higher than the K2SO4-extractable SON. Further studies such as the differences of organic N form and pool size between SON and dissolved organic N (DON) are recommended. 相似文献
19.
《Communications in Soil Science and Plant Analysis》2012,43(19-20):3139-3157
Nitrogen (N) in the soil is largely organic and is available to crops only after it is mineralized to inorganic N by microbial or enzyme action. To develop a soil test for guiding N applications, a method to predict the relative amount of organic N that will mineralize in a growing season is necessary. Several chemical analysis methods proposed in the literature to measure mineralizable N were examined for chemical interference, measurement precision, response to procedure modifications, and ability to distinguish differences among soils. The chemical analyses examined involved various acid or alkaline hydrolysis, with the resulting inorganic ammonium N measured by steam distillation and manual or automated diffusion. A gelatinous precipitate in the filtered and neutralized 6 M hydrochloric acid (HCl) hydrolysis solution interfered with magnesium oxide (MgO) diffusion traditionally used to measure inorganic ammonium N. Removing the precipitate appeared to circumvent the interference. The precipitate did not appear to interfere with the sodium hydroxide (NaOH) diffusion. The 6 M HCl hydrolysis extracted 34 to 103% of clay‐fixed ammonium in the soils. Steam distillation was shown to be an acceptable alternative to diffusion for measuring NaOH‐labile N. The vigor of NaOH measurement conditions caused differences in results, showing that precise and reproducible conditions are necessary. Several methods were closely correlated (r2 > 0.62) with N mineralized during aerobic incubations and could be considered for further evaluation for soil N testing. This study showed that modifications are required to several proposed analytical methods to improve their potential to estimate mineralizable N for fetilizer or other amendment recommendations for crop production 相似文献
20.
The mineralization and availability of cover crop N to the succeeding crop are critical components in the management of soil N to reduce N leaching. The effects of several leguminous and non-leguminous cover crops on soil N availability, N mineralization potential, and corn (Zea mays L.) yield were examined. The cover crops had variable effects on soil N availability and corn yield and N uptake. Because of the rapid mineralization of the cover crops following incorporation, the inorganic N levels in the soil sampled in mid-May 1992 (4 weeks after incorporation of cover crops), rather than the potentially mineralizable N, rate constants, initial potential mineralization rate, or cumulative N mineralized over 14 weeks, correlated well with N concentrations, C:N ratios, or the N added in the cover crops. However, the inclusion of potentially mineralizable N with inorganic N in a multiple regression improved the variability in the corn yield and the N uptake accounted for. Since extensive mineralization had occurred before the 21 May sampling, the potentially mineralizable N was affected more by the soil organic N and C than by the N concentrations of the cover crops. The presidedress NO3
--N test levels were well predicted by the inorganic and potentially mineralizable N (R
2=0.89, P<0.01), although the test levels were better in predicting corn yield and N uptake. If the available soil N test needs to be made earlier than recommended by the presidedress NO3
--N test, both inorganic and potentially mineralizable N are needed to better predict the corn yield and N uptake in the soils. 相似文献