不同栽培模式及施氮对玉米-小麦轮作体系土壤肥力及硝态氮累积的影响

以在陕西关中土垫旱耕人为土区进行的连续6年定位试验为对象,研究了长期覆盖栽培及施氮量对玉米?小麦轮作体系下土壤有机质、全氮及土壤剖面硝态氮残留量和分布的影响。结果表明,不同栽培模式对土壤有机质和全氮含量的影响为覆草垄沟常规节水,其中覆草模式影响达显著水平。增施氮肥不同程度地提高了土壤有机质和全氮含量。经过12季玉米-小麦的轮作,不同栽培模式0～200cm土壤剖面硝态氮残留量为垄沟节水覆草常规,垄沟和节水栽培模式与常规栽培硝态氮累积量差异达显著水平。随种植年限和施氮量增加,0～200cm土壤中硝态氮累积量明显增加,施240kg·hm-2N(N240)处理0～200cm土壤硝态氮累积量显著高于施120kg·hm-2N(N120)处理。不同施氮量下硝态氮在0～200cm土壤剖面的分布存在差异,与不施氮(N0)和N120处理相比,N240处理下各栽培模式在120cm以下的土壤硝态氮含量随深度增加而显著增加。     

不同栽培模式对小麦—玉米轮作体系土壤硝态氮残留的影响

在陕西关中地区研究了有限灌溉与旱地蓄水保墒栽培相结合的不同栽培模式和施氮量对冬小麦夏玉米轮作体系中硝态氮残留的影响。结果表明,种植五季作物后不同栽培模式0200.cm土壤剖面残留硝态氮平均在2183～29.kg/hm2之间,且残留的硝态氮主要集中在100200.cm土层。不同栽培模式相比,垄沟模式0200.cm土层的硝态氮残留量最高。随着种植年限和施氮量的增加,0200.cm土层硝态氮残留量随之显著增加。施用240kg/hm2氮肥,第五季作物收获后0200.cm土层硝态氮的残留量达477.kg/hm2;从第三季作物收获到第五季作物收获,残留硝态氮的增加量占这一时期氮肥施用量的比例高达51.6%。种植作物五季后,常规、节水和覆草模式在080.cm土层硝态氮残留量相对较低,而80.cm以下土层硝态氮残留量随着施氮量的增加明显增加。垄沟栽培模式在0200.cm土壤剖面残留硝态氮的量随施氮量增加显著增加,且在0120.cm土层硝态氮残留量明显高于其它模式。     

施肥与灌水对硝态氮在土壤中残留的影响

通过田间试验研究不同施氮量与灌水量对春玉米和冬小麦田土壤中硝态氮分布与累积的影响,结果表明,春玉米收获后0~2 m土壤中累积硝态氮185.7~748.0 kg/hm2,其中1 m以上占57.9%~70.1%。由于施用氮肥而增加的硝态氮占施N量的1.8%(N 112.5 kg/hm2),50.7%(N 225 kg/hm2),56.7%(N 337.5 kg/hm2)和77.0%(N450 kg/hm2)。不施N和施N 112.5 kg/hm2时春玉米田土壤剖面没有明显累积峰;施N等于或高于225 kg/hm2时在60~80 cm土层有明显累积峰,施氮量高的峰值较高;施N 450 kg/hm2时在120~140 cm深度出现另一个累积高峰。冬小麦收获后土壤0~2 m硝态氮累积量为74.9~328.8 kg/hm2,其中1m以上占67.8%~90.7%。由于施用氮肥而增加的硝态氮占施N量的19.5%(N 112.5 kg/hm2),35.6%(N 225 kg/hm2),58.9%(N 337.5 kg/hm2)和56.4%(N 450 kg/hm2)。冬小麦田收获后土壤深层(1~2 m)没有明显的硝态氮累积,即使施氮量高达450 kg/hm2时也只在表层40 cm以上累积较多。不论是春玉米还是冬小麦,当生育期施氮量大于225 kg/hm2时0~2 m土层均有明显的硝态氮累积,施氮量高的累积量较高。施氮量是造成土壤中硝酸盐累积的主要因素,灌水量对春玉米田硝态氮的向下迁移有显著影响。     

不同施氮情况下小麦玉米间作土壤硝态氮的动态变化

本文主要研究了0、210、420和630kg/hm2（NO、N1、N2和N3）4种不同施氮量对小麦玉米间作土壤硝态氮(NO-3-N)含量动态变化的影响。结果表明,0～200cm土层硝态氮的含量整体表现为N3>N2>N1>N0。各生育时期低氮水平下0～60cm土层,中、高氮水平下的0～80cm土层土壤硝态氮含量变化显著。0～60cm土层土壤硝态氮累积量随作物生育时期的变化呈“双峰”曲线,峰值分别出现在小麦挑旗期和玉米大喇叭口期,而60～200cm土层土壤硝态氮累积量的变化呈“单峰”曲线,峰值出现在玉米大喇叭口期。N0处理硝态氮累积量各生育时期变化差异较小。小麦与玉米共生期内0～200cm土层硝态氮含量表现为玉米带>小麦带,差异最大的时期为小麦灌浆期和玉米大喇叭口期。土壤硝态氮向深层的运移量随施氮量增加而增加,与N0相比,施氮后100～200cm土层硝态氮累积量小麦带增加了1053～6253kg/hm2,玉米带增加了1791～7039kg/hm2。优化氮肥施用比例,适当降低小麦播前施氮量可减小土壤硝态氮深层淋溶的风险。     

旱作地区长期小麦连作和苜蓿连作土壤剖面的矿质氮研究

对不同施肥条件下23年小麦连作地和苜蓿连作地土壤矿质氮分布和累积进行研究,探讨种植浅根系和深根系植物对硝态氮淋溶的影响。结果表明,不施肥(CK)和单施磷(P)肥,小麦和苜蓿连作地土壤硝态氮主要集中在0—60 cm土层,0—60 cm土层以下硝态氮含量变化稳定并小于2 mg/kg。氮肥、磷肥和有机肥配施(NPM)时,小麦连作地土壤硝态氮累积在20—100 cm和140—320 cm土层,年累积速率可达42.12 kg/(hm2.a);苜蓿连作土壤硝态氮主要集中在0—60 cm土层,仅在200—300 cm土层出现轻微累积,年累积速率仅为1.01 kg/(hm2.a)。在不施肥和单施磷肥下,种植小麦或苜蓿对土壤硝态氮残留量影响不显著,而氮、磷和有机肥配施时,小麦连作地土壤硝态氮残留量迅速增加,并与不施肥、单施磷肥处理有显著差异;苜蓿连作地土壤硝态氮残留量虽有少量增加,但与不施肥、单施磷肥处理无显著差异。不施肥、单施磷肥和氮、磷和有机肥配施,小麦连作、苜蓿连作地土壤剖面铵态氮含量主要在10—20 mg/kg之间波动,在土壤剖面无明显的累积现象,铵态氮残留量受施肥和作物种类的影响不显著。     

施氮量、土壤和植株氮浓度与小麦赤霉病的关系

【目的】赤霉病已成为影响小麦产量和品质的重要病害之一,为了解施用氮肥对小麦赤霉病的影响,本文通过研究不同施氮水平下小麦赤霉病的发病情况,探索施氮、土壤供氮、植株氮浓度与小麦赤霉病的关系。【方法】采用田间小区试验,以多穗型豫麦49-198(YM49-198)和大穗型周麦16(ZM16)为供试品种,设N 0、120、180、240、360 kg/hm25个施氮水平(N0、N120、N180、N240、N360),根据"小麦赤霉病测报技术规范"调查小麦赤霉病的发病情况。【结果】土壤硝态氮含量及0—90 cm土层土壤硝态氮累积量均随施氮量的增加而增加,小麦收获期N0、N120、N180处理0—30 cm土层硝态氮含量及0—90 cm累积量差异不显著,但显著低于N240和N360处理。两个品种小麦赤霉病病穗率和病情指数(DI)随施氮量的增加而增加,各处理间差异显著;豫麦49-198施氮处理的病穗率和DI比不施氮处理分别增加29.5%~132.0%和35.9%~225.2%,周麦16施氮处理的病穗率和DI比不施氮处理分别增加42.4%~161.8%和41.7%~206.9%;两个品种小麦N180处理赤霉病的病穗率和病情指数与N0、N120差异较小,显著低于N240和N360;周麦16较豫麦49-198发病严重,各处理的病穗率和病情指数比豫麦49-198分别高出7%~25%和28.0%~63.6%。小麦赤霉病病穗率和DI与硝态氮含量显著正相关,与0—90 cm硝态氮累积量呈线性正相关。孕穗期、开花期和灌浆期茎基部硝酸盐含量和拔节期~开花期植株的全氮含量各处理间差异较大,且与小麦赤霉病病穗率和DI显著线性正相关。【结论】土壤硝态氮含量及累积量随施氮量增加而增加,小麦收获后施氮量低于N 180 kg/hm2时土壤中硝态氮残留较低,赤霉病发病较轻。小麦赤霉病病穗率和病情指数随施氮量的增加而增加,说明施氮量过高会加重小麦赤霉病病害;小麦拔节期~开花期的氮浓度过高会加重赤霉病病害,因此在这一时期,适宜的施氮量、土壤硝态氮和植株氮浓度在赤霉病发生年份可以减轻病害,综合考虑土壤硝态氮残留、产量和赤霉病害等因素的适宜施氮量为N 180 kg/hm2。     

过量施氮对旱地土壤碳、氮及供氮能力的影响

【目的】过量施氮会影响土壤有机碳、氮的组成与数量,进而改变土壤供氮能力,但关于西北旱地长期过量施用氮肥后土壤有机碳、氮及土壤供氮能力变化的研究尚缺乏。本文在长期定位试验的基础上,通过分析不同氮肥水平特别是过量施氮条件下土壤硝态氮,有机碳、氮和微生物量碳、氮的变化,探讨长期过量施氮对土壤有机碳、氮及供氮能力的影响。【方法】长期定位试验位于陕西杨凌西北农林科技大学农作一站。在施磷(P2O5)100kg/hm2的基础上,设5个氮水平,施氮量分别为N 0、80、160、240、320 kg/hm2。重复4次,小区面积40 m2,完全随机区组排列。种植冬小麦品种为小堰22。本文选取其中3处理,以不施氮为对照(N0)、施氮量N 160 kg/hm2为正常施氮(N160),施氮量N 320 kg/hm2为过量施氮(N320),分别于2012年6月小麦收获后和10月下季小麦播前采集土壤样品,进行测定分析。【结果】过量施氮导致下季小麦播前0—300 cm各土层硝态氮含量显著增加,平均由对照的2.8 mg/kg增加到15.5 mg/kg;同时,0—60 cm和0—300 cm土层的硝态氮累积量分别由对照的47.2和108.9 kg/hm2增加到76.5和727.7 kg/hm2。过量施氮也增加了夏闲期间0—300 cm土层土壤有机氮矿化量,由对照的72.4 kg/hm2增加到130.7 kg/hm2。但过量施氮未显著增加土壤的有机碳含量,却显著增加了土壤有机氮含量,过量施氮0—20、20—40 cm土层土壤有机碳分别为9.24和5.39 g/kg,有机氮分别为1.05和0.71 g/kg,较对照增加52.2%和54.3%。同样,过量施氮未显著影响0—20、20—40 cm土层土壤微生物量碳含量,其平均含量分别为253和205 mg/kg,却显著提高了0—20、20—40 cm土层土壤微生物量氮含量,由对照的24.1和7.5 mg/kg提高到43.6和16.1 mg/kg。【结论】过量施氮可以显著增加旱地土壤剖面中的硝态氮累积量、夏闲期氮素矿化量、小麦播前土壤氮素供应量和土壤微生物量氮含量,但对土壤有机碳和微生物量碳没有显著性影响,同时过量施氮增加了土壤硝态氮淋溶风险,故在有机质含量低的黄土高原南部旱地冬小麦种植中不宜施用高量氮肥,以减少土壤氮素残留和农业投入,达到保护环境和培肥土壤的目的。     

玉米追氮对玉米∥大豆间作体系产量和土壤硝态氮的影响及其后茬效应

【目的】明确玉米条带不同追施氮量对间作作物产量、 吸氮量和土壤硝态氮动态变化的影响,并阐明间作系统不同施氮量的后茬农学效应和环境效应。【方法】玉米和大豆播种时均施用相同的基肥(其中氮肥用量为N 45 kg/hm2),根据大喇叭口期玉米条带追施氮量的不同(N 0、 75、 180 kg/hm2)设置三个处理(N0、 N75、 N180),并且大豆生育期间均不追施氮肥,然后实时监测玉米和大豆各个关键生育期的生物量和土壤硝态氮动态变化,并对比分析各处理的后茬冬小麦产量和土壤硝态氮残留量。【结果】随着玉米条带追施氮量的增加,玉米条带生物量、 产量和吸氮量均无显著变化,而且玉米追施氮量的多少对大豆生物量、 产量和吸氮量没有明显影响。间作种植系统土壤硝态氮含量受到追施氮量的影响,氮肥追施后,020 cm土壤硝态氮含量显著上升,但2040 cm土壤硝态氮含量变化不大。追施氮量越多,玉米条带和大豆条带的土壤硝态氮含量也越高,作物收获后土壤硝态氮残留量也越高,玉米条带追施N 180 kg/hm2的间作系统作物收获后土壤硝态氮含量高出其他两个处理12%~25%。此外,后茬作物冬小麦产量、 吸氮量并未随着前茬间作系统施氮量的增加而增加,但小麦收获后的0100 cm土壤硝态氮残留却随着前茬间作系统施氮量的增加而增大,相对仅施用基肥而不追施氮肥的间作系统,前茬间作系统追施氮肥导致后茬小麦收获后土壤(0100 cm)硝态氮残留量增加了22.38%~70.18%。【结论】针对玉米与大豆间作种植模式,只施用玉米基肥(其中氮肥用量为N 45 kg/hm2)而不追肥,或者在施用基肥的基础上,仅在玉米条带上追施少量氮肥(N 75 kg/hm2),不会影响间作体系产量,还可降低后茬小麦0100 cm土壤中的硝态氮残留。     

养分专家系统推荐施肥对甜瓜产量品质和土壤氮素淋失的影响

  【目的】  养分专家系统 (Nutrient Expert，NE) 是利用作物多年产量水平和施肥历史进行推荐施肥的轻简化施肥技术。本研究从甜瓜产量品质和土壤养分的淋洗、平衡角度，对该方法在甜瓜上应用的可行性进行验证。  【方法】  以甜瓜品种‘楼兰17号’为试材，于2017—2018年在甘肃省瓜州县向阳村进行了推荐施肥田间试验。在养分专家系统推荐施氮量 N 300 kg/hm2 (NE, N300) 的基础上，设置NE ± 25%N (N225和N375)、NE ± 50%N (N150和N450) 4个施氮量处理，以不施氮肥为对照 (N0)。在成熟期，测定甜瓜产量、品质、地上部干物质积累量、果实氮素吸收量、氮肥利用率、0—200 cm土层硝态氮累积量，分析土壤氮素平衡状况。  【结果】  2017和2018年甜瓜产量均以NE系统推荐的N300处理最高，较N0处理两年平均增产24.7%，施氮量0～300 kg/hm2范围内，甜瓜产量随施氮水平的增加而增加，超过NE推荐施氮量 (300 kg/hm2)时产量下降；在NE推荐的施氮量 (300 kg/hm2)时甜瓜品质最优，商品率、经济效益最高，施氮量不足或过量都不利于甜瓜品质的形成；氮肥利用率、氮肥养分内在效率随施氮量的增加而降低，但N225和N300处理差异不显著，果实吸氮量在N300处理时最高，N300处理氮素收获指数明显高于其他施氮处理；0—200 cm土层硝态氮累积量随着施氮量的增加而增加，2017年硝态氮主要残留在0—100 cm土层，占0—200 cm土层硝态氮积累量的43.9%～55.3%，2018年硝态氮主要残留在100—200 cm土层，占0—200 cm土层硝态氮积累量的44.8%～69.9%；0—100 cm土层氮素表观损失量随施氮量的增加而增加，甜瓜植株地上部吸氮量两年平均占氮素输出量的33.2%、氮素残留量占氮素输出量的33.1%、氮素表观损失量占氮素输出量的42.1%；甜瓜产量、地上部吸氮量及氮素残留量和施氮量的多曲线分析拟合得出，甜瓜最高吸氮量的施氮量为323 kg/hm2，最高产量的施氮量为293 kg/hm2。施氮量每增加30 kg/hm2，产量增加886.5 kg/hm2，增幅为2.1%；土壤硝态氮增加8.5 kg/hm2，增幅为37.6%。  【结论】  不论是产量和品质，还是氮素收获指数，NE系统推荐的施氮300 kg/hm2处理都取得了最优的效果。当超过推荐施氮量时，主要增加茎叶干物质量，但会降低果实的产量和品质。在供试生态条件下，土壤中硝态氮累积量随施氮量的增加而增加，且向下淋洗明显，试验的第一年主要积累在0—100 cm土层，第二年则下移至100—200 cm土层，环境风险增加。当氮素施用量超过300 kg/hm2时，氮素表观损失量 > 氮素残留量 > 植株地上部吸氮量。因此，在生态脆弱区，限制氮肥过量投入不仅是产量和品质的需要，也是实现环境可持续的要求。     

华北平原不同农田类型土壤硝态氮累积及其对地下水的影响

针对华北平原典型农田的传统灌溉施肥带来的肥料浪费和环境污染问题,采集定州保护地蔬菜、小麦-玉米轮作农田土样及相应的地下水样品,研究了不同农田利用类型、保护地蔬菜不同种植年限和不同种植类型的土壤硝态氮的累积及对地下水污染的程度。结果表明,土壤剖面0-400cm范围保护地蔬菜的硝态氮累积量明显高于农田,0-100cm,100-200cm,200-300cm,300-400cm平均为815.0,293.6,394.9,313.4kg/hm2,分别为农田的12.3,3.8,4.6,5.1倍。保护地土壤剖面硝态氮累积量随着棚龄的增加而增加,尤其在0-60cm表现明显,0-100cm和100-200cm老龄棚(12a)土壤硝态氮累积量分别为815.0,293.6kg/hm2,高于低龄棚(8a)216.2,11.4kg/hm2。大棚黄瓜的土壤剖面硝态氮累积大于番茄,在根区外深层剖面出现多个明显的累积峰。保护地灌溉水、小麦-玉米轮作农田灌溉水及手压井饮用水NO3-N含量分别为9.6,7.4,10.5mg/L,超标率(10mg/L)分别为38%,16%,46%,该区域浅层饮用地下水已受到硝酸盐污染。     

农田秸秆覆盖条件下冬小麦增产的水氮条件

通过田间试验建立了冬小麦产量与灌水量及施氮量的关系模型,并作了模拟分析,以期研究旱地农田秸秆覆盖条件下冬小麦增产的水氮条件.结果表明:秸秆覆盖的冬小麦能否增产与水肥供应关系密切.生育期间没有补充灌水时,覆盖增产主要取决于氮肥用量,氮肥投入较少时覆盖冬小麦经济产量能取得显著的增产效果;氮肥用量较高时产量低于未覆盖处理.因此,在雨养农业区,通过配合适量的氮肥完全能够做到秸秆覆盖下增产增收.在不同氮肥用量前提下,覆盖的增产效果除了与生育期总灌水量有关外,还与灌水量在各生育期间的分配有关.因此,在有灌溉条件的地区,根据氮肥投入情况,将有限的水分配在作物最需要的时期才能取得秸秆覆盖下的节水高产.     

Influence of mulch C/N ratio and decomposition stage on plant N uptake and N availability in soil with or without wheat straw

Mulches can improve soil properties, but little is known about nutrient availability in mulched soil that contains plant residues and the effect of mulching with manures. The aim of this study was to determine the effects of mulching with high or low C/N organic materials, in which low C/N materials differed in decomposability, and the presence of wheat straw in the soil on plant growth and N uptake, soil N availability and microbial biomass N within about four months after mulching. Three organic materials were used: mature wheat straw (W, C/N 80), young faba bean shoots (FB, C/N 7), and sheep manure (SM, C/N 8). There were eight treatments differing in amendment methods (mulching or mixing with W or both) and mulching materials (W, FB or SM). Treatments that were only mulched with W, FB or SM are referred to as m‐treatments. In m/s‐treatments, after W was mixed into the soil, W, FB or SM were placed on the soil surface as mulch. Two other treatments included an unamended control and soil mixed with W. Wheat was planted 0, 35 or 70 days after mulching (referred to as 0, 35, and 70 DAM) and grown for 35 days. Faba bean mulch increased shoot dry weight, shoot N uptake and available N compared to wheat or sheep manure mulch, particularly in the m‐treatments. Shoot dry weight was higher in m‐treatments than corresponding m/s‐treatments with the same mulch type. Shoot N uptake was higher in 70 DAM than in 0 DAM in all treatments and 0.3 to three‐fold higher in m‐treatments than the corresponding m/s‐treatments. Microbial biomass N was higher in 0 DAM than in 35 and 70 DAM in most treatments and up to two‐fold higher in m/s‐treatments than the corresponding m‐treatments. Available N in m/s‐treatments was two to six‐fold higher than m‐treatments in 0 DAM, but differed little in older mulch ages of W and SM. It can be concluded that compared to soil with only mulch, mixing of wheat straw into soil reduced plant growth and N uptake, particularly in the early stages of mulching (0 and 35 DAM). However, the presence of wheat in mulched soil may provide a longer lasting source of N for plants and reduce the risk of N leaching from rapidly decomposing low C/N mulch due to greater microbial biomass N uptake than only soil with mulch.     

Influence of Residue Management and Tillage Systems on Carbon Sequestration and Nitrogen,Phosphorus, and Potassium Dynamics of Soil and Plant and Wheat Production in Semi-arid Region

Reducing the tillage and application of mulch are important strategies for soil and water conservation and sustainability of agricultural systems. Soil can be a source or sink for carbon (C) depending on management strategies and plays a major role in the global C cycle. These interacting practices can alter nutrient movement and availability to the crops, reduce water loss, slow down organic-matter (OM) decomposition, and thus enhance C sequestration. A 2-year field study was conducted to quantify the tillage and mulching effect on soil organic C (SOC), OM, nitrogen (N), phosphorus (P), and potassium (K) at two depths (i.e., 0–15 and 15–30 cm deep) in the soil profile and N, P, and K concentrations (g kg^?1) in plant shoots at harvest on a Typic Calciargids in wheat–maize rotation. The four tillage systems used were zero tillage (ZT), minimum tillage (MT), conventional tillage (CT), and deep tillage (DT), and four mulch rates [control, 2 (M₂), 4 (M₄), and 6 (M₆) Mg ha^?1 year^?1 wheat (Triticum aestivum L.) straw] were applied in combination with each tillage system, keeping recommended rates of fertilizers. There was a linear positive response of mulch application on SOC for both years, but it was more pronounced during the second year. Greater values were found in ZT and the lowest in CT at all depths, although greater SOC content was found in upper layers than in deeper ones. Greater shoot N, P, and K concentrations were found in MT, CT, and DT, whereas the lowest concentration was found in ZT. Mulch application has no effect on N, P, and K concentrations in shoots. The soil N concentration was not affected by tillage and mulch, yet greater soil N content was found at 0–15 cm than 15–30 cm deep. There was significant effect of tillage on soil P and K during one year as greater P and K concentrations were found under MT, CT, and DT compared to ZT. More N, P, K, and OM concentrations were found at 0–15 cm deep than at 15–30 cm deep during the whole study period. Mulch effect was significant on K, and significantly greater amounts were found at greater levels of mulch application. The increases in the soil OM were 34.5, 35.75, and 24% at 0–8, 8–16, and 16–24 cm deep respectively from the first year to the second year. Tillage effect on soil organic-matter content was not significant. Tillage increased grain production for both years. For the first year, 22.9 and 27% greater yields were found in CT and DT, whereas in the second year yields were 10.6, 17.9, and 57% greater, respectively, in MT, CT, and DT as compared to ZT. Grain production was increased at a result of mulch application by 12.9, 20.3, and 10.6% during the first year and 11.45, 23.74, and 10.9% during the second year as compared to control (i.e., without mulch). Results show the importance of mulch application and crop residue retention. Both can increase the SOC content and water-holding capacity, which will result in improved production and soil physical health over long and continuous use of mulch.     

Optimization of nitrogen fertilizer rate under integrated rice management in a hilly area of Southwest China

China has the world''s highest nitrogen (N) application rate, and the lowest N use efficiency (NUE). With the crop yield increasing, serious N pollution is also caused. An in-situ field experiment (2011-2015) was conducted to examine the effects of three N levels, 0 (i.e., no fertilizer N addition to soil), 120, and 180 kg N ha^-1, using integrated rice management (IRM). We investigated rice yield, aboveground N uptake, and soil surface N budget in a hilly region of Southwest China. Compared to traditional rice management (TRM), IRM integrated raised beds, plastic mulch, furrow irrigation, and triangular transplanting, which significantly improved rice grain yield, straw biomass, aboveground N uptake, and NUE. Integrated rice management significantly improved ¹⁵N recovery efficiency (by 10%) and significantly reduced the ratio of potential ¹⁵N loss (by 8%-12%). Among all treatments, the 120 kg N ha^-1 level under IRM achieved the highest ¹⁵N recovery efficiency (32%) and ¹⁵N residual efficiency (29%), with the lowest ¹⁵N loss ratio (39%). After rice harvest, the residual N fertilizer did not achieve a full replenishment of soil N consumption, as the replenishing effect was insufficient (ranging from -31 to -49 kg N ha^-1). Furthermore, soil surface N budget showed a surplus (69-146 kg N ha^-1) under all treatments, and the N surplus was lower under IRM than TRM. These results indicate IRM as a reliable and stable method for high rice yield and high NUE, while exerting a minor risk of N loss. In the hilly area of Southwest China, the optimized N fertilizer application rate under IRM was found to be 100-150 kg N ha^-1.     

低温半干旱区不同覆盖物对地温和水分时空分布的影响

建立了不同覆盖物下春小麦生长期间土壤的地温、水分时空分布图。研究表明:保水、集水、增温、降水生产率效果排序:双重覆盖(秸秆+地膜)>地膜>秸秆>裸地。干旱年降水生产率分别较裸地提高83%、70.5%、37.7%。降水生产率较丰年分别提高53.39%、1.2%、12.8%,双重覆盖仍多蓄水31mm,半干旱区春小麦生长主要依赖土壤贮蓄水,双重覆盖和地膜覆盖使180 cm土层内水以汽态水凝聚在耕层,达到秋水春用。秸杆覆盖早春不但降低耕层地温,而且截留残留降水和部分有效降水不能入土而蒸发,降低土壤贮水量。应在秋季施碎秸秆后翻耕,接纳雨水,春播前膜侧种植,可起双重覆盖蓄水、保水、增产作用。覆膜对膜外横向30 cm处10 cm土层在全生育期都有增温作用。     

免耕覆盖还田下玉米秸秆氮素的去向研究

采用田间微区试验,以15N标记的玉米秸秆为研究对象,研究了免耕覆盖还田下玉米秸秆氮素经过4个生长季后的作物累积利用率、在土壤(0~60 cm)的残留率以及损失情况。试验共设2个处理:TS1为第1年15N标记秸秆覆盖还田,此后秸秆不还田;TS2为第1年15N标记秸秆覆盖还田,此后每年以非标记秸秆还田。结果表明:经过4个生长季后,两个处理间的玉米籽粒、秸秆的累积产量及总氮素吸收量的差异均不显著。在TS1处理中,秸秆氮素在籽粒和秸秆中的累积回收率分别为14.2%和6.7%,并分别高于TS2处理的12.4%和5.8%。与作物的累积回收率相比,更多的秸秆氮素被保持在土壤中。在TS1和TS2处理中,秸秆氮素在土壤中的残留率分别为40.9%和73.8%,而损失率分别为38.6%和8.1%。与TS1处理相比,TS2处理中较高的土壤微生物生物量碳和氮以及较低的矿质态秸秆氮的含量,说明连续秸秆还田在一定程度上提高了最初还田秸秆氮素在土壤中的微生物固持并降低了秸秆氮素的淋失风险,从而显著提高秸秆氮素在土壤-植物系统中的总回收率。因此,在温带农田生态系统中,长期的免耕结合秸秆覆盖还田可促进秸秆氮素的积累,这对提高和保持土壤氮素含量和稳定性具有重要的意义。     

用径流小区法研究不同耕作措施对土壤侵蚀的影响

用径流小区方法,研究了不同耕作措施对土壤侵蚀的影响。结果表明:B处理(沿等高线 薄膜覆盖 秸秆覆盖 开沟种植)能有效地减少土壤侵蚀,维护土壤耕作层,可促进农业的可持续发展。处理B、A、C总的径流量分别比处理D(CK)减少79.13%、69.76%、50.61%,总的侵蚀量减少的比例分别为86.81%、72.75%、50.90%。     

Orchard floor management effects on nitrogen fertility and soil biological activity in a newly established organic apple orchard

This study addresses the often-competing goals of organic fertility and weed control by evaluating alternative orchard floor management strategies for their impact on N cycling, tree performance, and soil biological activity in a newly established apple (Malus domestica Borkh.) orchard. The standard tillage weed control practice resulted in satisfactory tree growth with desirable levels of leaf N and most other nutrients; however, soil biological activity did not improve. Maintenance of a living cover understory increased soil N concentration and availability and improved soil biological activity; however, tree growth was less than in other treatments likely in response to competition with the living cover understory for space and water. Application of wood chip mulch resulted in exceptional tree growth which may have resulted from greater water availability, but available soil N was lower, and consequently, tree leaf N concentration was low; in addition, soil biological activity was not improved. Clove oil organic herbicide provided poor weed control resulting in lower leaf N and tree growth and did not improve soil biological activity. Brassicaceae seed meal applications enhanced N availability and soil nematode abundance, but leaf N and many other nutrients were below desirable levels, and additional research is needed to optimize this treatment. We conclude that meeting the multiple objectives of weed control, optimal tree health, and increased soil biological activity may require employment of different orchard floor management strategies at different times during the life of the orchard.     

中国北方典型地区农用地膜污染现状调查及其防治对策

通过对我国北方典型地区的调查，初步探索了该地区土壤农膜残留量和残膜特征。研究表明，河北省典型地区温室大棚、蔬菜田和作物田的农膜土壤残留量平均分别为5.629、7.369和2.822 kg·hm^-2，黑龙江省典型地区温室大棚、蔬菜田和作物田残留量平均分别为4.169、3.682和2.430 kg·hm^-2，各采样点之间存在着较大差异，但普遍较高，均明显高于未使用农膜的对照土壤。两地区之间除作物田的土壤农膜残留量没有明显差异外，河北地区其他两类土壤中的农膜残留量水平明显高于黑龙江地区，这种差异与各地区在农事活动及农膜使用上的差异具有一定的相关性。上述两地区土壤中残留农膜尺寸基本一致，主要集中在10～15 cm之间。该文针对我国目前农膜使用情况及其污染现状，提出了相应的防治对策。     

秸秆深层覆盖对土壤水盐运移及小麦生长的影响

通过对秸秆不同覆盖方式的土柱模拟实验研究表明,秸秆深层覆盖在土壤中形成了一个毛细管障碍层,破坏了土壤毛细管的连续性,明显降低深层土壤水分蒸发,减少了深层土壤盐分向表层的运移;秸秆表层覆盖使土表与空气的接触面变小,利于土壤保水。深层秸秆结合表层秸秆覆盖对土壤的保水效果最好,而且抑制盐分的土壤表聚,减轻土壤盐分对作物生长的胁迫,降低土壤耕层的返盐,保证了作物正常生长。