生物炭添加对酸化土壤中小白菜氮素利用的影响

针对菜地土壤酸化趋势显著、氮肥利用率低下等突出问题,以小白菜为供试作物,设置了前3季连续施用化肥氮及后2季不施化肥氮的5季盆栽试验,研究生物炭添加对酸化土壤上连续多季种植小白菜的产量、氮肥利用率以及土壤供氮能力的影响。结果表明:在连续添加化肥氮的条件下,生物炭添加显著增加了小白菜的产量及氮素累积量,有效降低了土壤速效氮含量,并提高了土壤速效氮中NO3--N含量比例,缓解了土壤酸化趋势,降低了小白菜中硝酸盐含量,增加了氨基酸含量,提高了氮肥利用率;在停止施用化肥后,生物炭添加处理仍能保持较高的土壤速效氮含量,提高土壤固持氮素的有效性,促进植株对氮素的吸收利用,从而使产量维持在施氮条件下的高水平。研究表明生物炭添加对土壤氮素具有"削峰填谷"的调节功能,能够有效促进氮素的吸收转化,从而有利于维持高产。     

不同秸秆还田方式对红壤性质及花生生长的影响

通过田间小区试验研究化肥配合不同秸秆还田方式对红壤养分、生物学特性和作物生长的影响。结果表明,与其他(NPK、NPKD1、NPKD2)处理相比,氮磷钾化肥配合秸秆直接还田(NPKJG)处理土壤碱解氮降低了7.88%~31.37%,速效磷降低了7.72%~23.81%。各处理土壤脲酶活性在花生的生长期间先降低后升高,而转化酶活性先升高后降低(除NPK处理的转化酶活性持续降低外)。氮磷钾化肥配合Fe SO4促腐秸秆堆肥还田处理(NPKD2)提高了土壤脲酶活性26.14%,而配合碱渣促腐秸秆堆肥处理(NPKD1)提高了土壤转化酶活性66.13%。氮磷钾化肥配合Fe SO4促腐秸秆堆肥处理土壤微生物生物量碳含量较高,且提高了花生各农艺性状指标和产量。     

生物质灰对红壤酸度的改良效果

用采自安徽、浙江、湖南和广东的4种红壤和1种赤红壤,通过室内培养实验研究了添加生物质灰对酸性土壤的改良效果。结果表明,添加生物质灰提高了土壤p H,降低了土壤交换性铝含量,且阳离子交换量(CEC)越小改良效果越明显。改良后土壤交换性K+、Ca2+、Mg2+含量也显著增加,交换性Ca2+增幅最大,其次为交换性K+。有效磷含量也有增加,磷含量较高的土壤有效磷增幅更大。虽然生物质灰含有一定量的重金属,但由于用量较少,对土壤有效态重金属含量的影响小,施用生物质灰的环境风险较小。总之,添加生物质灰不仅可以有效改良红壤酸度,还可提高红壤肥力。     

高寒山区地形序列土壤有机碳和无机碳垂直分布特征及其影响因素

地形、生物气候条件具有明显差异的青藏高原约占我国陆地面积的五分之一,开展该地区土壤有机碳和无机碳分布特征的研究对于理解青藏高原土壤碳循环过程与陆地碳库的精确预测以及应对全球气候变化具有重要意义。研究选取位于祁连山中段的阴、阳坡地形序列土壤,分析了不同坡向间以及同一坡向内随海拔高度变化土壤有机碳和无机碳的垂直分布特征及其影响因素。结果表明:阴、阳坡有机碳含量均随土壤深度增加而下降,但阳坡下降的速率(66%~91%)明显高于阴坡(31%~77%);阴坡土壤中碳酸钙基本淋失,通体无机碳含量较低(5.0 g kg-1),阳坡B层土壤无机碳含量是A层的2倍,表现为明显富集。阴坡和阳坡1 m土体总碳密度相当(分别为16.1~33.9 kg m-2和11.8~32.8 kg m-2),其中,阴坡以有机碳为主(占总碳密度的82%~99%),而阳坡有机碳和无机碳密度变化均较大(分别占总碳密度的27%~81%和19%~73%)。因此,坡向是影响高寒山区土壤碳垂直分布和组成的重要因素。此外,降雨量和植被类型对地形序列土壤有机碳和无机碳含量的空间变异也具有重要影响:降雨量每增加1 mm,表层(0~20 cm)土壤有机碳含量增加0.4 g kg-1,而淀积层(40~80 cm)土壤无机碳含量下降0.2 g kg-1;植被类型在一定程度上影响了土壤有机碳的富集程度。本研究揭示了青藏高寒山区土壤碳循环及其碳库预测应充分考虑微地形对坡面尺度下土壤碳垂直分布、碳库组成和空间变异的影响。     

氮肥对水稻不同生长期土壤不同深度氮素渗漏的影响

为了探明太湖地区氮肥施用对水稻不同生长期稻田土壤氮素渗漏的影响,利用渗漏管进行了原位监测。结果表明：①土壤各层(20 ~ 40、40 ~ 60、60 ~ 80和80 ~ 120 cm)渗漏液中铵态氮(NH4+-N)的平均浓度在水稻分蘖期较高,而硝态氮(-N)和全氮(TN-N)的平均浓度则在苗期相对较高。渗漏液中NH4+-N和TN-N浓度随土壤深度增加基本呈降低趋势。②以土壤80 ~ 120 cm深处渗漏量为进入地下水的氮素渗漏量,发现TN-N渗漏量占施肥量的比例为1.69% ~ 2.04%。分蘖期的NH4+-N渗漏量相对较多,而苗期-N和TN-N相对较多,总TN-N渗漏量中NH4+-N和-N基本无差异。③氮肥用量增加降了氮肥利用效率,加剧了土壤各层氮素渗漏风险。当施氮量由N 200增至270 kg/hm2时,氮肥表观利用率下降7.14%,下渗至地下水中的TN-N增加12.3%。     

回顾参加工作60年¾¾纪念中国科学院南京土壤研究所建所60周年有感

中国科学院南京土壤研究所是我国土壤科学研究的中心,也是培育土壤科学高层次人才的基地。值此纪念中国科学院南京土壤研究所成立60周年之际,笔者回顾了自己在土壤研究所不同发展阶段的科学研究、科研业绩、学术交流、人才培养、研究所管理等工作情况,系统地总结了自己为我国土壤科学事业发展及国家与国际社会经济建设所作过的贡献。同时,从工作经历中,提出了自己60年科研生涯最深的四条人生感悟,以激励大家能在今后的工作和学习中树立理想、创新信念,立足当前、放眼未来,为创建现代土壤科学和土壤所创新发展,为实现中华民族的伟大复兴梦想而努力奋斗。     

土壤溶液性质对水溶性镍的西红柿毒害的影响

选取17种具有代表性的中国土壤,研究土壤溶液性质对土壤孔隙水以及0.01 mol/L CaCl2浸提液中镍(Ni)植物毒害的影响。结果发现,孔隙水中Ni(PW-Ni)对西红柿地上部分生物量50% 抑制的毒性阈值(EC50)变化范围为1.02 ~ 8.91 mg/L,最大值是最小值的 8.7倍;CaCl2-Ni的毒性阈值EC50变化范围为 0.77 ~ 20.40 mg/kg,最大值是最小值的26.5倍,表明土壤溶液性质对水溶性Ni的毒性阈值影响很大。土壤PW-Ni毒性主要受到K+、Mg2+、S的影响,基于这3个因子的回归方程可以较好预测PW-Ni对西红柿毒性阈值EC50,决定系数为0.71。当回归方程包括土壤溶液中溶解性有机碳(DOC)、pH、电导率(EC)、Ca2+、Na+ 时,其决定系数提高到0.84,说明其他因子对PW-Ni的毒性也存在一定的影响,利用这些土壤溶液性质可以较好预测PW-Ni的植物毒性阈值。     

玉米/蒜苗套作系统中土壤微生物和土壤酶状况分析

对玉米蒜苗套作根区进行隔膜、隔网和无隔处理以及各自单作处理,通过处理间的相互比较,分析影响套作产量的主要土壤因素。结果表明:套作蒜苗土壤微生物上升其主要原因是根系间的非接触物质交换;套作玉米除此外,地上部环境的改变也使根部土壤微生物数量上升。根系间的非接触效应还使蒜苗、玉米土壤过氧化氢酶、蔗糖酶活性提高,而环境因素的改变也使玉米过氧化氢酶,蒜苗脲酶活性提高。相关性分析表明:微生物对蒜苗根际土壤酶活性的影响大于对玉米土壤酶的影响。     

Long-term impact of reduced tillage and residue management on soil carbon stabilization: Implications for conservation agriculture on contrasting soils

Residue retention and reduced tillage are both conservation agricultural management options that may enhance soil organic carbon (SOC) stabilization in tropical soils. Therefore, we evaluated the effects of long-term tillage and residue management on SOC dynamics in a Chromic Luvisol (red clay soil) and Areni-Gleyic Luvisol (sandy soil) in Zimbabwe. At the time of sampling the soils had been under conventional tillage (CT), mulch ripping (MR), clean ripping (CR) and tied ridging (TR) for 9 years. Soil was fully dispersed and separated into 212–2000 μm (coarse sand), 53–212 μm (fine sand), 20–53 μm (coarse silt), 5–20 μm (fine silt) and 0–5 μm (clay) size fractions. The whole soil and size fractions were analyzed for C content. Conventional tillage treatments had the least amount of SOC, with 14.9 mg C g⁻¹ soil and 4.2 mg C g⁻¹ soil for the red clay and sandy soils, respectively. The highest SOC content was 6.8 mg C g⁻¹ soil in the sandy soil under MR, whereas for the red clay soil, TR had the highest SOC content of 20.4 mg C g⁻¹ soil. Organic C in the size fractions increased with decreasing size of the fractions. In both soils, the smallest response to management was observed in the clay size fractions, confirming that this size fraction is the most stable. The coarse sand-size fraction was most responsive to management in the sandy soil where MR had 42% more organic C than CR, suggesting that SOC contents of this fraction are predominantly controlled by amounts of C input. In contrast, the fine sand fraction was the most responsive fraction in the red clay soil with a 66% greater C content in the TR than CT. This result suggests that tillage disturbance is the dominant factor reducing C stabilization in a clayey soil, probably by reducing C stabilization within microaggregates. In conclusion, developing viable conservation agriculture practices to optimize SOC contents and long-term agroecosystem sustainability should prioritize the maintenance of C inputs (e.g. residue retention) to coarse textured soils, but should focus on the reduction of SOC decomposition (e.g. through reduced tillage) in fine textured soils.     

Cover crop effect on soil carbon fractions under conservation tillage cotton

Cover crops may influence soil carbon (C) sequestration and microbial biomass and activities by providing additional residue C to soil. We examined the influence of legume [crimson clover (Trifolium incarnatum L.)], nonlegume [rye (Secale cereale L.)], blend [a mixture of legumes containing balansa clover (Trifolium michelianum Savi), hairy vetch (Vicia villosa Roth), and crimson clover], and rye + blend mixture cover crops on soil C fractions at the 0–150 mm depth from 2001 to 2003. Active fractions of soil C included potential C mineralization (PCM) and microbial biomass C (MBC) and slow fraction as soil organic C (SOC). Experiments were conducted in Dothan sandy loam (fine-loamy, kaolinitic, thermic, Plinthic Kandiudults) under dryland cotton (Gossypium hirsutum L.) in central Georgia and in Tifton loamy sand (fine-loamy, siliceous, thermic, Plinthic Kandiudults) under irrigated cotton in southern Georgia, USA. Both dryland and irrigated cotton were planted in strip tillage system where planting rows were tilled, thereby leaving the areas between rows untilled. Total aboveground cover crop and cotton C in dryland and irrigated conditions were 0.72–2.90 Mg C ha⁻¹ greater in rye + blend than in other cover crops in 2001 but was 1.15–2.24 Mg C ha⁻¹ greater in rye than in blend and rye + blend in 2002. In dryland cotton, PCM at 50–150 mm was greater in June 2001 and 2002 than in January 2003 but MBC at 0–150 mm was greater in January 2003 than in June 2001. In irrigated cotton, SOC at 0–150 mm was greater with rye + blend than with crimson clover and at 0–50 mm was greater in March than in December 2002. The PCM at 0–50 and 0–150 mm was greater with blend and crimson clover than with rye in April 2001 and was greater with crimson clover than with rye and rye + blend in March 2002. The MBC at 0–50 mm was greater with rye than with blend and crimson clover in April 2001 and was greater with rye, blend, and rye + blend than with crimson clover in March 2002. As a result, PCM decreased by 21–24 g CO₂–C ha⁻¹ d⁻¹ but MBC increased by 90–224 g CO₂–C ha⁻¹ d⁻¹ from June 2001 to January 2003 in dryland cotton. In irrigated cotton, SOC decreased by 0.1–1.1 kg C ha⁻¹ d⁻¹, and PCM decreased by 10 g CO₂–C ha⁻¹ d⁻¹ with rye to 79 g CO₂–C ha⁻¹ d⁻¹ with blend, but MBC increased by 13 g CO₂–C ha⁻¹ d⁻¹ with blend to 120 g CO₂–C ha⁻¹ d⁻¹ with crimson clover from April 2001 to December 2002. Soil active C fractions varied between seasons due to differences in temperature, water content, and substrate availability in dryland cotton, regardless of cover crops. In irrigated cotton, increase in crop C input with legume + nonlegume treatment increased soil C storage and microbial biomass but lower C/N ratio of legume cover crops increased C mineralization and microbial activities in the spring.