土壤微生物量作为土壤肥力指标的探讨

对不同利用方式19个黑土样品的微生物量和养分进行了分析,结果表明林地的微生物量明显高于玉米地和大豆地,但玉米地和大豆地之间未表现出显著差异,土壤微生物量和土壤养分含量大体上都呈现出林地>大豆地>玉米地的一致的趋势;同时土壤微生物量与土壤有机质、全氮、全磷、速效钾和碱解氮呈现出显著或极显著正相关关系,分析结果还表明土壤微生物量碳作为评价土壤肥力指标比土壤微生物量氮更为灵敏。因此,土壤微生物量可以作为评价不同利用方式的黑土肥力水平的一个生物指标。     

玉米不同育苗方式下土壤团聚体及颗粒分形特征

稳定的土壤团聚结构对种子发芽、根系发育、作物生长以及有机碳保护有着重要的影响。农业管理措施对团聚体胶结剂质量和保存时间影响较大,必然影响土壤团聚体的形成和稳定,不同耕作和育苗方式作为重要的农业管理措施也必将对土壤团聚作用产生影响。选择玉米平作和垄作条件下6种育苗方式的土壤为供试材料,采用标准化平均质量直径和分形理论,探讨了土壤团聚体的稳定性、分形特征及二者之间的关系。结果表明,平作和垄作条件下6种育苗方式对土壤团聚体的稳定性影响不同,平作方式下,秸秆钵直播、包衣直播和垄作方式下,肥团育苗、秸秆钵育苗更有利于大于0.25 mm粒径较大团聚体的形成,对土壤形成稳定的结构具有积极意义;土壤团粒的分形维数与小于0.25 mm粒径含量呈极显著正相关,与0.5～1 mm、1～2 mm粒径含量呈极显著负相关,说明土壤团粒的分形维数越小,土壤团聚体稳定性越强。研究结果说明土壤团聚体的分形维数可以客观地表征土壤结构的稳定性,可以作为表征土壤结构和性质的重要参数,对于深入探讨分形学在土壤综合评价中具有重要意义。     

长期平衡施肥对潮土微生物活性和玉米养分吸收的影响

利用中国科学院封丘农业生态实验站农田生态系统养分平衡长期定位试验地,研究氮磷钾平衡施肥(NPK)与缺素施肥(NK、PK、NP)对土壤微生物生物量、酶活性、呼吸强度以及玉米养分吸收的影响。结果发现,与不施肥对照(CK)相比,NPK处理玉米根系与茎叶生物量、籽粒产量以及植株氮磷钾吸收量均大幅提高,NP处理次之,PK与NK处理则无显著影响;同一处理玉米茎叶与根系养分含量接近,而籽粒的全氮和全磷含量较高、全钾含量偏低;与NPK处理相比,缺施氮、磷或钾肥均直接导致玉米植株相应养分的明显亏缺或其他养分的过量富集,但在根系、茎叶和籽粒部位的累积情况存在一定差异。与CK相比,所有施加磷肥的处理(NPK、NP、PK)土壤微生物生物量(碳、氮、磷)、脱氢酶、转化酶、脲酶与碱性磷酸酶活性以及土壤微生物代谢活性和土壤基础呼吸强度均显著升高(p<0.05),土壤微生物代谢熵则显著下降(p<0.05),而缺施磷肥的NK处理除显著提高脲酶活性外(p<0.05),对其他指标均无显著影响。结果表明,氮磷钾平衡施肥在促进土壤微生物繁育和保育微生物代谢活性以及促进作物生长和保证养分吸收等方面显得非常重要,而缺素施肥中以缺施磷肥的不利影响最为突出。     

Aggregation in a surface layer of a hardsetting and crusting soil as influenced by the application of amendments and grass mulch in a South African semi-arid environment

Hardsetting and crusting are forms of soil structure degradation associated with the collapse of macroaggregates during wetting and are responsible for poor seedling emergence, crop establishment and yields of food crops especially in semi-arid environments. This study investigated the effects of applying of 3.0 t ha⁻¹ phosphogypsum, 1.0 t ha⁻¹ polymer gel, 3.0 t ha⁻¹ grass mulch and 5.0 t ha⁻¹ cattle manure to the topsoil (0–15 cm) of a soil with hardsetting and crusting behavior and observed changes on aggregation under field conditions for two consecutive seasons. There were significant improvements in soil aggregate properties in the amended soil over the control. Both aggregate size distribution and wet aggregate stability showed significant differences between the amendments in the two seasons. The mean weight diameters of aggregates were 4.23 mm (mulch), 3.31 mm (manure), 2.17 mm (polymer gel), 2.23 mm (phosphogypsum) and 1.36 mm (control). The aggregates (2–4 mm) from amended soil were consistently more stable than the control and were in the order polymer gel = manure > mulch > gypsum > control. Tensile strength and bulk density of aggregates, on the other hand, were significantly higher (P < 0.05) in the unamended than amended soil.The application of soil amendments, especially mulch, significantly increased the soil water content over the two seasons and this was associated with lower soil penetration resistance in the latter. The reduced soil strength in the amended soils contributed to higher pegging, podding and grain yields of bambara groundnut (Vigna subterranean). This was confirmed by significantly higher correlations between soil aggregate characteristics, soil water, penetrometer resistance and growth and yield of bambara groundnut. The study concluded that significant improvements in soil aggregation can be obtained over a relatively short period and this can improve the yield of food crops.     

Rate of soil‐aggregate formation under different organic matter amendments—a short‐term incubation experiment

To improve soil structure and take advantage of several accompanying ecological benefits, it is necessary to understand the underlying processes of aggregate dynamics in soils. Our objective was to quantify macroaggregate (> 250 μm) rebuilding in soils from loess (Haplic Luvisol) with different initial soil organic C (SOC) contents and different amendments of organic matter (OM) in a short term incubation experiment. Two soils differing in C content and sampled at 0–5 and 5–25 cm soil depths were incubated after macroaggregate destruction. The following treatments were applied: (1) control (without any addition), (2) OM₁ (addition of OM: preincubated wheat straw [< 10 mm, C : N 40.6] at a rate of 4.1 g C [kg soil]^–1), and (3) OM₂ (same as (2) at a rate of 8.2 g C [kg soil]^–1). Evolution of CO₂ released from the treatments was measured continuously, and contents of different water‐stable aggregate‐size classes (> 250 μm, 250–53 μm, < 53 μm), microbial biomass, and ergosterol were determined after 7 and 28 d of incubation. Highest microbial activity was observed in the first 3 d after the OM application. With one exception, > 50% of the rebuilt macroaggregates were formed within the first 7 d after rewetting and addition of OM. However, the amount of organic C within the new macroaggregates was ≈ 2‐ to 3‐fold higher than in the original soil. The process of aggregate formation was still proceeding after 7 d of incubation, however at a lower rate. Contents of organic C within macroaggregates were decreased markedly after 28 d of incubation in the OM₁ and OM₂ treatments, suggesting that the microbial biomass (bacteria and fungi) used organic C within the newly built macroaggregates. Overall, the results confirmed for all treatments that macroaggregate formation is a rapid process and highly connected with the amount of OM added and microbial activity. However, the time of maximum aggregation after C addition depends on the soil and substrate investigated. Moreover, the results suggest that the primary macroaggregates, formed within the first 7 d, are still unstable and oversaturated with OM and therefore act as C source for microbial decomposition processes.     

土壤有机质含量与玉米生产力的关系

土壤有机质是土壤肥力的重要指标。本文通过空间移位的方法,将东北黑土带由南向北5个点有机质含量为18.1g kg-1、31.1g kg-1、54.6g kg-1、103.9g kg-1、53.6g kg-1的农田黑土,分别移至黑龙江省的海伦市和吉林省的德惠市的两种气候下,通过田间试验的方法,研究了黑土有机质含量与玉米生产力的关系。结果表明,在相同的施肥条件下,土壤有机质含量与玉米产量间不存在显著相关关系,产量差异不显著;施肥对各种有机质含量的黑土均有显著增产作用,增产幅度在12.3%～64.1%,黑土带的南部区域德惠市的施肥增产作用要明显高于北部区域海伦市的增产作用。     

不同施肥制度对玉米生育期土壤微生物量的影响

通过测定不同施肥制度下玉米土壤微生物量碳、氮的动态变化,探讨了不同施肥制度对玉米土壤的培肥效应。研究结果表明,与无肥、单施有机肥、单施化肥相比,有机肥与N、P、K肥配合施用能显著增加玉米各生育时期的土壤微生物量碳、氮,促进土壤微生物量显著增长,增强了土壤养分容量的供应强度,有利于培肥土壤。     

滇中高原华山松植物多样性与土壤生物肥力特征

为探究滇中高原华山松植物多样性与土壤生物肥力的关系,运用野外调查法和实验室分析法对玉溪市磨盘山国家森林公园的华山松天然次生林进行了研究。结果表明:1磨盘山华山松天然次生林形成以华山松为优势种的针阔混交林,其物种组成单一、植物多样性较低,共出现维管束植物13科15属15种。2华山松林下有机质、全氮、碱解氮、全磷、有效磷、速效钾含量,酶活性及微生物数量随土层深度的加深呈递减趋势,pH、全钾含量随土层深度的加深而呈递增趋势。3主成分分析结果显示,土壤养分、过氧化氢酶、转化酶和微生物都能较好地反映土壤生物肥力特征,多样性指数、优势度指数以及丰富度指数这3个因子能够较好地反映植物多样性。4华山松植物多样性与土壤肥力特征具有明显的相关性,其中对植物多样性影响较大的土壤肥力指标有真菌、过氧化氢酶、全氮、速效钾、全钾、转化酶、细菌、全磷、有效磷。     

黄土高原不同植物群落土壤团聚体中有机碳和酶活性研究

以黄土高原延河流域森林区3种典型植物群落为研究对象,研究了3种植物群落土壤团聚体中有机碳的含量、组分及土壤酶活性,分析了有机碳与酶活性的关系。结果表明:(1)3种植物群落,土壤团聚体各种形态有机碳和酶活性均表现为0~10 cm土层含量高于10~20 cm土层,辽东栎群落0~10 cm土层土壤多酚氧化酶活性却低于10~20 cm土层。(2)土壤团聚体有机碳含量在植物群落间表现为:辽东栎群落人工刺槐群落狼牙刺群落,酶活性在植被群落间的高低表现则不一致。土壤有机碳含量和酶活性在团聚体间均表现为随团聚体粒级的增大而增大,或先增大再减小的趋势。(3)蔗糖酶、纤维素酶以及β-D葡糖苷酶活性与各种形态有机碳均呈显著的正相关关系,多酚氧化酶和过氧化物酶与有机碳含量相关性不显著。(4)辽东栎群落和狼牙刺群落土壤团聚体蔗糖酶、纤维素酶、以及β-D葡糖苷酶活性在团聚体中表现为:|0.25 mm团聚体||2~0.25 mm团聚体||5~2 mm团聚体||5 mm团聚体|,其多酚氧化酶和过氧化物酶以及人工刺槐群落各种土壤酶活性均表现为2~0.25 mm粒级团聚体中最大。(5)β-D葡糖苷酶活性增大,能促进土壤各种有机碳含量增加;土壤蔗糖酶活性和β-D葡糖苷酶活性的提高有助于土壤活性有机碳含量增加;土壤多酚氧化酶活性的增大,有利于土壤腐殖质碳的积累。     

土壤质量生物学指标研究进展

本文对近年土壤微生物、土壤酶活性和土壤动物等土壤质量生物学指标研究成果进行了综合评述。土壤微生物是土壤有机组分和生态系统中最活跃的部分,被认为是最敏感的土壤质量生物学指标:微生物生物量代表参与调控土壤中能量和养分循环及有机物质转化所对应微生物的数量,但须结合多样性研究以弥补其无法反映土壤微生物组成和区系变化的缺陷;微生物群落组成和多样性动态反映土壤中生物类群的多变性和土壤质量在微生物数量和功能上的差异;土壤微生物活性体现在土壤微生物商、微生物呼吸和代谢商等方面,应考虑生物量大小与微生物种群活性间的相关关系以反映微生物种群内的差异。土壤酶活性具有极高时效性,在较短时间内就能反映出土壤质量的变化。土壤动物通常以种类的组成和数量,土壤动物区系的相对丰度、多样性或活性作为评价土壤生物质量的敏感指标。与土壤理化指标相比,土壤生物学指标更能对土壤质量的变化做出灵敏迅速的响应,因而被广泛地用于评价土壤质量。     

模拟侵蚀与施肥对东北黑土土壤质量和玉米产量的影响

土壤侵蚀是导致东北黑土区土壤退化和作物生产力降低的主要因素,但关于土壤侵蚀对黑土土壤质量和作物生产力影响的定量评价相对较少。基于2005年在黑龙江省嫩江市鹤山农场建立的土壤侵蚀—生产力关系田间小区试验,在试验布设后的第18年（2022年）,系统研究了模拟侵蚀和施肥对土壤理化生性质、土壤质量和玉米产量的影响。试验为不同侵蚀程度（设0、10、20、30、40、50、60和70 cm 8个侵蚀深度）和施肥（不施肥和施肥2个水平）的二因素完全随机区组设计。测定项目包括土壤耕层（0~20 cm）的主要理化性质（包括容重、黏粒含量、含水量、pH、有机碳、碱解氮、速效磷、速效钾）、生物学性质（包括微生物生物量碳、微生物生物量氮及过氧化氢酶、脲酶、β-葡萄糖苷酶和纤维素酶活性）和玉米产量。结果表明：1）随模拟侵蚀深度增加,土壤黏粒、有机碳、碱解氮、速效磷、微生物生物量碳含量和纤维素酶活性显著下降,土壤容重和速效钾含量显著增加;施肥导致土壤容重、pH、速效钾含量和过氧化氢酶活性显著下降,黏粒、有机碳、碱解氮、速效磷含量及脲酶、?-葡萄糖苷酶、纤维素酶活性显著增加。施肥削弱了土壤脲酶活性、容重与其他理化性质间的相关关系。2）模拟侵蚀导致土壤质量和玉米产量显著降低,且主要发生在侵蚀深度为40 cm前。侵蚀深度40 cm时土壤质量指数分别下降28.1%（不施肥处理）和26.7%（施肥处理）,玉米产量分别下降了45.8%（不施肥处理）和11.7%（施肥处理）。施肥使土壤质量指数和产量分别增加7.0%和3倍。3）影响侵蚀条件下土壤质量的主要因素在不施肥处理下为纤维素酶活性、微生物生物量碳和碱解氮含量,施肥处理则为纤维素酶活性、微生物生物量碳和速效磷含量。影响侵蚀条件下玉米产量的主要因素不施肥处理为碱解氮含量,施肥处理则为速效磷含量。上述结果初步阐明了土壤侵蚀影响黑土土壤质量和生产力的程度及主要因素,对于退化黑土土壤修复有一定指导价值。     

Temporal response of soil biochemical properties in a pastoral soil after cultivation following high application rates of undigested sewage sludge

Soil biochemical properties were measured annually between 1995 and 1999 in soil from an 8-ha site that had received over 1,000 wet tonnes ha^–1 undigested sewage sludge, 1–4 years earlier. Basal respiration generally declined with time and was usually greatest in the untreated control area. This trend was attributed to a similar trend in soil moisture content. In contrast, microbial biomass C increased with time and also generally increased with sludge treatment age. Microbial biomass C, and to a lesser extent sulphatase activity, accurately predicted the order of sludge application to the site. This was perceived as a function of time since tillage and pasture establishment, with activities increasing in parallel to the build up of C residues in the soil, and not an effect of sludge or its composition. Except immediately after sludge application, there was no effect on N mineralisation and nitrification. None of the biochemical properties was strongly correlated with heavy metal concentrations. Our results suggest that there was little effect on soil biochemical properties, either adverse or beneficial, of adding raw sewage sludge to this site. Although a companion study showed considerable mobility and plant uptake of heavy metals, this difference could mainly be attributed to a different sampling strategy and the effects of intensive liming of the site.     

子午岭林区植被自然恢复下土壤剖面团聚体特征研究

研究了子午岭林区七种植被类型土壤>0.25 mm水稳性团聚体含量、团聚体破坏率和水稳性团聚体分形维数随植被恢复的变化规律以及这3个指标随土壤有机碳含量增加的变化规律。结果表明:植被恢复对>0.25 mm水稳性团聚体含量、团聚体破坏率和水稳性团聚体分形维数的影响可以达到70 cm土层;除白羊草群落外,0-70 cm土层上>0.25 mm水稳性团聚体含量随植被恢复逐渐提高,团聚体破坏率和水稳性团聚体分形维数随植被恢复逐渐减小,土壤结构随植被恢复逐渐改善。>0.25 mm水稳性团聚体含量、团聚体破坏率和水稳性团聚体分形维数与土壤有机碳之间呈极显著对数相关关系(p=0.01,n=32),当有机碳含量低于18.1 mg/g时,>0.25 mm水稳性团聚体含量随有机碳含量提高而明显提高、团聚体破坏率和水稳性团聚体分形维数则随有机碳含量提高而明显降低,即土壤结构稳定性明显提高;当有土壤机碳含量高于18.1 mg/g,>0.25 mm水稳性团聚体含量、团聚体破坏率和水稳性团聚体分形维数渐趋稳定,即在白羊草、虎榛子、山杨和辽东栎阶段的0-5 cm土层土壤结构达到稳定状态。     

激发式秸秆还田对麦季潮土团聚体中酶活性的影响

秸秆还田是提升潮土有机质、改良土壤结构的重要措施。添加有机肥和微生物菌剂可激发土壤微生物活性,促进秸秆腐解、提高土壤酶活性。本研究通过潮土区田间小区试验,研究激发式秸秆还田及微生物菌剂对土壤团聚体中酶活性的影响,结果表明:在小麦整个生育期:(1)施加有机肥(8%氮来自有机肥)的处理,不同级别团聚体中的酶活性(脲酶、蔗糖酶、纤维素酶、碱性磷酸酶)比一次性施肥及常规施肥处理高8.15%~66.93%,且差异显著(P0.05);施加有机肥对0.25~0.053 mm团聚体中纤维素酶和碱性磷酸酶活性的增加效果明显;(2)添加微生物菌剂可提高不同级别团聚体中脲酶、纤维素酶、蔗糖酶和碱性磷酸酶的活性,不同酶活性的增幅存在差异;(3)团聚体中脲酶、纤维素酶活性在苗期较低而后逐渐升高;蔗糖酶、碱性磷酸酶的活性在苗期较低,至拔节期大幅升高而后逐渐降低;(4)氮肥不同基肥与追肥比例对土壤团聚体中酶活性也有一定影响:试验表明,基追比为5︰5的处理不同级别团聚体中脲酶、纤维素酶、蔗糖酶和碱性磷酸酶的活性高于基追比6︰4的处理。     

Soil Health of Recently Converted No-till Corn Fields in Maine

ABSTRACT

No-till (NT) forage production in Northeast United States is growing due to farmers’ desire to reduce costs. Soil samples (15cm deep), soil penetrometer values (depth to 300 psi), and earthworm midden counts were collected from 59 fields on 14 dairy farms in Maine planted to corn. Of the 59 fields sampled, 13 fields received light tillage in the sampling year, 40 had not been tilled within 5 years, and 6 fields had not been tilled for a minimum of 12 years. Median soil health scores (SHS) varied among farms, from 23 to 43 based on the 0 to 50 Woods End SHS scale, based more on past soil management. Most soil quality attributes were significantly correlated indicating that they were useful predictors of soil quality. Among fields not tilled in 5 years, we found no relationship of SHS to time in NT. Fields with greater earthworm activity had higher SHS indicating increased biological activity and potentially improved productivity resulting from better drainage and aeration. Farmers were asked to identify their highest and lowest soil quality fields, but according to the SHS, they were 56 percent successful. Three cornfields on three different farms were NT planted into herbicide killed long-term perennial hay fields; each of these had the highest SHS, but no farmer recognized that. More education on rotating perennial forage crops with NT corn is needed. No-till forage production can improve soil health, reduce fuel and labor costs by more than $50/acre, and residue cover can reduce soil erosion impacts.