草木栖、麦秸和泥炭在黑土中腐解特点及对土壤肥力的影响

有机物料田间腐解试验表明,各地均以草木栖分解最快,麦秸次之,泥炭最慢;同一有机物料的分解速率,北部克山均比南部哈尔滨慢。腐殖化系数,各地均以泥炭最大,麦秸次之,草木栖最小;同一有机物料的腐殖化系数,北部克山均比南部哈尔滨大。三种有机物料处理黑土:1.提高了腐殖质的数量和品质,增加了养分贮量和保肥能力,泥炭处理优于其他处理。2.明显地提高了胶体复合有机炭和追加复合度,草木栖处理最好,麦秸次之,再次是泥炭。3.改善了胶体腐殖质结合形态,松结态显著增加,土壤腐殖质更加活化,复合胶体的特性也均得到了改善。     

秸秆还田对稻田土壤溶液中溶解性有机质的影响

研究了麦秆不同方式还田、施用无机氮肥及不同移栽时间对水稻田土壤溶液中溶解性有机碳（DOC）、溶解性有机氮（DON）浓度的影响。结果表明，淹水后土壤溶液中DOC浓度在淹水初期明显增加，而后逐渐下降。添加麦秆这一有机物料，在水稻生长期前2个月内显著提高了DOC，对DON在一段时间内也表现出促进作用，其后差异不显著。施用无机氮肥降低了土壤溶液中DOC、DON浓度。DON的浓度与施肥量呈负相关。水稻推迟移栽，土壤溶液中溶解性有机质（DOM）均显著降低。     

THE KINETICS OF STRAW DECOMPOSITION IN RELATION TO ITS POTENTIAL TO PRODUCE THE PHYTOTOXIN ACETIC ACID

The losses of total weight and of the individual components of oat straw were followed under field conditions over one cropping season. Decomposition rates of cellulose and hemicellulose were closely similar, and together these polysaccharides accounted for most of the weight losses. Losses of lignin were small, and total weight loss can be calculated from the increase in percentage lignin in recovered samples. Straw retained the potential to produce phytotoxic concentrations of acetic acid only during the early stages of decomposition. Both the water soluble components and the readily available polysaccharides are probably substrates for the production of acetic acid. Early incorporation of straw minimised the potential for toxin production during winter.     

麦秸覆盖对盐渍土肥力及作物产量的影响

在田间条件下采用定位试验,研究了麦秸覆盖还田措施改良盐化潮土的作用和效果。结果表明:麦秸覆盖还田增加了土壤有机质和 N、P、K 等养分,降低了土壤 pH 值,改善了土壤的物理性状,促进了土壤脱盐;麦秸覆盖还田减少了地面水分的蒸发,有效保持土壤水分,从而抑制了盐分向地表的积聚;麦秸覆盖还田为玉米的正常生长发育创造了良好的土壤肥力基础,使玉米比对照增产 1470 kg/hm2,增产率为 16.20%。     

秸秆碳的田间原位分解和微生物量碳的周转特征

应用14 C示踪技术研究了杂交狼尾草秸秆在稻麦轮作田中为期 1年的原位分解。结果表明 :秸秆用量对其分解率影响甚微 ,1年后秸秆C分解了 72 %左右 ,分解速率常数为 2 7× 1 0 - 3d- 1,但秸秆用量的多少与土壤原有碳的分解和土壤有机碳平衡密切相关。黄棕壤原有C年分解率为 5 4 5 %～ 6 0 7% ,分解速率常数在 1 0 4× 1 0 - 4～ 1 1 8× 1 0 - 4d- 1之间。随秸秆用量增加 ,黄棕壤原有C分解率和分解量均增加 ,土壤有机碳的亏缺减少。微生物量14 C占加入秸秆14 C的 3 79%～ 1 0 63% ,占土壤残留14 C的 1 2 2 7%～1 7 4 3% ,其大小变化及减少程度均较微生物量12 C显著。微生物量12 C约为微生物量14 C的 0 74～ 3 85倍 ,说明大多数情况下 ,土壤原有C仍是土壤微生物活动所需能量和养分的主要来源。微生物量14 C的周转率在 1 1 0～ 1 1 8a- 1之间 ,微生物量12 C的周转率在 0 97～ 1 0 6a- 1之间。增加秸秆用量可加快土壤微生物量C的周转速度 ,反过来微生物量C周转速度的加快又加速了秸秆C和土壤原有C的分解。土壤原有C和秸秆C的分解进程与微生物量12 C和微生物量14 C的动态变化趋势一致 ,说明有机碳分解的快慢是土壤微生物活动强弱的外在表现。     

麦秸、氮肥与土壤混合培养时氮素的固定、矿化与麦秸的分解

应用3种土壤,在20℃和30℃温度下进行了与麦秸及不同量氮肥混合培养的试验,麦秸及氮化肥采取了¹⁵N标记、不标记的交叉处理。7周培养期间,各处理所含矿质氮包括所施化肥氮不同程度地被固定,一部分处理的起初被固定的矿质氮以后部分地得到释放,释放程度与土壤有机质和全氮含量以及培养温度有关。培养结束时,配施较多量氮肥的处理所施麦秸氮及化肥氮约有50-60%呈6N HC1水解氮组分之中,另有少量呈酸不溶性胡敏N形态,麦秸氮有4-17%矿化释放,化肥氮有10-50%仍为矿质氮形态,这些数值的高低基本上也与土壤的有机质和全氮含量以及培养温度有关。以一种土壤与非标记的麦秸和氮肥混合培养,测定了两个月期间的CO₂释放量,并未发现增加氮肥施量会促进麦秸分解,增施氮肥反而有稍为减缓麦秸C分解的趋势。     

秸秆还田与化肥配合施用对土壤肥力的影响

以山东省齐河县低肥力潮土为供试土壤 ,15年盆栽土培定位试验结果表明 ,长期秸秆还田并配施适量的化肥 ,是培肥地力 ,提高产量的有效措施之一。在秸秆还田量分别为 2 2 5 0、45 0 0、675 0kghm- 2 范围内 ,土壤有机质积累量 ,速效氮磷钾的生物有效性 ,脲酶活性强度等指标与秸秆还田量呈极显著正相关 ,并与气候、作物生长季节、土壤质地等因素有关     

作物秸秆碳在土壤中分解和转化规律的研究

采用14C标记秸秆,在大田和实验室的研究结果表明,秸秆的分解速率主要取决于C/N比。施入土壤后,土壤微生物迅速增加,尤其是细菌。秸秆降解首先形成非结构物质,其中大部分转化为富里酸,进而转化为胡敏酸。分解产物对土壤腐殖质的更新,从腐殖质表面官能团或分子断片开始,逐步进行。非结构物质可与腐殖酸的单个分子产生交联作用,在一定条件下,交联的复合分子可进入腐殖质分子核心的成分中。腐殖酸单个组分在土壤中的转化和重新分配,仅仅与腐殖质表面官能团的反交换过程密切相关。粘土矿物选择性吸附胡敏酸,而且优先吸附胡敏酸中低分子成分。     

秸秆还田对农田土壤风蚀影响的试验研究

土壤风蚀是形成沙尘暴导致土壤沙漠化的主要原因,它能够降低耕作层的保水性能和抗蚀能力,导致土壤肥力和生物生产量的下降,影响农业的可持续发展,对人类生存环境造成不同程度的危害[1]。土壤风蚀是一个复杂的物理过程,其根源除了严酷的自然气候外,有94·5%是人为掠夺式经营方式     

THE USE OF POLYACRYLAMIDE TO REPLACE CARBON IN THE DETERMINATION OF'OLSEN'S'EXTRACTABLE PHOSPHATE IN SOIL

The addition of 2.5 mg/l of polyacrylamide to 0.5M NaHCO₃ used as an extractant for ‘available’ phosphate overcame most of the analytical difficulties associated with the use of activated carbon which was recommended in the original procedure of Olsen et al. (1954). No significant differences in the amount of P extracted were found between polyacrylamide and carbon and with the former, technical problems were greatly reduced. Consequently, the modification of the original method to incorporate polyacrylamide has been adopted in the Agricultural Development and Advisory Service of the Ministry of Agriculture, Fisheries, and Food as a standard method for the determination of available phosphate in soils.     

DECOMPOSITION OF SOIL POLYSACCHARIDE

Polysaccharide material was isolated by absorption on charcoal from the acidified, non-humic fraction extracted by alkali from three soils. The polysaccharides were used as substrates in soil incubation, perfusion, and suspension experiments. Concordant results were obtained with freely drained Countess-wells and Insch Association soils derived from acidic and basic igneous parent materials respectively. Polysaccharide material added to soil at low concentration (I per cent) was apparently totally decomposed after 8 weeks when the amounts of polysaccharide in control and amended soils were statistically indistinguishable. At higher concentrations (2-3 per cent) a significant difference in reducing sugar, equivalent to about 30 per cent of the substrate, remained after 32 weeks. Partial neutralization of the polysaccharide material with calcium hydroxide increased the rate of decomposition in Countesswells Association soil but had an opposite, smaller effect in Insch Association soil. Soil polysaccharide material was decomposed slightly faster in perfusion and suspension experiments than in moist soil. Only 20 per cent of the carbohydrate in the unfractionated alkali–soluble organic matter of soil was decomposed during incubation in soil for up to 133 weeks. There was usually little change in the carbohydrate content of soil incubated alone. The soil microbial population showed a marked increase in response to added polysaccharide material but only slight qualitative changes were detected. It is concluded that the persistence of naturally occurring polysaccharide in soil is related to inaccessibility caused by chemical combination, complexing or insolubility but not to a biologically-stable molecular structure.     

应用穆斯堡尔谱(Mössbauer Spectroscopy)研究土壤磁性的发生机理

通过穆斯堡尔谱(MS)和磁测的综合分析,结果表明,我国磁性最强的昆明玄武岩红壤的磁性矿物,主要为磁赤铁矿、磁铁矿和钛赤铁矿。这些磁性矿物可解释为原生钛磁铁矿、钛铁晶石、钛铁矿的“离钛氧化作用”的产物,钛的游离使矿物向纯的磁铁矿、磁赤铁矿和赤铁矿转化,从而形成了土壤的强磁性和一定的磁化率剖面特征。     

无结构土壤透气性的初步研究

土壤的透气性是指土壤让空气穿透本身的能力。透气性是土壤很重要的物理性质,因为它不仅决定了土壤与大气间空气交换的速度^[1],而且和土壤的持水性有关^[2],测定土壤的透气性还可以了解土壤其他一系列的物理性质如排水的能力^[3]、地表迳流的速度^[2]、耐蚀性、空气容量^[3]及其结构性的程度等等。土壤中微生物活动的方向与强度、种籽的发芽、根系的发育及其吸收能力、土壤中养分的状态^[4]和影响农作物生活的其他重要土壤因素都有赖于土壤的透气性。     

秸秆还田对西藏中部退化农田土壤的影响

就不同秸秆还田方式对西藏中部退化农田土壤的影响进行了研究,结果表明:秸秆还田对增加土壤有机质、全N、速效P、全K和速效K具有重要作用。秸秆还田后,能提高土壤综合肥力水平,且有翻埋>高茬>覆盖的趋势。根据当地的生态条件,要控制西藏中部农田土壤的退化趋势,促进已退化土壤生产力的恢复和持续提高,建议该地区采用高茬方式进行秸秆还田。     

潮土中有机物质的分解与腐殖质积累

本文采用＾１４Ｃ标记示踪法研究我国北方潮土中有机物质的分解速率及其影响因素。潮土中有机物质的分解,除受气候条件影响外,还受土壤ＣａＣＯ３含量,水分及盐碱含量等因素的影响,并讨论了潮土有机质积累及提高潮土有机质含量的途径。     

STUDIES ON THE DECOMPOSITION OF PLANT MATERIAL IN SOIL

Soil samples taken during an experiment on the decomposition of ¹⁴C-labelled ryegrass in soil under field conditions (see Part I) were air-dried, irradiated, exposed to CHCl₃ or CH₃Br vapours, oven-dried or autoclaved. After these treatments the soils were inoculated, incubated, and the output of CO₂ measured. All these methods of partially (or, in some cases, completely) sterilizing soil rendered a small heavily labelled fraction of the soil organic matter decomposable. This fraction is postulated to be the soil biomass. Treatments involving heat or irradiation rendered small additional amounts of the soil organic matter decomposable (by processes other than the killing of organisms). Incubating unsterilized soil with partially sterilized soil did not decrease evolution of CO₂. This suggests that partial sterilization does not increase mineralization by destroying toxic substances that inhibit microbial growth, or by disturbing a host: predator balance in the unsterilized soil. The longer the labelled ryegrass was allowed to decompose in the field, the less labelled-CO₂ was evolved after partial sterilization. In contrast, the same amount of unlabelled-CO₂ was evolved from a soil that had been incubated 1 or 4 years with ryegrass. The labelled part of the biomass is considered to be largely zymogenic (with a half life of approximately 1.5 years), the unlabelled part largely autochthonous, remaining almost constant over the 3-year period. It is suggested that the size of the soil biomass can be roughly estimated from the size of the flush of CO₂ after CHCl₃ vapour treatment. Calculated on this basis, 2.3–3.5 Per cent the unlabelled-C in these soils (i.e. the C present in the soil before the labelled ryegrass was added) was in the biomass. Of the original ryegrass C added, 10–12 per cent was in the biomass after 1 year, decreasing to 4 per cent after 4 years.     

CONTRIBUTION OF SOIL MINERAL NITROGEN IN WHEAT PRODUCTION

A substantial amount of soil mineral nitrogen (Nmin) (NO₃—N + NH₄—N) exists in the effective rooting depth of most profiles. However, soil Nmin is usually not taken into account in fertilizer recommendations for crop production. The level of preplant-soil Nmin in the Cukurova region of Turkey is considerably high based on the high level of N application to many field and greenhouse crops. Therefore, soil Nmin was determined in the profiles of the wheat-field experiments, which were conducted at eight different locations. Nitrogen was applied in six rates as 1/2 at planting, 1/4 at tillering and 1/4 at booting stages. Wheat-grain yield was determined following harvest. Even though the yield was increased by the added rates of N, it was greater where the preplant soil Nmin values were measured as relatively high. Two years of results show that there are substantial amounts of soil Nmin in the profile, and it needs to be taken into account in fertilizer N recommendations.     

STUDIES ON THE DECOMPOSITION OF PLANT MATERIAL IN SOIL

The organic matter in soils containing decomposing ¹⁴C-labelled ryegrass was fractionated chemically. Earlier work on these soils had shown that they contained a small fraction, heavily labelled relative to the rest of the soil organic matter, that was mineralized when the partially sterilized soils were incubated. Reagents effective in extracting heavily labelled-C included cold o.in HC1, boiling saturated CaSO₄ solution, and o.in Ba(OH)₂, but neither these nor any other reagent tested could extract material as heavily labelled as that mineralized when partially sterilized soil was incubated. Reagents that extract heavily labelled-C are poor extractants for humified material and are not strongly hydrolytic: the more vigorous the hydrolysis the smaller the proportion of labelled-C in the hydrolysate. The amounts of labelled-C dissolved by Ba(OH)₂ from soils sampled after different periods in the field were directly proportional to the amounts of labelled-C mineralized by those soils when partially sterilized (by exposure to CHC1₃ vapour), inoculated and incubated. Balance sheets are presented for the distribution of labelled and unlabelled-C in fractions separated by hydrolysis with 6N HC1, by NaOH extraction, by neutral pyrophosphate extraction, and by oxidation with H₂O₂. The fraction remaining after hydrolysis with 6N HC1 was the most lightly labelled and had the widest C/N ratio. The percentage of labelled-C in the material dissolved by alkali or by pyrophosphate was little more than in the material not dissolved, despite the presence in the soil of fractions differing at least twenty-fold in intensity of labelling.     

保水剂有效使用的土壤水分条件及对小麦的增产效果

在中壤质潮土,土壤水分含量在50%FMC～80%FMC范围内,应用保水剂拌种可使小麦出苗率增加,出苗期提前,麦苗抗旱性增强,地上部鲜、干重明显增加。田间小麦增产4.49%～6.09%。     

Bt水稻杀虫蛋白时空变化及秸秆还田后在土壤中的持留规律

以Bt抗虫水稻华池B6、TT51及其非转基因水稻亲本嘉早935、明恢63,以及与它们亲缘较远但农艺性状相近的水稻品种中九B、R9311为试验材料,研究了田间种植条件下Bt抗虫水稻杀虫蛋白的时空变化及其在根际土中的持留规律,同时,还研究了秸秆还田后Bt蛋白在土壤中的持留规律。结果表明：1）Bt抗虫水稻华池B6植株各个部位...