不同水稻品种混作养鸭对土壤养分动态的影响

鸭稻共作和水稻混种均可产生良好的生态效应,但能否将两项技术结合起来,即通过不同水稻品种混种与稻田养鸭的叠加,进而产生"1+12"的生态效应和生产效益,是一项值得加以实践和探讨的课题。为探明多品种水稻混作养鸭这类复合生物多样性利用模式的应用可行性,本试验设置了水稻单作常规种植(施药施肥)、水稻单作养鸭、水稻单作空白对照(不养鸭不施肥药)、水稻品种混作常规种植(施药施肥)、水稻品种混作养鸭和水稻品种混作空白对照(不养鸭不施肥药)6种种植模式开展田间试验,研究不同水稻品种混作养鸭对土壤养分动态和稻米品质的影响。结果表明:种植双季稻后,水稻品种混作养鸭处理下土壤有机质含量显著高于其他种植模式。早晚季水稻生长期间水稻品种混作养鸭处理的土壤全氮含量低于水稻品种混作常规种植处理,但均显著高于其他处理;水稻品种混作养鸭处理的土壤碱解氮含量较其他处理显著提高。各处理土壤速效磷含量以水稻单作空白对照处理的最高,总体上,混作处理比单作处理平均土壤速效磷含量高。种植双季稻后,水稻品种混作养鸭种植模式的土壤全钾和速效钾含量均高于其他处理。水稻品种混作养鸭处理的稻米出糙率、精米率、直链淀粉含量和胶稠度较其他处理高,且垩白粒率较其他处理低。综合表明,水稻品种混作养鸭模式更有利于改善田间土壤养分状况,提高稻米的品质,故此模式可为优质健康稻米生产提供新途径。     

A scheme for soil classification of paddy fields in Japan with special reference to mineral paddy soils

Introduction

Paddy (irrigated) rice is the most important single crop in Japan. Nearly half of the total arable lands covering approximately 6.5 million hectares, are devoted to the growing of the rice plant. It is grown mainly on the alluvial plains which are intensively cultivated, and are the most productive soils of the country. Since the idea of modern pedology was introduced into Japan, some work has been done by some Japanese investigators to classify paddy soils on the basis of their morphological characteristics. A brief historical review on the soil survey work in Japan has been given by Kamoshita⁸⁾. In 1936 Kawamura described methods of soil survey in Korea through a careful study of the work developed by Stremme and his colleagues in Danzig. In those days Kamoshita⁹⁾,¹⁰⁾ devised a scheme of paddy soil classification by applying the concept of the wet soil types (mineralische Nassböden) proposed by Stremme, and he established five predominant soil types as follows: Bog soils (Moorböden), Half-bog soils (anmoorige Böden), Meadow soils (Wiesenböden), Gray lowland soils (graue Auenböden), and Brown lowland soils (braune Auenböden). The names in parentheses represent the wet soil types proposed by Stremme. These soil types are subdivided into soil kinds (Bodenarten) on the basis of differences in texture, rusty mottling, and humus content. The soil kinds were used as both categorical and cartographical units for detailed soil surveys.     

土壤改良剂对冷浸田土壤特性和水稻群体质量的影响

以南方典型冷浸田为研究对象, 在明沟排水的基础上, 通过田间定位试验, 以不施土壤改良剂为对照, 研究了施用不同土壤改良剂(自研的脱硫灰改良剂、生物活性炭, 市售的土壤改良剂石灰、硅钙肥、腐植酸)对冷浸田氧化还原电位、土壤呼吸强度、土壤微生物数量、水稻群体构建及产量构成因素的影响。结果表明, 施用改良剂能够改善土壤理化性状, 提升土壤速效养分和pH,但除脱硫灰处理外, 其他改良剂处理对土壤Eh未产生显著影响。施用不同土壤改良剂在水稻各生育期均能有效增强土壤微生物呼吸强度和放线菌数量, 并且放线菌数量达到差异性显著水平(P<0.05), 生物活性炭处理下土壤呼吸强度和放线菌数量分别较对照增加67.6%和127.6%。各土壤改良剂处理与CK相比较均有助于提高叶片SPAD、茎蘖数、水稻干物质积累量、成穗数、穗粒数、产量结实率和根系伤流速率。其中以脱硫灰和生物活性炭处理改良效果最佳, 抽穗后29 d时,根系伤流速率较CK分别提高45.4%和39.1%, 叶片SPAD分别增加27.4%和22.5%; 成熟期水稻成穗数较对照提高12.1%和10.7%,干物质积累量增加68.8%和50.5%,产量分别增加12.8%和10.3%。综上所述, 土壤改良剂可有效改善冷浸田土壤特性及水稻群体质量, 脱硫灰和生物活性炭处理的改良效果最明显, 增产幅度最大。     

Role of soil redox in growth and fertilizer nitrogen uptake by rice in Thailand paddy soils

Abstract. In a laboratory study, ¹⁵N ammonium fertilizer uptake and rice growth was determined in a non-acid sulphate marine soil (Typic Tropaquept) and an acid sulphate soil (Sulfic Tropaquept). Acid sulphate sensitive (IR 26) and acid sulphate tolerant (IR 46) rice varieties were grown in soil suspensions incubated at four Eh levels (+500, +250, +50, and -150 mV) in microcosms for three weeks. The results showed that rice grown in non-acid sulphate marine soils gave slightly better dry matter weight of 1.8g/pot, greater ¹⁵N uptake of 12.8 mg N/pot, and higher total N uptake of 38.4 mg N/pot than under acid sulphate soil conditions indicating the non-acid marine soil is more favourable to rice culture. Growth as measured by weight of dry matter was significantly reduced from 2.1g/pot under oxidized condition (+500 mV) to 0.8g/pot under highly reduced condition (-150 mV). N uptake by rice was significantly reduced from 16.9 mg/pot at + 500 mV to 4.5 mg N/pot at -150 mV Total N uptake also decreased with decreasing Eh. Growth, ¹⁵N uptake and total N uptake by acid sulphate tolerant rice, IR 46 were significantly higher than the acid sulphate sensitive rice variety, IR 26. Under highly reduced soil conditions (-150 mV), growing rice in acid sulphate soil would require additions of lime, intermittent irrigation and/or mid season drainage in order to increase soil redox potential and remove toxic substances.     

Status of paddy soils as affected by paddy rice and upland soybean rotation in northeast Japan,with special reference to nitrogen fertility

To investigate the current available nitrogen (N) and chemical properties of paddy soils affected by crop rotation between irrigated paddy rice (Oryza sativa L.) and upland soybean [Glycine max (L.) Merr.] (paddy-upland rotation), topsoils were collected from 22 fields of four different farmers in the northeastern region of Japan. Regardless of organic material application, a significant negative correlation was found between available soil N and an increase in the proportions of upland seasons to total crop seasons after the initiation of paddy-upland rotation. Soil total N and total carbon (C) also tended to decrease with an increase in upland frequency. In fields with repeated applications of cattle manure compost, the soil available N was higher than in fields where only crop residue was applied. A significant negative correlation was also found between the soil available N:total N ratio and upland frequency. This indicates that the part of soil N related to available N was notably lost by the use of paddy fields as upland fields. In order to sustain available soil N over the minimum suitable level of 80?mg?kg^?1, upland frequency should not exceed 65% when only crop residues and no other organic materials are applied. The upland frequency can be raised by the repeated application of organic materials which maintain a higher level of available soil N. The results imply that care should be taken to maintain the N fertility of paddy soil at a suitable level in paddy-upland rotation, and that upland frequency and organic materials applied are important factors to do this.     

Effects of Sesbania rostrata and Azolla microphylla incorporation on transformation of applied zinc and copper in lateritic rice soils with different flooding regimes

Fixation of Zn and Cu applied to tropical rice-growing lateritic soils rich in Fe-oxides may be reduced if the soils are kept flooded for a few days before their application. There may be a further reduction if such flooding is combined with incorporation of green manures. To investigate this effect, a laboratory experiment was conducted to study the effect of different periods (0 and 15 days) of preflooding combined with (0 and 0.50% of soil weight) Sesbania rostrata and Azolla microphylla incorporation as green manures on the transformation of applied Zn and Cu in two lateritic rice-growing soils. Recovery of added Zn/Cu in DTPA (diethylene triamine pentaacetate)-extractable form was always found to be higher when they were applied after the soils were maintained in a flooded state for 15 days than when applied immediately after flooding; this effect was more prominent in respect of Cu. Contrary to expectations, green manure incorporation along with preflooding caused a significant decrease in recovery of Zn/Cu; the effect, however, showed a decreasing trend as incubation progressed. The effect was more marked with A. microphylla than with S. rostrata, particularly with Cu. Possible causes of such changes and their implications on the Zn/Cu nutrition of rice are discussed. Received: 7 August 1995     

改良剂对反酸田土壤性质与水稻产量的影响

采用盆栽试验研究了不同改良剂在反酸田土壤上的应用效果。结果表明,土壤pH在3.47~4.90范围内,pH与交换性H+和交换性Al3+呈极显著线性负相关关系,而与土壤有效铁和有效硫含量呈显著正相关。不同改良处理在提高作物产量和改良土壤性质方面较对照处理与NPK处理效果明显,且钙镁磷肥、自研改良剂、石灰及碱渣等无机改良剂改良效果显著高于添加腐植酸、精制有机肥、碱性有机肥处理。其改良效果主要体现在提高土壤pH,显著降低土壤交换性H+和交换性Al3+含量,明显增加土壤有效钙和有效镁的含量,改善根系生长环境,增加水稻地上部养分吸收和水稻籽粒产量。综上,初步认为酸害(包括活性酸和潜在酸)是反酸田土壤最主要的限制因子,钙镁磷肥、自研改良剂和石灰等偏碱性且富含有效钙或磷的无机矿物质是农业生产中改良反酸田的适宜改良剂。     

Sonic dispersion of soil DTPA solution suspension as an extraction procedure for DTPA micronutrient test

Abstract

To examine sonic dispersion as an extraction procedure for DTPA micronutrient test, soil DTPA solution suspensions were sonicated to extract Fe, Zn, Mn, and Cu. The elements extracted after 15 or 60 seconds sonication were compared with those extracted after 1/2 or 2 hours shaking.

The mean differences between Fe, Zn, Mn, or Cu extracted after 15 seconds sonication and those extracted after 1/2 hour shaking were not significant. However, the extractions obtained after 2 hours shaking were significantly higher than those obtained after 15 or 60 seconds sonication.

The elements extracted after 15 or 60 seconds sonication correlated significantly with those extracted after 1/2 or 2 hours shaking. Therefore, 15 or 60 seconds sonication can replace 2 hours shaking in the extraction procedure for DTPA micronutrient test. However, 15 seconds sonication is more convenient than 60 seconds and does not require cooling of soil solution suspension during sonication. Therefore 15 seconds sonication ‐ a replacement for 2 hours shaking to extract Fe, Zn, Mn, and Cu ‐ is recommended.     

Characteristics of the soils developed under broad-leaved evergreen forests in okinawa prefecture and the kinki district with special reference to their pedogenetic processes

Abstract

Properties of sesquioxides, clay mineralogical composition, and charge characteristics of the soils developed under broad-leaved evergreen forests in Okinawa Prefecture (subtropical climate) and the Kinki District (warm temperate climate) were studied with special reference to their pedogenetic processes in order to reexamine the corresponding parameters of Brown Forest soils and related soils in Japan.

The soils in Okinawa Prefecture were characterized by a higher degree of weathering as compared to the soils in the Kinki District. Major differences involved the values of the Fed/Fet ratio for the soil samples throughout the profile, and those of the ratios of (Fed-Feo)/Fet, CEC/clay, and (Feo + Alo)/ clay and the content of CaO plus Na₂O for the B horizon. The soils in the Kinki District did not show andic soil properties, nor Al translocation in the profile and, both of which were characteristic of Brown Forest soils developed under cool temperate climatic conditions at high altitudes in the same District.

The difference in the degree of weathering were reflected on the charge characteristics at the very surface of the soils, i.e., the surface of the particles of the soils in Okinawa Prefecture exhibited a lower reactivity as compared with those of the soils in the Kinki District.     

中国南方潴育性水稻土产量演变及其肥力驱动因素分析

系统分析了我国广西桂林、钦州及玉林3个潴育性水稻土长期常规施肥(F)和不施肥(CK)处理下,双季稻产量及土壤肥力随时间的变化趋势,并借助通径分析探明主要肥力因素对各点水稻产量的驱动差异和关联。结果显示,不施肥条件下,桂林点的基础地力较低,其产量随时间呈显著下降趋势(各季产量均值666~846 kg hm-2),而玉林和钦州点基础地力相对较高,其产量在试验期间相对稳定(各季产量均值3 500~4 577 kg hm-2)。常规施肥下,桂林点产量显著提高(较CK增产522%),且随时间呈显著上升趋势,另两试验点较CK增产20%~67%。常规施肥下,土壤肥力随时间呈稳定或不同程度的上升趋势,其中土壤有效磷初始值低于10 mg kg-1的桂林和钦州点上升幅度最大且均达到显著水平,而初始值为50 mg kg-1的玉林点变化不大。土壤有机质与全氮变化在各地不同,气温偏低的桂林点有机质呈上升趋势且全氮含量较高(3 g kg-1),气温偏高的玉林和钦州点有机质呈下降趋势且全氮含量较低(1~2.5 g kg-1),表明有机质的累积和释放上存在差异。双季稻产量的主要肥力驱动因子各地有差异,桂北地区桂林点土壤有效磷为首要因素,桂南地区玉林和钦州点土壤有机质及氮含量为主要的肥力因素。因此,依据区域特征采取有针对性措施是持续、高效培肥土壤的保证。     

低产水稻土改良与管理研究策略

我国耕地后备资源极端缺乏,改良低产田是提高粮食产量的重要途径。低产水稻土作为低产田的重要组成部分,相关肥力特征及其改良技术研究比较零散,缺乏系统科学的调控管理策略。本文从低产水稻土类型、新的改良研究方法角度,探索可能的技术突破。基于农业部统计数据,因环境条件不良或土壤自身存在障碍因素,全国约有7.67×106hm2低产水稻土。按其主导成因,低产水稻土可分为冷潜型、粘结型、沉板型、毒质型四类。土壤质量评价是低产水稻土研究的重要方面,其评价方法主要包括土壤质量动力学法、土壤质量综合评分法、多变量指标克立格法、土壤相对质量评价法,现已发展了基于GIS的区域尺度水稻土质量评价方法,以及基于土壤生物学性状的质量评价方法。低产水稻土改良研究更多关注新技术和新方法,稳定性同位素探针技术、傅里叶变换红外光谱法(FTIR)和固相交叉极化魔角自旋13C核磁共振(CPMS13C-NMR)波谱技术的应用,将土壤有机碳的微团聚体分布、腐殖质的转化及其与土壤矿物结合机制深入到微观水平;同时高通量测序、土壤宏基因组学、宏转录组学等方法将相关研究推向分子水平。低产水稻土改良与管理的技术主要涉及到冷潜型、粘结型、沉板型、毒质型四大类低产水稻土的改良技术,基于产量反应和农学效率的推荐施肥方法是水稻土养分管理方法的重要发展方向。1)在低产水稻土质量评价方面,未来要结合不同低产类型的障碍因素开展个性化的土壤质量评价,如白土的质地和耕层厚度,加强引入土壤生物学指标进行土壤质量评价研究。2)在低产水稻土改良方面,要研究稻田障碍层次的形成机理与调控途径;研究其他低产类型如新垦水稻土、盐渍化水稻土、石灰化水稻土和污染水稻土的改良技术;研究长期改良措施对不同粒级团聚体腐殖质结构、酶类、微生物多样性和功能基因的影响。3)在低产水稻土管理方面,着重研究秸秆还田技术、推荐施肥技术、抗逆品种技术、群体控制技术。     

添加生物质炭对红壤水稻土有机碳矿化和微生物生物量的影响

通过室内培育试验,研究了添加生物质炭对江西红壤水稻土有机碳矿化和微生物生物量碳、氮含量的影响。结果表明:红壤有机碳矿化速率在培育第2天达最大值后迅速降低,培养7天后下降缓慢并趋于平稳;添加生物质炭降低了土壤有机碳的矿化速率和累积矿化量,培养结束时,不加生物质炭的对照处理中有机碳的累积矿化量分别比添加0.5%和1.0%生物质炭的处理高10.0%和10.8%。此外,生物质炭的加入显著提高了土壤微生物生物量,添加0.5%生物质炭处理的土壤微生物生物量碳、氮含量分别比对照高111.5%～250.6%和11.6%～97.6%,添加1.0%生物质炭处理的土壤微生物生物量碳、氮含量分别比对照高58.9%～243.6%和55.9%～110.4%。相同处理中,干旱的水分条件下(40%田间持水量)微生物生物量要高于湿润的水分条件(70%田间持水量)。同时,添加0.5%和1.0%的生物质炭使土壤代谢熵分别降低2.4%和26.8%,微生物商减少了43.7%和31.7%。     

Cyanobacterial communities of rice straw left on the soil surface of a paddy field

To estimate diversity, seasonal variation, and phylogeny of the cyanobacterial communities in rice straw placed in nylon mesh bags and left on the soil surface of a paddy field, total DNA was extracted from straw, amplified by polymerase chain reaction targeting 16S rRNA genes of cyanobacteria, and the amplicons were separated by denaturing gradient gel electrophoresis (DGGE). These DGGE bands were sequenced. The paddy field was under flooded condition after transplanting of rice (Experiment 1) and under drained conditions after harvest (Experiment 2). The residual samples on the soil surface under upland conditions were collected just before spring plowing and were placed again on the soil surface after transplanting under flooded conditions. DGGE band patterns of cyanobacterial communities of rice straw were different under drained conditions, under flooded conditions when fresh rice straw samples were placed (Experiment 1), and under flooded conditions when residual rice straw samples were replaced (Experiment 2), indicating that the communities were influenced by both water regime of the paddy field and the degree of the rice straw decomposition. Sequence analysis of DGGE bands indicated that most of the cyanobacteria in rice straw on the soil surface in the paddy field were filamentous members belonging to Subsections III and IV. Filamentous cyanobacterial cells were observed in rice straw under flooded conditions by epifluorescence microscopy.     

稻田冬种绿肥对水稻产量和土壤肥力的影响

为探讨冬季种植绿肥作物改良土壤的生态作用, 以冬闲连作为对照, 通过连续8年的定位试验研究了冬种绿肥(紫云英、油菜和黑麦草)收获后翻压还田对后作水稻产量及土壤肥力的影响。结果表明: 连续8年冬种绿肥期间, 冬种绿肥各处理的水稻平均产量均高于冬闲对照, 但不同处理增产效果有所不同, 其中紫云英 早稻 晚稻处理增产效果最明显, 为10.48%, 其次是油菜 早稻 晚稻处理(7.31%), 黑麦草 早稻 晚稻处理的增产效果较差, 仅为5.76%。紫云英 早稻 晚稻处理的土壤pH和碱解氮含量最高, 与其他处理相比, pH增加0.58%~1.37%, 碱解氮增加6.59%~35.35%。黑麦草 早稻 晚稻处理的土壤有机质、有效磷、速效钾含量和C/N在各处理中最高, 分别较其他处理高2.99%~4.98%、19.25%~31.05%、16.97%~22.15%和0.97%~6.61%。相关性分析结果表明, 水稻产量与每穗颖花数、结实率、千粒重及土壤碱解氮、有效磷极显著相关(P<0.01), 与每穗粒数、有机质、速效钾显著相关(P<0.05), 而与穗长、有效穗数及土壤pH和C/N相关不显著; 水稻产量各构成要素与土壤养分之间的关系极为密切。综合来看, 稻田冬种绿肥有利于增加水稻产量和改善土壤肥力。     

Effect of lime and phosphorus on zinc uptake from four soils of Brazil

Abstract

Four soils from southern Brazil were treated with four levels each of lime and P and cropped with corn (Zea mays L.) in the greenhouse. Zinc deficiencies occurred at soil pH values of 6.3 or greater and independently of the rate of P application. Application of P alone did not induce Zn deficiency.     

Evaluation of soil quality parameters in a tropical paddy soil amended with rice residues and tree litters

Laboratory and greenhouse experiments were conducted to study the effects of applications of rice residue and Pongamia pinnata and Azadirachta indica leaf litters on biochemical properties (extraction yield of humus, composition of humus, microbial biomass carbon, activities of urease and acid phosphatase) of a lowland rice soil under flooded conditions. Bulk soil sample collected from the Mandya paddy fields was used for the green house trials and the laboratory incubation studies. The organic materials were added at three rates – zero, 25.0 g carbon kg⁻¹ (2.5% C) and 50.0 g carbon kg⁻¹ dry soil (5.0% C). Results showed that tree leaf litter and rice residue at 5.0% C rate decreased instantaneous decay constant (k), there by retarded the rate of C mineralization. Carbon contents of HA increased with the rate of C added. Study of delta–log K values and C contents of humic acids revealed that greatest molecular weight of HA was in the pongamia litter treatment, followed by neem litter and rice residue. Grain and straw yields of rice crop in the pot culture study were statistically correlated to the soil quality parameters. Neem and pongamia tree litter incorporation at 2.5% C could be considered for improving soil health and crop yields of rice under flooded conditions; however, application at higher rates significantly (P ≤ 0.05) lowered total dry matter production in rice, despite favorable soil health parameters such as humic yields, microbial biomass – C content and acid phosphatase and urease activity. Among different soil health parameters, microbial quotient was found to be more sensitive indicator of decline in soil quality.     

Methane emission and entrapment in flooded rice soils as affected by soil properties

Laboratory incubation experiments were conducted to study the effects of soil chemical and physical properties on CH₄ emission and entrapment in 16 selected soils with a pH range of 4.7–8.1, organic matter content of 0.72–2.38%, and soil texture from silt to clay. There was no significant correlation with CH₄ emission for most of the important soil properties, including soil aerobic pH (measured before anaerobic incubation), total Kjeldahl N, cation exchange capacity, especially soil organic matter, and soil water-soluble C, which were considered to be critical controlling factors of CH₄ emission. A lower CH₄ emission was observed in some soils with a higher organic matter content. Differences in soil Fe and Mn contents and their chemical forms contributed to the this observation. A significant correlation between the CH₄ emission and the soil organic C content was observed only after stratifying soils into subgroups according to the level of CH₄ emission in soils not amended with organic matter. The results also showed that the soil redox potential (Eh), anaerobic pH, anerobic pH, and biologically reducible Fe and Mn affected CH₄ emission significantly. Urea fertilization promoted CH₄ emission in some soils and inhibited it in others. This result appeared to be related to the original soil pH. CH₄ entrapment was positively correlated with soil clay content, indicating the importance of soil physical characteristics in reducing CH₄ emissions to the atmosphere.     

Ecological safe management of terraced rice paddy landscapes

Ecological safe management of rice paddy landscapes is in focus of a joint research project comprising five German working groups and Chinese partners. The project is aiming at characterizing the scale-depending structures and processes of agricultural landscape of terraced paddy fields in southeast China. The specific objectives were the enlightenment of the linkage between remote sensible information and the spatial distribution of soil features, as well as soil structural processes and their relation to vertical and lateral water losses and solute leaching.The experimental watershed is located in southeast China. The soils which either developed from quaternary clay or red sandstone exhibit a (man-made) layered structure with three hydraulic-functional horizons: puddled layer, plough pan and the (water unsaturated) subsoil.The analysis of soil texture and selected chemical parameters on the catenary and catchment scale confirmed that even in old terraced and thoroughly modified landscapes, the original structures (unaffected by man) of catenary soil property distributions persist. Thus, the application of co-regionalization techniques incorporating topographical attributes as explaining variables was found to be suitable to characterize soil property distributions on both the catenary and the catchment scale.On-site field scale investigations revealed that paddy soils exhibit a dynamic soil–water system which is driven by the mechanical seed bed preparation (puddling) on the one hand and drying and wetting cycles including ponded/flooded periods on the other. It was found that the hydraulic properties depend mainly on the duration of cultivation as a rice paddy. In contrast to earlier studies, we found that a further decrease in the saturated hydraulic conductivity of the plough pan may still occur after 20 years. Even in older rice paddies, however, water losses may be significant mainly because of ineffective functioning of the surrounding bunds.Pedon and aggregate investigations demonstrated the pronounced dual porosity nature of the paddy soils with a macropore network consisting of cracks and biopores penetrating both the plough pan and the bunds. The shrinkage potential of the puddle layer was higher in older paddy fields than in younger ones while it was vice versa for soil from the plough pan. Swelling and shrinkage affected also the living conditions for soil microorganisms especially after drainage when the habitable pore space was significantly reduced. Pore scale and micro-biological investigations revealed that drainage induced stress reduced micro-biodiversity and decreased abundances of soil inhabiting microorganisms.In addition to newly proposed management strategies with recurrent wetting and drying cycles, we suggest maintaining (saturated) equilibrium conditions over longer periods to reduce soil structural dynamics and the risks of water losses and chemical leaching involved with preferential flow.     

施肥结构对冷浸田土壤肥力及水稻生长的影响

冷浸田因长期受冷泉水浸渍,土体封闭,难以通气与氧化,土壤溶液Eh下降,有效养分低,水稻产量低。本研究通过田间小区试验和动态取样与室内测定,探求了单质化肥、稳定性肥、复合肥配施生鸡粪和熟鸡粪等施肥方式对冷浸田土壤肥力及水稻生长的影响。结果表明:与单质化肥处理比较,复合肥与熟鸡粪配施处理土壤松结态腐殖质占重组腐殖质的比例提高10.8%,紧结态腐殖质占重组腐殖质的比例降低15.5%,土壤有机质和活性有机质含量分别提高8.9%和4.0%,土壤阳离子交换量提高10.2%,早稻土壤细菌数和微生物活性分别提高390.0%和13.0%;同时土壤磷酸铝盐和磷酸钙盐含量分别提高40.0%和28.0%,且磷酸铝盐和磷酸钙盐占无机磷总量的比例提高,闭蓄态磷占无机磷总量的比例降低,促使土壤中难溶性磷向易溶性磷转化,提高土壤有效磷含量;最终早稻磷、钾吸收量分别提高14.0%和127.0%,早、晚稻产量分别增加11.0%和8.0%。由此得出,有机无机平衡施肥是适合于冷浸田土壤培肥、水稻增产的施肥方式。     

不同耕种年限红壤性水稻土理化性质的变化特征

以江西省余江县不同种植年限的红壤性水稻土为对象,研究了土壤有机质、pH、阳离子交换量(CEC)、游离氧化铁含量和氧化铁活化度随时间变化趋势;选择耕种7、22和80年的土壤剖面,研究了游离氧化铁和无定形氧化铁在剖面不同层次的分布。结果表明,耕层(0～20cm)土壤有机质含量随着水稻种植年限的增加而增加,淹水种稻导致土壤pH升高,但主要发生在种稻的前7年,7～80年间土壤pH变化不大。土壤CEC随着种植年限的增加而增加,在17年达到最大,然后随种稻时间的进一步增加而减小。土壤游离氧化铁含量随种稻时间呈下降趋势,但种稻后土壤氧化铁的活化度高于母土旱地红壤。对7年和80年水稻土,表层土壤游离氧化铁的含量低于底层土壤,说明铁在剖面中存在淋溶迁移。7年和22年水稻土表层土壤无定形氧化铁含量高于底层土壤,但对80年水稻土,土壤无定形氧化铁随采样深度的增加而增加。