Effects of applied urea and straw on various nitrogen fractions in two Chinese paddy soils with differing clay mineralogy

Combined application of synthetic nitrogen (N) fertilizers and organic materials can enhance soil quality, but little is known about the distribution of fertilizer N among different soil fractions after crop harvest. A pot experiment using ¹⁵N tracer was employed to address this question with three treatments, i.e., labeled urea-only (¹⁵NU), labeled urea + rice straw (¹⁵NU-S) and labeled rice straw + urea (¹⁵NS-U) applied to a Ferallic Cambisol (1:1 type soil clay mineral) and a Calcaric Fluvisol (2:1 clay mineral). Soil microbial biomass N, fixed ammonium (fixed NH₄⁺), exchangeable ammonium and soil organic N fractions by hydrolysis (6 N HCl) and their isotope abundance were determined after the rice harvest. Soil newly formed N in urea + straw (U-S) treatments (¹⁵NU-S, ¹⁵NS-U) was the sum of labeled urea-N in ¹⁵NU-S and labeled straw-N in ¹⁵NS-U. Compared with ¹⁵NU, U-S significantly (P < 0.05) increased the content and percentage of newly formed total soil N, acid insoluble N, amino acid N, and hydrolysable unknown N in both soils. In U-S treatment, straw amendment significantly (P < 0.05) reduced the content and percentage of newly formed fixed-NH₄⁺-N in Fluvisol as compared with ¹⁵NU treatments. Soil microbes contributed to the larger percentage of newly formed amino acid N (P < 0.01) in Cambisol as compared with Fluvisol. Fertilizer N in various soil fractions was therefore strongly affected by clay mineral type and microbes after the combined application of organic materials and synthetic N fertilizer.     

Availability of exchangeable and non-exchangeable K in Argentine soils with different mineralogy

There were two objectives in the study: 1) To determine exchangeable K and non-exchangeable K in soils with different potassium depletion levels and mineralogy as plant sources 2) To establish a relationship between the mineralogy vs exchangeable K (Ke) and non-exchangeable K (Kne) mobilization. An extraction experiment of soils was carried out in a greenhouse, with a total of 6 consecutive crops of ryegrass. Different supply rates for plant K were determined by Ke and Kne mobilization according to the soil intensity of use. The contribution of the Ke was greater and generated higher amount of K uptake during maximum availability period (from 0 to the 1st harvest) than in the later period when soil K was already depleted. For this the initial exchangeable K and the illite concentration of soils accounted for almost 100% (R² = 0.981 P=0.01) of the K taken up by ryegrass. For the following period (from the 2nd harvest to the 6th), Kne forms became more important. Plant K supply was not only a result of initial exchangeable K and illite concentration but presumably also of primary K-bearing minerals.     

水耕年限对黄棕壤发育的水稻土的表面化学性质的影响

利用采自江苏省农业科学院果园的旱地黄棕壤(对照)和由黄棕壤发育水耕20年和60年的水稻土,研究了土壤黏粒和粉粒的矿物组成,胶体和土体的化学性质随水耕年限的变化.粉粒的X-射线衍射图谱表明,3种供试土壤发育母质相似,胶体的矿物组成随水耕年限的变化不大.动电电位和表面负电荷的测定结果也表明,胶体表面化学性质未发生明显变化.随水耕年限增加,土壤黏粒含量降低,导致土体性质发生明显变化,土壤CEC和结构电荷量随水耕年限增加显著减少.     

Clay mineralogy and some chemical properties of Ap horizons of Ando soils used for paddy rice in Japan

The clay mineralogy of the Ap horizons of Ando soils in Japanese paddies was determined by a combination of methods and compared with that of Ando soils of uplands. Six of 13 paddy soil samples contained allophane and imogolite and none contained gibbsite, whereas parallel figures were 15 and 7 for 22 upland soil samples. Substantial numbers of diatoms were found in 5 paddy and 1 paddy-converted upland soil samples. The lack of gibbsite was related to the stage of soil formation rather than the paddy condition, whereas the presence of diatoms was related to both. Regarding layer silicates, there was no particular difference between the paddy and upland soil samples but one unidentified mineral with unique morphology and infrared spectrum was found in two paddy soil samples. There was no particular difference in phosphate adsorption between the paddy and upland soil samples.     

The extractable trace element content of acid soils and the influence of pH,organic matter and clay content

Abstract

The analysis of extractable trace elements was carried out on 434 soils using 0.1 N HC1 as the extractant for copper, manganese, iron, zinc and cobalt, 0.2 M ammonium oxalate at pH 3.0 for molybdenum and boiling water for boron. Results indicated that on the average from about 1 to 20 percent of the total element content of the soil uas extractable, the percentage varying with the element. Comparing the amount of extractable elements in the 0–15 cm and 15–30 cm layers indicated that only manganese, zinc and boron were significantly different.

Correlation studies showed that the pH significantly influenced the quantity of manganese, iron, zinc and boron extracted, while organic matter influenced copper, manganese, zinc, cobalt and boron and clay content the copper, manganese, iron, zinc, cobalt and boron.     

Swelling and mineralogy of smectites in paddy soils derived from marine alluvium,Japan

A low-swelling smectite exhibiting little intra-crystalline swelling even after saturation with Na was found in paddy soils derived from marine alluvium of Ariake Bay in Kyushu, Japan. The low-swelling smectite was considered to be beidellite-nontronite mineral containing as much as 10% Fe₂O₃. The low-swelling characteristics of this smectite are ascribed to the considerable substitution of Fe²⁺ for Al³⁺ in the ochtahedral layer which depresses the dissociation of unit layers of smectite. Transformation of low-swelling to high-swelling smectite is believed to be due to the oxidation of Fe²⁺ to Fe³⁺ in the octahedral layer.     

不同利用年限的红壤水稻土孔隙结构差异的图像分析

本文利用目前常用的土壤孔隙结构研究方法,获取了不同利用年限的红壤水稻土在风干状态下的孔隙结构图像,对孔隙结构特征的图像分析结果表明,随着利用年限的延续,孔隙结构逐渐改善,表现在孔隙面积逐渐增加,孔隙的孔径分布和孔隙在土体中的分布逐渐均匀,孔隙中大孔隙比重逐渐增大等方面。     

Studies on soils in the transferring cultivation of paddy and upland field

The amount of paddy crop is usually increased by converting a continuous paddy field into a transferring cultivation between paddy and upland crops. To study the reasons for this increase, in Hokkaido a soil survey was made at 16 localities, where both types of cultivation were practiced. The survey was carried out on four different types of soil; peaty soils at Horomui (18,3),* Kurisawa (36,2), Ebetsu (23,2), and Iwamisawa (20,2); muck soil at Fukagawa (35,4); clay soils at Naie (28,3), Takikawa (31,1), Toyonuma (25,3) Fūen (80,2) and Higashiasahikawa (22,3); and sandy soils at Higashikawa (22,3), Pippu (30,2), Shimokawa (28,1), Kucchan (20,3), Kunneppu (16,2) and Ebetsu (30,2).     

Potassium replenishment capacity of illitic soils at their minimal exchangeable K in relation to clay mineralogy

Potassium replenishment capacity of eight soil series with varying illite content of their clay fraction were studied at their minimal exchangeable K through green house experiments. Higher minimal K levels were found in soils with high initial K status. Maximum K uptake values were associated with high minimal K. The % illite also had a significant relationship with minimum K levels. Average daily rates of K replenishment of soils varied between 0.25 and 0.67 mg kg^?1 soil after reaching minimum K. The K replenishment rates were found highly correlated with minimal exchangeable K (0.96^**). Amount of clay failed to attain the level of significance with K replenishment rate. Soils with higher illite content in their clay showed high K replenishment rates.     

不同施肥方法对双季稻区水稻产量及氮素流失的影响

为保障粮食安全,减少稻田生态系统氮肥投入,提高氮肥利用率和减少氮素流失成为重要的农业和环境措施。本研究在位于湖南岳阳的农业部岳阳农业环境科学观测实验站开展为期1年的早稻、晚稻田间试验,比较了不施肥(T_1)、尿素常规施肥(T_2,施N 280 kg·hm~(-2)、P_2O_5 165 kg·hm~(-2)、K_2O 120 kg·hm~(-2))、控释肥常规施用(T_3,施N 230 kg·hm~(-2)、P_2O_5 165 kg·hm~(-2)、K_2O 120 kg·hm~(-2))、高量控释肥侧条施用(T_4,施N 230 kg·hm~(-2)、P_2O_5 138 kg·hm~(-2)、K_2O 120 kg·hm~(-2))、中量控释肥侧条施用(T5,施N 180 kg·hm~(-2)、P_2O_5 123 kg·hm~(-2)、K_2O 120kg·hm~(-2))及低量控释肥侧条施用(T6,施N 140 kg·hm~(-2)、P_2O_5 123 kg·hm~(-2)、K_2O 120 kg·hm~(-2))下氮肥的养分利用率、作物产量及氮素流失情况,以期为稻田氮素合理利用提供理论依据。研究结果表明,控释肥侧条施用可有效提高水稻的产量和氮肥利用率,减少面源流失。1)在减少稻田秧苗数量和氮肥施用量的条件下,T_4处理的水稻早晚稻产量分别比T_2处理增加13.17%和4.72%,与T_3处理相比亦分别增加7.27%和1.74%;2)侧条施肥处理有效降低了稻田氮素流失量,年氮流失量为0.466~0.673 kg×hm~(-2),比常规施肥处理降低地表径流氮流失量3.54%~29.36%;3)侧条施肥有效提高了氮肥利用率,T_4处理的氮肥利用率分别是T_2、T_3处理的1.70倍和1.22倍。因此,采用合适的施肥方式、配施适量控释氮肥可获得较高的产值和收益。高量控释肥侧条施用(T_4)是本研究区域最佳的施肥模式,对实现现代化农业生产的高产高效、资源节约和生态环境保护具有重要意义。     

Depositional seals in polyacrylamide-amended soils of varying clay mineralogy and texture

Purpose  

Depositional seals, formed when turbid waters infiltrate into soils, lead to a reduction in soil hydraulic conductivity (HC) and enhance runoff and soil erosion. Since clay size particles constitute a dominant proportion of depositional seals, soil texture and clay mineralogy play a significant role in determining the seal’s hydraulic characteristics. Presence of high molecular weight anionic polyacrylamide (PAM) in suspension flocculates fine sediments, and therefore, its application to the soil surface may modify the characteristics of the depositional seal. The impact of PAM on the latter is expected to be influenced by soil properties. The aim of this study was to elucidate the effects of PAM application on clay flocculation and the HC of depositional seals formed in four soils varying in texture (ranging from loamy sand to clay loam), and diverse proportions of clay mineral constituents (kaolinite, smectite, and vermiculite).     

Ammonium fixation by clay minerals in different layers of two paddy soils after flooding

 The influence of flooding and cellulose addition on the fixation of NH₄ ⁺ in different soil layers of two paddy soils from China (an entisol and an ultisol) was investigated. In both soils the content of total reducing substances (TRS) sharply increased during the first days after flooding and was highest in the anoxic layers. This increase, which was more pronounced in the entisol with the higher total C content, was accompanied by an increase in the concentration of non-exchangeable NH₄ ⁺ in both soils. The increase in mineralization after flooding, resulting in higher concentrations of exchangeable NH₄ ⁺, favoured the fixation of NH₄ ⁺. Although the application of cellulose resulted in higher TRS contents, the fixation of NH₄ ⁺ ions decreased, which may have been the result of microbiological N immobilization. Received: 29 April 1998     

Nitrogen mineralization in sub‐tropical paddy soils in relation to soil mineralogy,management, pH,carbon, nitrogen and iron contents

The nitrogen (N) requirement for paddy rice cultivated in Bangladesh amounts to approximately 80 kg N ha^?1. Lack of knowledge on N mineralization from soil organic matter leads farmers to meet this N requirement exclusively by costly mineral fertilizers, which have typically an efficiency of less than 40%. We assessed to what extent routinely analysed soil properties (N and carbon (C), texture, pH, extractable iron (Fe), aluminium (Al) and manganese (Mn), soil mineralogy and length of the annual inundation period) are able to predict net aerobic and anaerobic N mineralization in paddy soils. Both soil N and C correlated positively with the aerobic but not with the anaerobic N mineralization rate. Instead, relative anaerobic N mineralization showed a significant negative correlation with soil N content. We observed no significant influence of clay mineralogy on soil N mineralization. Aerobic but not anaerobic N mineralization increased with length of the annual inundation period while the proportion of the soil N that was mineralized during 120 days decreased. The large clay content of fields that are inundated for 9–10 months annually explains the co‐occurrence of large soil N contents and relatively small N mineralization rates in these fields. However, variation in texture did not explain variation in N mineralization of soils with inundation periods of 3–8 months. Instead, the anaerobic N mineralization correlated positively with Na pyrophosphate‐extractable Fe and negatively with pH (both at P < 0.01). Thus, pH and Fe content, rather than soil N content, clay mineralogy or texture, explained the substantial variation in anaerobic N mineralization of paddy soils in Bangladesh inundated for 3–8 months. It is not known if these relationships between net evolution of ammonium in soil and pH and Fe content are causal or indirect. Elucidation of these mechanisms would greatly further our comprehension of the biochemistry of the young ‘floodplain soils' with relatively low content of pedogenic oxides throughout southeast Asia.     

施氮和不同品种水稻对紫色水稻土钾素形态的影响

通过盆栽试验研究了施氮水平和不同品种水稻对四川盆地 3种典型紫色水稻土 5种钾形态的影响以及各种土壤钾形态对水稻钾素营养的贡献。结果表明 ,4个紫色水稻土供钾能力均属中下水平 ,全钾含量为 1.29%～2.62% ,其中矿物钾量平均占 96.82% ,速效钾和非交换性钾仅平均占 0.62%和 2.56% ,土壤供钾能力以中性紫色水稻土 石灰性紫色水稻土 酸性紫色水稻土。施氮 (N 0～ 150mg/kg)促进 4个紫色水稻土钾素的释放 ,提高水稻对非交换性钾和矿物钾的吸收利用 ,使矿物钾和非交换性钾的贡献占植株吸钾的 80.3% ,速效钾仅为 19.7%。中性紫色土供试 4个品种水稻的吸钾能力为开优 5号 汕优 63Ⅱ优 6078引佳 1号。施氮后4个品种水稻吸自非交换性钾和矿物钾量平均占植物吸钾量的 66.9% ,以施中氮 (N 150mg/kg)时植株吸钾量最高 ;而低氮或高氮水平都不利于植物对钾的吸收和土壤钾的释放     

温度对厌氧条件下不同pH水稻土氮素矿化的影响

氮矿化反应是土壤生态系统氮素循环的重要环节之一,决定了土壤氮素的可利用性。温度和pH是影响氮素矿化的重要环境因子。为研究厌氧条件下温度对不同pH水稻土氮素矿化的影响,本文以两种不同pH的水稻土为试验对象,在厌氧条件下,设置15℃、25℃、37℃和50℃4个温度,结合一级反应动力学方程式和有效积温式研究温度对土壤氮素矿化势、矿化速率、矿化程度和矿化势/全氮等矿化参数的影响。结果表明,两种土壤氮素矿化势均随着温度的升高而增大。在15~37℃范围内,两种土壤的矿化速率以及矿化程度均随着温度升高而增大,且同种温度下两土壤差异不显著。但在37~50℃范围内,随着温度的升高,两种pH土壤矿化速率以及矿化程度有增大也有减小,差异达1%显著水平。说明在高温范围内,不同pH土壤氮素矿化对温度的响应有很大差异。4个温度下,矿化势/全氮的值均随温度升高而增大,说明有机氮的品质随温度升高而提高。通过温度与矿化参数的相关性分析发现,在15~37℃范围内,各矿化参数与温度均呈正相关,且相关性极显著(P0.01);但37~50℃时,各矿化参数与温度相关性均较小,有的为负相关。本试验测定各培养周期的pH,发现在培养过程中,两种土壤pH波动不大,对土壤氮矿化的变化无影响。结果表明,厌氧条件下,尽管中、低温时不同pH水稻土氮素矿化对温度有相似的响应,但高温时不同pH土壤的氮素矿化显著不同。     

不同品种水稻土壤氨氧化细菌和氨氧化古菌群落结构组成

本研究通过提取土壤总DNA,利用特异引物进行PCR扩增和变性梯度凝胶电泳(DGGE),研究了不同品种水稻对稻田土壤氨氧化细菌和氨氧化古菌群落结构组成的影响.结果显示:稻田土壤具有丰富的氨氧化细菌和氨氧化古菌,且氨氧化古菌种类更多;不同品种水稻氨氧化细菌群落结构组成差异较大,其中以"天A/Km71"、"闽优1027"和"Km62/1027"3个品种相似性较高,且明显不同于其余3个品种:而氨氧化古菌群落结构组成在不同土层间表现出较大差异,其中以"天A/Km71"和"Km62/1027"的表土与根际土氨氧化古菌群落组成差异最大.研究表明不同水稻品种及土壤层次对氨氧化微生物群落结构组成具有一定影响,证明氨氧化微生物尤其是氨氧化古菌在稻田土壤生态系统中占有重要地位.     

Acidification and salinization of soils with different initial pH under greenhouse vegetable cultivation

Purpose

Field survey and sampling of vegetable greenhouse soils were conducted in Shouguang, Shandong Province, and Ningbo, Zhejiang Province to study the acidification and salinization characteristics of soils with different initial soil pH values and greenhouse cultivation time.

Materials and methods

The pH, electrical conductivity (EC), and ion composition of 74 composite soil samples were analyzed to evaluate their relation to soil acidification and salinization.

Results and discussion

Compared with their corresponding open-field soils, acidification and salinization of the greenhouse soils occurred in both 0-20 cm and 20-40 cm soil layers for the Shouguang and Ningbo soils. The soil pH decreased gradually at different rates as greenhouse cultivation time increased in the two surveyed regions, but the opposite trend was observed for soil EC. For the Shouguang soils, while the percentages of K⁺ and NO₃ ^? increased dramatically and Ca²⁺ and HCO₃ ^- decreased significantly after the soils were converted to greenhouse use, the correlation between soil pH and EC was significant, and the stepwise multiple regression analysis further showed that there was a significant correlation between pH and the percent of Ca²⁺ and HCO₃ ^?.

Conclusions

Soil acidification and salinization are common in greenhouse soils with different initial soil pH. Soil acidification in the Shouguang soils is a result of decrease in the percent of Ca²⁺, HCO₃ ^? due to over application of N and K fertilizers. Future research should be devoted to understanding the relevant mechanisms in greenhouse soils with lower initial soil pH values to assess if there are correlations between soil acidification and salinization under greenhouse cultivation.     

不同pH低磷土壤上水稻磷营养特性研究

通过盆栽试验,研究了不同磷效率水稻在不同pH土壤和不同磷处理水平下的磷营养特性。结果表明,低磷条件下,分蘖期耐低磷基因型850、1574和1079的磷吸收效率最高,孕穗期3个耐低磷品种磷吸收量和利用效率均较高;到成熟期1574品种的相对磷吸收量最高,达到65%,而相对磷利用效率则以1574和850品种最高。不同pH土壤上,分蘖期,各水稻品种在碱性土壤上磷吸收量和利用效率最低,相对磷吸收量和相对磷利用效率却最高;耐低磷基因型850、1574和1079的磷吸收量高于鄂晚13和敏感基因型99012。在孕穗期,各水稻品种在碱性土壤上的磷吸收量高于其它两种土壤,但相对磷利用效率却最低;耐低磷基因型850和1574在3种土壤上磷吸收量均最高,成熟期各水稻品种磷利用效率则明显高于孕穗期。可见,不同耐低磷基因型在不同pH土壤上表现出的磷营养特性不同,在耐低磷品种的筛选过程中应该考虑土壤pH因素,生产中应根据不同土壤酸度类型选择合适的品种。