Pulverizing Soils for Laboratory Analysis

Soil-testing laboratories utilize a range of grinder types to pulverize soils for laboratory analysis. This study was conducted to evaluate the effects of soil particle diameter and laboratory subsample size on analysis variability on nitrate, Bray 1 extractable phosphorus (P), extractable potassium (K), and soil organic matter (SOM). Four soils collected for the Agricultural Laboratory Proficiency Program were pulverized using four types of commercial grinders and analyzed for particle-size distribution, P, and K. In a second study, soils were pulverized to pass sieves of 2.0, 1.0, and 0.50 mm and subsampled for P, K, and SOM. Results of the commercial grinders indicate a range in mean particle diameters from 0.15 to 0.60 mm, with the lowest for the grinder utilizing a hammer mill design. Sieve-size analysis results indicate that the coarsest 2.0-mm fraction had the largest variability for all soil analyses evaluated. Analyte variability decreased with decreasing sieve size. Mean Bray P, K, and SOM-LOI (Loss-on-Ignition) mean concentrations were not statistically significantly different across the sieve sizes evaluated. Laboratory analysis variability for extractable Bray P increased as subsample size was reduced.     

平原沙土区不同林分类型下土壤有机碳库特征及其影响因子

目的 明晰不同林分类型下土壤有机碳库特征,以期为平原沙土区土壤碳库的提高和生态恢复提供理论依据。 方法 以江苏省平原沙土区丰县16年生杨树纯林、柳树纯林、杨柳混交林3种林分类型及相邻的撂荒地（对照）为对象,测定0～20、20～40、40～60、60～80、80～100 cm等5个土壤层次有机碳及活性组分和土壤酶活性,计算土壤碳库管理指数,并对土壤有机碳库特征和环境因子进行相关性分析。 结果 （1）3种林分类型及对照各土层有机碳含量和储量范围分别为1.03～5.88 g·kg−1和3.53～17.55 t·hm−2。与对照相比,0～100 cm土层,3种林分类型土壤有机碳含量增加了45.2%～82.2%。杨树纯林0～100 cm土层有机碳储量分别是柳树纯林、杨柳混交林和对照的1.23、1.24、1.83倍。（2）与对照相比,0～100 cm土层,3种林分类型的土壤易氧化有机碳、可溶性有机碳和微生物生物量碳含量分别提高了28.6%～48.0%、6.8%～9.7%和21.6%～33.4%。3种林分类型土壤碳库管理指数显著高于100%（P<0.05）。（3）林分类型显著影响土壤蔗糖酶和多酚氧化酶活性（P<0.05）,杨柳混交林0～100 cm土层多酚氧化酶活性显著高于杨树纯林和对照（P<0.05）。（4）相关性分析表明,土壤有机碳库特征受多酚氧化酶和β-葡萄糖苷酶活性显著影响,有机碳含量和储量、易氧化有机碳含量及碳库管理指数受蔗糖酶、过氧化物酶活性显著影响,微生物生物量碳受蔗糖酶活性显著影响。冗余分析表明,土壤碳氮比和细根生物量是土壤有机碳库特征的主要影响因素。 结论 平原沙土区营造人工林提高了土壤有机碳及活性组分和有机碳库稳定性,杨树纯林提高土壤有机碳储量效果最好。     

天然沸石改良苏打盐碱土吸附机理的探讨——Ⅰ.天然沸石对苏打盐碱土中主要盐分吸附规律的研究

本文是利用天然沸石对苏打盐碱土中存在的主要钠盐的吸附规律的研究,探讨了在不同时间的条件下,沸石对不同浓度的4种钠盐的吸附规律。     

八个竹种海涂引种试验报告

本文从土壤含盐量着手对八个竹种在引种成活率、新竹抽发数及其质量、角竹笋产量等方面进行了较系统的研究。结果表明,土壤盐分影响竹子的生长发育,此影响一般随含盐量的增加而增加;不同竹种对土壤盐分的适应能力不同;角竹笋能获得高产,单产达20800kg/ha。参照产地母竹和引种地新竹的生长情况,我们建议:海涂地区发展竹子时可选用角竹、桂竹和红竹。     

蒙古栎秋播种育苗技术的研究

自１９９３年起对本局大趟子苗圃进行了蒙古栎秋播育苗试验,并对蒙古栎从采种、种子调制、田间管理及起苗、留床、造林等环节上形成了一套完整的科学育苗方法,避免了春播育苗种子储藏和鼠害等一系列不利问题,研究探索了最佳播种量和最佳经营密度。     

夏玉米田作物蒸腾与棵间土壤蒸发模拟计算方法研究

本文依据能量平衡原理和质量守恒定律，提出了作物蒸腾与棵间土壤蒸发的估算模式，并对参数的估算做了详细的分析和讨论。最后利用试验区实测资料，通过田间水热耦合运移的数值模拟，对夏玉米田作物蒸腾棵间土壤蒸发模型及其模拟计算方法进行了验证，结果表明，本文提出的模型和模拟计算方法是有效而实用的。     

Lithic soils in the semi-arid region of Brazil: edaphic characterization and susceptibility to erosion

Soils(Leptosols or Epileptic Regosols)with lithic contact at a depth of 50 cm occupy almost 20%of the Brazilian semi-arid region.These lithic soils are susceptible to erosion due to faster saturation of water-holding capacity during rainfall,which accelerates the beginning of runoff.However,erosion traits of lithic soils in the semi-arid region of Brazil are less studied.The aim of this study was to characterize the soil and landscape attributes in areas with Neossolos Litólicos(Entisols)in the Caatinga biome to identify region of high susceptibility to erosion.Results showed that the soils were characterized by a sandy texture,soil structure with poor development and low content of organic carbon.These attributes increase susceptibility to erosion and reduce water storage capacity,especially in the states of Cearáand Sergipe.In these states,the content of rock fragments in the soil reaches 790 g/kg.High contents of silt and fine sand,high silt/clay ratio,predominance of Leptosols and strong rainfall erosivity were observed in Piauíand northwestern Ceará.A very high degree of water erosion was observed in the states of Pernambuco and Paraíba.Despite the low degree of erosion observed in the state of Bahia,it is highly susceptible to erosion due to the predominance of very shallow soils,rugged relief and high values of rainfall erosivity.Lower vulnerability was observed in the state of Alagoas because of its more smoothed relief,greater effective soil depth,thicker A horizon of soil and lower rainfall erosivity.In general,the characteristics that intensify the susceptibility to erosion in the Caatinga biome are those soil structures with poor development or without aggregation,low contents of organic carbon,high contents of silt and fine sand,high values of silt/clay ratio and rugged relief in some regions.This study collected information contributing to a better characterization of soils with lithic contact in the semi-arid region of Brazil.In addition,regions with a higher susceptibility to erosion were identified,revealing insights that could help develop strategies for environmental risk mitigation.     

关于农田尺度下土壤有机质的空间变异研究

本文将空间分析技术与地统计学方法相结合,以某流域的土壤白土及乌栅土的各三层 土壤样本开展了数据处理及系统化分析,深入探讨了土壤有机质含量所存在的空间变异特征, 望能为此领域研究有所帮助。     

耕作与施肥模式对渭北旱塬春玉米田蓄水保墒与玉米产量的影响

为揭示渭北旱塬春玉米田休闲期不同保护性耕作模式的蓄水保墒与增产增收效应,寻找适合渭北旱塬春玉米田水肥高效利用的耕作方式和施肥水平,于2013—2014年度在陕西省合阳县甘井镇春玉米田分别设置传统农户模式(翻耕+低肥,S1)、现有高效模式(免耕+高肥,S2)、创新高效模式(深松+平衡施肥,S3)等模式处理,研究各类耕作与施肥相结合保护性耕作模式下春玉米水分利用率、产量和经济效益差异。结果表明,创新模式S3和现有模式S2较农户模式S1播前增加了土壤贮水量;创新模式S3和现有模式S2处理在玉米主要生育期0~200 cm土层平均土壤贮水量分别比农户模式S1增加23.3 mm和18.1 mm,水分利用效率分别提高12.3%和10%,产量增加11.1%、9.2%。创新模式和现有模式均较农户模式能够增加土壤贮水量,提高水分利用效率,增加产量和经济效益,但创新模式蓄水保墒,增产增收优势明显,是适合渭北旱塬地区春玉米生产的水肥管理模式。