An applied bioassay with tropical soil analyses for clayey oxisol fertility improvement

Abstract

There is a need for improved methodology providing reliable yield response data for tropical soils that correlate with soil testing results. However, both root development and desirable soil microbial activities are usually repressed with the heavy clayey oxisols in small pot greenhouse experiments. Fertility of the ultisols and oxisols is governed by soil organic matter content and soil microbial transformations. These are not determined with soil test extraction procedures and must be established with actual measurement of the complex biological permutations involved. The objective of these studies was to develop bioassay procedures suitable for boil fertility investigations with a heavy, clayey oxisol (56% clay) of Jaiba, a tropical region of central Brazil.

Soil dilution to 5.6% clay content with sterile, coarse quartz sand resulted in an optimum rhizosphere for plant nutrient studies using 500 g bioassay cultures. Phosphorus was the first limiting plant nutrient. Both N and K produced yield increases when applied singly although the largest increases in corn dry matter resulted with NPK combinations. Available N, P and S were related to organic matter transformations with response to S attained after exhaustive cropping. Significant responses to Zn, B and Mo were not obtained in these studies. Practical value of this procedure results from attaining reliable plant growth response to levels and combinations of fertilizer treatments with small quantities of soil. These data are fundamental for interpretation of soil test results that are utilized for highly diverse ultisols and oxisols. Sound recommendations for improved soil management practices are essential for the small, provincial subsistence type farms having very limited resources within the extensive, underutilized neotropics of the world.     

Evaluation of Dolomite Phosphate Rock–N‐Viro Soil Mixtures for Growth of a Horticultural Crop in an Acidic Sandy Soil

Abstract

Most agricultural soils in the Indian River area, South Florida, are sandy with minimal holding capacity for moisture and nutrients. Phosphorus (P) leaching from these soils has been suspected of contributing to the eutrophication of surface waters in this region. Dolomite phosphate rock (DPR) and N‐viro soil are promising amendments to increase crop production and reduce P loss from sandy soils. Soil incubation and greenhouse pot experiments were conducted to examine the effects of Florida DPR–N‐viro soil mixtures on the growth of a horticultural crop in an acidic sandy soil and to generate information for developing a desired formula of soil amendments. Dolomite phosphate rock and N–viro soil application increased soil pH, electrical conductivity (EC), extractable P, calcium (Ca), and magnesium (Mg). N–viro soil had greater effect on soil pH, organic matter content, and microbial biomass than the DPR. Comparatively higher nitrification rates were found in the N–viro soil treatment than the DPR treatment. A systematic decrease in soil‐extractable P was found with increasing proportions of N‐viro soil from the combined amendments. Greenhouse study demonstrated that the application of DPR and N‐viro soil significantly improved dry‐matter yield and increased plant P, Ca, and Mg concentrations of radish (Raphanus sativus L.). Based on dry‐matter yield and plant N uptake, the combined amendments that contained 30% or 20% of DPR materials appear to be optimal but remain to be confirmed by field trials.     

Excessive Nitrogen Inputs in Intensive Greenhouse Cultivation May Influence Soil Microbial Biomass and Community Composition

Intensive greenhouse vegetable‐production systems commonly utilize excessive fertilizer inputs that are inconsistent with sustainable production and may affect soil quality. Soil samples were collected from 15 commercial greenhouses used for tomato production and from neighboring fields used for wheat cropping to determine the effects of intensive vegetable cultivation on soil microbial biomass and community structure. Soil total nitrogen (N) and organic‐matter contents were greater in the intensive greenhouse tomato soils than the open‐field wheat soils. Soil microbial carbon (C) contents were greater in the greenhouse soils, and soil microbial biomass N showed a similar trend but with high variation. The two cropping systems were not significantly different. Soil microbial biomass C was significantly correlated with both soil total N and soil organic matter, but the relationships among soil microbial biomass N, soil total N, and organic‐matter content were not significant. The Biolog substrate utilization potential of the soil microbial communities showed that greenhouse soils were significantly higher (by 14%) than wheat soils. Principal component (PC) analysis of soil microbial communities showed that the wheat sites were significantly correlated with PC1, whereas the greenhouse soils were variable. The results indicate that changes in soil microbiological properties may be useful indicators for the evaluation of soil degradation in intensive agricultural systems.     

冻融交替对农田氮磷淋溶影响的研究进展

农田施肥过量导致氮磷养分淋溶引发的水体污染问题日益突出,冻融交替是中高纬度、高海拔和部分温带地区的自然现象,对冻土区农田生态系统的土壤生物地球化学过程有重要影响。了解冻融交替如何影响土壤氮磷养分淋溶,对建立阻控养分淋溶的措施至关重要。本文对国内外已有的研究结果进行归纳和梳理,从土壤物理、化学和生物学角度阐述了冻融交替对农田土壤氮磷淋溶的作用机制和影响因素。冻融交替主要是通过以下几个方面影响养分淋溶:1)土壤水的相变对土壤颗粒、孔隙结构、微生物细胞的破坏作用;2)对土壤微生物群落组成、结构及其参与的养分循环的影响; 3)最终导致土壤对养分和水分固持能力、可淋溶养分的含量和形态以及淋溶通道的改变。此外,气候因素包括气温和积雪覆盖对冻融模式的影响以及土壤自身的性质决定着冻融期间养分淋溶损失程度。基于冻融对养分淋溶的影响机制,阐述了增施生物炭、种植覆盖作物、采用免耕秸秆覆盖等耕作方式在减缓养分淋溶方面的研究进展和潜在机制,为今后相关研究工作提供了理论依据。最后简要指出当前研究的不足之处,提出未来相关研究的方向。     

Tillage and amendment effects on soil carbon and nitrogen mineralization and phosphorus release

The influence of tillage and nutrient amendment management on nutrient cycling processes in soil have substantial implications for environmentally sound practices regarding their use. The effects of 2 years of tillage and soil amendment regimes on the concentrations of soil organic matter variables (carbon (C), nitrogen (N) and phosphorus (P)) and C and N mineralization and P release were determined for a Dothan fine-sandy loam soil in southeastern Alabama. Tillage systems investigated were strip (or conservation) and conventional tillage with various soil nutrient amendments that included no amendment, mineral fertilizer, and poultry waste (broiler litter). Surface soil (0–10 cm depth increment) organic matter variables were determined for all tillage/amendment combinations. Carbon and N mineralization and P release were determined on surface soils for each field treatment combination in a long-term laboratory incubation. Soil organic P concentration was 60% greater in soils that had been conventionally tilled, as compared with strip-tilled, both prior to and following laboratory incubation. Carbon and N mineralization results reflected the effects of prior tillage amendment regime, where soils maintained under strip-till/broiler litter mineralized the greatest amount of C and N. Determination of relative N mineralization indicated that strip tillage had promoted a more readily mineralizable pool of N (6.1%) than with conventional till (4.2%); broiler litter amendments had a larger labile N fraction (6.7%) than was found in soils receiving either mineral fertilizer (4.1%) or no amendment (4.7%). Tillage also affected P release measured during the incubation study, where approximately 20% more inorganic P was released from strip-tilled soils than from those maintained under conventional tillage. Greater P release was observed for amended soils as compared with soils where no amendment was applied. Results from this study indicate that relatively short-term tillage and amendment management can significantly impact C, N, and P transformations and transfers within soil organic matter of a southeastern US soil.     

陕北黄土丘陵沟壑区高速公路边坡不同生物防护模式的土壤特性—以铜（川）-黄（陵）-延（安）高速公路为例

以陕西省铜川-黄陵-延安高速公路（简称铜延高速公路）为例,选取不同防护模式（穴状整地植草模式、挂网喷播植草模式、骨架植草模式）下有代表性的18个边坡为研究对象,通过边坡土壤特性数据的处理分析,发现：1）铜延高速公路边坡干旱缺水,肥力匮乏,有机质和全氮处于极缺乏和缺乏等级,速效磷处于中等等级,平均含量为16．28mg／kg;2）土壤水分、土壤养分以及植被盖度均表现为阴坡〉阳坡,而土壤密度则是阳坡〉阴坡;土壤水分含量呈现下坡位〉上坡位〉中坡位规律,土壤养分含量呈现从上坡位到下坡位逐渐升高,有自上而下累积的趋势,植被盖度呈现明显的分层现象,表现为下坡位〉上坡位〉中坡位;3）3种护坡模式中,骨架植草模式涵养水分能力最强,其次是穴状整地植草模式,最后是挂网喷播植草模式;4）水分是黄土高原地区高速公路边坡防护成功与否的关键因子,另外施加有机肥和氮肥,保护和收集表层土,增施磷肥以及合理确定边坡坡度和斜面长对边坡的保水保肥性和稳定性意义重大。     

西藏高原日光温室菜地土壤碳、氮矿化特征研究

采用室内培养方法, 以西藏拉萨地区选取的草地、农田为对照, 测定并比较日光温室土壤碳、氮矿化特征, 揭示草地和粮田转变为日光温室菜地后土壤矿化演变过程, 为西藏高原设施菜地土壤管理提供科学依据。结果表明, 草地、农田、1年温室、5年温室土壤有机碳矿化速率均在培养前期(0~7 d)日均矿化量最快, 且草地土壤显著高于农田和5年温室土壤(P<0.05), 温室土壤间无差异(P>0.05); 在培养28 d后, 农田土壤有机碳矿化释放的CO₂-C累积量高于草地, 草地高于1年温室和5年温室, 但不同类型土壤碳矿化释放的CO₂-C累积量间差异不显著(P>0.05)。无论是草地、农田还是温室, 4种土壤氮矿化都主要发生在培养的前期(0~3 d), 之后随着培养时间的延长, 不同利用类型土壤氮素转化以氮素的固定为主; 至培养结束时, 草地、农田、1年温室、5年温室土壤无机氮含量分别为培养0 d的29.04%、75.94%、66.86%、65.70%, 说明草地土壤氮素矿化能力较农田和温室强, 而温室土壤氮素矿化能力随着温室利用年限的延长而不显著升高, 农田氮矿化能力最弱。方差分析表明, 土壤氮矿化能力因土壤类型而异但矿化过程不因土壤类型而存在差异。     

伊犁河谷不同造林模式土壤养分与酶活性的关系

[目的]研究伊犁河谷5种典型造林模式下土壤养分和酶活性空间特征,为伊犁河谷地区造林树种的搭配和布局提供依据。[方法]通过采样和室内测试分析,对0—20和20—40cm土壤的化学性质及酶活性等指标进行分析测定,并对其相关性进行研究。[结果]0—20的土层土壤酶活性更强,养分含量也更高;各模式土壤养分含量差异显著,榆树防护林土壤碱解氮和有效磷含量最高,全钾和有效钾处于较高水平,林草间作用材林土壤全氮、全磷和有机质含量最高,碱解氮也处于较高水平;土壤酶活性与土壤养分有一定的相关,其中脲酶与全磷、碱解氮、速效磷和有机质显著正相关,过氧化氢酶与全钾和速效钾呈显著正相关,与全氮、全磷、碱解氮和有机质呈显著负相关。[结论]土壤酶活性与土壤养分间关系紧密,并可较好表征土壤肥力水平,可广泛应用于森林土壤的肥力水平评价。     

Effect of organic matter on the distribution, extractability and uptake of cadmium in soils

Distribution and plant uptake of soil Cd as influenced by organic matter and soil type were investigated in a greenhouse experiment. Three soils (a sand, sandy loam and clay loam) were used. The rates of organic matter in its moist state added were 0,20,40, 80, 160 and 320 g kg^-1 of the air-dried soil on mass basis. Ryegrass (Lolium multörum L.) was used as a test crop. Soil Cd was analysed by a sequential extraction technique and by extraction with 1 M NH₄NO₃ and 0.005 M DTPA. The exchangeable fraction of Cd as determined by 1 M MgCl₂ in the sequential extraction procedure increased, whereas the Fe-Mn oxidebound fraction decreased, with increasing levels of organic matter addition in all three soils. The dry matter yields of ryegrass were not affected by the addition of organic matter, but the Cd concentrations in both cuts of ryegrass decreased with increasing amounts of organic matter added. The plant Cd was highly but negatively correlated to soil CEC. At any level of organic matter addition, the decrease in Cd concentration of ryegrass was in the order: sand > sandy loam > clay loam.     

A method for determining microbially available N and P in an organic soil

Summary A bioassay of microbially available soil N and P is described. It is based on the addition of glucose together with N or P to soil, followed by monitoring of the respiration rate. The addition of glucose + N resulted in an immediate increase in the soil respiration rate followed by a short period of exponential increase, reflecting the growth of microorganisms on the added substrate. The exponential phase levelled off, when lack of P prevented further growth of the soil microorganisms. The soil respiration rate then remained constant for several hours before decreasing, when glucose became limiting. The addition of glucose + P resulted in a lower plateau of the soil respiration rate, indicating that microbial growth was more limited by N than P in this forest soil (0.28 and 0.79 mg CO₂ g^-1 organic matter h^-1, respectively). Additions of the limiting nutrient resulted in a proportional increase in the constant level of the soil respiration rate. This was used to calculated the increase in the soil respiration rate per mg N (0.71 mg CO₂ h^-1) or mg P (4.6 mg CO₂ h^-1) added to this particular soil. Microbially available N was then calculated in two ways from the regression equation (0.15 or 0.40 mg g^-1 organic matter) and P (0.13 or 0.17 mg g^-1 organic matter). A comparison with 2 M KCl extraction showed that in nutrient-poor forest soils the microbially available N was 6.3 or 18.5 times higher than the KCl extractable N.     

阔叶幼林取代杉木林后的土壤肥力研究

研究了3种阔叶混交幼林的土壤肥力，并将其肥力特征与杉木幼林进行对比研究。3种林分的立地条件相似常绿阔叶混交林1由12种观赏树种组成，常绿阔叶混交林2由7种速生乡土阔叶树种组成，常绿阔叶混交林3由12种阔叶树种组成。结果表明，各林地的土壤呈强酸性。常绿阔叶混交林1的土壤有机质、全氮和有效磷含量居各林地之首，其余的养分含量也大于或近似于杉木林地；常绿阔叶混交林2的全磷、全钾、有效氮、有效钾含量在4种林分中最高，有机质、全氮和有效磷含量也较高，说明这两种阔叶混交林有效地改善了土壤养分状况。常绿阔叶混交林3的土壤有机质、全氮和有效氮含量大于杉木林地，但是全磷、全钾、有效磷、有效钾含量小于后者。常绿阔叶混交林地1和常绿阔叶混交林地2的细菌、真菌和放线菌数量大于杉木林地，脲酶、磷酸酶、过氧化氢酶活性也较高，表明这2种阔叶混交林显著地改善了林地肥力。     

Changes in Soil Properties under Two Different Management Systems in the Western Amazon

Upland soils in the Amazon basin are often highly weathered and therefore possess low plant-available nutrient contents. Soil fertility is principally maintained by geochemical, biochemical, and biogeochemical processes. Within these processes, the soil microbial biomass is responsible for many of the cycles and transformations of nutrients in soils. The aim of this work was to evaluate the changes in soil fertility, in the form of nitrogen (N) and microbial activity, as indicators of the dynamic of carbon (C) with two extractants [irradiation extraction (IE) and IRGA methods], N, and phosphorus (P) in an upland soil area containing a dystrophic Yellow Latosol (Xanthic Ferralsol) in the western Amazon (Brazil) with succession of two plant covers (citrus or pasture) and management. The study was carried out in two chronosequences: primary forest followed by citrus plantations and primary forest followed by pasture. The results showed that pasture has greater capacity to accumulate organic C and total N than either primary forest or citrus plantation. Removing forest to introduce pasture or citrus plantations influences the soil fertility and microbial biomass of C, N, and P in the soil. Under the edaphoclimatic conditions, the irradiation extraction and IRGA methods all proved efficient in determining the soil microbial C activity. In addition, regardless of the depth of soil, the predominant N form is ammonium (NH₄ ⁺).     

黄土高原刺槐林对土壤养分时空分布的影响

以不同树龄刺槐纯林林地和撂荒地作对比,研究了黄土高原刺槐人工林对土壤养分时空分布特征的影响。结果表明,刺槐林地土壤有机质、pH值、全氮、有效氮、有效磷、速效钾、交换性钙和交换性盐基总量随刺槐树龄增加无明确变化规律,土壤全磷和交换性镁含量则呈现波动性变化;刺槐林地土壤有机质、全氮、有效氮含量随土壤深度增加按幂函数衰减,有效磷含量有递减趋势,土壤全磷、速效钾、交换性钙、交换性镁和交换性盐基总量随土壤深度增加无明显变化规律,而土壤pH随深度呈波动性变化;与撂荒地相比,刺槐林地土壤有机质、全氮、有效氮、有效磷、速效钾、交换性钙、交换性镁含量及交换性盐基总量分别增加21.6%~96.8%,34.3%~160.1%,191.5%~238.4%,2.1%~24.1%,19.82%~92.71%,64.2%~80.0%,25.0%~46.5%和67.2%~89.5%,表明刺槐林对改善土壤养分状况具有重要作用。     

THE EFFECT OF SOIL FACTORS ON THE EXTRACTION OF SOIL ORGANIC MATTER BY ANHYDROUS FORMIC ACID

Twenty-five soils, having a wide range of organic matter contents, were extracted with anhydrous formic acid containing 10 per cent acetylacetone, and the extracted material precipitated in two fractions with diisopropyl ether. Precipitates comprised from 5.1 to 51.1 per cent of the original soil organic matter, the proportion extracted tending to be greatest from acid soils of fairly high organic matter content and least from neutral or slightly alkaline soils of low organic matter content. Soil clay content appeared to have no effect on the efficiency of organic matter extraction, but was the most important soil factor governing the proportion of the total soil-N extracted. Amounts of N extracted ranged from 10.2 to 57.8 per cent of the original soil N content, extraction efficiency being greatest with soils of low clay content and low pH. There was evidence to suggest that soil clay afforded some protection to N compounds against extraction. The results indicate that formic acid/acetylacetone is most effective with soils in which much of the organic matter is only partly humified.     

Variation of Water Retention in Various Soils of Kuwait

Soil properties varied in water retention; due to soil texture and organic matter content. Variations of texture in many soils are effected mostly to soil forming factors of parent materials of the soil; biological activities; climactic variation; and duration of soil reaction. While the organic matter contents are affected totally by the environmental conditions of the soils. Water holding capacity of different soils influences' plant growth and development in diverse soil characteristics of the world and determines soil productivity. Water resources for agricultural activities are limited, particularly in arid environment and soil water-holding capacity of arid soil is very low. Kuwait can be good example of arid environment with limited water resources for agriculture activities and possess soil of coarse texture with very low organic matter content (Anonymous, 1997). Agricultural development in Kuwait meets many problems for crop production and urban landscaping. Water resources are limited and the quality is deteriorating at the same time soil water holding capacity is very low. Enormous amount of water, particularly desalinated expensive water is wasted for agricultural activities. This paper will study various parts of Kuwaiti soils water holding capacity and develop water retention data for efficient water irrigation and improvement of plant growth.     

火力楠和红苞木幼林的土壤肥力研究

对选定的火力楠幼林和红苞木幼林的土壤物理性质、土壤养分特点、微生物和酶活性进行了对比研究.结果表明,火力楠林的土壤容重显著小于对照,土壤毛管孔隙和总孔隙的比例及土壤毛管持水量显著大于后者.红苞木林的土壤容重是火力楠林的115%,土壤毛管孔隙、总孔隙的比例及毛管持水量分别为后者85%,87%和76%,而二者的非毛管孔隙相近.2种林分的土壤有机质、全N、全K和水解N含量均显著大于对照,而全P、速效P和速效K含量显著小于后者.二者的土壤pH值相近,均呈强酸性.火力楠林的土壤有机质、全N、全P、全K、水解N、速效P和速效K含量分别为红苞木林的1.29,1.26,1.17,1.02,1.20,1.33和1.51倍.火力楠林的土壤细菌、真菌和放线菌数量及土壤脲酶、磷酸酶和过氧化氢酶活性分别为红苞木林的1.63,1.18,1.72,1.19,1.06和1.24倍;2种林分的3种微生物数量和3种酶活性显著大于对照.     

低山丘陵区不同坡位茶园土壤肥力特征研究

南方低山丘陵区是我国茶园的集中分布区域, 研究其土壤肥力状况是改善茶园土壤养分状况、实现茶叶安全高效生产和可持续发展的基础.选择川西茶区典型低山丘陵茶园, 通过野外调查与样带采样研究土壤养分性质, 利用主成分分析等多元统计方法定量化比较了不同坡位及对照间土壤肥力质量.结果表明: (1)茶园土壤中砂粒含量最高, 平均占总量的39.13%, 其次是黏粒, 粉粒含量居第3位;土壤pH低于4.5, 有机质和全氮含量较低, 速效氮含量较高, 速效磷缺乏, 速效钾变化不显著.与林地、撂荒地相比, 茶园土壤各粒级含量变化规律不明显.有机质和全氮除在下坡位略高于撂荒地外, 其他坡位均小于撂荒地和林地;速效养分变化规律不显著.(2)茶园土壤肥力沿坡面变化明显, 以上坡位为基准, 土壤肥力指数PI值为零, 中坡位PI值(-13.64%)低于上坡位PI值(0)和下坡位PI值(14.39%).(3)与撂荒地、林地相比, 茶园的土壤肥力综合指数QI值最低.茶园、撂荒地、林地的QI值分别为0.56、1.11和2.73.     

THE BASIC FACTORS WHICH DETERMINE INHERENT SOIL FERTILITY IN UGANDA

Soil samples collected from approximately 1700 fertilizer trials carried out around 62 centres in Uganda were analysed. Mean levels of total N. organic P and cation exchange capacity at the 60 centres which had non-volcanic soils were very closely related to mean organic matter levels and largely explained the strong correlation of indices of available N, P and base status with organic matter. The indices of available P and base status were additionally related to pH and the indices of available N and P were further negatively correlated with sunshine hours. Soil organic matter itself was closely related to the content of clay, silt and free Fe. with which it is presumed it forms a stable complex, whilst soil pH decreased with rainfall in excess of evaporation. Thus soil texture, rainfall and hours of sunshine are the basic factors which largely determine inherent soil fertility in Uganda.     

Erosional impacts on soil properties and corn yield on Alfisols in central Ohio

Accelerated soil erosion can impact upon agronomic productivity by reducing topsoil depth (TSD), decreasing plant available water capacity and creating nutrient imbalance in soil and within plant. Research information on soil‐specific cause – effect relationship is needed to develop management strategies for restoring productivity of eroded soils. Therefore, two field experiments were established on Alfisols in central Ohio to quantify erosion‐induced changes in soil properties and assess their effects on corn growth and yield. Experiment 1 involved studying the effects of past erosion on soil properties and corn yield on field runoff plots where soil was severely eroded and comparing it with that on adjacent slightly eroded soil. In addition, soil properties and corn grain yield in runoff plots were compared on side‐slopes with that on toe‐slopes or depositional sites. Experiment 2 involved relating corn growth and yield to topsoil depth on a sloping land. With recommended rates of fertilizer application, corn grain yield did not differ among erosional phases. Fertilizer application masked the adverse effects of erosion on corn yield. Corn grain yield on depositional sites was about 50 per cent more than that on side‐slope position. Corn plants on the side‐slope positions exhibited symptoms of nutrient deficiency, and the ear leaves contained significantly lower concentrations of P and Mg and higher concentrations of Mn and K than those grown on depositional sites. Corn grain yield in experiment 2 was positively correlated with the TSD. Soil in the depositional site contained significantly more sand and silt and less clay than that on the side‐slope position. There were also differences in soil properties among erosional phases. The soil organic carbon (SOC) content was 19\7 g kg⁻¹ in slightly eroded compared with 15\1 g kg⁻¹ in severely eroded sites. Aggregate stability and the mean weight diameter (MWD) were also significantly more in slightly eroded than severely eroded soils. Adverse effects of severe erosion on soil quality were related to reduction in soil water retention, and decrease in soil concentration of N and P, and increase in those of K, Ca and Mg. Severe erosion increased leaf nutrient contents of K, Mn and Fe and decreased those of Ca and Mg. Corn grain yield was positively correlated with aggregation, silt and soil N contents. It was also negatively correlated with leaf content of Fe. Copyright © 2000 John Wiley & Sons, Ltd.