Rapid determination of lime requirement by mid‐infrared spectroscopy: A promising approach for precision agriculture

Mid‐infrared spectroscopy (MIRS) has proven to be a cost‐effective, high throughput measurement technique for soil analysis. After multivariate calibration mid‐infrared spectra can be used to predict various soil properties, some of which are related to lime requirement (LR). The objective of this study was to test the performance of MIRS for recommending variable rate liming on typical Central European soils in view of precision agriculture applications. In Germany, LR of arable topsoils is commonly derived from the parameters organic matter content (SOM), clay content, and soil pH (CaCl₂) as recommended by the Association of German Agricultural Analytical and Research Institutes (VDLUFA). We analysed a total of 458 samples from six locations across Germany, which all revealed large within‐field soil heterogeneity. Calcareous topsoils were observed at some positions of three locations (79 samples). To exclude such samples from LR determination, peak height at 2513 cm^?1 of the MIR spectrum was used for identification. Spectra‐based identification was accurate for carbonate contents > 0.5%. Subsequent LR derivation (LR_SPP) from MIRS‐PLSR predictions of SOM, clay, and pH (CaCl₂) for non‐calcareous soil samples using the VDLUFA look‐up tables was successful for all locations (R² = 0.54–0.82; RMSE = 857–1414 kg CaO ha^?1). Alternatively, we tested direct LR prediction (LR_DP) by MIRS‐PLSR and also achieved satisfactory performance (R² = 0.52–0.77; RMSE = 811–1420 kg CaO ha^?1; RPD = 1.44–2.08). Further improvement was achieved by refining the VDLUFA tables towards a stepless algorithm. It can be concluded that MIRS provides a promising approach for precise LR estimation on heterogeneous arable fields. Large sample numbers can be processed with low effort which is an essential prerequisite for variable rate liming in precision agriculture.     

Determination of organic and inorganic carbon, δ13C,and nitrogen in soils containing carbonates after acid fumigation with HCl

In carbonate‐containing soils a reliable determination of organic C requires a method that effectively separates organic and inorganic C without altering the organic matter. This study was conducted to determine whether HCl vapor completely removes carbonates even in dolomite‐rich soils and to what extent a widely used acid‐fumigation method has to be modified for humus‐rich soils. Furthermore, it was tested whether HCl fumigation alters organic‐C content. Since C and N parameters are often analyzed simultaneously we also tested the influence of acid‐vapor treatment on N content and on δ¹³C of soil organic matter. We applied fumigation with 37% HCl for 8 and 32 h using 9 carbonate‐containing soil samples. Inorganic C ranged from 7 to 124 and organic C from 9 to 267 g kg^–1. The maximum contents of dolomite and calcite were 940 and 640 g kg^–1, respectively. A time of 8 h was enough to completely remove all carbonates. Neither the content nor the δ¹³C of organic C were significantly affected by fumigation. In contrast, N contents were altered by acid treatment. Based on these results and on our experience in analyzing more than 1000 soil samples, a recommended procedure for acid fumigation of carbonate‐containing soils with a wide range of organic‐ and inorganic‐C contents was derived. Samples pretreated in this way can be analyzed reliably for their organic‐C content and δ¹³C. Furthermore, N and inorganic‐C contents can be determined with a quality sufficient for many purposes.     

煅烧对白云石治酸效果及其钙镁释放动力学特性的影响

针对中国土壤普遍酸化,而用石灰治理会导致土壤板结,用碱性工业废弃物治理又有二次污染风险等问题,该研究在低温煅烧工艺下,研究了白云石颗粒大小、煅烧时间对白云石碱度、微结构、钙镁释放动力学特征的影响,旨在为开发既能治酸改土又能供应钙镁养分的白云石煅烧工艺提供理论依据。研究提出了总碱度和短期累积碱度2个概念。结果表明:粒径从0.15到3 mm的白云石,经过1 h煅烧后,总碱度增加了78%、短期累积碱度提高了1 100倍。粒径为1～3 mm的煅烧白云石在煅烧1～3 h后钙镁的释放速率快慢的规律一致,以煅烧2 h后释放速率最快。钙、镁释放曲线可用Parabolic、一级动力学、Richards和Bertallanffy方程进行拟合。其中Bertallanffy修正方程最适于描述煅烧白云石CaO释放的规律;Richards和Bertallanffy修正方程适于定量描述MgO的释放规律。由此可见,白云石煅烧后具有较高治酸潜力(总碱度)又有较大的治酸强度(短期累积碱度),并且能促进钙镁的释放,钙镁供肥量可用Richards和Bertallanffy修正方程预测预报。就粒径1～3 mm的白云石而言,煅烧...     

白云石催化松木燃料棒水蒸气气化试验

以松木燃料棒为试验对象,水蒸气为气化剂,在反应器底部装载定量的白云石作为催化床,通过考察气相组分变化,以及焦油的傅里叶变换红外光谱变化,综合分析白云石催化随温度变化的规律。试验表明:煅烧后的白云石促进提高气化气中氢气含量,相比无催化剂添加,H_2体积分数在800℃时涨幅较大,由32.32%升高至40.11%;当温度大于850℃,由于白云石催化裂解焦油速率随温度加快,以及碳酸盐自身分解加剧,造成CO_2体积分数增大;白云石能够促使碳氢化合物向小分子H_2、CO_2和CO转化,且随温度升高而加剧。白云石促进脂肪烃的碳链断裂、芳香烃开环反应、脱羟反应、脱羧反应、三键断裂反应,以及羟基和醚链的氧化等,但羧基脱除速率随温度升高逐步大于羟基及醚氧化为羧基的速率,使羧基含量先增加后下降。     

Measurement of organic and inorganic carbon in dolomite‐containing samples

It is still open to question which method is the best for quantifying organic carbon (OC) and inorganic carbon (IC) in soils containing dolomite. The aims of this study were (1) to compare the accuracy of a novel thermal gradient (ThG), the classical calcimeter (CALC) and the loss‐on‐ignition (LOI) methods on a reference sample set with known proportions of OC present as soil organic matter (SOM) and IC present as dolomite and (2) to compare the results of the different methods on a set of soil samples with different dolomite and SOM contents. The CALC and LOI methods rely on separate quantification or removal of IC by acid or heat, whereas IC and OC can be quantified in a single run by the ThG analysis. The ThG method was the most accurate method for the reference sample set, especially when dolomite contents were high. On the soil sample set, the ThG and CALC methods performed equally well, but only when two outliers were eliminated. The LOI method was not satisfactory for either sample set. Overall, ThG was the most reliable method for measuring IC and OC in dolomite‐containing samples over a wide range of concentrations, but the more widely used CALC method was also acceptable.     

An examination of procedures for determining carbonates in soils and related materials

Abstract

A number of procedures were tested for determining carbonate‐C in soils and limestones, using a simple technique for digesting and collecting the CO₂, previously described by the author¹⁰. Some of the procedures appeared suitable for removing and quantifying carbonate‐C prior to the determination of organic‐C. Depending on the digestion solution and the length of treatment, between 0.25 and 0.68 % of the organic‐C in cultivated mineral soils was released as CO₂ during the digestion, and thus included in the figures for carbonate‐C.

The study includes furthermore, an examination of the effects of particle size and the length of the heating period on the rate of dissolution of calcite and dolomite. A semi‐quantitative EDTA extraction procedure is described for separation of these minerals in limestones.     

黔中白云岩石漠区小流域土地利用变化及生态效益

为明析灰质白云岩石漠区和砾质白云岩石漠区综合治理工程中植被恢复模式的治理效果,采用科研示范和工程治理相融合、遥感影像和实地调查相结合的方法,在黔中不同白云岩组石漠化小流域分析了相应研究区及不同林草恢复模式的生态效益变化。结果表明:(1)普定研究区属灰质白云岩石漠区,凯里研究区属砾质白云岩石漠区,2016年2个研究区农林地景观基质相似度较高,普定研究区石漠化趋势性较强。(2)2016—2020年,普定研究区和凯里研究区林地面积转入量>转出量、耕地面积转入量<转出量。植被覆盖率增加、土壤侵蚀模数降低和石漠化等级面积率降低,普定研究区综合治理生态效益显著。(3)普定研究区和凯里研究区植被覆盖率增加量、土壤侵蚀模数降低率和石漠化等级面积降低率呈生态修复模式>封山育林模式>草地畜牧业模式的变化趋势,生态修复模式和封山育林模式的生态效益呈普定研究区>凯里研究区的变化趋势。综上,具有相似景观背景的石漠化小流域经综合治理后,呈植被覆盖率增加、土壤侵蚀模数降低和石漠化等级面积率降低的趋势,石漠化治理效果呈生态修复模式>封山育林模式>草地畜牧业模式的变化趋势,灰质白云岩石漠区治理效果比砾质白云岩石漠区显著。     

贵阳市喀斯特白云岩区土地退化初步评价

通过大量典型样地调查数据,采用主成分分析法筛选出5个评价指标,用灰色关联基本理论建立退化指数模型,对贵阳市白云岩区土地退化进行初步评价,按照退化指数值将其土地退化程度分为4个等级,分别是轻度（O-0．20）、中度（0．20～0．4JD）、强度（O．4-0．65）和极强度（≥0．65）;59个评价单元有12个属于中度等级,47个属于强度等级,无轻度和极强度等级出现。评价显示,土地退化程度与地表植被有较好的相关性,贵阳市6个区（县）退化程度一致,具有典型的水蚀淋溶型侵蚀特征。     

生物质热解气化产物中焦油的催化裂解研究

采用东北杨木屑为原料,在固定床二级催化裂解反应器上,试验了不同产地白云石催化作用下的焦油催化裂解过程,并对裂解温度和催化剂类型、反应停留时间等参数对焦油转化效果和热解可燃气的影响进行了分析。实验结果表明:裂解温度越高、停留时间越长、焦油的裂解效果越好,裂解温度达到1 000℃时,焦油的催化裂解率达到98.99%,不同产地白云石的催化裂解效果是有明显差异的,陕西产白云石在裂解温度900℃时裂解率达到95.14%。决定白云石催化裂解效果优劣的最重要的因素是白云石煅烧处理后比表面积的大小,比表面积越大,催化效果越好。要想得到好的焦油裂解效果,须选择高比表面积的白云石。     

The use of carbonatite rock powder as a liming agent

Carbonatite rock powder, originating from the Lillebukt Alkaline Complex at Stjernøy in northern Norway, can potentially be used as a slow‐releasing lime and potassium (K) and magnesium (Mg) fertilizer due to a high concentration of the easily weathered minerals calcite (42%) and biotite (30%). However, the enrichment of barium (Ba) and strontium (Sr) may cause an undesired uptake to plants when carbonatite is applied to agroecosystems. A pot experiment was designed to investigate the liming and fertilization effects of carbonatite and the potential mobilization of Ba and Sr compared to a dolomite lime commonly used in Norwegian agriculture. These liming agents were mixed with a sandy soil applied to different amounts of peat, and the uptake of Ba, Sr, calcium (Ca), Mg, and K by Festuca arundinácea Schreb. Kora (tall fescue) and Trifolium repens L. Milkanova (white clover) was evaluated. The liming agents were generally incapable of buffering the acidifying effect from increased applications of peat, while the plant dry mass was unaffected. Compared to pots given dolomite and soluble K, the availability of K from carbonatite to plants was equally high or higher, and no difference in the K:(Ca + Mg) ratio in plants was observed. Carbonatite was a significant source to plant Ba and Sr, and the uptake seemed to follow the Ca uptake. Addition of peat amplified the uptake of Ba, Sr, Ca, Mg, and K to plants, probably an effect of organic acid‐induced weathering of carbonatite. White clover took up Ba, Sr, and Ca more effectively than tall fescue, but the Ba and Sr concentrations in plants were relatively moderate compared to concentrations reported from field investigations.