SW—Soil and Water: Construction of an Artificial Perched Watertable,Part 1: Air Permeability of Soils and Aspects of Soil Failure

The annual precipitation in the Three-river Plain of the People's Republic of China is only 500–600 mm and, besides, the rainfall is uneven; 60–70% of the annual precipitation occurs in July and August and there is almost no rainfall in the winter and spring seasons. Experiments were conducted to form the artificial perched watertable where the runoff caused in summer could preferably be held, by injecting high-pressure air into the soil. A horizontal soil cavity is required, so this paper deals with the determination of the air permeability of soils and the difference in the soil failure mechanisms due to the different air permeabilities.The results show that the air permeability k of 10 m² s⁻¹ MPa⁻¹ defined the situation between the fluidization and the V-shaped soil failure. When the value of k was from 10 to 0·1 m² s⁻¹ MPa⁻¹, the V-shaped soil failure took place and when it was less than 0·1 m² s⁻¹ MPa⁻¹, the soil cavity production took place. In order to produce the soil cavity in the B horizon of the planosol or Cg1 horizon of the meadow soil by air injection, the value of k for these soils should be less than 0·1 m² s⁻¹ MPa⁻¹ and the soil water content of these soils should be more than 30% d.b.     

覆盖模式及小麦根系对土壤微生物区系的影响

采用平皿分离培养法研究了5种栽培模式和小麦根系对土壤细菌、真菌及放线菌数量的影响。连续2年的定位测定结果表明:覆膜有利于土壤微生物数量增加。5种栽培模式中,小麦根区、根外土壤细菌数量均以覆膜模式下最高,分别为116.8×106cfu·g-1和86.7×106cfu·g-1;土壤真菌和放线菌数量均以垄沟覆膜(垄上覆膜、垄沟播种)模式下最高,分别为3.0×103cfu·g-1、1.4×103cfu·g-1和18.9×105cfu·g-1、19.7×105cfu·g-1。不同模式下小麦根系对土壤细菌和真菌数量影响较大,表现为根区高于根外;而根系对放线菌影响较小,只有补灌和覆膜2种模式为根区高于根外。多重比较结果显示,覆膜与其他模式之间细菌数量差异极显著,根区土壤细菌和真菌数量与根外存在显著差异。覆盖和根系能大幅度增加根区细菌、真菌和放线菌的数量,强化小麦根区根外细菌和真菌的数量差异。     

施肥措施对砂姜黑土水分入渗性能的影响

土壤水分入渗是降雨和灌溉水转变为土壤有效水的过程,是降水、地表水、土壤水和地下水相互作用的环节,是影响作物水分利用效率的重要因素。砂姜黑土黏粒含量高,具有楔型结构等障碍因子,水分入渗性能和持水能力较弱,作物水分利用效率低。改良土体结构是提高土壤入渗与持水能力,增加作物水分利用效率的重要途径。为研究施肥措施对砂姜黑土理化性质及水分入渗性能的影响,设置不施肥对照(CK)、测土配方施肥(PF)、测土配方施肥+秸秆还田(PF+JG)和测土配方施肥+粉煤灰(PF+FMH)4个试验处理,进行小麦-玉米田间轮作试验。研究了土壤容重、颗粒组成、总孔隙度和有机质含量的变化规律,分析了土壤水分入渗特征及其与土壤理化性质之间的关系。结果表明,PF+JG、PF+FMH处理使土壤有机质含量分别较CK和PF提高18.01%、8.92%和11.18%、2.61%,土壤容重分别降低12.90%、11.29%和4.48%、2.98%,土壤总孔隙度分别增加13.89%、5.87%和12.46%、4.56%,土壤水分累积入渗量分别增加98.08%、90.39%和34.64%、29.41%。PF+JG(1.18×10-4 m·s-1)和PF+FMH(1.13×10-4 m·s-1)处理的土壤水分稳定入渗速率分别是CK(5.92×10-5 m·s-1)和PF(8.73×10-5 m·s-1)的1.99倍、1.91倍和1.35倍、1.29倍。土壤水分稳定入渗速率与有机质及总孔隙度显著正相关(P0.01),与土壤容重呈显著负相关(P0.05)。该研究表明,秸秆还田和粉煤灰处理,可提高土壤有机质含量,降低土壤容重,增加土壤孔隙度,提高土壤水分稳渗速率,可为土壤水分入渗性能提升提供理论依据。     

Soil organic carbon stock for reclaimed minesoils in northeastern Ohio

Reclamation of disturbed soils is done with the primary objective of restoring the land for agronomic or forestry land use. Reclamation followed by sustainable management can restore the depleted soil organic carbon (SOC) stock over time. This study was designed to assess SOC stocks of reclaimed and undisturbed minesoils under different cropping systems in Dover Township, Tuscarawas County, Ohio (40°32·33′ N and 81°33·86′ W). Prior to reclamation, the soil was classified as Bethesda Soil Series (loamy‐skeletal, mixed, acid, mesic Typic Udorthent). The reclaimed and unmined sites were located side by side and were under forage (fescue—Festuca arundinacea Schreb. and alfa grass—Stipa tenacissima L.), and corn (Zea mays L.)—soybean (Glycine max (L.) Merr.) rotation. All fields were chisel plowed annually except unmined forage, and fertilized only when planted to corn. The manure was mostly applied on unmined fields planted to corn, and reclaimed fields planted to forage and corn. The variability in soil properties (i.e., soil bulk density, pH and soil organic carbon stock) ranged from moderate to low across all land uses in both reclaimed and unmined fields for 0–10 and 10–20 cm depths. The soil nitrogen stock ranged from low to moderate for unmined fields and moderate to high in some reclaimed fields. Soil pH was always less than 6·7 in both reclaimed and unmined fields. The mean soil bulk density was consistently lower in unmined (1·27 mg m⁻³ and 1·22 mg m⁻³) than reclaimed fields (1·39 mg m⁻³ and 1·34 mg m⁻³) planted to forage and corn, respectively. The SOC and total nitrogen (TN) concentrations were higher for reclaimed forage (33·30 g kg⁻¹; 3·23 g kg⁻¹) and cornfields (21·22 g kg⁻¹; 3·66 g kg⁻¹) than unmined forage (17·47 g kg⁻¹; 1·98 g kg⁻¹) and cornfield (17·70 g kg⁻¹; 2·76 g kg⁻¹). The SOC stocks in unmined soils did not differ among forage, corn or soybean fields but did so in reclaimed soils for 0–10 cm depth. The SOC stock for reclaimed forage (39·6 mg ha⁻¹ for 0–10 cm and 28·6 mg ha⁻¹ for 10–20 cm depths) and cornfields (28·3 mg ha⁻¹; 32·2 mg ha⁻¹) were higher than that for the unmined forage (22·7 mg ha⁻¹; 17·6 mg ha⁻¹) and corn (21·5 mg ha⁻¹; 26·8 mg ha⁻¹) fields for both depths. These results showed that the manure application increased SOC stocks in soil. Overall this study showed that if the reclamation is done properly, there is a large potential for SOC sequestration in reclaimed soils. Copyright © 2005 John Wiley & Sons, Ltd.     

稻-油轮作农田油菜生长季土壤呼吸作用及其影响因素分析

本文以西南地区稻-油轮作农田为研究对象,于2009年11月—2010年4月油菜生长期间采用静态暗箱法进行了土壤呼吸速率的观测,通过选择植株生长处、株间及行间3个样点研究土壤呼吸速率的时间变化及空间异质性,综合分析了土壤温度、土壤湿度、根系生物量、土壤有机碳以及C/N对土壤呼吸作用的影响。结果表明,油菜季土壤呼吸速率的日变化为单峰型,最大值出现在下午15:00。土壤呼吸速率的季节变化显著,呈现为先降低后升高的变化趋势,最低值出现在2010年1月。在植株尺度上,土壤呼吸作用存在明显的空间异质性,较高的土壤呼吸速率通常出现在靠近油菜植株的地方,表现为:植株生长处(336.71 mg·m-2·h-1)>株间(248.48 mg·m-2·h-1)>行间(141.77 mg·m-2·h-1)。土壤呼吸作用中根呼吸作用所占比例的季节变化呈单峰型,表现为生长初期小于生长中期和后期。在整个油菜生长季,根呼吸对土壤呼吸的贡献为25.78%~72.61%,平均为51.03%。土壤呼吸速率受多个环境因子的影响,与地表温度呈显著指数关系,与根系生物量呈显著线性关系,与土壤微生物生物量碳、易氧化有机碳及颗粒有机碳存在显著或极显著正相关。     

陕北多沙粗沙区乡村聚落土壤侵蚀及防治对策

通过定位观测和实地调查,对陕北多沙粗沙区已建乡村聚落的水力侵蚀,新建窑洞(房)过程中的弃土侵蚀及窑洞坍塌形成的侵蚀进行了研究。(1)观测期间(200406—200410),乡村聚落的平均水力侵蚀强度为5 434.3 t/km2,已达到强度级侵蚀,其中户间道路为7 348.0 t/km2,户间空地为6 873.2 t/km2,院落为2 081.7 t/km2;(2)新建1孔(间)窑洞或平房,平均弃土34.9 m3,相当于动土量的23.6%;延安以北丘陵区近20 a新建窑(房)平均每年弃土7.96×107m3,弃土年流失量约为5.17×106m3(7.76×106t/a);(3)在调查的102孔(间)塌窑所形成的松散堆积体中,平均每孔(间)窑(房)年流失泥沙46.3 m3。延安以北丘陵区因塌窑每年流失泥沙1.25×107m3(1.87×107t/a)。研究表明乡村聚落发展带来了较严重的土壤侵蚀,应加强研究与防治。     

恶臭假单胞菌P861(Gus)在油菜根部定殖的生态研究

本研究采用Gus 基因标记技术和常规方法跟踪考察了恶臭假单胞菌P861(Gus) 在缩影系统油菜根圈的定殖情况,以及缩影系统内土壤类型、土壤含水量对根部定殖的影响。土壤含水量分别为60% FC和75% FC时,P861(Gus) 在砂姜黑土中的定殖水平高于50% FC的,不但能散布至种子下8cm 以内的根段部位,且定殖水平分别为7.5×10²和2.8×10³cfu·g^-1。在灰潮土缩影中,P861(Gus) 在油菜根圈的定殖动态表现为在油菜播种后3 ～6 天,定殖密度可达最高水平(5.5×10⁶cfu·g^-1) ,然后急速下降,最后保持在一个相对稳定的较低水平(7.6×10²cfu·g^-1) 。P861(Gus) 在不同根段部位的定殖密度并无从上到下逐渐递减的规律。     

华北落叶松人工林碳汇功能的研究

以河北省木兰林管局14～59年生华北落叶松人工林为对象, 研究树木不同器官和林分不同组分水平的生物量与碳储量.结果表明, 华北落叶松树干碳储量在树木总储量中所占比重最大, 林地土壤和林木碳储量所占林分碳储量的比重最大.华北落叶松人工林林分碳密度为平均206.02 t·hm-2;林木碳密度为27.58 t·hm-2, 林地土壤碳密度为157.14 t·hm-2.以林木蓄积量(M)为基础的林木生物量(W)与碳储量(C)的拟合方程为:W =10.210 1+ 0.732 1M, C=5.188 4+0.373 6M;以林龄(A)和优势木平均高(H)为基础的林地土壤碳密度(Soc)拟合方程为:Soc=-24.635 6-5.606 1A+14.936 0H+0.439 8AH.在此基础上计算得出, 木兰林管局华北落叶松人工林总碳储量约为571.43×104 t, 其中林木生物量约150.00×104 t、碳储量约为76.49×104 t, 土壤碳储量约435.85×104 t.     

猪粪沼液防治辣椒疫病机理研究--沼液中铵与腐殖酸的作用

为探明猪粪沼液对作物土传病害的防治效果与机制,设纯化肥处理为对照,采用盆栽试验比较了猪粪沼液(ADP1)、外源添加铵沼液(ADP2)、除铵沼液(ADP3)、除腐殖酸沼液(ADP4)施用对辣椒疫病的防治效果。结果表明,猪粪沼液(ADP1)可以显著降低辣椒疫病的发病率(防效40.8%),去除沼液中的铵或腐殖酸后,对辣椒疫病的防治效果显著下降,其发病率与病原菌对照(PC)无显著差异。定量PCR检测结果表明,ADP2处理土壤疫霉数量最少(2.51×103copies.g 1),ADP3、ADP4沼液处理的辣椒根际疫霉数量较多,分别为8.19×103copies.g 1、1.38×104copies.g 1;土壤中辣椒疫霉菌的数量低于9.54×103copies.g 1时,辣椒疫病发病率与土壤中病原菌数量有较好的对应关系。不同沼液处理对细菌、真菌和放线菌数量的影响不同。病原菌存在下,ADP1处理的细菌、真菌、放线菌数量均最多,ADP2处理的真菌数量最少。孢子萌发试验表明,随着铵和腐殖酸处理浓度的增加,对疫霉菌游动孢子萌发的抑制率均逐渐增大。浓度为500 mg.L 1、1 000 mg.L 1、1 500 mg.L 1NH4+对疫霉菌孢子萌发的抑制率分别为77.6%、81.8%、95.4%。用浓度为25 mg(C).L 1、50 mg(C).L 1、75 mg(C).L 1、150mg(C).L 1的猪粪沼液腐殖酸处理疫霉菌游动孢子6 h,游动孢子萌发率分别比无菌水对照下降了27.8%、54.5%、70.0%、87.5%。研究表明铵和腐殖酸可能是沼液的主要抑菌因子,沼液作为土传病害抑制剂具有一定的应用前景。     

Effects of Single and Mixed Ion Solutions on Hydraulic and Physical Properties of a Clay Soil

In this work, the influence of solute concentration of two types of electrolyte solutions single-ion (Na) and mixed-ion (Na–Ca) systems on hydraulic and some physical properties of a clay soil was investigated. Saturated hydraulic conductivity (HC) declined noticeably using lower solute concentration in single ion system. The highest reduction in HC was observed at 250 mole_c m^?3 solute concentration. Application of high solute concentration of single-ion system reduced meanweight diameter (MWD) to less than half of the control treatment (0.16 mm compared with 0.33 mm). Resistance to penetrometer increased with decreasing solute concentration. In mixed-ion system the MWD was increased whereas the resistance to penetrometer was decreased. HC values ranged from 6.5?×?10^?4 to 9.0?×?10^?4 mm s^?1 in mixed ion system compared with 7.2?×?10^?4 to 13.0?×?10^?4 mm s^?1 in single-ion system. The improvement of some physical properties in mixed-ion solution treatment is attributed to the presence of calcium ion that usually acts as amendment to sodium-affected soil. Soil HC showed lower values at low solute concentrations.     

Tracer experiments on transfer of radio-iodine in the soil — rice plant system

In order to study the transfer of ¹²⁹I from soil into rice, tracer experiments have been carried out in the soil-rice plant system. The soil-plant transfer factors, which are defined as ‘concentrations of the nuclide in a plant organ’ divided by ‘concentrations of the nuclide in dry soil’, were 6.0 × 10^?3 for brown rice, 3.2 for the first leaf blade (flag leaf), 5.1 for the second leaf blade, 2.6 for stem, 1.4 for rachis and 9.0 for root on a dry weight basis at the time of harvest. The ratio of radio-iodine in brown rice to polished rice was about 1:0.3. The transfer factor of radio-iodine from soil to polished rice was estimated to be about 2 × 10^?3. It was observed that the concentration of radio-iodine in the soil solution increased with the plant growth. This was attributed to the reduced condition in the soil caused by the effects of root and/or micro-organisms. Release of I from rice plants into the air in an organic form was found. The chemical form of radio-iodine in the soil solution appeared to be iodide, and the radio-iodine in the plant tissue was found in a low molecular weight fraction by gel-filtration. The vertical distribution of radioiodine in the soil was also studied.     

Modelling Soil Detachment of Different Management Practices in the Red Soil Region of China

Soil erosion from cropland is a primary cause of soil degradation in the hilly red soil region of China. Soil characteristics and the resistance of soil to erosion agents can be improved with appropriate management practices. In this study, hydraulic flume experiments were conducted to investigate the effects of five management practices [manure fertilizer (PM), straw mulch cover (PC), peanut–orange intercropping (PO), peanut–radish rotation (PR) and traditional farrow peanut (PF)] on soil detachment. Based on the results, three conservation management practices (PC, PM and PO) increased the resistance of soil to concentrated flow erosion. The rill erodibility of different treatments was ranked as follows: PC (0·001 s m⁻¹) < PM (0·004 s m⁻¹) < PO (0·007 s m⁻¹) < PF (0·01 s m⁻¹) < PR (0·027 s m⁻¹). The rill erodibility was affected by soil organic content, aggregate stability and bulk density. The soil detachment rate was closely correlated with the flow discharge and slope gradient, and power functions for these two factors were developed to evaluate soil detachment rates. Additionally, the shear stress, stream power and unit stream power were compared when estimating the soil detachment rate. The power functions of stream power and shear stress were equivalent, and both are recommended to predict detachment rates. Local soil conservation can benefit from the results of this study with improved predictions of erosion on croplands in the red soil region of China. Copyright © 2016 John Wiley & Sons, Ltd.     

INORGANIC SOIL PHOSPHORUS

Sixteen soils and 4 soil preparations were cropped exhaustively with ryegrass in the glasshouse and monocalcium phosphate potentials (½pCa+pH₂PO₄=1) were measured after each of 6 consecutive harvests. The amounts of phosphorus (Q) removed from the soils by ryegrass accounted for 95·1–96·6 per cent of the variance in 1 for 3 soils and 2 soil preparations (P < 0·001), for 88·4–93·7 Per cent of the variance for 6 soils and 2 soil preparations (0·001 < P < 0·01), for 71·6–82·6 per cent of the variance for 3 soils (0·01 < P < 0·05) and for insignificant amounts of the variance for 4 soils. Values of ΔI/ΔQ ranged from 7 × 10^–4 to 431 × 10^–4½pCa+pH₂PO₄/ppm P removed from soil. ΔI/ΔQ tended to decrease (i.e. the soils were more buffered) with increasing clay contents and with increasing amounts of NaHCO₃-soluble P and to increase (i.e. the soils were less buffered) with increasing amounts of CaCO₃. Variations in organic C did not significantly affect ΔI/ΔQ. The following equation accounts for 81 per cent of the variance in ΔI/ΔQ for all soils except those in equilibrium with octacalcium phosphate: ΔI/ΔQ× (10⁴) = 225·9–4·17(% clay)+8·01(% CaCO₃)–1·38(ppm NaHCO₃-soluble P).     

Effects of Vegetation Stems on Hydraulics of Overland Flow Under Varying Water Discharges

Vegetation plays an important role in soil erosion control, but few studies have been performed to quantify the effects of vegetation stems on hydraulics of overland flow. Laboratory flume experiments were conducted to investigate the potential effects of vegetation stems on Reynolds number, Froude number, flow velocity and hydraulic resistance of silt‐laden overland flow. Cylinders with diameter D of 2·0, 3·2 and 4·0 × 10⁻² m were glued onto the flume bed to simulate the vegetation stems, and a bare slope was used as control. The flow discharge varied from 0·5 to 1·5 × 10⁻³ m³ s⁻¹ and slope gradient was 9°. Results showed that Reynolds number on vegetated slope was significantly higher than that on bare slope because of the effect of vegetation stems on effective flow width. All the flows were supercritical flow, but Froude number decreased as D increased, implying a decrease in runoff ability to carry sediment. The mean flow velocity also decreased with D, while the velocity profile became steeper, and no significant differences were found in surface flow velocities among longitudinal sections on all slopes. Darcy–Weisbach friction coefficient increased with D, implying that the energy consumption of overland flow on hydraulic resistance increased. Reynolds number was not a unique predictor of hydraulic roughness on vegetated slopes. The total resistance on vegetated slopes was partitioned into grain resistance and vegetation resistance, and vegetation resistance accounted for almost 80% of the total resistance and was the dominant roughness element. Further studies are needed to extend and apply the insights obtained under controlled conditions to actual overland flow conditions. Copyright © 2015 John Wiley & Sons, Ltd.     

秸秆还田方式和氮肥类型对黄淮海平原夏玉米土壤呼吸的影响

为了研究黄淮海平原不同秸秆还田方式和施氮类型对夏玉米农田生态系统土壤呼吸的影响,于2010年6—10月,采用LI-COR-6400-09土壤气室连接红外线气体分析仪(IRGA)对玉米农田行间掩埋秸秆区的土壤呼吸作用进行了连续测定。结果表明,常规施肥下,玉米生育期内秸秆行间掩埋处理(ISFR)的平均土壤呼吸速率显著高于秸秆移除(NSFR)和秸秆覆盖(SFR)处理(P<0.05)。秸秆行间掩埋配合施用化学氮肥处理中,配施50.4 kg(N).hm 2处理(ISF3)的平均土壤呼吸速率为(178.85±46.60)mg(C).m 2.h 1,显著高于配施33.6 kg(N).hm 2处理(ISF2)的(124.11±23.18)mg(C).m 2.h 1(P<0.05)。秸秆行间掩埋配合施用鸡粪处理中,鸡粪施用量为33.6kg(N).hm 2(ISOM2)处理的平均土壤呼吸速率为(208.08±31.54)mg(C).m 2.h 1,施用16.8 kg(N).hm 2(ISOM1)和50.4 kg(N).hm 2(ISOM3)处理的为(135.07±21.97)mg(C).m 2.h 1、(171.43±43.31)mg(C).m 2.h 1,相比ISOM2处理,ISOM1和ISOM3处理的平均土壤呼吸速率降低了35.09%和17.61%。ISOM2处理玉米季CO2排放累积量为499.39 g(C).m 2,显著高于ISF2处理的297.86 g(C).m 2。秸秆行间掩埋配合施用化学氮肥对土壤呼吸速率的影响小于配合施用鸡粪的影响,配合施用16%总氮的鸡粪,即33.6 kg(N).hm 2时C/N比最适宜土壤微生物的代谢活动。     

Thermal diffusivity of plowed leached meadow-chernozemic soils in the Adygeya Republic

Thermal diffusivity of the upper horizons of leached meadow-chernozemic soils varies in dependence on the soil water content within the following limits: 1.20–4.11 × 10⁻⁷ m²/s for the Ap horizon, 1.21–3.85 ×10⁻⁷ m²/s for the A1 horizon, and 1.35–3.73 × 10⁻⁷ m²/s for the A1B horizon. The relationships between the thermal diffusivity and the soil water content are described by S-shape curves with a long gently inclined segment within the range of water contents of <0.20 cm³/cm³, a distinct rise in thermal diffusivity within the water contents from 0.20 to 0.30–0.35 cm³/cm³, and a flattened or somewhat declining segment in the area with the high (>0.30–0.35 cm³/cm³) water contents. The thermal diffusivity of air-dried soil samples correlates with the physical clay (<0.01 mm) content. The Pearson correlation coefficient for these two variables equals −0.67 and is statistically significant at the significance level of 0.05. Regression equations allowing one to calculate the thermal diffusivity of the investigated soil horizons on the basis of data on the soil water content have been obtained.     

Reclamation and salt leaching efficiency for tile drained saline‐sodic soil using marginal quality water for irrigating rice and wheat crops

Due to increased population and urbanization, freshwater demand for domestic purposes has increased resulting in a smaller proportion for irrigation of crops. We carried out a 3‐year field experiment in the Indus Plains of Pakistan on salt‐affected soil (EC_e 15·67–23·96 dS m⁻¹, pH_s 8·35–8·93, SAR 70–120, infiltration rate 0·72–0·78 cm h⁻¹, ρ _b 1·70–1·80 Mg m⁻³) having tile drainage in place. The 3‐year cropping sequence consisted of rice (Oryza sativa L.) and wheat (Triticum aestivum L.) crops in rotation. These crops were irrigated with groundwater having electrical conductivity (EC) 2·7 dS m⁻¹, sodium adsorption ratio (SAR) 8·0 (mmol L⁻¹)^1/2 and residual sodium carbonate (RSC) 1·3 mmol_c L⁻¹. Treatments were: (1) irrigation with brackish water without amendment (control); (2) Sesbania (Sesbania aculeata) green manure each year before rice (SM); (3) applied gypsum at 100 per cent soil gypsum requirement (SGR) and (4) applied gypsum as in treatment 3 plus sesbania green manure each year (GSM). A decrease in soil salinity and sodicity and favourable infiltration rate and bulk density over pre‐experiment levels are recorded. GSM resulted in the largest decrease in soil salinity and sodicity. There was a positive relationship between crop yield and economic benefits and improvement in soil physical and chemical properties. On the basis of six crops, the greatest net benefit was obtained from GSM. Based on this long‐term study, combined use of gypsum at 100 per cent soil gypsum requirement along with sesbania each year is recommended for soil amelioration and crop production. Copyright © 2010 John Wiley & Sons, Ltd.     

PH—Postharvest Technology: Diffusive Drying Kinetics in Wheat,Part 2: applying the Simplified Analytical Solution to Experimental Data

Reanalysis of the drying background in wheat showed that analytical solutions may be employed in this grain to estimate diffusion coefficients by using the simplified equation for short times instead of the time-consuming series. Sixteen thin-layer drying curves of hard wheat were measured (airflow ≈ 0·3 kg m⁻²s⁻¹) covering four air temperatures (35–70°C) at each of four initial moisture content levels (0·189–0·269 decimal, d.b.). Experimental curves of the moisture ratio versus time grouped by initial moisture content showed the expected strong accelerating effect of temperature on drying rate. Besides, when the same curves were grouped by temperature, the moisture ratios corresponding to higher initial moisture contents fell, after some time, consistently faster, showing that the diffusion coefficient should increase somehow with water concentration. The short time simplified diffusive equation fitted each curve very well, with values of the coefficient of determination above 0·99. Values of the diffusion coefficient for the whole kernel ranged from 1·4×10⁻¹¹to 7·1×10⁻¹¹m⁻²s⁻¹, presenting the classical Arrhenius temperature dependency (activation energy ≈ 27·0 kJ mol⁻¹), but with a pre-exponential factor that depends linearly on initial moisture content. This diffusive kinetics is expected to be useful for fast and accurate dryer simulation.     

基于能值的青藏高原边缘区域农业生态系统可持续发展分析——以四川省阿坝藏族羌族自治州为例

运用能值理论对四川省阿坝州农业生态系统进行定量分析与评估.结果表明,1952～2005年期间,阿坝州农业生态系统总能值投入从1.126×1022 sej·a-1增加到1.661×1022 sej·a-1,总能值产出从5.002×1020 sej·a-1增加到1.383×1022 sej·a-1,生态功能潜力从54.08%下降到37.02%,人口基本承载力从19.94万人增加到31.51万人,能值自给率从74.58%下降到54.13%,能值投资率从34.0%上升到85.0%,能值密度从1.34×1011 sej·m-2上升到1.97×1011 sej·m-2,能值货币比率从4.93×1014 sej·$-1降低到1.81×1013 sej·$-1,环境负荷率从0.85上升到1.70,净能值产出率从0.18上升到1.82,可持续发展指数从0.20增加到1.07.研究结果表明,阿坝州农业生态系统生产效率不断提高,而生态旅游业对阿坝州农业生态系统的活力和发展潜力至关重要;阿坝州农业生态系统的工业辅助能投入不足,系统的发展建立在对自然资源消耗的基础上,有不可持续的危险.并以此为据,提出了促进阿坝州农业生态系统可持续发展的几点建议.