Principal soil types (Great soil groups) in Japan

Classified into three types, zonal, intra-zonal, and azonal, Japanese soil type may be explained as follows (see “General map of principal soil types”).     

Effect of temperature during ripening on grain quality of rice

Temperature during grain ripening has been shown to affect amylose content and gelatinization temperature of rice starch (1–6). These studies demonstrated that high ambient temperature results in lower amylose content and higher gelatinization temperature of the starch. Rice starches obtained from rice grains that matured at lower temperature had higher iodine blue values and were more susceptible to alkali digestion than those that ripened at higher temperature.     

Mechanisms and processes of crust formation on artificial aggregates

Crust formation process initiates from aggregate disinategration occurred through the combined effects of inherent soil properties and external actions. Rainfall plays a major role in determining the moisture conditions of the soil surface and in triggering aggregate disintegration mainly through slaking and the impact off raindrops. To analyze the relations between rainfall characteristics and crust formation, three artificially granulated aggregates were exposed to natural rainfall events. The rainfall characteristics were expressed in terms of the distribution pattern of rainfall intensity, I _10min; mean weighted drop diameters, D _n; raindrop concentration, N _Dn,; rainfall energy, Et;and kinetic energy, KE; as well as conventionally used parameters, such as total amount and mean intensity of rainfall. The degree of crusting was evaluated in terms of the water permeability and morphological observation just after the rainfall treatment. Based on a comparison of the rainfall characteristics and degree of crusting, we confirmed the following relations. Rainfall characteristics at the onset of the event considerably influence the degree of crusting, i.e. initial rainfall with high I _10min; and large drop size promotes aggregate disintegration by slaking due to rapid wetting, whereas initial gentle rainfall prevents slaking by slow wetting and subsequent crusting. When initial rainfall is not saaficient for slaking but Beads to a weakening sf the aggregates, subsequent disintegration and crusting are promoted by impact together with the residual influence of slaking. Impact is a dominant factor for aggregate disintegration under wet conditions after initial rainfall which is so gentle that slaking never occurs. Responses of the soils under different natural rainfall conditions were almost consistent with the results under simulated rainfall reported in the previous papers (Tanaka et $1.1997: Soil Sci. Plant Nutr., 43, 99-107, 109-115). Crusting was not observed in the Fujino 1–3 soil gender any rainfall events. In the Wokuei 1–3 soil, characterized by a susceptibility to slaking and stability to impact, crusting was only formed under the rainfall with high I _{10 min} at the onset. For the Shimazu 1 soil, impact played a dominant role in crusting under any rainfall events, and a larger degree of crusting was found when the effects of impact and slaking were combined. The characteristics of rainfall monitored in this study may be within a normal range as natural rainfall in terms of the amount and the mean intensity, suggesting that crusting likely to occur if the aggregate stability of soils is Bower than or similar to that sf the Shimaza 1 and the Hokuei 1–3 soils.     

Dairy Cattle Manure Effects on Soil Quality: Porosity,Earthworms, Aggregates and Soil Organic Carbon Fractions

In the European Union, the maintenance of soil quality is a key point in agricultural policy. The effect of additions of dairy cattle (Bos taurus) manure (DCM) during a period of 11 years were evaluated in a soil under irrigated maize (Zea mays L.) monoculture. DCM was applied at sowing, at wet‐weight rates of 30 or 60 Mg ha⁻¹yr⁻¹ (30DCM or 60DCM). These were compared with a mineral‐N treatment (300 kg N ha⁻¹, MNF), applied at six to eight emerged leaves and with a control (no N, no manure). Treatments were distributed in a randomized block design. Factors analysed were stability against wetting stress disaggregation, porosity, soil organic carbon (SOC) fractions and earthworm abundance, studied eight months after the last manure application. The application rate of 30DCM increased aggregate stability and the light SOC fraction, but not the pore volume, nor the earthworm abundance, compared with MNF. The DCM rates did not result in unbalanced agronomic advantages versus MNF, as high yields (12–16 Mg ha⁻¹ yr⁻¹) were obtained. In Mediterranean environments, the use of DCM should be encouraged mainly because of its contribution to the light SOC fraction which protects dry macro‐aggregates from implosion (slaking) during the wetting process. Thus, in intensive agricultural systems, it protects soil from physical degradation. Copyright © 2016 John Wiley & Sons, Ltd.     

Changes in soil hydraulic conductivity, runoff, and soil loss due to irrigation with different types of saline–sodic water

Irrigation with saline–sodic water causes sodic conditions in the soil which reduces soil productivity. We evaluated the changes in a number of important indices related to soil structural stability when treated wastewater (TWW), albeit with higher loads of organic matter and suspended solids, was used instead of more saline–sodic irrigation water, under different degrees of aggregate slaking. We studied soil saturated hydraulic conductivity (HC) using disturbed samples packed in columns, and soil infiltration rate, runoff and erosion under simulated rainfall. Aggregate slaking was manipulated by wetting the samples prior to all tests at either a slow (1–2 mm h^− 1) or a fast (50 mm h^− 1) rate. Samples of a calcareous silty clay (Typic Calciorthids) from the Bet She'an Valley, Israel, were taken from plots irrigated for three years with either TWW, saline–sodic Jordan River water (JRW), or moderately saline–sodic spring water (SPW), and also from a non-cultivated area (control). With little or no aggregate slaking (use of slow wetting), higher HC values and lower amounts of total runoff and soil loss were measured compared to when more severe aggregate slaking was induced (use of fast wetting). The HC values for the TWW treatment were similar to, or lower than, those for the control and significantly higher than those for the JRW treatment. For the runoff and soil loss data, differences among the water quality treatments were, generally, more pronounced when aggregate slaking was substantially reduced, and were related to soil sodicity. Under the latter condition, runoff and soil loss from the TWW treatment were comparable with those from the control and significantly lower than those from the JRW treatment. Our results suggested that replacing saline–sodic irrigation water with TWW could have favorable effects on soil structural stability, especially under conditions where aggregate slaking can be reduced (e.g., in regions with low to moderate rain intensities; and/or use of low intensity irrigation systems).     

不同耕作措施对旱作农田土壤水稳性团聚体稳定性的影响

为了探明陇中黄土高原旱作农田土壤水稳性团聚体崩解机制,以连续进行15年的不同耕作措施长期定位试验为研究对象,利用LB湿筛法(快速湿润法、慢速湿润法和预湿润后扰动法)和传统湿筛法探索了传统耕作(T)、传统耕作+秸秆还田(TS)、免耕(NT)、免耕+秸秆覆盖(NTS)4种耕作措施对陇中黄土高原旱作农田土壤水稳性团聚体稳定性的影响及其破坏机制。结果表明:不同耕作措施下,4种湿筛法处理后,0.25 mm非水稳性团聚体含量排序为:传统湿筛法快速湿润法预湿润后扰动法慢速湿润法;4种湿筛法处理后,团聚体平均重量直径排序为:慢速湿润法预湿润后扰动法快速湿润法传统湿筛法;不同耕作措施下,土壤团聚体相对崩解指数高于相对机械破坏指数。不同湿筛法处理后,在0~5 cm和5~10 cm土层均以NTS的水稳性团聚体含量和平均重量直径最高,且NTS处理的平均重量直径显著(P≤5%)高于NT和T处理;而10~30 cm土层,TS处理的水稳性团聚体含量和平均重量直径最高,且显著高于T处理的平均重量直径,但与NTS处理的平均重量直径无显著差异。不同耕作措施下的团聚体崩解指数和机械破坏指数均以T处理最高,NT次之,NTS处理最低。秸秆对0~5cm、5~10 cm、10~30 cm土层的团聚体崩解指数和机械破坏指数的降低均具有显著效应,而免耕仅在0~5 cm土层具有显著效应。因此,该区水稳性团聚体分散主要是由于水分入渗而引起的,且快速湿润时的破坏最大;同时,NTS处理可有效提升土壤水稳性团聚体稳定性,更有利于该区农田水土保持。     

快速湿润过程中钾和钙离子浓度对土壤团聚体稳定性的影响

为探索土壤团聚体稳定性对电解质的响应情况,该文研究湖北省2种土地利用方式下(林地、耕地)的3种类型土壤(黄褐土、黄棕壤、棕红壤)团聚体,在不同浓度(0、0.005、0.01、0.02、0.05、0.08、0.10、0.20 mol/L)电解质(KNO_3、Ca(NO_3)_2)溶液中快速湿润时的稳定性和破碎过程。结果表明:1)浓度低于0.1 mol/L时,团聚体稳定性随电解质浓度增大而减小;2)团聚体稳定度AS随湿润时间呈双指数衰减,与纯水相比,棕红壤和林地黄褐土的破碎过程受电解质溶液影响尤为显著,黄褐土和耕地黄棕壤在电解质溶液中迅速全部破碎;3)初始阶段团聚体破碎能量与土壤粉粘比和有机质含量呈负相关,与铁铝氧化物含量呈正相关。总之,团聚体稳定性随电解质溶液浓度增大而减小,且相对于纯水,团聚体在电解质溶液中破碎更快。     

Modelling slaking sensitivity to assess the degradation potential of humid tropic soils under intense rainfall

In the humid tropics, soil erosion due to the impact of high‐intensity tropical rainfall is one of the important environmental problems. A quick assessment of slaking sensitivity of soils that are frequently subjected to the fast wetting of intense rainfall of the humid tropics is necessary for the selection of appropriate soil management practices to avoid soil structure deterioration that results in runoff, seal formation, erosion and eventual degradation. Unfortunately, field and laboratory measurements of slaking sensitivity are tedious, time consuming and expensive. Therefore, a slaking sensitivity ranking framework using readily available soil data, namely, clay content, organic matter content, exchangeable sodium percentage (ESP) and cation exchange capacity (CEC) determined to be important in slaking sensitivity and structural degradation under intense rainfall was developed. The ranking framework was subsequently used to classify 23 agriculturally important Trinidadian soils into slaking sensitivity classes for management recommendation. A simple mathematical model that provides a rapid assessment of slaking sensitivity was also developed using the soil data of 14 out of the 23 soils and subsequently tested on the remaining nine soils. Our results suggest that about 80 per cent or more of the soils are highly sensitive to slaking pressures, highly vulnerable to degradation and require management practices that reduce the rate of wetting and thus degradation of aggregates under intense rainfall. The developed model performed with a high degree of accuracy as the predicted values were in close agreement with measured values (r = 0·93). This suggests that the model gives a good indication of the structural degradation vulnerability of the soils studied under the conditions applied and criteria used. The model is, therefore, recommended for use in the tested humid tropical soils. However, more comprehensive testing is required on a broader range of soils prior to its more widespread application in other climatic conditions. Copyright © 2010 John Wiley & Sons, Ltd.     

Expevimental analysis of slaking characteristics of mudstone in different pH solutions

为了研究泥质岩在不同pH值溶液中的崩解特性,为酸雨地区泥质岩的利用提供理论依据和技术指导,选取阜新海州露天矿泥质岩为例,进行室内浸水崩解试验。对泥质岩在不同pH值溶液中的崩解现象、崩解物的颗粒含量和崩解比进行分析、利用X射线衍射(XRD)、荧光光谱分析,测试岩样矿物化学成分。试验得到以下结论：不同pH值溶液中崩解强度大小关系是：酸>碱>中性;随着循环的进行,泥质岩的崩解程度不断加深,崩解速度先增大后逐渐减小甚至消失;泥质岩中许多不能溶于水的矿物成分可以和酸发生化学反应生成可溶性盐类,是泥质岩在酸中崩解最剧烈的主要原因;考虑泥质岩所处环境pH值不同对工程建设有重要意义。