Characteristics of Soil Porosity and Changes of Soil Water Content in Eucalyptus Plantation

Objective] This study almed to investigate the characteristics of soiI total porosity （STP） and various factors affecting soiI water content （SWC） in eucalyptus pIantation （EP）, thereby providing references for soiI water utiIization in eucalyptus pIanting in the red soiI hiI y region of South China. [Method] In the same cIimatic region, soiI sampIes were coI ected from surface soiI Iayer （A）, iI uvial horizon （B） and parent material horizon （C） in the upper sIope, middIe sIope and Iower sIope of eucalyptus pIantation, native forest and pine forest, respectiveIy, to determine the soiI porosity and soiI water content and analyze changes and various infIuencing factors of soiI water content in horizontal and vertical direction. [Result] Average soiI porosity in eucalyptus pIantation, native forest and pine forest was 45.9%, 41.4%and 55.3%, respectiveIy; soiI water content in these three forest stands was 13.3%, 13.4% and 15.5%, respectiveIy. In addition, soiI water content in these three forest stands exhibited no significant differences （P＆gt;0.05） among different soiI profiIes and sIope positions, but soiI water content in surface soiI Iayer varied significantIy （P＆lt;0.05） among different forest stands; in the horizontal direction, soiI water content exerted an extremeIy significant positive correIation with total coverage. [Conclusion] Total coverage of canopy Iayer, herb and Iitter Iayer is one of the most critical fac-tors affecting the changes of soiI water content in surface soiI Iayer of forest stands.

Transient infiltration tests in pyroclastic soils with double porosity

Fallout volcanic deposits of SommaVesuvius(Campania,southern Italy),characterized by the presence of layers with contrasting textural and hydraulic properties,are frequently affected by shallow landslides during rainwater infiltration.The soils of the stratigraphic sequence present intraparticle pores,originated by the gases escaped during magma decompression in the volcanic conduit,thus are characterized by double porosity(i.e.,intraparticle and interparticle pores),which is expected to affect their hydraulic behaviour,and to play a key role in rainwater infiltration through layered deposits.To understand the effect of double porosity on the hydraulic behaviour of the involved soils,controlled experiments have been carried out in an infiltration column.The experimental apparatus is provided with newly designed non-invasive Time Domain Reflectometry(TDR)probes,not buried in the investigated soil layers so as to minimize disturbance to the flow,allowing water content measurement during vertical flow processes.Specifically,transient flow experiments are carried out through reconstituted specimens of black scoriae and grey pumices,both loose pyroclastic granular soils from fallout deposits of Somma-Vesuvius,featuring double porosity with different pore size distributions,that were estimated by X-ray tomography and Mercury Intrusion Porosimetry.The experimental results highlight the effects of the double porosity and clearly indicate the different behaviour of the two soils during wetting and drying processes,mainly related to the different dimensions of intraparticle pores.

Effect of Sprinkler and Border Irrigation on Topsoil Structure in Winter Wheat Field

A two-year experiment was carried out on the effect of sprinkler irrigation on the topsoil structure in a winter wheat field. A border-irrigated field was used as the control group. The total soil porosity, pore size distribution, pore shape distribution, soil cracks and soil compaction were measured. The sprinkler irrigation brought significant changes to the total soil porosity, capillary porosity, air-filled porosity and pore shape of topsoil layers in comparison with the border irrigation. The total porosity and air-filled porosity of the topsoil in the sprinkler irrigation were higher than those in the border irrigation. The changes in the air-filled and elongated pores were the main reasons for the changes in total porosity. The porosities of round and irregular pores in topsoil under sprinkler irrigation were lower than those under border irrigation. Sprinkler irrigation produced smaller soil cracks than border irrigation did, so sprinkler irrigation may restrain the development of macropore flow in comparison with border irrigation. The topsoil was looser under sprinkler irrigation than under border irrigation. According to the conditions of topsoil structure, it is preferable for crops to grow under sprinkler irrigation than under border irrigation.

A Porous Simulation Experiment of Protozoa Movement with Glass Bead

Protozoa can move due to their flagella, cilia or pseudopodia, and play an important role in the transformation and cycling of matter and energy in ecosystems. In this study, the glass beads with the diameters of 1. 0, 0.5, 0. 25 and 0.1 mm were used to simulate soil pores of 0. 292 - 0. 258, 0.155 - 0.116, 0.056 - 0.040 and 0.028 - 0.020 mm respectively. Three typical soil protozoa of Bodo edax, Colpoda cucullus and Amoeba proteus were examined for the relation of their movement to pores. It was found that the smallest protozoan of Bodo edax could be leached through all the pores. However, no more than 26% of the added protozoan was leached out of the column. The leached protozoa were decreased with the pore sizes and leaching duration. The bigger one of Colpoda cucullus was moved out from the column filled with the glass beads of > 0. 5 mm in diameter. Less than about 15% of the added protozoa were leached out of the column. The biggest one of Amoeba proteus could not leached out from any of the pores. It is evident that most of the protozoa remained in the column due to their occupation of the pores.

Effects of biochar amendments on soil water retention characteristics of red soil at south China

Biochar has been extensively used for the improvement of soil water retention.However,the effects of various biochars were not well determined.The objectives of this study were to investigate the effects of three biochars[biochars made from bamboo(Bambusaceae),rice straw(Oryza sativa),and tobacco stem(Nicotiana L.)]on soil physical properties and the water retention characteristics of red soil at southeast China.The air-dried soil samples were mixed with ratios of 2%,5%,and 10%(w w^(−1))BC(bamboo biochar),RC(rice straw biochar),and TC(tobacco biochar),respectively,and evaluated for changes in soil bulk density(BD),soil saturated water content,field capacity,capillary porosity and soil hygroscopic coefficient.The results showed that BD decreased significantly with the application of the three types of biochar,total soil porosity and capillary porosity increased with the increase of the biochar ratio.The soil hygroscopic coefficient,wilting moisture capacity,saturated water content,and field capacity were significantly affected by the application of the three types of biochar.Compared with the other two treatments,the BC showed the best effects on soil water characteristics.BC treatments with addition ratios of 2%,5%,and 10%significantly decreased BD by 6.55%,18.03%,and 36.07%,respectively.Moreover,saturated water content and field capacity were increased by BC.BC treatments significantly increased the readily available water by 32.65%,42.49%,and 50.01%,respectively.However,the increased non-readily available water induced by the high ratio of biochar addition was not easily utilized by plants.Our results suggested that the biochar amendment can improve soil structure,decrease soil BD,boost soil porosity and capillary porosity,and increase soil moisture constant,and 2-5% of BC was recommended in the field condition.

Experimental measurement of acoustically induced surface vibration with different soil conditions

Experimental measurement is performed to investigate the acoustically induced surface vibration with different soil conditions. Using the method of scanning detection and analyzing the three-dimensional （3D） char- acteristic diagram of surface vibration, the influence of soil properties, such as porosity and humidity, upon the signal of acoustically induced surface vibration is measured. The experimental results show that the surface vibration redu- ces with the decrease of soil porosity and reduces a little with the increase of soil humidity; and with a big plastic landmine buried, the surface vibration enhances signifi- cantly. It indicates that the signal of acoustically induced surface vibration mainly depends on soil porosity and mechanical effect of buried objects.

Soil Pore Characterization Using Free Software and a Portable Optical Microscope

Total porosity （TP）, determined by image analysis, pore type and pore size distribution were evaluated on impregnated soil blocks from an undisturbed Brazilian sandy loam soil using a digital portable optical microscope. The free software Image J （version 1.40g） was used for image analysis. Procedures for soil image collection and analysis were presented. The image analysis allowed the evaluation of pore sizes with diameters ranging from 20 to 〉 1 000 μm. The following types of pores were also obtained： rounded, elongated and intermediate. The results M[owed the characterization of the soil as moderately porous （TP = 21.6%）. Rounded, intermediate and elongated pores were responsible for 11.6%, 31.7% and 56.7% of TP. In relation to pore size 51.1% of TP was in the 100-500μm size class and a third of TP came from the pores larger than 500μm.

Study on Soil Moisture Distributing Characteristics of Artificial Forest in Mountainous Region

Physical characteristics of soil structure and soil moisture of five kinds of artificia! forests were researched in Shengquan Temple Forestry Farm, in the southern mountainous area of Jinan City, in order to offer scientific management and nurture of forest vegetation in mountainous area of North China. Results indicated that： （1） In these artificial forests researched, some indexes expressing soil pedonydrological physical character, such as soil density, porosity, infiltration rate, were much better than those in bare land, and these indexes Showed this order： mixed forest 〉 pure forest, Kalopanax pictus 〉 Koelreuteria paniculata 〉 Pistacia chinensis. （2） In dry and rainy seasons, with the increasing of soil depth, soil water content decreased in most parts of forest, and their extent of change was less than those in bare land. （3） With the increasing of soil depth, soil saturated water content decreased in all kinds of forests. Water storing capacity of surface soil layer was the best in the mixed forest, while differences were little in other forest. Water storing and adjusting capacity was good in the mixed forest, while water offering capacity had little discrepancy in all forests. Conclusions show that judging from water conservation and water use efficiency, mixed forest is better than pure forest, and in pure forest K. pictus is better than K. paniculata. Therefore, it is proposed that in the future, mixed forest should be fostered and managed firstly, the species being made up of K. pictus and P. chinensis. In the pure forest, K. pictus is much better than others. Nowadays K. paniculata, and P, chinensis, especially their soil surface vegetation and litter, should be protected. As to poor forest, closing hill for afforestation should be adopted. Poor forest have better be reconstructed to be mixed forest in available conditions.

Growing-season soil microbial respiration response to long-term no tillage and spring ridge tillage

No tillage(NT)and spring ridge tillage(SRT)are two common applications of conservation tillage.Although conservation tillage is known to exert major control over soil microbial respiration(SMR),the growing-season SMR response to these two applications remains elusive.In order to better understand the influence of conservation tillage practices,this experiment was conducted in an experimental field using NT and SRT for 17 years.In situ measurements of SMR,soil temperature and soil water content(SWC)were performed.Soil samples were collected to analyze soil porosity,soil microbial biomass(SMB)and soil enzymatic activities.Results show that the two conservation tillage systems had a significant difference(p<0.05)in terms of SMR;the SMR of NT was 14.7 mg∙C/m^(2)∙h higher than that of SRT.In terms of soil temperature and soil enzymatic activities,the two treatments were not significantly different(p>0.05).Despite SRT increasing the proportion of micro-porosities and meso-porosities,the soil macro-porosities for NT were 7.37%higher than that of SRT,which resulted in higher bacteria and fungi in NT.Owing to SRT damaged the hypha,which had disadvantage in soil microbe protection.Inversely,less soil disturbance was a unique advantage in NT,which was in favor of improving soil macro-pores and SWC.Redundancy analyses(RDA)showed SMR was positively correlated with soil macro-pores,SMB and SWC.Furthermore,the Pearson correlation test indicated that SMB and soil enzymatic activities did not have a significant correlation(p>0.05).This study results suggest that SRT is more conducive to carbon sequestration compared with NT in cropland.

Land husbandry:an agro-ecological approach to land use and management Part 2:Consideration of soil conditions

This paper,complementing the first part(Shaxson et al.,2014),sketches the outlines of an ecologically-based approach to better care of soils,within the overarching context of‘land husbandry’,contributing to more-effective conservation of soil and water.It suggests an up-dated paradigm which concentrates more on renewing and conserving the biologically-moderated spaces in the soil in the root-zone rather than on the solid soil-particles themselves.When read in sequence,the two papers offer contributions to better understanding of both the problems and the possibilities for solving the ongoing uncertainties of how best to repair damaged lands,to maintain and improve those areas already in use,and to safeguard the potentials of those as-yet-unopened areas which surely will be brought into production in the future,by the planning and executing of optimum strategies for assuring sustainability of their uses into the future.These two papers do not set out to challenge existing knowledge,but rather to suggest additions to,and alternative interpretations of,what may already be known.The conclusions suggest some important amplifications to any curriculum for the training and/or up-dating of people involved in those subject-areas which contribute to better land husbandry and more-effective conservation of soil and water,as well as to the buffering of soils’productive capacities against the possible adverse effects of climate change.