Tillage-induced seasonal changes in soil physical properties affecting soil CO 2 evolution under intensive cropping

Drivers of difference in CO2 and CH4 emissions between rubber plantation and tropical rainforest soils

Changes in soil physical properties of two Alfisols and an Ultisol in southern Nigeria as affected by desurfacing to simulate varying levels of soil erosion were monitored for two consecutive seasons (3 and 7 months after exposure). These investigations were conducted at Ilora (Alfisol), Ikenne (Alfisol), and Onne (Ultisol) in southern Nigeria. All measurements were made on the top 5 cm of the undisturbed control and the desurfaced soils. Following topsoil removal some deleterious changes in soil physical properties occurred on the exposed subsoils. Seven months after removal of 10 cm of topsoil, bulk densities had increased from 1.37 to 1.45 Mg m −3 at Onne, 1.23 to 1.50 Mg m −3 at Ikenne, and 1.27 to 1.42 Mg m −3 at Ilora. These increased bulk densities were reflected in decreased total and macroporosities. Seven months after 10 cm of topsoil removal, total porosity was reduced from 48 to 45% at Onne, 52 to 43% at Ikenne, and 52 to 46% at Ilora. Available water‐holding capacities of the surface 5 cm of exposed subsoils following 5 cm of topsoil removal were reduced during 7 months by 61% at Onne, 23% at Ikenne, and 12% at Ilora. Corresponding reductions in saturated hydraulic conductivities of these soils were 75%, 65%, and 35% three months after exposure. Also reduced were the moisture retention at 0.01 MPa suction, and the clay contents of the exposed subsoils. Generally, the magnitude of these changes in physical properties was less for the undisturbed control than for the desurfaced soils. These results strengthen the argument that these structurally unstable soils of the tropics should be managed extremely carefully.

Defining tillage need for edible bean production under no-tillage: Classical and time series analyses

A method for assessing the impact of load on mechanical stability and on physical properties of soils

Soil carbon dioxide fluxes following tillage in semiarid Mediterranean agroecosystems

Conventional agriculture is the dominant contributor to negative environmental impacts such as the growth in global greenhouse gas (GHG) emissions, and the challenges are likely to increase with the increasing global food demand as well as the agricultural expansion. Agroforestry is a sustainable management practice with strong potential to provide ecosystem services and environmental benefits through increasing carbon sequestration, nutrient availability, water use efficiency and biodiversity, and reducing soil erosion and nitrogen losses. Therefore, the establishment of agroforestry practices offers an opportunity to reduce GHG emissions. Previous studies have showed the effects of agroforestry on soil nitrous oxide (N2O), carbon dioxide (CO2), and methane (CH4) fluxes in many parts of the world. In temperate Europe, the information on the GHG mitigation potential of agroforestry compared to cropland monoculture is still unclear. The present thesis consists of two studies, which was designed to explore whether the conversion of cropland monoculture to agroforestry systems reduces trace gases N2O, CO2, and CH4 emissions from the soil. The study was carried out at three sites varied with soil types in Germany. Each site had adjacent alley cropping agroforestry and cropland monoculture systems and the trees in agroforestry system were planted 1 to 11 years prior to this research. We measured soil N2O, CO2, and CH4 fluxes monthly using vented static chambers at the three sites from March 2018 to January 2020. On each day of gas sampling, soil temperature, water-filled pore space and extractable mineral nitrogen (N) were measured in the top 5 cm. The objective of our first study was to quantify the spatial-temporal dynamics of soil N2O fluxes from cropland agroforestry and monoculture systems, following different crop rotations and fertilization rates. The pattern of soil N2O fluxes were predominantly controlled by soil mineral N in both agroforestry and monoculture systems. The positive relationship between water-filled pore space with soil N2O fluxes during the cropping seasons, indicating soil moisture acts as a limiting factor under N-sufficient conditions. The entire agroforestry systems tended to reduce soil N2O emissions by 9% to 56% compared to monocultures, during the corn phase of the rotation that had typically high fertilization rates. The lowest soil N2O emissions in the unfertilized tree rows (occupied 20% of the agroforestry area) represent a potential for mitigating N2O emissions from croplands. The objective of our second study was to investigate the changes in soil CO2 and CH4 fluxes after conversion from cropland monoculture to alley cropping agroforestry systems. Our results showed that seasonal variations of soil CO2 and CH4 fluxes were strongly regulated by soil temperature and moisture, and the spatial variations were mainly controlled by texture. The establishment of agroforestry systems had no effect on reducing soil CO2 emissions, possibly because there was no significant difference in soil temperature between management systems. Annual soil CH4 uptake in the agroforestry systems was increased by up to 300% compared to monocultures, which may be related to the regulation of trees on soil moisture in agroforestry systems. The present research provides the first insight into the systematic comparison of soil N2O, CO2 and CH4 fluxes from cropland agroforestry and monoculture systems, and it provides a unique dataset for estimating the net balance of carbon emissions after conversion of cropland monoculture to alley cropping agroforestry system in temperate regions. Although soil CO2 emissions showed no differences between management systems, the total annual soil emissions of non-CO2 GHG from agroforestry systems were reduced by 0.22 Mg CO2 eq ha-1 compared to the monocultures. Considering the driving function of soil moisture and mineral N on soil GHG fluxes from cropland agroforestry and monoculture systems, our findings suggest that improved system management (e.g. optimal adjustments of the areal coverages between tree and crop rows) and optimized fertilizer input will enhance the potential of cropland agroforestry for mitigating N2O emissions and increasing CH4 uptake and C sequestration in the long run.

Moisture and soil texture effects on soil CO 2 efflux components in southeastern mixed pine forests

Abstract. The objective of this research was to secure the fundamental information in changes of soil physical properties as influenced by the compaction of root media during container filling. Three root media were formulated by blending peatmoss (PM) with expanded rice hull (PM + ERH, 8:2, v/v), carbonized rice hull (PM + CRH, 6:4) and ground and aged pine bark (PM + GAPB, 8:2). Based on the optimum bulk density, the amount of root media filled into 6.0, 7.5, 8.5, 10.5 and 12.5 cm were adjusted to 90, 100, 110, 120, and 130%, then the changes in total porosity (TP), container capacity (CC), and air-filled porosity (AFP) were measured. The TP decreased significantly as the packing amount of three root media were elevated in all sizes of container. The TP did not show significant differences among the root media in small sizes of containers, but showed significant differences when sizes of containers became larger. As packing amount of three root media were elevated, the CCs in all sizes of containers were decreased. The PM + CRH had the lowest CC among three root media in containers smaller than 8.5 cm, but had the highest CC in those larger than 10.5 cm. These results indicated that the decreases in CC were influenced by the sizes of containers as well as kinds of root media. The elevation of packing amount in three root media diminished significantly the AFP. The AFP in PM + GAPB medium was two times as high as those of PM + ERH or PM + CRH when equal packing densities were applied in all sizes of containers. As the container sizes became larger in three root media, the extents in decreasing of CC were distinct than those of AFP. Above results indicate that elevation in packing amount of three root media decreased significantly the TP, CC and AFP, but these were influenced differently by sizes of containers and kinds of root media. The results would be useful for expectation in the changes of physical properties in various sizes of containers filled with peatmoss based root media.

The effects of combined throughfall reduction and snow removal on soil physical properties across a drainage gradient in aspen forests of northern Minnesota, USA

Changes in soil physical properties and organic carbon status at the topsoil horizon of a vertisol of central India after 28 years of continuous cropping, fertilization and manuring

The shift toward conservation tillage systems has caused plant pathologists to reexamine the importance of tillage and residue management on plant disease development. When plant diseases are influenced by tillage, it is often difficult to determine the factors responsible for changes in disease incidence or severity. One of the components altered by changes in tillage practices is the soil physical environment. Changes in soil physical properties may affect plant diseases by influencing the survival or activity of the pathogen, host susceptibility, or the prevalence of other soil microorganisms. Research is reviewed which illustrate how changes in the soil physical environment influence pathogen activity and disease development. Examples are drawn from tillage research, as well as research addressing the relationship of soil physical factors to disease development. Soil physical factors included are soil water, aeration, compaction, porosity, and temperature. Increased soil water can reduce disease through reducing plant water stress. Reduced soil aeration or temperature or increased soil water or compaction can predispose the host to infection and disease development. High soil water can also increase disease through increasing motility of the pathogen or diffusion of host exudates. Pore size may limit activity or movement of the pathogen. Changes in soil physical factors also may limit disease by affecting microbial antagonism. A greater understanding of how soil physical factors affect disease incidence and severity and pathogen survival and activity are needed before we can predict how the adoption of a tillage system will influence disease.

长白山西坡岳桦林带的草本植物(以小叶章为代表)侵入了苔原带,形成了独特的植物入侵现象。在光谱及影像分析的基础上,结合GPS(Global Positional System)定位技术,并依据小叶章与牛皮杜鹃的光谱差异及其反演的NDVI (Normalized Difference Vegetation Index)植被指数,揭示小叶章侵入苔原带的过程;通过对不同侵入时间、强度的斑块进行群落调查及土壤测试,探究小叶章侵入苔原带的生态后果。结果显示小叶章侵入苔原带始于20世纪80年代后期,由低海拔向高海拔推进,进入21世纪后逐渐形成了稳定的以小叶章为优势物种的植物群落结构。目前,低海拔处的小叶章斑块经过多年扩张已连接成片,而高海拔处的斑块正处于扩张的初期阶段。从生物多样性变化可以看出,小叶章侵入苔原带导致植物群落多样性升高和物种数量的增加,苔原带原有的灌木数量明显减少,草本植物逐渐增多。植被的改变影响了土壤的理化性质,C/N比下降,土壤腐殖质含量和全氮含量下降,但速效氮和土壤持水能力上升,土壤养分的高效利用又进一步推动了小叶章的侵入。小叶章侵入苔原带已经造成了严重的生态后果。;In China, the alpine tundra of Changbai Mountain is one of only three areas in China with this type of rare alpine tundra. The vegetation has undergone significant change in recent decades. Herbaceous species from the ‘<em>Betula ermanii</em> zone’, represented by <em>Deyeuxia angustifolia</em>, have invaded the alpine tundra zone on Changbai Mountain. This incursion represents a unique phenomenon in the mountainous areas of China. We examined the incursion process of <em>D. angustifolia</em> using GPS (Global positional system) techniques based on spectral and image analysis. In the study area, GPS equipment was used to identify individual <em>D. angustifolia</em> patches. Spectral analysis, particularly the red edge bands, was conducted by comparing the hyperspectral data between the invasive D.<em> andustifolia</em> and the native species, <em>Rhododendron chrysanthum</em>. The spectral diversity of the invasive and native species' enabled us to compare their NDVI (Normalized Difference Vegetation Index), which was used to analyze within patch changes in vegetation. Landsat TM images from 1983, 1999, 2002, 2006 and 2008 were used to calculate the NDVI index. The results showed that the incursion of <em>D. angustifolia</em> began in the 1980s. Currently, <em>D. angustifolia</em>has successfully invaded this alpine landscape with the gradual trend following an altitudinal gradient. The incursion range has extended from relatively low elevations to higher elevations. Moreover, the inference is that <em>D. angustifolia</em> patches at lower elevations are interconnected forming relatively large patches. At higher elevations in the tundra landscape, these <em>D. angustifolia</em> patches were smaller and more scattered.We also investigated the ecological consequences of the <em>D. angustifolia</em> invasion using plant community surveys and soil tests. The <em>D. angustifolia</em> patches were defined as patches at different times of invasion, which consisted of three different invasive levels (low, medium and high levels of invasion). In the newly formed plant community <em>D. angustifolia</em> was the dominant species. While this invasion altered the native plant community structure and enhanced biodiversity, it altered some soil properties including both physical and chemical properties. Compared with the native plant community, dominated by <em>R. chrysanthum</em>, the invasive patches showed higher Shannon-Wiener diversity and species richness. Changes in abundance and evenness of the community suggested that <em>D. angustifolia</em> would occupy the most dominate position in that community. The change of community structure resulted in the reduction of shrubs and increased the number of herbaceous species. The change of vegetation directly or indirectly led to changes in soil properties. The progression of invasion resulted in a decrease in the carbon/nitrogen ratio, soil humus and total nitrogen. However, the available nitrogen and soil water content increased. The changes in soil nutrients were closely related to changes in physical soil properties, especially for soil water content. The increases in soil water content altered nitrogen fixation processes, microbial decomposition and nitrification. We propose that the efficient use of soil nutrients may promote further <em>D. angustifolia</em> invasion. Moreover, we suggest that a time lag occurs between changes in the vegetation and soil properties.The invasion of <em>D. angustifolia</em> on the alpine tundra ecosystem has and continues to have severe impacts.

Annual and seasonal variations in soil volatile organic compound concentrations in a Mediterranean shrubland and holm oak forest

Forest soil CO 2 fluxes as a function of understory removal and N-fixing species addition

Evaluation of CO 2 fluxes from an agricultural field using a process-based numerical model