Lower Soil Depths Research Articles

A study on the soil seed bank of Nyala area, south Darfur, Sudan

This research is an ecological study on the vegetation of Nyala area, South Darfur State, Sudan. The main objectives of this research is determination of soil seed bank of species in the study area. The collected plant species were identified checked via the aid of the herbarium of the Department of Botany, Faculty of Science, University of Khartoum. Twenty-seven plant species have been identified from the study of soil seed bank. The most dominant of these species were Euphorbia aegyptiaca, Dactyloctenium eagypticum, Eragrostis tenella, Corchorus trilocularis and Amaranthus graecizans. The number of dead seeds/m2 on the upper soil surface layer (0-5 cm) was 12150, while that of live seeds was 5560. The number of dead seeds/m2 for the lower soil depth (5-10 cm) was 9707 and that of live seeds was 3254 seeds/m2. Statistical analysis of the data of the soil seed bank showed that there were statistically significant differences between the number of dead and live seeds/m2 at the same soil depth and among different soil depths.

Understanding yield-limiting factors for sorghum in semi-arid sub-Saharan Africa: beyond soil nutrient deficiency

ABSTRACT Even in semi-arid regions of sub-Saharan Africa, low crop yields are often attributed to a lack of soil nutrients and limited use of chemical fertilizers. However, in areas where soils with low effective soil depth are common, water availability may be a more significant factor that limits crop production than a lack of soil nutrients. In Sudan Savanna, the effective soil depths of three dominant soils, namely Pisoplinthic Petric Plinthosols (PT-pt.px), Petric Plinthosols (PT-pt), and Ferric Lixisols (LX-fr), are < 30, 30–50, and ~ 100 cm, respectively. Consequently, a lack of soil water is anticipated for both Plinthosols types. This study investigated the limiting factor in sorghum cultivation for each dominant soil in Sudan Savanna by creating plots with and without irrigation and fertilization. The results indicated that neither rainfall nor irrigation significantly affected sorghum yield under unfertilized conditions in all soil types, suggesting that even in very shallow PT-pt.px, a lack of soil water was not the limiting factor under unfertilized conditions. However, under fertilized conditions, reduced rainfall significantly decreased sorghum yield in PT-pt and PT-pt.px. In conclusion, in addition to the lack of soil nutrients being the limiting factor in sorghum cultivation under unfertilized conditions, regardless of soil type, lack of soil water becomes a limiting factor in soils with an effective soil depth of < 50 cm (e.g., Plinthosols) under fertilized conditions. These findings underscore the importance of knowing the effective soil depth when developing efficient fertilizer application methods to achieve food security in semi-arid regions of sub-Saharan Africa.

Impact of Land Use Types on Soil Organic Carbon and Nitrogen Stocks: A Study from the Lal Bakaiya Watershed in Central Nepal

Understanding the role of soil carbon (C) dynamics and quantitative changes as affected by various land use patterns is very critical given the significance of carbon sequestration. In this context, the current study was conducted in the Lal Bakaiya watershed in Makawanpur District, Nepal, to assess the variation of soil organic carbon (SOC) and nitrogen (N) stocks in three different land use types, namely, natural forest, grassland, and cultivated land. Incremental soil depths method (i.e., 0–15 cm, 16–30 cm, and 31–45 cm) was applied to collect soil samples in bulk from each of the land use under the study to estimate SOC and N stocks in laboratory. A total of 90 soil samples were collected from three soil layers down the soil profile up to 45 cm for each land uses. The results show that both SOC and N contents decreased with soil depths; however, substantial amount of SOC and N stocks were reported in lower soil depths under land use with natural forest. Both SOC and N contents were found relatively higher at 0–15 cm depth in natural forest soil (1.40 ± 0.20% and 0.26 ± 0.04%) than those in grassland and cultivated land, respectively. The mean total SOC stock and N stock ranged from 46.3 ± 4.24 t ha−1 and 7.11 ± 1.86 t ha−1 in cultivated land to 62.05 ± 9.17 t ha−1 and 11.40 ± 1.92 t ha−1 in the land use with natural forest, respectively. Furthermore, the mean total carbon and nitrogen ratio (C/N ratio) of the soil was found to be higher in cultivated land (7.07 ± 1.93) than that in natural forest (5.75 ± 1.47) and grassland (5.62 ± 1.49), respectively. Two-way analysis of variance results showed that both land use type and soil depth have significantly ( p &lt; 0.05 ) affected the SOC and N stocks in the study. From the results, it is suggested that well-managed land use can contribute significantly in offsetting global carbon emission.

Forest carbon stock variation with altitude in bolale natural forest, Western Ethiopia

This study was initiated to assess forest carbon stock variation with altitude. A systematic sampling technique was used to select sample plots. A total of 36 (12 plots from each altitude class) square plots with size of 20 m × 20 m were obtained. Diameter at breast height (DBH) and height of individual trees of DBH > 5 cm were measured from all the selected sample plots. A total of 216 soil samples, 108 for analysis of soil organic carbon (SOC) fraction (% C), and 108 for bulk density determination (BD), were collected. Altitude had a significant effect on above and belowground tree biomass, and litter carbon stock, but not on deadwood, and soil organic carbon stock. The aboveground and belowground biomass and litter carbon were higher at lower altitudes, which were attributed to higher biomass production due to higher photosynthesis and higher net primary production. Soil organic carbon varied significantly with depth. A higher soil organic carbon stock was observed at the upper soil depth (0–10 cm). At lower soil depths, carbon stocks were smaller due to less plant residue and less biological activity in the deeper soil. In general, the study found that carbon density is high at lower altitudes and lower at higher altitudes. Therefore, altitude should be given due consideration for forest development and management for climate change mitigation. The result suggests that different governmental and nongovernmental organizations have to give due attention for forest conservation to reduce the CO2 emmission.

Legacy phosphorus in Alabama Hartsells soil after long-term amendment with broiler litter.

Numerous studies have investigated effects of long-term manure application on total phosphorus (P) and inorganic P (Pi ), but few have evaluated soil organic P (Po ). Little is known about crop management effects on Po in soils with varying minerology. In this study, sequential fractionation was used to characterize specific P forms after 25 years of broiler litter (BL) or ammonium nitrate (Con) applications to an Alabama Hartsells soil. Crops (corn [Zea mays L.], soybean [GlycineWilld.], and corn or soybean with a wheat [Triticum aestivum L.] cover crop) were under conventional tillage (CT) or no-tillage (NT). Regardless of crop, tillage, or fertilizer type, the proportion of extractable Pi was relatively stable at 21%-49% at 0-5cm and 25%-45% at 5-10cm. Extractable Pi ranged from 0.69 to 2.4mg g-1 . BL increased total extractable Pi (p≤0.001) at 0-5cm and 5-10cm. Total extractable P was influenced at 0-5cm (p≤0.006) by both tillage and fertilization type, but not at 5-10cm or at either depth in soybean plots. Long-term BL application increased total extractable soil P at 0-5cm. In corn systems, CT did not reduce P loading to topsoil or result in P leaching to lower soil depths, compared to NT. Soybean and soybean-wheat reduced P loading in BL plots, compared to corn and corn-wheat. Soil Po was classed in the order of monoesters >phytate and polyphosphates, where most was extractable with NaOH. BL increased extractable Po in all fractions. Care should be taken when applying BL to highly weathered soils to avoid legacy Po accumulation. Soybean rotations and cover crops could help remediate P-laden soils after repeated BL application.

Effect of Land Use Change on Soil Physico-Chemical Properties under Different Land Use System in Arsi Zone, Oromia Region, Ethiopia

The establishment of artificial plantation using Eucalyptus globules in Ethiopia is becoming economically important for improving the livelihoods of small holder farmers. The species are adapted to different soil depths with varied responses to soil physical and chemical properties that have an implication on the proper management of environmentally sensitive areas. However, the sources of variations of soil physical and chemical properties have not been well investigated and documented for most vertisol in Ethiopia. This study was designed to investigate soil physical and chemical properties variations under different land use systems of cropland, grazing land and trees covered area with Eucalyptus globulus plantation at Gusha Temela Kebele, Arsi Zone and Oromia, Ethiopia. A total of 48 composite soil samples with 4 replicates * 3 treatments * 2 sampling plots * 2 at soil depths of 0–10 and 10–20cm were used for laboratory analysis. Some of the soil physical and chemical properties were analyzed and interpreted including soil texture, bulk density), soil moisture content, pH, available phosphorus (available P), soil organic carbon, total nitrogen and carbon to nitrogen ratio (C/N ratio). The results showed that, except in a few cases, all considered soil properties showed significant differences with land use types and soil depths. Soil Bulk density (r=0.0002), soil moisture content (r&lt;0.0001), soil pH (r&lt;0.0001), available phosphorus (0.0002) and soil organic carbon (r&lt;0.0001) were significantly varied with land use types. Textural fractions of sand, silt and clay showed no significant difference with land use types and soil depths. Although not significant, the clay content was slightly higher under grazing land. On the other hand, soil parameters including bulk density, soil moisture content, pH, soil organic carbon and total nitrogen were higher under grazing land than in the rest land use types and significantly varied with respect to soil depths; greater in the lower soil depth except for soil organic carbon and total nitrogen which were higher in the upper soil depth. The textural fraction of clay across all land use types was higher in the lower depth than in the upper surface layer which could be due to the translocation of this fine particle from the upper soil layer to the lower one. Findings of the present study indicated that land use change has more effect on soil chemical than physical parameters that grazing land is more fertile than other land use types. It implies that management practices significantly influence soil chemical properties variations especially the soil organic carbon concentrations for better employment of land management practices through implementation of climate smart agriculture.

Simulation of the Nitrogen and Phosphorus Leaching Characteristics under Different Filter Materials of an Improved Subsurface Drainage

Leaching characteristics of filter materials of the improved subsurface drainage are very important for nitrogen and phosphorus loss. In this paper, the leaching characteristic of soil, sand, straw, and zeolite under different layouts were studied by HYDRUS-2D simulation based on calibration and validation according to laboratory data. Two scenarios were considered, including different soil and filter layouts, and mixed filter materials of straw and sand or zeolite. The results indicate that zeolite showed good adsorption characteristics of both ammonia nitrogen and phosphorus, while the straw’s adsorption characteristics were very different between ammonia nitrogen and phosphorus. Nitrogen and phosphorus concentrations of the outflow were mostly determined by the materials around the outlet. Compared with the cases of no lower soil, when the lower soil depth was 5 cm, the ammonia nitrogen concentrations under sand and straw decreased 54.5% and 96.3%, and the corresponding decreased phosphorus concentrations were 84.1% and 96.2%. In views of mixed filter with straw and the different layouts, that the ratio of straw and sand was 1:1, or the ratio of straw and zeolite was 2:1; at the same time, sand and zeolite should be set around the outlet, and may be better for ammonia nitrogen and total phosphorus concentrations reduction.

Variability of hydraulic conductivity and water repellency of soils with fire severity in pine forests and reforested areas under Mediterranean conditions

AbstractThe effects of fire on soil hydraulic conductivity (K) and soil water repellency (SWR) have been mainly studied by field experiments in forest areas burned by wildfires with a given severity, while the variability of K and SWR with the fire severities has been less investigated. To fill this gap, the changes in the K and SWR with fire severity and soil depth (1 and 5 cm below the ground surface) have been evaluated in two forest ecosystems (natural stand of pine and reforested areas) of Central Eastern Spain. A significant influence of the fire severity on the infiltration rates was found, and this influence was different between the natural stand of pine and the reforested areas. Compared to the unburned soils, the highest reduction of the K (80% to 90%) and SWR levels were found for the fires with low and intermediate severities at the soil surface. At the lower soil depth, the reduction of K and the SWR level due to fire were proportional to its severity. Moreover, the K of the soil surface layer was often higher compared to the water infiltration in the deeper layer. In the reforested areas, also low fire severities can noticeably reduce the surface K, despite the limited SWR, while the natural forests are less exposed to hydrophobicity in their surface soil layer. This study indicates the need to reduce the risk of flooding and erosion linked to a reduction in water infiltration and increase of soil repellency.

Carbon Stock Potential of Gara Gola Natural Vegetation in East Hararghe Zone, Eastern Ethiopia

This study was conducted at Gara Gola, in the Oromia regional state of Ethiopia, to examine the carbon sequestration potentials under three altitudinal gradients [i.e., Lower altitude (LA: 1500–1800 m.a.s.l.); Middle altitude (MA: 1801–2000 m.a.s.l.) and upper altitude (UA: 2001–2300 m.a.s.l.)]. A total of 60 quadrats of 20m x 20m, 5m x 5m, and 1m x 1m with six horizontal transect lines were employed to gather data on the tree, shrub, herbaceous, and soil, respectively. To estimate organic carbon percentage, soil parameters were collected from three soil profiles (i.e., 0 to 10 cm, 10 to 20 cm, and 20 to 30 cm). The mean total carbon stock of the study area was 641.18 Mg ha-1. MA had relatively higher TC than the other gradients. But the LA had the lowest TC stock, due to a high amount of human and animal interference. The results showed that the UA had significantly higher above-ground (AGC) and below-ground carbon (BGC) stocks with 147.3±39.4 Mg ha-1 and 18.37±7.8 Mg ha-1, respectively, compared to other gradients. However, LA had the lowest AGC (66.8±8.7 Mg ha-1) and BGC (12.06±2.6 Mg ha-1). Lower altitude exhibited a significantly higher SOC value than the other two altitudinal gradients followed by MA. The UA had the lowest SOC value. SOC across the three soil profiles follows a reduction trend from topsoil depth to lower soil depth with significant variation. In conclusion, LA should embrace better ecological, policy, and socioeconomic considerations than the other gradients.

Soil Depth Significantly Shifted Microbial Community Structures and Functions in a Semiarid Prairie Agroecosystem.

The North American Great Plains cover a large area of the Nearctic ecozone, and an important part of this biome is semiarid. The sustainable intensification of agriculture that is necessary to produce food for an ever-increasing world population requires knowledge of the taxonomic and functional structure of the soil microbial community. In this study, we investigated the influence of soil depth on the composition and functions of the microbial communities hosted in agricultural soils of a semiarid agroecosystem, using metagenomic profiling, and compared them to changes in soil chemical and physical properties. Shotgun sequencing was used to determine the composition and functions of the soil microbial community of 45 soil samples from three soil depths (0–15 cm, 15–30 cm, and 30–60 cm) under different agricultural land use types (native prairie, seeded prairie, and cropland) in southwest Saskatchewan. Analysis of community composition revealed the declining abundance of phyla Verrucomicrobia, Bacteroidetes, Chlorophyta, Bacillariophyta, and Acidobacteria with soil depth, whereas the abundance of phyla Ascomycota, Nitrospirae, Planctomycetes, and Cyanobacteria increased with soil depth. Soil functional genes related to nucleosides and nucleotides, phosphorus (P) metabolism, cell division and cell cycle, amino acids and derivatives, membrane transport, and fatty acids were particularly abundant at 30–60 cm. In contrast, functional genes related to DNA and RNA metabolism, metabolism of nitrogen, sulfur and carbohydrates, and stress response were more abundant in the top soil depth. The RDA analysis of functional genes and soil physico-chemical properties revealed a positive correlation between phages and soil organic P concentrations. In the rooting zone of this semiarid agroecosystem, soil microbes express variable structural patterns of taxonomic and functional diversity at different soil depths. This study shows that the soil microbial community is structured by soil depth and physicochemical properties, with the middle soil depth being an intermediate transition zone with a higher taxonomic diversity. Our results suggest the co-existence of various microbial phyla adapted to upper and lower soil depths in an intermediate-depth transition zone.

Carbon Stock Potential across Different Land Covers in Tropical Ecosystems of Damota Natural Vegetation, Eastern Ethiopia

The research was carried out in Damota kebele, in the Oromia regional state of Ethiopia, to examine the carbon sequestration potentials under three land covers (i.e., farmland (FL); bushland (BL), and woodland (WL)). In the three land covers, 60 squares of 20 m × 20 m, 5 m × 5 m, and 1 m × 1 m with six horizontal transect lines were employed to gather data on tree, shrub, herbaceous, and soil, respectively. To estimate organic carbon percentage, soil parameters were collected from three soil profiles (i.e., 0–10 cm, 10–20 cm, and 20–30 cm). The results showed that MA had significantly higher above-ground carbon (AGC) with 67.9 ± 11.4 Mg ha−1, whereas BL had significantly higher below-ground carbon (BGC) stocks with 16.32 ± 5.5 Mg ha−1, compared to other gradients. However, FL had the lowest AGC (53.2 ± 4.5 Mg ha−1) and BGC (8.04 ± 2.9 Mg ha−1). FL exhibited a significantly higher SOC value than the other two land covers followed by WL. The BL had the lowest SOC value. SOC across the three soil profiles follows a reduction trend from topsoil depth to lower soil depth with significant variation. WL had relatively higher TC than the other gradients. But FL had the lowest TC stock. Due to a high amount of human and animal interference in FL, weak security, and law enforcement measures, it has low TC. In conclusion, FL should embrace the better ecological, policy, and socioeconomic considerations than the other land covers.

The impact of Tamarix invasion on the soil physicochemical properties

The exotic Tamarix species, T. ramosissima and T. chinensis, were introduced into South Africa in the early 1900s reportedly either for ornamental or soil wind erosion control purposes in the mines. They are, however, currently invading several riparian ecosystems in the country and threatening its biodiversity and proper functioning. The objective of this study was to assess the effects of the exotic Tamarix species on the soil physicochemical properties vis-à-vis the indigenous Tamarix at the Leeu River in the Western Cape Province, of South Africa where they are purvasive. Three transects were laid from the riverbank towards the outer land, where the exotic followed by the native Tamarix species predominantly occurred. Soil was sampled from three points per transect and three soil depths (0–10, 10–20 and 20–30 cm) per point in winter and summer to determine selected soil physicochemical properties. The results showed that total nitrogen (TN), total carbon (TC), Sodium (Na), Potassium (K) and Magnesium (Mg) concentrations under the native and exotic Tamarix species were significantly higher than those in the open land without Tamarix species. The salinity under the native and exotic Tamarix species was greater (P < 0.05) in the topsoils (0–10 cm) than in the deeper soils (20–30 cm) with 5.05 mS cm−1 and 4.73 mS cm−1, respectively. Soil electrical conductivity (EC) was higher (P < 0.05) during the winter season under the exotic Tamarix species (5.05 mS cm−1) followed by the native species (4.73 mS cm−1) and it was the lowest in the control (0.16 mS cm−1) at 0–10 cm soil depth. Similarly, sodium and sodium absorption ratios (SAR) under the native and exotic Tamarix species were significantly greater than those in the control. The highest levels (P < 0.05) of TC were recorded at the topsoil (0–10 cm soil depth) under the exotic Tamarix species (1.17%), followed by the native Tamarix (1.07%) with the control recording the lowest (0.53%). There were no significant differences (P < 0.05) in K, TC, TN and SOC concentrations at lower soil depths (20–30 cm). The soil texture was significantly affected by the Tamarix species. The soil bulk density was lower under the exotic Tamarix followed by native Tamarix species than the control soils. The soil volumetric water content was higher under the exotic Tamarix species compared to the control. This study concludes that the invasion of the exotic and native Tamarix species altered the soil properties underneath and created conducive soil conditions for their predominance.

Assessment of Groundwater Potential Zones of Upper Blue Nile River Basin Using Multi-Influencing Factors under GIS and RS Environment: A Case Study on Guder Watersheds, Abay Basin, Oromia Region, Ethiopia

Groundwater is the most crucial resource for human beings and plays an important role in combating climate change and is substantial to human existence on the globe. Overall increased demand for water in different sectors, population growth, and unreliable rainfall necessitates the planning and management of groundwater. In this study, groundwater potential zones are delineated by combining remote sensing and geographical information system techniques in the Guder watersheds of the Upper Blue Nile Basin. Groundwater potential zones are prepared by using various multi-influencing factors like geomorphology, land use/cover, lithology, soil type, soil texture, drainage density, slope, lineament, rainfall, and elevation. These influencing factors’ features were given appropriate weightage according to Saaty’s AHP method, expert judgment, and their relative significance for groundwater occurrence. The groundwater potential zone was classified into different categories as very poor, poor, moderate, good, and very good according to quantile classification. This study reveals that about 33.6% of the Guder River Basin represents a good andvery good GWPZ category with an equal value of 16.8%,; while values 23.3%, 20.2%, and 22.9% were denoted by very poor, poor, and moderate groundwater potential zone, respectively. GWPZ was validated by field-collected data such as well discharge and soil depth. An accepted similarity was observed between delineated GWPZ and the basin’s soil depth graphically. The results of this study were also verified by correlation and kappa statistics values of 0.73and 77%, respectively. The study is certain with a sensible dimension of consistency in pairwise comparison between influencing and the overall weightage. The very high GWPZs are found in the northern part starting from the center longitude of the study area, more along with the northwestern, southern, and southwestern of the Guder subbasin. Low to very low groundwater potentiality has been seen at different distances from the center due to the presence of escapements, hills and steep side slopes, slopes, and rock surfaces. The study also revealed that the zone of high groundwater potential has high soil depth, and the zone of low groundwater showed low soil depth as the capacity of the aquifer to store water may depend on the depth of soil profile. This study attests to the GIS and remote sensing techniques as an effective model for delineation of GWPZs and can be applied at other basins of Ethiopia.

Increased rainfall may place saline/sodic soils on the tipping point of sustainability

Increased rainfall is increasing the risk of the capillary movement of sodium (Na⁺) and other salts from buried marine sediments to the soil surface in the North American northern Great Plains. These salts reduce productivity and resilience while increasing their effect on the environment. Understanding the interactions among management, climate, cropping system, and soil is the first step toward implementing effective management plans. Unfortunately, while much work has been conducted, little is known about the effective management of semiarid dryland saline/sodic soils. This study determined the influence of soil depth on hydraulic conductivity and changes in soil Na⁺ (mg Na⁺ kg^–1 soil) to electrical conductivity (EC_1:1) (dS m^–1) ratio following high spring rainfall in 2019 in three soils. The soil parent materials were Glaciolacrustrine underlaid at a depth of approximately 15 m by marine sediments that contained Na⁺ and other salts. The landscape positions included in the study were a well-drained shoulder, moderately well-drained backslope, and a poorly drained toeslope soil. Based on the soil classification, shoulder and backslope subsoils were not predicted to be salt affected, while the toeslope soil was predicted to contain a natric soil horizon. Rainfall in 2018, 2019, and 2020 was 46, 76, and 37 cm, respectively, and soil cores were collected prior to and following the 2019 high rainfall. Soil cores were separated into the 0 to 7.5, 50 to 57.5, 82.5 to 90, 92.5 to 100, and 105 to 112.5 cm segments. Samples from 2018 were analyzed for soil EC_1:1, pH, ammonium acetate extractable cations, soil particle size, available water at field capacity, drainable porosity, soil bulk density, and saturated hydraulic conductivity. Samples from 2019 were analyzed for EC_1:1 and ammonium acetate extractable Na⁺. Across the sampling sites, shoulder and backslope soils had higher saturated hydraulic conductivities than the toeslope soils. Saturated hydraulic conductivities were negatively correlated to pH (<i>r</i> = –0.55, <i>p</i> &lt; 0.01), the Na⁺ to EC_1:1 ratio (<i>r</i> = —0.66, <i>p</i> &lt; 0.01), extractable Na⁺ (<i>r</i> = —0.56, <i>p</i> &lt; 0.01), and sand content (<i>r</i> = —0.66, <i>p</i> &lt; 0.01), and positively correlated to the silt content (<i>r</i> = 0.65, <i>p</i> &lt; 0.01). A comparison between the saturated hydraulic conductivity and the Na⁺ to EC_1:1 ratio suggests that saturated conductivities approached 0 cm h^–1 when the Na⁺ (mg Na⁺ kg^–1) to EC_1:1 (dS m^–1) ratio exceeded 600. The 2019 high rainfall increased the risk of soil dispersion in the lower soil depths (&gt;82.5 cm). For example, in the shoulder soil at the 105 to 112.5 cm depth, EC_1:1 decreased 0.936 ± 0.254 dS m^–1 from 2018 to 2019, whereas the exchangeable Na⁺ increased 688 ± 283 mg kg^–1 soil. Our findings suggest that a climate change-induced shift in rainfall patterns can increase salinity and sodicity risks in northern Great Plains subsurface soils. Salinity and sodicity risks are expanding into zones not previously identified as at risk, and improving or maintaining the productivity of these soils requires careful planning.

Changes in Soil Organic Carbon and Its Labile Fractions after Land Conversion from Paddy Fields to Woodlands or Corn Fields

Land use change could significantly affect soil organic carbon (SOC) and other soil chemical properties. However, the responses of soil labile C fractions at different soil depths to land-use change are not still clear. The aim of this study was to investigate the effect of paddy field conversion on woodlands or corn fields on total soil organic C (TOC) and its labile C fractions including particulate organic C (POC), microbial biomass C (MBC), and potassium permanganate-oxidizable C (KMnO4–C) along a 0–100 cm soil profile. Our results indicate that soil TOC concentrations increased by 3.88 g kg−1 and 3.47 g kg−1 in the 0–5 cm soil layer and 5.33 g kg−1 and 4.68 g kg−1 in the 5–20 cm soil layer during 13 years after the conversion from paddy fields to woodlands and corn fields, respectively. In the 20–40 cm soil layer, the woodlands had the highest TOC concentration (12.3 g kg−1), which was 5.13 g kg−1 and 3.5 g kg−1 higher than that of the paddy and corn fields, respectively. The increase in TOC was probably due to the absence of soil disturbance and greater root residue input into the woodland soil. In corn fields, pig manure addition contributed to the increase in soil organic C concentrations. In addition, the proportion of soil KMnO4–C increased after conversion from paddy fields to woodlands or corn fields in the 0–40 cm soil layer, ranging from 39.9–56.6% for the woodlands and 24.6–32.9% for the corn fields. The soil POC content was significantly higher in woodland and corn field soils than in paddy field soils at lower soil depths (5–40 cm). However, there were no differences in MBC contents in the whole soil profile between the woodlands and paddy fields. The KMnO4–C and MBC was the most important factor affecting the CMI values through the whole 0–100 cm soil profile. Overall, converting paddy fields to woodlands or corn fields increased the TOC and labile C fractions in the 0–40 cm soil layer. Future studies should focus on the response of the deeper soil C pool to land-use change.

Effect of Drip Fertigation under Different Fertilizer Levels on Nutrient Status in Coconut (Cocos nucifera L) Leaf

A study was conducted during 2017-18 under the All India Co-ordinated Research Project initiated in 2009 at research farm of Bihar Agricultural University, Sabour, Bhagalpur. The aim of this study was compare the nutrient concentration of coconut leaves at different nutrient levels through drip fertigation in a Randomized Block Design (RBD) with four (4) replications. Result was observed that leaf Nitrogen, Phosphorous, Sulphur, Iron, Manganese, Copper and Boron content under different fertigation treatments were not significantly different from each other. The content of micronutrients in leaf were found to increase with increasing levels of fertilizer in the treatments. Cation Exchange Capacity was positively correlated with all the leaf nutrients. Organic carbon did not show remarkable relation with plant nutrient parameters. Soil K content of all three depths was positively correlated with all the leaf nutrient elements. Soil pH value was positively correlated with leaf P content in coconut which explains that leaf P content is directly proportional to the soil pH value. Electrical conductivity (EC) of soil was also positively correlated with P, K and B concentration in coconut leaf. Correlation coefficient value between CEC and leaf nutrient contents explains that 2nd depth of soil is more important for mineral nutrition of coconut palm. Correlation coefficient values between soil P content and leaf nutrient content. Higher correlation coefficient value was found at lower soil depth between available sulphur content in soil and sulphur content in leaf of coconut. This result suggests that inherent supplying capacity of micronutrient of experimental soil is not so influential for higher plant growth, but application of N, P and K fertilizers trigger the absorption capacity for micronutrient from soil. Under different NPK levels, the applied NPK does not have significant effect on leaf N, P, S, Zn content after five (5) years of experimentation while the effect was found to be significant for few elements like K, Fe, Mn, Cu, and B. An increasing trend was observed for leaf nutrient content with increasing levels of fertilizer application.

Experimental study of uplift of buried pipe liquefiable soil at different depths

In recent earthquakes, many buried structures, including tunnels and lifelines, have been seriously damaged. It is noteworthy that the phenomenon of soil liquefaction has a significant role in the occurrence of these damages. The enormous damage because of soil liquefaction, has motivated the study of uplifting of lifelines. Therefore, in this research, it has been attempted to study uplift of buried pipe in liquefiable soil by physical modeling. The soil used in this study was Gum tape sand and the shaking table was used to simulate the seismic load. Also, due to the importance of the deformation mechanism in this process, particle image velocimetry technique has been used. The buried pipe (at three depths of 1.5, 2.5 and 5 times the diameter of the pipe) has been subjected to seismic load and then deformation mechanism of it has been discussed. The results show that by decreasing the buried depth of the pipe, due to the relatively high pore water pressure at the lower soil depth, the overpressure created after the dynamic loading tends to dissipate and flow to low pressure points (surface area) and because of upward flow in the surface area, the uplift will continue to some extent. Also, the displacement vectors around the pipe are circular rings that try to uplift the pipe.

The Effect of Foliar and Ground-Applied Essential Nutrients on Huanglongbing-Affected Mature Citrus Trees.

The fate of foliar and ground-applied essential nutrients is the least studied topic under citrus greening or Huanglongbing (HLB)-affected citrus, which is inherently suffering from severe root decline because of HLB-associated problems. The objective of this study was to evaluate if ground-applied coupled with foliar spray of essential nutrients can reverse the decline in tree growth and understand the fate of the nutrients in the soil-root-tree interfaces. The treatments were arranged in a split-split plot design in which nitrogen (N) was ground-applied in 20 splits biweekly and Mn, Zn, and B were foliar and /or ground-applied in three splits following the spring, summer, and late summer flush seasons. Soil nutrients in three depths (0–15, 15–30, and 30–45 cm), root, and leaf nutrient concentrations of the essential nutrients, leaf area index (LAI), and tree canopy volume (TCV) data were studied twice (spring and summer) for two years. A significantly higher soil NH4-N and NO3-N concentrations were detected in the topsoil depth than the two lower soil depths (15–30 and 30–45 cm) indicating lesser nutrient leaching as trees received moderate (224 kg ha−1) N rate. Except for soil zinc (Zn) concentration, all the nutrient concentrations were significantly higher in the topsoil (0–15 cm), compared with two lower soil depths indicating that Zn was intricate by changes in soil environmental conditions, root acquisition, and/or leaching to lower soil depth. Leaf N concentration significantly increased over time following seasonal environmental fluctuations, tree growth, and development. Thus, leaf N concentration remained above the optimum nutrient range implying lower N requirement under irrigation scheduling with SmartIrrigation, an App used to determine the daily irrigation duration to meet tree water requirement and split fertigation techniques. Root Manganese (Mn) and Zn concentrations were significantly higher in the root tissues of the treated than the control trees and translocated to the leaves accordingly. Meanwhile, a significantly higher LAI for trees budded on Swingle (Swc) rootstock however, larger TCV for trees budded on Volkameriana (Volk) rootstocks. The trees had significantly larger TCV when the trees received a moderate N rate during early study years and under foliar 9 kg ha−1 coupled with the ground 9 kg ha−1 Mn and Zn treatments during the late study years. Therefore, split ground application of 224 kg ha−1 of N, foliar applied 9 kg ha−1 coupled with ground-applied 9 kg ha−1 Mn and Zn were the suggested rates to sustain the essential leaf nutrient concentration within the optimum ranges and improve the deterioration of vegetative growth associated with HLB-induced problems of citrus trees.

Complex Valuation of Energy from Agricultural Crops including Local Conditions

This paper provides values of economic, energy and environmental assessments of 20 crops and assesses the relationships of soil-climatic conditions in the example of the Czech Republic. The comparison of main soil quality indicators according to the configuration of land and climate regions is performed on the basis of energy and economic efficiency as well as a comparison of the level of environmental impacts. The environmental impacts are identified based on the assessment of emissions from production and also in the form of soil compaction as an indicator of the relationship to soil quality. As concerns soil properties, of major importance is soil skeleton, slope of land and the depth of soil, which cause an increase in emissions from the energy produced. Substantially better emission parameters per 1 MJ through energy crops, the cultivation of perennial crops and silage maize has been supported. Among energy crops, a positive relationship with the quality of soil is seen in alfalfa, with a significant reduction in soil penetrometric resistance; energy crops are also politically justifiable in competition with other crops intended for nutrition of population. The main advantage of energy crops for the low-carbon economy is their CO2 production to MJ, which is almost half, especially in marginal areas with lower soil depths, slopes and stoniness, which can be included in the new agricultural policy.

Aboveground and belowground traits of turf‐type bahiagrass (Paspalum notatum Flügge) genotypes under simulated drought

AbstractAs awareness of environmental impacts of anthropogenic ecosystems increases, low input turfgrass species like bahiagrass (Paspalum notatum Flügge) may become more prominent in urban landscapes and on golf courses. A study was conducted at the West Florida Research and Education Center, Jay, FL, USA, to evaluate the performance of novel turf‐type bahiagrass genotypes under drought conditions. The experiment was arranged as a completely randomized block design. Three Wilmington‐mutants, three Argentine‐mutants, two experimental lines, and two industry standards [‘Argentine’ and ‘Empire’ zoysiagrass (Zoysia japonica Steud.)] were selected for this trial. Aboveground and belowground characteristics were evaluated by growing the grasses in clear acrylic tubes under greenhouse conditions. A progressive dry‐down and well‐watered control comprised the treatments. The tubes were weighed daily to determine their transpiration break and midpoints. The rate of root depth development (RRDD) was recorded by measuring the single visible deepest root. At the end of the dry down, plant roots were harvested and analyzed using WinRhizo. Although total root growth was reduced under drought conditions, plants tended to have faster vertical root growth and prioritized root development in the lower soil depths. Root length density (RLD) and the distribution of RLD in the lower soil depths, fast RRDD, and high transpiration midpoints were the most important drought responsive traits. These attributes were consistently observed on genotypes WilM10 and ArgM27.