Higher Soil Bulk Density Research Articles

Phenological and yield components response of major exotic maize varieties to different levels of soil bulk densities

<p>Maize is the second staple food and a major cereal crop in Pakistan, but its actual yield is 25-30% less than the potential because of high soil bulk densities. Three exotic maize varieties (Baber, Pioneer-30P45, and Syngenta-6621) were evaluated under the three different soil bulk densities of 1.00 - 1.30, 1.30 - 1.60, and 1.60- 1.90 g.cm<sup>-3</sup>. Nine treatments were replicated three times, making 27 pots experiments under complete randomized design were tested. Results showed that bulk density significantly (α < 0.05) affected all the parameters of the crops except the number of days to emergence. The fewest number of days to emergence (8.4), tasseling (60.9), silking (66.9), maturity (91.9), leaves per plant (6.3), as well as the lowest shoot thickness (0.49 cm) were obtained under the 1.00 - 1.30 g.cm<sup>-3</sup> density. This density also produced the tallest plants (174.7 cm), highest stover (5938.7 kg ha<sup>-1</sup>), grain yields (1551 kg ha<sup>-1</sup>), and harvest index (21.9 %). Conversely, most days to emergence, tasseling, silking, and maturity occurred at the bulk density of 1.60 - 1.90 g.cm<sup>-3</sup>, which also produced the shortest plants and the lowest grain stover and grain yields as well as the harvest index. It was concluded that increasing bulk density levels increase the number of days to tasseling, silking, maturity, and leaves per plant and shoot thickness. Syngenta 6621 was found late in maturity among the hybrids but produced superior stover and grain yields.</p>

A Large-Scale Dataset of Conservation and Deep Tillage in Mollisols, Northeast Plain, China

One of the primary challenges of our time is to feed a growing and more demanding world population with degraded soil environments under more variable and extreme climate conditions. Conservation tillage (CS) and deep tillage (DT) have received strong international support to help address these challenges but are less used in major global food production in China. Hence, we conducted a large-scale literature search of English and Chinese publications to synthesize the current scientific evidence to evaluate the effects of CS and DT on soil protection and yield maintenance in the Northeast China Plain, which has the most fertile black soil (Mollisols) and is the main agricultural production area of China. As a result, we found that CS had higher soil bulk density, strong soil penetration resistance, greater water contents, and lower soil temperature, and was well-suited for dry and wind erosion-sensitive regions i.e., the southwest areas of the Northeast. Conversely, DT had better performance in the middle belt of the Northeast China Plain, which contained a lower soil temperature and humid areas. Finally, we created an original dataset from papers [dataset 1, including soil physio-chemical parameters, such as soil water, bulk density, organic carbon, sand, silt, clay, pH, total and available nitrogen (N), phosphorus (P), and potassium (K), etc., on crop biomass and yield], by collecting data directly from publications, and two predicted datasets (dataset 2 and dataset 3) of crop yield changes by developing random forest models based on our data.

Key soil properties influencing infiltration capacity after long-term straw incorporation in a wheat (Triticum aestivum L.)–maize (Zea mays L.) rotation system

Straw incorporation is increasingly being adopted in wheat (Triticum aestivum L.)–maize (Zea mays L.) rotation systems to improve soil physiochemical properties. To identify the main soil properties influencing infiltration capacity under long-term straw incorporation in a wheat–maize rotation system, the study set four treatments: no straw incorporation and fertilizer application, wheat straw incorporation with 276 kg nitrogen/ha, wheat and maize straw incorporation with 276 kg N/ha, and wheat and maize straw incorporation. The initial, average, and final infiltration rates were calculated to represent soil infiltration capacity. Compared with other treatments, wheat straw incorporation with 276 kg nitrogen/ha treatment significantly decreased soil bulk density, soil aggregate (DMWD) mean weight diameter measured using the dry sieving method, and weight rate of soil aggregates with diameters greater than 0.25 mm measured using the wet sieving method, and significantly increased total soil porosity, soil capillary porosity, field capacity, and weight rate of soil aggregates with diameters less than 0.25 mm measured using the wet sieving method. In contrast, wheat and maize straw incorporation treatment significantly increased soil bulk density and noncapillary porosity, but decreased total soil porosity, capillary porosity, and field capacity. The results of partial least squares regression indicated that the soil moisture content and DMWD were the primary factors influencing initial infiltration rate with positive regression coefficient. Higher total soil porosity, capillary porosity, field capacity, and DMWD contributed to higher final infiltration rate, while higher soil bulk density and noncapillary porosity were correlated with a lower final infiltration rate. The key influencing factors of average infiltration rate were soil bulk density, soil moisture content, total soil porosity, capillary porosity, and DMWD. The wheat straw incorporation with 276 kg nitrogen/ha treatment had higher infiltration rates than no straw incorporation and fertilizer application treatment. However, with an increase in straw amount, the influence of straw on infiltration showed a law of diminishing marginal returns. Therefore, wheat and maize straw incorporation with 276 kg nitrogen/ha treatments had a lower infiltration rate than wheat straw incorporation with 276 kg nitrogen/ha treatment. In addition, wheat and maize straw incorporation treatment had the lowest average and final infiltration rates of all treatments, indicating that excessive straw incorporation without nitrogen fertilizer had adverse effects on infiltration rates. This study furthers understanding of the influence of long-term straw incorporation on soil hydrological processes and helps rationally use straw resources in wheat–maize rotation systems.

Post‐paddy tillage affects soil physical processes of rain‐fed rice–wheat rotation

AbstractRain‐fed rice (Oryza sativa L.)–wheat (Triticum aestivum L.) (RFRW) rotation can be a resource‐saving solution for sustainable cropping systems. However, conventional puddled and flood transplanted rice, repeat tractor compaction, and years of shallow rotary tillage and paddy–dryland rotation had a negative impact on soil physical in the RFRW rotation (e.g., soil consolidation and shrinkage, shallow tillage layer). A 4‐yr field experiment was established to determine if different post‐paddy tillage systems would improve soil physical properties and plant factors. We compared no‐tillage (NT), conventional rotary tillage (RT), and deep tillage (DT) to improve the deteriorated soil structure, soil water, wheat root system, and grain yield. The results indicated that DT increased the average soil water content by 7.25% and 9.98%, increased field capacity by 9.58 and 5.23%, and decreased the soil bulk density by 6.2 and 2.2% at 0‐to‐20‐cm soil depth in 4 yr as compared to NT and RT, respectively. The NT increased the average relative soil moisture and had higher soil bulk density at 0‐to‐20‐cm depth. The DT deepened the root growth and increased the total root point numbers by 21.0 and 22.8% at 0‐to‐40‐cm soil depth in 4 yr, respectively, compared with NT and RT. In 4 yr, the DT significantly achieved higher average grain yield by 5.3 and 13.5%, respectively, compared with NT and RT. Overall, DT after rice was shown to be a promising management approach for improving wheat yields and might enable sustainable intensification of RFRW rotation.

Effects of genotype and ecological environment on the community structure and function of symbiotic bacteria in rhizosphere of ginseng

BackgroundGinseng, an important traditional Chinese medicine and a new resource food, has two production modes: farmland ginseng and forestland ginseng. Ginseng faces many problems such as high soil bulk density, easy hardening, low nutrient content, reduced porosity and increased soil acidification because of continuous cropping. Increasing studies indicate that plant rhizosphere symbiotic bacteria have an important effect on plant growth and development. We speculate that differences in microbial community may play an important role in promoting ginseng growth, development and health. To reveal the differences between farmland and forestland ginseng cultivation, and to address problems associated with continuous ginseng cropping, we investigated the effects of differences in plant rhizosphere symbiotic bacterial communities in promoting ginseng growth, development, and health.ResultIn the present study, the microbial communities in the rhizosphere of different genotypes and ecological environments were analyzed using the high-throughput sequencing platform Illumina, phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt), and other technologies. The organic matter, total nitrogen, available nitrogen, and available phosphorus contents in forestland soil were significantly different from those in farmland. The bacterial communities of ginseng in forestland, farmland, and greenhouse environments have specific dominant groups at the phylum and genus levels. There were differences in the gene functions of ginseng root-related bacterial communities between forestland and farmland. There were significant differences in the abundance distribution of rhizosphere bacteria among the different genotypes at the phylum and genus levels.ConclusionsThere is a close relationship between the ecological environment and bacterial population structure, and the ecological environment of forestland is more conducive to the formation of rich rhizosphere bacterial populations; additionally, the genetic diversity is richer than that of farmland. The rhizosphere bacterial community structure of ginseng was influenced by genotype, and there was a correlation between the distance between ginseng genotypes and the stratified clustering of its rhizosphere bacterial community structure.

Comparison of Infiltration Rates of Soils for Run-Off Management and Irrigation Planning in Makurdi Benue State, Nigeria

Understanding of initial infiltration rates and steady state infiltration rates of soil is very important for runoff management and irrigation scheduling. Therefore, a field experiment was conducted at the Teaching and Research Farm of Joseph Sarwuan Tarka University, Makurdi in 2018 to evaluate the initial and steady state infiltration rates of soils in Makurdi, Nigeria. Infiltration test was carried out using double ring infiltrometer at eighteen points. Initial and steady state infiltration rates and the cumulative infiltration were then calculated. Soil samples were collected from the adjacent area of the marked points at 0-15 cm and 15-30 cm depths for routine analysis. Undisturbed soil samples were also collected for the measurement of saturated hydraulic conductivity, bulk density, total porosity and moisture content determination. Simple descriptive statistic of mean, variance and standard deviation was used to analyze the data. The soils were predominantly sandy loan texture, with percentage sand, silt and clay as 710.7, 118.9, and 170.4 g kg-1 respectively. Soil bulk density and saturated hydraulic conductivity were 1.40 g cm-3 and 10.27 cm hr-1 at 0 – 15 cm depth, while soil organic carbon and CEC were 0.67 % and 6.62 cmol/kg respectively. The initial infiltration rate ranged from 7.40 - 87.46 mm hr-1 with a mean of 44.09 mm hr-1, meanwhile, the steady state infiltration rate ranged between 4.99 – 22 mm hr-1, with a mean value of 15.42 mm hr-1. High soil bulk density caused moderate to low infiltration capacity. The mean values for the steady state infiltration rate suggest that the soils of the study area have moderate infiltration capacity, therefore, water application for irrigation should be less or equal to the infiltration capacity of the soils to minimize water loss by surface runoff and erosion.

Effects of Land Use on the Soil Microbial Community in the Songnen Grassland of Northeast China.

Land use change obviously changes the plant community composition and soil properties of grasslands and thus affects multiple functions and services of grassland ecosystems. However, the response mechanisms of soil microorganisms, key drivers of the nutrient cycle and other soil functions during changes in grassland use type and associated vegetation are not well understood. In this study, Illumina high-throughput sequencing was used to analyze the changes in the soil microbial community structure of four grassland use types: exclosure (EL), mowed land (ML), grazed land (GL), and farmland (FL) in the Songnen Plain of Northeast China. The results showed that the FL and EL had significantly higher soil total nitrogen (TN) and lower soil electrical conductivity (EC) and pH than GL and ML. In contrast, the GL and ML had higher soil bulk density (BD) and organic matter, respectively, than the other land use types. In addition, the values of the Shannon diversity and Pielou’s evenness indexes were highest in the EL of all the land use types. Based on the high-throughput sequencing results, we observed high levels of α diversity in the FL for both bacteria and fungi. A structural equation model (SEM) revealed that pH and EC had a direct and positive effect on the bacterial community structure and composition. In addition, plant taxonomic diversity (according to the Shannon diversity and Pielou’s evenness indexes) indirectly affected the bacterial community composition via soil pH and EC. Notably, fungal composition was directly and positively correlated with soil nutrients and the value of Pielou’s evenness index changed with land use type. In conclusion, soil properties and/or plant diversity might drive the changes in the soil microbial community structure and composition in different grassland use types.

Soil Organic Carbon Stocks under Different Land Utilization Types in Western Kenya

The up-surging population in sub-Saharan Africa (SSA) has led to the conversion of more land for agricultural purposes. Resilient land utilization types that input carbon to the soil are key in enhancing climate change mitigation. However, there are limited data on different land utilization types’ contribution to climate mitigation through carbon input to soils. The study aims to quantify carbon stock across different land utilization types (LUT) practiced in Western Kenya. The following land utilization types were studied: agroforestry M (agroforestry with Markhamia lutea), sole sorghum, agroforestry L (agroforestry with Leucaena leucocephalaI), sole maize, and grazing land replicated thrice. To determine soil bulk density, SOC concentration, and soil carbon stock, soil samples were collected at depths of 0–5, 5–10, 10–20, and 20–30 cm from different LUTs. A PROC ANOVA was used to determine the difference in soil bulk density, SOC, and SOC stock between different LUTs and depths. The four variables differed across the LUTs and depths. A high soil bulk density was observed at 0–5 cm under grazing land (1.6 g cm−3) and the lowest under agroforestry M (1.30 g cm−3). Conversely, the soil bulk density was low at 20–30 cm under grazing land. The 0–5 cm depth accounted for a high share of SOC and SOC stock under Agroforestry M, while the 10–20 and 20–30 cm depth accounted for the high share of SOC stock under agroforestry L. The study showed differences in SOC across the different depths and LUTs. The findings highlight that agroforestry L and agroforestry M are promising interventions toward climate mitigation through carbon induction to soils.

Effect of Nano-Drip Irrigation and Crude Oil Application on Some Soil Physical Properties and Maize (Zea Mays L.) Production

A two factorial field experiment was conducted in loam soil as randomized complete block design with three replications during the spring season 2021, in Al-Hamidiyah research station (latitude33𝑜 27՚ 11.9՚N, longitude 43𝑜 23՚ 025՚𝐸(. To study the effect of nano-drip irrigation on soil bulk density, mean weight diameter and maize production. The first factor included crude oil application with two levels i.e., 1% and 0% while the second factor was two levels of irrigation, namely surface and sub-surface drip irrigation. The class A evaporation pan was used to determine the intervals between the irrigation events. The irrigation process was conducted when 50% of the available water is used. The soil bulk density, porosity, mean weight diameter and maize production were recorded. The obtained result showed that the lowest and highest soil bulk density were 1.37 and 1.62 Mg m-3 for the treatment SDIM. While the highest porosity was resulted from the treatment SSDIM reached 47%. The highest mean weight diameter was obtained from the treatment SSDIM by giving 0.39. Regarding the maize production, the highest yield was 1.399 kg.m-3 resulted from the treatment SSDIM.

Low soil fertility impairs cotton yield in the early years of no-tillage over degraded pasture

No-till is one of the main techniques for soil conservation and the mitigation of negative climate impacts. The objective of this study was to evaluate soil fertility, nutrition, cotton yield, and the fiber quality of cotton under different soil tillage systems. The study was carried out in the field in the 2017/2018 and 2018/2019 crop seasons. The experimental design was a complete randomized block with five replications. No-till (NT) and conventional tillage (CT) farming were used in the 2017/2018 and 2018/2019 crop seasons. NT resulted in higher soil bulk density (0-35 cm) than CT. When compared to NT, the availability of calcium, magnesium, potassium, phosphorous, cation exchange capacity, base saturation, zinc, and pH were 120, 90, 43, 135, 49, 110, 41, and 8% higher in areas with CT, respectively. Boron content was 14% higher with NT (0-20 cm) than CT. Leaf concentrations of nitrogen, Ca, and Mg were higher with CT in both seasons, and B was higher with NT. However, in the second season (2018/2019), leaf concentrations of P, K, and sulfur were higher with NT than CT. When compared to NT, fiber yields were 75% and 32% higher with CT in the 2017/2018 and 2018/2019 seasons, respectively; this corresponded to a difference of 757 and 420 kg ha-1 of fiber. However, no effects on fiber quality parameters were observed. NT limits the availability of most nutrients in soil in the early years of cotton cultivation; this reduces plant nutrition and fiber yield but has no effect on quality.

Barley-Based Cropping Systems and Weed Control Strategies Influence Weed Infestation, Soil Properties and Barley Productivity

Barley-based cropping systems (BCS) alter barley production by influencing weed infestation rates and soil nutrient dynamics. This two-year field study evaluated the interactive effects of five BCS and five weed control strategies (WCS) on soil properties and the growth and yield of barley. Barley was planted in five different cropping systems, i.e., fallow-barley (FB), maize-barley (MaB), cotton-barley (CB), mungbean-barley (MuB) and sorghum-barley (SB). Similarly, five different WCS, weed-free (control, WF), weedy-check (control, WC), false seedbeds (FS), chemical control (CC) and use of allelopathic water extracts (AWE), were included in the study. The SB system had the highest soil bulk density (1.48 and 1.47 g cm−3 during the period 2017–2018 and 2018–2019, respectively) and lowest total soil porosity (41.40 and 41.07% during the period 2017–2018 and 2018–2019, respectively). However, WCS remained non-significant for bulk density and total soil porosity during both years of the study. Barley with WF had a higher leaf area index (5.28 and 4.75) and specific leaf area (65.5 and 64.9 cm−2 g−1) compared with barley grown under WC. The MuB system under WC had the highest values of extractable NH4-N (5.42 and 5.58 mg kg−1), NO3-N (5.79 and 5.93 mg kg−1), P (19.9 and 19.5 mg kg−1), and K (195.6 and 194.3 mg kg−1) with statistically similar NO3-N in the MaB system under WC and extractable K in the MuB system under FS. Grain yield ranged between 2.8–3.2 and 2.9–3.3 t ha−1 during the period 2017–2018 and 2018–2019, respectively, among different WCS. Similarly, grain yield ranged between 2.9–3.2 and 3.0–3.2 t ha−1 during the period 2017–2018 and 2018–2019, respectively, within different BCS. Among WCS, the highest grain yield (3.29 and 3.32 t ha−1) along with yield-related traits of barley were in WF as compared to WC. Overall, MuB system recorded better yield and yield-related traits, whereas the lowest values of these traits were recorded for FB systems. In conclusion, the MuB system with WF improved soil characteristics and barley yield over other cropping systems. The AWE significantly suppressed weeds and was equally effective as the chemical control. Therefore, MuB and AWE could be used to improve barley productivity and suppress weeds infestation.

Improving irrigation, crop, and soil management for sustainable soybean production in Southern Brazilian lowlands

Lowlands have been cultivated with irrigated rice (Oryza sativa) in a monoculture cropping system for more than a century in southern Brazil. Shallow topsoil with high bulk density and deficient water infiltration favors the of production paddy rice; however, this condition does not favor species non-tolerant to flooding or oxygen restriction. Thus, soil and irrigation management may be necessary to raise the rice-soybean (Glycine max) rotation systems to sustainable levels. We carried out a two-year field experiment to assess the effects of irrigation treatments and soil management on soil physical properties, soybean growth, and grain yield in lowland systems. The experiment comprised a randomized block design with two factors and three replications. The main factor comprised the following irrigation treatments: sprinkler; surface, and rainfed. Four soil managements composed the second factor: conventional tillage (CT), no-tillage (NT), conventional tillage with raised-seedbed, and no-tillage with raised-seedbed. Soil physical properties, soil penetration resistance, crop parameters, grain yield and water productivity were evaluated. CT increased the soil penetration resistance near the soil surface layer. The highest soil bulk density at the 0.05-0.10 m layer in the CT reduces grain yield in rainfed soybean compared to NT. Supplementary irrigation increased soybean yield of about 36 % in years of uneven rainfall distribution. Sprinkler irrigation resulted in higher irrigated water productivity (90 %) compared to surface irrigation, contributing to a more sustainable increase in grain yield. Crop rotation in a no-tillage cropping scheme could improve the sustainability of diversified agriculture in lowlands.

Scour Hole Development in Natural Cohesive Bed Sediment around Cylinder-Shaped Piers Subjected to Varying Sequential Flow Events

Scour evolution and propagation around a cylinder in natural cohesive sediment was uniquely investigated under multi-flow event varying sequentially by velocity magnitudes. This flume study differs from others that only used test sediment with commercially available clays for single flow. The objective of this study was to explore the potential differences in scour hole development in natural riverbed sediments subjected to varying flow velocity scenarios, advancing our understanding from existing studies on scour. The study consisted of 18 experimental runs based on: velocity, flow duration, and soil bulk density. Scour hole development progressed initially along the cylinder sides, and maximum depths also occurred at these lateral locations. Scour hole depths were less for higher soil bulk densities (≥1.81 g/cm3) compared with lower densities, and erosion rates were slower. It was observed with all flow sequences that scour depths were similar at the end of each experimental run. However, scour initiation was observed to be time dependent for soils with higher bulk density (1.81–2.04 g/cm3) regardless of flow velocity sequences. The observed time dependency suggests a process feedback with the scour hole development initiated at the cylinder sides, which influence local 3D hydraulics as the scour hole depth progresses.

Arbuscular Mycorrhizal Communities in the Roots of Sago Palm in Mineral and Shallow Peat Soils

Communities of arbuscular mycorrhizal fungi (AMF) in plant roots improve host plant growth. In this study, AMF communities in the roots of the sago palm (Metroxylon sagu Rottb.) were investigated in mineral soil (MS) and shallow peat soil (SPS) in Sarawak, Malaysia. MS exhibited lower moisture content (MS, 38.1; SPS, 79.8%), higher pH (H2O) (MS, 4.6; SPS, 4.1), higher soil bulk density (MS, 1.03; SPS, 0.20 g cm−3), and higher nitrogen content (MS, 16.9; SPS, 2.7 kg m−3) than SPS at the same soil depth, while the phosphorus (P) content (Bray II) (MS, 1.6; SPS, 1.9 g P2O5 m−3) was similar. The AMF colonization rate was significantly lower in SPS (39.2 ± 12.5%) than in MS (73.2 ± 4.6%). The higher number of AMF operational taxonomic units (OTUs) was detected by amplicon sequencing of the partial small-subunit rRNA gene (MS, 78; SPS, 50). A neighbor-joining tree of obtained OTUs revealed that they belonged to Acaulosporaceae, Ambisporaceae, Claroideoglomeraceae, Gigasporaceae, and Glomeraceae. The lower abundance and diversity of AMF in SPS are possibly caused by abiotic factors, including soil physicochemical properties. Glomus and Acaulospora species detected in SPS might have strong tolerance against acidity and high soil moisture content.

Particle size distribution and clay minerals in dryland soils of Aceh Besar, Indonesia

Soil particle size distribution is a fundamental physical property affecting other soil properties. This research aims to determine the distribution of soil particles and the composition of clay minerals on each layer of the horizon in four soil profiles (P1, P2, P3, and P4) with different parent materials in the dryland of Aceh Besar district which includes Entisols Jantho, Andisols Saree, Inceptisols Cucum, and Oxisols Lembah Seulawah. Particle size distribution (or texture) and bulk density (BD) were analyzed in the laboratory. Soil structure and consistency were observed directly in the field. The type of clay minerals was identified by X-ray diffraction, while Fe, Al, and Si-oxide were extracted by dithionite-citrate solution. The results shown that the particle size distribution and the physical properties of dryland soils of Aceh Besar vary between soil orders. Andisols Saree has better physical properties than the physical properties of other soils and low bulk density. The Al, Fe, and Si fractions and clay mineral composition in the soil profiles also vary considerably between soil orders. The Andisols are dominated by allophane minerals (amorphous fractions) while Entisols, Inceptisols and Oxisols consist of mixed minerals of feldspar, quartz, halloysite, goethite, and other clay minerals. These soil orders have some soil physical constraints i.e. high soil bulk density, low water holding capacity and poor soil structures. Improvements in the physical properties of the soil on Aceh Besar dryland are indispensable to improve the quality of the soil.

PERFORMANCE EVALUATION OF THE POPULAR SWRC MODELS AT DIFFERENT SOIL BULK DENSITY RANGES

Soil bulk density is an important soil property which influences the hydraulic properties of soil. Soil bulk density has never been a fixed soil property, but it varies spatially due to soil changes and temporally due to human activities, soil management and effects of climate change. This changes in soil bulk density affects the characterization of hydraulic properties of soil especially when mathematical soil retention models are used. Since the measurement of the soil water retention characteristics in the field is expensive, labor intensive and time consuming, mathematical models have been developed to predict these properties. Therefore, it is important to establish the impact of the soil bulk density on the performance of these mathematical models especially their accuracy to fit measured data using measured data. The aim of this study was performance evaluation of the water retention models at different soil bulk density ranges. The study used the dataset downloaded from the global database (ISRIC). The study used Residual Standard Error (RSE) and R2 to measure the accuracy of the model in predicting or quantify the goodness of fit to the experimental data. The low values of RSE shows that experimental data are close to the model predictions. This paper discussed the popular Soil Water Retention Characteristic (SWRC) models then it assessed their performance on varying soil bulk density ranges. The results from the study showed that the performance of the models improved with increase in values of field bulk density. It was established that Gardner and Bi-exponential models were better suited to describe SWRC irrespective of the variation of soil bulk density because they displayed consistent best performance (R2 greater than 0.98) at low and high soil bulk density. From the study, the soil scientist can choose these models to apply especially when the soil bulk density varies greatily.

Ecologically suitable areas for growing Scutellaria baicalensis worldwide: an analysis based on GMPGIS

This paper explored the ecologically suitable areas for growing Scutellaria baicalensis using Geographic Information System for Global Medicinal Plants(GMPGIS), to figure out the resource distribution of S. baicalensis worldwide and provide a scientific basis for its scientific introduction. A total of 349 S. baicalensis sampling sites were selected all over the world for GMPGIS-based analy-sis of the ecologically suitable areas with six ecological factors including annual average temperature, average temperature during the coldest season, average temperature during the warmest season, average annual precipitation, average annual relative humidity, and annual average illumination and soil type as the ecological indexes. The results demonstrated that the ecologically suitable areas for growing S. baicalensis were mostly located in the Northern hemisphere, and the suitable areas in the United States, China, and Russia accounted for 19.25%, 18.66%, and 13.15% of the total area worldwide, respectively. In China, the Inner Mongolia, Heilongjiang province, and Yunnan province occupied the largest proportions of the total area, namely 14.28%, 8.72%, and 6.18%, respectively. As revealed by ecological factors of each sampling site, S. baicalensis was resistant to low temperature but not to high temperature. The adaptive range of average annual precipitation is narrower than that of average annual air humidity. The suitable soils were mainly inceptisol, alfisol, and fluvisol. High temperature and rainy climate or excessively high soil bulk density was not conducive to the growth of S. baicalensis. The adoption of GMPGIS enabled to obtain areas with the greatest ecological similarity for S. baicalensis, which were reliable data supporting the exploration of resource distribution and reasonable introduction of S. baicalensis.

Twenty-Years of Hop Irrigation by Flooding the Inter-Row Did Not Cause a Gradient along the Row in Soil Properties, Plant Elemental Composition and Dry Matter Yield

In hops (Humulus lupulus L.), irrigation by flooding the inter-row can carry away suspended particles and minerals, causing gradients in soil fertility. The effect of more than 20 years of flooding irrigation on soil and plants was evaluated in two hop fields by measuring soil and plant variables in multiple points along the rows. In a second experiment 1000 kg ha−1 of lime was applied and incorporated into the soil to assess whether liming could moderate any gradient created by the irrigation. At different sampling points along the rows, significant differences were recorded in soil properties, plant elemental composition and dry matter yield, but this was not found to exist over a continuous gradient. The variations in cone yield were over 50% when different sampling points were compared. However, this difference cannot be attributed to the effect of irrigation, but rather to an erratic spatial variation in some of the soil constituents, such as sand, silt and clay. Flooding irrigation and frequent soil tillage resulted in lower porosity and higher soil bulk density in the 0.0–0.10 m soil layer in comparison to the 0.10–0.20 m layer. In turn, porosity and bulk density were respectively positively and negatively associated with crop productivity. Thus, irrigation and soil tillage may have damaged the soil condition but did not create any gradient along the row. The ridge appeared to provide an important pool of nutrients, probably caused by mass flow due to the evaporation from it and a regular supply of irrigation water to the inter-row. Liming raised the soil pH slightly, but had a relevant effect on neither soil nor plants, perhaps because of the small amounts of lime applied.

Modulation of the soil microbiome by long-term Ca-based soil amendments boosts soil organic carbon and physicochemical quality in a tropical no-till crop rotation system

Unsustainable agricultural management practices such as non-conservationist tillage and overuse of fertilizers result in soil acidity and, in turn, soil degradation due to reduced carbon (C) concentrations and nutrient availability and increased aluminum toxicity. Application of lime (L) and phosphogypsum (PG) can overcome these constraints and improve soil quality, but the long-term effects of these amendments on both abiotic and biotic soil properties are not known, particularly when applied in combination. Here, we evaluated the effects of L (acidity corrective), PG (soil conditioner), and their combination (LPG) on soil organic matter (SOM) transformations, soil chemical and physical properties, and microbiome assembly in a long-term experiment under a no-till crop rotation system in a tropical soil. The Ca-based soil amendments increased C concentrations (labile and stable fractions), improved soil physicochemical properties, and changed the associations between several bacterial and fungal groups. Contrary to expectations, the acidic soil amended with PG exhibited greater number of significant shifts in the bacterial community than soil amended with L or LPG, as well as higher soil bulk density. By contrast, the fungal community underwent greater shifts in soil amended with L or LPG, which had higher macroporosity. L and LPG amendment shaped the fungal community and rearranged the SOM fractions at similar rates, suggesting an essential role of the altered fungi in SOM transformation. In addition, combining L with PG increased the relevance of many low-abundance microorganisms, especially fungi, compared with the control, indicating an increase in their ecological role in the soil. Finally, by applying general joint attribute modeling and sensitivity analysis, we determined that soil fertility increased most in LPG-amended soil, as the ensuing changes in the bacterial and fungal communities resulted in improved SOM fractions, soil physical characteristics and, ultimately, soil quality.

Influences of different afforestation systems on the soil properties of limestone mountains in the mid-eastern region of China

Limestone mountain ecosystem degradation has resulted in decreased soil fertility, low water holding capacity, and low biomass productivity. Afforestation has been proposed as an effective method to improve soil properties, however, scant information is available. In this study, the influence of Platycladus orientalis (PO), Broussonetia papyrifera (BP), a mixed shrub dominated by Ziziphus jujuba, Viter negundo (ZV) and a mixed shrub-grass dominated by V. negundo cannabifolia and Arthraxon hispidus (VA) on soil properties at two depth levels (0–10 cm; 10–20 cm) was assessed. This study demonstrates that compared with VA and ZV, PO and BP had higher soil bulk density and subsoil and lower soil water content. A similar trend was observed in the soil content of organic carbon, total nitrogen and total phosphorus with the overall highest and lowest values found in ZV and BP, respectively. These soil nutrients also differed between the two soil layers; however, total soil phosphorus, soil organic carbon and total nitrogen content in PO were markedly higher in topsoil than in subsoil. The available soil nitrogen of ZV was the highest, followed by VA, PO and BP, and significant differences were also detected among them. The available soil phosphorus content did not differ by vegetation type, whereas its content in topsoil was notably higher than in subsoil at all sites. However, the marked difference between topsoil and subsoil was observed only for available potassium but not total potassium. Our study reveals the differential impacts of vegetation type on soil properties in a degraded limestone mountain ecosystem. The use of native shrubs and grasses can increase soil fertility and could be an alternative to the afforestation plan to rehabilitate a degraded limestone mountain area in the mid-eastern region of China.