Soil Aeration Research Articles

Development and testing of vehicle-mounted soil bulk density detection system

Soil bulk density (BD) reflects the soil’s ability to function for structural support, water and solute movement, and soil aeration. It is used to express soil physical and biological measurements on a volumetric basis for soil quality assessment and comparisons between management systems in precision agriculture. In order to solve the problem that it is difficult to directly obtain the BD with large sample size, this study introduces a self-developed vehicle-mounted BD detection system, which is a composite sensor. Through the collection and analysis of soil electrical conductivity (ECa), soil mechanical resistance (MR) and soil surface images (SIMG), BD is estimated. A systematic verification test was carried out in the experimental field in North China, the study depth was 0.2 m. The R2 and RMSE between the estimated BD and actual BD measured by core sampling were 0.647 and 0.173 (using Multiple Linear Regression), 0.591 and 0.160 (using Ridge Regression), 0.719 and 0.090 (using Gradient Boosting Decision Tree). Soil moisture content (SMC) was included into the model of BD and R2 of the model was increased from 0.719 to 0.775, RMSE was reduced from 0.090 to 0.073. The system can estimate the degree of soil compactness with R2 = 0.708 and RMSE = 0.049. SMC can also be estimated from ECa and MR (R2 = 0.481, RMSE = 1.658). These results show the potential of the vehicle-mounted BD detection system, which can provide the basis for fast, economical, and efficient soil physical property analysis.

Effect of Soil Aeration and Root Morphology on Yield under Aerated Irrigation

Soil compaction easily causes root hypoxia stress, resulting in poor root growth and the absorption of soil water and nutrients. We hypothesized that aerated irrigation (AI) could enhance nutrient uptake and utilization, thus unlocking the high yield potential by increasing soil aeration and root morphology indicators compared with that in the non-aeration treatment. A greenhouse experiment was conducted to investigate the effect of soil aeration and root morphology on the yield of greenhouse cucumbers. The dissolved oxygen (DO) in irrigation water at 10 mg L−1 (A1), 20 mg L−1 (A2), and non-aeration treatment (A0) were applied via a subsurface drip irrigation system. The soil respiration rates, DO in soil water, root morphology, and crop yield were measured. The results showed that AI could significantly improve the soil respiration rate, DO in soil water, and root morphology compared with non-aeration treatment. The A2 significantly increased soil respiration rate by 11.63% and 11.93%, respectively, compared with the A1 and A0 treatments. Under A1 and A2, the DO in soil water increased by 20.01% and 18.02%, respectively, compared with the A0. Moreover, during the flowering and fruit set, the mature, and the late stages, the root surface area, root volume, root tip number, root forks, and root dry weight in the A2 treatment significantly increased than that in the A0 treatment. The soil respiration rate, DO in soil water, root length, and root forks were the main indexes correlated to the yield, respectively. The DO in soil water and root forks number significantly influenced the yield. The cucumber yield and economic benefits in A2 peaked at 53.04 t ha−1 and 3.95 × 104 USD ha−1, increased by 7.86% and 7.30% compared with that in the A0 treatment, respectively (p < 0.05). The results could provide technical support and scientific knowledge for regulating greenhouse cucumbers under AI.

Towards the effects of moss-dominated biocrusts on surface soil aeration in drylands: Air permeability analysis and modeling

Soil aeration is an important factor influencing soil biological and biochemical processes because it directly affects soil microbial activity and respiration. As an important living skin of the soil, biocrusts strongly impact various soil properties and play a vital role in maintaining surface soil structure and multifunctionality. Although there are several studies concerning the effects of biocrusts on soil respiration processes, it is still not well understood how biocrusts affect air permeability (Ka) and soil aeration in drylands. In a semiarid climate region of the northern Chinese Loess Plateau, the Ka and air-filled porosity (εa) of moss-dominated biocrusts established on aeolian sand and loess soil were measured as a function of soil water content under laboratory and in situ conditions and compared to measurements of bare soils. The relative air permeability (Kra) of biocrusts and bare soils was further analyzed and estimated with commonly applied Kra models that are based on the soil water retention curve (SWRC), and the performance of these models was specifically assessed for biocrusts. The in situ measurements yielded a 51.8% and 76.7% higher Ka for the biocrust-colonized aeolian sand and loess soil, respectively, when compared to the bare soils. Correspondingly, in comparison to the bare soils, the εa of the biocrusts also increased by 38.0% for the aeolian sand and by 52.4% for the loess soil. The laboratory measurements showed an 8.5%–9.3% increase of Ka for the biocrust-colonized soils from wet to dry conditions when compared to their bare counterparts, which was mainly attributed to their higher fine particle and organic matter contents as well as to the moss rhizoids. Moreover, a positive linear relationship (R2 > 0.43) was found between the log Ka and log εa for both biocrusts and bare soils. Additionally, the biocrusts exhibited higher water content at almost all matric potentials in comparison to the bare soils. The Kra of biocrusts was 22.0% higher for aeolian sand and 42.1% higher for loess soil when compared to the bare soils. The van Genuchten-Burdine and Brooks and Corey-Burdine models performed best with regard to the estimation of Kra (RMSE ≤ 0.100, bias ≤ 0.018). In general, biocrusts may greatly increase surface soil aeration due to their higher Ka and εa, and the soil aeration status of biocrusts can be indirectly assessed through their effective degree of soil water saturation. Our findings suggest that biocrusts should be carefully considered in further studies of soil aeration related to biological processes and gas and vapor transport in dryland ecosystems.

Multi crop high efficiency seed drill with solar hybrid seed metering: A step toward precision and sustainability

High crop production with limited energy resources is always the priority area of developing countries. Conventional agricultural experimenting and crop production methods are time-consuming, challenging, laborious, and energy intensive. Various developments and experimental studies have been carried out for advancement in agriculture technologies. This study is mainly focused on the design and development of a unique high-efficiency seed drill machine to increase the energy efficiency of agricultural experiments, and crop production and conserve the tillage, seed, fertilizer, and power requirement. This machine has a special seed dividing head and seed distributor triggered with a mechanical timer. The mechanical timer is responsible to deliver seed to the seed distributor as per fixed plotting intervals. The seed distribution unit distributes the seeds uniformly in all furrows as per the pre-decided seed rate aided with a centrifugal glider aided with a DC motor powered by a 30 W solar PV plate and backup battery. Moreover, the machine has 9 × 9 s-type spring tines for seed and fertilizer, which are mainly designed for better soil pulverization and aeration with significant in-field resource conservation as per conventional alternatives. The effective width is seven feet and adjustable rows with versatile seed rate options. Overall, the results from different field tests verified the uniform seed dispersal with improved germination rate. The analysis of power requirements compared to conventional machines results in the 40% less power requirement. Overall, the machine has customized unique features for experiments and energy-efficient precision agriculture to conserve input resources.

Design and Fabrication of Solar Powered Tiller with Seed Sowing

Agriculture is very important for the Indian economy. India being a developed nation, where agriculture plays a major role in developing the nation needs in all outcomes, The present project aims to develop Solar Powered tiller to reduce the time of the farmer by digging into the soil for multiple times in a certain area, where it’s having an attachment of seed sowing. The chain sprocket is a motorized by wiper motor and tiller blade will break the soil into small pieces, which helps improve the aeration of soil and prevents weeds from growing. Here the power to accelerate the equipment is utilized from the solar panel and stored in the battery for further purpose, where the panel is fixed at the top of the tiller for continuous rays of energy absorption. The multimeter is fixed to check the solar panel output voltage. By using the power, it tends to run the tiller in a proper manner. The seed sowing hopper is fixed at back side of wheel, where the seeds are flow in ground by reciprocating motion by means of rotating wiper motor. Now this project's major focus is on creating a functional operating system. High safety reduced human effort, improved soil tiller efficiency, decreased work load, less worker fatigue, and lower maintenance costs are all achieved by the project.

Subsurface aeration alters the fungal composition of rhizosphere soil and tomato plant performance in Northwest China

Rhizosphere hypoxia constrains plant growth, and numerous studies have shown that root zone aeration accelerates plant photosynthesis and growth and increases crop yields. Nevertheless, the mechanism by which soil microorganisms are involved in this process is not clear. The purpose of the present study was to examine the effects of aeration and irrigation depth on the composition and structure of rhizosphere soil fungal communities and tomato plant performance. The amount of aeration assayed was equal to 0 (CK), 0.5 (V1), 1 (V2), and 1.5 (V3) times the porosity of the soil. The two depths of subsurface drip irrigation used were 15 (D15) and 40 cm (D40). The results demonstrated that soil aeration not only increased tomato plant performance but also influenced fungal diversity and composition. Compared to the no-aeration treatment, the V3 soil aeration treatment increased the total dry weight and fruit yield by 39.9% and 65.6%, respectively. The results also showed that the abundance of the phylum Ascomycota and the family Lasiosphaeriaceae increased with increasing soil aeration, whereas those of members of the phylum Zygomycota and the order Capnodiales decreased with increasing soil aeration. Moreover, the variation in subsurface irrigation depth altered the rhizosphere soil fungal community. In general, the results of this study demonstrate that root zone aeration can ameliorate hypoxic conditions in Lou soils and is beneficial to soil fungal communities and tomato plant performance. Keywords: tomato, soil aeration, rhizosphere soil fungal community, plant performance DOI: 10.25165/j.ijabe.20231601.6368 Citation: Li Y, Zhang M Z, Cao X S, Wang J W, Zhang Z X, Niu Q W. Subsurface aeration alters the fungal composition of rhizosphere soil and tomato plant performance in Northwest China. Int J Agric & Biol Eng, 2023; 16(1): 172–183.

Redoxtrons – An experimental system to study redox processes within the capillary fringe

AbstractSpatiotemporal characterisation of the soil redox status within the capillary fringe (CF) is a challenging task. Air‐filled porosities (ε), oxygen concentration (O2) and soil redox potential (EH) are interrelated soil variables within active biogeochemical domains such as the CF. We investigated the impact of water table (WT) rise and drainage in an undisturbed topsoil and subsoil sample taken from a Calcaric Gleysol for a period of 46 days. We merged 1D (EH and matric potential) and 2D (O2) systems to monitor at high spatiotemporal resolution redox dynamics within self‐constructed redoxtron housings and complemented the data set by a 3D pore network characterization using X‐ray microtomography (X‐ray μCT). Depletion of O2 was faster in the organic matter‐ and clay‐rich aggregated topsoil and the CF extended >10 cm above the artificial WT. The homogeneous and less‐aggregated subsoil extended only 4 cm above the WT as indicated by ε–O2–EH data during saturation. After drainage, 2D O2 imaging revealed a fast aeration towards the lower depths of the topsoil, which agrees with the connected ε derived by X‐ray μCT (εCT_conn) of 14.9% of the total porosity. However, small‐scaled anoxic domains with O2 saturation <5% were apparent even after lowering the WT (down to 0.25 cm2 in size) for 23 days. These domains remained a nucleus for reducing soil conditions (EH < −100 mV), which made it challenging to characterise the soil redox status in the CF. In contrast, the subsoil aeration reached O2 saturation after 8 days for the complete soil volume. Values of εCT_conn around zero in the subsoil highlighted that soil aeration was independent of this parameter suggesting that other variables such as microbial activity must be considered when predicting the soil redox status from ε alone. The use of redoxtrons in combination with localised redox‐measurements and image based pore space analysis resulted in a better 2D/3D characterisation of the pore system and related O2 transport properties. This allowed us to analyse the distribution and activity of microbiological niches highly associated with the spatiotemporal variable redox dynamics in soil environments.Highlights The time needed to turn from reducing to oxidising (period where all platinum electrodes feature EH > 300 mV) condition differ for two samples with contrasting soil structure. The subsoil with presumably low O2 consumption rates aerated considerably faster than the topsoil and exclusively by O2 diffusion through medium‐ and fine‐sized pores. To derive the soil redox status based upon the triplet ε–O2–EH is challenging at present in heterogeneous soil domains and larger soil volumes than 250 cm3. Undisturbed soil sampling along with 2D/3D redox measurement systems (e.g., redoxtrons) improve our understanding of redox dynamics within the capillary fringe.

Amelioration of dry land suboptimal using biochar and compost to improve soil physical properties and soybean yield

The primary constraint of suboptimal soils under wet tropical regions, besides their low pH, is their low soil organic matter (SOM) content. This research aimed to improve the soil properties of dry land suboptimal and the yield of soybeans by applying biochar and compost. This research was carried out to investigate the effects of coconut shell biochar (B) and Leucaena compost (C) applied alone (at a rate of 10 ton.ha-1) or in combination (5 B: 10 C; 10 B: 15 C each. thus 10 1 B: 10 C) on soil physicochemical properties, growth, and yield of Soybean on Ultisols in Jambi Province. Biochar and compost applied alone or in combination significantly increased soil organic matter (SOM), total porosity (TP), and Aeration Pore (AP); decreased bulk density (BD) and low drainage pore (LDP). Also, combined application and single application biochar or compost to impact beneficially on soil water retention and available water (AW). Additionally, combined application and single application biochar or compost additions increased components of yield as a number of pods of soybean. The study showed that biochar applied alone or in combination with compost offers the potential to enhance soil quality and improve soybean yield.

Impact of Tillage on Growth, Productivity and Economics of Soybean Grown in Vertisols of Western Madhya Pradesh, India

The investigation entitled, “Impact of Tillage on Growth, Productivity and Economics of Soybean Grown in Vertisols of Western Madhya Pradesh, India’’ was conducted during the kharif season of the year 2019-20 in the Department of Soil Science and Agricultural Chemistry, R.V.S.K.V.V., College of Agriculture, Indore. The objective of the experiment was to study the effect of tillage practices on the growth and productivity of soybean and to evaluate the effect of tillage on the economics and energy use efficiency of soybean. The experiment conducted in randomized block design and replicated five times. There were four treatments T1-Sub Soiling (SS) + Sowing by precision seed drill, T2- Tillage by Cultivator twice (CT), T3- Deep Tillage by M.B. plough (DT) and T4- Reduced Tillage + Crop Residues (RT+CR 30 % of previous crop). The results indicated that T1-Sub Soiling (SS) treatment was recorded maximum value of growth parameters, yield attributes ,seed yield, test weight, seed weight plant-1, Nodules Weight per plant, net returns and B:C which was statistically at par with treatment T2 Cultivator twice (CT). The overall conclusion drawn from the study is that due to continuous mechanization and use of heavy machinery a compact layer was observed in Vertisols at 20-30 cm soil depth which restricts root growth, reduces infiltration rate, thereby, causes water logging during rainy season. The poor soil aeration results in reduction in soybean productivity in Madhya Pradesh.

Root hypoxia aggravates the effects of saline tailings water on the growth and physiology of woody plants

AimsOil sands mining in the boreal forest produces large volumes of liquid tailings. Forestry research has generally focused on the thickness and composition of the soil layers to be placed on top of the tailings during reclamation. However, tailings release water, which may seep into the root zone and affect plants. Furthermore, the interactions and combined effects of root hypoxia and root substrate chemistry on plant responses are poorly understood.MethodsThe effects of the aqueous phase of novel tailings (Non-Segregating Tailings—NST) were studied under well-aerated and hypoxic conditions in three relatively waterlogging tolerant tree species [tamarack (Larix laricina), black spruce (Picea mariana), and balsam poplar (Populus balsamifera)] and three relatively sensitive tree species [lodgepole pine (Pinus contorta), jack pine (Pinus banksiana), and aspen (Populus tremuloides)] by growing them in hydroponic solutions in a controlled environment.ResultsRoot hypoxic conditions further reduced the survival, growth, and physiology of plants exposed to NST. Our results confirm that NST water produces the same deleterious effects in plants as previously reported in the amalgamated oil sands tailings. Root hypoxia inhibited salt sequestration in trembling aspen and may have inhibited an osmoregulative mechanism in black spruce needles.ConclusionsOur results highlight the potential impact of water seepage from buried tailings on reclamation success. Furthermore, hypoxic conditions can aggravate these effects by inhibiting salt stress mechanisms. We suggest that the preparation of reclamation sites impacted by tailings water should involve efforts to enhance soil aeration to minimize the detrimental effects on plants.

Calcium Preparation Aided Bioremediation of Fluoranthene-Contaminated Soil

Since natural bioremediation is a lengthy process, new bioremediation techniques should be developed to accelerate and optimize the removal of soil contaminants such as polycyclic aromatic hydrocarbons (PAHs). One of the substances that can be used to enhance PAH removal is calcium peroxide, applied as an oxidizing agent to improve soil aeration. Here, we investigated the bioremediation of soil contaminated with fluoranthene. Two doses of calcium preparation (CP), 0.29 and 0.58 g/kg, composed of calcium peroxide and calcium hydroxide, and increasing the soil pH by one and two units, respectively, were used. Fluoranthene decline was 83% and 95% for CP-aided soils, and 80% for soil without calcium preparation. During the remediation process, dynamic changes in the sorption complex of soils were found, mainly due to changes in the sum of base exchangeable cations. These changes in the first experiment period were significantly influenced by the presence of calcium preparation while in the second period by the presence of fluoranthene. The presence of calcium preparation caused changes in the microbiocenosis, especially at the higher dose. There was no effect of calcium preparation on plant growth.

The Soil Environment of Abandoned Charcoal Kiln Platforms in a Low-Altitude Central European Forest

This study examines the soil environment of eight charcoal kiln platforms and the neighboring soil in Czech and Bohemian low-altitude forest stands. Both mixed and undisturbed soil samples were used to assess the hydrophysical soil properties, nutrient content, cation exchange capacity, enzyme activity, and soil active carbon content, while soil color, stoniness, root density, and horizon thickness were estimated in the field. Charcoal-rich horizons had high total organic carbon concentrations and total nitrogen content (about 150% and 40% higher than in the organomineral horizons of the control plot, respectively), with total carbon stocks being higher than those in neighboring forest soils. Fine root density was highest in the charcoal-rich horizons, encouraged by high soil porosity, aeration, and favorable chemical properties. Enzyme group activity differed between individual soil horizons and kiln and control plots, with depolymerization enzyme activity highest in charcoal-rich horizons and humification enzyme activity highest in mineral horizons. Phosphatase, chitinase, and phenoloxidase activity were highest in charcoal-rich horizons, while β-glucosidase activity remained similar across horizons. After long-term abandonment, kiln sites shift from inhospitable sites to localized hotspots for plant and microbial growth, having more favorable physical, enzymatic, and chemical soil properties than the surrounding areas. This study confirmed that kiln production platforms act as microhabitat hotspots, also providing information on a wide spectrum of soil properties linked with soil microorganisms and root growth.

Climate Resilient Rice Production, Intercropping in Rice, Alternate Crops, Insitu Water Harvestinig and Ground Water Recharge to Combat Deficit Rainfall

Under changing climatic scenario, the rainfall amount and its distribution over space and time have become uncertain during the rice growing season which is also affecting rice production very often. Under deficit rainfall (50% & 19% in 2010 and 2012) from dry sowing or dry transplanting of rice to its harvest (48-52 cm rainfall from August to October), 42.8 q/ha coarse rice (cv, Annada) and 29-45 q/ha medium rice (cv. Satabdi and Himsagar) were harvested with one irrigation of 7.5 cm at panicle initiation stage. Water productivity ranged from 1250 to 1810 lit/kg of raw rice in different years. Dry seeded/dry transplanted rice was established receiving 55 to 74 mm rainfall within seven days. However, one supplemental irrigation following dry sowing/transplanting will ensure better seedlings establishment. Soil mulching by CRIJAF nail weeder at field capacity at 6-21 days after rice dry transplanting/dry sowing will maintain better hydro thermal regime and aeration of soil under deficit rainfall and ascertain composite weed control. Field capacity moisture during rice growth was enough to produce 45q/ha grain yield. This practice of rice production will mimimise methane gas emission over waterlogged rice paddies. In situ rain water harvesting in micro pond (12 m x 10 m x 1.5 m) sacrificing 9 per cent of total area (1333 m2) at lowest corner of the field provides life saving irrigation and produced 3-3.5 tonnes medium rice/ha. Through these micro ponds (7 in one hectare), in porous alluvial or sandy loam soils, annually around 3.58 to 7.47 crore litres of water can be recharged/ha to the unconfined aquifer in rainy season (July to September). Inter/relay cropping in rice field will produce 3.5 to 4.5 tonnes of rice along with 15- 200 q of different vegetables/ha, increase nutritional security of resource poor farmers, net return and make effective utilization of rainwater. Under deficit rainfall, as alternate crops of rice, yield of rain fed green gram (cv. Pant mung-5, RMG 62), arhar (UPAS -120) and sweet corn green cobs on ridges, were 21-23 q, 30 q/ha and 1,20,000 numbers/ha respectively. Adopting these rice production/intercrop/alternate crop/water harvesting technologies, sustainability can be ensured under a deficit rainfall, in current changing climatic scenario.

Modelling air conductivity function of unsaturated root-permeated soil

Air conductivity as a function of degree of saturation, ka(Sw), is a crucial air transport parameter of soil to evaluate soil aeration. This function controls the level of oxygen stresses introduced to plants. It has been found that plant roots affect ka(Sw) of soil where they grow in the soil pore space. However, there is no model available to predict ka(Sw) of root-permeated soils. Quantifying the effects of plant roots on ka(Sw) is vital to understand soil aeration. This study aims to derive a new model for the prediction of the ka(Sw) of unsaturated root-permeated soils. Then a verification experiment was conducted, aiming to validate the new model by comparing ka(Sw) predicted by the new model with ka(Sw) measured in the experiments. In the experiments, ka(Sw) of a compacted sandy loam vegetated with two grass species (Chrysopogon zizanioides and Cynodon dactylon) with different root densities was measured. The results showed that the proposed model predicts the ka(Sw) of root-permeated soils of various root densities well.

Comparison of Some Soil Enzymatic Activities in Luvisol of Conservation and Conventional Tillage in a Model Experiment

The effect of soil tillage operation on soil biological properties has not been extensively studied in Hungary. We investigated some soil biological enzymatic activities (dehydrogenase, β-glucosidase, and phosphatase) of a Luvisol, treated by different tillage, management intensities, i.e., conservation tillage (CT), fully conventional tillage with mouldboard ploughing every year (PT), and moderately conventional tillage with shallow and deep ripping intermittently in every two years (BR). A pot experiment was carried out in climate-controlled growth chamber for six weeks as a model experiment, of using the composite soils (0-20 depth) with the three types of tillage intensity. Our finding suggested, that adding of the crop residues might increase the soil organic matter content, that is reflected by the high concentration of labile carbon in the CT soil. The greater intensified soil aeration at the conventional tillage operation, contributed to the much higher dehydrogenase activity in the PT and the BR soil. Otherwise, the higher aeration of soil resulted a decreased β-glucosidase activity in the conventional tillage (BR) soil. The high phosphorus availability of soil correlated by the lowest phosphatase enzymatic activity and the improved available P ratio in CT soil, indicating the inhibition of phosphatase activity. The soil biological enzymatic activities was shown to be affected by the presence of different substrates at the three management practices.

Advances in Root System Architecture: Functionality, Plasticity, and Research Methods

Root system architecture (RSA) refers to the spatial distribution and extended morphology of plant root systems in soil. RSA not only determines the ability of plants to obtain water and nutrients but also affects other ecological functions. Hence, it plays a dominant role in the overall health of plants. The study of RSA can provide insight into plant absorption of water and fertilizers, the relationship between above- and belowground plant parts, and the physiological health and ecological functions of plants. Therefore, this paper summarizes research on the morphology, functionality, plasticity and research methods of RSA. We first review the basic structure, physiology, and ecological functions of root systems. Then the soil factors that shape RSA—including soil moisture, nutrients, temperature, aeration, and others—are summarized. After that, research methods for studying RSA are described in detail, including harvesting, two-dimensional morphological observation, and three-dimensional image reconstruction. Finally, future research developments and innovations are discussed to provide a theoretical basis for further investigations in this field.

Aerated drip irrigation improves water and nitrogen uptake efficiencies of tomato roots with associated changes in the antioxidant system

• After aerated drip irrigation, soil oxygen content significantly increased. • The duration and sequence of aeration changed the root antioxidant system. • The root antioxidant system correlated root morphology of tomato. • Root antioxidant systems and growth affect water and nitrogen uptake efficiency of tomato. China has the largest area of vegetable cultivation in greenhouse vegetable system in the world. However, the excessive application of irrigation and fertilizers has caused soil degradation and hardening, even leading to injury and yield loss in vegetable. Increasing soil aeration oxygen can improve crop water and nutrient uptake efficiencies. However, its effects on crop antioxidant systems are less known. Due to the sensitivity of the antioxidant system to changes in soil oxygen content, it is expected that aerated drip irrigation (ADI) delivering microbubble water to the crop rhizosphere will alter root antioxidant enzyme activities, malondialdehyde (MDA) content, and osmotic regulators in tomato plants. We conducted pot experiments under eight irrigation regimes: five aerated durations (0%, 25%, 50%, 75%, and 100%) of the subsurface drip irrigation period aerated (CK, A 25% , A 50% , A 75% , and A), with two aerated sequences (L: subsurface drip irrigation follow by aerated drip irrigation, F: aerated drip irrigation follow by subsurface drip irrigation) for the A 25% , A 50% and A 75% treatments. All treatments with ADI had an average of 7.63% higher oxygen concentration (OC) than the CK treatment at 74 d after transplanting. The principal component analysis revealed that MDA of all treatments had the greatest effect on the antioxidant system, while aerated drip irrigation reduced MDA content. Increasing aeration duration from A 25% to A 75% significantly affected antioxidant enzyme activities and root growth parameters, and the L treatment had higher values than the F treatment. The L -A 75% treatment had the highest water use efficiency, nitrogen uptake efficiency, and yield. The structural equation model demonstrated that ADI indirectly promotes tomato water and nitrogen uptake efficiencies by affecting the antioxidant system and root growth.

Effect of Oil Spill on Physicochemical Properties of Soil Spilled Sites in Kokori, Ethiope East Local Government Area, Delta State, Nigeria

Oil pollution might affect soil physicochemical properties. Pore spaces might be clogged, which could reduce soil aeration, water infiltration and increase bulk density, subsequently affecting plant growth. This study investigated the effect of oil spill sites at Kokori, Delta State, Nigeria, analyzing physicochemical properties, total petroleum hydrocarbon, polyaromatic hydrocarbon, benzene, anions and selected heavy metal concentrations using standard methods. Data obtained revealed that the physicochemical properties of the assessed soils were insignificantly altered when compared with their respective DPR intervention values. PH values were in the range of 4.80-5.60 which is considered to be strongly acidic. The electrical conductivity ranged from 122µS/cm to 185µS/cm indicating that the soil is saline. Chloride ion values were between 32.50mg/kg to 82.10mg/kg. Nitrate ranged from 0.85mg/kg to 1.04mg/kg, while phosphate was between 0.34mg/kg and 0.96mg/kg. Total petroleum hydrocarbon varied from 7.12-45.66mg/kg for topsoil and 7.12-37.82mg/kg for bottom soil. It is lowest at 7.12mg/kg, mean at 18.1mg/kg. These values were within the DPR permissible limits. Benzene and Polyaromatic Hydrocarbon (PAH) had a constant value of 0.001mg/kg in all locations. Iron, arsenic, lead, mercury, cadmium, nickel and copper were the heavy metals detected. Their concentrations at spill sites were moderate and generally did not exceed their respective target limits. However, level of lead was as high as 11.6mg/kg in location 3. The soil should be monitored so that it does not exceed the threshold values of the studied parameters.

A new exponential model for predicting soil gas diffusivity with varying degree of saturation

AbstractSoil gas diffusivity (Dp/Do, gas diffusion coefficients in soil and in free air, respectively) and its relation to soil moisture is of great importance for describing and quantifying essential provisional and regulatory functions associated with terrestrial ecosystems such as soil aeration and greenhouse gas (GHG) emissions. Because gas migration in terrestrial soil systems is predominantly diffusion controlled, soil gas diffusivity becomes a fundamental prerequisite to quantify diffusive gas fluxes. Descriptive–predictive models are often used to estimate Dp/Do from easily measurable soil physical properties. Most of the available models take the form of power‐law functions and often tend to mischaracterize soil moisture effects at high moisture regimes. Based on a wide range Dp/Do data available in literature representing both intact and repacked soils, this study developed a novel air‐saturation‐dependent exponential (ASEX) gas diffusivity model to model Dp/Do in relation to soil air saturation. The model variable α, which represents the diffusivity at half air saturation normalized by the same in complete soil air saturation, could potentially differentiate moisture effects on different soil structural states. For specific applications in intact soils, we propose corresponding α values for upper‐limit (α = .6) and lower‐limit (α = .05) estimates of diffusivity, while an average value (α = .3) for general applications in both intact and repacked soils. As expected, our model based on a few a priori measured supportive data showed a better performance over the classical predictive models that do not use such measurements. The new model was further used to derive useful implications to showcase soil density effects on Dp/Do.

Cotton plant (Gossipyum spp.) development and yield are influenced by soil compaction: A Review

Intensive exploitation of soils has resulted in physical, chemical, and biological degradation as the demand for agricultural commodities, including cotton, has grown. Physical characteristics of the soil are those that are directly linked to the supply of water, nutrients, and air, as well as the establishment of roots for good agricultural crop development and yield. In this context, soil compaction is one of the most serious environmental issues caused by conventional agriculture. Cotton plant, which is highly sensitive to water stress and lack of soil aeration, is directly impacted by this type of degradation, which results in reduced root system development, affecting water and nutrient absorption, and causing damage to overall plant and crop yield. Soil compaction has been shown to reduce cotton yield in several studies; for example, the majority of the southeastern cotton-growing regions in the United States, which make up the majority of the U.S. Cotton Belt, have compacted soils and 66 % of cotton farmers in Australia were affected by soil compaction, while other research shows a 27 % yield loss for the crop in these conditions. On the other hand, most studies carried out in systems that aim to reduce soil compaction, have shown that improvements in soil physical properties related to decompaction result in an increase in cotton plant yield.