Increased Soil Bulk Density Research Articles

Effect of Soil Compaction and Bulk Density on the Growth and Yield of Soybean (Glycine max) on Sandy Clay Loam Soil of the Semi-arid Region of Northern Nigeria as Influenced by Tractor Wheel Traffic

Soil compaction from farm machinery is an environmental problem. The effect of compaction on plant growth and yield depends on the crop grown and the environmental conditions that crop encounters. The effect of compaction from tractor traffic on soybean (Glycine max), variety TGX1448-2E, on a sandy clay loam soil in the semi-arid region of northern Nigeria was investigated for two growing seasons, 2015 and 2016. A randomized complete block design of the field of plots with treatments of 0,5,10, 15 and 20 passes of a tractor MF 390 was used. Each treatment was replicated three times. The soil bulk density, penetration resistance and soil moisture content for each applied load were measured and the yield from each treatment was determined. Agronomic treatments were kept the same for all plots in both 2015 and 2016. Results showed increased soil bulk density, penetration resistance and soil moisture content with increased tractor passes. Highest grain yield was obtained at 5 tractor passes with a mean bulk density of 1.76 Mgm,-3 penetration resistance 1.70 MPa and moisture content 13.37% with a mean yield of 2568 kgha-1 and lowest was obtained from 20 tractor passes were 340 kgha-1. Statistical models were used to predict yield as a function of bulk density, penetration resistance, moisture content, contact pressure, and a number of tractor traffic passes. Grain yield with respect to moisture content gave the best yield prediction (r2 = 0.94).

Soil Microbial Metabolic Activity and Community Structure in Drip-Irrigated Calcareous Soil as Affected by Irrigation Water Salinity

Saline water irrigation can dramatically change the soil environment and thereby influence soil microbial processes. The objective of this field experiment was to use Biolog and high-throughput sequencing methods to evaluate the metabolic activity and community structure of soil microorganisms after 9 years of saline water irrigation. The results showed that brackish and saline water irrigation significantly increased soil bulk density and salinity, but significantly decreased soil pH, TN, SOM, MBC, and metabolic activity. The Biolog tests of sole-carbon-source utilization indicated that the brackish and saline water treatments significantly reduced the utilization of four carbohydrate sources (D-cellobiose, β-methyl-d-glucoside, D-mannitol, and glucose-1-phosphate), two amino acid sources (L-asparagine and glycyl-L-glutamic acid), two carboxylic acid sources (D-galacturonic acid and D-malic acid), and two polymer sources (Tween 80 and glycogen). Brackish and saline water increased soil bacterial richness (ACE and Chao 1 indices) but had no effect on which bacterial phyla were present. Brackish and saline irrigation water significantly increased the relative abundance of four dominant bacterial phyla (Gemmatimonadetes, Actinobacteria and Chloroflexi, Saccharibacteria). In contrast, the relative abundance of five dominant phyla (Proteobacteria, Acidobacteria, Nitrospirae, Planctomycetes, and Verrucomicrobia) was reduced by brackish and saline irrigation water. Our study suggests that soil bacterial community will form significant differences species under different irrigation water salinity, which can adapt to saline stress by adjusting the species composition. The results of this study increase understanding about the potential effects of saline water irrigation on soil biological processes.

WATER INFILTRATION OF COVERING SOILS WITH DIFFERENT TEXTURES AND BULK DENSITIES IN GRAVELMULCHED AREAS

To determine the influence of different bulk densities and texture on soil water infiltration after remediation in gravel-mulched areas, we subjected two different soil types were to a battery of tests to determine their soil infiltration characteristics. The results show that the soil infiltration capacity decreases with increasing soil bulk density. A logarithmic negative correlation was identified between stable infiltration rate and the bulk density of the two soils (R2 > 95%). Moreover, the larger the bulk density, the smaller the cumulative infiltration, and there is a significant linear negative correlation between density and infiltration. The Kostiakov infiltration model better describes the infiltration process of the Lou soil at all stages and the infiltration of Yellow-brown soil before 40 min. Finally, as soil water is redistributed, and its content increases with soil depth, and the greater the bulk density, the greater the water storage capacity of the soil from 0 to 30 cm. Overall, the soil bulk density should be no less than 1.5 g/cm3 when Lou soil is chosen to cover on gravel-mulched land, and not less than 1.4 g/cm3 for Yellow-brown soil.

Grazing Crop Residues Has Less Impact in the Short‐Term on Soil Properties than Baling in the Central Great Plains

Core Ideas Corn residue grazing had little to no impact on soil health indicators. Residue baling increased wind erosion risks by 22 to 56%. Baling reduced near‐surface soil water content by 8 to 32%. Soil type or precipitation amount did not influence residue removal impacts on soil properties. Residue grazing can be a more sustainable practice than baling Cattle grazing and baling of corn (Zea mays L.) residues are common practices in integrated crop–livestock systems, but their impacts on soil properties are not well understood on a regional scale. We conducted a 3‐yr study across a precipitation gradient (ranging from 400 to 804 mm) in the central Great Plains to evaluate soil compaction, structural quality, water content, fertility, sorptivity, and microbial biomass in response to corn residue grazing and baling. Six on‐farm sites varying in soil texture, organic matter, crop rotation, and irrigation practices were established with three residue treatments: control, grazing, and baling. Sites were predominantly under conservation tillage management. Residue baling reduced residue cover by 57% and residue grazing by 17% relative to the control. At most sites, residue baling reduced near‐surface soil water content by 8 to 32% and increased wind erodible fraction by 22 to 56% compared with the control but grazing generally had no effect. Residue grazing and baling had small or no negative effects on other measured soil properties regardless of soil type or precipitation amount. When changes in soil properties did occur, they were due to differences in grazing duration or agronomic management. For example, grazing during spring at one of the sites increased soil bulk density by 7% (1.17 vs. 1.26 Mg m−3) relative to the control. This short‐term study indicates that residue grazing, in general, does not impact soil properties, but residue baling at high rates (>50%) could increase wind erosion risks and reduce surface soil water content in this region.

Yields, Soil Health and Farm Profits under a Rice-Wheat System: Long-Term Effect of Fertilizers and Organic Manures Applied Alone and in Combination

The rice-wheat system (RWS), managed over 10.5 Mha in the Indo-Gangetic Plains of India suffers from production fatigue caused by declining soil organic matter, multi-nutrient deficiencies and diminishing factor productivity. We, therefore, conducted a long-term field experiment (1998–1999 to 2017–2018) in Modipuram, India to study the effect of continuous use of farmyard manure (FYM) as an organic fertilizer (OF), mineral fertilizers applied alone (RDF) and their combination (IPNS), as well as the inclusion of forage berseem (IPNS+B) or forage cowpea (IPNS+C) on crop yield, soil health and profits. The long-term yield trends were positive (p < 0.05) in all treatments except the control (unfertilized) in rice, and the control and RDF in wheat. Although the yields of rice, wheat and RWS were highest under IPNS treatments (IPNS, IPNS+B, IPNS+C), the maximum annual yield increase in rice (9.2%) and wheat (13.7%) was obtained under OF. A linear regression fitted to the yield data under different IPNS options revealed a highly significant (p < 0.001) annual yield increase in rice (5.1 to 6.6%) and wheat (6.8 to 7.7%) crops. Continuous rice-wheat cropping with RDF brought an increase in soil bulk density (Db) over the initial Db at different soil profile depths, more so at depths of 30–45 cm, but inclusion of forage cowpea or berseem in every third year (IPNS+B or C) helped to decrease Db, not only in surface (0–15 cm) but also in sub-surface (15–30 and 30–45 cm depth) soil. Whereas soil organic carbon (SOC) increased under OF, IPNS and IPNS + legume (B or C) treatments, it remained unaffected under RDF after 20 RW cycles. The inclusion of legumes along with IPNS not only helped to trap the NO3–N from soil layers below 45 cm but also increased its retention in the upper soil (0–15 cm depth). On the other hand, RDF had a higher NO3–N content in the lower layers (beyond 45 cm depth), indicating downward NO3–N leaching beyond the root zone. A build-up of Olsen-P was noticed under RDF at different time intervals. The soil exchangeable K and available S contents were maximal under OF and IPNS options, whereas a decline in DTPA extractable-Zn was recorded under OF. Overall, RWS economics revealed that OF treatment involved the maximum cost of cultivation (US$1174 ha−1) with the least economic net return (US$1211 ha−1). Conversely, IPNS + legume (B or C) had lowest cost of cultivation (US$707 to 765 ha−1) and a significantly higher (p < 0.05) net return (US$2233 to 2260 ha−1). The study, thus, underlines the superiority of IPNS over RDF or OF; the inclusion of legumes gives an added advantage in terms of production sustainability and soil health. Further studies involving IPNS ingredients other than FYM is needed to develop location-specific IPNS recommendations.

Effects of plant residue management on soil properties, surface runoff, and soil loss under rainfall simulation in a semi-arid region in Iran

A 5-year field study was conducted on the effect of plant residue management on soil erosion, runoff, bulk density, penetration resistance, and organic carbon. There were three treatments: burning residues on field (BR), returning residues unto the soil surface after harvesting (TR), and removing residues from soil surface (RR) (control treatment). At the end of the 5-year treatment, a rainfall simulation at 90 mm h−1 was applied to each plot. After rainfall simulation started, the runoff volume and soil loss amount in samples were collected at four sampling times. The results showed that the runoff volume for BR (from 145.5 ± 12.2 to 190.0 ± 11.8 mL) differed significantly (p ≤ 0.01) from that of RR (from 32.3 ± 5.5 to 67.5 ± 11.1 mL) and TR (from 10.0 ± 0.7 to 16.7 ± 3.3 mL). A significant difference (p ≤ 0.01) was also observed between RR and TR regarding runoff volume and soil loss amount in different sampling times, except for the first sampling time (2–4 min). The runoff volume in BR and TR was 215% higher and 294% lower than that of the control (RR), respectively. As compared to the control (RR), soil loss decreased by 96.5% in TR but increased by 192% in BR. The BR increased soil bulk density and penetration resistance by 4.9% and 12.4%, whereas TR reduced them by 2.1% and 15.8%, respectively, as compared to the control (RR). The results indicated that the highest (0.35) and lowest (0.03) runoff coefficients were obtained for BR and TR treatments, respectively. It is concluded that returning plant residues to soil is the best residue management practice in decreasing soil runoff volume and controlling soil erosion in semi-arid regions.

Responses of soil organic carbon, soil respiration, and associated soil properties to long‐term thinning in a semiarid spruce plantation in northwestern China

AbstractSilvicultural thinning using whole‐tree harvesting (WTH) has been an important and common forest management practice for Picea crassifolia plantations in the Qilian Mountains of China. However, consequences of this silvicultural practice are still not well known. We examined the influence of three thinning levels on long‐term soil carbon storage, soil respiration (Rs), and soil properties. Our results showed that soil carbon stocks decreased significantly with increasing thinning intensity at a soil depth of 0–70 cm, whereas soil water storage increased, especially in the deep soil layers (30–70 cm). Mean Rs rates during the growing season increased significantly with increasing thinning intensity, and the dynamics of Rs coincided with that of soil temperature. Generally, 65% to 73% of the variation in Rs rates in three thinning levels was explained by the changes in soil temperature. WTH significantly increased soil bulk density at the 0‐ to 30‐cm and soil pH at the 0‐ to 20‐cm depths and significantly decreased soil nitrogen and C:N ratio in the 0‐ to 20‐cm layers. As no significant effect of WTH was detected on fine root biomass, we attributed the elevated soil respiration to accelerated decomposition of organic matter as a result of elevated soil temperature and substrate quality. Our results demonstrate the potential for WTH to relieve water deficits in spruce plantations in semiarid regions but suggest that WTH has a negative impact on carbon sequestration.

Impact of soil compaction on water content in sandy loam soil under sunflower

Abstract Soil compaction causes important physical modifications at the subsurface soil, especially from 10 to 30 cm depths. Compaction leads to a decrease in infiltration rates, in saturated hydraulic conductivity, and in porosity, as well as causes an increase in soil bulk density. However, compaction is considered to be a frequent negative consequence of applied agricultural management practices in Slovakia. Detailed determination of soil compaction and the investigation of a compaction impact on water content, water penetration depth and potential change in water storage in sandy loam soil under sunflower (Helianthus annuus L.) was carried out at 3 plots (K1, K2 and K3) within an experimental site (field) K near Kalinkovo village (southwest Slovakia). Plot K1 was situated on the edge of the field, where heavy agricultural equipment was turning. Plot K2 represented the ridge (the crop row), and plot K3 the furrow (the inter–row area of the field). Soil penetration resistance and bulk density of undisturbed soil samples was determined together with the infiltration experiments taken at all defined plots. The vertical bulk density distribution was similar to the vertical soil penetration resistance distribution, i.e., the highest values of bulk density and soil penetration resistance were estimated at the plot K1 in 15–20 cm depths, and the lowest values at the plot K2. Application of 50 mm of water resulted in the penetration depth of 30 cm only at all 3 plots. Soil water storage measured at the plot K2 (in the ridge) was higher than the soil water storage measured at the plot K3 (in the furrow), and 4.2 times higher than the soil water storage measured at the most compacted plot K1 on the edge of the field. Results of the experiments indicate the sequence in the thickness of compacted soil layers at studied plots in order (from the least to highest compacted ones): K2–K3–K1.

Storage of carbon in constructed technosols: in situ monitoring over a decade

Artificial soils constructed from wastes and by-products have been considered as a sustainable option for land reclamation. In particular, they could contribute in a complementary manner to natural soils to global climate regulation by storing large quantities of carbon (C). However, the evolution of C stocks in such newly formed soils remains largely unknown. This work aimed at evaluating the dynamics of C in constructed Technosols, focusing on two experimental sites in Lorraine, France, where Technosols were constructed from thermally-treated industrial soil, papermill sludge and green waste compost, and planted with grasses. Soil samples were collected over 12 years, and stocks of C were calculated, taking into account the increase in soil bulk density and the associated decrease in soil thickness over the years. The evolution of the stocks of organic C was compared to the evolution reported for natural grassland soils from the same region and for other Technosols. Initial organic C stocks in the two constructed Technosols were 50% higher than in natural analog soils when calculated over 30 cm, and up to 5 times higher when calculated over 100 cm. Organic C stocks in the two Technosols decreased over the first three years, but increased during the following years, most likely due to the accumulation of plant-derived C. A similar evolution was observed in other planted Technosols. We conclude that Technosols constructed from an adequate set of parent materials can keep large amounts of organic C over time and sequester additional C under permanent plant cover.

Effects of soil bulk density on growth, physiology and quality of Glechoma longituba

Through the determination of the growth, physiological and active components of Glechoma longituba, the effect of soil bulk density on growth and quality of G. longituba was explored. Through pot experiment, six different bulk density treatments were set for 0.8, 0.9, 1.0, 1.1, 1.2, 1.3 g·cm⁻³ , the growth index, physiological index and the content of active components were determined. The results showed that the growth indexes and biomass of G. longituba firstly increased and then decreased with the increase of soil bulk density. The dry weight of G. longituba achieved the maximum 5.70 g in the treatment of 1.0 g·cm⁻³ . The photosynthetic pigments, soluble sugars and free amino acids firstly increased and then decreased with the increase of soil bulk density. The suitable soil bulk density was beneficial to the accumulation of photosynthetic pigment, soluble protein and free amino acid synthesis. The content of malondialdehyde increased gradually with the increase of soil bulk density. The contents of ethanol-soluble extractives of G. longituba were greater than 25%, meeting its quality criterionin Chinese Pharmacopoeia 2015, achieved the maximum of 40.66% in the treatment of 1.0 g·cm⁻³ . The total flavonoids content of G. longituba increased gradually with the increase of soil bulk density, triterpenic acid and phenolic acids decreased gradually with the increase of soil bulk density. Soil bulk density has a significant effect on the growth and quality of G. longituba, and it is conducive to the growth and its medicinal quality at the soil bulk density of 1.0 g·cm⁻³.

Effect of long-term straw mulching and no-tillage on physical properties of meadow soil in cold region.

The effects of different straw returning technology and farming system on soil physical properties is not clear in Heilongjiang Province, which is located in middle temperature zone with large amount of straw. Here, the effects of straw mulching on soil physical properties in meadow soil under no tillage conditions were studied in field experiments for eight consecutive years (2010-2017). The no straw covering (0%), 30% coverage (30%), 60% coverage (60%) and 100% coverage (100%) were disposed in the experiment. The results showed that straw mulching under no tillage significantly increased soil bulk density by 0.10-0.20 g·cm-3, which increased with the increases of coverage amount. Straw mulching increased soil solid fraction by 2.5%-7.8%. Soil temperature decreased with the increases of coverage amount, and this trend was more apparent on the surface of soil. The temperature reduction in 0-5 cm soil layer was 1.87-2.90 ℃. Soil water content significantly increased with the increases of straw mulching, with an enhancement of 6.4%-10.2%. Straw mulch decreased the total porosity and diameter of >0.05 mm aeration pores, increased the effective pore size of 0.05-0.002 mm, with the magnitude of such effects being positively dependent on coverage amount. There was no significant effect of straw mulching on inactive porosity of soil. Long-term straw mulching increased soil compaction and soil moisture, reduced soil temperature and total soil porosity, and increased soil available porosity in 0-5 cm soil layer.

Ecological Restoration of Compacted Soil Following the Application of Different Leaf Litter Mulches on the Skid Trail over a Five-Year Period

Ground-based skidding operations performed with heavy machinery have drastic effects on forest soils, which normally culminate in an increased soil bulk density and removal of the litter layer. We aimed to assess the efficacy of different tree species litter on the recovery of soil physical, chemical, and biological properties over a 5-year period in the Hyrcanian forests, northern Iran. Therefore, treatments included 45 combinations of five treatments (undisturbed area—UND, untreated trail or bare soil—U, and three leaf litter types: pure beech—B, beech-hornbeam—B-H, and beech-hornbeam-maple—B-H-M) replicated in three plots in three transects. Results show that the highest litter thickness, and concentrations of C and N in the litter were observed in the UND treatment. The litter C/N ratios were highest in the untreated trail (U; 27.52) followed by B > B-H ≈ B-H-M > UND treatments. The highest recovery of soil bulk density, total porosity, macroporosity, soil penetration resistance, and aggregate stability was observed on the B-H-M and B-H treatment followed by the B treatment. The highest recovery values of pH, C, N, C/N ratio, C and N sequestration recovery rates were observed on the B-H-M treatment, followed by the B-H treatment. Significantly higher values of available nutrients (P, K, Ca, and Mg), earthworm density, and biomass were found in the UND treatment followed by B-H-M ≈ B-H > B treatment, while the lowest amounts of available P, K, Ca, and Mg were detected for the U trail. The high-quality litter species (hornbeam and maple) allowed for better recovery of the soil organic matter and increased nutrient availability compared to the lower quality litter (beech). We can conclude that by applying the different litters on compacted soil, the measured soil properties were significantly improved at the B, B-H, and B-H-M treatments. Nevertheless, the soil properties following the B, B-H, and B-H-M treatments still demonstrated significant differences with the UND treatment, even over a 5-year period.

Compaction and Physical Attributes of the Soil After the Development of Cover Plants

Compaction problems in heavily tilled soils have been commonly mitigated with the use of cover plants. Aiming to evaluate the effects of compaction on the physical properties of a plyntic Haplic-Alitic Cambisol soil after development of different cover crops, a complete randomized blocks design experiment, with 3 × 3 factorial arrangement and four replications, was conducted. Treatments consisted of cultivation of two legume species, crotalaria (Crotalaria juncea L.) and stylosanthes cv. Campo Grande (Estilosantes capitata + Estilosantes macrocephala) and a grass species, brachiaria (Urochloa brizhantha cv. Marandu), subjected to soil compaction: CM–Conventional soil management (tillage) without additional compaction; CMc4 and CMc8–conventional soil management with additional compaction using a 6 Mg tractor in four and eight wheel passes. Conventional management with additional compaction does not affect significantly the physical attributes at a soil depth of 0.10-0.20 m, and only the soil moisture does not differ according to the soil management, irrespective of the depth and kind of cover plant. Traffic levels in four passes result in an increased soil bulk density and macroporosity in the 0.0-0.05 m, and in soil resistance to penetration and total porosity in the layer up to 0.10 m. Cover crops are important in maintaining soil physical quality to reduce the negative effects of compacting forces, especially to stylosanthes cv. Campo Grande that provided greater soil protection in systems with or without addition of compaction, conditioning the lowest values of bulk density and soil resistance to penetration.

Effects of irrigation water salinity on soil salt content distribution, soil physical properties and water use efficiency of maize for seed production in arid Northwest China

In order to explore the use of groundwater resources, field experiments were conducted for three consecutive years during 2012-2014 in the Shiyang River basin of Northwest China. Irrigation was conducted using four different water salinity levels that were arranged in a split plot design. These four water salinity levels were s0, s3, s6 and s9 (0.71, 3, 6 and 9 g/L, respectively). The soil salt content, soil bulk density, soil porosity, saturated hydraulic conductivity, plant height, leaf area index and yield of maize for seed production were measured for studying the effects of saline water irrigation on soil salt content distribution, soil physical properties and water use efficiency. It was observed that higher salinity level of irrigation water and long duration of saline water irrigation resulted in more salt accumulation. Compared to initial values, the soil salt accumulation in 0-100 cm soil layer after three years of experiments for s0, s3, s6 and s9 was 0.189 mg/cm3, 0.654 mg/cm3, 0.717 mg/cm3 and 1.135 mg/cm3, respectively. Both greater salt levels in the irrigation water and frequent saline water irrigation led to greater soil bulk density, but poorer soil porosity and less saturated hydraulic conductivity. The saturated hydraulic conductivity decreased with increase in soil bulk density, but increased with improvement in soil porosity. It was noted that the maize height, leaf area index and maize yield gradually decreased with increase in water salinity. The maize yield decreased over 25% and the water use efficiency also gradually declined when irrigated with water containing 6 g/L and 9 g/L salinity levels. However, maize yield following saline water irrigation with 3 g/L decreased less than 20% and the decline in water use efficiency was not significant during the three-year experiment period. The results demonstrate that irrigation with saline water at the level of 6 g/L and 9 g/L in the study area is not suitable, while saline water irrigation with 3 g/L would be acceptable for a short duration together with salt leaching through spring irrigation before sowing. Keywords: saline water irrigation, soil salt content distribution, soil physical properties, maize for seed production, water use efficiency DOI: 10.25165/j.ijabe.20181103.3146 Citation: Yuan C F, Feng S Y, Wang J, Huo Z L, Ji Q Y. Effects of irrigation water salinity on soil salt content distribution, soil physical properties and water use efficiency of maize for seed production in arid Northwest China. Int J Agric & Biol Eng, 2018; 11(3): 137–145.

Safflower root and shoot growth affected by soil compaction

ABSTRACT Safflower (Carthamus tinctorius L.) is a commercial seed crop grown for its good yield of high-quality oil. It is tolerant to water stress but may be sensitive to soil compaction. The aim of this study was to assess safflower growth under different degrees of soil compaction at depths of 0.15 m to 0.20 m. The experiment was carried out in PVC pots constructed from three rings. Five levels of penetration resistance (0.20, 0.33, 0.50, 0.93, and 1.77 MPa) were applied in the intermediate ring, and two safflower genotypes, IMA-4904 and IMA-2106, were examined. There was no difference between safflower genotypes with respect to their resistance to soil compaction, which reduced root length density in the compacted layer and changed the root distribution in the soil profile, but did not prevent the roots from crossing the compacted layer and developing in depth. Increased soil bulk density in the compacted layer increased root diameter of the IMA-2106 genotype. Penetration resistance levels over 0.20 MPa (density of 1.2 mg.dm–3) limited safflower root development. The maximum safflower growth occurred when the soil penetration resistance was 0.86 MPa. In this study, the Q1/2 index was higher than 1.77 and 1.55 for the IMA-2106 and IMA-4904 genotypes, respectively. Hence, safflower has proven to be tolerant to soil compaction, and stands out as a species with potential to decrease soil bulk density.

Laboratory testing of Beerkan infiltration experiments for assessing the role of soil sealing on water infiltration

Soil surface sealing is a major cause of decreased infiltration rates and increased surface runoff and erosion during a rainstorm. The objective of this paper is to quantify the effect of surface sealing on infiltration for 3 layered soils with different textures for the upper layer and investigate the capability of BEST procedure to catch the formation of the seal and related consequences on water infiltration. Rainfall experiments were carried out to induce the formation of the seal. Meanwhile, Beerkan infiltration runs were carried out pouring water at different distances from the soil surface (BEST-H versus BEST-L runs, with a High and Low water pouring heights, respectively) for the same type of layered soils. Then, we determined saturated soil hydraulic conductivity, Ks, values from rainfall simulation and Beerkan infiltration experiments. Rainfall simulations carried out on soil layers having different depths allowed to demonstrate that infiltration processes were mainly driven by the seal and that Ks estimates were representative of the seal. Mean Ks values, estimated for the late-phase, ranged from 13.9 to 26.2 mm h−1. Soil sealing induced an increase in soil bulk density by 38.7 to 42.1%, depending on the type of soil. Rainfall-deduced Ks data were used as target values and compared with those estimated by the Beerkan runs. BEST-H runs proved more appropriate than BEST-L runs, those last triggering no seal formation. The predictive potential of the three BEST algorithms (BEST-slope, BEST-intercept and BEST-steady) to yield a proper Ks estimate for the seal was also investigated. BEST-slope yielded negative Ks values in 87% of the cases for BEST-H runs. Positive values were obtained in 100% of the cases with BEST-steady and BEST-intercept. However, poorer fits were obtained with the latter algorithm. The comparison of Ks estimates with rainfall-deduced estimates allowed to identify BEST-steady algorithm with BEST-H run as the best combination. The method proposed in this study could be used to easily measure the seal's saturated hydraulic conductivity of an initially undisturbed bare soil directly impacted by water with minimal experimental efforts, using small volumes of water and easily transportable equipment.

Long-term no-tillage application increases soil organic carbon, nitrous oxide emissions and faba bean (Vicia faba L.) yields under rain-fed Mediterranean conditions

The introduction of legumes into crop sequences and the reduction of tillage intensity are both proposed as agronomic practices to mitigate the soil degradation and negative impact of agriculture on the environment. However, the joint effects of these practices on nitrous oxide (N2O) and ammonia (NH3) emissions from soil remain unclear, particularly concerning semiarid Mediterranean areas. In the frame of a long-term field experiment (23 years), a 2-year study was performed on the faba bean (Vicia faba L.) to evaluate the effects of the long-term use of no tillage (NT) compared to conventional tillage (CT) on yield and N2O and NH3 emissions from a Vertisol in a semiarid Mediterranean environment. Changes induced by the tillage system in soil bulk density, water filled pore space (WFPS), organic carbon (TOC) and total nitrogen (TN), denitrifying enzyme activity (DEA), and bacterial gene (16S, amoA, and nosZ) abundance were measured as parameters potentially affecting N gas emissions. No tillage, compared with CT, significantly increased the faba bean grain yield by 23%. The tillage system had no significant effect on soil NH3 emissions. Total N2O emissions, averaged over two cropping seasons, were higher in NT than those in CT plots (2.58 vs 1.71 kg N2O-N ha−1, respectively; P < 0.01). In addition, DEA was higher in NT compared to that in CT (74.6 vs 18.6 μg N2O-N kg−1 h−1; P < 0.01). The higher N2O emissions in NT plots were ascribed to the increase of soil bulk density and WFPS, bacteria (16S abundance was 96% higher in NT than that in CT) and N cycle genes (amoA and nosZ abundances were respectively 154% and 84% higher in NT than that in CT). The total N2O emissions in faba bean were similar to those measured in other N-fertilized crops. In conclusion, a full evaluation of NT technique, besides the benefits on soil characteristics (e.g. TOC increase) and crop yield, must take into account some criticisms related to the increase of N2O emissions compared to CT.

Structure characteristics of soil and canopy and their relationships in wheat field under different tillage and application of organic fertilizer.

With the aim to optimize the structural characteristics of wheat canopy by improving topsoil structure, we examined the effects of three different tillage treatments, deep tillage (DT), shallow tillage (ST), no-tillage (NT) alone, and with application of organic fertilizer, DTF, STF and NTF, on the soil structure and wheat canopy characteristics for five years. Under the same tillage treatment, application of organic fertilizer decreased soil bulk density, the content of soil aggregates with diameter > 5 mm, the mean mass diameter (MWD), and geometric mean diameter (GMD) values of the soil aggregates with diameter >0.25 mm. Soil porosity and the content of soil aggregates with diameters of 2-5 mm and 0.25-2 mm at 20-40 cm soil layer were increased. Compared with other treatments, NTF was better in improving soil bulk density and increased soil porosity at 0-20 cm soil layer. DTF decreased the soil bulk density and the stability of mechanical aggregate with diameter > 0.25 mm at 40-60 cm soil layer, and increased soil permeability. Application of organic fertilizer decreased leaf angle index and increased leaf area index (LAI) and the net photosynthetic rate (Pn) of the flag leaf at post-anthesis stage. The lowest angle index and the highest Pn were detected in STF and DTF treatment, respectively. Results from path analysis showed that the direct path coefficients were significant from the independent variables (soil bulk density, soil porosity, R0.25 and MWD) to the dependent variables (angle index, LAI and Pn). At 0-20 cm soil layer, the increased MWD value was beneficial to the improvement of Pn and LAI. At 20-40 cm soil layer, the increased soil bulk density would optimize the leaf angle and further improve canopy light penetration. At 40-60 cm soil layer, high soil bulk density and low porosity negatively affected the value of LAI and Pn. We concluded that deep tillage or shallow tillage with application of organic fertilizer would be beneficial for improving soil structure, increasing soil permeability, optimizing wheat canopy structure, increasing canopy light harvesting rate, leaf area index and photosynthetic rate, with positive consequences on wheat yield.

Effects of irrigation water salinity on soil salt content distribution, soil physical properties and water use efficiency of maize for seed production in arid Northwest China

In order to explore the use of groundwater resources, field experiments were conducted for three consecutive years during 2012-2014 in the Shiyang River basin of Northwest China. Irrigation was conducted using four different water salinity levels that were arranged in a split plot design. These four water salinity levels were s0, s3, s6 and s9 (0.71, 3, 6 and 9 g/L, respectively). The soil salt content, soil bulk density, soil porosity, saturated hydraulic conductivity, plant height, leaf area index and yield of maize for seed production were measured for studying the effects of saline water irrigation on soil salt content distribution, soil physical properties and water use efficiency. It was observed that higher salinity level of irrigation water and long duration of saline water irrigation resulted in more salt accumulation. Compared to initial values, the soil salt accumulation in 0-100 cm soil layer after three years of experiments for s0, s3, s6 and s9 was 0.189 mg/cm3, 0.654 mg/cm3, 0.717 mg/cm3 and 1.135 mg/cm3, respectively. Both greater salt levels in the irrigation water and frequent saline water irrigation led to greater soil bulk density, but poorer soil porosity and less saturated hydraulic conductivity. The saturated hydraulic conductivity decreased with increase in soil bulk density, but increased with improvement in soil porosity. It was noted that the maize height, leaf area index and maize yield gradually decreased with increase in water salinity. The maize yield decreased over 25% and the water use efficiency also gradually declined when irrigated with water containing 6 g/L and 9 g/L salinity levels. However, maize yield following saline water irrigation with 3 g/L decreased less than 20% and the decline in water use efficiency was not significant during the three-year experiment period. The results demonstrate that irrigation with saline water at the level of 6 g/L and 9 g/L in the study area is not suitable, while saline water irrigation with 3 g/L would be acceptable for a short duration together with salt leaching through spring irrigation before sowing. Keywords: saline water irrigation, soil salt content distribution, soil physical properties, maize for seed production, water use efficiency DOI: 10.25165/j.ijabe.20181103.3146 Citation: Yuan C F, Feng S Y, Wang J, Huo Z L, Ji Q Y. Effects of irrigation water salinity on soil salt content distribution, soil physical properties and water use efficiency of maize for seed production in arid Northwest China. Int J Agric & Biol Eng, 2018; 11(3): 137–145.

Surface Energy Balance Partitioning in Tilled Bare Soils

Core Ideas Following tillage, soil bulk density increased after rainfall. Increases in soil bulk density decreased the available energy for turbulent fluxes. Surface energy balances in tilled soils are affected by changes in bulk density. Surface energy balance (SEB) partitioning is critical to heat and water budgets at the soil–atmosphere interface. Tillage can alter SEB partitioning by initially decreasing soil bulk density (ρb), after which ρb increases with time due to rainfall and other factors. The objective of this study is to determine the effect of ρb changes on SEB partitioning. We measured SEB components for two 4‐d periods (Period 1 and Period 2) at an early‐tilled (T1) and late‐tilled (T2) bare soil site. During Period 1, ρb, net radiation, and soil heat flux were similar for T1 and T2, but evaporation was higher at T2. During Period 2, ρb was 0.11 g cm‾3 larger at T2 than at T1. This resulted in a 7% higher soil heat flux at T2, which in turn caused 13% less evaporation. These results highlight the importance of considering dynamic ρb with time when determining SEB partitioning for tilled soils.