Organic matter accumulation post‐mineral sands mining

Soil development and organic matter (OM) accumulation are vital for sustainability in reclaimed prime farmlands following mineral sands mining. Additionally, the effectiveness of soil reconstruction techniques on soil development greatly influences crop productivity. Soil development and management effects following mineral sands mining were evaluated in years 1 (2005), 4 (2009) and 6 (2011) at the Carraway‐Winn Reclamation Research Farm, VA, USA. Treatments for this full scale agricultural experiment are as follows: biosolids applied at a rate of 78 Mg/ha managed with conventional tillage (BIO‐CT) and no‐till (BIO‐NT), a 15‐cm topsoil cap (TS), and a lime + fertilized control. Crop yields were determined annually, and soils were collected and analysed for aggregate size distributions and OM pools (available, aggregate‐protected and mineral‐bound). Crop yields (Corn‐Zea mays and wheat/soybean‐Triticum aestivum/Glycine max) were generally larger in the biosolids treatments from 2005 to 2008, with no difference among treatments from 2009 to 2011. Whole soil carbon (C) and nitrogen (N) rapidly increased between 2005 and 2009, mainly in the large macroaggregate (2000–8000 μm) size fraction. Carbon accumulation rates in the whole soils ranged from 2.85 to 3.58 Mg C/ha in the first 4 yr of soil development (similar trends were observed for N). There were no differences for soil aggregate parameters among treatments until year 6, where biosolids treatments contained more microaggregate (53–250 μm) and mineral‐bound C and N relative to other treatments. Short‐term increases in crop yields and long‐term increases in stable soil C and N make biosolids applications a viable alternative to traditional TS replacement strategies for this mining land use scenario.     

Assessing and Managing Soil Quality for Urban Agriculture in a Degraded Vacant Lot Soil

Following the decline of industrial manufacturing, many US cities have experienced severe population reductions that have resulted in large areas of vacant land. Urban agriculture has emerged as a desirable land use for these spaces, but degraded soils are common. Therefore, we measured soil and plant responses to amendments and management in urban lots where vacant houses had recently been demolished in Youngstown, OH, USA. Soil degradation was observed following demolition activities in the form of compaction (bulk density of 1·5–1·8 Mg m⁻³) and low soil microbial biomass C (21 mg C kg⁻¹ soil). Our split‐plot experiment measured the effects of organic matter (OM) amendments produced from yard wastes and the use of raised beds on soil properties and vegetable crop yields. Two years after their application, OM amendments resulted in significant improvement to a number of soil physical, chemical, and biological properties. Vegetable crop yields were improved by OM amendments in 2011 and by both OM amendments and the use of raised beds in 2012. A soil quality index, developed using factor analysis and the Soil Management Assessment Framework, produced values ranging from 0·60 to 0·85, which are comparable to those reported for rural agricultural soils. All results indicate that urban agriculture can be productive in vacant urban land and that amendments produced from urban yard wastes can improve soil quality at previously degraded sites and increase crop yields for urban agriculture. Copyright © 2015 John Wiley & Sons, Ltd.     

Soil organic carbon stock for reclaimed minesoils in northeastern Ohio

Reclamation of disturbed soils is done with the primary objective of restoring the land for agronomic or forestry land use. Reclamation followed by sustainable management can restore the depleted soil organic carbon (SOC) stock over time. This study was designed to assess SOC stocks of reclaimed and undisturbed minesoils under different cropping systems in Dover Township, Tuscarawas County, Ohio (40°32·33′ N and 81°33·86′ W). Prior to reclamation, the soil was classified as Bethesda Soil Series (loamy‐skeletal, mixed, acid, mesic Typic Udorthent). The reclaimed and unmined sites were located side by side and were under forage (fescue—Festuca arundinacea Schreb. and alfa grass—Stipa tenacissima L.), and corn (Zea mays L.)—soybean (Glycine max (L.) Merr.) rotation. All fields were chisel plowed annually except unmined forage, and fertilized only when planted to corn. The manure was mostly applied on unmined fields planted to corn, and reclaimed fields planted to forage and corn. The variability in soil properties (i.e., soil bulk density, pH and soil organic carbon stock) ranged from moderate to low across all land uses in both reclaimed and unmined fields for 0–10 and 10–20 cm depths. The soil nitrogen stock ranged from low to moderate for unmined fields and moderate to high in some reclaimed fields. Soil pH was always less than 6·7 in both reclaimed and unmined fields. The mean soil bulk density was consistently lower in unmined (1·27 mg m⁻³ and 1·22 mg m⁻³) than reclaimed fields (1·39 mg m⁻³ and 1·34 mg m⁻³) planted to forage and corn, respectively. The SOC and total nitrogen (TN) concentrations were higher for reclaimed forage (33·30 g kg⁻¹; 3·23 g kg⁻¹) and cornfields (21·22 g kg⁻¹; 3·66 g kg⁻¹) than unmined forage (17·47 g kg⁻¹; 1·98 g kg⁻¹) and cornfield (17·70 g kg⁻¹; 2·76 g kg⁻¹). The SOC stocks in unmined soils did not differ among forage, corn or soybean fields but did so in reclaimed soils for 0–10 cm depth. The SOC stock for reclaimed forage (39·6 mg ha⁻¹ for 0–10 cm and 28·6 mg ha⁻¹ for 10–20 cm depths) and cornfields (28·3 mg ha⁻¹; 32·2 mg ha⁻¹) were higher than that for the unmined forage (22·7 mg ha⁻¹; 17·6 mg ha⁻¹) and corn (21·5 mg ha⁻¹; 26·8 mg ha⁻¹) fields for both depths. These results showed that the manure application increased SOC stocks in soil. Overall this study showed that if the reclamation is done properly, there is a large potential for SOC sequestration in reclaimed soils. Copyright © 2005 John Wiley & Sons, Ltd.     

Aggregate and organic matter dynamics in reclaimed soils as indicated by stable carbon isotopes

Recovery of belowground ecosystem processes, such as soil aggregation and organic matter (OM) accumulation, in reconstructed soils is crucial to successful reclamation of disturbed lands. Objectives of this study were to track soil aggregate recovery in combination with aggregate associated OM on a chronosequence of reclaimed surface mine sites and a native, undisturbed reference site. Macroaggregate and micro-within-macroaggregate proportions increased with reclamation age, while microaggregate proportions decreased. Organic carbon (C) and total nitrogen (N) concentrations increased with reclamation age for each aggregate fraction and were higher in the OM fraction observed within soil aggregates than in the free OM fraction found between soil aggregates. Naturally occurring isotopic signatures of ¹³C decreased rapidly with reclamation age, indicating over 50% of total aggregate C to be new C from predominately C₃ plant community inputs after 26 years of reclamation. Soil aggregate size distribution trends of increasing macroaggregation and micro-within-macroaggregates along with rapid rates of OM accumulation with time indicated that reclaimed soils had recovered structurally towards a native soil condition after a period of 10-15 years.     

The Effect of Severe Drought on the Evolution of Urban and Manure Wastes in an Agricultural Soil in Mediterranean Ecosystems

In semi‐arid Mediterranean soils, water availability is the most limiting factor, negatively affecting the organic matter (OM) degradation. The aim of this work is to study under controlled laboratory conditions how three sources of OM [municipal solid waste (MSW), sheep manure (SM) and cow manure (CM)] behave when they are applied to an agricultural soil subjected to a severe year‐long drought. In order to apply the same concentration of OM to the soil (16·92 Mg OM ha⁻¹), 2 kg of soil was mixed with 30, 67·41 and 55·25 Mg ha⁻¹ (dry matter) of MSW, CM and SM, respectively. Two levels of irrigation were employed: (i) watered soils and (ii) non‐watered soils. Soil's chemical properties [water soluble carbon (WSC), humic acids, fulvic acids and protein mass distribution], biological properties (soil microbial biomass carbon and o‐diphenoloxidase activity) and solid‐state ¹³C cross‐polarisation magic angle spinning nuclear magnetic resonance spectroscopy were determined. In watered soils, the soil microbial biomass carbon was higher in the SM than in CM and MSW treatments (9·9% and 23·1%, respectively). The WSC was significantly higher in SM than in CM (55·7%) and MSW (78·7%) treatments. A decrease in the content of O‐alkyl C and an increase in alkyl C, aromatic C and carboxyl C were observed. In non‐watered soils, the biochemical properties and alkyl C and alkyl/O‐alkyl ratio decreased, whereas WSC content and O‐alkyl C increased. These results indicated that the evolution of OM and the activity of the microbial community in non‐watered soils were very different to those in the watered soils. Copyright © 2016 John Wiley & Sons, Ltd.     

Soil Organic Carbon Molecular Properties: Effects of Time Since Reclamation in a Minesoil Chronosequence

Studies on molecular characterization of soil organic carbon (SOC), although critical to understanding SOC dynamics, are relatively scarce for reclaimed minesoils. The aim of this study was to assess the effects of time since reclamation on SOC molecular properties in a reclaimed minesoil chronosequence using different spectroscopic indices. The chronosequence consisted of four minesoils, with similar soil‐forming conditions, reclaimed to pasture ecosystem, and distinguished only by time since reclamation varying from 1 to 22 years. Results indicated that the SOC molecules in the older minesoils were comprised of highly humified polyaromatic and polycondensed species with higher proportions of O‐containing and N‐containing functional groups. In each minesoil, resistant and labile SOC fractions were identified. The resistant SOC fraction constituted >20 and <10 per cent of total SOC (g kg⁻¹) in the oldest and youngest minesoil, respectively. Among the spectroscopic indices, the ϵ₂₈₅ ultraviolet‐visible index, diagnostic of aromatic C, was the most efficient in identifying the intrasite short‐term (1‐year) changes in SOC molecular properties. Strong positive relationships found between different spectroscopic indices and total SOC (g kg⁻¹), with consistently higher r² values observed in older minesoils, indicated that SOC molecular characteristics played a key role in overall SOC dynamics, becoming more influential with increasing time since reclamation. In addition, significant relationships between the spectroscopic indices and different soil quality parameters indicated that SOC molecular properties influenced soil quality as well. Overall, the results indicated that SOC molecular properties were useful indicators of both SOC dynamics and soil quality in this minesoil chronosequence. Copyright © 2013 John Wiley & Sons, Ltd.     

Potential of mine land reclamation for soil organic carbon sequestration in Ohio

Soils are an effective sink for carbon storage and immobilization through biomass productivity and enhancement of soil organic carbon (SOC) pool. The SOC sink capacity depends on land use and management. Degraded lands lose large amounts of C through SOC decomposition, erosion, and leaching. Thus, restoration of disturbed and degraded mine lands can lead to increase in biomass productivity, improved soil quality and SOC enhancement and sequestration. Reclamation of mined lands is an aggrading process and offers significant potential to sequester C. A chronosequence study consisting of 0‐, 5‐, 10‐, 15‐, 20‐ and 25‐year‐old reclaimed mine soils in Ohio was initiated to assess the rate of C sequestration by pasture and forest establishment. Undisturbed pasture and forest were used as controls. The SOC pool of reclaimed pasture sites increased from 15·3 Mg ha⁻¹ to 44·4 Mg ha⁻¹ for 0–15 cm depth and from 10·8 Mg ha⁻¹ to 18·3 Mg ha⁻¹ for 15–30 cm depth over the period of 25 years. The SOC pool of reclaimed forest sites increased from 12·7 Mg ha⁻¹ to 45·3 Mg ha⁻¹ for 0–15 cm depth and from 9·1 Mg ha⁻¹ to 13·6 Mg ha⁻¹ for 15–30 cm depth over the same time period. The SOC pool of the pasture site stabilized earlier than that of the forest site which had not yet attained equilibrium. The SOC sequestered in 0–30 cm depth over 25 years was 36·7 Mg ha⁻¹ for pasture and 37·1 Mg ha⁻¹ for forest. Copyright © 2000 John Wiley & Sons, Ltd.     

Physical properties of some intensively cultivated soils of Ireland amended with spent mushroom compost

In this paper, spent mushroom compost (SMC), a by‐product of the mushroom industry, is proposed as a suitable organic amendment for soil structure restoration. A 4‐month incubation pot trial was conducted in which fresh and composted SMC was amended at three different rates (50, 100 and 200 t ha⁻¹) to a range of structurally degraded tillage soils (n = 10). Soil OC content and aggregate stability as determined by the three disrupting tests of the Le Bissonnais method (fast‐wetting, slow‐wetting and mechanical breakdown) were investigated. Applications of 50, 100 and 200 t ha⁻¹ fresh SMC increased the OC content by 2·71 per cent, 2·69 per cent and 2·49 per cent respectively, while amendments of composted SMC increased the OC content by 3·28 per cent, 2·94 per cent and 2·87 per cent for each application rate, respectively. The effect of SMC on aggregate stability was generally positive and statistically significant in most soils. However, in soils 3 and 4 an application rate of 200 t ha⁻¹ SMC decreased the aggregate stability, on average, by 15 per cent, in comparison to the control, for the fast‐wetting test. Aggregate stability was strongly controlled by the inherent OC content of the study soils; that is, the OC content prior to SMC addition. A positive correlation coefficient was also evident for the dithionite‐extractable iron, most pronounced for slow‐wetting and mechanical breakdown treatments (r = 0·844 and r = 0·817 respectively). It is clear from this research that SMC amendments have the capacity to improve soil structural stability. Copyright © 2007 John Wiley & Sons, Ltd.     

Impact of 47 Years of No Tillage and Stubble Retention on Soil Aggregation and Carbon Distribution in a Vertisol

Aggregation often provides physical protection and stabilisation of soil organic carbon (C). No tillage (NT) coupled with stubble retention (SR) and nitrogen (N) fertiliser application (90 N, 90 kg N ha⁻¹ application) can help improve soil aggregation. However, information is lacking on the effect of long‐term NT, SR and N fertiliser (NT, SR + N) application on soil aggregation and C distribution in different aggregates in vertisols. We analysed the soil samples collected from 0‐ to 30‐cm depth from a long‐term (47 years) experiment for soil aggregation and aggregate‐associated C and N. This long‐term field experiment originally consisted of 12 treatments, having plot size of 61·9 × 6·4 m, and these plots were arranged in a randomised block design with four replications, covering an area of 1·9 ha. Soil organic C concentrations as well as stocks were significantly higher under the treatment of NT, SR + N only in 0–10 cm compared with other treatments such as conventional tillage, stubble burning + 0 N (no N application) and conventional tillage, SR + 0 N. Mineral‐associated organic C (MOC) of <0·053 mm was 5–12 times higher (r  = 0·68, p  < 0·05, n  = 32) compared with particulate organic C (POC) (>0·053 mm) in the 0‐ to 30‐cm layer. We found that NT, SR + N treatment had a positive impact on soil aggregation, as measured by the mean weight diameter (MWD) through wet sieving procedure, but only in the top 0‐ to 10‐cm depth. MWD had significant positive correlation with water stable aggregates (r  = 0·67, p  < 0·05). Unlike MWD, water stable aggregates were not affected by tillage and stubble management. Large macroaggregates (>2 mm) had significantly higher organic C and N concentrations than small macroaggregates (0·25–2 mm) or microaggregates (0·053–0·25 mm). We also found that N application had a significant effect on MWD and soil organic C in vertisols. It is evident that better soil aggregation was recorded under NTSR90N could have a positive influence on soil C sequestration. Our results further highlight the importance of soil aggregation and aggregate‐associated C in relation to C sequestration. Copyright © 2016 John Wiley & Sons, Ltd.     

Assessing Impacts of Crested Wheatgrass AND Native Species Establishment on Soil Characteristics in Reclaimed LAND Using Bayesian Posterior Predictive Distributions

We examined the interacting effects of drastic disturbance and re‐vegetation communities on the development of soil properties over time. We compared soil characteristics from an undisturbed reference site with reclaimed mine sites that differed by vegetation type and time since reclamation: Three sites were seeded solely with crested wheatgrass (Agropyron cristatum) (11, 16, and 29 years old), and two were seeded with native cool‐season grass mixes (14 and 26 years old). We sampled soil at two depths (0–5 and 5–15 cm) for soil macroaggregate and microaggregate weights, aggregate carbon to nitrogen (C : N) ratios, and microbial abundance. We employed a Bayesian bivariate model to account for potential correlations in soil properties across depths and compared soil properties across sites using posterior predictive distributions. We found that all reclaimed soils, regardless of vegetation type, had total aggregate weights that were similar to the undisturbed reference soil but had a larger proportion of macroaggregates than the reference soil. Aggregate C : N ratios were similar between the undisturbed reference and crested wheatgrass soils, while the reclaimed native cool‐season grass soils had lower C : N ratios in the top 5 cm. Total microbial abundance in soils seeded with crested wheatgrass was an order of magnitude lower than that in soils occupied by native species (both reclaimed and undisturbed). The presence of crested wheatgrass on the reclaimed sites alone did not differentiate all soil properties across our reclamation sites, but seeding this single, aggressive species may have contributed to maintaining different belowground characteristics on reclaimed soils. Copyright © 2015 John Wiley & Sons, Ltd.     

Rate of soil‐aggregate formation under different organic matter amendments—a short‐term incubation experiment

To improve soil structure and take advantage of several accompanying ecological benefits, it is necessary to understand the underlying processes of aggregate dynamics in soils. Our objective was to quantify macroaggregate (> 250 μm) rebuilding in soils from loess (Haplic Luvisol) with different initial soil organic C (SOC) contents and different amendments of organic matter (OM) in a short term incubation experiment. Two soils differing in C content and sampled at 0–5 and 5–25 cm soil depths were incubated after macroaggregate destruction. The following treatments were applied: (1) control (without any addition), (2) OM₁ (addition of OM: preincubated wheat straw [< 10 mm, C : N 40.6] at a rate of 4.1 g C [kg soil]^–1), and (3) OM₂ (same as (2) at a rate of 8.2 g C [kg soil]^–1). Evolution of CO₂ released from the treatments was measured continuously, and contents of different water‐stable aggregate‐size classes (> 250 μm, 250–53 μm, < 53 μm), microbial biomass, and ergosterol were determined after 7 and 28 d of incubation. Highest microbial activity was observed in the first 3 d after the OM application. With one exception, > 50% of the rebuilt macroaggregates were formed within the first 7 d after rewetting and addition of OM. However, the amount of organic C within the new macroaggregates was ≈ 2‐ to 3‐fold higher than in the original soil. The process of aggregate formation was still proceeding after 7 d of incubation, however at a lower rate. Contents of organic C within macroaggregates were decreased markedly after 28 d of incubation in the OM₁ and OM₂ treatments, suggesting that the microbial biomass (bacteria and fungi) used organic C within the newly built macroaggregates. Overall, the results confirmed for all treatments that macroaggregate formation is a rapid process and highly connected with the amount of OM added and microbial activity. However, the time of maximum aggregation after C addition depends on the soil and substrate investigated. Moreover, the results suggest that the primary macroaggregates, formed within the first 7 d, are still unstable and oversaturated with OM and therefore act as C source for microbial decomposition processes.     

Soil carbon pools of reclaimed minesoils under grass and forest landuses

Minesoils are characterized by low soil organic matter and poor soil physicochemical environment. Mine soil reclamation process has potential to restore soil fertility and sequester carbon (C) over time. Soil organic C (SOC) pool and associated soil properties were determined for reclaimed minesoils under grass and forest landuses of varied establishment year. Three grassland sites of 30, 9, and 1 years after reclamation (G30, G9, and G1) and two forest sites, 11 years after reclamation (RF) and undisturbed stand of 40 years (UF), were selected within four counties (Morgan, Muskingum, Noble, and Coshocton) of southeastern Ohio. Soil bulk density (BD) of reclaimed forest (RF) soil was significantly higher than undisturbed forest (UF) soils within 10–40 cm soil depth profile. Reclamation process increased soil pH from slightly acidic to alkaline and decreased the soil EC in both landuses. Among grassland soils, significant changes in SOC and total soil N contents were observed within 0–10 cm soil depth. SOC contents of G30 (29.7 Mg ha⁻¹) and G9 (29.5 Mg ha⁻¹) were significantly higher than G1 soils (9.11 Mg ha⁻¹). Soil N content was increased from G1 (0.95 Mg ha⁻¹) to G9 (2.00 Mg ha⁻¹) site and then the highest value was found under G30 (3.25 Mg ha⁻¹) site within 0–10 cm soil depth. UF soils had significantly higher SOC and total N content than RF soils at 0–10 and 10–20 cm soil depths. Copyright © 2009 John Wiley & Sons, Ltd.     

Long‐term cropping systems and tillage management effects on soil organic carbon stock and steady state level of C sequestration rates in a semiarid environment

A calcareous and clayey xeric Chromic Haploxerept of a long‐term experimental site in Sicily (Italy) was sampled (0–15 cm depth) under different land use management and cropping systems (CSs) to study their effect on soil aggregate stability and organic carbon (SOC). The experimental site had three tillage managements (no till [NT], dual‐layer [DL] and conventional tillage [CT]) and two CSs (durum wheat monocropping [W] and durum wheat/faba bean rotation [WB]). The annually sequestered SOC with W was 2·75‐times higher than with WB. SOC concentrations were also higher. Both NT and CT management systems were the most effective in SOC sequestration whereas with DL system no C was sequestered. The differences in SOC concentrations between NT and CT were surprisingly small. Cumulative C input of all cropping and tillage systems and the annually sequestered SOC indicated that a steady state occurred at a sequestration rate of 7·4 Mg C ha⁻¹ y⁻¹. Independent of the CSs, most of the SOC was stored in the silt and clay fraction. This fraction had a high N content which is typical for organic matter interacting with minerals. Macroaggregates (>250 µm) and large microaggregates (75–250 µm) were influenced by the treatments whereas the finest fractions were not. DL reduced the SOC in macroaggregates while NT and CT gave rise to higher SOC contents. In Mediterranean areas with Vertisols, agricultural strategies aimed at increasing the SOC contents should probably consider enhancing the proportion of coarser soil fractions so that, in the short‐term, organic C can be accumulated. Copyright © 2010 John Wiley & Sons, Ltd.     

Accumulation and composition of total organic carbon in reclaimed coal mine lands

Reclaimed coal mine lands have the potential to sequester atmospheric carbon (C); however, limited information exists for the western USA coalfields. This study was carried out on two chronosequences (BA‐C₃ grasses and DJ‐shrubs) of reclaimed sites at two surface coal mines to determine the effects of vegetation, soil texture, and lignin content on soil total organic carbon (TOC) accumulations. In the BA chronosequence, TOC increased over 26 years at an average rate of 0·52 Mg C ha⁻¹ yr⁻¹ in the 0–30 cm depth and was significantly correlated with clay content. Comparison between < 1 and 16‐year‐old stockpile soils indicated TOC content did not differ significantly. In the DJ chronosequence, TOC content in the 0–30 cm depth declined from 31·3 Mg ha⁻¹ in 5‐year‐old soils to 23·4 Mg ha⁻¹ in 16‐year‐old soils. The C:N ratios suggested that some (up to 2·0 per cent) of the TOC was potentially derived from coal particles in these reclaimed soils. Soil total N (TN) contents followed a similar trend as TOC with TOC and TN concentrations strongly correlated. Lignin contents in TOC of all reclaimed soils and topsoil stockpiles (TSs) were higher than that of nearby undisturbed soils, indicating the recalcitrant nature of TOC in reclaimed soils and/or possibly the slow recovery of lignin degrading organism. Results indicated that TOC accumulations in DJ were largely controlled by its composition, particular lignin content. In BA sites TOC accumulation was strongly influenced by both clay and lignin contents. Copyright © 2008 John Wiley & Sons, Ltd.     

Organic Farming Affects C and N in Soils Under Olive Groves in Mediterranean Areas

Under semiarid climatic conditions, intensive tillage increases soil organic matter losses, reduces soil quality, and contributes to climate change due to increased CO₂ emissions. There is a need for an agricultural management increasing soil organic matter. This paper presents the organic carbon (OC) and nitrogen (N) stocks, C:N ratio and stratification ratios (SRs) of these properties for olive groves soils under long‐term organic farming (OF), and conventional tillage (CT) in Los Pedroches valley, southern Spain. The results show that OF increased C and N stocks. The soil organic carbon (SOC) stock was 73·6 Mg ha⁻¹ in OF and 54·4 Mg ha⁻¹ in CT; and the total nitrogen (TN) stock was 7·1 Mg ha⁻¹ and 5·8 Mg ha⁻¹ for OF and CT, respectively. In the surface horizon (A: 0–16·9 cm in OF and Ap: 0–21·8 cm in CT) and Bw horizon (16·9–49·6 cm in OF and 21·8–56 cm in CT), SOC and TN concentrations and C:N ratios were higher in OF than in CT. Soil properties stratification in depth, expressed as a ratio, indicates the soil quality under different soil management systems. The SR of SOC ranged from 2·2 to 3·1 in OF and from 2·1 to 2·2 in CT. However, only SR2 (defined by Ap‐A/C) showed significant differences between CT and OF. The SR of TN showed similar trends to that of the SR of SOC. Organic farming contributes to a better soil quality and to increased carbon sequestration. Copyright © 2013 John Wiley & Sons, Ltd.     

Three hydro‐seeding revegetation techniques for soil erosion control on anthropic steep slopes

Erosion control at low–medium radioactive waste disposal sites is an important concern. A study was carried out in El Cabril (Córdoba, Spain) on two 40 per cent anthropic steep slopes in order to test the effectiveness of hydro‐seeding techniques for controlling soil erosion. Two groups of 10 m × 3 m plots were established. The treatments tested were: hydro‐seeding with the application of vegetal mulch (VM); hydro‐seeding with added humic acids (HA); hydro‐seeding with vegetal mulch and humic acids added (VM + HA); and a control without hydro‐seeding or soil amendment (C). Fifteen run‐off producing rainfall events were recorded during the study period, with intensities ranging between 2 mm h⁻¹ and 33·6 mm h⁻¹. All treatments significantly reduced runoff and soil loss (p < 0·05). The VM+HA treatment was the most effective, reducing 98·5 per cent of total soil loss. The HA treatment (97·1 per cent reduction) was also more effective than the VM treatment (94·8 per cent reduction). A great reduction in runoff and sediment yield was observed in the treated plots during the first stages after hydro‐seeding. This result may be attributed to the combined effect of: (a) the protection against raindrop impact due to the application of straw and mulch to the soil surface, and (b) a general improvement in the soil's structure brought by the organic amendments. Seven months after hydro‐seeding, an increase in the density of the plant cover could be added to the beneficial effects mentioned above. Copyright © 2000 John Wiley & Sons, Ltd.     

EFFECTS OF CRUSHED MAIZE STRAW RESIDUES ON SOIL BIOLOGICAL PROPERTIES AND SOIL RESTORATION

Agriculture soils in the Mediterranean need restoration and rehabilitation after 10 millenia of use and abuse. Maize straw residues crushed at three sizes [<1 (C1), 1–10 (C2) and >10 cm (C3)] at 5 Mg ha⁻¹ y⁻¹ and with and without urea (150 kg N ha⁻¹) were applied during a period of 3 years for the purpose of restoration of a Typic Xerofluvent located near Córdoba (Spain). The effect on the vegetal cover and biological properties (microbial biomass, soil respiration and enzymatic activities) were determined. The size of the crushed maize residues (particle size <1 cm) and N supply influenced in the evolution of soil biological properties and vegetal cover. The stimulation of microbial biomass, soil respiration, dehydrogenase, urease, β‐glucosidase, phosphatase and arylsulphatase activities was higher in C1 + N‐amended soils for 14·9%, 16·3%, 8·8%, 24·3%, 13·5%, 7·1% and 10·3%, respectively, compared with C2 + N and for 25·8%, 26·9%, 18·3%, 38·5%, 28·2%, 19·1% and 18·3%, respectively, compared with C3 + N. Vegetal cover from the C1 + N treatment was 11·4%, 17·8%, 29·4%, 37·6%, 44·9% and 75·1% greater than that in C2 + N, C3 + N, C1, C2, C3 and control soil. These results suggested that under dry climatic conditions, the application of crushed maize straw finely crushed + N fertilizers improved the soil biological properties and also favour the appearance of spontaneous vegetation, which will protect the soil and will contribute to its restoration. Consequently, the addition of the crushed maize straw finely crushed + N fertilizers may be considered a good environmental strategy for recovery of degraded soils. Copyright © 2014 John Wiley & Sons, Ltd.     

SOIL PROPERTY CHANGES FOLLOWING IRRIGATION WITH COALBED NATURAL GAS WATER: ROLE OF WATER TREATMENTS,SOIL AMENDMENTS AND LAND SUITABILITY

Saline‐sodic water is a by‐product of coalbed natural gas (CBNG) production in the Powder River Basin of Wyoming, USA and is being beneficially used in places as irrigation water. This study evaluated effects of 2 years of natural precipitation on soil properties of a hay field after the cessation of managed irrigation with CBNG water. The hay field had been irrigated with only CBNG water [CBNG(NT)], CBNG water amended with gypsum [CBNG(G)] or gypsum plus sulfur via a sulfur burner [CBNG(GSB)] in combination with soil amendments—gypsum ( +G ), elemental sulfur ( +S ), and both ( +GS ). Results indicated that infiltration rates were the lowest on fields irrigated with CBNG(NT), followed by CBNG(G) and CBNG(NT) +G treatments (12·2, 13·2, and 13·5 cm h⁻¹, respectively). The CBNG(GSB) +GS treatment had the highest infiltration rates (33·5 cm h⁻¹). By the second year, salinity and sodicity of treated soils had decreased in the A‐horizon of most CBNG‐water irrigated plots, whereas in Bt₁‐ and Bt₂‐horizons salinity generally decreased but sodicity increased; S and GS soil amended plots had higher profile salinities compared with NT and G soil treatments. Although Na⁺ leaching was observed in all fields that received soil and/or water amendments, CBNG(GSB) +GS plots had the lowest sodicity in the A‐ and Bt₁‐horizons. Effective managed irrigation requires knowledge of site‐specific soil properties, plant suitability, water chemistry, and amendments that would be needed to treat the CBNG waters and soils. This study indicates the greatest success was realized when using both soil and water amendments. Copyright © 2011 John Wiley & Sons, Ltd.     

Irrigation effects of cooling tower effluent on soil chemistry and alfalfa in the Rio Grande river basin

Development of alternative sources through wastewater reuse is important to meet water demands in arid regions. However, effects of wastewater irrigation on soil properties and crop performance must be evaluated before advocating its widespread use. Objectives of this study were to evaluate: (i) effects of prior evaporative disposal of saline‐sodic blowdown water (BW) on soil (fine‐loamy, mixed, and thermic Typic Calciorthods) properties in the disposal area, and (ii) effects of flood irrigation with three water qualities (control, BW 1X, and BW 2X) on soil salinity and alfalfa performance using a greenhouse soil column study (soil collected from same study area as objective (i)). Results indicated that although prior land disposal of BW had increased salinity and sodicity of soil, they were within the tolerance limits of the intended crop, alfalfa. Mass balance calculations indicated measured (15·6 Mg ha⁻¹) and calculated (13·2 Mg ha⁻¹) salt accumulation at the test site used for evaporative disposal were similar. Alfalfa grown using BW under greenhouse conditions produced prime quality hay and biomass yield similar to the control treatment (8·3 g column⁻¹ vs. 10·5 g column⁻¹ in control). Although 3·6 years equivalent of flood irrigation with BW 1X did not result in saline soil (BW 1X irrigated soils EC ranged from 2·2 to 3·5 dS m⁻¹), BW 2X irrigation resulted in saline soils. Sodicities of irrigated soils were greater in fine textured deep soils than coarse textured surface soils (e.g., SAR of 6·1 at 0–5 cm vs. 19·5 mmol^1/2 L^−1/2 at 30–60 cm in BW 1X), indicating the need for high solubility Ca amendments for long‐term irrigation with BW on fine texture soils within the soil profile. Copyright © 2010 John Wiley & Sons, Ltd.     

Spatiotemporal Heterogeneity of Soil Available Nitrogen During Crop Growth Stages on Mollisol Slopes of Northeast China

Spatiotemporal heterogeneity of soil available nitrogen (AN) (sum of NO₃⁻–N and NH₄⁺–N) is the essential basis for soil management and highly correlates to crop yield. Both geostatistical and traditional analyses were used to describe the spatiotemporal distribution of AN in the 0–20‐cm soil depth on typical Mollisol slopes (S1 and S2) in Northeast China. The concentration of NO₃⁻–N dynamics at slope positions was typically opposite to NH₄⁺–N. The peak values of AN typically moved from the summit of the slope to the bottom from spring to autumn and were mainly influenced by the content of NO₃⁻–N (S1, 7·9–18·9 mg kg⁻¹; S2, 1·2–103·6 mg kg⁻¹), both of NO₃⁻–N (S1, 3·9–8·3 mg kg⁻¹; S2, 2·2–28·0 mg kg⁻¹) and NH₄⁺–N (S1, 21·4–30·5 mg kg⁻¹; S2, 2·1–23·3 mg kg⁻¹), and NH₄⁺–N (S1, 10·5–28·9 mg kg⁻¹; S2, 5·0–39·0 mg kg⁻¹) in the seedling stage, vegetative growth stage, and reproductive growth stage, respectively. The spatial autocorrelation of AN was strong and was mainly influenced by structural factors during crop growth stages. This was mainly determined by soil erosion–deposition (SED) and soil temperature–moisture (STM) in the seedling stage; this was also mainly influenced by SED, STM, crop type, and crop growth in the vegetative growth stage and by early STM and early SED in the reproductive growth stage. Generally, the content of AN, NO₃⁻–N, and NH₄⁺–N on the whole slope was mainly determined by the early SED and local fertilizer application, while their spatiotemporal heterogeneity, especially the evenness, was mainly changed by SED, STM, crop growth, and crop types on the slope scale. In order to increase more crop yields, additional N fertilizer application on both the summit and the bottom during the vegetative growth stage and conservation tillage systems or additional soil amendments on the back slopes was necessary. Copyright © 2016 John Wiley & Sons, Ltd.