• Authors:
    • Nafziger, E. D.
    • Lauer, J. G.
    • Herzmann, D.
    • Helmers, M. J.
    • Dick, W. A.
    • Del Grosso, S. J.
    • Abendroth, L. J.
    • Kravchenko, A. N.
    • Anex, R. P., Jr.
    • Necpalova, M.
    • Sawyer, J. E.
    • Scharf, P. C.
    • Strock, J. S.
    • Villamil, M. B.
  • Source: JOURNAL OF SOIL AND WATER CONSERVATION
  • Volume: 69
  • Issue: 6
  • Year: 2014
  • Summary: Variability in soil organic carbon (SOC) results from natural and human processes interacting across time and space, and leads to large variation in the minimum difference in SOC that can be detected with a particular experimental design. Here we report a unique comparison of minimum detectable differences (MDDs) in SOC, and the estimated times required to observe those MDDs across the north central United States, calculated for the two most common SOC experiments: (1) a comparison between two treatments, e.g., moldboard plow (MP) and no-tillage (NT), using a randomized complete block design experiment; and (2) a comparison of changes in SOC over time for a particular treatment, e.g., NT, using a randomized complete block design experiment with time as an additional factor. We estimated the duration of the two experiment types required to achieve MDD through simulation of SOC dynamics. Data for the study came from 13 experimental sites located in Iowa, Illinois, Ohio, Michigan, Wisconsin, Missouri, and Minnesota. Soil organic carbon, bulk density, and texture were measured at four soil depths. Minimum detectable differences were calculated with probability of Type I error of 0.05 and probability of Type II error of 0.15. The MDDs in SOC were highly variable across the region and increased with soil depth. At 0 to 10 cm (0 to 3.9 in) soil depth, MDDs with five replications ranged from 1.04 g C kg(-1) (0.017 oz C lb(-1); 6%) to 7.15 g C kg(-1) (0.114 oz C lb(-1); 31%) for comparison of two treatments; and from 0.46 g C kg(-1) (0.007 oz C lb(-1); 3%) to 3.12 g C kg(-1) (0.050 oz C lb(-1); 13%) for SOC change over time. Large differences were also predicted in the experiment duration required to detect a difference in SOC between MP and NT (from 8 to > 100 years with five replications), or a change in SOC over time under NT management (from 11 to 71 years with five replications). At most locations, the time required to detect a change in SOC under NT was shorter than the time required to detect a difference between MP and NT. Minimum detectable difference and experiment duration decreased with the number of replications and were correlated with SOC variability and soil texture of the experimental sites, i.e., they tended to be lower in fine textured soils. Experiment duration was also reduced by increased crop productivity and the amount of residue left on the soil. The relationships and methods described here enable the design of experiments with high power of detecting differences and changes in SOC and enhance our understanding of how management practices influence SOC storage.
  • Authors:
    • Mcleod, M.
    • Schwenke, G.
    • Wilson, B. R.
    • Cowie, A.
    • Tighe, M.
    • Rabbi, S. M. F.
    • Badgery, W.
    • Baldock, J.
  • Source: AGRICULTURE ECOSYSTEMS & ENVIRONMENT
  • Volume: 197
  • Year: 2014
  • Summary: This project aimed to identify land uses and soil management practices that have significant associations with soil organic carbon (SOC) stocks (0-0.3 m) in New South Wales (NSW), Australia. The work presented in this paper is based on a one-off survey targeting key land uses and management practices of eastern NSW. Because of the nature of the work, the land uses and management combinations surveyed in different soils and climatic conditions were significantly unbalanced, and separately analyzing associations after breaking the dataset into different land uses may lead to significant increases in Type errors. Therefore, redundancy analysis (RDA) was undertaken to explore the association between explanatory variables (i.e., land uses, soil management, soil properties and environmental variables) and the variation in stocks (mass per unit area) of particulate organic carbon (POC), humic organic carbon (HOC) and resistant organic carbon (ROC) across 780 sites in eastern NSW, south eastern Australia. Results indicated that soil properties, land uses, soil management and environmental variables together could explain 52% of total variation in stocks of the SOC fractions. Specifically soil properties and environmental variables explained 42.8%, whereas land uses and management practices together explained 9.2% of the total variation in SOC fractions. A forward selection RDA was also undertaken considering soil properties and environmental variables as covariates to assess the statistical significance of land uses and management practices on stocks of POC, HOC and ROC. We found that pasture had significant positive associations on stocks of carbon fractions. Among the soil properties and environmental variables rainfall, longitude and elevation had a significant positive influence while pH and bulk density had a significantly negative influence on the HOC, POC and ROC stocks. Using a novel multivariate technique, the current work identified the land uses and soil management that had significant impact on carbon stocks in soil after accounting for influences soil properties and environmental variables.
  • Authors:
    • Varvel, G. E.
    • Wienhold, B. J.
    • Jin, V. L.
    • Schmer, M. R.
    • Follett, R. F.
  • Source: Soil Science Society of America Journal
  • Volume: 78
  • Issue: 6
  • Year: 2014
  • Summary: Demand for corn (Zea mays L.) stover as forage or as a cellulosic biofuel has increased the importance of determining the effects of stover removal on biomass production and the soil resource. Our objectives were to evaluate grain yield, soil organic C (SOC), and total soil N (0-150 cm) in a 10-yr, irrigated, continuous corn study under conventional disk tillage (CT) and notill (NT) with variable corn stover removal rates (none, medium, and high). Natural abundance C isotope compositions ( d13C) were used to determine C additions by corn (C4-C) to the soil profile and to evaluate the retention of residual C3-C. After 10 yr of management treatments, mean grain yields were 7.5 to 8.6% higher for NT when stover was removed compared with no stover removal, while grain yields were similar for CT in all stover removal treatments. Turnover of SOC occurred as C3-C stocks were replaced by C4-C in the 0- to 120-cm soil profile. Total SOC and N stocks changed mainly in surface soils (0-30 cm), with no detectable cumulative changes at 0 to 150 cm. Specifically, SOC declined after 10 yr under CT at 0 to 15 cm and was affected by residue management at 15 to 30 cm. Total soil N was greater when no stover was removed (P = 0.0073) compared with high stover removal at 0 to 15 cm. Long-term NT ameliorated medium stover removal effects by maintaining near-surface SOC levels. Results support the need to evaluate SOC cycling processes below near-surface soil layers.
  • Authors:
    • Zavattaro, L.
    • Grignani, C.
    • Krueger, J.
    • Bechini, L.
    • Baumgarten, A.
    • Schlatter, N.
    • Lehtinen, T.
    • Costamagna, C.
    • Spiegel, H.
  • Source: SOIL USE AND MANAGEMENT
  • Volume: 30
  • Issue: 4
  • Year: 2014
  • Summary: Soil organic matter (SOM) improves soil physicochemical and biological properties, and the sequestration of carbon in SOM may mitigate climate change. Soil organic carbon (SOC) often decreases in intensive cropping systems. Incorporation of crop residues (CR) may be a sustainable management practice to maintain the SOC levels and to increase soil fertility. This study quantifies the effects of CR incorporation on SOC and greenhouse gas (GHG) emissions (CO2 and N2O) in Europe using data from long-term experiments. Response ratios (RRs) for SOC and GHG emissions were calculated between CR incorporation and removal. The influence of environmental zones (ENZs), clay content and experiment duration on the RRs was investigated. We also studied how RRs of SOC and crop yields were correlated. A total of 475 RRs were derived from 39 publications. The SOC increased by 7% following CR incorporation. In contrast, in a subsample of cases, CO2 emissions were six times and N2O emissions 12 times higher following CR incorporation. The ENZ had no significant influence on RRs. For SOC concentration, soils with a clay content >35% showed 8% higher RRs compared with soils with clay contents between 18 and 35%. As the experiment progressed, RR for SOC concentration increased. For N2O emissions, RR was significantly greater in experiments with a duration <5yr compared with 11-20yr. No significant correlations were found between RR for SOC concentration and yields, but differences between sites and study durations were detected. We suggest that a long duration of crop residue incorporation is a win-win scenario under a continental climate. We conclude that CR incorporation is important for maintaining SOC, but its influence on GHG emissions should be taken into account as well.
  • Authors:
    • Mloza-Banda, H. R.
    • Cornelis, W. M.
    • Mloza-Banda, M. L.
    • Makwiza, C. N.
    • Verbist, K.
  • Source: SOIL USE AND MANAGEMENT
  • Volume: 30
  • Issue: 4
  • Year: 2014
  • Summary: A comparative study was carried out of annual ridge tillage (RT) and short-term effects of conservation agriculture (CA) on soil properties in fields of small-scale farmers. Soil samples were collected at depths of 0-10 and 10-20 cm from a total of 12 fields which had been under CA for two and four seasons, respectively, and from adjacent RT fields for direct comparisons. CA fields were converted from fields previously under continuous RT. Soil organic carbon, total nitrogen and available phosphorus were greater in CA fields while extractable potassium, pH and salt content were moderated under CA. Conversion of long-term RT to CA did not significantly influence bulk density and aggregate stability (geometric mean diameter) although structural stability was greater under CA practices. Total porosity, macroporosity and matrix porosity, and volumetric water content at saturation, field capacity and permanent wilting point did not substantively respond to tillage effects. Relative water capacity and air-water storage parameter, theta fc/POR t, were significantly greater after 4 yr of CA. Soils under CA showed greater values for field-saturated hydraulic conductivity compared with RT fields. With the highest loadings in a principal component analysis, this work suggests that variables related to volumetric water content and aeration of the soil matrix, organic carbon, available phosphorus and soil texture were the most useful indices for future field comparison of RT and CA practices.
  • Authors:
    • Mengel, D. B.
    • Hettiarachchi, G. M.
    • Khatiwada, R.
    • Fei, M.
  • Source: Journal
  • Volume: 179
  • Issue: 3
  • Year: 2014
  • Summary: Crop yields are limited primarily by unavailability of nutrients in agricultural soil. Adoption of reduced-tillage and no-tillage systems leads to stratification of nutrients in surface soil, so management of phosphorus (P) in these systems is a major issue. The objective of this research was to understand the influence of placement (broadcast vs. deep-placed P) and fertilizer source (granular vs. liquid P) on the reaction products of P under greenhouse conditions using soil columns. Phosphorus was added at a rate of 75 kg/ha to two soils: an acid soil from Manhattan, KS, and a slightly acid to neutral soil from Ottawa, KS. At 5 weeks after P application, soil pH, resin-extractable P, and speciation of P in soils were determined at different distances from the point of fertilizer application. Scanning electron microscope with energy-dispersive X-ray analysis and synchrotron-based X-ray absorption near-edge structure spectroscopy were used to understand P speciation. Results for P fertilizer sources and placement with respect to resin-extractable P showed no clear differences between the treatments except for granular broadcast and granular deep-placed treatments in the Ottawa soil. Reaction products formed after application of P in two soils showed some clear differences. The X-ray absorption near-edge structure speciation revealed that Fe-P-like forms dominated in the acidic soil, whereas adsorbed and Fe and Ca-P-like forms dominated in the neutral to slightly acid soil. No clear trends in reaction products were detected with respect to P source or the P placement method. Furthermore, scanning electron microscope with energy-dispersive X-ray analysis of incubated fertilizer granules extracted from soils at 5 weeks showed enrichment of Al, Fe, and Ca in the zones of remaining P in incubated granules, indirectly indicating that these cations enter and or remaining in the granules and begin to react with P before the granules dissolve completely.
  • Authors:
    • Hardie,Marcus
    • Clothier,Brent
    • Bound,Sally
    • Oliver,Garth
    • Close,Dugald
  • Source: Plant and Soil
  • Volume: 376
  • Issue: 1-2
  • Year: 2014
  • Summary: This study aims to (i) determine the effects of incorporating 47 Mg ha(-1) acacia green waste biochar on soil physical properties and water relations, and (ii) to explore the different mechanisms by which biochar influences soil porosity. The pore size distribution of the biochar was determined by scanning electron microscope and mercury porosimetry. Soil physical properties and water relations were determined by in situ tension infiltrometers, desorption and evaporative flux on intact cores, pressure chamber analysis at -1,500 kPa, and wet aggregate sieving. Thirty months after incorporation, biochar application had no significant effect on soil moisture content, drainable porosity between -1.0 and -10 kPa, field capacity, plant available water capacity, the van Genuchten soil water retention parameters, aggregate stability, nor the permanent wilting point. However, the biochar-amended soil had significantly higher near-saturated hydraulic conductivity, soil water content at -0.1 kPa, and significantly lower bulk density than the unamended control. Differences were attributed to the formation of large macropores (> 1,200 mu m) resulting from greater earthworm burrowing in the biochar-amended soil. We found no evidence to suggest application of biochar influenced soil porosity by either direct pore contribution, creation of accommodation pores, or improved aggregate stability.
  • Authors:
    • Soinne,Helena
    • Hovi,Jarkko
    • Tammeorg,Priit
    • Turtola,Eila
  • Source: Geoderma
  • Volume: 219
  • Year: 2014
  • Summary: Soil structure is one of the key properties affecting the productivity of soils and the environmental side effects of agricultural soils. Poor surface soil structure increases the risk of soil erosion by water and eroded clay-sized particles can carry adsorbed phosphorus (P) to the surface waters, thus inducing eutrophication of receiving waterways. Management practices, e.g. reduced tillage, used to reduce erosion can lead to enrichment of P in the uppermost soil layers, which leads to elevated risk for dissolved P loss in the runoff water. In this study, we aimed to identify whether biochar (BC) could be used to reduce clay soil erosion by improving aggregate stability. Moreover, we tested whether the BC addition would change the P sorption affinity of the soil and help to reduce the loss of dissolved P. One sandy and two clayey soils were amended with BC (0,15 and 30 t ha(-1)) and after a 3week incubation, a wet-sieving method was used to measure the release of colloidal particles and the stability of aggregates. The sorption of P onto soil surfaces was estimated with a Q/I (quantity/intensity) plot technique. The BC used here had a very low P sorption affinity and the BC addition did not increase the sorption of P in incubated soils. However, for the two clayey soils, the BC additions increased aggregate stability and reduced detachment of colloidal material. The BC thus induced changes in soil properties that could be beneficial for erosion control and thereby aid in reducing particulate P losses from agricultural fields. (c) 2014 Elsevier B.V. All rights reserved.
  • Authors:
    • Wiaux,F.
    • Cornelis,J. -T
    • Cao,W.
    • Vanclooster,M.
    • Van Oost,K.
  • Source: Geoderma
  • Volume: 216
  • Year: 2014
  • Summary: At the scale of hillslopes, a detailed mechanistic understanding of the processes controlling OC stabilization is still lacking. Here, we aimed to study the impact of geomorphic and pedogenic processes on the distribution of OC quality (ability of OC to release carbon dioxide through metabolic pathways) along an agricultural hillslope in the Belgian loess belt We collected soil cores at four topographic positions along the hillslope (summit convex shoulder, backslope and footslope). We assessed (i) cumulative soil erosion using diagnostic soil horizons and the Cs-137 techniques, (ii) OC stocks and its quality (NaOCl-resistant OC), and (iii) reactive soil mineral phases (concentration of Fe, Al and Si in specific oxalate and dithionite-citrate-bicarbonate extractants). Our results show that ongoing erosion has resulted in a small amount of reactive soil phases (e.g. Fe and Al-oxyhydroxides) in the upper first meter of the most eroded soil profile (backslope position). The erosion observations show that this is related to the truncation and rejuvenation of the backslope soil profile by bringing unweathered and calcareous loess to the soil surface. As a consequence, the potential of soil to stabilize OC by molecular interactions with soil minerals is substantially reduced by erosion when calcareous loess is reached. This was supported by the observed amount of mineral-protected OC (using NaOCl-resistant OC as an indicator) which was significantly lower at the eroded midslope than at the other slope positions. The combined effect of geomorphic and pedogenic processes thus strongly impacts the distribution of soil OC quality along the hillslope. We observed a spatial differentiation of the labile OC pool (i.e. the OC not resistant to NaOCl) along the hillslope with a significant enrichment at the depositional site. The labile OC pool contributed 64 +/- 5%, 69 +/- 5%, 40 +/- 22% and 49 +/- 6% of total OC at the footslope, backslope, convex shoulder and summit, respectively. Despite the fact that a part of this high labile OC stock at the footslope (5.8 +/- 0.2 kg OC m(-2)) can be protected from microbial degradation due to specific environmental conditions, our results suggest that a large part of this depositional OC stock has a high potential for mineralization given its quality. (C) 2013 Elsevier B.V. All rights reserved.
  • Authors:
    • He, W.
    • Liu, S.
    • Gu, R.
    • Yu, J.
    • Yan, C.
    • Teclemariam, S.
    • Liu, E.
    • Liu, Q.
  • Source: Geoderma
  • Volume: 213
  • Year: 2014
  • Summary: The influence of different tillage practices on soil organic carbon levels is more significant under long-term tillage compared to short-term tillage. Despite the great interest in the effect of no-tillage (NT) management practice on carbon sequestration, the long-term effect of NT practice on soil organic carbon and its fractions in northern China remain unclear. We evaluated the long-term effects (after 17 years) of NT and conventional tillage (CT) practices on soil organic carbon and its fractions at different depths ranging from 0 to 60 cm using a cinnamon soil in Shanxi, China. A randomised block design with three replications was used to evaluate both the tillage and its effects on the yield performance of winter wheat (Triticum aestivum L.). After 17 years, the soil organic carbon (SOC) concentration in the NT soil was greater than that of the CT soil, but only in the layer that was located between 0 and 10 cm. There was a significant accumulation of SOC (0-60 cm) in the NT soil (50.2 Mg C ha(-1)) compared to that observed in the CT soil (46.3 Mg C ha(-1)). The particulate organic matter C (POM-C), dissolved organic C (DOC), and microbial biomass C (MBC) levels in the 0-5 cm layer under NT treatment were 155%, 232%, and 63% greater, respectively, compared to the CT treatment. The POM-C, DOC, and MBC in the 5-10 cm layer under NT treatment were 67%, 123%, and 63% greater, respectively, compared to the CT treatment. Below 10 cm, the labile carbon observed in the NT treatment did not differ from that of the CT treatment. Significantly positive correlations were observed between the SOC and the labile organic C fractions. Moreover, the winter wheat (T. aestivum L) yield increased 28.9% in the NT treatment compared to the CT treatment. The data show that NT is an effective and sustainable management practice that improves carbon sequestration and increases soil fertility, resulting in higher winter wheat yields in the rainfed dryland farming areas of northern China. (C) 2013 Elsevier B.V. All rights reserved.