Cultivated Organic Soils Research Articles

Modelled impacts of mitigation measures on greenhouse gas emissions from Finnish agriculture up to 2020

Emission scenarios based on integrated quantitative modelling are a valuable tool in planning strategies for greenhouse gas mitigation. By estimating the potential of individual mitigation measures to reduce greenhouse gas emissions, resources can be targeted to the most promising policy measures. This paper reports two agricultural emission scenarios for Finland up to year 2020, one baseline scenario (Scenario 1) based on the projected agricultural production levels determined by markets and agricultural policy and one with selected mitigation measures included (Scenario 2). Measures selected for the analysis consisted of 1) keeping agricultural area at the current level, 2) decreasing the proportion of organic soils, 3) increasing the proportion of grass cultivation on organic soils and 4) supporting biogas production on farms. Starting from 2005, the emissions of nitrous oxide and methane from agriculture would decrease 2.3% in Scenario 1 by 2020 whereas the respective decrease would be 11.5% in Scenario 2. According to the results, mitigation measures targeted to cultivation of organic soils have the largest potential to reduce the emissions. Such measures would include reducing the area of cultivated organic soils and increasing the proportion of perennial crops on the remaining area.

Tillage effects on gaseous emissions from an intensively farmed organic soil in North Central Ohio

As in other drained, intensively cultivated Histosols of the world, soil subsidence is a growing concern of vegetable farmers in the muck crops region of North Central, Ohio. Subsidence in organic soils is caused primarily by aerobic degradation of soil organic matter (SOM), which in turn makes available large quantities of once bound C and N. Upon drainage and cultivation, soil C and N dynamics shift drastically. Organic soils transition from CO 2 and organic N sinks, to persistent sources, whereas CH 4 uptake capacity increases. Therefore, this study was conducted to assess the short-term (within the first year) impact of conversion of intensively tilled organic soils to no-till management. The specific objectives of this study were to: (i) compare soil moisture content, soil temperature, and greenhouse gas (GHG) emission rates from moldboard/disking (MB), no-till (NT), and bare (B) treatments in cultivated organic soils, and (ii) estimate the rate of subsidence associated with these tillage practices. Over the year, soil moisture content (SMC) was significantly higher in MB (0.90 kg kg −1) than B (0.84 kg kg −1) treatments; however NT (0.87 kg kg −1) was not significantly different from either MB or B treatments. Mean annual temperatures at 5 cm depth were significantly higher in B (16.9 °C) compared to MB (16.2 °C) and NT (15.9 °C) treatments The CO 2 emissions were not significantly different among treatments, while N 2O emissions were significantly higher from MB (96.9 kg N 2O-N ha −1 yr −1) than NT (35.8 kg N 2O-N ha −1 yr −1) plots. Both CH 4 uptake and CH 4 emission exhibited low annual flux in all treatments.

Regulatory effects of soil properties on background N2O emissions from agricultural soils in China

The background nitrous oxide (N2O) emission (BNE) from agricultural soils originates from microbial nitrification and denitrification processes of soil nitrogen supplies, excluding emissions from nitrogen fertilizers applied in the current year. It is of great necessity to quantify BNE accurately at various spatial scales since BNE contributes considerably to the overall N2O emissions from croplands. Annual BNE rates across various soil/climate regions and major cropping systems of China were determined by network observations during 2002–2006 using the static chamber technique. The observations show BNE rates ranging from 0.1 to 3.67 kg N ha−1 year−1, with a mean of 1.35 kg N ha−1 year−1. Empirical functions are derived for cultivated mineral soils and describe the dependences of annual BNE rates upon soil total nitrogen (TN) content, soil organic carbon (SOC) content, bulk density (BD) and clay fraction (CF), separately or collectively. These empirical functions provide simple approaches to scale up estimated national/regional BNE inventories using available database of soil properties surveys and cropland area statistics. The national BNE of China is estimated to be 0.114–0.184 Tg (1 Tg = 1012 g) N year−1 in 2000, with the range being due to the use of different approaches. However, the available observations of annual BNE rates do not cover the entire range of soil properties on a national scale. Further work is needed to verify the empirical models for a complete range of soil types. In addition, a predictive empirical relationship between annual BNE rates and TN or SOC is established for cultivated mineral soil at the global scale. However, the empirical models could not accurately predict the BNE rates of cultivated organic soils. Further studies are required to understand the regulatory effects of soil properties on annual BNE rates of cultivated organic soils.

Exploring the Nature of the Relationships Among Total, Extractable and Solution Phosphorus in Cultivated Organic Soils

Exploring the Nature of the Relationships Among Total, Extractable and Solution Phosphorus in Cultivated Organic Soils

Carbon stocks and sequestration potentials of agricultural soils in the federal state of Baden‐Württemberg, SW Germany

AbstractSoil organic carbon (SOC) inventories are important tools for studying the effects of land‐use and climate change and evaluating climate‐change policies. A detailed inventory of SOC in the agricultural soils of the federal state of Baden‐Württemberg was therefore prepared based on the highest‐resolution geo‐referenced soil, land‐use, and climate data (BÜK200 inventory). In order to estimate the quality of different approaches, C inventories of the region were also prepared based on data from the National Inventory Report (UBA, 2003) and by applying the IPCC (1997) method to the two data sets. Finally, the BÜK200 inventory was used to estimate potentials of no‐tillage agriculture (NT) and peatland restoration to contribute to C sequestration and greenhouse‐gas (GHG)‐emission mitigation since both measures are discussed in this context. Scenario assumptions were change to NT on 40% of the cropland and restoration of 50% of cultivated peatlands within 20 years.On average, grasslands contained 9.5 kg C m–2 to 0.3 m depth as compared to only 6.0 kg C m–2 under cropland, indicating strong land‐use effects. The SOC content depended strongly on waterlogging and elevation, thus reflecting reduced C mineralization under aquic moisture regimes and low temperatures. Comparison of the BÜK200 inventory with the approach used for UBA (2003) showed high inconsistencies due to map resolution and SOC contents, whereas the IPCC method led to fairly good agreements. Results on the simulated effects of NT and peatland restoration suggested that 5%–14% of total agricultural GHG emissions could be abated with NT whereas peat restoration appeared to have a minor mitigation potential (0.2%–2.7%) because the total area of cultivated organic soils was too small to have larger impact.

Relationships between Radarsat SAR data and surface moisture content of agricultural organic soils

A time series of 10 C-band fine beam images were acquired over the West Monteregie region (Quebec) in 1999 to examine the potential of Radarsat to detect surface moisture content of cultivated organic soils. Soil moisture data were simultaneously collected from 10 fields cropped to carrots, potatoes, lettuces, and onions. The analysis was conducted at two levels: (i) a temporal scale (daily average value); and (ii) a spatial scale (10 fields). At the first level, we found that the average radar backscatter ) was quite well correlated to the seasonal change of the average moisture content (R 2=0.75), although the dates with a strong vegetation growth decreased the relationship. Comparison with data acquired for mineral soils indicates that organic soils exhibit a lower backscatter, especially at lower moisture content levels, suggesting that soil types should be considered prior to map soil moisture changes. At the field scale, the relationship was much lower (R 2=0.44). The quality of the relationship was proportional to vegetation cover and appeared to be crop-dependent. Best results were obtained with onions and carrots. Considering only bare organic soils, the result was satisfactory (R 2=0.79) and similar to those published on mineral soils.

Geostatistics of near-surface moisture in bare cultivated organic soils

The aim of this study was to characterise fine scale patterns of organic soil moisture content in the top 5 cm by means of semi-variogram modelling. Soil moisture content was observed along a transect on 2 occasions, early in the 1999 growing season to avoid any influences originating from vegetation and cultural practices. Soil moisture values were found to be normally distributed and were not significantly correlated with the soil organic matter content. Many similarities were depicted between the exponential semi-variograms characteristics of this study and another one in mineral soils, reported in the literature, except for the much higher sills associated with organic soils. Of particular interest were similar correlation lengths, indicating that a correlation range of the order of 100 m should be expected for mineral soils and for the level of moisture and organic matter contents found in this study.

Agricultural improvement of cultivated organic soils II. Effects of liming and deep cultivation on soil properties and root development

Abstract. The effect of liming and deep cultivation on soil properties and root development was investigated in two cultivated shallow fen peats resting on acid gyttja (lake mud) soils. Root growth was in general dependent on soil pH and aluminium content of the soil. A soil pH (H2O) below 5 adversely affected roots and a pH below 4 severely restricted root growth. Liming of the topsoil or the subsoil and to some extent deep cultivation improved root growth. Increased rooting depth made it possible for plants to utilize soil water to a greater depth in the profile and to support a larger crop yield.

Agricultural improvement of cultivated organic soils I. Effects of deep cultivation, liming, irrigation and P‐fertilization on crop yields

Abstract. Four field experiments were carried out on cultivated shallow fen peat overlying acid gyttja (lake mud) soil. The accessibility of the generally ample supply of physically available water was restricted by a limited root depth caused by low pH and high levels of aluminium in the subsoil. In order to improve the nutrient status and the crop water supply of the soils liming, deep cultivation, P‐fertilization and irrigation were tested in field experiments comprising these four main treatments and their combinations. Liming and P‐fertilization of the topsoil, irrigation and deep cultivation in combination with deep liming improved crop yields. Deep cultivation without liming had a negative effect on yield in most years.

Water Repellence of Cultivated Organic Soils

Abstract A range of cultivated organic soils was studied with respect to water repellence. All soils were wettable above a water content of approximately 30-50 % (v/v). Below this critical content, most soils showed a varying degree of water repellence. Well decomposed peat had lower infiltration rates than moderately decomposed peat. Lightly crushing the peat soil before measurement increased the infiltration rate compared with an undisturbed soil sample. In tests with aqueous ethanol of different molarity, peat soils showed greater repellence than gyttja soils. All moss peat layers were extremely water repellent and fen peats slightly less repellent. Water repellence did not occur on gyttja clay and marl gyttja.

The fate of some pesticides in Finnish cultivated soils

The persistence and movement of methabenzthiazuron, metazachlor, trifluralin, iprodione, fenitrothion, fenvalerate and furathiocarb was studied in one growing season in cultivated clay, finesand and organic soils in southern Finland. Trifluralin was studied for two growing seasons. Methabenzthiazuron was the most mobile pesticide and metazachlor was almost as much mobile. They leached at least 15 cm in a month. Fenitrothion and fenvalerate were the most immobile. Trifluralin was the most and fenitrothion the least persistent. The concentrations of iprodione and fenvalerate in the top soils increased towards the autumn, presumably due to leaching of pesticides from plants. The residues of trifluralin measured in the surface layer of the mineral soils at the end of the growing season might have been harfmul to plants sensitive to trifluralin. The residues of trifluralin in the peat soil surface 1.5 years after the treatment were still high. Also methabenzthiazuron, iprodine and fenvalerate residues may in all probability have been detected in the following spring. If the half-life of a pesticide is over 80 - 100 days, it is likely that residues of it may be found in the spring following the application in cultivated Finnish soils.

The influence of soil properties, total copper, iron, manganese, and zinc on the yield of oat, carrot, onion and lettuce

Abstract As part of a series of studies for evolving useful soil tests for Cu, Fe, Mn and Zn in cultivated organic soils, 55 such soils from eastern Canada were used in a greenhouse study. Oat, carrot, onion, and all three followed by lettuce were grown in a greenhouse in 2 L pots containing 1.8 L of soil. The moisture, fertilization and temperature conditions provided were known to be non‐Hmiting. And yet, yields of crops, on per kg soil basis, generally correlated negatively with certain soil properties. The more decomposed and denser soils tended to be less productive, even though more soil, but not significantly less water, was accessible to the roots in such soils than in the case of less decomposed, more open soils. In contrast, crop yield per unit soil volume (1.8 L) basis showed a negative effect of water holding capacity on yield of oat, and positive effect of pH on carrot yield. No other correlations were significant. The results thus corroborated the practice of basing soil tests and fertilizer...

THE EFFECT OF USING COPPER FOR MITIGATING HISTOSOL SUBSIDENCE ON

As a sequel to earlier studies on the suitability of using moderate and nonbiocidial amounts of Cu for slowing down the undesirably fast degradation and resultant subsidence of cultivated organic soils, this greenhouse investigation showed that the yield, Cu status, and nutrition of minicarrots, carrots, and onions grown in an organic soil (B) containing 1060 ppm (wt/wt) Cu were similar to those grown in an organic soil (A) containing 136 ppm Cu. The long-term investigation also simulated a situation where organic soil B, containing about three times the Cu required for mitigating the subsidence by about 50%, is mixed with a mineral sublayer in 1:1 vol/vol proportion for agronomic convenience. Organic soil B so mixed individually with sand, shell-rich deposit (soil S), gyttja (soil G), or a clay (soil Cl) sublayer thus produced soils B1, S1, G1, and Cl1, respectively. Minicarrots, carrots, and onions grown in these four mixtures also appeared not to be adversely affected by the Cu added to them by soil B. Soils S2, G2, and Cl, obtained by amending soils S, G, and Cl, respectively, contained Cu in excess of the equivalent of 5% of their cation exchange capacity. As in previous studies, the Cu in these soils tended to adversely affect the yields or Cu status or nutrition of minicarrots, carrots, and onions grown in them. However, the severity of the adverse effects appeared to decline with time.

THE ESTABLISHMENT OF SYNCHRONY BETWEEN SUBSURFACE LAYERS AND ESTIMATION OF OVERALL SUBSIDENCE OF CULTIVATED ORGANIC SOILS BY A PALYNOLOGICAL METHOD

Pollen profiles of Tsuga canadensis in a virgin and two cultivated areas of a bog revealed the bimodal distribution characterized by easily recognizable minima, thus establishing synchrony between specific layers of the three organic soil profiles. This knowledge allowed estimation of overall subsidence of the cultivated soils, and would facilitate comparisons between subsurface layers now determinable as synchronous. Such comparisons should help determine the extent and depth of temporal biochemical and physical changes in subsurface layers of cultivated organic soils.

Stream Transport of Nutrients Through a Wetland

AbstractThe potential of managed wetlands to remove nutrients from agricultural drainage water was investigated by hydrographic and nutrient analyses for 2 years in Oak Orchard Creek, N.Y., which drains in series cultivated Histosols (upstream) and wetlands managed for waterfowl (downstream). Three stations were established, two above and one below the wetland. Creek‐water pH averaged about 7.4. Dissolved concentrations (mg/liter) ranged from 0 to 19 for N, 0.009 to 2 for P, 2 to 10 for K, 45 to 411 for Ca, and 10 to 102 for C, and were highest just below the cultivated areas. Eighty to ninety percent of the creek load was carried from December through March. The cultivated organic soils were a rich source of nutrients to the creek, and the managed wetlands acted as net nutrient sinks for N and P during the 2nd year only, when flow through the system was about half that in the 1st year. However, on an areal basis, much less nutrient material was lost from the wetlands than from other parts of the basin. The creek system seems to be N‐limited; P loads exceeded N loads during late summer. It is suggested that nutrient retention by wetlands depends on past nutrient history and current regulation of water movement through the system.

THE EFFECT OF RESIDUAL FERTILIZER COPPER ON AMMONIFICATION, NITRIFICATION AND PROTEOLYTIC POPULATION IN SOME ORGANIC SOILS

As a part of attempts at examining the suitability of using moderate amounts of Cu for mitigating the undesirably fast decomposition and subsidence of some organic soils, this investigation revealed that both total and DTPA-TEA-extractable Cu contents of 14 samples of cultivated organic soils correlated negatively with the total microbial population counted on soil extract-acitidione-gelatin agar plates and positively with the percentage of that population capable of extracellular proteolysis. On the other hand, the concentrations of both total and extractable Cu did not correlate with either the total number of proteolytic organisms counted, or the capacities of the soils for ammonification and nitrification. The results are, therefore, in accord with the belief that Cu curtails the decomposition of organic soils primarily through inactivation of accumulated soil enzymes, but not through direct toxic effects on the general soil microbial population.

Ochre and Subsurface Drainage in Cultivated Organic Soils of Willard Marsh, Ohio

ABSTRACT SEDIMENTS in subsurface drainage systems were characterized in cultivated organic soils of the Willard Marsh. On-site inspections of sediment-affected drains were made, and soil permeability to water was measured in the field. Chemical analyses were made on drain sedi-ments and soil for ferrous iron, total iron, manganese, aluminum, organic matter, mineral content and pH. The permeability of the subsoil was quite low, rang-ing from 0.1 to 0.4 cm/hr. The plow layer permeability varied from about 1.5 to 2.5 cm/hr. Sediments from drains ranged from 100 percent organic material to a mixture of organic and mineral materials. A maximum iron content of 35 percent was found in an ochreous sediment/Ferrous iron in the soil increased markedly below drain depth. Subsurface drainage appears to be impeded by two principle factors: One is the low perme-ability of the subsoil and the other is the accumula-tion of organic sediments and ochre (iron) in drains.