Neutral Soil Conditions Research Articles

Efficiency of Phosphorus Fertilizers Derived from Recycled Biogas Digestate as Applied to Maize and Ryegrass in Soils with Different pH

Three phosphorus (P) fertilizer fractions recycled from biogas digestates were tested alone and in combination for their efficiency in two agricultural surface soils with different pH: a silty sandy loam and a clay loam. The experiments were carried out in pots under greenhouse conditions, using mineral triple superphosphate (TSP) as a reference. Maize was cultivated for 50 days, followed by ryegrass cultivation for an additional 84 days in the same soil, without additional fertilization. The variables investigated were above-ground plant biomass production, plant phosphorus concentration and content, and plant available phosphorus concentration in soil. The dry matter (DM) yield of maize was increased by the organic P fertilizers equal to or more than TSP in both soils. In the neutral soil, biomass was almost doubled compared to TSP when using one of the fractions (Struvite containing P-Salt) alone or in combination with dried solid fractions. P concentration in maize cultivated in the neutral soil was not significantly different between the P fertilization treatments. However, associated with biomass increase, the total P content in maize plants was equal to or higher than that with TSP. In the acidic soil, P concentration and total P content in maize plants, as well as the calcium-acetate-lactate extractable P (CAL-P) concentration in soil, were equal to or even higher than TSP. Ryegrass DM yield was unaffected by all P fertilizers, independent of the soil, although P concentration and total P content increased in the acidic soil with all fertilizers. Our results show that recycled P fertilizers from biogas digestates are effective P fertilizer alternatives to mineral TSP for maize cultivation under acidic and neutral soil conditions. The lack of growth effects in ryegrass indicates that recycled P fertilizers do not require changes in weed control. On the other hand, P extraction by ryegrass in overfertilized acidic soils as an option for soil remediation also works in soils fertilized with biogas digestate fractions.

Effect of sulfamethazine on surface characteristics of biochar colloids and its implications for transport in porous media

Antibiotics are contaminants of emerging concern due to their potential effect on antibiotic resistance and human health. Antibiotics tend to sorb strongly to organic materials, and biochar, a high efficient agent for adsorbing and immobilizing pollutants, can thus be used for remediation of antibiotic-contaminated soil and water. The effect of ionizable antibiotics on surface characteristics and transport of biochar colloids (BC) in the environment is poorly studied. Column experiments of BC were conducted in 1 mM NaCl solution under three pH (5, 7, and 10) conditions in the presence of sulfamethazine (SMT). Additionally, the adsorption of SMT by BC and the zeta potential of BC were also studied. The experimental results showed that SMT sorption to BC was enhanced at pH 5 and 7, but reduced at pH 10. SMT sorption reduced the surface charge of BC at pH 5 and 7 due to charge shielding, but increased surface charge at pH 10 due to adsorption of the negatively charged SMT species. The mobility of BC was inhibited by SMT under acidic or neutral conditions, while enhanced by SMT under alkaline conditions, which can be well explained by the change of electrostatic repulsion between BC and sand grains. These findings imply that pH conditions played a crucial role in deciding whether the transport of BC would be promoted by SMT or not. Biochar for antibiotics remediation will be more effective under acidic and neutral soil conditions, and the mobility of BC will be less than in alkaline soils.

Tandem modified Fenton oxidation and bioremediation to degrade lubricant-contaminated soil

Several remediation technologies were evaluated in this study to efficiently break down lubricant in contaminated soil, including chemical oxidation, bioremediation, and the combination of chemical oxidation and bioremediation. The chemical oxidation batch experiment results indicated that when soil pH was acidified to 3.0, traditional Fenton's oxidation most effectively removed lubricant in contaminated soil. However, this method may cause permanent damage to the ecosystem since it requires acidic soil conditions. Further experimentation showed that by adding citric acid to traditional Fenton's oxidation, this modified Fenton's process oxidized the lubricant even more efficiently, by forming an effective chelation and preventing the production of ferric oxide precipitates, all under neutral soil conditions. In the bioremediation tests, results showed that lubricant degradation efficiencies improved by adding peptone and glutamate salt, since they served as nutrients for the soil microbes. Overall, the combination of a 56 d biopile with ammonium chloride and monosodium glutamate, followed by a modified Fenton's oxidation, was found to be the optimal degradation approach in lubricant-contaminated soil, with a promising 99.2% removal efficiency for an initial concentration of 10,000 mg kg−1 of lubricant.

Forest clearance and land use by early farmers in Europe: Insights from north Greek oral history

European prehistorians have long debated whether Neolithic farmers, especially in temperate central and northern Europe, exploited cleared woodland for short-term ‘slash-and-burn’ crop husbandry or for cultivation of ‘permanent’ gardens/fields. Because empirical evidence was scarce and rather indirect, circumstantial arguments based on the relative costs and benefits of the two rival regimes have hitherto dominated this debate, but more direct archaeobotanical proxies for Neolithic crop husbandry (based on weed ecology and crop isotopes) now favour the predominance of intensively cultivated permanent plots. At the same time, it is argued from ongoing experimental cultivation at Forchtenberg in southern Germany that short-term slash-and-burn husbandry offers much better returns on both land and labour, at least on poor soils marginal for Neolithic cereals. This paper presents oral historical evidence for mid-twentieth century clearance and subsequent long-term cultivation of mixed deciduous woodland in the Pieria region of northern Greece. These data extend the sparse European ethnographic and historical record of manual clearance for crop husbandry to deciduous woodland of the northern Mediterranean, while also providing comparative material against which to evaluate experimental results. Pierian farmers achieved good cereal yields for many years on cleared woodland, with very limited use of fire, demonstrating the viability of a permanent-cultivation regime for early farmers in the north Mediterranean, but suitable land was scarce in Pieria and informants had no experience of the alternative slash-and-burn regime. Conversely, the Forchtenberg experiments have effectively tested only the slash-and-burn regime under soil pH conditions hostile to successful long-term cultivation. Evaluation of these experiments in the light of the Pierian data suggests that long-term cultivation of cleared woodland would have offered Neolithic famers better returns than slash and burn under good or neutral soil conditions. Comparison of the likely returns of the two rival regimes thus offers no grounds for questioning archaeobotanical indications of Neolithic permanent cultivation. The Pierian and Forchtenberg data agree, however, in suggesting that the time elapsed between clearance and reliable grain harvests, under either regime, may have been long enough to pose a significant challenge to the survival of pioneer Neolithic farmers, especially if these were colonists settling beyond ‘commuting’ distance from their previous homes.

DEVELOPMENT OF AN ON-THE-GO SOIL PH MAPPING METHOD: ANALYSIS OF MEASUREMENT VARIABILITY

An automated system for mapping soil pH on-the-go has been developed, tested, and commercialized. This systemis capable of determining soil pH approximately every 10 s as it moves across a field. When georeferenced, thesemeasurements could be used to construct soil pH maps that can be involved in farm management decision process. This methodfor on-the-go soil pH mapping uses flat surface ion-selective electrodes to directly measure the pH of moist soil. The prototypesystem was evaluated in a field with artificially created areas corresponding to acidic and neutral soil conditions. Testsrevealed that the resulting standard error (measurement error superimposed on the effects of soil micro variability) was foundto be 0.38 pH. The standard laboratory procedure (measurement of soil pH in 1:1 weight-to-weight soil-water solution)performed on the same set of samples resulted in 0.24 pH standard error. In addition, various laboratory experiments showedhigh correlation between soil pH measured directly on naturally moist samples and soil solutions (R2 = 0.93 - 0.96). Fieldevaluation of automated soil pH mapping indicated that automated sampling did not introduce a significant source of errorand produced the same variance of measurements within relatively homogeneous field areas as measurements performeddirectly on manually extracted soil samples.

Preliminary Research on Seed Production and Nutrient Content for Certain Quinoa Varieties in a Saline–Sodic Soil

AbstractThe aim of the present study was to compare the potential seed yield of eight quinoa varieties, to explore their mineral composition of seeds and to identify superior varieties in two locations with different soil properties. Compared with neutral soil conditions, seed yield in the marginal (saline–sodic) soil was decreased by 45 %. Under the latter soil conditions seed yield was negatively correlated with crop density, indicating that a considerable yield loss was due to poor and uneven plant density caused by adverse soil properties. Among the varieties, ‘RU–5–PQCIP–DANIDA–UNA’ produced the highest seed yield (>20 dt ha−1) when grown under neutral soil conditions. Under marginal conditions, the above‐mentioned variety and ‘N 407’ produced seed yields up to 10 dt ha−1 whereas the rest reached yields of only about 5 dt ha−1. The majority of the varieties accumulated significantly more protein (20 %) in the seeds under saline–sodic soil conditions (lower yielding environment). The varieties originated from South America were superior in accumulating protein in the seeds at both locations. Mineral contents of calcium (Ca), magnesium (Mg), zinc (Zn) and manganese (Mn) in the seeds were significantly higher in the neutral soil. No differences were found for phosphorous (P), iron (Fe), copper (Cu) and boron (B) between the two locations. The South American varieties were again superior in mineral composition. Adaptation of certain quinoa varieties even under marginal environments seems promising for seed production and/or protein and mineral content in the seeds. Agronomic data are needed in a due course, over a higher number of locations and/or various climatic conditions.

Impact of environmental conditions on sub-surface storage tanks (part I)

The present investigation concentrates on the effects of environmental changes upon sub-surface storage tanks that are frequently used in the Niger Delta region and other parts of Nigeria for petroleum products. The research is part one of a long-term study that aims at the determination of corrosion rates of the under ground tanks within the Port Harcourt Municipality. Cast iron made storage tanks with gasoline fluid were buried under the soil at a depth of 4 m under various environment conditions. The simulated conditions include natural rain fail, temperature and acidic, alkaline and neutral soils. A control condition of neutral sea sand as base and filling materials were also investigated. After various exposure periods, the densities of the storage tanks, composition of soil, soil pH, corrosion rates and soil resistivities were determined. The experiments were repeated after every six months. Within the last three years, it has been observed that the corrosion rates of the tanks covered with cellophane materials were relatively less than those tanks that were buried directly within the soil except that of the control experiment. In addition the corrosion rates of tanks buried within the acidic environment were more than those buried within the alkaline and neutral soil conditions. Also, it was interestingly observed that the corrosion rates were generally and initially very rapid during the first year of the work, and decreased with time. Equally the water content of the soil was low. The soil resistivity increased relatively to the control sample site (G). (Journal of Applied Sciences & Environmental Management: 2002 6(2):79-84)

KINETICS OF NITROGEN LOSS IN SIMULATED WASTEWATER TREATMENT IN A SOIL-PLANT SYSTEM

We investigated the effect of nitrogen forms on the kinetics of N loss in a small-scale soil-plant system, simulating overland flow conditions with controlled alternate aerobic-anaerobic cycles. The substantial gaseous N losses of applied 15NH4+-N (18.47 to 30.65 percent) indicate the presence of favorable oxidation-reduction conditions for the simultaneous occurrence of nitrification-denitrification reactions. Gaseous loss through NH3 volatilization was unlikely in this study, due to slightly acidic to neutral soil conditions. The 15NO3--N accumulation in both the 15NH4+- and 15NO3--N treatments was negligible, indicating that 15NO3--N was not stable under the experimental conditions. The rate of gaseous N loss computed by a zero-order kinetics model was 3.93 μg 15N per gram per day for the 15NO3--N treatments and 2.09 μg 15N per gram per day for the 15NH4+-N treatments. The conversion of NO3--N to NH4+-N as a consequence of respiratory reduction was not evident in the study.