Increasing Soil Moisture Content Research Articles

Integrated soil, water and agronomic management effects on crop productivity and selected soil properties in Western Ethiopia

Land degradation is a major challenge limiting crop production in Ethiopia. Integrated soil and water conservation is widely applied as a means to reverse the trend and increase productivity. This study investigated the effects of such integrated approaches at two sites, Jeldu and Diga, in Western Ethiopia. A split plot design with physical soil and water conservation in the main plots and agronomic practices in the sub plots was employed. Maize (Zea mays L.) followed by groundnut (Arachis hypogaea L.) at Diga, and wheat (Triticum aestivum) followed by faba bean (Vicia faba L.) were the test crops. Surface soils were sampled before sowing and after the crop harvest, and analyzed for selected parameters. Soil moisture content during the growing period was also monitored. The use of soil bund increased soil moisture content, and significantly (P < 0.05) increased days to flowering and maturity, kernel weight and harvest index, grain yield of the test crops, with the exception of maize. The improved agronomic practices (intercropping, fertilization and row planting) significantly (P < 0.05) increased grain yield of all the test crops. The effect of the treatments on soil parameters may require longer time to be evident. Although the increase in crop yield due to soil bund and the improved agronomic practices is eminent, economic analysis is necessary before recommending the widespread use of the improved options.

Effects of soil moisture content on the growth and physiological status of ginger (Zingiber officinale Roscoe)

Ginger (Zingiber officinale Roscoe), one of the most valuable economic plants from the Zingiberaceae family, is used worldwide as a spice and flavoring agent in the beverage, bakery, confectionary, and pharmaceutical industries. Soil moisture is one of the most important constraints in ginger cultivation. In the present paper, the phenotype, physiology, biochemistry, and expression difference of genes coding for key enzyme for endogenous hormone metabolism in ginger under different soil moisture conditions (water-filled pore space, WFPS) were measured. Our results indicated that with the increase of soil moisture content, the ramet number of Z. officinale gradually increased, and the ramet number increased to 26.7 ± 3.7 at 40% humidity. However, the stem height, stem diameter, and the relative chlorophyll content were highest at 25% humidity. Similarly, the activities of superoxide dismutase (SOD) and peroxidase (POD) as well as the contents of abscisic acid (ABA) and ethylene (Eth) content remained relatively low at 25% humidity, whereas they were relatively high at lower moisture (10%) and higher moisture (30–40%) levels. In addition, the expression patterns of key enzyme-coding genes involved in ABA synthesis and Eth metabolism were analyzed to elucidate the effect of soil moisture on ginger cultivation. The results showed that the expression of the genes were in accordance with the variation of ABA and Eth under different soil moisture levels. In sum, soil moisture significantly affects the growth of Z. officinale, and 25% soil humidity is suitable for the growth of Z. officinale.

Interactive effects of plastic film mulching with supplemental irrigation on winter wheat photosynthesis, chlorophyll fluorescence and yield under simulated precipitation conditions

Water shortages continuously threaten agricultural productivity in semi-arid regions. Efficient water-saving management practices urgently need to be developed. In the present study, a mobile rain shelter was used with two cultivation modes: (1) the ridge furrow (R) rainfall harvesting system; and (2) traditional flat planting (F). In addition, two supplemental irrigation levels (150, 75 mm) and three precipitation levels (1: 275, 2: 200, 3: 125 mm) were included in this study. We demonstrated that the R system with 150 mm supplemental irrigation and 200 mm simulated rainfall can significantly improve winter wheat net photosynthesis rate (Pn), electron transport rate (ETR), effective quantum yield of PS II (ΦpsII), maximum quantum efficiency of PSII (Fv/Fm), variable fluorescence (Fv), energy transformation potential of PSII (Fv/Fo), and leaf photosynthetic performance index of PSⅡ (Fv/Fmʹ), at the jointing, flowering, and later stage of grain filling. These improvements were due to significantly increased soil moisture content, total chlorophyll ab contents (13.1%), and chlorophyll stability index (88.3%) of flag leaves, and decreased (32.7%) evapotranspiration (ET) at field scales and soil temperature, all of which increased the grain yield (18.9%) and water use efficiency (WUE, 75.8%) compared with traditional flat planting. The chlorophyll fluorescence parameters of winter wheat were significantly positively correlated with the Pn, total Chl, WUE, and grain yield (except ET). These results suggest that the R system with 150 mm supplemental irrigation and 200 mm simulated rainfall was the best cultivation practice for improving photosynthesis, chlorophyll fluorescence, WUE, and yield of winter wheat in semi-arid regions.

Análise da dinâmica da água em um solo não saturado sob condições de chuvas simuladas

O semiárido brasileiro apresenta solos com pequena espessura e pouca permeabilidade, onde a água pluvial permanece na camada superficial do solo e rapidamente evapora. Embora essa condição acarrete um nível freático raso (pouco profundo), ele desempenha um papel fundamental nos períodos de estiagem, sobretudo para a vegetação nativa do semiárido (Caatinga). O objetivo principal deste trabalho é estimar o efeito da intensidade de precipitação na dinâmica da água no solo, em uma região semiárida do estado de Pernambuco, Brasil. Foi realizada a modelagem matemática unidimensional da dinâmica da água no solo usando o software 1D-Hydrus. Foram utilizadas quatro diferentes taxas de precipitação e tempos de duração dos eventos chuvosos, baseados em valores medidos in loco. A maior parte das chuvas precipitadas ficaram contidas nos primeiros 15 centímetros do solo. Os resultados indicaram que os eventos pluviométricos intensos e de menor duração determinam maiores valores na umidade superficial do solo. Eventos menos intensos e de maior duração acarretam em um aumento do teor de umidade do solo por um período de tempo mais prolongado, aproximadamente por 3 dias, independente da intensidade de precipitação. Os eventos pluviométricos aumentam a umidade volumétrica superficial do solo rapidamente, porém quando cessam, a umidade volumétrica retorna aos valores iniciais lentamente, cerca de 10 dias após os eventos chuvosos.

Field investigations to determine the thermal performance of earth air tunnel heat exchanger with dry and wet soil: Energy and exergetic analysis

Earth air tunnel heat exchanger (EATHE) systems are inadequate to meet the thermal comfort requirements in semi-arid regions as they require large pipe lengths. The effectiveness and performance of such system can be increased by increasing soil moisture content, making as wet soil configuration. In the present work, the thermal performance of the EATHE system with dry and wet soil has been evaluated during the peak summer season. Further, the thermal behavior of these two EATHE systems has been compared on the basis of temperature of air flowing through buried pipes at different sections along the length. For the same a theoretical model is developed and validated with experimental results and found in good agreement with an error ranging from 2.44% to 10.85%. Moreover, the exergetic analysis has been carried outto investigate the work potential and scope of maximum utilization of energy. Results reveal that thepipe length can be reduced by 12–14 m with wet EATHE system as compared to dry EATHE system for the same cooling performance. The second law analysis shows that the maximum exergetic efficiency is 52.25% and 53.18% for dry and wet soil EATHE systems respectively.

Transition from a warm and dry to a cold and wet climate in NE China across the Holocene

Northeast (NE) China lies in the northernmost part of the East Asian Summer monsoon (EASM) region. Although a series of Holocene climatic records have been obtained from lakes and peats in this region, the Holocene hydrological history and its controls remain unclear. More specifically, it is currently debated whether NE China experienced a dry or wet climate during the early Holocene. Here we reconstruct changes in mean annual air temperature and peat soil moisture across the last ∼13,000 year BP using samples from the Gushantun and Hani peat, located in NE China. Our approach is based on the distribution of bacterial branched glycerol dialkyl glycerol tetraethers (brGDGTs) and the abundance of the archaeal isoprenoidal (iso)GDGT crenarchaeol. Using the recently developed peat-specific MAATpeat temperature calibration we find that NE China experienced a relatively warm early Holocene (∼5–7 °C warmer than today), followed by a cooling trend towards modern-day values during the mid- and late Holocene. Moreover, crenarchaeol concentrations, brGDGT-based pH values, and the distribution of 6-methyl brGDGTs, all indicate an increase in soil moisture content from the early to late Holocene in both peats, which is largely consistent with other data from NE China. This trend towards increasing soil moisture/wetter conditions across the Holocene in NE China records contrasts with the trends observed in other parts of the EASM region, which exhibit an early and/or mid-Holocene moisture/precipitation maximum. However, the Holocene soil moisture variations and temperature–moisture relationships (warm–dry and cold–wet) observed in NE China are similar to those observed in the core area of arid central Asia which is dominated by the westerlies. We therefore propose that an increase in the intensity of the westerlies across the Holocene, driven by increasing winter insolation, expanding Arctic sea ice extent and the enhanced Okhotsk High, caused an increase in moisture during the late Holocene in NE China.

Effect of soil moisture during stratification on dormancy release in seeds of five common weed species

SummaryAlthough the effects of cold stratification on the release of physiological dormancy in seeds have been studied extensively, knowledge of the role of soil moisture content on seed dormancy release during cold stratification is limited. Our study determined seed dormancy characteristics and the effect of soil moisture content on seed dormancy breakage during cold stratification in the five common weed species Amaranthus retroflexus, Chenopodium album, Chenopodium hybridum, Plantago lanceolata and Setaria glauca. Seeds of all five species were dormant at the time of harvest and their germination response to light and temperature varied. Soil moisture content had a significant effect on seed dormancy release of all species except P. lanceolata. Germination percentage of A. retroflexus, C. album, C. hybridum increased and then decreased as soil moisture content increased, regardless of germination test temperature. The optimal soil moisture content and seed moisture content for dormancy breakage of A. retroflexus, C. album, C. hybridum were 8%, 12%, 8% and 22.0%, 37.7%, 25.7% respectively. Dry storage (after‐ripening) significantly increased germination of S. glauca. Moreover, increasing soil moisture content first slowed and then increased dormancy breakage in S. glauca. These results suggest that data on soil moisture content should be incorporated into models that predict weed seed dormancy breakage and timing of seedling emergence as well as those for weed management.

Effects of soil moisture on dust emission from 2011 to 2015 observed over the Horqin Sandy Land area, China

Abstract Using the observational data of dust concentrations and meteorological parameters from 2011 to 2015, the effects of soil moisture and air humidity on dust emission were studied at long (monthly) and short (several days or hours) time scales over the Horqin Sandy Land area, Inner Mongolia of China. The results show that the monthly mean dust concentrations and dust fluxes within the near-surface layer had no obvious relationship with the monthly mean soil moisture content but had a slightly negative correlation with monthly mean air relative humidity from 2011 to 2015. The daily mean soil moisture exhibited a significantly negative correlation with the daily mean dust concentrations and dust fluxes, as soil moisture changed obviously. However, such negative correlation between soil moisture and dust emission disappeared on dust blowing days. Additionally, the effect of soil moisture on an important parameter for dust emission, the threshold friction velocity (u∗t), was investigated during several saltation-bombardment and/or aggregation-disintegration dust emission (SADE) events. Under dry soil conditions, the values of u∗t were not influenced by soil moisture content; however, when the soil moisture content was high, the values of u∗t increased with increasing soil moisture content.

Causation Analysis and Improvement Strategy for Reduced Pendimethalin Herbicidal Activity in the Field after Encapsulation in Polyurea.

To reduce the amount of organic solvents in pendimethalin emulsifiable concentrate (EC), small-size microcapsules (S-MCs) and large-size microcapsules (L-MCs) were prepared with polyurea as a wall material. Petri-dish bioassays were carried out to investigate the bioactivity of formulations and the influence of both organic matter and moisture. The relationships between degradation and the biological activity of three pendimethalin formulations in the soil were investigated, and field experiments were executed to verify the laboratory results. The laboratory tests showed the following: (1) the bioactivity of EC and S-MCs was similar and greater than that of L-MCs; (2) organic matter could reduce the bioactivity of MCs and EC, and the impact of organic matter on L-MCs was greater; (3) increased soil moisture content had no significant effect on the bioactivity of EC but slightly reduced that of the MCs; and (4) the L-MCs showed significantly more prolonged residual and effective persistence in the soil than did EC and S-MCs. However, the field experiments indicated that the herbicidal efficacies of L-MCs at the early and late stages were both lower than those of EC. Comprehensive analysis of the results indicated that the main reason that the herbicidal efficacy of L-MCs was lower than that of EC in the field was that L-MCs missed the optimal herbicidal periods due to the slow-release characteristics of L-MCs. The S-MCs had both similar release rates and herbicidal efficacy in the field as EC. Therefore, to develop a good pesticide formulation, the occurrence and damage characteristic of pests must be considered.

Mineralization of organic carbon and nitrogen in semi-arid soils under organic and inorganic fertilization

Abstract Although compost is added to soils to improve their nutritive status and properties; yet upon its decomposition, considerable amounts of CO2 might be emitted to the atmosphere causing hazardous environmental risks. Investigating the mineralization of compost applied to a sandy soil and a silty clay one of low organic-C content in the green house for 90 days under soil moisture contents of 75 or 100% of FC was considered. Efflux rate of CO2 decreased considerably for one day in the sandy soil after application of the compost; beyond which showed an almost constant rate. In the silty clay soil, the efflux rate decreased obviously to achieve non detectable value 3 days later. Even in soils amended with mineral N-fertilizer, CO2 emissions were valued while decreased with time. By the end of the incubation time, the rate of C-mineralization was significantly higher in the sandy soil compared with the silty clay one. Increasing soil moisture content from 70 to 100% of the field capacity led to further increases in rates of CO2 efflux as well as org-C mineralization. The amount of N mineralized in the sandy soil was 1.7 times higher than its content in the silt clay one at the FC and 1.1 times in case of 70% of FC. In conclusion, a reversible equilibrated process between decomposition of soil organic matter and buildup of more stable organic components might exist at the same time.

Effect of Cropping Sequence on Agricultural Crops: Implications for Productivity and Utilization of Natural Resources

Offensive land uses system with continuous growing of similar crops on the same land largely affect soil physical condition, crop development and had big concerns on long term adverse effects of environmental pollution. The choice of sequence highly based on agricultural system, finance and environmental condition. Conventional monoculture agricultural systems can reduce the soil organic matter contents and structures. The accumulation of crop residues with frequent inclusion of pulse crops in a rotation is vital to improve the biochemical and physical properties of the soil via increasing the labile of organic matter. Surface residue of crops is one of the most effective erosion control measures and increase soil moisture content. Different crops have dissimilar growth and development periods thus, one crop may provide protection from erosive forces during a period of the year and the other may not. Besides, crop rotation combines with different management practices are essential to improve the physical, chemical, biological properties of the soil and thereby control erosion and to maximize crop yield by maintain soil moisture and control disease and pests infestation.

Nitrous oxide fluxes and nitrifier and denitrifier communites as affected by dry-wet cycles in long term fertilized paddy soils

Drying and rewetting events of soil represents a common physiological stress for soil microbial communities. We investigated the effect of alternate drying-rewetting cycles on N2O emissions and soil microbial communities in jar experiments with soil samples. The results showed that instant flooding and air-drying moments are two important steps of soil drying and rewetting periods influencing soil microbial communities and N2O emissions. N2O fluxes in the air dry (AD) steps were always higher than those in the instant flooding (IF) steps, especially in the early stages of AD and IF. The soil treated with long-term organic matter and chemical fertilizer promoted N2O emissions but inhibited the N2O release from newly applied urea when soil went through drying and rewetting events. Soil moisture content(s) also significantly affected the growth of ammonia oxidiser and denitrifier communities, with the functional gene abundance increasing with increasing soil moisture content. While comparing first and second cycles, N2O fluxes were six times higher in the first cycle than in the second cycle. It is concluded that sudden changes in moisture condition influenced the N2O flux, and nitrifier and denitrifier functional genes by affecting the growth of ammonia oxidiser and denitrifier communities.

Influence of soil moisture content on assessment of bulk density with combined frequency domain reflectometry and visible and near infrared spectroscopy under semi field conditions

The potential of combining frequency domain reflectometry (FDR) and visible and near infrared spectroscopy (vis-NIRS) was shown to successfully assess soil bulk density (BD). However, the accuracy of both sensing tools was reported to be influenced by the soil moisture content (MC). The aim of the paper is to evaluate the influence of soil MC level on accuracy of BD assessment under semi field conditions by the combination of FDR and vis-NIRS data. Measurements of volumetric moisture content (θv) in the field and gravimetric moisture content (ω) in the laboratory using a FDR and a vis-NIRS (350–2500nm) techniques were conducted in five arable fields of different soil texture classes in Silsoe, Bedfordshire, UK. In order to account for different MC levels, three measurement campaigns were carried out during the period from July 2011 to October 2012, where a total of 300 soil samples were used, representing three natural MC levels of low (L1), medium (L2) and high (L3). L1, L2 and L3 datasets were subjected to artificial neural network (ANN) analysis to predict ω and θv based on fusion of vis-NIRS spectra and FDR output voltage, and subsequently the predicted values were substituted into a model to assess BD.Results showed that MC has large influence on both the vis-NIRS and FDR sensors for measuring ω and θv, respectively. The accuracy of BD assessment improved with soil MC increase, with root mean square error of prediction (RMSEp) values of 0.079, 0.072 and 0.061 g cm−3, for average ω of 0.106 (L1), 0.197 (L2) and 0.28 (L3) gg−1, respectively. The accuracy of θv measurement with the FDR depended on ensuring good contact with the soil, which is not the case for dry soil conditions, at which accuracy of θv measurement and BD assessment was deteriorated. It is recommended to set an optimal MC range (depending of soil texture), over which precise soil BD estimation can be certain.

Pengaruh Takaran Pupuk Guano dan Biochar terhadap Pertumbuhan dan Hasil Tanaman Kacang Merah (Phaseolus vulgaris L.) di Lahan Kering pada Dataran Menengah

Penelitian dilaksanakan untuk mengetahui pengaruh takaran pupuk guano dan biochar terhadap pertumbuhan dan hasil tanaman kacang merah pada dataran menengah, di kebun percobaan Faperta Universitas Timor pada bulan Februari – April 2017, menggunakan Rancangan Acak Kelompok faktorial 3 x 3 diulang 3 kali. Faktor pertama takaran guano yang terdiri dari 3 taraf yaitu tanpa guano, guano 5 t/ha dan guano 10 t/ha sedangkan faktor kedua takaran biochar yang terdiri dari 3 taraf yaitu tanpa biochar, biochar 5 t/ha dan biochar 10 t/ha. Hasil penelitian menunjukkan tidak terjadi interaksi antara aplikasi pupuk guano dengan biochar. Pemberian guano 10 t/ha secara nyata meningkatkan kadar lengas tanah (17,62%), luas daun (8.595 cm2), jumlah bintil akar (175,11), bobot kering akar (0,70 g), rasio tajuk akar (16,24), jumlah polong pertanaman (2,86), jumlah biji per polong (2,86), bobot kering biji (7,24 g) dan bobot biji per petak (1,17 t/ha) dengan presentase peningkatan hasil sebesar 31,1%. Peningkatan level pemberian Biochar tidak menunjukkan beda nyata antar level perlakuan, tetapi cenderung meningkatkan pertumbuhan dan hasil tanaman. ©2017 dipublikasikan oleh Savana Cendana.

Manganese oxide affects nitrification and N2O emissions in a subtropical paddy soil with variable water regimes

SummaryCrop management‐induced redox cycles lead to the formation of distinct soil layers that characterize manganese (Mn) distribution or redistribution in rice (Oryza sativa L.) based ecosystems. We studied the effect of Mn oxides on soil nitrification and N2O emissions to validate the hypothesis that Mn oxides affect the soil's nitrification and denitrification processes. Subtropical paddy soil with three different water regimes (50, 100 and 200% of soil water‐holding capacity (WHC)) was treated with 3% birnessite (Mn oxide) or left untreated. The nitrification process was simulated with zero‐ or first‐order kinetic models and N2O emissions were also measured. The maximum net rates of soil nitrification (Va1) decreased significantly with increasing soil moisture contents (F = 184.8; P &lt; 0.001), and so did the average net rates of soil nitrification (Va2) (F = 6.96; P = 0.008). Manganese oxide significantly decreased Va1 (F = 474.7; P &lt; 0.001), whereas it had no significant effects on Va2 (F = 0.26; P = 0.62). Manganese oxide changed the best fitting nitrification kinetic model from first‐ to zero‐order for both 50 and 200% WHC, but it had no effect at 100% WHC. The maximum rates of emission of N2O significantly increased with increasing soil water contents (F = 15 007; P &lt; 0.001). Manganese oxide retarded the maximum rate of N2O emission at 100% WHC, whereas it depressed the rate from 1084 to 225 μg N kg−1 day−1 at 200% WHC (F = 7494; P &lt; 0.001). The results indicate that the effects of Mn oxide on regulating nitrification and N2O emissions are associated with water regime‐dictated redox potential, and might have important implications for regulating N cycling in rice‐based ecosystems.Highlights Effect of manganese oxide on nitrification and denitrification in a paddy soil. Mn oxide retarded nitrification in oxic conditions and enhanced it in anoxic conditions. Mn oxide decreased rate of emission of nitrous oxide in anoxic conditions. Manganese oxide might be able to regulate N cycling in rice paddy soil.

Dynamics of Soil Moisture and Salt Content After Infiltration of Saline Ice Meltwater in Saline-Sodic Soil Columns

Saline ice meltwater can be used for irrigation and leaching of salts in salt-affected soil regions. A laboratory experiment was conducted using soil columns to investigate the redistribution of soil moisture, salt and sodium adsorption ratio (SAR) in saline-sodic soil under the infiltration of saline ice meltwater. Soils were treated using saline water of three irrigation volumes (1 600, 2 400 and 3 200 mL) at four salinity levels. These four salinity levels included salt free (0 g L−1), low salinity level (1.4 g L−1), moderate salinity level (2.7 g L−1) and high salinity level (4.1 g L−1). The prepared saline water was frozen into ice, and then the ice was put on the surface of soil columns. After 96 h, the infiltration rate and soil moisture content of saline ice treatments were greater than those of salt-free ice treatments, increasing with the increase of ice salinity. Infiltration of saline ice meltwater increased soil moisture content in the upper layers for all treatments. Both salt contents and SAR values in the upper soil layers decreased in all saline ice treatments and were lower than those in salt-free ice treatment. However, this trend was reversed in the deeper (below 20cm) soil layers. The highest desalting rate and lowest SAR were observed in high-salinity treatment under three irrigation volumes in the 0–15 cm soil layer, especially under irrigation volume of 2 400 mL. These results indicate that saline ice (0–20cm) meltwater irrigation is beneficial to saline-sodic soil reclamation, and the best improvement effect would be achieved when using high-salinity ice under optimal irrigation volume.

Wetting and greening Tibetan Plateau in early summer in recent decades

AbstractThe Tibetan Plateau (TP) plays an essential role in the global hydrological cycle. Unlike the well‐recognized surface warming, changes in precipitation over the TP and the underlying mechanisms remain ambiguous. A significant increase in the amount of precipitation over the southeastern TP in May over 1979–2014 (13.46% decade−1 of the climatology) is identified in this study, based on homogenized daily rain gauge data. Both the increased precipitation frequency and intensity have contributions. The coherent increases in soil moisture content and vegetation activities further confirm the precipitation trend, indicating a wetting and greening TP in the early summer in recent decades. The moisture budget analysis shows that this wetting trend in the past four decades is dominated by the increased water vapor convergence due to circulation changes, while increases in specific humidity play a minor role. The wetting trend over the TP in May results directly from the earlier onset of the South Asian summer monsoon (ASM) since the late 1970s associated with the phase transition of Interdecadal Pacific Oscillation around the late 1990s. The earlier onset of the ASM triggers low‐level southwesterly anomalies over the northern Indian Ocean, promoting moisture convergence and increased precipitation over the TP in May. Specifically, the increased amount of precipitation after the onset of the ASM explains 95% of the increase in the total amount of precipitation in May.

Soil disturbance caused by ground-based skidding at different soil moisture conditions in Northern Iran

ABSTRACTSkidding operations induce considerable and wide spread soil disturbance. It is unclear how much additional damage is caused by increased soil moisture content at the time of skidding. We visually assessed 16 categories of soil surface disturbances, measured surface layer bulk density, porosity, and rutting in two oriental beech sites in northern Iran following five frequencies of traffic on two slope gradients with 19% and 33% soil moisture content. At both moisture contents, the most severe soil disturbances occurred with more frequent equipment traffic and on steeper slopes. Soil disturbances were detected on 65% of the harvested area at lower and 87% at higher moisture content. Bulk density, porosity, and rut depth were significantly affected by traffic frequency, trail slope and moisture content. Bulk density nearly reached critical values of 1.4-1.55 g cm–3 after 7 passes at higher and 12 passes at lower moisture content. Adverse effects on porosity caused by increased traffic and trail slope increased with increasing soil moisture content. Rutting was observed after one and seven passes at high and low moisture content, respectively, and was deeper on steeper slopes. To minimize disturbance, ground-based skidding should be limited to times when soil moisture content is low.

Monitoring and Mitigation Works in Unsaturated Archaeological Deposits

Monitoring of the archaeological deposits at the World Heritage Site Bryggen in Bergen has been ongoing since 2001. In latter years a large-scale project of mitigation works has been carried out, resulting in the creation of a water-management system aimed at raising groundwater-levels and increasing soil moisture content in areas with poor preservation conditions. Oxygen is a key parameter in the decay of archaeological material in the unsaturated zone, and the monitoring at Bryggen includes in situ monitoring of oxygen concentrations and comparison to soil moisture content, temperature, groundwater-level, precipitation and soil reactivity. This is used to document where and when decay takes place and to estimate “how wet is wet enough” in order to reduce the oxygen diffusion and the decay rate to an acceptable level. The results show that even small changes in the soil moisture can have a large impact on the oxygen dynamics in the ground.

Effects of Different Irrigation Water Types, N Fertilizer Types, and Soil Moisture Contents on N2O Emissions and N Fertilizer Transformations in Soils

The use of reclaimed water (RW) for irrigation alleviates agricultural water shortages. However, N2O emissions and N fertilizer transformations in soils irrigated with RW under different N fertilizer types and soil moisture contents are poorly understood. A 216-h laboratory incubation experiment was conducted to evaluate the effects of irrigation water types (RW and fresh water, FW), N fertilizer types (15N-labeled KNO3 and (NH4)2SO4), and soil moisture contents at 40, 60, and 90 % water-filled pore space (WFPS) on N2O emissions and N fertilizer transformations in intact soil cores. The results showed that cumulative N2O emissions ranged from 3.78 to 36.30 mg N m−2, and fertilizer-derived N2O losses accounted for 0.14–2.44 % of N fertilizers, while fertilizer-derived N residues (NO3 −-N + NH4 +-N) accounted for 10.16–26.95 % of N fertilizers. The N2O emissions at 40 % WFPS and fertilizer-derived N residues at 60 % WFPS in soils irrigated with RW were significantly (10.98 and 20.95 %, respectively) higher than those irrigated with FW, while fertilizer-derived N2O losses at 60 % WFPS in soils irrigated with RW were 10.26 % higher than those irrigated with FW. The N2O emissions and fertilizer-derived N2O losses in soils amended with (NH4)2SO4 at 40 and 60 % WFPS were significantly (26.61–178.84 %) larger than those amended with KNO3, while fertilizer-derived N residues in soils amended with KNO3 were significantly (41.47 %) higher than those amended with (NH4)2SO4. The N2O emissions significantly increased with increasing soil moisture content. Our results indicate that N fertilizer types and soil moisture contents are the two important factors regulating N2O emissions and N fertilizer transformations. When RW irrigation is used, controlling soil moisture contents within 41 and 60 % WFPS (the optimum is 46 % WFPS) and application of KNO3 can reduce N2O emissions and fertilizer-derived N2O losses, and correspondingly increase fertilizer-derived N residues, which can contribute to climate change mitigation.