Decreased Soil Temperature Research Articles

Decrease in artificial radiation with netting reduces stress and improves rabbit-eye blueberry ( Vaccinium virgatum Aiton) ‘Ochlockonee’ productivity

Blueberry production under netting has increased in recent years to mitigate the adverse effects of climate change. The objective of the present study was to evaluate the effect of different radiation intensities on rabbit-eye blueberry (Vaccinium virgatum Aiton) ‘Ochlockonee’ photosynthetic efficiency and productive parameters. Four treatments were established: T1 (control), T2, T3, and T4 at 0%, 30%, 60%, and 90% radiation decrease (RD), respectively, with black shedding netting. The following were recorded for each treatment: environmental conditions, photosystem II (PSII) maximum quantum yield (Fv/Fm), photosystem II effective quantum yield , leaf stomatal conductance (gs), quality parameters, and fruit yield. Results showed an increase of 4.6 oC in mean minimum temperatures for the different netting treatments, which promote development and fruit set, as well as prevent damage at temperatures near 0 oC. The RD treatments increased between 175% and 325% (P < 0.05) compared to the control. It can be concluded that netting decreased soil temperature between 1 and 3 oC and increased minimum temperatures between 1 and 6 oC, which promoted plant development and decreased frost damage during flowering and fruit development. Current direct radiation levels over 1000 µmol m-2 s-1 in V. virgatum inhibited productivity in T1. Netting decreased the degree of photoinhibition and increased photosystem II photochemical efficiency throughout the day, and T4 and T3 exhibited the highest efficiency.

Tendencies in current climate change and atmospheric circulation variability in the Arctic region of West Siberia

The main goal of this study is to carry out the investigation of the climatic parameters variability and the role of global atmospheric circulation in their trends over the Arctic region of West Siberia (60-70°N, 60-90°E) using reanalysis data. The characteristics of spatial and temporal variability of meteorological parameters (surface air temperature and soil temperature, atmospheric pressure, snow depth and surface albedo) were calculated using ERA-Interim reanalysis data over the period of 1979−2015. It was established that in the beginning of XXI century, there is an air and soil temperature decrease in winter and autumn and its statistically significant increase in spring and summer. The tendency to permafrost area degradation is observed for the Arctic region. The maximal changes are observed in low-temperature permafrost soils than in soils with higher temperature. This trend is accompanied by the decrease in snow cover depth and surface albedo. Global circulation indices variability, its relationships with meteorological parameters in West Siberia and with sea ice cover extent in the Arctic Seas indicate that atmospheric blocking processes, which are responsible for anticyclonic type of weather, were developed in the region during last decades.

Effects of straw and plastic film mulching on greenhouse gas emissions in Loess Plateau, China: A field study of 2 consecutive wheat-maize rotation cycles.

Mulching practices have long been used to modify the soil temperature and moisture conditions and thus potentially improve crop production in dryland agriculture, but few studies have focused on mulching effects on soil gaseous emissions. We monitored annual greenhouse gas (GHG) emissions under the regime of straw and plastic film mulching using a closed chamber method on a typical winter-wheat (Triticum aestivum L. cv Xiaoyan 22) and summer-maize (Zea mays L. cv Qinlong 11) rotation field over two-year period in the Loess Plateau, northwestern China. The following four field treatments were included: T1 (control, no mulching), T2 (4000kgha-1 wheat straw mulching, covering 100% of soil surface), T3 (half plastic film mulching, covering 50% of soil surface), and T4 (complete plastic film mulching, covering 100% of soil surface). Compared with the control, straw mulching decreased soil temperature and increased soil moisture, whereas plastic film mulching increased both soil temperature and moisture. Accordingly, straw mulching increased annual crop yields over both cycles, while plastic film mulching significantly enhanced annual crop yield over cycle 2. Compared to the no-mulching treatment, all mulching treatments increased soil CO2 emission over both cycles, and straw mulching increased soil CH4 absorption over both cycles, but patterns of soil N2O emissions under straw or film mulching are not consistent. Overall, compared to T1, annual GHG intensity was significantly decreased by 106%, 24% and 26% under T2, T3 and T4 over cycle 1, respectively; and by 20%, 51% and 29% under T2, T3 and T4 over cycle 2, respectively. Considering the additional cost and environmental issues associated with plastic film mulching, the application of straw mulching might achieve a balance between food security and GHG emissions in the Chinese Loess Plateau. However, further research is required to investigate the perennial influence of different mulching applications.

Analysis of a ground source heat pump system using an unsaturated 3-dimensional model

This research presents an unsaturated three-dimensional model to study a ground source heat pump system based on moisture porous theory and soil moisture dynamics. The experiments are performed under the same condition as in the numerical methods. The soil temperature along 50m deep of the U tube shows good agreement with the simulation results. The shallow soil temperature decreases by approximately 0.5–0.9°C, during the heating period, when the infiltration and evaporation are considered by adding a source phase equation on the same operation time. The infiltration-influencing factors (e.g. soil moisture rate and soil saturated hydraulic conductivity) and the evaporation-influencing factors (e.g. soil saturated moisture content) are also calculated. The soil temperature decreases by approximately 5–8% as the influencing factors increase by 50–100%. Furthermore, the effect on the shallow soil is obvious, especially at a depth of 5m and attenuates with the soil depth.

Effect of moderate high temperature on the vegetative growth and potassium allocation in olive plants

There is little information about the prolonged effect of a moderately high temperature on the growth of olive (Olea europaea L.). It has been suggested that when the temperature of the air rises above 35°C the shoot growth of olive is inhibited while there is any reference on how growth is affected when the soil is warmed. In order to examine these effects, mist-cuttings and young plants generated from seeds were grown under moderate high temperature (37°C) for 64 and 42days respectively. In our study, plant dry matter accumulation was reduced when the temperature of both the air and the root medium was moderately high. However, when the temperature of the root medium was 25°C, the inhibitory effect of air high temperature on plant growth was not observed. The exposure of both the aerial part and the root to moderate high temperature also reduced the accumulation of K+ in the stem and the root, the water use efficiency and leaf relative water content. However, when only the aerial part was exposed to moderate high temperature, the accumulation of K+ in the stem, the water use efficiency and leaf relative water content were not modified. The results from this study suggest that the olive is very efficient in regulating the water and potassium transport through the plant when only the atmosphere surrounding the aerial part is warmed up. However, an increase in the soil temperature decrease root K+ uptake and its transport to the aerial parts resulting in a reduction in shoot water status and growth.

Complex impacts of logging residues on planted hybrid poplar seedlings in boreal ecosystems

We studied three hybrid poplar plantations in Quebec (Canada) established on sites with varying soil and environmental characteristics to investigate the effects of logging residues on the water potential, carbon isotope ratio and foliar nutrients of planted trees. On each site, four treatments representing different residue loads, as well as treatments aimed at manipulating specific factors of the environment (Herbicide, Geotextile) were applied to test their effects on seedling water potential, carbon isotope ratio and foliar nutrients. Along with analyses of variance, we used structural equation modelling to infer causal relationships of logging residues on height, basal diameter and foliar nutrition of trees through their effects on soil temperature, soil water content and competing vegetation cover. Logging residues decreased soil temperature at all sites and woody plants cover at one site out of three. Height, basal diameter and unit leaf mass were strongly related to each other. Foliar δ13C, N concentration and unit leaf mass increased with decreasing cover of woody plants suggesting an important role of competition for resources. Overall, logging residues had no direct influence on hybrid poplar dimensions after two growing seasons: their effects on the microenvironment of this resource demanding tree species were either cancelling out each other, or were not significant enough to have a significant impact on the growth drivers measured. For example, presence of logging residues might reduce soil temperature, impeding overall seedling performance. Our study highlights the fact that any given silvicultural method aimed at manipulating logging residues has a complex influence involving the interaction of multiple environmental drivers and that the net effect on tree productivity will depend on species and site specific conditions.

Mulching Affects Soil Properties and Greenhouse Gas Emissions Under Long‐Term No‐Till and Plough‐Till Systems in Alfisol of Central Ohio

AbstractAgricultural activities emit greenhouse gases (GHGs) and contribute to global warming. Intensive plough tillage (PT), use of agricultural chemicals and the burning of crop residues are major farm activities emitting GHGs. Intensive PT also degrades soil properties by reducing soil organic carbon (SOC) pool. In this scenario, adoption of no‐till (NT) systems offers a pragmatic option to improve soil properties and reduce GHG emission. We evaluated the impacts of tillage systems (NT and PT) and wheat residue mulch on soil properties and GHG emission. This experiment was started in 1989 on a Crosby silt loam soil at Waterman Farm, The Ohio State University, Columbus, Ohio, USA. Mulching reduced soil bulk density and improved total soil porosity. More total carbon (16.16 g kg−1), SOC (8.36 mg L−1) and soil microbial biomass carbon (152 µg g−1) were recorded in soil under NT than PT. Mulch application also decreased soil temperature (0–5 cm) and penetration resistance (0–60 cm). Adoption of long‐term NT reduced the GHG emission. Average fluxes of GHGs under NT were 1.84 g CO2‐C m−2 day−1 for carbon dioxide, 0.07 mg CH4‐C m−2 day−1 for methane and 0.73 mg N2O‐N m−2 day−1 for nitrous oxide compared with 2.05 g CO2‐C m−2 day−1, 0.74 mg CH4‐C m−2 day−1 and 1.41 mg N2O‐N m−2 day−1, respectively, for PT. Emission of nitrous oxide was substantially increased by mulch application. In conclusion, long‐term NT reduced the GHG emission by improving the soil properties. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Integrated double mulching practices optimizes soil temperature and improves soil water utilization in arid environments.

Water shortage threatens agricultural sustainability in many arid and semiarid areas of the world. It is unknown whether improved water conservation practices can be developed to alleviate this issue while increasing crop productivity. In this study, we developed a "double mulching" system, i.e., plastic film coupled with straw mulch, integrated together with intensified strip intercropping. We determined (i) the responses of soil evaporation and moisture conservation to the integrated double mulching system and (ii) the change of soil temperature during key plant growth stages under the integrated systems. Experiments were carried out in northwest China in 2009 to 2011. Results show that wheat-maize strip intercropping in combination with plastic film and straw covering on the soil surface increased soil moisture (mm) by an average of 3.8% before sowing, 5.3% during the wheat and maize co-growth period, 4.4% after wheat harvest, and 4.9% after maize harvest, compared to conventional practice (control). The double mulching decreased total evapotranspiration of the two intercrops by an average of 4.6% (P<0.05), compared to control. An added feature was that the double mulching system decreased soil temperature in the top 10-cm depth by 1.26 to 1.31°C in the strips of the cool-season wheat, and by 1.31 to 1.51°C in the strips of the warm-season maize through the 2years. Soil temperature of maize strips higher as 1.25 to 1.94°C than that of wheat strips in the top 10-cm soil depth under intercropping with the double mulching system; especially higher as 1.58 to 2.11°C under intercropping with the conventional tillage; this allows the two intercrops to grow in a well "collaborative" status under the double mulching system during their co-growth period. The improvement of soil moisture and the optimization of soil temperature for the two intercrops allow us to conclude that wheat-maize intensification with the double mulching system can be used as an effective farming model in alleviating water shortage issues experiencing in water shortage areas.

Grazing exclusion reduced soil respiration but increased its temperature sensitivity in a Meadow Grassland on the Tibetan Plateau.

Understanding anthropogenic influences on soil respiration (R s) is critical for accurate predictions of soil carbon fluxes, but it is not known how R s responds to grazing exclusion (GE). Here, we conducted a manipulative experiment in a meadow grassland on the Tibetan Plateau to investigate the effects of GE on R s. The exclusion of livestock significantly increased soil moisture and above-ground biomass, but it decreased soil temperature, microbial biomass carbon (MBC), and R s. Regression analysis indicated that the effects of GE on R s were mainly due to changes in soil temperature, soil moisture, and MBC. Compared with the grazed blocks, GE significantly decreased soil carbon release by 23.6% over the growing season and 21.4% annually, but it increased the temperature sensitivity (Q10) of R s by 6.5% and 14.2% for the growing season and annually respectively. Therefore, GE may reduce the release of soil carbon from the Tibetan Plateau, but under future climate warming scenarios, the increases in Q10 induced by GE could lead to increased carbon emissions.

Numerical Simulation of Coupled Water and Salt Transfer in Soil and a Case Study of the Expansion of Subgrade composed by Saline Soil

Salt expansion is one of the major problems of subgrade involving saline soils. Salt expansion is induced by the crystallization of salt when the soil water content or temperature decreases. A case of salt expansion in subgrade composed by saline soil is introduced. It is located in G314 Road, which is one of the national highways in China, from Urumqi to Khunjerab. There is 3.40 ∼5.91% salt within 1.0 depth in the ground surface of the G314 (K587 + 035), which belongs to strong sulphate salty soil. The maximum salt expansion is up to 20cm in G314 Road, which has a serious impact on the road. Salt expansion is majorly controlled by the salt crystallization and the transmission of water and salt. Based on the solute transport theory in porous media, the water flow theory and thermal conduction theory, the govern differential equations of coupled salt crystallization, salt transmission and water flow are established in this paper. The coupled water and salt transfer problem of saline soil is solved by a software named as COMSOL with the use of a secondary development module. To verify the method for simulating the coupled water and salt transmission process, the water and salt transfer process in a 1D soil column is simulated and the results are compared with the theoretical solution. The results show that coupled model of water and salt established in this paper can accurately predict salt migration and crystallization of saline soil.

The Effect of Mulch and Fertilizer on Soil Temperature of a Potato Growth

The aim of this research is to investigate the effect of the temperature decrease by using mulch and fertilizer on the soil to potato. The study was conducted in November 2008 until June 2009 which was designed in a separate split plot design. The treatments consists of two factors and three replications, namely Factor I: The main plot consist of four treatments of mulch without mulch (Mo), Cover crops Arachis pintoi (Ma), rice straw mulch (Mj) and Black silver plastic mulch (Mp). Factor II: The sub-plot consists of three treatments: without fertilizer (P0), NPK 300 kg /ha (P1) and a combination of organic fertilizer 20 tons / ha nonorganic fertilizer (NPK), of 300 kg/ha (P2). The parameter was the surface erosion rate, the growth and production of potatoes, that were observed, that is environment components: 1) the measurement of soil temperature at night.and the plant component (the number of tubers). The study showed that all types of mulch effectively decrease soil temperature. The rice straw mulch ttreatment with a combination of organic and anorganic fertilizer produced the lowest soil temperature of 17.82 0C. It is capable of recording the soil temperature up to 6.43 0C. The treatment of types of mulch in combination with organic and anorganic fertilizer produced the highest number of tuber compared to other types of treatments. However, treatment types of mulch are given a combination of organic and anorganic fertilizer resulted in the highest number of tubers. Future work should focus on the use of mulch and fertilizer in getting the optimum growth of potato.

西北旱地春小麦不同覆盖措施的温度和产量效应

PDF HTML阅读 XML下载 导出引用 引用提醒 西北旱地春小麦不同覆盖措施的温度和产量效应 DOI: 10.5846/stxb201403050373 作者: 作者单位: 甘肃农业大学生命科学与技术学院 甘肃干旱生境国家重点实验室 作者简介: 通讯作者: 中图分类号: 基金项目: 公益性行业(农业)科研专项(20130314);现代农业产业技术体系建设专项(CARS-3-2-49) Effect of mulching method on soil temperature and grain yield of spring wheat in rainfed agricultural areas of northwestern China Author: Affiliation: College of bioscience and technology, Gansu Provincial Key Lab of Aridland Crop Science Gansu Agricultural University, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:在西北半干旱雨养条件下,以春小麦为材料,研究了夏季覆膜(T1)、秋季覆膜(T2)、春季覆膜(T3)、小麦碎秆覆盖(T4)、小麦整秆覆盖(T5)、夏季覆膜+麦秆还田 (T6)和无覆盖对照(CK)7个处理间0-20 cm土壤温度、产量和重要农艺指标的差异。结果表明:处理间在不同生育时期、不同土层的土壤温度存在显著差异。生育时期间比较,处理间土壤温度差异以播种期-分蘖期最大、蜡熟期-成熟期次之、拔节期-灌浆中期较小;土层间比较,处理间土壤5 cm处的温度差异依次大于10 cm、15 cm、20 cm处。T6在各时期、各土层均表现出突出的增温效应,全生育期土壤平均温度较CK高0.57 ℃,以成熟期、播种期及分蘖期增温效果较大;其它覆盖处理存在增温和降温的双重效应,增温效应覆膜 > 秸秆覆盖,而降温效应则秸秆覆盖 > 覆膜,各处理的32个土壤温度测试点中,增温点次以T4最少(仅有9个),降温点次为23个,且T4降温幅度最大,全生育期0-20 cm土壤平均温度较CK低0.63 ℃,降温效果在播种期和分蘖期尤为突出。覆盖处理全生育期土壤平均温度表现为覆膜 > CK > 秸秆覆盖。温差最高值出现在分蘖期土壤5 cm处的T6与T4间,T6高出T4 4.23 ℃。T6可以平抑生育期间土壤温度的变化,其它5个覆盖处理则加剧土壤温度的波动,以T4处理的土壤温度波动最明显(CV为32.4%)。处理间产量、单位面积穗数、穗粒数间差异显著,而千粒重差异不显著。无论覆膜还是秸秆覆盖,都较CK穗粒数显著增加(17.4%-36.3%)。除T5较CK显著减产14.1%外,其它覆盖处理均较CK显著增产21.7%-37.3%,其中以全膜覆土穴播基础上的秋季覆膜 (T2)增产最显著,适宜在西北旱地春小麦产区推广应用。土壤温度主要影响营养生长,拔节-开花期0-20 cm的土壤温度与株高高度正相关(0.77*-0.92**),但覆盖引起土壤温度的变化最终对西北旱地春小麦产量没有关键影响。 Abstract:This study determined the effects of mulching method on soil temperatures in the 0-20 cm soil layer, and grain yield of spring wheat (Triticum aestivum L.) in a semiarid rainfed agricultural area of northwestern China. The experiment was conducted at Tongwei Research Station, Gansu Agricultural University (34°55'N, 104°57'E) in 2012. The following 7 treatments were evaluated: plastic film mulch applied in summer (T1), plastic film mulch applied in autumn (T2), plastic film mulch applied in spring (T3), mulching with chopped wheat straw (5 cm in length) on the soil surface in summer (T4), mulching with whole wheat straw in summer (T5), T1 in combination with harvested wheat straw returned to the field (T6), and control (no mulching, CK). Soil temperatures were measured and recorded at 32 points in each treatment. Soil temperatures differed significantly among mulching treatments, growth stages and soil layers. The largest difference in soil temperature occurred from the sowing to tillering period, followed by the dough stage to maturation period, whereas the smallest differences in soil temperature were in the jointing-middle filling stage. Soil temperature decreased with soil depth in the order 5 cm > 10 cm > 15 cm > 20 cm. Soil temperature in the T6 plots was significantly (0.57 ℃) higher than, and this effect was more pronounced in the sowing, tillering, and maturing stages than in the other growth stages. The other five treatments either increased or decreased soil temperatures depending on growth stage and soil layer. Soil temperature was consistently increased by plastic film mulch but consistently decreased by straw mulching. The T4 treatment had 9 points with soil temperatures higher than the CK, and 23 points lower than the CK. Mean soil temperature over the whole growth period was 0.63℃ lower in the T4 treatment than in the CK, with the difference being more obvious at the time of sowing and the tillering stage. Average soil temperatures over the whole growth period were in the order: plastic film mulch > CK > straw mulching. The highest difference occurred between T6 and T4 in the 5 cm soil layer at the tillering stage, with T6 being 4.23 ℃ higher than T4. The largest variation soil temperature among growth stages was found in the T4 treatment, with a coefficient of variation of 32.4%. Mulching increased the number of kernels per spike by 17.4% to 36.3% compared with the CK. Mulching increased wheat grain yield by 21.7% to 37.3% compared to the CK, with the maximum yield increase being with plastic film mulch applied in the autumn (T2). The exception was the T5 treatment which decreased grain yield by 14.1% compared to the CK. It appears that the T2 mulching method is the most suitable for spring wheat production in rainfed agricultural regions of northwestern China. There were highly positive correlations (r = 0.77*-0.92**) between soil temperature and plant height at jointing-flowering, but mulching method did not have a significant impact on spring wheat grain yield in the study area. 参考文献 相似文献 引证文献

Review of Alternative Management Options of Vegetable Crop Residues to Reduce Nitrate Leaching in Intensive Vegetable Rotations

Vegetable crop residues take a particular position relative to arable crops due to often large amounts of biomass with a N content up to 200 kg N ha−1 left behind on the field. An important amount of vegetable crops are harvested during late autumn and despite decreasing soil temperatures during autumn, high rates of N mineralization and nitrification still occur. Vegetable crop residues may lead to considerable N losses through leaching during winter and pose a threat to meeting water quality objectives. However, at the same time vegetable crop residues are a vital link in closing the nutrient and organic matter cycle of soils. Appropriate and sustainable management is needed to harness the full potential of vegetable crop residues. Two fundamentally different crop residue management strategies to reduce N losses during winter in intensive vegetable rotations are reviewed, namely (i) on-field management options and modifications to crop rotations and (ii) removal of crop residues, followed by a useful and profitable application.

Mulch Effects on Floral Resources and Fruit Production of Squash, and on Pollination and Nesting by Squash Bees

Zucchini squash (Cucurbita pepo) has a high pollination demand, and the native, ground-nesting squash bee (Peponapis pruinosa) provides the majority of the crop’s pollination requirement in some environments. Squash bees nest directly in crop fields, and nests can be disturbed by tillage and other management operations. Mulches that use municipal waste materials may provide a weed control strategy for squash plantings that is more benign to squash bees than cultivation. Field and greenhouse studies were conducted in 2011 and 2012 to compare the effects of nontillage weed control methods including polyethylene black plastic, woodchips, shredded newspaper, a combination of shredded newspaper plus grass clippings (NP + grass), and bare soil (control) on soil characteristics, squash pollination and fruit production, and squash bee nesting. Woodchips, shredded newspaper, and NP + grass mulch decreased soil temperature, while soils beneath newspaper mulch retained more moisture. Unmarketable, misshapen fruit occurred more frequently in plastic than in the other mulch treatments. No measurable differences in floral resource production or crop pollination were found among treatments, suggesting that misshapen fruit resulted from high soil temperatures in black plastic plots rather than poor pollinator attraction. Squash bee nests were located within bare soil, newspaper, and NP + grass plots, indicating that these mulches did not prevent nesting. NP + grass mulch had a positive effect on plant growth and fruit production, possibly from an addition of plant-available nitrogen or the presence of preferable nesting ground. Shredded newspaper when combined with grass clippings performed as an effective mulch material that improved crop performance with no apparent negative impacts on squash bee nesting or on squash floral resources and pollination.

Short-term effects of four tillage practices on soil physical properties, soil water potential, and maize yield

The area cultivated using conservation tillage has recently increased in central Spain. However, soil compaction and water retention with conservation tillage still remains a genuine concern for landowners in this region because of its potential effect on the crop growth and yield. The aim of this research is to determine the short-term influences of four tillage treatments on soil physical properties. In the experiment, bulk density, cone index, soil water potential, soil temperature and maize (Zea mays L.) productivity have been measured. A field experiment was established in spring of 2013 on a loamy soil. The experiment compared four tillage methods (zero tillage, ZT; reservoir tillage, RT; minimum tillage, MT; and conventional tillage, CT). Soil bulk density and soil cone index were measured during maize growing season and at harvesting time. Furthermore, the soil water potential was monitored by using a wireless sensors network with sensors at 20 and 40cm depths. Also, soil temperatures were registered at depths of 5 and 12cm. Results indicated that there were significant differences between soil bulk density and cone index of ZT method and those of RT, MT, and CT, during the growing season; although, this difference was not significant at the time of harvesting in some soil layers. Overall, in most soil layers, tillage practice affected bulk density and cone index in the order: ZT>RT>MT>CT. Regardless of the entire observation period, results exhibited that soils under ZT and RT treatments usually resulted in higher water potential and lower soil temperature than the other two treatments at both soil depths. In addition, clear differences in maize grain yield were observed between ZT and CT treatments, with a grain yield (up to 15.4%) increase with the CT treatment. On the other hand, no significant differences among (RT, MT, and CT) on maize yield were found. In conclusion, the impact of soil compaction increase and soil temperature decrease, produced by ZT treatment is a potential reason for maize yield reduction in this tillage method. We found that RT could be certainly a viable option for farmers in central Spain, particularly when switching to conservation tillage from conventional tillage. This technique showed a moderate and positive effect on soil physical properties and increased maize yields compared to ZT and MT, and provides an opportunity to stabilize maize yields compared to CT.

Evaporative Cooling of Wet Soil Surface under Different Agricultural Land Use Systems

Laboratory evaporation studies were conducted to assess the roles of the various stages of evaporation on heat reduction from wet soil surfaces. Undisturbed soil columns from three different fields viz., cocoa (Theobroma cacao), oil palm (Elaies guineensis) and arable were collected from the 0-10 cm depth at the Plantations section of the Department of Crop and Soil Sciences, KNUST, Kumasi. The samples were initially saturated with water at an initial temperature of 65 o C. The soil columns were subjected to surface evaporation by placing them under a Sanyo (40 cm) dynamic wide desk oscillating fan. Evaporation and temperature readings were taken at 5 minutes interval for 1 hour. Two homogeneous soil columns were used as for reference tests (control). Evaporation analysis showed 1st and 2nd stages of evaporation with cumulative evaporation being proportional to the square root of time at the 2nd stage. Temperature decreased rapidly with increasing evaporation during the 1st stage of evaporation till the falling and slow rate stages, during which change in temperature was minimal and almost constant. A 1 mm increase in evaporation showed a decrease in mean temperature by 7.53 o C, 7.35 o C and 7.10 o C from cocoa, oil palm and arable fields, respectively at 1% significant level. The results of this study indicated that under a constant atmospheric evaporativity, 1 mm increase in evaporation would cause a significant decrease in soil temperature.

Modeling the Emergence of Winter Wheat in Response to Soil Temperature, Water Potential, and Planting Depth

Abstract. Seedling emergence is a critical stage in wheat (Triticum aestivum L.) establishment, particularly in dryland agriculture. Soil temperature, water potential, and planting depth are important factors influencing emergence. These factors can have considerable spatio-temporal variation, making it difficult to predict the timing and percentage of wheat seedling emergence. Our objectives were to: (1) measure the effect of soil temperature, water potential, and planting depth on seedling emergence of winter wheat; and (2) develop a population-based hydrothermal model to estimate time and percentage of winter wheat emergence planted at a given soil depth. The experiment was a 3 (wheat cultivars) A— 3 (planting depths) A— 5 (temperatures) A— 5 (water potentials) factorial in a randomized complete block design (RCBD) with three replicates. Decreasing soil water potential from 0 to -1 MPa delayed emergence of Moro, Buchanan, and Rod by 13, 14, and 18 days after planting and prolonged the time to reach maximum emergence by 19, 21, and 27 days after planting, respectively. Decreasing soil temperature from 25°C to 5°C delayed the average starting emergence of the three wheat cultivars by 19 days and delayed their average maximum emergence by 25 days after planting. Increasing soil planting depth from 5 to 10 cm delayed starting emergence time for Moro, Buchanan, and Rod by 6, 4, and 7 days, while maximum emergence was delayed by 12, 16, and 9 days after planting, respectively. Increasing the planting depth from 5 to 15 cm hindered the three cultivars from reaching 50% emergence. A hydrothermal time emergence model was developed that estimated observed emergence with 154 out of 207 data points having a root mean square error (RMSE) of ≤15%, whereas 19% of the simulated results did not exceed 19% RMSE and only 7% of the simulated data had RMSE greater than 20%. The simulations of the emergence model for maximum percent seedling emergence (E max ) and number of days after planting to reach maximum emergence (DAP max ) were compared with field data for three years and two cultivars (Rod and Moro). The emergence model gave reasonably good simulations of E max and DAP max for both winter wheat cultivars and in the three years of sowing dates.

Crop residue management and soil health: A systems analysis

Due to the scarcity of alternative organic amendments, the retention of crop residue in fields can be considered key in promoting physical, chemical, and biological attributes of soil health in agricultural systems of developing countries. However, due to multiple other uses, small landholders in these countries are faced with trade-offs in managing crop residues. This article reviews crop residue management practices, mainly surface retention, incorporation or removal, describing their advantages and limitations in cereal-based agroecosystems in developing countries. The benefits of residue retention are regionally variable and depend on both agroclimatic and socioeconomic factors. Most studies from developing countries in Asia, Latin America, and Africa show positive effects of retaining crop residues on soil quality, soil organic matter and carbon storage, soil moisture retention, enhanced nutrient cycling, and decreased soil loss, among other environmental and soil health benefits. Variation was observed in the effect of surface retention vs. incorporation on various soil properties indicating the importance of taking into account abiotic factors such as climate, soil texture, study duration, sampling methods, and agronomic practices when assessing the impact of these practices. Negative effects of residue retention on crop performance attributed to nitrogen immobilization, waterlogging and decreased soil temperature have also been reported in some environments. Residue trade-offs in mixed crop-livestock systems in developing countries can limit the amount of residue retained. However, interventions such as intensification, partial retention, improved return of nutrients from manures, and the provision of substitutes to the current functions of livestock (e.g. mechanization, insurance) could reduce these residue trade-offs in favour of promoting long-term soil health.

In situ soil respiration at reclaimed and unreclaimed post-mining sites: Responses to temperature and reclamation treatment

Soil respiration accounts for much of the CO2 released from terrestrial ecosystems into the atmosphere. Although respiration depends on temperature, the relationship between respiration and temperature may vary among soils. Here, we measured soil respiration and soil temperature in chronosequences of reclaimed and unreclaimed post-mining sites (10–50-year-old coal mining heaps near Sokolov, the Czech Republic) to determine the major factors affecting temperature-dependent soil respiration. Soil respiration was repeatedly measured in situ during 2011 and 2012 at five reclaimed sites (planted with alder) and five unreclaimed sites (overgrown with willow, birch, and aspen). In addition, spatial heterogeneity was assessed by repeatedly measuring soil respiration at 30 permanent points at one 28-year-old site (the “30-point” site) in 2007–2008. In all sites root biomass, soil carbon (C) content, soil pH, and the thickness of Oe layer were also measured.In the chronosequences and 30-point site, the relationship between soil respiration and temperature increased with soil C content; soil respiration was unrelated to temperature if soil C content was <9%. The increase in respiration with temperature was enhanced by a thick Oe layer and by high root biomass.Soil respiration at reclaimed sites increased with site age to age 30 years and then decreased. The decrease in respiration at the older sites was associated with a decrease in soil temperature (associated with increased shading). Respiration at unreclaimed sites increased with age and was usually lower than in reclaimed alder plantation of similar ages.

Simulation of a combined heating, cooling and domestic hot water system based on ground source absorption heat pump

The amount of energy used for heating and domestic hot water (DHW) is very high and will keep increasing. The conventional ground source electrical heat pump used in heating-dominated buildings has the problems of thermal imbalance, decrease of soil temperature, and deterioration of heating performance. Ground source absorption heat pump (GSAHP) is advantageous in both imbalance reduction and primary energy efficiency (PEE) improvement; however, the imbalance is still unacceptable in the warmer parts of cold regions. A combined heating/cooling/DHW (HCD) system based on GSAHP is proposed to overcome this problem. The GSAHPs using generator absorber heat exchange (GAX) and single-effect (SE) cycles are simulated to obtain the performance under various working conditions. Different HCD systems in Beijing and Shenyang are simulated comparatively in TRNSYS, based on which the thermal imbalance, soil temperature, heat recovery, and energy efficiency are analyzed. Results show that GSAHP–GAX–HCD is suitable for Beijing and GSAHP–SE–HCD is suitable for Shenyang. The imbalance ratio can be reduced to −14.8% in Beijing and to 6.0% in Shenyang with an annual soil temperature variation of only 0.5°C and 0.1°C. Furthermore, about 20% and 15% of the total condensation/absorption heat is recovered to produce DHW, and the PEE can reach 1.516 in Beijing and 1.163 in Shenyang. The combined HCD systems can achieve a PEE improvement of 23.6% and 44.4% compared with the normal heating/cooling systems.