Daily Soil Temperature Research Articles

Soil Warming Increases Arsenic Availability in the Rice Rhizosphere

Core Ideas Arsenic is a common contaminant in rice, threatening yield and human health. Climate warming could alter availability and plant uptake of arsenic. Arsenic concentrations in porewater and plant tissue increased with soil warming. Grain arsenic concentrations were not significantly affected by soil temperature. Future studies should explore links between climate conditions and arsenic uptake by rice. Arsenic uptake by rice (Oryza sativa L.) threatens yield and contaminates grain. Climate warming could affect these hazards. We tested the effect of elevated soil temperature on arsenic availability to and uptake by rice plants. Rice was grown in arsenic‐amended soil in rhizoboxes that facilitated porewater sampling and synchrotron X‐ray fluorescence (XRF) imaging of the rhizosphere. Plants were subjected to similar atmospheric conditions but different soil temperatures. The XRF imaging revealed greater arsenic sequestration in root iron plaques with a warmer soil temperature. Mean and median arsenic concentrations in porewater and root, straw, and husk tissue were positively correlated with average daily maximum soil temperature. Grain arsenic concentrations did not change. Warmer soil temperatures likely increased plant‐available arsenic by increasing reductive dissolution of arsenic‐bearing iron minerals, but the plants effectively regulated grain arsenic. The impacts of changing environmental conditions on arsenic contamination of rice should be further explored.

Spatio-temporal variation analysis of soil temperature based on wireless sensor network

Abstract: Soil temperature is a key factor for best planting dates decision-making in the large scale farming areas of northeast China because of high latitudes and frigid environment. Continuous data were collected from a wireless sensor network (WSN)-based monitoring system to exactly analyze and understand soil temperature of the whole farmland. Using the classical statistics and geo-statistics methods, real-time monitoring data were analyzed with three aspects, i.e. temporal variation, spatial variation and spatio-temporal variation. Temporal variation analysis of each sensor node showed a sinusoidal curve of daily soil temperature and gave the long-term trend of daily average soil temperature in a certain period. Spatial variation analysis provided the spatial distribution map of daily average soil temperature within a study region for a certain day. Spatio-temporal variation analysis quantified the variation process of the spatial distribution over time by the monitored classes distribution indicator (MCDI) proposed. Experimental results showed that the above variations analysis of the real-time data provide an effective approach to determine whole-farmland soil temperature. Keywords: precision agriculture, soil temperature dynamics, spatial-temporal variability, spatial variation, wireless sensor network (WSN) DOI: 10.3965/j.ijabe.20160906.1871 Citation: Liu H, Meng Z J, Wang H, Xu M. Spatio-temporal variation analysis of soil temperature based on wireless sensor network. Int J Agric & Biol Eng, 2016; 9(6): 131－138.

A multi-year estimate of methane fluxes in Alaska from CARVE atmospheric observations.

Methane (CH4) fluxes from Alaska and other arctic regions may be sensitive to thawing permafrost and future climate change, but estimates of both current and future fluxes from the region are uncertain. This study estimates CH4 fluxes across Alaska for 2012-2014 using aircraft observations from the Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE) and a geostatistical inverse model (GIM). We find that a simple flux model based on a daily soil temperature map and a static map of wetland extent reproduces the atmospheric CH4 observations at the state-wide, multi-year scale more effectively than global-scale, state-of-the-art process-based models. This result points to a simple and effective way of representing CH4 flux patterns across Alaska. It further suggests that contemporary process-based models can improve their representation of key processes that control fluxes at regional scales, and that more complex processes included in these models cannot be evaluated given the information content of available atmospheric CH4 observations. In addition, we find that CH4 emissions from the North Slope of Alaska account for 24% of the total statewide flux of 1.74 ± 0.44 Tg CH4 (for May-Oct.). Contemporary global-scale process models only attribute an average of 3% of the total flux to this region. This mismatch occurs for two reasons: process models likely underestimate wetland area in regions without visible surface water, and these models prematurely shut down CH4 fluxes at soil temperatures near 0°C. As a consequence, wetlands covered by vegetation and wetlands with persistently cold soils could be larger contributors to natural CH4 fluxes than in process estimates. Lastly, we find that the seasonality of CH4 fluxes varied during 2012-2014, but that total emissions did not differ significantly among years, despite substantial differences in soil temperature and precipitation; year-to-year variability in these environmental conditions did not affect obvious changes in total CH4 fluxes from the state.

Mitigation impact of minimum tillage on CO2 and N2O emissions from a Mediterranean maize cropped soil under low-water input management

Reduced tillage might reduce greenhouse gas (GHG) emissions from cropped soils. However the topic is somehow still controversial, since lower CO2 emissions achieved through reduced soil mineralization might be offset by higher N2O losses from less disturbed soil, because of higher water filled pore space. This work aimed to clarify the potential GHG mitigation benefits of minimum tillage (MT), as opposed to mouldboard ploughing (CT), for Mediterranean maize cultivations under low water input management. To this end, soil CO2 and N2O fluxes were monitored at high time resolution by means of a newly developed automated system of closed static chambers coupled to a field gas photoacoustic detector. Relative to CT, cumulated CO2 emissions appeared significantly reduced in MT over three months after the autumn ploughing (by about 30%) and along the spring-summer cultivation (by about 28%), for similar maize yields. N2O emissions from MT showed restrained averaged values relative to CT (by 40% and 18% for fallow and maize periods, respectively); however differences might not be significant. For both treatments, N2O emission factors were lower than the 1% IPCC default value (0.40 and 0.28 for CT and MT, respectively), following the restrained irrigation water input along the drought period. Results indicate that MT reduced GHG emissions both (i) in the short-term, likely due to the increased decomposition of soil organic matter in the ploughed soil (CT), mainly concentrated within the first week after deep tillage; (ii) in the longer-term, likely through its capacity to constrain the daily soil temperature fluctuations in the drought periods along the spring-summer maize cultivation. At this stage, the low-water input management might have played a key role in mediating the response of N2O emissions to MT treatment.These findings suggest that minimum tillage could entail consistent GHG benefits under the drip irrigation management in Mediterranean croplands.

Daily soil temperature modeling using ‘panel-data’ concept

ABSTRACTThe purpose of this research was to predict soil temperature profile using ‘panel-data’ models. Panel-data analysis endows regression analysis with both spatial and temporal dimensions. The spatial dimension pertains to a set of cross-sectional units of observation. The temporal dimension pertains to periodic observations of a set of variables characterizing these cross-sectional units over a particular time-span. This study was conducted in Khorasan-Razavi Province, Iran. Daily mean soil temperatures for 9 years (2001–2009), in 6 different depths (5, 10, 20, 30, 50 and 100 cm) under bare soil surface at 10 meteorological stations were used. The data were divided into two sub-sets for training (parameter training) over the period of 2001–2008, and validation over the period of the year 2009. The panel-data models were developed using the average air temperature and rainfall of the day before ( and , respectively) and the average air temperature of the past 7 days (Tw) as inputs in order to predict the average soil temperature of the next day. The results showed that the two-way fixed effects models were superior. The performance indicators (R2 = 0.94 to 0.99, RMSE = 0.46 to 1.29 and MBE = −0.83 and 0.74) revealed the effectiveness of this model. In addition, these results were compared with the results of classic linear regression models using t-test, which showed the superiority of the panel-data models.

Development and preliminary evaluation of an integrated field scale model for perennial bioenergy grass ecosystems in lowland areas

Computer models are useful tools for evaluating environmental and economic sustainability of proposed dedicated cellulosic grass ecosystems for biofuel production. This study developed an integrated, field scale, and process-based ecosystem model (DRAINMOD-GRASS) for simulating hydrological processes, soil carbon and nitrogen cycling, and plant growth in cropping systems for producing bioenergy grasses in lowland areas. We tested the model using measurements from three replicated switchgrass (Panicum virgatum) plots located in eastern North Carolina, USA. Results showed that the model accurately predicted 5-year (2009–2013) biomass yield. Predicted daily water table depth closely matched field measurements with Nash-Sutcliffe coefficient of 0.86. The model also accurately predicted temporal dynamics of daily soil moisture and temperature with Nash-Sutcliffe coefficients of 0.7 and 0.9, respectively. Predicted seasonal changes in net N mineralization and nitrification rates were comparable to field measurements in 2011 and 2012.

RETRACTED: Application of adaptive neuro-fuzzy technique to determine the most relevant variables for daily soil temperature prediction at different depths

RETRACTED: Application of adaptive neuro-fuzzy technique to determine the most relevant variables for daily soil temperature prediction at different depths

Efeito de coberturas do solo sobre a sobrevivência de Macrophomina phaseolina no feijão-caupi

RESUMO Com o objetivo de avaliar a sobrevivência de Macrophomina phaseolina em solo submetido a diferentes coberturas, conduziu-se dois experimentos em casa de vegetação, no delineamento inteiramente casualizado, em esquema fatorial 5 x 2, com cinco coberturas (Brachiaria brizantha, Pennisetum glaucum, Crotalaria spectabilis, solo coberto com filme de polietileno e solo sem cobertura) e solo esterilizado e não esterilizado. No primeiro experimento, as plantas foram cultivadas em vasos e dessecadas, para posterior plantio do feijão-caupi e no segundo, a semeadura da cultura foi realizada em sucessão ao primeiro cultivo. Nos dois experimentos foram colocadas em cada vaso a 10 cm de profundidade, no dia do plantio da cultura, quatro bolsas de tecido contendo, cada uma, 10 gramas de inóculo de M. phaseolina, das quais, duas foram retiradas aos 30 dias após o plantio e duas no final do ciclo da cultura, para posterior plaqueamento e determinação da sobrevivência. Realizou-se também o monitoramento das temperaturas máximas e mínimas diárias do solo. Os tratamentos com solo coberto com material vegetal apresentaram menor elevação da temperatura em relação ao solo coberto com filme de polietileno e sem cobertura, que elevaram a temperatura em até 5,9 e 3,9 ºC, respectivamente, em relação ao solo coberto com palhada de P. glaucum. O solo coberto com filme de polietileno e sem cobertura apresentaram maiores taxas de sobrevivência de M. phaseolina e o solo coberto com palhada de P. glaucum a menor taxa. Maior sobrevivência foi observada no solo não esterilizado.

The effect of biochar application on thermal properties and albedo of loess soil under grassland and fallow

There is sparse peer-reviewed literature on the biochar effects on the thermal properties of soils although they play an important role in the soil energy balance and resulting temperature distribution. The objective of this study was to quantify the effect of biochar from wood off cuts on the thermal conductivity, heat capacity, thermal diffusivity, albedo, water content, and bulk density of loess soil under grassland (G) and fallow (F) in the temperate climate of Poland. The biochar at an amount of 0, 10, 20, and 30Mgha−1 was incorporated to a depth of 0–15cm under F and remained on the surface under G. All field measurements were done on 24 occasions from spring to autumn in 2013–2014. Additional laboratory measurements of the thermal properties in water saturated (Wet) and dry (Dry) states. Incorporation of biochar under the F led to reduced soil bulk density and particle density from 1.18–1.20Mgm−3 and 2.48–2.55Mgm−3 under F0 and F10 to 1.00Mgm−3 and 2.20Mgm−3 under F30, respectively. The field measured average water contents were greater under F while the minimum ones were lower in biochar-amended than control soil without biochar. In general, the average thermal conductivity and thermal diffusivity and values of thermal conductivity at the saturation and dry state under F in general decreased with the increasing biochar application rate. After biochar addition, the albedo decreased with the increasing biochar application rate and was considerably greater under F than G. After rain, there was substantial reduction of the albedo under F in contrast to G, where it was increased. Changes in the soil thermal properties in response to biochar application were most pronounced under F and those in albedo under G. Irrespective of the biochar application rate, the average thermal conductivity and water content were greater under G than F. The daily soil temperature amplitude in biochar amended plots decreased under G and increased under F. The use of the statistical-physical model showed that the rate of the increase in the thermal conductivity and thermal diffusivity with increasing soil water content was greater in soil with greater rather than lower bulk density. The relatively wide range of variations suggests that biochar application can be an important factor in regulation of the thermal soil properties and albedo as well as climate change.

INVESTIGATION OF GROUND TEMPERATURE FOR HEAT SINK APPLICATION IN KUCHING, SARAWAK, MALAYSIA

Ground Air Heat Exchanger (GAHE) may be a solution to improve thermal comfort in buildings located in Sarawak but no ground survey specifically to examine the potential of GAHE has been done. Ground temperature prediction with computer program did not provide an accurate result for this region. In this study, a few sites with different soil profile in Kuching, Sarawak were selected to determine the soil temperature up to 4 meters depth. For peat soil area with high water table, the ground mean temperature is about 28 °C after 1m depth. For sandy clay type soil which is subjected to tidal activity, the daily soil temperature fluctuates greatly with the highest maximum temperature exceeding 32°C for all depth. This behavior is not really desirable if the ground were to be used as a steady heat sink source. Red podzolic soil gave an almost flat profile between 26°C to 27°C after the depth of 1m which is more desirable as a ground heat sink source. Therefore earth tube application in the state of Sarawak should consider the type of soil profile and optimum depth of to take advantage of the cool ground to provide building cooling.

The estimation of daily mean soil temperature at different depths in three Agroecological regions of Sri Lanka

Soil temperature is an important climatic variable in regulating ecosystem process, yet it is difficult and costly to measure daily. Several mathematical models are available to estimate soil temperature; however, most are with complicated independent variables. In this research, site specific parsimonious models were developed to estimate daily mean soil temperature in deeper depths (i.e.>10 cm) using air temperature, soil temperature at 5 cm depth and day of the year as independent variables. Different models were developed for four Coconut growing sites and results showed that 5 cm depth soil temperature along with day of the year estimate the soil temperature at deeper depths with high accuracy. Further, models with air temperature and day of the year estimate the soil temperature at 5 and 10 cm depths satisfactorily. These models can be used to estimate the daily mean soil temperature simply and cost effectively and it also allows the reconstruction of missing soil temperature values. COCOS Vol. 20: 9-25 (2013)

Temperature regimes of northern taiga soils in the isolated permafrost zone of Western Siberia

Soil temperature regimes were studied in three ecosystems of the north of Western Siberia in the zone of isolated permafrost: the forest ecosystem with gleyic loamy sandy podzol (Stagnic Albic Podzol), the flat-topped peat mound ecosystem with humus-impregnated loamy sandy to light loamy peat cryozem (Histic Oxyaquic Turbic Cryosol (Arenic)), and the peat mound (palsa) ecosystem with oligotrophic destructive permafrost-affected peat soil (Cryic Histosol). Annual temperature measurements in the soil profiles demonstrated that these soils function under different temperature regimes: very cold permafrost regime and cold nonpermafrost regime. The following annual temperature characteristics proved to be informative for the studied soils: sums of above-zero temperatures at the depths of 10 and 20 cm, the maximum depth of penetration of temperatures above 10°C, and the number of days with daily soil temperatures above (or below) 0°C at the depth of 20 cm. On the studied territory, the insulating effect of the snow cover in winter was at least two times more pronounced than the insulating effect of the vegetation cover in summer. Cryogenic soils of the studied region are characterized by the high buffering towards changing climatic parameters. This is explained by the presence of the litter and peat horizons with a very low thermal diffusivity and by the presence of permafrost at a relatively shallow depth with temperature gradients preventing penetration of heat to the permafrost table.

Effect of Drill-Seeded Soybean Density and Residual Herbicide on Palmer Amaranth (Amaranthus palmeri) Emergence

Palmer amaranth is the most troublesome weed of soybean in the southern United States. Field experiments were conducted at two Arkansas locations to determine the effect of drill-seeded soybean density on Palmer amaranth emergence. Experimental factors were multiple soybean seeding rates planted on a 19-cm-wide row spacing and the presence or absence of a PRE residual herbicide (flumioxazin plus pyroxasulfone). Soybean groundcover was measured throughout the growing season and daily soil temperature was recorded in selected soybean densities. In the absence of a PRE residual herbicide, at least a 1.7-fold reduction in Palmer amaranth emergence occurred when soybean were present. Differences in Palmer amaranth emergence occurred among soybean densities for both locations, suggesting the value of crop canopy in preventing Palmer amaranth emergence in the absence of an effective residual herbicide. In plots treated with the PRE herbicide, no difference in Palmer amaranth emergence occurred among soybean densities, except for the absence of soybean. Achievement of 95% groundcover by soybean reduced daily soil temperature fluctuations, which in turn reduced Palmer amaranth emergence. For both locations, soybean grain yields were greatest at the highest seeding rate (617,500 seed ha−1). In the presence of flumioxazin plus pyroxasulfone applied PRE, greater grain yields occurred compared to the absence of a PRE herbicide at both Fayetteville and Marianna. Based on this research, an effective PRE-applied residual herbicide has more influence on Palmer amaranth emergence than soybean density, and Palmer amaranth germination and emergence are dependent upon daily soil temperature fluctuations, which is a function of soybean density.

Changes in the 1963–2013 shallow ground thermal regime in Russian permafrost regions

Spatial variability and temporal trends of the shallow ground thermal regime and permafrost active-layer thickness (ALT) were estimated over 1963–2013 using daily soil temperature data available from stations of the Russian Hydrometeorological Service. Correlation analysis was used to evaluate the role of changing climatic conditions on the ground thermal regime. ALT data collected by the Circumpolar Active Layer Monitoring program in Russia were used to expand the geography of ALT observations over 1999–2013, and to identify ‘hot spots’ of soil temperature and ALT change. Results indicate that a substantially higher rate of change in the thermal regime of permafrost-affected soils prevailed during 1999–2013, relative to the last fifty years. Results indicate that the thermal regime of the upper permafrost in western Russia is strongly associated with air temperature, with much weaker relationships in central and eastern Russia. The thermal regime of permafrost-affected soils shows stronger dependence on climatic conditions over the last fifteen years relative to the historical 50-year period. Geostatistical analysis revealed that the cities of Norilsk and Susuman are hot spots of permafrost degradation. Of six settlements selected for detailed analysis in various parts of the permafrost regions, all but one (Chukotka), show substantial changes in the shallow ground thermal regime. Northern locations in the continuous permafrost region show thickening of the active layer, while those farther south experienced development of residual thaw layers above the permafrost and decreases in the duration of the freezing period.

An analytical model for estimating soil temperature profiles on the Qinghai-Tibet Plateau of China

Soil temperature is a key variable in the control of underground hydro-thermal processes. To estimate soil temperature more accurately, this study proposed a solution method of the heat conduction equation of soil temperature (improved heat conduction model) by applying boundary conditions that incorporate the annual and diurnal variations of soil surface temperature and the temporal variation of daily temperature amplitude, as well as the temperature difference between two soil layers in the Tanggula observation site of the Qinghai-Tibet Plateau of China. We employed both the improved heat conduction model and the classical heat conduction model to fit soil temperature by using the 5 cm soil layer as the upper boundary for soil depth. The results indicated that the daily soil temperature amplitude can be better described by the sinusoidal function in the improved model, which then yielded more accurate soil temperature simulating effect at the depth of 5 cm. The simulated soil temperature values generated by the improved model and classical heat conduction model were then compared to the observed soil temperature values at different soil depths. Statistical analyses of the root mean square error (RMSE), the normalized standard error (NSEE) and the bias demonstrated that the improved model showed higher accuracy, and the average values of RMSE, bias and NSEE at the soil depth of 10-105 cm were 1.41°C, 1.15°C and 22.40%, respectively. These results indicated that the improved heat conduction model can better estimate soil temperature profiles compared to the traditional model.

Soil respiration patterns for four major land-use types of the agro-pastoral region of northern China

Land-use types and management practices are critical factors that affect soil CO2 efflux (Rs). In the agro-pastoral area of northern China, land-use types have changed considerably during the last 60 years due to changes in the social-economic status of the human population and associated changes in land-use needs. Only a few studies have examined Rs in this region of China, and these studies have mainly focused on grazing intensity effects on Rs rather than comparisons among land-use types. The aim of this study was to evaluate annual variation of Rs for the dominant land-use types in the agro-pastoral region of northern China, including ungrazed grassland (UG), moderately grazed grassland (MG), perennial pasture (PP), and cropland (CL). Measurements of Rs were obtained throughout the year for these four land-use types using a mobile greenhouse gas analyzer. Values of Rs from the four land-use types for the growing season, non-growing season, and across the entire year were in the order PP>CL>UG>MG. Annual values of Rs in PP and CL were 1.6- and 1.1-fold greater, respectively, than that for UG, while Rs in MG was 94% of UG. Daily mean soil temperature (Ts) was the main factor that controlled Rs and explained 52–71% of the variability in daily Rs. Monthly mean temperature and precipitation explained 67–87% of the variability in monthly cumulative Rs. Annual Rs for all land-use types averaged 1.9kgCm−2yr−1 (range: 1.6–2.5) with about 94% of annual Rs occurring during the growing season. No pulses of Rs were observed during the autumn and spring freeze-thaw period, probably because of the large snow accumulation, which minimized Rs during these two periods. These results showed that land-use types exhibit different Rs that were associated with differences in temperature and precipitation. Results also suggest that conversion of UG or MG to CL and PP will likely increase Rs.

Maize (Zea mays L.) yield and soil properties as affected by no tillage in the black soils of China

A four-year tillage experiment on maize was conducted in the high latitude region of Northeast of China. The main objective of this study was to investigate the effects of different field tillage practices on maize grain yield, soil physical properties, and soil water and temperature dynamics in Northeast of China. The tillage practices included moldboard plow tillage (MOT), rotary tillage (ROT), reduced tillage (RET), combined tillage (COT), and no tillage (NOT). The surface soil water content at depths of 0–20 cm was higher under NOT compared with other tillage practices, but not different at the deeper soil depths in 2011. The soil temperatures under NOT and RET were lower than those under moldboard plow tillage and ROT at depths of 5 and 15 cm, respectively, measured at 9:00 am in 2005. From the hourly dynamics of soil temperature, the differences among the tillage practices mainly appeared during the daytime (from 8:00 am to 7:00 pm). Among all the practices, the average daily soil temperature under ROT was the highest, while that under NOT was the lowest. MOT, ROT, and RET had higher soil accumulative infiltration compared with NOT and COT. The surface soil bulk density under NOT was higher than or equal to that under the other four tillage practices. The maize yields under NOT were the lowest among all the tillage practices for three years straight. Meanwhile, the yields under MOT were the highest, which were about 47%, 61%, and 38% higher than those under NOT. NOT practice is not recommended for use in spring-planted maize under the high latitude humid cool climate Mollisol region in Northeast of China.

Evaluate the effect of mulches on soil temperature, soil moisture level and yield of capsicum (Capsicum annuum) under drip irrigation system

Drip irrigation with mulches is the best suitable approach for conservation of moisture and for producing higher yield to fulfill the food demand in the country. Therefore, this experiment was laid out to evaluate the effect of mulches on soil temperature, soil moisture level and yield of capsicum ( Capsicum annum ) at Precision Farming Development Centre of Indira Gandhi Krishi Vishwavidyalya, Raipur. The daily soil temperature observation were taken from 15 January, 2010 to 03 March, 2011 at 7:30 AM and 2:00 PM. Soil thermometer was used for the measurement of soil temperature. The black plastic mulch (BPM), paddy straw mulch (PSM) and without mulch (WM) with four level of irrigation were taken to study the effect on growth and yield of capsicum. It is concluded from the study that at 7:30 AM the average soil temperature under black plastic mulch (BPM) was 1.29 and 1.93°C higher as compared to the paddy straw mlch (PSM) and without mulch (WM), respectively. At 2:00 PM under BPM the average soil temperature increased by 4.6 and 1.62°C compared to under PSM and WM condition, respectively. At the same time the average soil temperature of under WM was 3.0°C more as compared to PSM condition. PSM kept the soil temperature less than WM. It was also found that the soil temperature under PSM was higher than the WM condition, when the atmospheric temperature was low in the morning. From the analysis it is concluded that BPM saved significantly higher soil moisture (49%) as compared to paddy straw mulch at 15 cm soil depth, similarly BPM saved 44 per cent more soil moisture as compared to paddy straw mulch at 30 cm soil depth. BPM with 80 per cent irrigation level gave maximum yield 20802.40 kg/ha, followed by BPM+100 per cent irrigation level which gave 20000.00 kg/ha. Minimum yield was found in without mulch with control irrigation condition.

Temporal variability and covariance structures of soil temperature in a sugarcane field under different management practices in southern Brazil

Extreme soil thermal regimes adversely affect soil functioning and reduce crop productivity. Thus, there is the need to understand the extent which soil tillage and mulching can modify extreme soil temperature conditions for optimum crop growth and productivity. The objective of this study was to investigate the residual effect of tillage and introduction of straw mulching on the temporal variability and covariance structures of soil temperature of a sugarcane field in southern Brazil during the 2011/2012 growing season. The experiment was laid out in a randomized complete block design (RCBD), with split-plot arrangement in three replications. The main treatment consisted of no tillage (NT), chiseling (Chi), compacted no tillage (NTC) and conventional tillage (CT) imposed a year before this study while the sub-plots (new treatments) were straw mulching and no mulching of previous sugarcane trash. Soil bulk density was determined at the middle of soil layers 0–10, 10–20, 20–40 and 40–60cm using the core method. Soil water content (SWC) and temperature were monitored at the middle of soil layers 0–5, 5–10, 10–20, 20–40 and 40–60cm, respectively in each treatment using TDR and copper-constantan sensors. Soil water content was measured manually while soil temperature data was recorded automatically every thirty (30) minutes. BD was highest (1.76gcm−3) in the 10–20cm layer of NTC treatment. SWC was lower in the surface layer of all tillage treatments, while straw mulch plots exhibited higher SWC values. Higher average, maximum, minimum and amplitude of soil surface temperature were observed in NTC and NT treatments. Straw mulching significantly influenced the soil thermal regime, as it suppressed the maximum soil surface temperature by 11°C and the average daily temperature by about 4°C during the critical summer period. During the critical winter season, daily average and maximum soil temperatures increased by about 3 and 4°C by straw mulch, respectively. Straw mulching influenced temporal covariance structure of soil temperature. Applied statistical time series analysis of daily soil temperature used certain proportion of previous observations, gave higher coefficient of determination as well as being able to incorporate measurement and model errors, making it better than the corresponding classical linear regression procedure. This study showed that straw mulching could mitigate deleterious effects of supra-optimal temperature and protect the soil from sub-zero thermal conditions during the extreme summer and winter periods, respectively.

Improved yield by harvesting water with ridges and subgrooves using buried and surface plastic mulchs in a semiarid area of China

This paper determines the responses of soil temperature, water status and crop yields to a new planting pattern involving ridges and subgrooves with plastic film mulching in a millet-field pea-spring wheat-potato cropping system. The study was conducted in a typical semiarid area, during the four annual growing seasons of 2005–2008 and five treatments were designed: (1) a flat plot with no mulching, which is the conventional tillage practice (CK); (2) alternating ridges and furrows with no mulching (M0C0); (3) alternating ridges and furrows with no mulching, and subgrooves mulched with plastic film (M0C); (4) alternating ridges and furrows, with only the ridges mulched with plastic film on the surface (MC0); and (5) alternating ridges and furrows, as well as subgrooves, with the ridges and subgrooves mulched with plastic film (MC). The subgrooves with plastic film mulching increased topsoil temperature, the average daily soil temperature of the 4-growing seasons was 16.7, 16.8, 16.9, 17.4 and 17.2°C for the CK, M0C0, MC0, M0C and MC, respectively. The soil temperature was significantly higher in the M0C and MC than in the CK, M0C0 and MC0 in May 2006, September in 2007 and May 2008. In average and wet years, the soil water content in the 20–40cm soil layer was 6.2–37.7% higher in the MC than in the CK. The ridges and subgrooves with plastic film mulching improved crop yields, and the average yield over the four years was higher in the MC than in the CK, M0C0, M0C and MC0 by 163%, 98%, 62% and 21%, respectively. Potato is a staple and economic crop in this region, and the ratio of large and moderate-sized potato tuber yield to total tuber yield was 21.7% higher in the treatments with subgrooves than in the treatments without subgrooves. In conclusion, the technique of ridges and subgrooves with plastic film mulching is an effective practice for improving crop yields in semiarid agroecosystems.