Maximum Soil Temperature Research Articles

INFLUENCE OF SOIL MOISTURE CONTENT ON SOIL SOLARIZATION EFFICIENCY

The experiments of this study were carried out to investigate how soil temperature is influenced by different soil moisture content regimes during soil solarization. The ten plots were brought to five volumetric moisture regimes (M1-M5). The moistened soils were mulched with 100-μm-thick black and transparent polyethylene covers. Maximum and minimum soil temperatures for depths of 10, 20 and 30 cm were recorded from 1 June to 30 July, 2010at Faculty of Agriculture, Omar Al-Mukhtar University, El-Beida, Libya. For black and transparent covers, the results showed that the maximum soil temperatures decreased with increasing soil moisture content. Moreover, soil solarization efficiency decreased with increasing moisture content. The higher temperatures under the M4 (0.39 and 0.37 m3/m3 at start solarization) irrigation regime resulted in faster eradication of the pathogenic fungus.

Effect of Mulching on Soil Temperature and Moisture Regime on Emergence, Growth and Yield of White Yam in a Tropical Wet-and-Dry Climate

An on-farm yam experiment was conducted to study the effect of mulching on soil temperature and moisture regime on white yam (Dioscorea rotundata) growth and yield in Abeokuta, South-western Nigeria. Three mulching options (grass mulched, polythene mulched and unmulched) was selected and related to crop growth and yield. Grass mulch sig- nificantly (P < 0.05) lowered maximum soil temperature by 1-2℃ at 15cm depth during the thermal critical period (Janu- ary - March). This led to higher rate of emergence which accounted for 28 and 46% to the polythene mulch and the un- mulched plots respectively. Furthermore, grass mulch had tuber yield of about 4-6 tonnes ha-1 season-1 greater than the polythene mulch and the unmulched plots. Irrespective of mulching materials, it was found that mulching significantly (P< 0.05) increased tuber yield by about 6-8 tonnes ha-1 season-1 than the unmulched. The effect of grass mulch over nylon mulch on yam performance in the study was also discussed.

Soil Temperature Prediction on Farmland Water Level and Environmental Factors Paddy Based on BP-ANN Model

The main environmental factors of the influence of soil temperature are air temperature, total solar radiation, effective photosynthetic radiation, wind speed and relative humidity, while the farmland water and submerging duration are the main factors affecting the change of soil temperature, and it exist complex non linear relationship between them. The aim of this study was constructed the soil temperature prediction model on farmland water level and environmental factors and obtained paddy soil temperature predictive value by using the data of existing water level and environmental factors. For the flooding treatment, the minimum and maximum soil temperature appeared at 7:00 and 18:00, for the drought treatment the minimum and maximum soil temperature respectively appeared at 6:00 and 14:00. This study trained artificial neural network based on back propagation algorithm (BP-ANN) through the existing data to predict the four characteristics the soil temperature of different water level control so as to obtain the soil temperature amplitude. Results showed that there was certain deviation between the predictive value and the actual value at the four characteristic moments, relative error were 1.19%, 1.34%, 2.09% and 1.07%, the predicted outcome was satisfactory. It is significant for guiding the rice irrigation and the production of practice facilitated.

Variations in soil temperature at BJ site on the central Tibetan Plateau

The temporal and spatial variation in soil temperature play a significant role in energy and water cycle between land surface and atmosphere on the Tibetan Plateau. Based on the observed soil temperature data (hourly data from 1 January 2001 to 31 December 2005) obtained by GAME-Tibet, the diurnal, seasonal and interannual variations in soil temperature at BJ site (31.37° N, 91.90° E; 4509 a.s.l.) near Naqu in the central Tibetan Plateau were analyzed. Results showed that the average diurnal variation in soil temperature at 4 and 20 cm depth can be described as sinusoidal curve, which is consistent with the variation of solar radiation. However, the average diurnal variation in soil temperature under 60 cm was very weak. The average diurnal amplitude in soil temperature decreased by the exponential decay function with the increase of soil depth (R2=0.92, p<0.01). It is demonstrated that the average diurnal maximum soil temperature decreased by the exponential decay function with the increase of soil depth (R2 =0.78, p<0.01). In contrast, the average diurnal minimum soil temperature increased by the exponential grow function with increasing of soil depth (R2=0.86, p<0.01). There were a linear negative correlation between the average annual maximum Ts and soil depth (R2=0.96, p<0.01), a logarithmic function relationship between the average annual minimum soil temperature and soil depth (R2=0.92, p<0.01). The average seasonal amplitude in soil temperature followed the exponential decay function with the increase of soil depth (R2=0.98, p<0.01). The mean annual soil temperature in each layer indicated a warming trend prominently. During the study period, the mean annual soil temperature at 4, 20, 40, 60, 80, 100, 130, 160, 200 and 250 cm depth increased by 0.034, 0.041, 0.061, 0.056, 0.062, 0.050, 0.057, 0.051, 0.047 and 0.042 °C /a, respectively.

Effects of Hay Mulch on Soil Properties and Potato Tuber Yield under Irrigation and Nonirrigation in New Brunswick, Canada

Organic mulching and irrigation are considered to be important soil conservation and agricultural practices. However, the effectiveness of these practices on soil properties and potato production in the relatively cool, moist maritime region of Canada has not yet been well studied. In the growing seasons of 2000–2003, a field experiment was conducted at the Potato Research Centre, Agriculture and Agri-Food Canada, Fredericton, New Brunswick, to assess the benefits of hay mulching on a loamy sand soil under potato production. Treatments consisted of four levels of hay mulching: 0, 2.25, 4.5, and 9.0 Mg ha-1 with four replicates under irrigation or nonirrigation. Results showed that hay mulching could help conserve soil moisture in nonirrigation treatments with an increase of mean soil moisture content by 5.7 to 9.5% under 2.25 to 9.0 Mg ha-1 of hay mulch relative to a control. The greatest conservation effect on soil water in our region would be achieved with a mulch rate of 5.6 Mg ha-1. Under irrigation, mulching slightly increased soil temperature. Without irrigation, soil temperature was affected both positively and negatively by mulching, depending on time of day and quantity of mulch applied. During periods of warmer weather, mulching reduced maximum soil temperature during daytime but increased minimum soil temperature during nighttime. While the magnitude of soil temperature change was slight, it varied linearly with mulch quantity. During periods of cold weather, mulching generally increased soil temperature. The soil organic carbon content in the year following mulching increased proportionally with the amount of mulch applied in the nonirrigated treatments. Thus, thicker mulching treatments resulted in a greater increase in soil organic matter accumulation. Irrigation was found to potentially induce organic matter loss for the lower mulching treatment (2.25 Mg ha-1) and control. No significant effects of hay mulching on total potato tuber yield under irrigation were found, but tuber yield under nonirrigation increased linearly with the amount of mulch applied.

Models for estimation of hourly soil temperature at 5cm depth and for degree-day accumulation from minimum and maximum soil temperature

A model has been developed for the daily variation in soil temperature at 5 cm depth, for use where both the minimum and maximum temperatures are known or can be estimated. The model is based on data from three Australian sites with minute-by-minute data over 3–7 years. The model uses two sine curves; one for the increase from minimum to maximum and another for the relatively rapid decrease in temperature immediately after the maximum. An exponential decay function is used for the slower decrease in temperature until the minimum is reached. The time of the minimum soil temperature is primarily determined by the time of sunrise and therefore varies depending on the day of the year, whereas the time of the maximum temperature is influenced primarily by the time of the middle of the day (midpoint between sunrise and sunset). The time of the transition point between the maximum and the next minimum is related to the time of sunset. Therefore, the model uses latitude, longitude, and the day of the year to determine the time of sunrise and sunset to adjust the shape of the temperature profile throughout the day. The model has been validated using 3-hourly soil temperature data for 35 other sites in Australia, with a correlation of 0.993 between actual 3-hourly temperatures and those predicted. Its use for degree-day calculations has been validated using hourly data from a site in Victoria, where the model’s estimates of degree-days differ &lt;0.7% from the value based on individual hourly temperatures, whereas methods that assume a symmetrical change from maximum to minimum temperature overestimate degree-days by 6–7%.

Summer Cover Crops Fix Nitrogen, Increase Crop Yield, and Improve Soil–Crop Relationships

Impact of cover crops (CCs) on winter wheat (Triticum aestivum L.) and grain sorghum [Sorghum bicolor (L.) Moench] yields is not well understood. We assessed crop yield and its relationships with CC‐induced changes in soil properties for a 15‐yr CC experiment in wheat–sorghum rotation at 0, 33, 66, and 100 kg ha−1 of N application in south central Kansas. Hairy vetch (Vicia villosa Roth) was used as a winter CC from 1995 to 2000, while sunn hemp (SH; Crotalaria juncea L.) and late‐maturing soybean [LMS; Glycine max (L.) Merr.] were used as summer CCs in no‐till from 2002 to 2008. Summer CCs increased crop yields particularly at low rates of N application. At 0 kg N ha−1, SH increased sorghum yield by 1.18 to 1.54 times, while wheat yield increased by 1.60 times in the first year (2004) after CC establishment relative to non‐CC plots. At 66 kg N ha−1, SH had no effects on sorghum yield, but it increased wheat yield in 2 of 3 yr. Cover crops increased soil total N pool by 270 kg ha−1 for the 0‐ to 7.5‐cm depth. Crop yield increased with the CC‐induced decrease in soil maximum compactibility (soil's susceptibility to compaction) and soil temperature, and increase in soil aggregate stability, soil organic carbon (SOC) and total N concentration, and soil water content, particularly at 0 kg N ha−1. Principal component analysis (PCA) selected soil compactibility and total N as the best yield predictors. Inclusion of summer legume CCs in no‐till fixes N, increases crop yield, and improves soil–crop relationships.

Enhanced Soil Solarization againstFusarium oxysporumf. sp.lycopersiciin the Uplands

Soil solarization tests againstFusarium oxysporumf. sp.lycopersici, the causal agent of tomato Fusarium wilt, were conducted for seven weeks through July and August 2008 and 2009 in the climatic conditions of Al-Aroub Agricultural Experimental Station, located in the southern mountains of the West Bank, Palestine. Double polyethylene (DPE) sheets, regular polyethylene (PE) sheets, and virtually impermeable films (VIF) were compared to examine their effects on soil temperature, disease severity, and plant growth. Results showed that in comparison to the control, PE, DPE, and VIF treatments increased the mean maximum soil temperatures by 10.2, 14.1, and 8.8°C, respectively, in 2008 and by 10.2, 12.6, and 8.3°C respectively, in 2009. The longest length of time recorded for temperature above 45°C under DPE sheets were 220 hours in 2008 and 218 hours in 2009. The treatments reduced the pathogen population by 86% and the disease by 43% under the DPE treatment in 2009 and to a lesser extent by the other treatments. Increases of up to 94% in fresh plant weight and up to 60% in plant dry weight were evident under the same treatment. The treatments also increased soil organic matter, both nitrogen forms, and major cations.

Influence of soil hydrothermal environment, irrigation regime, and different mulches on the growth and fruit quality of strawberry (Fragaria × ananassa L.) plants in a sub-temperate climate

SummaryThe present study was undertaken over two consecutive years under sub-temperate climatic conditions in the mid-hill region of Himachal Pradesh (30°52'N, 77°11'E; 1,175 m asl) on loamy sand Inceptisols. The aim was to investigate the effects of irrigation and mulch material on the growth, flowering, fruiting behaviour, relative leaf water content (RLWC), yield, and quality of strawberry (Fragaria × ananassa L. ‘Chandler’). The drip irrigation treatments included irrigation with 100, 80, or 60% (coded 1.0, 0.8, and 0.6 V) of the total water requirement. Both mulches increased the minimum soil temperature to a depth of 5 cm. The drip and surface irrigation treatments raised the minimum soil temperature by 3.0º – 5.4ºC, and lowered the maximum temperature by 2.2º – 5.8ºC compared to the rainfed control. Hay mulch was more effective in raising the minimum temperature and lowering the maximum soil temperature than black polyethylene mulch. Moisture conservation increased by 2.8 – 12.8% under the black polyethylene mulch compared to the no-mulch treatment. Drip and surface irrigation methods, as well as mulching, were found to be effective for enhancing the growth, irrigation water use efficiency (IWUE), fruit yield, and quality of strawberry plants. However, the number of crowns per plant, the percentage berry set, the RLWC, root length density (RLD), and fruit yield were highest under treatment M3I3 [i.e., black polyethylene mulch plus drip irrigation (1.0 V)] by 565.5%, 94.5%, 32.8%, 394.5%, and 549.6%,respectively, compared to the no mulch plus rainfed control. The maximum IWUE values for plant biomass [1.39 metric tonnes (MT) ha–1 m–1] and fruit yield (2.79 MT ha–1 m–1) were recorded under treatment M3I5 [i.e., black polyethylene mulch plus drip irrigation (0.6 V)]; whereas, the lowest values (0.39 and 0.68 MT ha–1 m–1, respectively) were observed using treatment M1I2 (i.e., without mulch, plus surface irrigation). Fruit size, weight, sugar content, and anthocyanin content increased significantly under treatment M2I3 [i.e., hay mulch, plus drip irrigation (1.0 V)] compared with all other treatments. Total soluble solids (TSS) contents and total acidity (TA) were highest under treatment M1I1 (i.e., no mulch, plus rainfed). A linear regression model could describe the variations in quality parameters of strawberry plants grown under sub-temperate climatic conditions. Root density was found to be the best indicator with which estimate fruit quality.

Relationship between soil temperature and fruit colour development of 'Clemenpons' Clementine mandarin (Citrus clementina Hort ex. Tan).

In Citrus, root temperature regulates rind colouration. However, few studies have investigated the range of temperatures and timing which determine rind colour break. The objective of this study was to determine the relationship between range of soil temperature (ST) and rind colour development in the precocious ‘Clemenpons’ Clementine mandarin. Reflective white plastic mulch was used to modify root temperature. Mulching increased reflected light and reduced daily maximum ST and temperature range, major differences being established 70-30 days before harvest. Rind colour-break correlated positively with 20 °C < ST < 23 °C; thus, 20-23 °C appears to be the ST threshold interval for fruit colouration. The sooner the soil reached it, the sooner the fruit changed rind colour. In our experiments, control trees accumulated 565 h at this ST interval before fruit changed colour, whereas in treated trees it occurred 2 weeks earlier. Hence, in treated trees the colour break was advanced by 2 weeks and this increased the percentage of fruit harvested at the first picking date by up to 2.5-fold. Fruit colour-break does not take place at a certain ST, but after several hours at a ST of 20-23 °C. In our experiments, reducing ST during the 2 months before harvest advances the first picking date in the ‘Clemenpons’ Clementine mandarin.

AGRONOMIC AND ECONOMIC EVALUATION OF PERMANENT RAISED BEDS, NO TILLAGE AND STRAW MULCHING FOR AN IRRIGATED MAIZE-WHEAT SYSTEM IN NORTHWEST INDIA

SUMMARYNo-tillage and raised beds are widely used for different crops in developed countries. A field experiment was conducted on an irrigated maize-wheat system to study the effect of field layout, tillage and straw mulch on crop performance, water use efficiency and economics for five years (2003–2008) in northwest India. Straw mulch reduced the maximum soil temperature at seed depth by about 3 °C compared to the no mulch. During the wheat emergence, raised beds recorded 1.3 °C higher soil temperature compared to the flat treatments. Both maize and wheat yields were similar under different treatments during all the years. Maize and wheat planted on raised beds recorded about 7.8% and 22.7% higher water use efficiency than under flat layout, respectively. Straw mulch showed no effect on water use and water use efficiency in maize. The net returns from the maize-wheat system were more in no tillage and permanent raised beds than with conventional tillage. Bulk density and cumulative infiltration were more in no tillage compared with conventional tillage.

Satellite-based and mesoscale regression modeling of monthly air and soil temperatures over complex terrain in Turkey

Simple regression algorithms were developed to quantify spatio-temporal dynamics of minimum and maximum air temperatures ( T min and T max, respectively) and soil temperature for a depth of 0–5 cm ( T soil-5cm) across complex terrain in Turkey using Moderate Resolution Imaging Spectroradiometer (MODIS) data at a 500-m resolution. A total of 762 16-day MODIS composites (127 images × 6 bands) between 2000 and 2005 were averaged over a monthly basis to temporally match monthly T min, T max, and T soil-5cm from 83 meteorological stations. A total of 60 (28 temporally averaged plus 32 time series-based) linear regression models of T min, T max, and T soil-5cm were developed using best subsets procedure as a function of a combination of 12 explanatory variables: six MODIS bands of blue, red, near infrared (NIR), middle infrared (MIR), normalized difference vegetation index (NDVI), and enhanced vegetation index (EVI); four geographical variables of latitude, longitude, altitude, and distance to sea (DtS); and two temporal variables of month, and year. The best multiple linear regression models elucidated 65% (RMSE = 5.9 °C), 65% (RMSE = 5.1 °C), and 57% (RMSE = 6.9 °C) of variations in T min, T max, and T soil-5cm, respectively, under a wide range of T min (−34 to 25 °C), T max (0.2–47 °C) and T soil-5cm (−9 to 40 °C) observed at the 83 stations.

Leaf litter manipulations alter soil physicochemical properties and tree growth in a Neotropical savanna

This study was aimed to assess the role that leaf litter play in nutrient cycling, nutrient soil availability and ecosystem processes in an oligotrophic tropical savanna. A four year experiment was performed in a Neotropical savanna from the Brazilian plateau (cerrado), in which litter levels were modified, and the resulting changes in biophysical and chemical soil properties were studied. Changes in organic matter decomposition, soil respiration and stem growth of the six most common tree species were also monitored. Compared to litter removal plots, double litter plots had lower maximum soil temperature and higher soil water content, and litter decomposition rates in one of three species studied, consistent with higher soil respiration rates observed in this treatment. With the exception of Ca, there were no significant differences in nutrients between the removal, natural and double litter plots, even though most nutrients tended to increase in the double litter plots by the end of the experimental period, while in the control plots nutrient levels remained relatively constant. Of the six tree species used for growth analysis, only one, Sclerolobium paniculatum, a fast growing species with shallow roots, had a significant increase in stem growth due to litter addition. Preliminary results over four years indicate that litter removal and addition resulted in some significant changes and tendencies that indicate that litter is effectively altering ecosystem processes. The information obtained also suggest that nutrient cycling in plots with natural litter levels (control plots) was in a closed loop; most nutrients released by litter decomposition and mineralization were absorbed and reutilized immediately by the plants, thus minimizing nutrient leakage outside the system.

Development and validation of a disease forecast model for Sclerotinia rot of carrot

Selected crop, microclimate and pathogen variables were monitored in carrot crops for four years to identify important variables associated with the development of Sclerotinia sclerotiorum and the start of epidemics of Sclerotinia rot of carrot. Soil moisture, and occasionally soil temperature, were the variables most closely associated with the development of apothecia and ascospores. Initial development of apothecia and ascospores occurred after one week of mean soil matric potential of −20 kPa or higher and maximum soil temperature up to 24 °C. At matric potentials of −30 to −40 kPa, development of apothecia and ascospores occurred in up to two weeks, and the occurrence of apothecia and ascospores was sporadic below −40 kPa. Preliminary risk algorithms were proposed to predict the occurrence of apothecia and ascospores, the start of epidemics, and the need for initial application of fungicides. Architectural and phenological stages of carrot development were used as primary risk factors incorporated into two predictive models. Ninety-five per cent closure of the carrot canopy was selected as a critical crop threshold to activate inoculum predictors. The critical crop thresholds to activate the disease forecasting system were 100% closure of the canopy plus 70 to 80% of plants with one to two collapsed senescing leaves and one to three healthy leaves lodged on the soil. The efficacy and accuracy of the model were tested over a two-year period. Applying the fungicide boscalid according to the forecast model resulted in equivalent disease control to using calendar-based sprays and decreased the number of fungicide applications in both years by up to 80%. Predicted inoculum values from the model were correlated with observed inoculum values at commercial field sites.

지표면 멀칭재료가 지온과 사과나무 묘목의 수체생육에 미치는 영향

본 실험은 멀칭용 P.E 필름 종류에 따른 지온변화가 사과 우량 측지묘 생산에 미치는 영향을 구명하고자 실시하였다. 투명 P.E. 필름, 흑색 P.E. 필름 피복구와 대조구로 무피복구를 두고 대목 직경이 9.1~11.0mm인 M.9 대목을 재식하였다. 대목 재식 3주 후에 사과 '시나노 스위트' 품종을 절접하였으며, 6월 중순에는 재식 당년 측지발생을 유도하기 위하여 묘목에 BA를 살포하였다. 생육기인 4월 중순부터 11월 초순까지의 대조구의 지온은 기온보다 약 <TEX>$0.7^{\circ}C$</TEX> 정도 높았고, 피복구의 지온은 대조구보다 약 <TEX>$1{\sim}5^{\circ}C$</TEX> 정도 높았다. P.E. 필름 종류별 지온은 투명 P.E. 필름 피복구가 흑색 P.E. 필름 피복구보다 약 <TEX>$2{\sim}3^{\circ}C$</TEX> 정도 높았다. 기상요소에 따른 지온의 일교차는 흑색 P.E. 필름 피복구가 시험구중 가장 낮았다. 사과 묘목의 생장과 측지 발달에 있어서는 피복구가 무피복구보다 생장이 양호하였다. 우량 측지묘 획득률은 흑색 P.E. 필름피복구가 가장 높았는데, 그 이유는 생육초기 지온이 대조구보다 높게 유지되면서 여름철에 지온이 <TEX>$35^{\circ}C$</TEX>를 넘은 적이 투명 P.E. 필름 피복구보다 많지 않았기 때문으로 추정되었다. This study was conducted to investigate the influence of different polyethylene film (P.E. film) for mulching on the changes in soil temperature and the production of good feathered apple nursery trees. M.9 rootstocks with stem diameter of 9.1~11.0 mm were planted in plots covered with different P.E. film (i.e., transparent P.E. film, black P.E. film, and bare soil as control). Three weeks after planting, the rootstocks were veneer grafted with 'Sinano Sweet' apple cultivar. In the middle of June, BA was sprayed to nursery for inducing feathering during the growing season. The soil temperature of the control was higher than air temperature by about <TEX>$0.7^{\circ}C$</TEX> from mid April to early October, and that of P.E. film mulching was about <TEX>$1{\sim}5^{\circ}C$</TEX> higher than that of the control. The soil temperature under transparent P.E. film was about <TEX>$2{\sim}3^{\circ}C$</TEX> higher than that under black P.E. film. The diurnal range of soil temperature under the black P. E. film was lowest among all treatments. The P.E. film mulching induced better tree growth and feathering than bare soil. Percentage of good feathering apple nursery of black P.E. film was highest among all treatments because the soil temperature unuder black P.E. film in the early growing season was higher than that of the control and the number of days when the maximum soil temperature was over <TEX>$35^{\circ}C$</TEX> in the summer was lower than that under the transparent P.E. film.

The paleoaltimetry of Tibet: An isotopic perspective

Stable isotopes provide a valuable perspective on the timing of elevation change of the Tibetan Plateau. We begin our paper by looking in depth at isotopic patterns in modern Tibet. We show that the δ^(18)O value of surface waters decreases systematically up the Himalayan front in central Nepal by about –2.8‰/km, in agreement with the patterns documented and modeled by previous research. On the Tibetan plateau itself there is no apparent correlation between elevation and the δ^(18)O value of flowing surface waters. Both surface waters and soil carbonates display a northward increase in δ^(18)O values, of about 1.5‰/° north of the Himalayan crest, even though elevation increases modestly. The isotopic increase with latitude reduces the isotope-elevation gradient for water in the northernmost plateau to –1 to –2‰/km. Carbonates in both soils and lakes form at higher temperatures than assumed by previous studies on the plateau. Temperature estimates from clumped-isotope (Δ_(47)) analyses of modern soil carbonates significantly exceed mean annual air T and modeled maximum summer soil temperatures by 15.8±2.8° and 9.7±2.5 °C, respectively. Similarly elevated temperatures best account for the δ^(18)O values observed in modern soil and lake carbonates. We recalculated paleoelevations from previous studies on the plateau using both higher formation temperatures and latitude-corrected isotopic values. With one notable exception, our revised model produces paleoelevation estimates very close to previous estimates. The exception is the reconstruction from late Eocene age deposits at Xoh Xil, for which we calculate elevations that are higher and much closer to the current elevation than previously reconstructed. Therefore, there is no evidence for northward progression through time of Tibetan elevation change. Instead, the available—but admittedly very scanty—evidence suggests that much of Tibet attained its modern elevation by the mid-Eocene. A truly robust test of the various geodynamic models of uplift await expansion and replication of isotopic records all across Tibet, especially in the center and north and for >15 Ma.

Impact of conservation tillage under organic mulches on the reproductive efficacy and yield of quality protein maize

The present study was carried out to evaluate the efficacy of conservation tillage under organic mulches on the reproductive developments and production potentials of Quality Protein Maize (QPM) cv. Pozarica during the period from November 2007 to April 2008. The study included tillage and zero tillage conditions and four indigenous mulches viz. water hyacinth, rice straw, rice husk and ash. All the mulches significantly modified microclimatic parameters in both tillage and zero tillage conditions. However, under non-tilth condition water hyacinth and rice straw mulches reduced the maximum soil temperature at 5 cm depth by 3.5-4.2°C and 2.4-2.7°C, respectively at 14:00 hrs and raised the minimum temperature by 1.5-2.3°C and 1.2-1.4°C at 06:00 hrs. The water retentive capacity of the mulched soil under zero tillage condition was higher at all the stages of plant growth and ranked in the order of water hyacinth&gt;rice straw&gt;rice husk&gt;ash&gt;control. The reproductive developments in mulched plants were advanced by about 1 to 10 days. Mulching practices also enhanced the number of ears plant-1, ear height, length and diameter, tassel length, number of seed rows ear-1 and seeds row-1, 1000-grains weight, weight of rachis ear-1, grain yield and higher harvest index (HI). The grain yield of mulched plants notably water hyacinth was nearly double (8.73 t ha-1) than unmulched plants (4.93 t ha-1) under non-tilth condition. The indigenous mulches especially water hyacinth and rice straw, irrespective of tilth or non-tilth conditions, appeared to be great suppressants of weed growth allowing to produce less than one third of the total biomass compared to that of control. The residual mulching effect had little or no influence on physical properties of the soil under both conditions. However, the chemical properties were favourably influenced for the follow-up crops. Key words: Conservation tillage; organic mulches; soil moisture conservation; yield; QPM. DOI: 10.4038/jas.v5i2.2782The Journal of Agricultural Sciences, 2010, vol. 5, no 2 pp.52-63

Soil properties affected by combinations of soil solarization and organic amendment

A field experiment was conducted to investigate the effects on soil properties of solarization combined with rice bran additive. The treatments included control (bare soil), black polyethylene film mulch (BM), clear polyethylene film mulch (CM), rice bran mixture (RBMx), rice bran mulch (RBM), rice bran mixture and black polyethylene film mulch (RBMx + BM), rice bran and black polyethylene film mulch (RBM + BM), rice bran mixture and clear polyethylene film mulch (RBMx + CM), and rice bran and clear polyethylene film mulch (RBM + CM). Initially, 15 kg m−2 of rice bran was applied to each treatment as the organic amendment. A cover of black or clear polyethylene film was then used to begin the soil solarization process. Approximately 49 days later, the polyethylene film was removed and five broccoli seedlings per replication were planted 6 weeks later. The combination of rice bran mixture with the clear/transparent polyethylene film mulch (RBMx + CM) raised both the mean and maximum soil temperatures over 0–30 cm of soil depth. Maximum soil temperature under the RBMx + CM treatment was the highest of all treatments (77°C) and were about 32°C greater than under the control, while it was only 52°C under RBM + BM treatment. Combining rice bran with clear/transparent polyethylene film mulch during the soil solarization process is recommended for raising soil temperatures. Further investigation over a longer period of soil solarization process with rice bran–organic amendment and polyethylene film mulch combinations is required to more accurately determine their effects on soil properties and crop production.

A weighted coefficient model for estimation of Australian daily soil temperature at depths of 5cm to 100cm based on air temperature and rainfall

Soil temperatures are related to air temperature and rainfall on the current day and preceding days, and this can be expressed in a non-linear relationship to provide a weighted value for the effect of air temperature or rainfall based on days lag and soil depth. The weighted minimum and maximum air temperatures and weighted rainfall can then be combined with latitude and a seasonal function to estimate soil temperature at any depth in the range 5–100 cm. The model had a root mean square deviation of 1.21–1.85°C for minimum, average, and maximum soil temperature for all weather stations in Australia (mainland and Tasmania), except for maximum soil temperature at 5 and 10 cm, where the model was less precise (3.39° and 2.52°, respectively). Data for this analysis were obtained from 32–40 Bureau of Meteorology weather stations throughout Australia and the proposed model was validated using 5-fold cross-validation.

Effects of fire frequency on prescribed fire behaviour and soil temperatures in dry dipterocarp forests

This study investigated how fire frequencies and fuel loads influence fire behaviour and soil heating in dry dipterocarp forests of the Huai Kha Khaeng Wildlife Sanctuary, Thailand. Fire behaviour and soil temperatures during burning were measured on a series of plots with different past fire frequencies ranging from unburned control, to rarely, infrequently and frequently burned, representing fire occurrences in 0, 1, 2 and 7 out of the past 10 years respectively. The pre-burning loads of fine fuel including grasses, herbs, shrubs, seedlings, saplings and litters increased with the length of the previous fire-free interval. The rate of spread, flame height, fireline intensity and maximum soil temperatures at any soil depths were not significantly different between the past burning regimes, so fires were classed as low-intensity and low-severity surface fire. The longest duration of heating with temperatures &gt;60°C at ground level occurred at the rarely burned site (~14 min), followed by the infrequently burned site (~12 min) and the frequently burned site (~8 min). However, the duration of heating above any given critical temperature threshold at 2- and 5-cm soil depths was less than 1 min across all regimes. From a fuel management perspective, there does not appear to be a need to carry out prescribed burns more frequently than every 6–7 years, because fine fuel loads did not continue to accumulate substantially beyond 7 years after a fire.