Abstract: Soil tillage systems can be able to influence soil compaction, water dynamics, soil temperature and crop yield. These processes can be expressed as changes of soil microbiological activity, soil respiration and sustainability of agriculture. Objectives of this study were: 1 - to assess the effects of tillage systems (Conventional System (CS), Minimum Tillage (MT), No-Tillage (NT)) on soil compaction, soil temperature, soil moisture and soil respiration and 2- to establish the effect of the changes on the production of wheat, maize and soybean. Five treatments were installed: CS-plough; MT-paraplow, chisel, rotary grape; NT-direct sowing. The study was conducted on an Argic-Stagnic Faeoziom. The MT and NT applications reduce or completely eliminate the soil mobilization, due to this; soil is compacted in the first year of application. The degree of compaction is directly related to soil type and its state of degradation. The state of soil compaction diminished over time, tending toward a specific type of soil density. Soil moisture was higher in NT and MT at the time of sowing and in the early stages of vegetation and differences diminished over time. Moisture determinations showed statistically significant differences. The MT and NT applications reduced the thermal amplitude in the first 15cm of soil depth and increased the soil temperature by 0.5-2.20C. Water dynamics and soil temperature showed no differences on the effect of crop yields. The determinations confirm the effect of soil tillage system on soil respiration; the daily average was lower at NT (315-1914 mmoli m-2s-1) and followed by MT (318-2395 mmoli m-2s-1) and is higher in the CS (321-2480 mmol m-2s-1). Comparing with CS, all the four conservation tillage measures decreased soil respiration, with the best effects of no-tillage. Although wheat production at MT and NT applications, had no significant differences soybean production was significantly affected from MT and NT applications. The differences in crop yields are recorded at maize and can be a direct consequence of loosening, mineralization and intensive mobilization of soil fertility.
Abstract: The understanding on the contribution of root respiration to total soil respiration is still very limited, especially for sugarcane. In this study, trenching experiments in sugarcane plantations were conducted to separate and investigate soil respiration for this crop. The measurements were performed for the whole growing period of 344 days to quantify root respiration. The obtained monitoring data showed that the respiration rate is increasing with the age of the plant, accounting for up to 29% of the total soil respiration before harvesting. The root to soil respiration ratio increased rapidly during the young seedling stage, i.e. first five months, then declined and finally got stabilized during yield formation and ripening stages, respectively. In addition, the results from the measurements confirmed that soil respiration was positively correlated with soil moisture content.
Abstract: A better understanding of cloud forest characteristic in a tropical montane cloud forest at Khao Nan, Nakhon Si Thammarat on climatic, vegetation, soil and hydrology were studied during 18-21 April 2007. The results showed that as air temperature at Sanyen cloud forest increased, the percent relative humidity decreased. The amount of solar radiation at Sanyen cloud forest had a positive association with the amount of solar radiation at Parah forest. The amount of solar radiation at Sanyen cloud forest was very low with a range of 0-19 W/m2. On the other hand, the amount of solar radiation at Parah forest was high with a range of 0-1000 W/m2. There was no difference between leaf width, leaf length, leaf thickness and leaf area with increasing in elevations. As the elevations increased, bush height and tree height decreased. There was no association between bush width and bush ratio with elevation. As the elevations increased, the percent epiphyte cover and the percent soil moisture increased but water temperature, conductivity, and dissolved oxygen decreased. The percent soil moistures and organic contents were higher at elevations above 900 m than elevations below.
Abstract: The study of soil for agriculture purposes has
remained the main focus of research since the beginning of civilization as humans- food related requirements remained closely linked with the soil. The study of soil has generated an interest
among the researchers for very similar other reasons including transmission, reflection and refraction of signals for deploying
wireless underground sensor networks or for the monitoring of objects on (or in ) soil in the form of better understanding of soil
electromagnetic characteristics properties. The moisture content has
been very instrumental in such studies as it decides on the resistance of the soil, and hence the attenuation on signals traveling through soil
or the attenuation the signals may suffer upon their impact on soil. This work is related testing and characterizing a measurement circuit
meant for the detection of moisture level content in soil.
Abstract: Offset Double-Disk Opener (DDO) is a popular
furrow opener in conservation tillage. It has some limitations such as
negative suction to penetrate in the soil, hair pinning and mixing seed
and fertilizer in the slot. Because of importance of separation of seed
and fertilizer in the slot, by adding two horizontal mini disks to DDO
a modified opener was made (MDO) which placed the fertilizer
between and under two rows of seed. To consider performance of
novel opener an indoor comparison test between DDO and MDO was
performed at soil bin. The experiment was conducted with three
working speeds (3, 6 and 8 km h-1), two bulk densities of soil (1.1
and 1.4 Mg m-3) and two levels of residues (1 and 2 ton ha-1). The
experimental design consisted in a (3×2×2) complete randomized
factorial with three replicates for each test. Moisture of seed furrow,
separation of seed and fertilizer, hair pinning and resultant forces
acting on the openers were used as assessing indexes. There was no
significant difference between soil moisture content in slots created
by DDO and MDO at 0-4 cm depth, but at 4-8 cm the in the slot
created by MDO moisture content was higher about 9%. Horizontal
force for both openers increased with increasing speed and soil bulk
density. Vertical force for DDO was negative so it needed additional
weight for penetrating in the soil, but vertical force for MDO was
positive and, which can solve the challenge of penetration in the soil
in DDO. In soft soil with heavy residues some trash was pushed by
DDO into seed furrow (hair pinning) but at MDO seed were placed at
clean groove. Lateral and vertical separation of seed and fertilizer
was performed effectively by MDO (4.5 and 5 cm, respectively)
while DDO put seed and fertilizer close to each other. Overall, the
Modified Offset Double-disks (MDO) had better performance. So by
adapting this opener with no-tillage drillers it would possible to have
higher yield in conservation tillage where the most appropriate
opener is disk type.
Abstract: The overall objective of this paper is to retrieve soil
surfaces parameters namely, roughness and soil moisture related to
the dielectric constant by inverting the radar backscattered signal
from natural soil surfaces.
Because the classical description of roughness using statistical
parameters like the correlation length doesn't lead to satisfactory
results to predict radar backscattering, we used a multi-scale
roughness description using the wavelet transform and the Mallat
algorithm. In this description, the surface is considered as a
superposition of a finite number of one-dimensional Gaussian
processes each having a spatial scale. A second step in this study
consisted in adapting a direct model simulating radar backscattering
namely the small perturbation model to this multi-scale surface
description. We investigated the impact of this description on radar
backscattering through a sensitivity analysis of backscattering
coefficient to the multi-scale roughness parameters.
To perform the inversion of the small perturbation multi-scale
scattering model (MLS SPM) we used a multi-layer neural network
architecture trained by backpropagation learning rule. The inversion
leads to satisfactory results with a relative uncertainty of 8%.
Abstract: Different techniques for estimating seasonal water
use from soil profile water depletion frequently do not account for
flux below the root zone. Shallow water table contribution to supply
crop water use may be important in arid and semi-arid regions.
Development of predictive root uptake models, under influence of
shallow water table makes it possible for planners to incorporate
interaction between water table and root zone into design of irrigation
projects. A model for obtaining soil moisture depletion from root
zone and water movement below it is discussed with the objective to
determine impact of shallow water table on seasonal moisture
depletion patterns under water table depth variation, up to the bottom
of root zone. The role of different boundary conditions has also been
considered. Three crops: Wheat (Triticum aestivum), Corn (Zea
mays) and Potato (Solanum tuberosum), common in arid & semi-arid
regions, are chosen for the study. Using experimentally obtained soil
moisture depletion values for potential soil moisture conditions,
moisture depletion patterns using a non linear root uptake model have
been obtained for different water table depths. Comparative analysis
of the moisture depletion patterns under these conditions show a wide
difference in percent depletion from different layers of root zone
particularly top and bottom layers with middle layers showing
insignificant variation in moisture depletion values. Moisture
depletion in top layer, when the water table rises to root zone
increases by 19.7%, 22.9% & 28.2%, whereas decrease in bottom
layer is 68.8%, 61.6% & 64.9% in case of wheat, corn & potato
respectively. The paper also discusses the causes and consequences
of increase in moisture depletion from top layers and exceptionally
high reduction in bottom layer, and the possible remedies for the
same. The numerical model developed for the study can be used to
help formulating irrigation strategies for areas where shallow
groundwater of questionable quality is an option for crop production.
Abstract: A new interface circuit for capacitive sensor is
presented. This paper presents the design and simulation of soil
moisture capacitive sensor interface circuit based on phase
differential technique. The circuit has been designed and fabricated
using MIMOS- 0.35"m CMOS technology. Simulation and test
results show linear characteristic from 36 – 52 degree phase
difference, representing 0 – 100% in soil moisture level. Test result
shows the circuit has sensitivity of 0.79mV/0.10 phase difference,
translating into resolution of 10% soil moisture level.
Abstract: To simulate expected climate change, we implemented a two-factor (temperature and soil moisture) field design in a forest in Ontario, Canada. To manipulate moisture input, we erected rain-exclusion structures. Under each structure, plots were watered with one of three treatments and thermally controlled with three heat treatments to simulate changes in air temperature and rainfall based on the climate model (GCM) predictions for the study area. Environmental conditions (including untreated controls) were monitored tracking air temperature, soil temperature, soil moisture, and photosynthetically active radiation. We measured rainfall and relative humidity at the site outside the rain-exclusion structures. Analyses of environmental conditions demonstrates that the temperature manipulation was most effective at maintaining target temperature during the early part of the growing season, but it was more difficult to keep the warmest treatment at 5º C above ambient by late summer. Target moisture regimes were generally achieved however incoming solar radiation was slightly attenuated by the structures.
Abstract: Subgrade moisture content varies with environmental and soil conditions and has significant influence on pavement performance. Therefore, it is important to establish realistic estimates of expected subgrade moisture contents to account for the effects of this variable on predicted pavement performance during the design stage properly. The initial boundary soil suction profile for a given pavement is a critical factor in determining expected moisture variations in the subgrade for given pavement and climatic and soil conditions. Several numerical models have been developed for predicting water and solute transport in saturated and unsaturated subgrade soils. Soil hydraulic properties are required for quantitatively describing water and chemical transport processes in soils by the numerical models. The required hydraulic properties are hydraulic conductivity, water diffusivity, and specific water capacity. The objective of this paper was to determine isothermal moisture profiles in a soil fill and predict the soil moisture movement above the ground water table using a simple one-dimensional finite difference model.
Abstract: In most wheat growing moderate regions and
especially in the north of Iran climate, is affected grain filling by
several physical and abiotic stresses. In this region, grain filling often
occurs when temperatures are increasing and moisture supply is
decreasing. The experiment was designed in RCBD with split plot
arrangements with four replications. Four irrigation treatments
included (I0) no irrigation (check); (I1) one irrigation (50 mm) at
heading stage; (I2) two irrigation (100 mm) at heading and anthesis
stage; and (I3) three irrigation (150 mm) at heading, anthesis and
early grain filling growth stage, two wheat cultivars (Milan and
Shanghai) were cultured in the experiment. Totally raining was 453
mm during the growth season. The result indicated that biological
yield, grain yield and harvest index were significantly affected by
irrigation levels. I3 treatment produced more tillers number in m2,
fertile tillers number in m2, harvest index and biological yield. Milan
produced more tillers number in m2, fertile tillers in m2, while
Shanghai produced heavier tillers and grain 1000 weight. Plant height
was significant in wheat varieties while were not statistically
significant in irrigation levels. Milan produced more grain yield,
harvest index and biological yield. Grain yield shown that I1, I2, and
I3 produced increasing of 5228 (21%), 5460 (27%) and 5670 (29%)
kg ha-1, respectively. There was an interaction of irrigation and
cultivar on grain yields. In the absence of the irrigation reduced grain
1000 weight from 45 to 40 g. No irrigation reduced soil moisture
extraction during the grain filling stage. Current assimilation as a
source of carbon for grain filling depends on the light intercepting
viable green surfaces of the plant after anthesis that due to natural
senescence and the effect of various stresses. At the same time the
demand by the growing grain is increasing. It is concluded from
research work that wheat crop irrigated Milan cultivar could increase
the grain yield in comparison with Shanghai cultivar. Although, the
grain yield of Shanghai under irrigation was slightly lower than
Milan. This grain yield also was related to weather condition, sowing
date, plant density and location conditions and management of
fertilizers, because there was not significant difference in biological
and straw yield. The best result was produced by I1 treatment. I2 and
I3 treatments were not significantly difference with I1 treatment.
Grain yield of I1 indicated that wheat is under soil moisture
deficiency. Therefore, I1 irrigation was better than I0.
Abstract: The soil moisture content is an important property of
the soil. The results of mean weekly gravimetric soil moisture
content, measured for the three soil layers within the A horizon,
showed that it was higher for the top 5 cm over the whole period of
monitoring (15/7/2004 up to 10/11/05) with the variation becoming
greater during winter time. This reflects the pattern of rainfall in
Ireland which is spread over the whole year and shows that light
rainfall events during summer time were compensated by loss
through evapotranspiration, but only in the top 5 cm of soil. This
layer had the highest porosity and highest moisture holding capacity
due to the high content of organic matter. The gravimetric soil
moisture contents of the top 5 cm and the underlying 5-15 and 15-25
cm layers show that bottom site of the Hill Field had higher soil
moisture content than the middle and top sites during the whole
period of monitoring.
Abstract: In order to monitor the water table depth on soil profile
salinity buildup, a field study was carried out during 2006-07. Wheat
(Rabi) and Sorghum (Kharif) fodder were sown in with three
treatments. The results showed that watertable depth lowered from
1.15m to 2.89 m depth at the end of experiment. With lower of
watertable depth, pH, ECe and SAR decreased under crops both
without and with gypsum and increased in fallowing. Soil moisture
depletion was directly proportional to lowering of watertable. With the
application of irrigation water (58cm) pH, ECe and SAR were reduced
in cropped plots, reduction was higher in gypsum applied plots than
non-gypsum plots. In case of fallowing, there was increase in pH, EC,
while slight reduction occurred in SAR values. However, soil salinity
showed an increasing upward trend under fallowing and its value in
0-30 cm soil layer was the highest amongst the treatments.
Abstract: Study of soil properties like field capacity (F.C.) and permanent wilting point (P.W.P.) play important roles in study of soil moisture retention curve. Although these parameters can be measured directly, their measurement is difficult and expensive. Pedotransfer functions (PTFs) provide an alternative by estimating soil parameters from more readily available soil data. In this investigation, 70 soil samples were collected from different horizons of 15 soil profiles located in the Ziaran region, Qazvin province, Iran. The data set was divided into two subsets for calibration (80%) and testing (20%) of the models and their normality were tested by Kolmogorov-Smirnov method. Both multivariate regression and artificial neural network (ANN) techniques were employed to develop the appropriate PTFs for predicting soil parameters using easily measurable characteristics of clay, silt, O.C, S.P, B.D and CaCO3. The performance of the multivariate regression and ANN models was evaluated using an independent test data set. In order to evaluate the models, root mean square error (RMSE) and R2 were used. The comparison of RSME for two mentioned models showed that the ANN model gives better estimates of F.C and P.W.P than the multivariate regression model. The value of RMSE and R2 derived by ANN model for F.C and P.W.P were (2.35, 0.77) and (2.83, 0.72), respectively. The corresponding values for multivariate regression model were (4.46, 0.68) and (5.21, 0.64), respectively. Results showed that ANN with five neurons in hidden layer had better performance in predicting soil properties than multivariate regression.
Abstract: Soil microbial activity is adversely affected by pollutants such as heavy metals, antibiotics and pesticides. Organic amendments including sewage sludge, municipal compost and vermicompost are recently used to improve soil structure and fertility. But, these materials contain heavy metals including Pb, Cd, Zn, Ni and Cu that are toxic to soil microorganisms and may lead to occurrence of more tolerant microbes. Among these, Pb is the most abundant and has more negative effect on soil microbial ecology. In this study, Pb levels of 0, 100, 200, 300, 400 and 500 mg Pb [as Pb(NO3)2] per kg soil were added to the pots containing 2 kg of a loamy soil and incubated for 6 months at 25°C with soil moisture of - 0.3 MPa. Dehydrogenase activity of soil as a measure of microbial activity was determined on 15, 30, 90 and 180 days after incubation. Triphenyl tetrazolium chloride (TTC) was used as an electron acceptor in this assay. PICTs (IC50 values) were calculated for each Pb level and incubation time. Soil microbial activity was decreased by increasing Pb level during 30 days of incubation but the induced tolerance appeared on day 90 and thereafter. During 90 to 180 days of incubation, the PICT was gradually developed by increasing Pb level up to 200 mg kg-1, but the rate of enhancement was steeper at higher concentrations.
Abstract: Moisture is an important consideration in many
aspects ranging from irrigation, soil chemistry, golf course, corrosion
and erosion, road conditions, weather predictions, livestock feed
moisture levels, water seepage etc. Vegetation and crops always
depend more on the moisture available at the root level than on
precipitation occurrence. In this paper, design of an instrument is
discussed which tells about the variation in the moisture contents of
soil. This is done by measuring the amount of water content in soil by
finding the variation in capacitance of soil with the help of a
capacitive sensor. The greatest advantage of soil moisture sensor is
reduced water consumption. The sensor is also be used to set lower
and upper threshold to maintain optimum soil moisture saturation and
minimize water wilting, contributes to deeper plant root growth
,reduced soil run off /leaching and less favorable condition for insects
and fungal diseases. Capacitance method is preferred because, it
provides absolute amount of water content and also measures water
content at any depth.