Root Zone Depth Research Articles

Soil enzymatic activity as a soil health indicator for mango orchards under subtropical region

The ecological significance of this study was to assess the enzymatic activities in 200 mango orchards located at subtropical region of Lucknow, UP, India. Soil biological activities were widely considered as an indicator for ecological processes undergoes dynamic changes. Keeping this in view, dehydrogenase (DHA) and fluorescein diacetate (FDA) was employed to indicate the status of these orchard ecologies from which 200 soil samples were collected from root zone depth (0-30 cm). Data showed lower activity of these enzymes; with majority falls below benchmark level; only 13.5 and 23.5% DHA and FDA were in higher category level of >1.01 µg TPF g-1 h-1 and >251 µg fluorescin g-1 h-1, respectively. Soil organic carbon falls only 28% in the category of >0.75%. Lower productivity of mango orchards was linked to lower soil enzymatic activities and associated characters. Growers could adopt better management practices to improve the condition of soil biological health.

Performance Evaluation of Subsurface Drainage System under Waterlogged Saline Vertisols for Sugarcane Crop in Ukai Kakrapar Canal Command, Gujarat

Crop productivity in canal command areas of India is declining due to waterlogging and soil salinization problems, and it is posing a big threat to livelihood security of small and marginal farmers. Subsurface drainage (SSD) technology, which restores favourable condition in the crop root zone by reclaiming waterlogged saline soils, can be one of the options to restore the crop productivity in such areas. The SSD system was installed at Mulad village in the Ukai Kakrapar canal command area, Gujarat, in the year 2012 to address the problem of drastic yield reduction of sugarcane due to twin problems of waterlogging and soil salinity in Vertisols. It was found that the SSD helped in desalination of soil profile as soil electrical conductivity was reduced to a range of 0.42 to 3.90 dS.m-1 from its initial range of 1.2 to 7.3 dS.m-1. Electrical conductivity of drained water was in the range of 1.3 to 4.4 dS.m-1. Further, there was reduction in waterlogging condition, both surface and sub-surface, as water table lowered below crop root zone depth (depth of 0.6 m) and surface water ponding duration reduced to 6-8 days from earlier 25-30 days during peak monsoon days. Overall performance of SSD system was satisfactory as average sugarcane yield in the study area increased significantly from 39.29 to 97.29 t.ha-1 as result of reduction in soil salinity and waterlogging in drainage area. Economic analysis also indicated 114% increase in benefit-cost ratio after SSD installation. Thus, large scale installation of SSD system for reclamation of waterlogged saline Vertisols is economically viable in the state of Gujarat.

Performance Evaluation of Subsurface Drainage System under Waterlogged Saline Vertisols for Sugarcane Crop in Ukai Kakrapar Canal Command, Gujarat

Crop productivity in canal command areas of India is declining due to waterlogging and soil salinization problems, and it is posing a big threat to livelihood security of small and marginal farmers. Subsurface drainage (SSD) technology, which restores favourable condition in the crop root zone by reclaiming waterlogged saline soils, can be one of the options to restore the crop productivity in such areas. The SSD system was installed at Mulad village in the Ukai Kakrapar canal command area, Gujarat, in the year 2012 to address the problem of drastic yield reduction of sugarcane due to twin problems of waterlogging and soil salinity in Vertisols. It was found that the SSD helped in desalination of soil profile as soil electrical conductivity was reduced to a range of 0.42 to 3.90 dS.m-1 from its initial range of 1.2 to 7.3 dS.m-1. Electrical conductivity of drained water was in the range of 1.3 to 4.4 dS.m-1. Further, there was reduction in waterlogging condition, both surface and sub-surface, as water table lowered below crop root zone depth (depth of 0.6 m) and surface water ponding duration reduced to 6-8 days from earlier 25-30 days during peak monsoon days. Overall performance of SSD system was satisfactory as average sugarcane yield in the study area increased significantly from 39.29 to 97.29 t.ha-1 as result of reduction in soil salinity and waterlogging in drainage area. Economic analysis also indicated 114% increase in benefit-cost ratio after SSD installation. Thus, large scale installation of SSD system for reclamation of waterlogged saline Vertisols is economically viable in the state of Gujarat.

Yüzeyaltı Damla Sulama Yöntemiyle Sulanan Yalova İncisi Sofralık Üzüm Çeşidinde Yaprak Su Potansiyeline Göre Sulama Programının Oluşturulması

This research was carried out in the Eastern Mediterranean Region of Turkey where to determine the effects of various irrigation strategies applied with subsurface drip systems on Yalova Incisi table grape variety and yield and water use efficiency along with optimal irrigation program during 2016, in the experimental fields of Alata Horticultural Research Station, Tarsus Soil and Water Resources Topcu Unit. In the study six irrigation levels (Full irrigation, TS; deficit irrigation, KS75; deficit irrigation, KS50; Partial Root-Zone Drying PRD75% , Partial Root-Zone Drying PRD50% of full irrigation treatments and Rainfed, RF) were tested. Soil water deficit in the rootzone depth was replenished to field capacity in irrigations. The experimental was carried out in randomized block design with three replications. The effect of the irrigation levels on the yield were found statistically significant. Full irrigation treatment under the produced the highest yield (30.9 t ha-1), the lowest yield was obtained in rainfed treatment plots (11.7 t ha-1). Leaf water potantial were measured throughout the growing season with a pressure chamber. The YSP values decreased with increasing water stress. Highest yields of Yalova Incisi variety can be obtained when irrigated at leaf water potential value Ψ =0.92 MPa.

Spatial-Temporal Variability of Land Surface Dry Anomalies in Climatic Aspect: Biogeophysical Insight by Meteosat Observations and SVAT Modeling

The spatial-temporal variability of drought occurrence over Bulgaria is characterized based on long-term records (2007–2018) of Meteosat information and the SVAT model-derived soil moisture availability index (referred to root zone depth, SMAI). Land surface temperature according to the satellite-derived Land Surface Analysis Satellite Application Facility Land Surface Temperature (LSASAF LST) product and SMAI were used to designate land surface state dry anomalies. The utility of LST for drought assessment is tested by statistical comparative analyses, applying two approaches, site-scale quantitative comparison, and evaluation of spatial-temporal consistency between SMAI and LST variability. Pearson correlation and regression modeling techniques were applied. The main results indicate for a synchronized behavior between SMAI and LST during dry spells, as follows: opposite mean seasonal course (March–October); high to strong negative monthly correlation for different microclimate regimes. Negative linear regressions between the anomalies of SMAI and LST (monthly mean), with a strong correlation in their spatial-temporal variability. Qualitative evaluation of spatial-temporal variability dynamics is analyzed using color maps. Drought-prone areas were identified on the bases of LST maps (monthly mean), and it is illustrated they are more vulnerable to vegetation burning as detected by the Meteosat FRP-PIXEL product. The current study provides an advanced framework for using LST retrievals based on IR satellite observations from the geostationary MSG satellite as an alternative tool to SMAI, whose calculation requires the input of many parameters that are not always available.

Effects of depth-dependent irrigation regimes and organomineral fertilizers on water use and quality attributes of sugar beet

Experiments were conducted under provincial conditions of Kayseri, Turkey, for two years in the growing seasons of 2014 and 2015 to determine the effects of irrigation water applications based on different sugar beet root zone depths and different organomineral fertilizers on sugar beet yield, root quality, water consumption, and water use efficiency. Two constant root depths (D1 = 0.9 m and D2 = 0.6 m) and one active water extraction root depth (D3= 0.4-0.9 m) were investigated. A mineral fertilizer (F1), an organomineral fertilizer (F2), and organic + mineral fertilizer (F3) were considered as the subtreatments in the experiments carried out in a completely randomized block split-split plots design with 3 replications. Despite the lower nitrogen and phosphorus quantities applied, the F2 treatment produced the same sugar beet root yield (95.31 t/ha) as F1 (88.59 t/ha) and F3 (94.56 t/ha) treatments. The irrigation water requirements of D1 for two years were 22.8% and 27.6% greater than the D2 and D3 treatments, respectively. Irrigation water use efficiencies of D2 and D3 treatments were higher than D1. Digestion and recoverable sugar percent and Na, K, and N contents of roots were not affected significantly by the treatments. Using organomineral fertilizers would offer various advantages for disposing of huge urban waste deposits and returning organic matter to agricultural areas. Use of active root water extraction depth or 0.60-m root depth for irrigation applications will also contribute to efficient use of water resources and improve the income of sugar beet farmers due to reduced irrigation costs.

Modeling site suitability and production potential of carinata-based sustainable jet fuel in the southeastern United States

Abstract The aviation sector is currently responsible for 2.6% of global carbon emissions. Carbon emissions of the aviation sector are expected to increase by 3–4% each year due to the rising demand for air travel. The use of bio-jet fuel derived from carinata (Brassica carinata) is a potential solution for mitigating carbon emissions from the aviation sector. This study determines suitable sites for growing carinata across three southeastern states of Georgia, Alabama, and Florida. Suitable edaphic (average soil storage, soil organic carbon, root zone depth) and climatic variables (temperature) along with historical land use trajectories were used for determining the land suitability for carinata production. The weights of the edaphic variables were decided by surveying experts using the Analytical Hierarchy Process. This study also determined the susceptibility of frost events in growing season of carinata from 2010 to 2017. Finally, the composite risk was calculated by multiplying the probability of potential damage risk and probability of land risk. Considering minimum risk level of 5%, about 45.56% (0.77 million ha) of land in Georgia, 0.81% (0.01 million ha) land in Alabama and about 3.04% (0.05 million ha) of land in Florida is suitable for growing carinata. Depending upon the composite risk level and expected carinata yields, the total production potential of carinata was between 1.87 and 3.91 million metric tons which was sufficient for producing between 980 and 2045 million liters of bio-jet fuel sufficient enough to replace 1.4%–2.33% of the current jet fuel consumption in the United States. Our study will feed into current policy debate about reducing carbon footprint of the aviation sector in the United States and promote development of bio-economy for rural America.

Role of Colocasia esculenta L. schott in arsenic removal by a pilot-scale constructed wetland filled with laterite soil

The role of plant Colocasia esculenta L. schott (C. esculenta) in arsenic removal was investigated in a pilot-scale constructed wetland (PCW), which was filled with laterite soil (19.90–28.25% iron by weight). This PCW consists of 2 sets of flow systems in parallel, with C. esculenta planted at a density of 20 plants/m2 in one system and the other without any plants. The synthetic water containing arsenic concentration of 0.50 mg/l, with its pH controlled at 7.0 and influent flow at 1.5 m3/day. With C. esculenta, the arsenic in water decreased from 0.485 mg/l to 0.054 mg/l (89% removal), whereas, without C. esculenta, the arsenic decreased from 0.485 mg/l to 0.233 mg/l (52% removal). As for the fate of the influent arsenic, the C. esculenta was responsible for 65% of arsenic accumulation. Note that the arsenic was found mostly within the root zone depth (20–40 cm). It appears that such a high capacity of arsenic removal was enhanced both by the plants through rhizostabilization and by the iron-adsorbed process within the laterite soil bed. In addition, the arsenic removal was observed to increase along with the time from 30 to 90 days, and it reached to a maximum removal around 90 days, and then decreased after 122 days. Thus, the arsenic removal efficiency including mechanisms founded can then be applied in designing of constructed wetland for arsenic treatment from gold mine drainage with similar site/soil characteristic.

Temporal soil salinity modeling using SaltMod model in the west side of Urmia hyper saline Lake, Iran

Soil salinity is a common problem among lands, which plays harmful effects on groundwater, leading to some problems on land use, use of water, and accordingly on human life. The present study was conducted to simulate soil salinity in the root and transition zones in ten years of simulation period and assume the impact of drain depth and irrigation scenarios on soil salinity and depth to water table. Thus, SaltMod was used with the Geo-Hydrological data collected from Dizaj-e Dowl area located in the northwest of the Urmia Lake. The results indicated that the leaching efficiency of 0.5 in the root zone and natural drain depth of 8.5 and 5.5 m/season were the best match with the observed data. Soil salinity in the root zone had a consistent trend both above and below the drain level rise from 8 dS/m during the first season to 55 dS/m in the second season. Based on the water table, an increase of 7.7 m occurred after 10 years of the simulation period. In addition, the drain depth of 1.2 m assumed in the pilot area appeared to be feasible. Based on the results, SaltMod can be used to predict soil salinity for a long-term analysis by assuming the effect of different scenarios of irrigation and drainage depth on soil salinity in various soil horizons.

Assessing soil nutrient index in mango orchards of Maal area, Lucknow, U.P.

For developing soil nutrient index (SNI), hundred soil samples were collected from root zone depth in hundred mango orchards of villages of Maal region in Lucknow, Uttar Pradesh. Univariate statistics of nutrient data was developed. The SNI in mango orchards of each village was developed and showed that majority of the nutrients were in low to medium ratings. DTPA extractable Zn was low in mango orchards of Thari village while all other orchards had medium ratings. The Cu content showed low while Fe content was medium in orchards of all villages. The Mn content was low in all village mango orchards except Maal village where it showed medium rating. Available K was in medium to high ratings while P was medium in all the orchards. Mango yield in these orchards were <10.0 t ha−1. Yield limiting nutrients indicated need for adoption of good orchard management practices.

Should Upper Limit of Available Water be Based on Field Capacity?

Core Ideas Plants can use water while soil drains. Extra water can move up into the root zone. Field measurements of water use are not restricted by boundary values. Plant‐available water is usually determined from laboratory measurements as the difference between field capacity (undisturbed soil samples) and wilting point (disturbed samples), both of which are determined at arbitrary applied pressures. How much soil water is actually available to plants? The purpose of this report is to demonstrate that data are inconsistent with the concept of field capacity at a pressure head being the upper limit of available water. Existing field studies were re‐examined. Literature shows that a considerable portion of transpired water often comes from below the root zone. A site that had water table depths ranging from near the surface to 3 m deep showed that tensiometer pressure heads in the root zone rarely got as dry as −333 cm pressure head (approximate limit of field capacity). Another study showed that as surface soil dried, the roots were able to take up water from deeper soil, showing the flexibility of the root zone depth. Still other studies suggest that transpiration might start between 3 and 10 h after a rain ends, even while the soil is still draining. Together these studies strongly suggest that roots take up water under conditions wetter than −333 cm pressure head; therefore, laboratory‐determined field capacity should not be considered the upper cutoff of available water.

Carbon and Nitrogen Pools in Deep Soil Horizons at Different Landscape Positions

Core Ideas Total C and total N were greater at shoulder position for alfalfa than in the other two land uses. No observed differences for total C among land uses at backslope and footslope positions. Labile pools of C and N showed differences with land use and topographic positions. In general, labile C and N pools followed alfalfa &gt; black walnut plantation &gt; corn–soybean. Labile and bulk pools of carbon and nitrogen (C and N) play different functional roles in soil organic matter dynamics and nutrient cycling. The objectives of this study were to evaluate the (i) effects of land use [corn (Zea mays L.)–soybean [Glycine max (L.) Merr.], alfalfa (Medicago sativa L.), and black walnut (Juglans nigra L.) plantation] and (ii) vertical distribution of labile [potassium permanganate oxidizable carbon (POXC), water extractable organic carbon (WEOC), water extractable nitrogen (WEN)] and bulk [total carbon (TC), total nitrogen (TN)] pools of C and N in soil to a depth of 105 cm at different topographic positions within a watershed. Alfalfa had 10.02 to 14.86 Mg ha−1 greater TC than corn–soybean and black walnut plantation on the shoulder position in the surface horizon (0–15 cm), whereas the subsurface horizon (15–105 cm) showed no significant differences for TC measured at all topographic positions. Soil POXC was significantly higher in alfalfa than corn–soybean in the surface layer of 0 to 15 cm by 1748.6, 1904.03, and 2878.67 kg ha−1 at the shoulder, backslope, and footslope positions, respectively. However, no differences were observed for POXC at the shoulder position when all subsurface layers were combined at 15‐ to 105‐cm depth. In general, the labile pools of C and N showed differences with land use and topographic positions and followed alfalfa &gt; black walnut plantation &gt; corn–soybean. The study results suggest that for accurate assessment of land use on C and N gains and/or losses both bulk and labile pools should be measured including the entire root zone depth. Topographic differences should be accounted for assessing C and N pools at the watershed scale.

Improving Water Use Efficiency and Water Productivity for Okra Crop by using Subsurface Water Retention Technology

Utilizing the modern technologies in agriculture such as subsurface water retention techniques were developed to improve water storage capacities in the root zone depth. Moreover, this technique was maximizing the reduction in irrigation losses and increasing the water use efficiency. In this paper, a polyethylene membrane was installed within the root zone of okra crop through the spring growing season 2017 inside the greenhouse to improve water use efficiency and water productivity of okra crop. The research work was conducted in the field located in the north of Babylon Governorate in Sadat Al Hindiya Township seventy-eight kilometers from Baghdad city. Three treatments plots were used for the comparison using surface trickle irrigation system: Polyethylene sheet (SWRT) was used in plot T1, controlled irrigation in plot T2 and uncontrolled irrigation in plot T3. Irrigation quantities, time of irrigation, soil water contents were measured for all treatments plots. The results indicated that water use efficiency for the three experimental plots, T1, T2, and T3 were: 2.43, 1.94 and 0.98 kg/m3, respectively. The increasing value in water use efficiency of T1 plot compared with T2 and T3 plots were 25 and 148 %, respectively. Additionally, the water productivity of okra crop for T1, T2, and T3 plots was: 12800.9, 8744.8, and 4736.3 ID/m3, respectively. The increasing value of the water productivity of T1 compared with plots T2 and T3 was 46 and 170 %, respectively. From this study, the benefit of using membrane sheet below the soil surface resulted in an increase in the value of yield, water use efficiency and water productivity. Moreover, saving water and reduced the water losses by deep percolation were resulted. &#x0D;

Mapping rootable depth and root zone plant-available water holding capacity of the soil of sub-Saharan Africa

In rainfed crop production, root zone plant-available water holding capacity (RZ-PAWHC) of the soil has a large influence on crop growth and the yield response to management inputs such as improved seeds and fertilisers. However, data are lacking for this parameter in sub-Saharan Africa (SSA). This study produced the first spatially explicit, coherent and complete maps of the rootable depth and RZ-PAWHC of soil in SSA. We compiled geo-referenced data from 28,000 soil profiles from SSA, which were used as input for digital soil mapping (DSM) techniques to produce soil property maps of SSA. Based on these soil properties, we developed and parameterised (pedotransfer) functions, rules and criteria to evaluate soil water retention at field capacity and wilting point, the soil fine earth fraction from coarse fragments content and, for maize, the soil rootability (relative to threshold values) and rootable depth. Maps of these secondary soil properties were derived using the primary soil property maps as input for the evaluation rules and the results were aggregated over the rootable depth to obtain a map of RZ-PAWHC, with a spatial resolution of 1 km2. The mean RZ-PAWHC for SSA is 74 mm and the associated average root zone depth is 96 cm. Pearson correlation between the two is 0.95. RZ-PAWHC proves most limited by the rootable depth but is also highly sensitive to the definition of field capacity. The total soil volume of SSA potentially rootable by maize is reduced by one third (over 10,500 km3) due to soil conditions restricting root zone depth. Of these, 4800 km3 are due to limited depth of aeration, which is the factor most severely limiting in terms of extent (km2), and 2500 km3 due to sodicity which is most severely limiting in terms of degree (depth in cm). Depth of soil to bedrock reduces the rootable soil volume by 2500 km3, aluminium toxicity by 600 km3, porosity by 120 km3 and alkalinity by 20 km3. The accuracy of the map of rootable depth and thus of RZ-PAWHC could not be validated quantitatively due to absent data on rootability and rootable depth but is limited by the accuracy of the primary soil property maps. The methodological framework is robust and has been operationalised such that the maps can easily be updated as additional data become available.

Temporal Changes of Soil Water in Sandy Soils Amended with Pine Bark and Efficient Blueberry Irrigation

Core Ideas Hydraulic properties of soil mixed with pine bark changed rapidly as bark degraded. Soil ρb increased from 0.33 to 0.62 g cm–3 and θfc increased from 7 to 21% in 2 yr. After 2 yr, no change in θfc indicated a constant capillary size porosity in the bark–soil mixture. Root zone depth in the bark–soil mix decreased continually to reduce plant‐available water. Sensors help monitor soil‐water dynamics that mimic the above changes in bark–soil mixtures. Temporal changes in the physical and hydraulic properties of pine bark as it degrades above sandy soil likely affect soil water (θv) availability and the efficiency of irrigation in blueberry (Vaccinium corymbosum L.) production. The objectives of this study were to (i) assess the physical and hydraulic properties of commercially available pine bark with large, medium, and fine grades as it aged above well‐ and poorly‐drained sandy soils, and (ii) test the capability of dielectric soil moisture sensors to monitor θv reliably through time. During 3 yr, the depth of the pine bark layer decreased from 26 to 15 cm, and the bulk density of the 0‐ to 15‐cm layer of pine bark increased from 0.33 to 0.62 g cm–3. The water content at field capacity (θfc) of pure pine bark was initially 0.07 cm3 cm–3 and increased to 0.21 cm3 cm–3 during the first 2 yr, but changed little afterward. The measured θfc at two sites with 2‐yr‐old pine bark remained between 0.19 and 0.21 cm3 cm–3 and agreed well with sensor estimates. The θfc gradually decreased with depth from 0.25 cm3 cm–3 at 7.5‐cm depth in the pine bark layer to 0.10 cm3 cm–3 at 60‐cm depth. The layer of pine bark mixed with well‐drained sandy soil reached the lowest θv (θl of 0.10 cm3 cm–3) after 12 d of drying, but this decrease in moisture required 40 d in poorly‐drained sandy soil. The root zone of pine bark in well‐drained sandy soil drained to θfc in &lt;2 h compared with 3 h in poorly‐drained sandy soil. These data could be used to optimize irrigation efficiency.

ELECTRICAL TECHNIQUE FOR MONITORING WETTING PATTERN UNDER TRICKLE SOURCE

Knowledge of the wetted pattern dimensions is important in designing and managing efficient drip irrigation systems. Distance between emitters, root zone depth and emitter flow rates must be matched to the soil’s wetting characteristics and the amount and timing of water to be supplied to meet the crop needs. To estimate the wetted pattern dimensions correctly during laboratory experiments in soil section, the wetting front progress should be allowed to move freely into the soil profile in all directions. The developed technique depending on number of electric circuits distributed on steel axes (electrical measurement axes) inside a wooden rectangular soil box was used to determine the wetting front movement. This technique of determining wetted pattern dimension, avoids the side effects of the Plexiglass wall, in conventional technique, on the soil moisture movement. As a result, the obtained wetted pattern agrees closely to that described by Zur (1999) and Ismail et. al (2006).

HYDRUS Simulation of Sustainable Brackish Water Irrigation in a Winter Wheat-Summer Maize Rotation System in the North China Plain

Freshwater resources in the North China Plain (NCP) are near depletion due to the unceasing overexploitation of deep groundwater, by far the most significant source of freshwater in the region. To deal with the deepening freshwater crisis, brackish water (rich but largely unused water in agriculture) is increasingly being used in irrigation in the region. However, inappropriate irrigation with brackish water could lead to soil salinization and cropland degradation. To evaluate such negative impacts, the HYDRUS-1D model was used to simulate soil salt transport and accumulation under 15 years of irrigation with brackish water. The irrigation scenarios included brackish water irrigation during the wintering and jointing stages of winter wheat and then freshwater irrigation just before the sowing of summer maize. Freshwater irrigation was done to leach out soil salts, which is particularly vital in dry years. For the littoral region of the plain, HYDRUS-ID was used to simulate the irrigated cropping system stated above for a total period of 15 years. The results showed that it was feasible to use brackish water twice in one year, provided freshwater irrigation was performed before sowing summer maize. Freshwater irrigation, in conjunction with precipitation, leached out soil salts from the 100 cm root-zone depth. The maximum salt accumulation was in the 160–220 cm soil layer, which ensured that root-zone soil was free of restrictive salinity for crop growth. Precipitation was a critical determinant of the rate and depth leaching of soil salt. Heavy rainfall (&gt;100 mm) caused significant leaching of soluble salts in the 0–200 cm soil profile. Salt concentration under brackish water irrigation had no significant effect on the variations in the trend of soil salt transport in the soil profile. The variations of soil salinity were mainly affected by hydrological year type, for which the buried depth of soil salt was higher in wet years than in dry years. The study suggested that 15 years of irrigation with brackish water is a reliable and feasible mode of crop production in coastal regions with a thick soil column above the water table. The scheme proposed in this study allowed the use of brackish water in irrigation without undue salinization of the crop soil layer, an intuitive way of resolving the deepening water crisis in the NCP study area and beyond.

English

Predicting grain yields of maize in soil amended with organic wastes using modified productivity index was studied for three cropping seasons. Soil samples for determination of productivity index and individual productivity indicators for prediction of grain yields of maize were collected from 0 15, 15-30, 30-45, and 45-60 cm depths. Ascribed sufficiency value was assigned to each productivity indicator of bulk density, available water capacity (AWC) pH and depth of rooting zone (DRZ) which were used to calculate productivity index (PI) for each amendment. Highest predictions of grain yields of maize were obtained for sawdust PI=0.39 and grain yield of maize-2.30 t ha-1 in 2013 and burnt rice mill waste PI=0.39 and grain yield of maize=2.30 t ha-1 and PI=0.37 and grain yield of maize=2.25 t ha-1 in 2014 and 2015 cropping seasons, respectively. The prediction of organic wastes for grain yields of maize is as follows BRMW>SD>URMW>C. Calculated productivity index (CPI) predicted highly significant (r=0.92 and r2=0.84) grain yields of maize. Bulk density more than AWC and pH predicted highly significant (r=0.95 and r2 = 0.89) grain yield of maize. Key words: Amended, grain yields of maize, organic wastes, predicting, productivity index.

Observed Soil Moisture–Precipitation Feedback in Illinois: A Systematic Analysis over Different Scales

Abstract The lack of understanding on the soil moisture–precipitation feedback mechanisms remains a large source of uncertainty for land–atmosphere coupled models. Previous observation-based studies on the soil moisture–precipitation feedback in Illinois have shown contradictory results. This paper extends earlier research by providing a more holistic analysis considering different scales based on an 11-yr (2003–13) hourly soil moisture dataset, which makes it possible to revisit the disputed hypothesis on the correlation between warm-season soil moisture and subsequent precipitation. This study finds a strong positive correlation between late spring/early summer state-average soil moisture at the root-zone depths and subsequent state-average summer precipitation. On the daily to weekly time scale, however, no relation is found. Moreover, regional analysis suggests that precipitation variability over central Illinois can be best explained by the soil moisture variability in northwest Illinois. Using a back-trajectory method [Water Accounting Model-2 layers (WAM-2layers)] from May to July, the evaporative sources of precipitation in Illinois are identified. The pattern of the source regions shows little interannual variability, while the strength of the sources changes significantly and the Gulf of Mexico contributes more during wet years. However, strong influences (teleconnections) of sea surface temperatures on the subsequent precipitation variability in Illinois are not found on a seasonal scale. The long time scale of the soil moisture–precipitation correlation and the weak influences of SSTs and climate indices may suggest that precipitation variability in spring/summer in Illinois is mostly related to continental-scale soil moisture–precipitation feedback.

Simplified continuous simulation model for investigating effects of controlled drainage on long-term soil moisture dynamics with a shallow groundwater table.

Accurate modeling of soil water content is required for a reasonable prediction of crop yield and of agrochemical leaching in the field. However, complex mathematical models faced the difficult-to-calibrate parameters and the distinct knowledge between the developers and users. In this study, a deterministic model is presented and is used to investigate the effects of controlled drainage on soil moisture dynamics in a shallow groundwater area. This simplified one-dimensional model is formulated to simulate soil moisture in the field on a daily basis and takes into account only the vertical hydrological processes. A linear assumption is proposed and is used to calculate the capillary rise from the groundwater. The pipe drainage volume is calculated by using a steady-state approximation method and the leakage rate is calculated as a function of soil moisture. The model is successfully calibrated by using field experiment data from four different pipe drainage treatments with several field observations. The model was validated by comparing the simulations with observed soil water content during the experimental seasons. The comparison results demonstrated the robustness and effectiveness of the model in the prediction of average soil moisture values. The input data required to run the model are widely available and can be measured easily in the field. It is observed that controlled drainage results in lower groundwater contribution to the root zone and lower depth of percolation to the groundwater, thus helping in the maintenance of a low level of soil salinity in the root zone.