Sweet Sorghum Planting Effects on Stalk Yield and Sugar Quality in Semi-Arid Tropical Environment

Sweet sorghum [Sorghum bicolor (L.) Moench] has potential as a bioenergy crop for producing food, fiber, and fermentable sugar. Unlike dryland grain sorghum, little information is available on the influence of staggered planting and genotypes, especially in semiarid tropical environments. The objectives of the present study were (i) to quantify the effects of planting time and genotype on stalk and biomass yields, juice sugar quality, and (ii) to identify the most productive genotypes and planting windows for sustainable feedstock supply. Four commercial sweet sorghum genotypes (SSV84, SSV74, CSV19SS, and CSH22SS) were planted on five planting dates (1 June, 16 June, 1 July, 16 July, and 1 August) during the rainy (June–October) season of 2008 and 2009 in Hyderabad (17°27´ N, 78°28´ E), India. Planting in early and mid-June produced significantly (P ≤ 0.05) higher fresh stalk yield and grain yield than later planting dates. Commercial hybrid CSH22SS produced significantly more stalk, grain, sugar, and ethanol yield over genotypes SSV84 or SSV74. Based on the stalk yield, juice sugar quality, sugar, and ethanol yields, the optimum planting dates for sweet sorghum in semiarid tropical climate is early June to early July. Planting sweet sorghum during this time allows more feedstock to be harvested and hence extends the period for sugar mill operation by about 1 mo, that is, from the first to the last week of October

Water scarcity management: Part 2: Satellite-based composite drought analysis

The composite use of two drought indices, namely the Reconnaissance Drought Index (RDI) for meteorological drought and the Vegetation Health Index (VHI) for agricultural drought, is considered for drought quantification and monitoring leading to water scarcity. The results of 20-year monthly RDI for Thessaly, Greece, indicate that there are eight drought periods lasting 12 months each and the start of severe and extreme drought usually coincides with the beginning of the hydrological year, whereas for moderate droughts the start occurs in spring, both lasting until the end of the hydrological year. There is also an increase in the areal extent of drought with the maximum occurring in the summer. Similarly, the results of VHI indicate that drought occurs every year during the warm season with increasing severity and areal extent. The findings justify the composite use of drought indices of different drought types for drought assessment and monitoring. Copyright © 2018 Inderscience Enterprises Ltd

The role of spatial and spectral resolution on the effectiveness of satellite-based vegetation indices

Remote Sensing applications are designed to provide farmers with timely crop monitoring and production information. Such information can be used to identify crop needs or health problems and provide solutions for a better crop management. Vegetation indices (VIs) derived from satellite data have been widely used to assess variations in the physiological state and biophysical properties of vegetation. In the present study, the experimental area is located near the village Eleftherion of Larissa Prefecture in the Thessaly Plain, and consisted of two adjacent agricultural fields of cotton and corn. Imagery from WorldView-2 (WV2) satellite platform was obtained from European Space Imaging and Landsat-8 (L8) free of charge data were downloaded from the United States Geological Survey (USGS) archive. The images were selected for a four month span to evaluate continuity with respect to vegetation growth variation. VIs for each satellite platform data such as the Normalized Difference Vegetation Index (NDVI), the Soil-Adjusted Vegetation Index (SAVI) and the Fraction Photosynthetically Radiation (FPAR) were calculated. The comparison of these VIs produced from the two satellite systems with different spatial and spectral resolution was made for each growth stage of the crops and their results were analyzed in order to examine their correlation. Utilizing the WV2 new spectral data, several innovative chlorophyll and vegetation indices were created and evaluated so as to reveal their effectiveness in the detection of problematic plant growth areas. The Green Chlorophyll index appeared to be the most efficient index for the delineation of these areas. © 2016 SPIE

Remote sensing in water balance modelling for evapotranspiration at a rural watershed in Central Greece

There is an increasing trend in water balance modelling for remote sensing tools, which provide distributed information of watershed features. The paper's objective consists of exploring the remote sensing potential for evapotranspiration estimation in water balance modelling of a small rural watershed with limited data, namely Portaikos rural mountainous watershed of 132 km2 in Central Greece. Three water balance models with small number of parameters are used, namely Abulohom's, GR2M and Xiong-Guo model, respectively. Two approaches are considered. At first, monthly potential evapotranspiration derived from conventional meteorological data is used as input to the models. Second, air temperature is derived from land surface temperature (LST) of NOAA/AVHRR satellite images for monthly evapotranspiration estimation. Time series of the above parameters for 13 years (1981-1993) are used. The remote sensing potential for evapotranspiration estimation is assessed by comparing the observed and simulated monthly runoff at the output of Portaikos watershed. Four error statistics are used for validation. The results are considered quite satisfactory for the four error statistics. The GR2M shows relatively better performance than the other models for all the error statistics, as well as for the satellite-based approach, which shows slightly better performance than the conventional approach. © 2018 Inderscience Enterprises Ltd

Comparing soil moisture under trickle irrigation modeled as a point and line source

The validity of the assumption that an irrigation event from point sources can be approximated as an infinite line source is investigated in this article. This is accomplished by comparing soil water dynamics under line and point sources. Two existing mathematical models which simulate point and line drip irrigation were used. The models consider root water uptake, evaporation of soil water from the soil surface and incorporate hysteresis in the soil water characteristic curve. The comparison was made for two soil types (loamy sand and silt). The results showed that the treatment of a point source as a line source underestimates the water content values for both the soil types. This difference decreases when the depth of comparison increases. For soil depths greater than 30cm and for time greater than irrigation duration the two models gave very close results. For the same emitter spacing and for the horizontal direction perpendicular to the drip line on the emitter spot, when the distance from the point and the line sources increases the difference of water content values increases. On the contrary, in the direction parallel to the drip line when the distance from the emitter increases (the distance from the line source remains the same) the difference of water content decreases. Lastly, differences are greater in the case of coarse grained soil than in fine grained soil.Cylindrical flow model Plane flow model Discharge rate Emitter spacing Line spacing

Remotely Sensed Methodologies for Crop Water Availability and Requirements in Precision Farming of Vulnerable Agriculture

Agriculture is mainly impacted by water availability. Differences in climate conditions and the appearance of severe events, like droughts, has a significant imprint on local, regional and global agricultural productivity. The goal of this paper is to present remotely sensed approaches for water availability and requirements in vulnerable agriculture. Earth Observation (EO) data contribute to precision agriculture for efficient crop monitoring and irrigation management. A drought susceptible region considered as vulnerable farming was chosen, in the Thessaly prefecture in Central Greece. Water availability is measured by means of precipitation frequency examination and drought estimation. Crop water requirements are measured by assessing crop evapotranspiration (ET) with the synergistic use of WV-2 satellite images and ground-truth data. The remote-based ETcsat is assessed by utilizing the reference ETo derived from Food and Agriculture Organization (FAO) methodology, while the meteorological data and Kc are evolved from Normalized Difference Vegetation Index (NDVI). According to the rainfall frequency studies, indicators demonstrate a significant precipitation decrease. The results reveal the importance of water availability estimation for facing agriculture water needs and the necessity for monitoring of drought conditions in a vulnerable Mediterranean area in order to plan an integrated strategy for climate adaptation. Moreover, the conclusions clarify the usefulness of collaborating innovative very high spatial and sperctral resolution EO images along with ground-truth data for crop ET monitoring and also the assimilation into the precision agriculture methodology which is valuable for optimal agricultural production. © 2019, Springer Nature B.V

Water Quality Focusing on the Hellenic World: From Ancient to Modern Times and the Future

Water quality is a fundamental issue for the survival of a city, especially on dry land. In ancient times, water availability determined the location and size of villages and cities. Water supply and treatment methods were developed and perfected along with the evolution of urbanization. In Europe, after the fall of the Roman Empire, water supply and sewage systems went through fundamental changes. However, in medieval times, the lack of proper sanitation and low water quality increased the spreading and effects of epidemics. The importance of potable water quality was established during modern times. In Greece, the significance of water filtration and disinfection was not understood until the beginning of the 20th century. Moreover, the beneficial effects of water quality and sanitation on human health and especially on life expectancy are considered. In Greece and other countries, a dramatic increase in life expectancy mainly after the 2nd World War is probably due to the improvement of potable water quality and hygiene conditions. However, since the mid-20th century, new water quality issues have emerged, such as eutrophication, the improvement of water treatment technologies, as well as chemical and microbiological water pollution problems. This study, in addition to the historical evolution of water quality, highlights and discusses the current issues and challenges with regard to the management and protection of water quality, including global changes in population and urbanization, lack of infrastructure, use of nonconventional water resources, spreading of emerging pollutants and contaminants (e.g., antibiotics and microplastics), and climatic variability impacts. Against these, a review of the main proposed strategies and measures is presented and discussed to protect water quality and maintain water supplies for the future. Understanding the practices and solutions of the past provides a lens with which to view the present and future

Evaluation and cross-comparison of vegetation indices for crop monitoring from sentinel-2 and worldview-2 images

Farmers throughout the world are constantly searching for ways to maximize their returns. Remote Sensing applications are designed to provide farmers with timely crop monitoring and production information. Such information can be used to identify crop vigor problems. Vegetation indices (VIs) derived from satellite data have been widely used to assess variations in the physiological state and biophysical properties of vegetation. However, due to the various sensor characteristics, there are differences among VIs derived from multiple sensors for the same target. Therefore, multi-sensor VI capability and effectiveness are critical but complicated issues in the application of multi-sensor vegetation observations. Various factors such as the atmospheric conditions during acquisition, sensor and geometric characteristics, such as viewing angle, field of view, and sun elevation influence direct comparability of vegetation indicators among different sensors. In the present study, two experimental areas were used which are located near the villages Nea Lefki and Melia of Larissa Prefecture in Thessaly Plain area, containing a wheat and a cotton crop, respectively. Two satellite systems with different spatial resolution, WorldView-2 (W2) and Sentinel-2 (S2) with 2 and 10 meters pixel size, were used. Normalized Difference Vegetation Index (NDVI) and Leaf Area Index (LAI) were calculated and a statistical comparison of the VIs was made to designate their correlation and dependency. Finally, several other innovative indices were calculated and compared to evaluate their effectiveness in the detection of problematic plant growth areas. © 2017 SPIE

History of floods in Greece: causes and measures for protection

Floods as diachronic and international phenomena affect numerous people, buildings and infrastructure. Throughout human history, floods are the most lethal and have caused more economic losses than other natural disasters. In this review, the history of floods is considered focusing in ancient Greece since the early Bronze Age. Ancient Greeks avoided living near lakes and rivers probably for hygiene reasons and protection from floods. Representative impressive hydraulic anti-flooding works including dams, walls, channels from different cities and other settlements in the Minoan era, and the Archaic, Classical, Hellenistic and Roman period are presented. It is concluded that the risk with respect to flood events is more severe today than in ancient times. The ongoing urbanization and deforestation through the centuries have led to an increasing and unmanageable flood risk. For this reason, a set of special measures should be applied in vulnerable areas aiming to mitigate severe damages that floods might cause, including anti-flooding dams, water flow diverting technologies, rainwater harvesting and rain gardens for stormwater retention, reforestation and other smart environmental strategies. The examples of anti-flood hydro-technologies described in this paper may have some relevance for water engineering even in modern times. © 2020, Springer Nature B.V

Investigation of the direct runoff generation mechanism for the analysis of the SCS-CN method applicability to a partial area experimental watershed

The Soil Conservation Service Curve Number (SCS-CN) method is widely used for predicting direct runoff volume for a given rainfall event. The applicability of the SCS-CN method and the direct runoff generation mechanism were thoroughly analysed in a Mediterranean experimental watershed in Greece. The region is characterized by a Mediterranean semi-arid climate. A detailed land cover and soil survey using remote sensing and GIS techniques, showed that the watershed is dominated by coarse soils with high hydraulic conductivities, whereas a smaller part is covered with medium textured soils and impervious surfaces. The analysis indicated that the SCS-CN method fails to predict runoff for the storm events studied, and that there is a strong correlation between the CN values obtained from measured runoff and the rainfall depth. The hypothesis that this correlation could be attributed to the existence of an impermeable part in a very permeable watershed was examined in depth, by developing a numerical simulation water flow model for predicting surface runoff generated from each of the three soil types of the watershed. Numerical runs were performed using the HYDRUS-1D code. The results support the validity of this hypothesis for most of the events examined where the linear runoff formula provides better results than the SCS-CN method. The runoff coefficient of this formula can be taken equal to the percentage of the impervious area. However, the linear formula should be applied with caution in case of extreme events with very high rainfall intensities. In this case, the medium textured soils may significantly contribute to the total runoff and the linear formula may significantly underestimate the runoff produced