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Stamatiadis S.,Soil Ecology and Biotechnology Laboratory | Tsadilas C.,Greek National Agricultural Research Foundation | Schepers J.S.,University of Nebraska - Lincoln
Plant and Soil | Year: 2010

The capacity of a ground-based canopy sensor to detect stress-related parameters of cotton (Grossypium hirsutum) was investigated in a split-plot field experiment for two consecutive growing seasons in central Greece. Three levels of irrigation (22, 31 and 40 cm water) were the whole-plot factor and three rates of fertilizer (60, 110 or 160 kg N ha-1) were the split-plot factor with three replications. Irrigation level was the major factor that explained variations in leaf isotopic composition (δ15N and δ13C) within growing seasons and cotton yield at harvest. The rate of fertilizer application did not have a significant effect on cotton yield because there was sufficient residual soil N to meet crop needs. Canopy NDVI was highly correlated to yield when cotton response to differential irrigation was detected. The obtained correlations between canopy reflectance and stress-related parameters (leaf N, δ15N and δ13C) and the stability of the relationship between NDVI and yield over two consecutive seasons indicated that ground-based remote sensing can be used to assess the level of water stress that occurred during the growing season. The application of this technology for in-field monitoring of water stress may prove valuable in semiarid regions where water is often the most limiting factor in crop production. © 2009 Springer Science+Business Media B.V. Source


Stamatiadis S.,Soil Ecology and Biotechnology Laboratory | Tsadilas C.,Greek National Agricultural Research Foundation | Samaras V.,Greek National Agricultural Research Foundation | Schepers J.S.,University of Nebraska - Lincoln | Eskridge K.,University of Nebraska - Lincoln
European Journal of Agronomy | Year: 2016

Efficient N management is essential to optimize yields and reduce degradation of the environment, but requires knowledge of deficit irrigation effects on crop yields and crop N outputs. This study assessed the N content and N-use efficiency of cotton over the 2008 and 2009 growing seasons in a single field site of the Thessaly Plain (central Greece). The experiment consisted of nine treatments with three fertilizer rates (60, 110 and 160 kg N ha-1) split into three irrigation levels (approx. 1.0, 0.7 and 0.4 of the amount applied by the producer). Reduced water supply induced a shift in the distribution of N within the plant with seeds becoming an N sink under conditions of water stress. Total crop N increased linearly with irrigation level and reached a maximum average of 261 and 192 kg N ha-1 in 2008 and 2009, respectively. Fertilizer application did not trigger a crop N or yield response and indicated that N inputs were in excess of crop needs. Variation in weather patterns appeared to explain annual differences of nitrate-N in the top soil and N uptake by the crop. The index of lint production efficiency (iNUE) detected crop responses caused by irrigation and annual effects, but failed to account for excessive N inputs due to mineral fertilizer applications. A maximum average iNUE of 9.6 was obtained under deficit irrigation, whereas an iNUE of 8.1 was obtained under 40 cm irrigation when crop N uptake was not excessive (192 kg ha-1 in 2009). In contrast, NUE, as an estimator of N recovery efficiency, identified excessive fertilizer inputs as N losses to the environment and indicated that 60 kg N ha-1 was a rate of high N removal efficiency and long-term N balance. However, NUE failed to account for crop N responses to irrigation and weather/management patterns. In this case study, neither index was able to detect all the factors influencing the N mass balance and both were required in order to provide a comprehensive evaluation of the environmental performance of our cropping system. © 2015 Elsevier B.V. Source


Stamatiadis S.,Soil Ecology and Biotechnology Laboratory | Evangelou L.,Greek National Agricultural Research Foundation | Yvin J.-C.,TIMAC AGRO INTERNATIONALCRIAS | Tsadilas C.,Greek National Agricultural Research Foundation | And 2 more authors.
Journal of Applied Phycology | Year: 2014

A greenhouse experiment was conducted to evaluate the effects of foliar application of an Ascophyllum nodosum seaweed extract (AZAL5) on the growth, nutrient uptake, and yield of winter wheat in a surface soil of the Thessaly Plain classified as TypicXerorthent. Twelve treatment combinations in a randomized complete block design with a factorial arrangement were composed of two rates of inorganic fertilizer (0 and 50 ppm N), three rates of AZAL5 (0, 1.5, and 3 % diluted extract), and two levels of water supply (75 and 45 % of field capacity). Under soil P and K sufficiency, the addition of fertilizer N greatly increased grain yield and nutrient uptake in the shoots (N and K) and grain (N, P, and K). Reduced water supply decreased grain yield and caused water stress as evidenced by decreased Δ13C in the N-deficient treatments and decreased nutrient uptake. AZAL5 application caused increased grain K uptake and a 25 % increase in yield only when mineral N was added. Differences in the efficacy of the two AZAL5 concentrations indicated that optimal dilution ratios were directly or indirectly dependent on soil water content. Complex interaction effects between AZAL5 and water supply on grain Δ13C could not be explained by conventional physiological response to water stress. The lack of biomass, nutrient content, and Δ13C differences between AZAL5 and control treatments in the shoot indicated that the reproductive organs of wheat were the main site of biostimulant action. Overall, the results underline the potential of this product to enhance the effectiveness of inorganic N fertilizers in intensively managed cropping systems under optimal irrigation, deficit irrigation, or rainfed conditions. © 2014, Springer Science+Business Media Dordrecht. Source


Stamatiadis S.,Soil Ecology and Biotechnology Laboratory | Evangelou L.,Greek National Agricultural Research Foundation | Blanta A.,University of Thessaly | Tsadilas C.,Greek National Agricultural Research Foundation | And 7 more authors.
Communications in Soil Science and Plant Analysis | Year: 2013

Surface visible-near infrared (NIR) reflectance of bare soil by remote sensing devices has been used to infer topsoil properties such as organic matter, soil texture, water content, salinity, and crop residue cover. Spectral mapping of soil properties can be ultimately used as a tool for the implementation of site-specific management practices at the field scale or for soil-landscape modeling at a regional scale. The accuracy of prediction of soil properties with satellite imagery is affected by conditions and properties of the soil surface, by radiometric and atmospheric effects, and by spatial and spectral resolutions. In this study, a high-resolution World View 2 image was used to map soil reflectance in three 10-ha fields of differing soil types and textures that were located in different sections of the east Thessaly Plain. Radiance data from four visible-NIR channels were extracted from the same coordinates that soil samples were taken at two soil depths within each field. Point radiance values were correlated to soil organic matter, total carbon (C) and nitrogen (N) contents, their isotopic composition, carbonate content, nitrate content, pH, electrical conductivity, and soil texture that were analyzed in the laboratory. Strong correlation coefficients emerged between green/NIR image reflectance and total soil N, organic matter, and carbonate content across the three fields in both soil depths. The greatest negative correlation coefficient (R2 = 0.77) was obtained between satellite NIR reflectance and soil N content. More data are needed to verify these relationships, but the results indicated the potential of high-resolution satellite imagery to quantify within-field and regional-scale variability of soil N and C in the Thessaly Plain. © 2013 Copyright Taylor & Francis Group, LLC. Source

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