Papers by Theofanis Gemtos
Precision Agriculture, 2010
In the present study, the spatial variability of some soil physical and chemical properties in a ... more In the present study, the spatial variability of some soil physical and chemical properties in a 0.8 ha apple orchard were studied. Sixty soil samples were taken from two sampling depths: 0-0.3 m and 0.3-0.6 m. The soil samples were analyzed for the following soil properties: soil texture, pH, cation exchange capacity and NO 3-N, NH
AGROFOR, 2021
Nutrition of intensive sheep farming in Greece is based mainly on feeding forages and concentrate... more Nutrition of intensive sheep farming in Greece is based mainly on feeding forages and concentrates in the stable, while grazing is provided in a low extend. Feeding cost is the major cost factor and from the protein supplementation side is based on alfalfa hay and soybean meal. The aim of the study was to investigate the substitution of soybean meal with local produced legumes forages. Thirty ewes of the “Karagouniko” breed were split in three groups of ten animals each. In the first group (control group), nutrition was based on alfalfa hay and soybean meal. In the second group, alfalfa hay and soybean meal were entirely substituted with vetch hay. In the third group, alfalfa hay was completely substituted with peas hay and the soybean meal inclusion was increased. Body weight was measured in the beginning and at the end of the trial period. Feed consumption and milk production were recorded daily and milk quality was analyzed weekly. No significant differences were found for all th...
Energy Procedia, 2017
The area of wetlands after peat mining in Belarus is about 190,000 hectares and once peat harvest... more The area of wetlands after peat mining in Belarus is about 190,000 hectares and once peat harvesting has ceased it is impossible to grow any cultural plants for some years. One of the perspective directions is rewetting wetlands after peat extraction that stimulate vegetation of natural grass, like reed, rush and others which are growing in natural conditions. The grass biomass may be used for energy purpose, in particular for composite briquettes fabrication, which contents in 50 % from grass and 50 % from peat. The LCA method based on the standards series ISO 14040 was used for evaluation of environmental impact of growing and production of composite briquettes from wetland biomass. The goal of LCA was comparison two scenarios of biomass production for composite briquettes. Product system B (PSB) based on biomass harvesting with simultaneous shredding and product system A (PSA) based on biomass mowing, raking for drying and bailing. The basic LCA impact categories were: climate change, acidification, photo oxidant formation, eco toxicity and human toxicity. The product system A (mowing and baling biomass) achieved better results in 3 categories out of 5, and especially eco toxicity and human toxicity. And if for climate change the indicator results for both systems were close, for acidification, eco toxicity and human toxicity PSB systems impact was significantly higher to compare to PSA. It may be explained by peat using for biomass drying in product system B. The contents of SO2 and Hg in the peat in several times higher to compare to diesel and gas, while PCB and GCB are contained only in the peat.
European Journal of Agronomy, 2000
Eleven sugar beet genotypes were tested for their performance under different soil compaction lev... more Eleven sugar beet genotypes were tested for their performance under different soil compaction levels. The genotypes used were three inbreds, three commercial varieties widely cropped in Greece, four experimental hybrid varieties and two multigerm OP lines. The experiment was conducted in pots in glasshouse. Pots were filled with soil and after placing the seed at a depth of 3 cm, the compaction pressure was applied. Two soil types, two initial soil water contents and seven pressure levels ranging from a minimum pressure up to 400 kPa were the factors studied in a randomised complete block experiment with four replications. Results showed that sugar beet is sensitive to compaction although low compaction pressures (less than 200 kPa) seemed to be beneficial. From the genotypes tested inbreds were more sensitive to pressure effects than hybrids. Differences among hybrid varieties were observed indicating that response to soil compaction effect could be genotypically affected. This was further confirmed by the different response between the multigerm open polinated varieties
Biomass and Bioenergy, 1999
The possibility of collecting cotton stalks in Greece and using them for energy production was in... more The possibility of collecting cotton stalks in Greece and using them for energy production was investigated. The production and properties of cotton stalks were studied and a system for collection of the aerial part is proposed as a feasible solution to avoid wet conditions under the local climate. A successful method for collection and packaging of the residue was applied, using conventional but highly advantageous equipment, oering reduced investment cost and use of existing machinery. The energy required to harvest cotton stalks was measured by an instrumented tractor. The tractor was able to measure the developed forces between tractor and implement, the power absorbed through the PTO, as well as tractor velocity and fuel consumption. The energy consumed for the operation was calculated and when compared to the energy of the biomass collected gave a positive balance. The work proved the feasibility of harvesting cotton stalks using conventional machinery giving the possibility to collect energy material with a total energy content of 500,000 tons of oil equivalent at national level.
Agricultural Engineering International: …, 2002
In Greece there is a need for reducing sugar beet production costs and adopting methods enhancing... more In Greece there is a need for reducing sugar beet production costs and adopting methods enhancing sustainable agriculture. Minimizing tillage operations by adopting conservation tillage can provide significant energy and cost production savings. Additionally, reduced or no-tillage can offer the opportunity to the farmers to conform to the good management practices imposed by the EU. A three year conservation tillage experiment was carried out in Central Greece in order to evaluate the profits. Tested methods were: reduced tillage with a heavy cultivator (HC), rotary cultivator (RC), disk harrow (DH) and no-tillage (NT) compared with a conventional tillage method (CT) using plough. Reduced tillage methods caused an increase of weeds, of the soil dry bulk density, penetration resistance and shear strength. Soil retained a greater amount of water in the seedbed layer. As a result, crop emergence was facilitated in dry years.
Agriculture
Politicians and the general public are concerned about climate change, water scarcity, and the co... more Politicians and the general public are concerned about climate change, water scarcity, and the constant reduction in agricultural land. Water reserves are scarce in many regions in the world, negatively affecting agricultural productivity, which makes it a necessity to introduce sustainable water resource management. Nowadays, there is a number of commercial IoT systems for irrigation scheduling, helping farmers to manage and save water. However, these systems focus on using the available fresh water sources, without being able to manage alternative water sources. In this study, an Arduino-based low-cost IoT system for automated irrigation scheduling is developed and implemented, which can provide measurements of water parameters with high precision using low-cost sensors. The system used weather station data combined with the FAO56 model for computing the water requirements for various crops, and it was capable of handling and monitoring different water streams by supervising their...
Κεφάλαιο 1. Εισαγωγή Σύνοψη Το κεφάλαιο αυτό είναι μια εισαγωγή στα μηχανήματα καλλιεργητικών φρο... more Κεφάλαιο 1. Εισαγωγή Σύνοψη Το κεφάλαιο αυτό είναι μια εισαγωγή στα μηχανήματα καλλιεργητικών φροντίδων. Γίνεται μια γενική περιγραφή των κατηγοριών των μηχανημάτων που περιγράφονται. Στη συνέχεια αναλύονται κάποια γενικά προβλήματα που αντιμετωπίζονται κατά τη χρήση των μηχανημάτων. Ένα από αυτά είναι η συμπίεση του εδάφους, καθώς τα μηχανήματα χρησιμοποιούνται κυρίως σε ήδη εγκατεστημένες εκτάσεις. Αναλύεται το πρόβλημα και τα μέσα περιορισμού του. Δεδομένου ότι πολλά από τα μηχανήματα αυτά έχουν μεγάλο πλάτος εργασίας, η πλοήγησή τους στο χωράφι με ακρίβεια αποτελεί ένα πρόβλημα. Γι' αυτό αναφέρονται στοιχεία για τα συστήματα υποβοήθησης πλοήγησης που στηρίζονται στη χρήση νέα τεχνολογίας GPS καθώς και για την αναπτυσσόμενη τεχνολογία ελεγχόμενης κυκλοφορίας των μηχανημάτων στο χωράφι. Προαπαιτούμενη γνώση Ο αναγνώστης καλά είναι να γνωρίζει θέματα, όπως ο γεωργικός ελκυστήρας και η χρήση του, τα μηχανήματα κατεργασίας του εδάφους και σποράς, καθώς και να έχει γενικές γνώσεις για τη λειτουργία των δορυφορικών συστημάτων εντοπισμού θέσης στη Γη. 1.2. Προβλήματα χρήσης του γεωργικού εξοπλισμού Τα μηχανήματα των καλλιεργητικών φροντίδων από τη φύση τους κινούνται στους αγρούς μετά την κατεργασία του εδάφους και, τις περισσότερες φορές, σε εγκατεστημένες φυτείες. Επομένως, βρίσκουν συνήθως το έδαφος χαλαρό από την κατεργασία του εδάφους. Το χαλαρό έδαφος είναι εύκολο να συμπιεστεί
All in-text references underlined in blue are linked to publications on ResearchGate, letting you... more All in-text references underlined in blue are linked to publications on ResearchGate, letting you access and read them immediately.
Γeωργική Μηχανολογία [ΠΑΝEΠΙΣΤΗΜΙΟ ΘEΣΣΑΛΙΑΣ, ΣΧΟΛΗ ΓEΩΠΟΝΙΚΩΝ EΠΙΣΤΗΜΩΝ, ΤΜΗΜΑ ΓEΩΠΟΝΙΑΣ ΦΥΤΙΚΗΣ... more Γeωργική Μηχανολογία [ΠΑΝEΠΙΣΤΗΜΙΟ ΘEΣΣΑΛΙΑΣ, ΣΧΟΛΗ ΓEΩΠΟΝΙΚΩΝ EΠΙΣΤΗΜΩΝ, ΤΜΗΜΑ ΓEΩΠΟΝΙΑΣ ΦΥΤΙΚΗΣ ΠΑΡΑΓΩΓΗΣ ΚΑΙ ΑΓΡΟΤΙΚΟΥ ΠEΡΙΒΑΛΛΟΝΤΟΣ]
Γeωργική Μηχανολογία [ΠΑΝEΠΙΣΤΗΜΙΟ ΘEΣΣΑΛΙΑΣ, ΣΧΟΛΗ ΓEΩΠΟΝΙΚΩΝ EΠΙΣΤΗΜΩΝ, ΤΜΗΜΑ ΓEΩΠΟΝΙΑΣ ΦΥΤΙΚΗΣ... more Γeωργική Μηχανολογία [ΠΑΝEΠΙΣΤΗΜΙΟ ΘEΣΣΑΛΙΑΣ, ΣΧΟΛΗ ΓEΩΠΟΝΙΚΩΝ EΠΙΣΤΗΜΩΝ, ΤΜΗΜΑ ΓEΩΠΟΝΙΑΣ ΦΥΤΙΚΗΣ ΠΑΡΑΓΩΓΗΣ ΚΑΙ ΑΓΡΟΤΙΚΟΥ ΠEΡΙΒΑΛΛΟΝΤΟΣ]
In this paper, remote sensing measurements like apparent electrical conductivity (ECa.) are used ... more In this paper, remote sensing measurements like apparent electrical conductivity (ECa.) are used to assess soil compaction. In an experiment comparing five tillage treatments and their effect to energy crops soil penetration resistance (SPR) was measured at the same time as ECa. ECa measurements were carried out using EM-38with dipoles at 1m apart and SPR by an electronic penetrometer. The negative correlation between the two parameters for all measurements resulted in R2= 0.73. Taking the measurements for each treatment in conventional tillage plots R2 = 0.53, chisel plough tillage 0.61, rotary tiller 0.69, disk harrow 0.55, strip-till 0.35 and no till 0.81.
Crop fertilization is an important part of cost and energy inputs in agriculture. The opportunity... more Crop fertilization is an important part of cost and energy inputs in agriculture. The opportunity to apply the variable rate of nitrogen fertilizers according to the plant needs in each part of the field is a promising practice to increase the fertilizer use efficiency. An experiment was conducted in 2016 in the University of Thessaly farm, Central Greece in order to evaluate the use of lidar and optical sensors to monitor the crop canopy for sunflower and maize. The canopy development can serve as a good indicator for the nutrition state of the crops regarding especially the nitrogen, and it can be used as an indicator for variable rate application systems. In order to obtain plants with different canopy development, a field experiment was established with treatments receiving the normal, farmer’s practice, nitrogen rates (100%N) at basic fertilization, treatments receiving 50% reduced nitrogen fertilizer (50%N) and treatments with no nitrogen application (0%N). During growing, the...
Pears require a substantial number of inputs for satisfactory yield and quality. High inputs incr... more Pears require a substantial number of inputs for satisfactory yield and quality. High inputs increase costs, reducecompetitiveness and induce environmental problems. In thecurrent study the environmental profile of a pear orchard, located in central Greece, was developed under different agricultural practices. More specifically, the environmental impacts of using different nitrogen (N) fertilizer application techniques (uniform and variable rate application, VRA) were revealed and compared. UsingN VRA, less N was used, offering cost reduction to the farmer. A Life Cycle Assessment was performed, following the ISO standards. The results showed that 55 % of the total emissions to air in the Particulate matter impact categorywere due to nitrogen oxide and ammoniaderived from fertilizer use. Moreover, carbon dioxide fossil and dinitrogen monoxide emissions to air coming also from fertilizer production and application were significant contributors to Climate Change exceeding the amount o...
Eιδικά Θέματα Γeωργικής Μηχανολογίας [ΠΑΝEΠΙΣΤΗΜΙΟ ΘEΣΣΑΛΙΑΣ, ΣΧΟΛΗ ΓEΩΠΟΝΙΚΩΝ EΠΙΣΤΗΜΩΝ, ΤΜΗΜΑ Γ... more Eιδικά Θέματα Γeωργικής Μηχανολογίας [ΠΑΝEΠΙΣΤΗΜΙΟ ΘEΣΣΑΛΙΑΣ, ΣΧΟΛΗ ΓEΩΠΟΝΙΚΩΝ EΠΙΣΤΗΜΩΝ, ΤΜΗΜΑ ΓEΩΠΟΝΙΑΣ ΦΥΤΙΚΗΣ ΠΑΡΑΓΩΓΗΣ ΚΑΙ ΑΓΡΟΤΙΚΟΥ ΠEΡΙΒΑΛΛΟΝΤΟΣ]
Eιδικά Θέματα Γeωργικής Μηχανολογίας [ΠΑΝEΠΙΣΤΗΜΙΟ ΘEΣΣΑΛΙΑΣ, ΣΧΟΛΗ ΓEΩΠΟΝΙΚΩΝ EΠΙΣΤΗΜΩΝ, ΤΜΗΜΑ Γ... more Eιδικά Θέματα Γeωργικής Μηχανολογίας [ΠΑΝEΠΙΣΤΗΜΙΟ ΘEΣΣΑΛΙΑΣ, ΣΧΟΛΗ ΓEΩΠΟΝΙΚΩΝ EΠΙΣΤΗΜΩΝ, ΤΜΗΜΑ ΓEΩΠΟΝΙΑΣ ΦΥΤΙΚΗΣ ΠΑΡΑΓΩΓΗΣ ΚΑΙ ΑΓΡΟΤΙΚΟΥ ΠEΡΙΒΑΛΛΟΝΤΟΣ]
Γeωργική Μηχανολογία [ΠΑΝEΠΙΣΤΗΜΙΟ ΘEΣΣΑΛΙΑΣ, ΣΧΟΛΗ ΓEΩΠΟΝΙΚΩΝ EΠΙΣΤΗΜΩΝ, ΤΜΗΜΑ ΓEΩΠΟΝΙΑΣ ΦΥΤΙΚΗΣ... more Γeωργική Μηχανολογία [ΠΑΝEΠΙΣΤΗΜΙΟ ΘEΣΣΑΛΙΑΣ, ΣΧΟΛΗ ΓEΩΠΟΝΙΚΩΝ EΠΙΣΤΗΜΩΝ, ΤΜΗΜΑ ΓEΩΠΟΝΙΑΣ ΦΥΤΙΚΗΣ ΠΑΡΑΓΩΓΗΣ ΚΑΙ ΑΓΡΟΤΙΚΟΥ ΠEΡΙΒΑΛΛΟΝΤΟΣ]
Ø1.8 mm) malzemelerden üretilmiş içi boş konik hüzmeli meme kullanılmıştır. Plastik meme plakalar... more Ø1.8 mm) malzemelerden üretilmiş içi boş konik hüzmeli meme kullanılmıştır. Plastik meme plakalarının her birinde 4 farklı renkte (mavi, yeşil, sarı ve pembe) imal edilmiş girdap plakaları; paslanmaz çelik ve seramik memeler için standart tip çelik girdap plakası kullanılmıştır. Çalışmada toplam 27 adet meme-girdap plakası kombinasyonu için 1, 2, 3, 4, 5, 6, 8, 10 ve 12 bar işletme basınçlarında debi ölçümleri yapılmıştır. Her bir kombinasyonda kullanılan memeler için akış katsayıları hesaplanmış, tam pülverizasyon için gerekli minimum işletme basınçları belirlenmiş ve pülverizasyon karakteristikleri tahmin edilmiştir. Araştırma sonuçlarına göre; içi boş konik hüzmeli memelerde kullanılan girdap plakaları memenin işletme özelliklerini değiştirmiştir. Aynı orifis çapına sahip plastik memelerde ölçülen debi, paslanmaz çelik ve seramik memelerden daha düşük bulunmuştur. Orifis çapı arttıkça akış katsayısı azaldığı gibi pülverizasyon için gerekli minimum işletme basıncı değeri de düşmüştür. Plastik memelerde akış katsayısı 0.141-0.457; paslanmaz çelik memelerde 0.453-0.560; seramik memelerde 0.439-0.608 aralığında değişmiştir. Konik hüzmeli memelerde pülverizasyonun oluşması için gerekli minimum işletme basıncının, orifis çapı arttıkça azaldığı belirlenmiştir. Orifis çapı Ø1.0 mm ve Ø1.2 mm olan içi boş konik hüzmeli memelerin 10 bar işletme basıncının üzerinde çok ince yapılı (<100 μm) damlalar ürettiği saptanmıştır. Plastik memelerin 4-8 bar işletme basıncı aralığında ince yapılı (100-175 μm) damlalar ürettiği belirlenmiştir. Orifis çapı Ø1.5 mm ve Ø1.8 mm olan seramik memelerin ise 3 bar işletme basıncında orta yapılı damlalar (175-250 μm) ürettiği saptanmıştır. Anahtar kelimeler: Akış katsayısı, damla çapı, girdap plakası, konik meme, meme plakası Determination of Discharge Coefficient and Some Operational Features of Hollow Cone Nozzles
Precision agriculture is the management of spatial and temporal variability of the fields using I... more Precision agriculture is the management of spatial and temporal variability of the fields using ICT. The application in horticultural crops was developed in the last ten years. Data are collected from different sources (yield and quality, soil properties, remote sensing), stored to GIS data bases, analysed using geostatistical methods to develop management zones and decision support systems are used to assist farmers to the management. Variable rate application systems were developed to apply inputs according to the real requirements of the plants in the management zones. Although variability is a well established fact, farmers’ adoption is rather slower than expected because the system is complicated and in many cases profitability is not well demonstrated. Additionally, environmental benefits cannot take direct monetary values for the farmer. PA has a wider application impact like precise movement and management of farm machinery, development of efficient mechanization and fleet m...
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Papers by Theofanis Gemtos