Theodore Karyotis

Nutrients and Trace Elements of Arable Soils Rich in Organic Matter

Abstract The distribution and the status of macronutrients and trace elements in surface soil samples originated mainly from organic deposits of Philippoi (northern Greece) were investigated. These soils are classified as Histosols and belong to the suborder of Saprists (1). The pH of examined samples ranged from 5.1 to 7.8 and the total soil nitrogen (Ntot) varied from 4.0 to 21.8 g kg−1. The total soil carbon (Ctot) ranged between 116.0 and 336.5 g kg−1, whereas the organic carbon (Corg) was between 109.4 and 335.5 g kg−1 and the C:N ratio varied between 12.4 and 29.3. Calcium carbonate (CaCO3) was not detected in all surface horizons, and the exchangeable calcium (Ca++) ranged between 12.95 and 54.65 cmol kg−1. This suggests the impact of aquatic organisms (which contain CaCO3) on soil enrichment with calcium by means of weathering process. Micronutrients extracted by 4 M HNO3 were in the following order iron (Fe)>manganese (Mn)>zinc (Zn)>copper (Cu). The distribution of trace elements extracted by DTPA varied considerably among the examined soil samples. The following range was found: Fe 97.5–579 mg kg−1, Mn 1.48–53.0 mg kg−1, Cu 0.24–10.4 mg kg−1, and Zn 0.5–23.9 mg kg−1. Total soil nitrogen was closely related to Corg, whereas soil properties showed considerable variability. This may reveal the factors responsible for deposition process, degree of soil development; part of this distribution may be attributed to intensive farming activities. Symptoms of Fe deficiency have been observed, which may be ascribed mainly to the presence of CaCO3. Deficiency of Cu was also recorded in maize (Zea mays L.) cultivated in slightly alkaline soils. Geostatistics have been used for a quantitative depiction in maps of nutrient status and variability. A combination of measures, such as water management, tillage practices, application of proper rotation schemes, and recommendation of rational fertilization practices, is expected to maintain soil quality and enhance fertility.

Incubation Experiments on Net Nitrogen Mineralization in Organic Greek Soils

Abstract Aerobic incubation experiments were conducted in organic surface samples collected from arable soils of Philippoi, in Northern Greece. Laboratory experiments were carried out to investigate the nitrogen (N) mineralized from soils and sugar beet residues incorporated into the soils. Cumulative mineralization of N, potentially mineralizable nitrogen (N0), and mineralization rate constant k were estimated after 30 continuous incubation weeks at 35°C. Total N content of soils ranged between 6.6 and 19.2 g kg−1, total soil carbon from 119 to 309 g kg−1, soil organic carbon ranged from 119 to 308 g kg−1, and the C∶N ratio varied from 13.5 to 18.3. The cumulative net mineralized N ranged between 132 and 426 mg kg−1 for nonamended soil and between 165 and 586 mg kg−1 for residue‐amended soil. Nitrate was the main form of mineralized N, although appreciable amounts of ammonium were measured. Potentially mineralizable nitrogen (N0) varied between 254 and 1067 mg kg−1 for nonamended soil and 311–1465 mg N kg−1 in residue‐treated soil. The mineralization constant k was between 0.052 and 0.068 (week−1). Close relationships between total soil N and soil organic carbon, and between cumulative mineralization and total soil N were found. Mineralization occurred rather rapidly, although the amount of mineralized N per week was reduced in the later weeks of incubation. Variation in net mineralization among soil samples can be attributed to soil organic matter content, origin, and state of decomposition, as well as differences in management histories, and soil and microenvironmental conditions. Monitoring of mineralization process may ensure a basis for increasing nitrogen use efficiency.

Soils and Native Vegetation in a Hilly and Mountainous Area in Central Greece

Soils and native vegetation were investigated in 24 sites in the hilly and mountainous province of Elassona, central Greece. Most soils consist of coarse alluvial material that originated from the weathering of hard limestone or schist. Mostly are acidic, and the coarse texture enhances the leaching of exchangeable cations. Mean soil organic matter is greater than values recorded in the lowlands. Low content of available phosphorous (P) was observed in certain soils, and this may be attributed either to P fixation in the clay minerals or to parent material. Copper (Cu) content was low in 11 samples, and the content of exchangeable calcium (Ca++) was lower than the critical level in two thirds of samples. Similarly, low values were recorded for exchangeable magnesium (Mg++) and potassium (K+). Results from annual plants have shown low nitrogen (N) content and partial deficiency in Ca, K, and Mg, which reflects the particular soil and climatic conditions. Furthermore, in certain samples Cu, manganese (Mn), and zinc (Zn) were found at deficiency levels. Samples from perennial plants were selected from sites where vegetation was degraded. Results revealed nitrogen (N), Mn, and Cu deficiency, and the values for micronutrients iron (Fe), Zn, and boron (B) were greater than critical levels. Practices and measures are suggested to improve soils and to restore the degraded vegetation, such as application of lime material in the acidic soil for correction of pH, rational water management, cultivation of crops with low water requirements, banning of overgrazing in areas vulnerable to erosion, winter cover of slopes with pasture and fodder crops, establishment of permanent shrubs, reforestation of certain hilly and mountainous areas, and training of farmers. Findings of this study can assist local authorities in managing natural resources in a more rational and sustainable manner. Establishment of pasturelands in combination with rational grazing management should be of high priority to sustain livestock production.

Net Nitrogen and Sulfur Mineralization in Mountainous Soils Amended with Indigenous Plant Residues

Abstract Mineralization of nitrogen (N) and sulfur (S) were examined over a 31‐week incubation period under aerobic conditions in 13 soils selected from the mountainous district of Pertouli, central Greece. The main native plant species are turf, forage crops, forest trees, herbs, and shrubs. Net mineralization and immobilization of N and S by indigenous plants were estimated. Most soils are acidic in this xeric, mesic climatic regime, and organic carbon (C), organic nitrogen (N), and sulfur (S) appreciably varied in soils and plant species. The cumulative net mineralization of N is much higher in comparison to the amount of mineralized S. Release of N is curvilinear with time and associated with a declining mineralization in the later stages of the incubation. Close relationships exist between soil organic S and N and between organic C and N, indicating that these elements are mainly bound in the organic matter. The cumulative net mineralization from soils varies greatly and ranges between 36.6 and 212.8 (average 104.8) mg/kg for N and between 21.4 and 45.2 (average 31.8) mg/kg for S. Immobilization occurs in most soils amended with indigenous plant residues, with the amount of immobilized N varying between 14.8 and 49.5 mg/kg and that of immobilized S ranging from 2.6 to 30.7 mg/kg. However, the estimated rates of N and S mineralization are not negligible and can be taken into account as potential sources in the management of the upland soils.

Zinc in soils, water and food crops

A basic knowledge of the dynamics of zinc (Zn) in soils, water and plants are important steps in achieving sustainable solutions to the problem of Zn deficiency in crops and humans. This paper aims at reviewing and discussing the relevant aspects of the role of Zn in the soil-water-plant agro biological system: from the origins of Zn in soils and water to soil Zn deficiency distribution and the factors affecting soil Zn availability to plants, therefore to elucidate the strategies potentially help combating Zn deficiency problems in soil-plant-human continuum. This necessitates identifying the main areas of Zn-deficient soils and food crops and treating them with Zn amendments, mainly fertilizers in order to increase Zn uptake and Zn use efficiency to crops. In surface and groundwater, Zn enters the environment from various sources but predominately from the erosion of soil particles containing Zn. In plants is involved in several key physiological functions (membrane structure, photosynthesis, protein synthesis, and drought and disease tolerance) and is required in small but nevertheless critical contents. Several high revenue food crops such as beans, citrus, corn, rice etc are highly susceptible to Zn deficiency and biofortification is considered as a promising method to accumulate high content of Zn especially in grains. With the world population continuing to rise and the problems of producing extra food rich in Zn to provide an adequate standard of nutrition to increase, it is very important that any losses in production easily corrected so as Zn deficiencies are prevented.

Improving Farming Practices in Municipality of Gazi, Crete, Greece

A soil survey and mapping program financed by the municipality of Gazi located on the north–central part of Crete was carried out. The studied area is characterized by a moist meso-Mediterranean climate and different degrees of land degradation from human activities. Surface soil horizons are eroded, resulting in fertility decline for olive trees, the dominant crop. According to the U.S. Department of Agriculture classification, the soils at higher altitudes are classified as Entisols xerorthents and those at lower altitudes as E. xerofluvents. Using a geographical information system (GIS), all spatial data from the soil survey were organized to facilitate its storage, management, and analysis. Based on topographic–geological maps and aerial photographs, other derivative data layers were calculated. Sampling points were determined using GIS. This information, and all results pertaining to the sample, was entered into a graphical database, designed to store all relevant data for each point. Data layers describing the spatial distribution of key parameters such as soil texture, pH, CaCO3, and nutrient status were produced using geostatistical methods. Soil classification and the evaluation of soil suitability for various activities were greatly facilitated by visualization of the data as various thematic maps. Our study demonstrates the ability of GIS as an administrative tool that can assist farmers in improving farming practices.

Nutrients, Trace Elements and Net N Mineralization in Acidic Kenyan Soils

The nutrients status and properties in Kenyan soils (Kiambu, Mbeere Districts) are reported with the aim to elucidate the factors of productivity decline. According to the FAO (1988) system the studied soils were classified as humic Nitisols, haplic Acrisols or luvic Arenosols. The soils were found acidic, as a result of leaching of exchangeable cations and they are poor in organic carbon. Cation exchange capacity was extremely low in the sandy soils of Mbeere. Available phosphorus and exchangeable K+ were low inducing a crucial problem of soil fertility. Among the micronutrients, manganese extracted by DTPA was most abundant element, while micronutrients extracted by 4 M HNO3 ranked as follows: Fe>Mn>Zn>Cu. Copper (DTPA) was low and manganese was extremely high in Kiambu. Iron content varied greatly, while decreased zinc was observed in Mbeere. Nitrogen mineralization over an incubation period of 30 weeks ranged from 54.64 to 145.50 mg kg−1 and represents 4.53–21.09% of the total soil nitrogen. Soil nitrogen was associated to soil organic carbon and was strongly correlated to total soil N. Water harvesting, liming, and improved management of composting and manure are amongst the measures to restore soil fertility.

Adaptation, Agronomic Potential, and Current Perspectives of Quinoa Under Mediterranean Conditions: Case Studies from the Lowlands of Central Greece

ABSTRACT Quinoa was cultivated for 7000 years by indigenous people of the Andes, but in recent decades it is gaining international attention because of its tolerance to abiotic stresses, the wide genetic variability, and its high nutritional value. Greece was among the European countries and in the Mediterranean basin, the first European country, which since 1995 was involved in the “American and European Test of Quinoa” organized by the Food and Agriculture Organization and the Quinoa Project “CIP-DANIDA.” The experiments (1995–2004) were conducted in the lowlands of Central Greece (Larissa region). The first experiments focused on the adaptation of quinoa varieties to warm and dry climatic conditions and to the effect of plant density on seed yield (SY). Drought, low relative humidity, high temperatures (>32 °C), and long days (during anthesis) were considered unfavorable for seed production. Moreover, crusting and drying up of the soil surface had a negative effect on the proportion (60–70%) of emerged seedlings. The best sowing density is considered to be 25 plants m−2. Considering the effect of sowing date on SY and quality, it was found that early sowing in March is more suitable (in areas where frost avoidance is ensured), whereas latest (May) sowing was unsuitable and resulted in poor germination. The evaluation of 25 quinoa varieties showed that only 8 (six European and two Latin American) varieties produced seeds, whereas the rest 17 produced only panicles and flowers. Dry matter quality of the produced stems was analyzed for protein and fiber content. Dry stems of the plants remained after seed harvest contained high percentage of fibers (45%). The eight most promising varieties were also evaluated for their yielding potential and their seed composition under contrasting soil properties. Compared to neutral soil conditions, SY in the saline–sodic soil was decreased up to 45%. Mineral and protein content in seeds was higher in the varieties originated from Latin America. SY for some varieties exceeded 1000–1500 kg ha−1, and seeds were rich in protein (15–18.5%) and minerals content. On a breeding program started in 2002, 23 families have been created using mass selection procedures for the creation of new varieties from plants survived in the saline–sodic soils. These selections had to be evaluated in dense sowing in typical SY experiments, but experimentation was discontinued in the absence of financial support. Farmers’ knowledge gaps on cultivation techniques, the distances from the European markets, and the absence of incentives are probably considered the major obstacles to date for crop’s expansion in Greece. Research should focus on the evaluation of promising genetic material in different agroecological zones including higher altitudes. Abbreviations: AETQ, American and European Test of Quinoa; FAO, Food and Agriculture Organization; SY, seed yield; a.s.l., above sea level; N, neutral soil; S-S. saline–sodic soil; B, branched plant types; UN-B, unbranched plant types.

Nitrogen Leaching Of Spring Wheat Genotypes (Triticum Aestivum L.) Varying In Nitrogen-Related Traits

Efficient use of nitrogen (N) by wheat crop and hence prevention of possible contamination of ground and surface waters by nitrates has aroused environmental concerns. The present study was conducted in drainage lysimeters for three years (1998–2000) to identify whether spring wheat genotypes (Triticum aestivum L.) that differ in N-related traits differ in N leaching and to relate parameters of N use efficiency (NUE) with parameters of N leaching. For this reason two spring wheat cultivars (‘Albis’ and ‘Toronit’) and an experimental line (‘L94491’) were grown under low (20 kg N ha−1) and ample N supply (270 kg N ha−1). The genotypes varied in parameters of NUE but not in N leaching. Grain yield of the high-protein line (‘L94491’) was, on average, 11% lower than that of ‘Toronit’ but among genotypes had significantly higher N in the grain (%), grain N yield, and N harvest index. Nitrogen lost through leaching was considerably low (0.42–0.52 g m−2) mainly due to low volume of percolating water or the ability of the genotypes to efficiently exploit soil mineral N. There were no clear relationships between N-related genotype traits and N leaching, but across all treatments significantly negative correlations between volume of leachate and the amount of N in the total biomass and grain N yield existed.

Variation of Properties in Surface Soils from a Prior Lake‐Bed (Lake Askuris, Greece) Farmed for Over 90 Years

Twenty‐seven soil samples were collected from surface horizons, in order to include representative soil types. Three samples per site were taken and mixed from the examined area, in spring 2005. The study area occupies 820 ha of the now‐drained (1910), partially levelled, and continuously farmed Lake Askuris in Greece. The area, which is close to the village of Kalipefki (Longitude: 22° 27′ 22″ E; Latitude: 39° 57′ 39″ N) and to Mount Olympus, is elevated (≈1000 m) with a Mediterranean climate of mild, rainy winters and hot, dry summers. In addition to clay content, the soils were chemically characterized using 22 soil chemical tests, including pH, total carbon and organic matter, total nitrogen, total sulphur, exchangeable cations, cation exchange capacity, organic and extractable phosphorus (P), and pseudo‐total and diethylenetriaminepentaacetic acid (DTPA) extractable trace elements. All of the soil data were skewed, with population mean values higher than the median for clay percentage, cation exchange capacity, carbon/nitrogen ratio, exchangeable calcium (Ca) and magnesium (Mg), DTPA iron (Fe), and total zinc (Zn). A geographic information system and kriging was used to prepare spatially explicit maps (at least two or three level of fertility) for the exchangeable basic cations, the trace elements, phosphorus, organic matter, total nitrogen (N), and total sulfur (S). It is expected these contemporary baseline data will assist the local community and farmers as they consider future nutrient management plans along with other land use options that could include re‐flooding the lake bed.”