Christos Noulas

SUBSOIL ROOT GROWTH OF FIELD GROWN SPRING WHEAT GENOTYPES (TRITICUM AESTIVUM L.) DIFFERING IN NITROGEN USE EFFICIENCY PARAMETERS

In a two-year (1999–2000) field experiment four Swiss spring wheat (Triticum aestivum L.) genotypes (cvs. ‘Albis’, ‘Toronit’ and ‘Pizol’ and an experimental line ‘L94491’) were compared for genotypic differences in the root parameters that determine uptake potential and nitrogen use efficiency (NUE):root surface area (RSA) and its components, root length density (RLD) and the diameter of the roots. The genotypes were grown under no (N0) and under ample fertilizer nitrogen (N) [ammonium nitrate (NH4NO3); N1; 250 kg N ha−1] supply. Root samples were taken from all the genotypes at anthesis from the subsoil (30–60 cm). Genotypic effects on RLD and RSA were evident only in 2000 and large amounts of N fertilizer usually diminished root growth. Adequate soil moisture in 1999 may have favored the establishment of the root system of all the genotypes before anthesis. Parameters of NUE for each genotype were also determined at anthesis and at physiological maturity. ‘Albis’ the least efficient cv. in recovering fertilizer N (ranged from 36.5 to 61.1%) with the lowest N uptake efficiency (0.47 to 0.79 kg kg−1) had the lowest RLD and RSA in both seasons. Among genotypes ‘Toronit’, a high-yielding cv., efficient in recovering fertilizer N, exhibited the higher NUE (22.4 to 29.3 kg kg−1) and tended to have the highest values of RLD and RSA. Nitrogen fertilization also led to an increase in the proportion of roots with diameters less than 300 μm and decreased the proportion of roots with diameters of 300 to 700 μm. These trends were more pronounced for cv. ‘Pizol’ in 1999 and for cv. ‘Toronit’ in 1999 and 2000. By anthesis in a humid temperate climate, there are no marked differences in the subsoil root growth of the examined genotypes. Some peculiarities on the root growth characteristics of the cultivars ‘Albis’ and ‘Toronit’ may partially explain their different NUE performance.

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.

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.

Evaluation of lentil varieties and farming system effect on seed damage and yield loss due to bruchid (Bruchus spp.) infestation

Abstract. A major constraint of lentil (Lens culinaris Medik.) cultivation is yield reduction due to field infestation by the seed beetles Bruchus spp. (bruchids). The aim of the study was to assess seed loss (SL) and yield loss (YL) due to bruchid infestation under organic and conventional farming, and to investigate genotypic variability for seed yield of 20 lentil varieties in response to bruchid damage. Field experiments were established over three consecutive years in two areas of central and northern Greece. SL was determined as the percentage of damaged seeds, whereas the weight of the damaged seeds was estimated as YL. Farming system was the main source of variation for both SL and YL. Mean SL under organic farming was 15% and mean YL was 0.13 t ha–1. SL and YL were 2.6- and 8.4-fold higher, respectively, under organic than conventional farming. Valuable genotypic variability was observed with respect to both SL and YL. Early flowering and small seed size were traits associated with low SL and YL. Among varieties, mean SL ranged from 8.5% to 29.2% and YL from 0.06 to 0.31 t ha–1. Evaluation for high yield potential, indicating bruchid tolerance, revealed two types of promising varieties: varieties with high yield and low seed bruchid damage due to phenological escape, and varieties with high yielding potential despite the high SL and YL.

Agronomic Assessment of Nitrogen Use Efficiency in Spring Wheat and Interrelations with Leaf Greenness Under Field Conditions

ABSTRACT Four spring wheat genotypes (Triticum aestivum L.) were grown without (N0 = 0 kg N ha−1) and under ample (N1 = 250 kg ha−1) nitrogen (N) fertilizer in field experiments in two seasons. The aim was to assess genotypic variation in N use efficiency (NUE) components and N-related indices during grain filling thus to identify superior wheat genotypes. Leaf chlorophyll (SPAD) readings at crucial growth stages were employed to help differentiate genotypes. Interrelations between yield and N-related indices with SPAD, where also assessed to explain possible pathways of improving NUE early in the growing season. Results showed that genotypic effects on NUE were mostly evident in 2000, a year with drier preanthesis and wetter postanthesis than the normal periods. ‘Toronit’ almost always had the highest biomass yield (BY) and grain yield (GY). Except in 1999 under N0, ‘L94491ʹ showed the highest % grain N concentration (GNC). Genotypes affected SPAD at almost all stages and N fertilization delayed leaf senescence for all genotypes and growth seasons. Correlations between SPAD at different growth stages and GY, N biomass yield at maturity (NBYM) and GNC were significant (P≤ 0.001), positive and strong/very strong (>r = 0.7). N translocation efficiency (NTE) was inversely related to PANU (~r = − 0.77, P≤ 0.001), suggesting that N after anthesis is being preferentially transported to the ears to meet the N demand of the growing grains. It is concluded that there is still a large potential for increased NUE by improved N recirculation, use of fast and inexpensive crop N monitoring tools and high yielding, N uptake efficient genotypes. Abbreviations: NUE, Nitrogen use efficiency; SPAD, Minolta SPAD-502 chlorophyll meter, NHI, nitrogen harvest index; HI, Harvest index; NTE, N translocation efficiency from vegetative plant parts to grain; DMTE, dry matter translocation efficiency; CPAY, contribution of pre-anthesis assimilates to yield; PANU, Post-anthesis N uptake, d.a.s., days after sowing, N0, zero (0) kg ha−1 applied N fertilizer, N1, 250 kg ha−1 applied N fertilizer.

Morphology and distribution of wheat and maize roots as affected by tillage systems and soil physical parameters in temperate climates: an overview

ABSTRACT Congregated information on maize and wheat root morphology and their distribution as influenced by tillage and soil physical conditions is meager. Root growth under no-tillage (NT) or conventional tillage (CT) is variable: Under NT, higher bulk density slows root elongation and provides shorter roots but simulate root branching; results may be opposite depending on soil texture. Under CT, soil compaction may have negative effects on root growth, with roots exhibiting plasticity. In humid climates, low soil temperatures can reduce root length density (RLD) and increase the diameter of spring cereals under NT. Tillage intensity induces a different distribution of nutrients, a trend which increases with time resulting in higher RLD in the topmost layer of NT. Compared to maize it is difficult to present an overview of the effect on tillage on the RLD of wheat due to inconclusive results. Adequate placements of banded starter fertilizer will effectively build up an early root system of maize, especially at suboptimal growth temperatures. Many studies reported a higher or similar grain yield of maize or wheat under NT compared to CT in temperate climates. However, the limited information or the conflicting results will promote the topic for inclusion in future breeding programs.

COURSE OF DRY MATTER AND NITROGEN ACCUMULATION OF SPRING WHEAT GENOTYPES KNOWN TO VARY IN PARAMETERS OF NITROGEN USE EFFICIENCY

Field experiments were conducted for two years to compare and identify bread spring wheat (Triticum aestivum L.) genotypes which make the most efficient use of nitrogen (N). Such information is required for breeding strategies to reverse the negative relationship between yield and protein content. Three Swiss spring wheat cultivars (‘Albis’, ‘Toronit’, ‘Pizol’) and an experimental line (‘L94491’) were grown without (N0; 0 kg N ha−1) and with high fertilizer N [(NH4NO3); (N1; 250 kg N ha−1) supply on a clay loam soil with low organic matter content. Biomass and nitrogen accumulation in biomass as well as the leaf growth and senescence patterns (SPAD) were investigated in an attempt to explain the physiology of growth and N translocation of these genotypes. The pre-anthesis accumulation of biomass and N in the biomass depended on genotype only at N1 in 2000. In this year, conditions were less favorable for the pre-anthesis accumulation of biomass and N, which was, on average, 10 and 20% lower, respectively, of the total than in 1999. The contribution of pre-anthesis assimilates to the grain yield (CPAY) was higher in 1999 for all genotypes (36.9%) compared to 2000 (13.5%) except ‘Toronit’. Between anthesis and maturity the climate influenced the genetic variability of some N use efficiency components: N translocation efficiency (NTE) and dry matter translocation efficiency (DMTE). NTE was higher in 1999 (68.1%) compared to 2000 (50.7%); 1999 was a year in which the post-anthesis period was drier and warmer than usual. ‘Toronit’ produced the highest biomass by maturity due mainly to greater and longer lasting green leaf area after anthesis. ‘Albis’ performed relatively well under low input conditions, with considerable amounts of N being re-translocated to the seeds at maturity (NHI), whereas ‘Pizol’ accumulated in grains N as high as for ‘L94491’. In a humid temperate climate breeding for greater N uptake and partitioning efficiency may be a promising way to minimize N losses and produce high phytomass and grain yields. Using high protein lines as selection material and combining them with high biomass genotypes may lead to high protein contents without decreasing yield.