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An irrigated field trial was conducted to test the effects of white clover in three turfgrass species (perennial ryegrass, Kentucky bluegrass, and creeping bentgrass) on color, clipping yield, and botanical composition and to estimate nitrogen (N) 2 fixation and N transfer from white clover to associated turfgrass species under different N-fertilization conditions in 1999-2002.Nitrogen fertilizers significantly increased color ratings in all observations. Grass-white clover mixtures had better color ratings than pure grass at all sampling dates and seasonal averages in unfertilized conditions. Fertilized pure grass plots yielded significantly more than control plots in all turfgrass species. Nitrogen fertilization did not affect clipping yield greatly in turfgrass -white clover mixtures. Nitrogen application significantly decreased white clover percentage in the harvested clippings in second and third year.Nitrogen fertilization increased tissue N concentration positively in all turfgrass species grown alone. In contrast, N fertilization did not greatly affect tissue N concentration of either turfgrass species or white clover in the mixtures. Nitrogen fixation of white clover was estimated as 24.6, 30.7, and 33.8 g m 22 year 21 in perennial ryegrass, Kentucky bluegrass, and creeping bentgrass, respectively. The total estimated N 2 fixation gradually decreased with increasing N fertilization. Nitrogen transfer from white clover to the associated turfgrass varied from 4.2 to 13.7% of the total N that the white clover fixed annually.

Irrigated field experiments were conducted in the Marmara region of Turkey in 2002 and 2003 to compare alternate 40 : 25 cm row spacings and conventional 65 cm with four different plant densities (65 000, 85 000, 105 000 and 125 000 plants ha−1) of three corn hybrids (DK‐585, ADA 95–10 and C‐955) in some morphological traits and forage and dry matter yield. Morphological traits such as plant height, leaf per plant, stem diameter, ear per plant and ear percentage were measured, forage and dry matter yield was also determined in this study. Hybrids, row spacings and plant densities significantly affected some morphological traits, forage and dry matter yield at 0.01 level. Later maturing hybrids tended to produce taller and thicker stemmed plants. Row spacings and plant densities did not affect plant height. Average stem diameter increased significantly with population density. Row spacings did not influence leaf number, whereas leaf number increased slightly with plant density. On average, all corn plants had slightly more than 1.0 ear per plant in our experiment. Row spacings and plant densities did not affect significantly number of ear per plant. Early maturing DK‐585 had the highest ear percentage whilst late maturing C‐955 lowest. Yields usually increased with hybrid maturity. When averaged across years, row spacings and plant densities, late maturing C‐955 performed significantly better in forage and dry matter yield in all experimental years and combined years. The studies showed favourable advantage for alternate 40 : 25 cm rows over conventional 65 cm row spacings at all plant densities. Average forage and dry matter yields were greater for alternate 40 : 25 cm row spacings than for 65 cm row spacings. However, strong hybrid × row spacing interactions for both forage and dry matter yield were detected.

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The objectives of this study were to evaluate dry matter (DM) yield and seed yield of six leafed and semi-leafless pea (Pisum sativum L.) genotypes, and to compare them for these traits. Evaluation of genotype × environment (G × E) interaction, stability and cluster analysis were also carried out at eight diverse locations with typical Mediterranean and Mediterranean-type climate during the 2001-2002 and 2002-2003 growing seasons. Significant differences were found among the pea genotypes for DM and seed yield on individual years and combined over years, and in all locations. All interactions which related to G × E interaction showed significance (P>0.001) for DM and seed yield. The highest yield (4789 kg ha -1 ) was obtained from the leafed genotype 'Urunlu'. However, stability analysis indicated that for DM yield, the leafed genotypes 'Golyazi' and 'Urunlu' should be grown in low yielding and high yielding environments, respectively. Cluster analysis, based on grouping locations, showed that P101 was the preferred variety in low yielding environments, and P98, in high yielding ones. It was suggested that the use of both stability and cluster analyses might give better results. Comparison of cluster and stability analyses showed that the stability analysis fails to recommend cultivars to different regions where yield potential showed significant differences. It seems, however, that cluster analysis could be a powerful tool to examine G × E interaction. If the number of environments was sufficient, a separate stability analysis could be run in each cluster.Additional key words: adaptation, cluster, leafed and semi-leafless peas, Mediterranean conditions, stability. ResumenInteracción genotipo × ambiente y análisis de estabilidad para rendimiento de materia seca y de semilla en guisante (Pisum sativum L.)Los objetivos de este estudio fueron evaluar y comparar el rendimiento de materia seca (DM) y de semilla de seis genotipos de guisante con hojas convencionales y semiafilas. Además, se evaluó la interacción genotipo × ambiente (G × E) y se realizaron análisis de estabilidad y tipo cluster en ocho localidades de clima mediterráneo, durante las temporadas 2001-2002 y 2002-2003. Se encontraron diferencias significativas entre genotipos para rendimiento de DM y de semilla, tanto para años individuales como combinados, así como en todas las localidades. Todas las interacciones G × E fueron Field pea adaptation and stability 97 significativas (P>0,001) para rendimiento en DM y semilla. Se obtuvo la producción más alta (4789 kg ha -1 ) con el genotipo de hoja convencional 'Urunlu'. El análisis de estabilidad indicó que, para rendimiento en DM, los genotipos 'Golyazi' y 'Urunlu' deben cultivarse en ambientes de baja y alta producción, respectivamente. El análisis cluster, basado en agrupamiento de localidades, mostró que la variedad P101 fue la mejor en ambientes de baja producción, y la P98 en los de alta producción. Al comparar los análisis de estabilidad y de tipo cluster se vio que el primero falla al recome...