Percorrer por autor "Lopez-Bellido, Rafael J."
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- Genotype and planting date effects on cotton growth and production under south Portugal conditions – I. Phenology and growth analysisPublication . Barradas, Gonçalo; Lopez-Bellido, Rafael J.Genotype earliness and date of sowing are two of the most critical aspects in the management of cotton (Gossypium hirsutum L.) in Mediterranean climates, where low temperatures at sowing and low temperatures and raining during boll period and harvest are the main weather constrains of the season length. The aim of this work was to determine the influence of cultivar maturity type and planting date on phenology and growth indexes. Six genotypes and three sowing times were studied in one field experiment conducted in 2002 and 2003 at Comenda Experimental Station, Alentejo, Portugal. No significant differences were accounted between genotypes in each phenological phase periods and in the whole growing season durations. Inversely, planting date delay had a clear impact on shortening of some phenological periods, namely, planting-emergence (-7.5 days), emergence-first square (-19 days) and first flower-first open boll (-15.5 days). The poor heat unit accumulation and unfavorable high-day and lownight temperatures registered after 15 August deeply affected the boll period duration, which surpass the standards higher limit intervals referred for California and Andalusia. Logistic growth asymptote (A) varied significantly with genotype (64.9 to 229.5 g plant-1) and year (84.1 to 165.6 5 g plant-1) but without any regular pattern between planting dates. The number of days after planting to reach maximum growth rate (C) decreased significantly with planting date delay (122.8 to 98.7 DAP) and varied significantly between both years (104.6 to 117.7 DAP). In contrary, the B constant (maximum relative growth rate) experienced no significant differences between the two factors in study (0.075 g g-1 day-1). Genotype and planting date had significant impacts on RGR (0.065 to 0.105 g g-1 day-1) and NAR (8 to 13 g m-2 day-1), in the beginning of the season and on G (1.7 to 3.4 g plant-1 day-1), LAI (2.6 to 4.6) and GCR (13.1 to 26.7 g m-2 day-1) in the mid and late season. The two former growth indexes reach higher values in the early growth stages, decreasing deeply thereafter until the end of the season. On contrary G, LAI and CGR presented a bell shaped distribution pattern along the season, with peak CGR taking place 15 to 30 days after the beginning of the flowering period and peak LAI 22 to 30 days after peak CGR. However, data analyses of those growth indexes reveal inconsistent variation patterns among the two studied factors. It was concluded that further studies using a larger range of maturity type cultivars are necessary in order to provide valuable phenological and growth indexes baseline values for cotton grown in the southern Iberian Peninsula.
- Genotype and planting date effects on cotton growth and production under south Portugal conditions – II. MonitoringPublication . Barradas, Gonçalo; Lopez-Bellido, Rafael J.Monitoring is a frequent practice in the high-yielding cotton producing regions, furnishing precious information to decision making during the growing season and contributing to understand growth and development of cotton plants. The aim of this work was to determine the influence of cultivar maturity type and planting date on the main monitoring indexes: plant height (H), number of main-stem nodes (MSN), height-to-node ratio (HNR) and number of nodes above white flower (NAWF). Six genotypes and three sowing times were studied in one field experiment over two seasons at Comenda Experimental Station, Alentejo, Portugal. Best regressions of H and MSN to accumulated degree days (DD) along the season were quadratic models, with significant differences between genotypes and years. Consequently, heat unit’s requirements per each new cm height and new main-stem node (plastochrons) increase linearly. Between genotype H differences were find just after first-flower (550 DD), whilst MSN differences were find only after first open boll (1000 DD). Both differences emphasize until the end of the season. Inter-annual differences were also find in H, at first-flower (500 DD) and in MSN, a bit earlier (400 DD). No planting date influence on H or MSN were detected. Best regressions of HNR to DD were inverse models, also with significant differences between genotypes and years. ‘Celia’ and early planting dates presented lower NFFB. Behavior of NAWF since first-flower to cutout (NAWF = 5) was well explained by linear models, regression coefficients (NAWF decrease per day) showed only between genotype differences. Contradictory signs of maturation types were find. Low H and MSN plastochrons and low final vigor index suggests precocity but, in contrary, relatively high NFFB, initial vigor index, final H and high number of days to cutout, suggests late maturing tendencies of our studied cultivars as a whole. Planting date can be underlined as a management practice with relatively low influence on H, MSN, HNR and NAWF evolution. However, especial attention must be given on the influence of planting date on NFFB, once this monitoring index is strikingly linked with precocity, feature particularly important for regions with growing season duration constrains. Further annual monitoring data and analysis is necessary in order to allow their use as decision making tools available to the main cotton producing regions of southern Iberian Peninsula.
- Genotype and planting date effects on cotton growth and production under south Portugal conditions. III. Boll set percentage, boll location, yield and lint quality.Publication . Barradas, Gonçalo; Lopez-Bellido, Rafael J.Assimilate diversion of vegetative growth, reinforced by inadequate temperatures to growth and maturation of bolls later set in season, resulted in poor harvest indexes and low retention, mainly at the first fruit positions and on lower fruiting branches. Significant differences of seed-cotton production between genotypes were observed, and higher values were attained by variety Celia, presenting more short season characters. The delaying of the planting date, while allowing better emergence and initial growth of the plants, shorten the available growing season and has a negative impact on seed cotton production. Thus, in Caia region, short season cultivars and early planting dates are best suited to cotton production, also being important to achieve high boll retention in the first positions and fruiting branches, in order to approach the boll growth and maturing period with more favourable environmental conditions. Fiber color grading shows no significant differences between varieties and planting dates, although differences were found in some of the commercial and technological quality measurements.
- Seed weight, seed vigor index and field emergence in six upland cotton cultivars.Publication . Barradas, Gonçalo; Lopez-Bellido, Rafael J.In regions where a short growing season is combined with low soil temperatures at sowing, field emergence and stand establishment is one of the most critical stages in cotton production. This study evaluates the relations between seed weight, seed vigor index and field emergence on 6 upland cotton (Gossypium hirsutum L.) genotypes, grown at Alentejo (Portugal). Leaf area per cotyledon, cotyledons to total leaf area and to total dry weight ratios were also analyzed. Seed vigor index, the sum of cold and standard germination tests, showed significant differences between genotypes, and different year to year soil temperatures had a significant impact on seedling emergence. No significant correlations were found between field emergence and seed weight or seed vigor index. However, poor positive linear relationships were found between seed weight and seed vigor index, as well as between standard test and field emergence. Probably, the expected impact of seed quality on field emergence was overlapped or confused by the influence of other factors (soil crusting) than temperature physical stress exerted over seeds. Cotyledons per total leaf area and dry weight represent important proportions of the entire plants during the relatively long seedling period often observed in the cotton crop grown on marginal spring weather conditions.