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- 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.