Journal of Food, Agriculture and Environment

Genotype and planting date effects on cotton growth and production under south Portugal conditions – I. Phenology and growth analysis

Author(s):

Gonçalo Barradas ^1*, Rafael J. López-Bellido ²

Recieved Date: 2009-01-16, Accepted Date: 2009-03-29

Abstract:

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 low-night 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 relative growth rate (RGR) (0.065 to 0.105 g g^-1 day^-1) and net assimilation rate (NAR) (8 to 13 g m^-2 day^-1), in the beginning of the season and on absolute growth rate (G) (1.7 to 3.4 g plant^-1 day^-1), leaf area index (LAI) (2.6 to 4.6) and crop growth rate (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.

Keywords:

Gossypium hirsutum, phenology, growth analysis, genotype earliness, planting date

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Journal: Journal of Food, Agriculture and Environment
Year: 2009
Volume: 7
Issue: 2
Category: Agriculture
Pages: 300-312

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