Crescimento, desenvolvimento, produtividade e qualidade de sementes de chia em diferentes datas de semeadura

Abstract

The demand for functional foods such as chia has increased in recent years. In view of this, there is a need to expand studies with this species, mainly in agronomic aspects in the regions with adequate edaphoclimatic conditions for chia cultivation of the Rio Grande do Sul State. It is known that the sowing date influences the growth and the length of the development cycle and, consequently, the biomass production, grain yield and seed quality of different crops. Thus, this work aimed to characterize the growth, development, crop yield and seed quality of chia at different sowing dates. To achieve it, an experiment was carried out in five sowing dates (09/22/16, 10/28/16, 01/03/17, 02/08/17 and 03/24/17) in Santa Maria, RS. The experimental design was a complete randomized block design with four replicates. The variables evaluated in the field were: emergency date, plant height (cm), number of leaves (weekly), leaf area (every fifteen days) and the occurrence dates of some development stages. Three plants per plot (every fifteen days) were collected to determine the dry mass matter and to perform the growth analysis of the species at different sowing dates. The evaluation of the grain yield and the seed quality in the laboratory was also carried out. The physiological indexes indicated that at earlier sowing dates there is a greater plant growth, either in shoot dry matter mass, height and leaf area index. The leaf area index of the branches is increased with plant development and significantly contributes to the total leaf area of chia in all studied sowing dates. For the sowing dates studied, the main stem represents between 60 and 70% of the shoot dry matter mass accumulated in the plants of the early sowing dates, and between 40 and 50% in late sowings. The length of the vegetative phase of chia plants in days and in degree days varies between the sowing dates, with shorter duration in late sowings, in response to the photoperiod reduction. The vegetative phase represents the greatest part of the total development cycle in the early sowing dates, being overcome by the reproductive phase in the late sowing dates (02/08/17 and 03/24/17). The phyllochron for chia varies from 36.23 (very late sowing) to 59.88 ºC day (early sowing). Later sowings result in a smaller accumulated final number of leaves in the main stem due to the reduction in the mean photoperiod and the rapid induction to the reproductive phase. Chia can be sown from September to February providing seeds with high physical and physiological quality. The physical and physiological quality of chia seeds does not differ between main stem and the branches. For the studied dates, the best sowing month to achieve higher productivity of chia seeds in Santa Maria is January.