The effect of supplementary irrigation on same sunflower (Helianthus annuus L.) parameters

Author(s)

Evandro Machado Gomes

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia Civil, Arquitetura e Urbanismo
• Defense date: 2005-02-23

Examining board members

Dirceu Brasil Vieira; Maria Regina Gonçalves Ungaro; Fernando Braz Tangerino Hernandez; Abel Maia Genovez; Antonio Carlos Zuffo

• Advisor: Dirceu Brasil Vieira

Abstract

The study was conducted from 2001 to 2003, in Limeira (Brazil), with the sunflower hybrid M-742. The aim of the present work was to study the effect of the supplementary irrigation on some sunflower (Helianthus annuus L.) parameters. The sowing and harvest were done, respectively in June 18, September 14 in 2001; June 16, October 8 in 2002 and June 24, October 15 in 2003. The experimental design was a randomized blocks with three treatments and four replications. The treatments were: a) irrigation according to soil moisture (Always Irrigated); b) irrigation in the critical periods (Phases Irrigated) and c) without supplementary irrigation (Rainfed). The irrigation was performed by sprinkler and scheduled by gravimetric method. The main analyzed parameters were: head, leaves and stem dry weight and height; 1.000 seed mass; head diameter; oil and protein content; root system distribution; water demand. The data were submitted to analysis of variance and the averages were compared by Tukey test. Based upon the results some conc1usions are feasible: a) sunflower plants under sever water stress produces a higher root number that explore the soil deeply than plants with no water stress; b) the greater root concentration occurred in the superficial horizon, for all treatments. c) water supplementation during flower bud formation and grain filling stages is sufficient to assure good levels of grain yield and root system development; d) the water Stress causes an emphasize decrease in stem, head and leave dry mass; e) plants grown under accentuate water stress yielded 30% less than plants with no stress and 20% less than plants that received water only in the critical periods of bud formation and grain filling; f) the leaf area decrease through the plants height appears to be a mechanism of sunflower's defense to water stress; g) the sunflower under water stress increases protein and reduces oil seed content; h) the kc coefficient was lower at 20 days after emergence and higher at flower bud stage (AU)