Características físicas e fisiológicas de sementes de milho submetidas ao sistema de trilha manual e mecanizada em cinco teores de água

Abstract

The agricultural frontiers are expanding, making himself look for new technologies to optimize production, especially in large cultures. Corn (Zea mays L.), is a very important crop in Brazil, where the use of agricultural machinery is essential in all stages of cultivation, taking care to avoid damage mainly in the harvesting stages. The objective was to evaluate the physical and physiological characteristics of maize seed harvested in different moisture ranges and submitted to manual and mechanized threshing. The experiment was conducted in the experimental area of the Department of Agricultural Engineering of the Federal University of Ceará and UFC Seed Laboratory. The machinery used was a stationary threshing coupled to the power shaft of a tractor. Eight corncobs were taken at random every two days, which four were manually threshed and the remaining four, husked and past the stationary thresher. The seeds were divided into five classes according moisture contained in the seeds, the classes were 30.3 to 26.9% (T1); 26.9 to 23.5% (T2); 23.5 to 20.1% (T3); 20.1 to 16.7% (T4) and 16.7 to 13.3% (T5). The experimental design consisted of a factorial 5 x 2 (humidity x threshing) in completely randomized design - DIC. The seeds were evaluated for physical and physiological quality and submitted in addition to the measurement of humidity, several tests: mechanical damage, laboratory germination test, germination test on the field for the emergence speed index (ESI), final stand, thousand seed weight (TSW) and tetrazolium test. Mechanical damage were observed in seeds harvested with higher moisture content, the germination values were significant only for the threshing factor, it is the manual threshing and that resulted in more normal seedlings. The emergence speed was similar in both methods of threshing, making a difference only in the final stand, where mechanically threshed seeds germinated less. The threshing factor did not influence the TSW, it is the largest value found those obtained with lower water content, because of their lower presence of photoassimilates and greater loss of water when stored the harvested first, there was interaction between the two factors and it was observed that the moisture Mechanical of T3, T4 and T5 resulted in heavier seeds. The threshing was not significant for the tetrazolium test, and the moisture range of 16.7 to 13.3% obtained with the best seed germination potential, this potential decreased as humidity increased to harvest. The humidity did not affect the germination, however, mechanized threshing, showed problems in the force and damage to the seeds when harvested with higher moisture content, after which the seeds with 16.7 to 13.3% moisture that had the most vigorous seeds and minor mechanical damage to the threshing.