IRRIGATION FREQUENCIES FOR Eucalyptus grandis SEEDLINGS

One of the bottlenecks in relation to the production of forest seedlings is irrigation, especially in less-tech nurseries. The small volumes of substrate, where the seedlings develop, lead to low water storage. This fact can lead to water deficit and significant losses in the production of seedlings, generating even mortality. The objective of this study was to determine the best irrigation frequencies for Eucalyptus grandis seedling production in less-tech nurseries. The experiment was conducted between 2013/08/04 and 2013/23/07 (106 days) and conducted in Chapadao do Sul county, Brazil. The experiment was set up in a randomized complete block design, with five replications. Four irrigation frequencies were tested: IF1 (one daily irrigation - 11:00 a.m.), IF2 (two daily irrigations - 11:00 a.m. and 7:00 p.m.), IF3 (three daily irrigations - 07:00 a.m., 11:00 a.m. and 7:00 p.m.) and IF4 (four daily irrigations - 07:00 a.m., 11:00 a.m., 3:00 p.m. and 7:00 p.m.). The sample units were composed of eight seedlings in 50 cm3 conical tubes filled with soil and vermiculite in a volume ratio of 1:1. The irrigation depth was estimated by reference evapotranspiration (Penman-Monteith) multiplied by a crop coefficient equal to two. Plant height, number of definitive leaves, shoot dry mass (root and total), seed quality index, survival and efficiency of water use by eucalyptus seedlings were evaluated. The average daily irrigation depth in the experimental period was 5.2 mm. Based on the results, it is recommended for eucalyptus seedling producers, in less-tech nursery, irrigation management twice per days. (11:00 a.m. and 7:00 p.m.).