Trocas gasosas, crescimento e produção de sorgo sacarino sob lâminas de irrigação com água salobra e doses de potássio

Abstract

The careful use of water does not often carry out in many farming’s, causing a shortage of hydric resources. In addition, the high balance of solar energy available to the evapotranspiration processes, jointly with the irrigation adoption, can result in higher concentrations of salt in the soil. Thus, the use of the brackish water associated with the potassium fertilisation requires a lot of cares, since agricultural production might be restricted, reducing cultivation productions by anti-economic levels, especially in arid and semi-arid regions. That way, the comprehension of these raw materials effects in the sorghum is relevant to understand physiological mechanisms that the plant uses to tolerate the stress. Therefore, the goal of this study is to evaluate the irrigation depth effects with brackish water and doses of potassium in the growth and sweet sorghum in the semi-arid region of Pernambuco-Brazil. The experimental design was a randomized block (CBC) arranged in factorial structure (5 x 5), five irrigation depth with brackish water (40, 70, 100, 130, and 160% of the ETc), and five doses of potassium (0, 50, 100, 150 and 200% recommended to the cultivation) with four repetitions. The plant height, stem diameter, stem green mass, leaf green mass, panicle green mass and total green mass was observed. Increasing water replenishment with brackish water associated with doses of potassium increased the leaf gas exchange and generated larger sorghum growth and productivity. The study reveals the use of irrigation depth that corresponds to 160% of Etc provided productive gains up to 43, 71 Mg ha-1, and therefore, the use of water saline in the sorghum cultivation can be an option to use in the irrigation. The potassium fertilization with the IPA doses recommendation (20kg ha-1 of K2O) provided better increments in the variables that were analysed and was thus adapted for the tested variety (IPA SF15) and the management conditions.