Cultivo de girassol irrigado com água salina sob doses de nitrogênio.

Abstract

Sunflower cultivation irrigated with saline water under nitrogen rates. The sunflower (Helianthus annuus L.) is one of the most potential oilseed specie for the production of renewable fuel besides being an important alternative for the farmer in rotation systems and crop sequence. Its wide adaptation to different climatic conditions makes of the sunflower a highly promissory crop for the Brazilian Northeast. Soil salinity is one of the main problems of irrigated agriculture and has reduced production in growing areas worldwide. One way to mitigate the effects of salinity on plants is to improve the nutritional quality of the soil. Due to the scarcity of information in this grad in the semiarid region, a study was conducted, under greenhouse conditions, to evaluate the growth and yield of Embrapa 122 / V-2000 sunflower variety under the influence of different water salinities and nitrogen fertilization. The factors studied were 5 salt salinity of irrigation water (0.5, 1.5, 2.5, 3.5 and 4.5 dS m-1) and five nitrogen doses (60, 80, 100, 120 and 140% of the recommended nitrogen for experiments in pots), combined in a 5 x 5 split plot experimental design with three blocks, with one plant per conducted. The plants were grown in 20 L pots, filled with a Entisol. The irrigations were automatically daily leaving the soil at field capacity. Growth variables (plant height, stem diameter, leaf area and phytomass), production variables (capitulum diameter, productivity, number and percentage of viable achenes) velocity of germination and water use by the sunflower were measured, and the results submitted to analysis of variance and regression for those which were significant. Sunflower reduced its growth and production at water salinity levels greater than 1.5 and 2.5 dS m-1, respectively. Nitrogen levels influenced only the total phytomas of achenes and non viable achenes and the percentage of viable achenes. Water consumption was affected much by salinity as by nitrogen, observing that the N doses which mitigated the effect of salt on the plant was equivalent to 100% of the recommended dose.