The response of quantitative and qualitative traits of sunflower seed to various nitrogen sources (organic and chemical fertilizers) and zeolite under different regimes of irrigation

Introduction The sunflower (Helianthus annuus L.) is one of the most important oil-producing plants in the world. Innovative strategies are needed to improve water and nutrient use efficiencies for sustainable production in sandy soils. In recent years, there has been an increasing demand for agricultural products with specific qualities. Oil seeds are the most important sources of energy for human demand following cereals. During recent decades, Cultivation area of sunflower as a main oilseed crop considerably increased due to its short growth season, high oil yield and also its nutritional value. Unsaturated fatty acids such as Oleic, Linoleic acids include about 90% of sunflower oil. Evaluation of different nutrient sources to achieve more drought tolerance in sunflower is vital to achieve high quantity and quality yield. Oil quality and yield are both dependent upon the genotype of a plant and its interaction with the environment. Among the factors responsible for increasing crop yield and quality, irrigation and fertilizer are the most important. Materials and methods In order to evaluate the response of sunflower quantitative and qualitative yield to various nitrogen sources and zeolite under different irrigation regimes, a two-year study was carried out as split-factorial based on RCBD at Agricultural Research Faculty of Tarbiat Modares University in 2015 and 2016. Irrigation regimes including (irrigation after depleting 40, 60, 80% of available soil water (ASW), was considered as main plot while the combinations of the nitrogen sources (providing 100% of required N through manure farmyard, 50% farm yard+ 50% urea, 100% of required N through urea) and zeolite (0, 5 10 t ha-1) were regarded as subplot. Results and discussion The results showed the highest stem diameter and height in the first (respectively 2/2 mm and 186.7 cm) and second (respectively 2.26 mm and 168.3 cm) years were achieved by using zeolite and irrigation after depleting 40% of ASW. In addition, the highest grain oil and protein yield in second year were obtained by irrigation after depleting 40% of ASW accompanied with using zeolite. Water stress caused significant decline in unsaturated fatty acids including oleic, linoleic, stearic acids (respectively 22 and 7, 50 % in the first and 27, 6.8 and 52 % in the second year) while palmetic acid increased under water stress by 54.6 and 65.3% in the first and second years. Farmyard manure positively affected oil quality in sequential years through higher accumulation of oleic (by 9.2 and 9.7%), linoleic acids (by 7.8 and 8.2%) under water stress conditions. Conclusions The result showed that under well irrigated conditions using manure farmyard and under water stress manure farmyard accompanied with zeolite, led to the best results in terms of quantitative and qualitative yield. In general, zeolite application and farmyard manure could alleviate water stress adverse effects, and improved plant growth, yield and oil and protein concentration. Overall, using manure farmyard plus zeolite might be considered as agronomic approach to decrease chemical fertilizer application rates and improve the sustainability of agricultural systems especially when the sunflower plants were subjected to water shortage conditions.