VOL. 10, NO. 7, JULY 2015 ISSN 1990-6145 ARPN Journal of Agricultural and Biological Science © 2006-2015 Asian Research Publishing Network (ARPN). All rights reserved. www.arpnjournals.com 247 EFFECT OF HUMIC ACID AND SULFUR ON GROWTH, SOME BIOCHEMICAL CONSTITUENTS, YIELD AND YIELD ATTRIBUTES OF FLAX GROWN UNDER NEWLY RECLAIMED SANDY SOILS Bakry A. B. 1 , Mervat Sh. Sadak 2 and El-karamany M. F. 1 Field Crops Research Department, National Research Centre, Dokki, Giza, Egypt 2 Department of Botany, National Research Centre, Dokki, Giza, Egypt E-Mail: bakry_ahmed2004@yahoo.com ABSTRACT A field experiment was carried out at the experimental Station of National Research Centre, Al Nubaria district, El-Behira Governorate-Egypt, in 2013/2014 and 2014/2015 winter seasons to investigate the influence of three sulfur fertilizer levels and/or foliar humic acid on some morphological and biochemical parameters as well as yield quantity and quality of flax plant grown under newly reclaimed sandy soil conditions. Results indicated that, humic acid foliar treatment with 20 (mg/l) in addition to sulfur fertilizer at rate of (250 and 500 kg/fed) gave significant increases in seed, straw and oil yield / fed. These increases due to the recorded increases in morphological criteria (plant height and root length, fresh and dry weight of shoot and root), photosynthetic pigments, (chlorophyll a, chlorophyll b and carotenoids), carbohydrate constituents (total carbohydrates, total soluble sugars and polysaccharides), IAA, phenol, free amino acids and proline contents. Meanwhile, lipid peroxidation decreased significantly in response to the above mentioned treatment as compared with control plants. Interaction between humic acid (20 cm/L) with sulfur at rate of (500 kg/fed) was the most effective treatment as it gave the highest increases in all morphological criteria, biochemical parameters, yield and yield attributes compared with the other treatments. Humic acid and sulfur fertilizer at all levels caused marked decreases in total saturated fatty acids accompanied by marked increases in total unsaturated fatty acids. The essential fatty acids (Linoleic acid C 18:2 + Linolenic acid C18:3) were increased by all applied treatments. It is worthy to mention that, the enhancement effects of humic acid (20 mg/l) and sulfur fertilizer (500 kg/fed) were the most pronounced treatment on flax plant. Keywords: fatty acid, flax, humic acid, lipid peroxidation, sulfur fertilizer, yields. INTRODUCTION Flax (Linum usitatissimum L.) is a source of two products; flax seed for oil and fiber for linen products. In Egypt, it is an old economic crop grown as a dual purpose crop for seeds and fibers which is used for the manufacture of linen. Linseed contains 30-48 % of oil abundant in unsaturated fatty acids, especially α-linolenic acid (40-68 %), where technical purity can reach 95%. Linseed oil-chemical industry in drying oil (for the production of printing and other inks, varnishes, paints and linoleum). Environmental pollution due to excessive application of chemical fertilizer such as nitrogen fertilizer to agricultural lands, surface waters and groundwater is one of the most important environmental and social concerns throughout the world especially in developing countries (Parr et al., 1992). Soil organic matter has beneficial effects on soil quality and positive effects on crop productivity and also has the potential to sequester carbon. In addition, organic matters could reduce the application of industrial fertilizers in long term (Rasmussen and Parton, 1994). Humic acid (HA) is one of the main organic substances, which is an important component of humic substances. Humic acid is complex substances derived from organic matter decomposition. Humic acid are the most significant constituents of organic matter in both soils and municipal waste compost, and have a relevant role in the cycling of many elements in the environment and in soil ecological functions (Senesi et al., 1996). According to previous investigations, humic seem to have a particular favorable effect on the nutrient supply. Foliar sprays of these substances also promote growth, and increase yield and quality in a number of plant species (Karakurt et al., 2009) at least partially through increasing nutrient uptake, serving as a source of mineral plant nutrients and regulator of their release (Atiyeh, et al., 2002). Moreover, humic acid influence respiration- process, the amount of sugars, amino acids and nitrate accumulated (Boehme et al., 2005). Sulfur (S) is an essential macroelement for plant nutrition, but its concentration in plants is the lowest of all the macronutrients. Sulfur is increasingly being recognized as the fourth major essential nutrient element after nitrogen (N), phosphorus (P), and potassium (K). Plants are able to assimilate sulfate and reduce it to essential amino acids, where S is involved in a range of metabolic functions, including protein synthesis. Greater attention needs to be paid to the role of S in balanced crop nutrition. Sulfur plays an important role not only in the growth and development of higher plants, but is also associated with increased stress tolerance in plants (Nazar, et al., 2011 and Osman and Rady, 2012). S deficiency negatively affects the chlorophyll and N contents of leaves and photosynthetic enzymes (Lunde, et al., 2008), and consequently the reduction in yields and quality parameters of crops (Hawkesford, 2000 and Osman and Rady, 2012). Adequate S nutrition improves photosynthesis and the growth of plants, and has