evaluation of some agroecological characteristics of basil (ocimum basilicum l.) as affected by simultaneous application of water-saving superabsorbent hydrogel in soil and foliar application of humic acid under different irrigation intervals in a low inp

introduction: basil (ocimum basilicum l.) is an annual herbaceous plant that belongs to lamiaceae family. this plant is native of india country and other countries in south of asia. nowadays, the use of water superabsorbent polymers is increased in agriculture and their role in reducing the drought stress and increasing the crops production has been demonstrated in many researches. superabsorbent polymers can absorb lots of water and keep it in their structure and give it to plant under drought stress conditions (9). humic substances are a group of heterogeneous molecules that are bonded together by weak forces, therefore they have high chemical stability. humic acid comprise 65 to 80 percent of total soil organic matter (6). according to medicinal importance of basil and its roles in the food and pharmaceutical industries, beside the limited water resources and need to increase water use efficiency through using ecological inputs, this study designed and conducted aimed to evaluate agroecological characteristics of basil as affected by application of water-saving superabsorbent and humic acid under irrigation intervals. materials and methods: in order to evaluate the effects of different amounts of water-saving superabsorbent and foliar application of humic acid and irrigation intervals on some quantitative characteristics of basil (ocimum basilicum l.), a split strip plot experiment was conducted based on rcbd design with three replications at the research farm of ferdowsi university of mashhad, iran during growing season of 2012-13. experimental factors included three levels of water-saving superabsorbent (0, 40 and 80 kg ha-1) as the main plot factor, two levels of humic acid (0 and 3 kg ha-1) as the sub plot factor and two levels of irrigation interval (5 and 10 days) as the strip plot factor. studied traits were seed number and weight per plant, plant height, number of lateral branches per plant, seed yield, biological yield and harvest index. results and discussion: the results showed that interaction of superabsorbent and humic acid had a significant effect on seed yield (p≤ 0.05), as the highest seed yield (2638.8 kg ha-1) obtained from application of 40 kg ha-1 superabsorbent without humic acid. evaluation of the superabsorbent and irrigation intervals interaction revealed that in all levels of superabsorbent, dry matter yield under irrigation interval of 5 days was more than irrigation interval of 10 days, so that dry matter yield at irrigation interval of 5 days and 0, 40 and 80 kg ha-1 levels of superabsorbent increased 13, 50 and 17% compared to irrigation interval of 10 days, respectively. seed number per plant significantly was affected by interaction effects of humic acid and irrigation interval, so that in condition of using of humic acid in irrigation interval of 10 days, seed number per plant increased by 26% compared to control. the triple interaction of superabsorbent, humic acid and irrigation interval had significant effect on branch number per plant, as in irrigation interval of 5 days, in both conditions of application and no-application of humic acid, the highest branch number per plant observed in 40 kg ha-1 level of superabsorbent. in general, the combined use of 40 kg ha-1 water-saving superabsorbent and humic acid in different levels of irrigation, particularly under drought stress condition, while improved quantitative characteristics of basil, played an effective role in alleviation the devastating effects of drought stress. it seems that the appropriate level of water-saving superabsorbent (40 kg ha-1) increased morphological characteristics and seed yield of basil through the absorption of water (4) and improvement of soil physical characteristics. it seems that humic acid increased quantitative characteristics of basil by increasing activity of growth hormones such as auxin and improving nutrient uptake. in most of the studied traits, efficiency of humic acid improved in conditions of superabsorbent application and the plant could use the humic acid more efficient. conclusions: the cost of this study has been funded by research and technology deputy of ferdowsi university of mashhad, faculty of agriculture, the financial supports is appreciated.