Reducing the Effects of Water Stress using Vermicompost and Mineral Zeolite in Sunflower (Helianthus annus L.)

IntroductionThe population of developing countries is dramatically increasing, thus acute food supply challenges are threatening them in case of quality and quantity. One of the successful strategies for improving agricultural production and food supply is to preserve, maintain, and enrich the soil .Iran has an arid and semi-arid climate with an average rainfall of 240 mm per year, so improving water use efficiency and reducing the effects of water stress can help farmers increase their agricultural products. Another serious problem of Iranian agricultural system is the widespread application of chemical fertilizers in the recent decades, which has caused soil degradation and environmental pollution. Therefore, by addressing these two concerns, this research was to evaluate the possibility of reducing the unpleasant effects of water stress on sunflower using organic fertilizers of Vermicompost and Mineral Zeolite (Clinoptilolite).
Materials and methodsThis study was conducted at the agricultural research farm of Tarbiat Modares University in Tehran, Iran (lattitude: 35° 44´N and longitude: 51° 10´E) during the growing season of 2010 to 2011. The factorial arrangement was done on Randomized complete block design (RCBD) with three replications. The main-plot factors were different nutritional systems, such as, F1(0% vermicompost 100% chemical (urea) 175% zeolite), F2 (25% vermicompost 75% chemical (urea) 150% zeolite), F3(50% vermicompost 50% chemical (urea) 125% zeolite), F4(75% vermicompost 25% chemical 100% zeolite); and sub-plot factors were deficit irrigation at three levels including control treatment (S1): 50% moisture depletion/moisture content (or, 50% FC), (S2): 60% moisture content (or, 40% FC) and (S3): 70% moisture content (or, 30% FC).
All the experimental plots were irrigated equally until the R4 phase. Irrigation regimes was set after R4 based on soil moisture reduction measured with a TDR device models trime_FM, and for more accurate results, a gravimetric soil moisture was used too. Chlorophyll extraction was performed by Arnon's (1949) standard method and was read with a spectrophotometer model (GBC-Cintra 6- Australia), at wavelengths of 663 and 645 nm. The proline content was extracted with Bate's (1973) method and was read with a spectrophotometer at a wavelength of 520 nm. The protein content was measured using the standard Kjeldahl (1883) method. Also, seed oil content was measured using Soxhlet (Model No SCMS-F100-6H), and oil yield was calculated by multiplying the seed oil content in grain yield. Data were recorded in Microsoft Excel ver. 2010 and statistical analysis was done with SAS ver. 9.1 software. Means compared using LSD at the 1% probability level.
Results and DiscussionANOVA (Analysis of Variance) results showed that the effect of stress/deficit irrigation, nutritional systems and their interactions were significant (P