تأثیر مصرف پیش‌رویشی تعدادی از علف‌کش‌ها‌ی متداول بر روی جمعیت علف‌های‌هرز، خصوصیات رویشی، گل و بنه زعفران (Crocus sativus L.)

Intoduction: Saffron (Corocus sativus L.) as the most expensive crop has special position among export products of Iran. Currently, Iran is the biggest saffron producer and exporter in the world. Much of saffron in Iran produced in South and Razavi provinces (6). One of the problems in saffron production of these regions is weed control. Weed competing with saffron for water, nutrients, light cause reduction of product (3, 7). Among control methods of weed, use of herbicides is not common in saffron fields. The main reason is the evidences about herbicides damage. For example, Zare Hosseini et al (14) observed application of herbicides of Iodosulfuron methyl sodium + Mesosulfuron- methyl+ Mefenpyr-diethyl destroyed grasses and broadleaf, but it destroyed saffron plant too. Haloxyfop- R methyl ester damaged grasses, but decreased stigma yield. This study aimed to investigate the effect of pre-emergence herbicides on weed population changes; the performance characteristics of saffron and saffron corms were implemented.
Materials and Methods: An experiment was conducted in a 4-year saffron farm located in Shahn Abad village, Zaveh city in Khorasan Razavi province in 2011- 2012. It was in a completely randomized block design with eight treatments and three replications. The treatments included six pre-emergence herbicides including Metribuzin 70% WP (850 g.ha-1), Oxyfluorfen24% EC (1 l.ha-1), Ioxynil 22.5% EC (1.5 l.ha-1), Etalfluorelin 33.3%EC (3 l.ha-1), Trifluoralin 48%EC (2 l.ha-1) and Chloridazon 80 %WP (5 Kg.ha-1) + Desmedipham 15.7% EC (5 l.ha-1) along with weed free and weedy check. Herbicides applied after irrigation simultaneously with crust breaking. The measurement characteristics included the number of flowers, fresh and dry weight of flower and stigma, leaf dry weight, leaf length, corm number and weight of saffron, weed type and wet and dry weight of dominant weeds. Herbicide treatments after irrigation were performed simultaneously with Crust breaking in 03/11/2011. The flowers gathering were conducted in 03/11/2011. Sampling of weed was performed in two stages in 04/18/2011 and 05/05/2012. In the first stage adding to the collection weed, leaves of saffron are also collected and the length of them were measured. In the second phase, when corm growth was stopped, they were gather, count, weight, and divide by weight. Corms into 4 groups: 0 to 3 g, 3 to 6 g, 6 to 9 grams and 9 grams were divided up. The traits were analyzed by using software programs Mstat-c. Mean comparison carried out with Duncan test with 5% probability.
Result and Discussion: The results showed that between herbicide treatments the highest number of flower (16.76 per m-2) and dry weight of stigma (75.67 mg per m-2) was belonged to Metribuzin treatment. The least flowers number (10.76 per m-2) and dry weight of stigma (13.67 mg per m-2) were observed in Etalfluorelin treatment. However there weren’t significant difference between Etalfluorelin and Trifluoralin for these traits. In the first stage of weed sampling were only narrow leaf weeds. In the second stage sampling was 7 species, 3 species of narrow-leaf and broadleaf species was 4. Most of the narrow leaf weed species were ovate goatgrass (Aegilopsgeni culata Roth.). Most broadleaf species belong to maltese star thistle (Centaurea melitensis L.). In the first stage of sampling Metribuzin and Chloridazone+ Desmedipham herbicides had the highest effect in narrow leaf weed control, respectively. Ioxynil had the least impact on this stage. In the second stage of sampling, the highest and lowest control of maltese star thistlewas observed in Chloridazone+ Desmedipham and Ioxynil respectively. Chloridazone+ Desmedipham and Metribuzin had the greatest impact onovate goatgrass and other herbicides for control of these species were not significantly different. Minimal impact on the total corm weight was observed in Metribuzin and Etalfluorelin respectively. The most reduction of corm weight was observed in Chloridazone + Desmedipham treatments. Amiri et al (4) reported that Metribuzin application before and after the weed eruption is appropriate for broadleaves and somewhat narrow-leaves control. None of the treatments had adverse effects on corm weight producing with 0-3, 6-9 and above 9 grams but 3-6 grams weight of corm was affected. In producing corms with 3 to 6 grams weight the least adverse effect was observed in Metribuzin. The most adverse effect after no weeding treatment in producing corms with 3 to 6 grams weight was belonged to Chloridazone + Desmedipham.
Conclusion:. On the basis of results, it seems to be due to the least amount of damage to saffron and its corm and the most control of broadleaf and to some extent narrow- leaf weed, the application of 850 grams.ha-1 pre-emergence herbicide Metribuzin is suitable for saffron weed control.