EFFECTS OF FUNGICIDES ON ALFALFA SEED YIELD

Alfalfa is the most seeded forage crop in the Republic of Croatia.The seed requirements are estimated at 250-300 thousand kg each year. Despite the relatively suitable management, favourable environmental conditions and numerously recognized national cultivars the state seed production is insufficient and more than 70% of seed requirements are compensated by import. The research of a fungicides efficiency on alfalfa seed yield components (plant height, branch number, number of seeds per pod, number and weight of pods per stem, number and weight of seeds per stem, weight of 1000 seeds) has been carried out during 1994 and 1995 in Osijek. It involved application of two fungicides (both of them without a state alfalfa application licence): Impact C (flutriafol+carbendazim) and Tilt 250 EC (propiconazol) on alfalfa second growth seed stands in a different phenological stages of alfalfa development. The experiment was established at two three year old alfalfa stands of cultivar Osječka 66 sown in thick rows (0.12 m row spacing) and wide rows (0.5m row spacing). The experimental design was split-plot with four replicates. The plot size was 25 m2 . The fungicide application variants were as follows: 1.non treated; 2. at the beginning of a flowering stage; 3. in a full flowering stage; 4.at the end of a flowering stage; 5. as a combination of 2+4; and 6.as a combination 3+4 in a dose: Impact C 0.5 l/ha / 400 l of water and Tilt 250 EC 1 l/ha / 400 l of water. A control of the seed stands health during the vegetation confirmed the presence of disease agents: Phoma medicaginis, Stemphylium botryosum, Pseudopeziza medicaginis and Uromyces striatus. The results of the investigation indicate that applied fungicides did not significantly affect alfalfa seed yield. The total average seed yield in 1994 was 323 kg/ha and in 1995 213 kg/ha. In 1994 the seed yield on fungicide application variant 2 was 381.88 kg/ha and it was by 35% higher than on variant 3 and by 23% higher than on variant 4. In that year of the investigation the highest seed yielding variant was variant 2 in a wide row sown stand (456.3 kg/ha). It was by 48.4% higher than the same variant in a thick row sown stand (307.5 kg/ha) and by 27,5% higher than variant 1 (357.85 kg/ha). Also variant 2 had the highest number of seeds per pod and lowest height of plants in 1994 and the highest number and weight of pods in 1995. Both fungicides had significant effect (P<0.01) on weight of 1000 seeds in 1995. Row space didn't significantly influence seed yield in 1994, but it significantly affecteded it in 1995 (P<0.05). The higher yield had a thick row sown stand. During the two year sinvestigations wide rows sown stand had by 13.8% grater height of plants, by 31.2% larger number of branches, by 15.1% higher weight of seeds and by 7% larger number of pods and seeds per stem, but it hadn't higher seed yield mostly because unfavourable environmental conditions. Concerning results and new knowledge it is recommendable to continue the investigations and to check up an economic return of fungicides application in alfalfa seed stands.