The Effect of Tobacco Monoculture and Crop Rotations on Tobacco Leaf Composition

This paper presents the long-term results relating to the influence of different crop rotations and tobacco monoculture upon the chemical composition of flue-cured tobacco leaf. As a key crop, tobacco is included in all crop rotations. Considering the obtained results in the particular year’s tobacco growing in monoculture or in crop rotation mainly had significant effect on nicotine content in tobacco leaf including a 10-year average. A similar trend was also determined for the content of proteins. The content of total nitrogen and reducing sugars was mainly affected significantly by crop rotation as regards the particular years. Calcium and potassium ratio was also unfavorable, although both of them were significantly influenced by crop rotation. The same is true for magnesium in the particular years

Utjecaj monokulture flue-cured duhana i različitih tipova plodoreda na gustoću populacije biljno-parazitskih nematoda

Phytosanitary function of crop rotation is a known fact, so one of the basic motives for this work was to investigate its influence on the population densities of plant-parasitic nematodes. Long-term experiments, which are still in progress, were set up on luvic semigley on multi-layered Pleistocene sands on the experimental field of the Tobacco Institute Zagreb at Pitomača. Along with tobacco monoculture, investigations also included seven different types of crop rotations. As key crop, tobacco is included in all crop rotations. Results obtained indicate that presence of the population of endoparasitic nematodes, genus Pratylenchus, was to some degree crop dependent. Tobacco does not seem to stimulate intensive occurrence of this nematode population. However, as soon as it is included into crop rotation, the number of nematodes increases particularly in crop rotations involving a larger number of rotation fields. Soybean and oil-seed rape favour the spread of Pratylenchus species. Still, no alarming incidence of nematodes belonging to this genus was recorded. Ectoparasitic nematodes involve genera Tylenchus, Tylenchorhynchus and, to some extent, Paratylenchus, while incidence of genera Helicotylenchus and Rotylenchus is negligible. Members of these genera are no dangerous pests for the crops studied, even more so as they mainly appeared in populations that are not noxious. The established opinion about the population of saprophagous nematodes being more dependent on the amount of soil organic matter than on the crop type was not convincingly confirmed in this research.Fitosanitetska funkcija plodoreda poznata je činjenica, pa je jedan od temeljnih povoda za ova istraživanja bio da se istraži njegov utjecaj na populaciju nekih rodova biljno-parazitskih nematoda. Višegodišnja istraživanja, koja se i dalje nastavljaju, provedena su na lesiviranom tlu na višeslojnim pleistocenskim pijescima na pokušalištu Duhanskog instituta Zagreb u Pitomači. U pokusu je, pored monokulture duhana, zastupljeno sedam različitih tipova plodoreda. Kao ključna kultura, duhan je zastupljen u svim plodoredima. Zastupljenost populacije endoparazitskih nematoda roda Pratylenchus do određenog stupnja ovisila je o usjevu. Duhan očito ne potiče jaču pojavu populacije nematoda ovog roda. No, čim se uključi u plodored broj se nematoda povećava, napose u plodoredima s većim brojem plodorednih polja. Soja i uljana repica pogoduju širenju Pratylenchus vrsta. Ipak, nematode ovog roda nisu se pojavile u zabrinjavajućem stupnju. Ectoparazitske nematode zastupljene su rodovima Tylenchus, Tylenchorhynchus i, donekle, Paratylenchus, a savim beznačajno rodovima Helicotylenchus i Rotylenchus. Pripadnici ovih rodova nisu opasni štetnici za istraživane kulture, tim više što su najčešće bili zastupljeni u populacijama koje nisu opasne. Uvriježeno mišljenje da je populacija saprofitskih nematoda ovisnija o količini organske tvari u tlu nego o vrsti usjeva nije u ovim istraživanjima uvjerljivo potvrđeno