Utjecaj roka žetve na prinos kineskog šaša (Miscanthus x giganteus)

Miscanthus x giganteus (miskantus) je višegodišnja C4 travna vrsta s odlikama koje ju svrstavaju u obećavajuće kulture za proizvodnju krutih i tekućih biogoriva. Posjeduje visok proizvodni potencijal i ekološki je vrlo prihvatljiva vrsta jer uspješno raste uz vrlo male količine pesticida i gnojiva. Miskantus se žanje u jesen, zimi i u proljeće. Najveći prinosi postižu se u jesen, dok kasniji rokovi žetve rezultiraju nižim prinosima, ali kvalitetnijom masom za izgaranje. U kasnijim rokovima žetve dolazi do prirodnog sušenja biljaka u polju, čime se ostvaruju znatne uštede energije kod dosušivanja. Cilj rada je bio utvrditi prinos biomase energetske trave Miscanthus x giganteus uzgajane na dvije lokacije (nizinsko i planinsko područje) u tri različita roka žetve. Pokusna polja miskantusa postavljena su na 2 lokacije: Centar za travnjaštvo Agronomskog fakulteta na Medvednici te u Donjoj Bistri. Reznice rizoma miskantusa posađene su početkom svibnja 2011. Pokusi su postavljeni po shemi slučajnog bloknog rasporeda u 3 ponavljanja u trećoj godini uzgoja miskantusa (2013. godine). Rokovi žetve miskantusa bili su: a) jesenski - na kraju vegetacijske sezone 2013., b) zimski - sredinom zime 2014. godine i c) proljetni - neposredno prije kretanja vegetacije miskantusa 2014. godine. Ručnim odsijecanjem biljaka na 4 m2, na visinu 5 cm od tla i vaganjem požnjevene mase utvrđen je prinos zelene mase. Sušenjem poduzoraka cca. 1000 g sasjeckane mase 48 sati na 60 °C, ponovnim vaganjem i preračunavanjem u t ha-1 utvrđen je prinos suhe tvari (ST). Prosječni prinos ST sva tri roka žetve u Donjoj Bistri (22,25 t ha-1) bio je za 12,4 % veći od prosječnog prinosa na Medvednici (19,80 t ha-1) zahvaljujući manjem nedostatku i ravnomjernijem rasporedu oborina na ovoj lokaciji u vegetacijskom dijelu godine u odnosu na Medvednicu. U jesenskom roku žetve postignut je najveći prinos ST miskantusa (27,59 t ha-1). Bio je za 33,7% veći od prinosa ST zimskog roka žetve (20,63 t ha-1) i 85,4% veći od proljetnog prinosa ST (14,88 t ha-1). Zimski prinos ST bio je za 38,6% veći od proljetnog prinosa ST biomase miskantusa. Razlike u prinosu ST među lokacijama postojale su samo u jesenskom roku žetve, dok u ostala dva roka nisu zabilježene (signifikantna interakcija lokacija x rok žetve).Miscanthus x giganteus (Miscanthus) is a perennial C4 grass species with features that classify it as a promising species for the production of solid and liquid biofuels. It has a high production potential and it is very environmentally friendly as it can grow successfully with very small amounts of pesticides and fertilizers. Miscanthus is harvested in the fall, winter and spring. The highest yields are obtained in the autumn, while the later harvest dates result in lower yields, but higher quality combustion mass. In the later harvest dates, it comes to natural drying of plants in the field, which brings significant savings of energy used for grain drying. The objective of the study is to determine the biomass yield of bioenergy grass Miscanthus x giganteus grown in two locations (lowland and mountainous area) in three different harvest dates. Experimental fields of miscanthus were set in 2 locations: Center for Grassland of Faculty of Agriculture on Medvednica and Donja Bistra. Miscanthus rhizomes cuttings were planted in early May 2011. Experiments were conducted using randomized complete block design in 3 repetitions, in the third cultivation year (year 2013.). Miscanthus harvest dates were: a) autumn – at the end of the growing season 2013., b) winter - mid winter 2014. and c) spring - immediately before the vegetation movement of miscanthus 2014. The yield of the green mass was determined by manually cutting off the plants at the area of 4 m2, at the height of 5 cm from the ground and weighing harvested mass. The yield of dry matter (DM) was determined by drying of sub-samples of approximately 1000 g minced mass for 48 hours at 60°C, re-weighing and conversion to t ha-1. The average DM yeld of all three harvest dates in Donja Bistra (22,25 t ha-1) was 12,4% higher than the average yield on Medvednica (19,80 t ha-1), due to the miner absence and more equal distribution of percipitation at this location in the vegetation period of the year compared to Medvednica. The highest DM yield of Miscanthus was obtained in the autumn harvest date (27,59 t ha-1). It was 33,7% higher than the DM yield from winter harvest date (20,63 t ha-1) and 85,4% higher than DM yield from spring harvest date (14,88 t ha-1). DM yield from winter harvest date was 38,6% higher then the spring harvest date DM yield of Miscanthus. There were differences in DM yield between locations only in the autumn harvest date, while the differences between the other two harvest dates were not registered (significant interaction location x harvest date)