IMPACT OF WINTER COVER CROPS AT WEED POPULATION IN ORGANIC POPCORN MAIZE (Zea mays everta Sturt.) PRODUCTION

Tijekom trogodišnjeg istraživanja (2008./09.-2011.) provedenog na lesiviranom tlu Istočne Hrvatske u blizini Valpova, istraživan je utjecaj ozimih pokrovnih usjeva na zakorovljenost u razdoblju između žetve soje do sjetve kukuruza kokičara (Zea mays everta Sturt.), zakorovljenost u usjevu kokičara, te rast, razvoj, prinos i komponente prinosa kukuruza kokičara. Pokus je proveden po načelu ekološkog uzgoja, a postavljen je kao potpuno randomizirani blok dizajn u četiri repeticije s 12 tretmana ozimih pokrovnih usjeva: N-kontrola bez pokrovnog usjeva, pojedinačni pokrovni usjevi: R-ozima raž, P-ozima pšenica, F-facelija, Sg-stočni grašak, Vic-ozima grahorica; te smjese ozimih pokrovnih usjeva RSg, RVic, PSg, PVic, FSg i FVic. Dominantne korovne vrste u provedenom istraživanju bile su: Matricaria chamomilla L. i Arabidopsis thaliana L. u ozimim pokrovnim usjevima, te Ambrosia artemisiifolia L., Chenopodium album L., Amaranthus retroflexus L., Echinochloa crus–galli (L.) PB. i Setaria glauca (L.) PB. u kukuruzu kokičaru. Najmanju zakorovljenost imale su smjese PSg, RVic i PVic, te pojedinačni pokrovni usjevi R, Vic i P sa statistički značajno manjim brojem korova u odnosu na kontrolu. Najprinosniji tretmani po ostvarenoj nadzemnoj masi bili su RVic, RSg, R i P. Vremenske prilike značajno su utjecale na zakorovljenost, a najveći broj korova utvrđen je u izrazito vlažnom razdoblju 2010. godine. Zakorovljenost u kukuruzu kokičaru u odnosu na kontrolu u prosjeku je bila značajno veća na tretmanu P, kod sklopa kukuruza kokičara nije bilo razlike, dok je visina kukuruza kokičara bila niža na tretmanima R i FVic. Najveći prinos kukuruza kokičara ostvaren je na smjesi PVic (2,5 t ha-1) u 2010. godini, dok je u prosjeku, u odnosu na kontrolu, prinos bio viši na tretmanima PVic i FVic. Tretman Sg rezultirao je najvećom prosječnom hektolitarskom masom i masom 1000 zrna kukuruza kokičara u odnosu na kontrolu. Smjese žitarica i leguminoza pokazale su se učinkovitije u suzbijanju korova u odnosu na pojedinačne pokrovne usjeve, a tretmani PSg, RVic i RSg mogu se preporučiti kao najučinkovitiji u suzbijanju zakorovljenosti.Three year research (2008/09-2011) at the lessive soil of the Eastern Croatia near town Valpovo has been conducted in order to establish the impact of winter cover crop treatments at weed population between soybean harvest and seeding of the popcorn maize (Zea mays everta Sturt.) crop, weed in popcorn maize crop, as well as growth, development, yield and yield components of the popcorn maize as the main crop. The research has been conducted in accordance with organic rules, and it has been set up as complete randomized block design in four repetitions with 12 cover crop treatments: N-control, no cover crop, single cover crops: R-winter rye, P-winter wheat, F-phacelia, Sg-fodder pea, Vic-hairy vetch; and cover crop mixtures: RSg, RVic, PSg, PVic, FSg and FVic. Dominant weed species determined in this trial were: Matricaria chamomilla L. and Arabidopsis thaliana L. found in winter cover crops, and Ambrosia artemisiifolia L., Chenopodium album L., Amaranthus retroflexus L., Echinochloa crus–galli (L.) PB. and Setaria glauca (L.) PB. in popcorn maize. The least weeded were cover crop mixtures PSg, RVic and PVic and single cover crops R, Vic and P, with significantly lower number of weed in comparison with the control. Treatments with the highest shoot production were RVic, RSg, R and P. Weather did influence significantly weedeness, especially in very moist period of the year 2010. The weedness in popcorn maize, in comparison with control, was higher at treatment P, main crop density was not affected by cover crop treatments, whereas height of the popcorn maize was lower at treatments R and FVic. The highest popcorn maize grain yield was recorded at PVic treatment in 2010 (2.5 t ha-1), whereas, in average, higher yields, in comparison with control, were recorded at PVic and FVic treatments. Treatment Sg had the highest average hectolitre weight and 1000 grains weight in comparison with control. The mixtures of cereals and legumes were proven to be more effective in weed suppresion in comparison with single cover crop treatments, whereas treatments PSg, RVic and RSg can be recommended as the most effective in weedness control