Kritično vreme suzbijanja korova u usevu kukuruza pri standardnoj i setvi u duple redove

Abstract

Interakcija između korova i useva je vrlo dinamična, permanentna i kompleksna pojava. Korovi i gajene biljke se „takmiče“ za životni prostor i prirodne resurse neophodne za normalana rast i razvoj biljaka. Generalno, korovi su jači kompetitori od gajenih biljaka zbog njihove izraženije eurivalentnosti i prilagodljivosti na različite i promenjive uslove životne sredine. Stoga je veoma važno stvoriti takve uslove u agrofitocenozama kako bi usevi bili u kompetitivnoj prednosti u odnosu na korove. To se između ostalog može postići i optimalnom normom setve useva i pravoveremenim suzbijanjem korova. Za pravoveremeno suzbijanje korova veoma važno je poznavanje kritičnog perioda u razvoju useva kada on mora biti oslobođen od korova, a to predstavlja ključnu kariku u uspostavljanju sistema integralne zaštite useva od korova. Polazeći od značaja kukuruza, problema do kojih se može doći pri različitim uslovima njegovog gajenja, agroekoloških prilika, različitih sistema setve, nivoa zakorovljenosti i šteta od korova programom ove disertacije predviđeno je da se definiše kritično vreme suzbijanja korova (KVSK) u dva sistema setve kukuruza. U periodu 2015-2017. godine na području Padine (Južni Banat) su izvedeni eksperimenti po principu split-split plot modela, sa dve glavne parcele: SS - standardna setva (setvena norma 80.000 biljaka ha-1) i SDR – setva duplih redova (setvena norma 93.900 biljaka ha-1). Svaka glavna parcela bila je podeljena na dve potparcele (bez i sa pre-em primenom herbicida: 1,44 kg ha-¹ S-metalohlora + 0,75 kg ha-¹ terbutilazina) koja se sastojala od pet vremena uklanjanja korova (T2-T6 tj. BBCH 13-16-19-34-53) i dve kontrole (T1- zakorovljena i T7- nezakorovljena). Za definisanje KVSK proučavani su parametri: vrsta, brojnost i suva masa korova m-2; visina, suva masa kukuruza, prinos zrna i komponente prinosa (dužina klipa, broj zrna u klipu i masa 1.000 zrna). Za statističku analizu korišćen je softver R i "drc" paket. Svi mereni vegetativni i generativni parametri korova i useva su se značajno razlikovali između godina u oba sistema setve kukuruza, vremena ukljanjanja korova u varijantama sa i bez pre-em primene herbicida. Najmanje vrednosti svih parametara su utvrđene u vegetacionoj sezoni sa deficitom padavina (281,1 mmmm) a najveće u sezoni sa optimalnom količinom padavina (526,4 mm) osim redukcije prinosa kukuruza gde je to bilo obrnuto. U sve tri sezone u svim tretmanima najbrojnije su bile sledeće korovske vrste: Amaranthus retroflexus, Chenopodium album, Helianthus annuus, Datura stramonium, Cirsium arvense, Solanum nigrum i Sorghum halepense. U suvljoj sezoni (281,1 mm) KVSK u SS u varijanti sa pre-em primenom herbicida je nastupilo u fazi kukuruza BBCH 14 (26 DPN), a bez primene herbicida u fazi BBCH 12 (21 DPN). U istoj sezoni u SDR i varijanti sa pre-em tretmanom KVSK je nastupilo u BBCH 13 (22 DPN), a bez primene herbicida u fazi BBCH 12 (18 DPN). U vegetacionoj sezoni sa 336,0 mm kiše u SS i varijanti sa pre-em tretmanom KVSK je nastupilo kada je kukuruz bio u fazi BBCH 15 (36 DPN), a bez primene herbicida u BBCH 11 (16 DPN). U istoj sezoni KVSK u SDR i varijanti sa pre-em tretmanom je nastupilo u fazi BBCH 16 (41 DPN), a bez primene herbicida u BBCH 12 (19 DPN)...

The interaction between weeds and crops is a dynamic process of competition for living space and natural resources necessary for normal plant growth and development. It is well known that weeds are strong competitors due to their ability to adapt to changing environmens. Therefore, it is very important to create such conditions in agrophytocenoses so that the crops have a competitive advantage over weeds. This can be achieved among other things, by the optimal planting rate of crops and timely weed control. For timely weed control, it is very important to know the critical period in crop development when it must be free of weeds, and this is a key link in establishing a system of integrated crop protection against weeds. Considering many variables that can impact corn growth and develepment, problems that can occur under different growing conditions, agroecological conditions, different sowing systems, weed levels and weed damage, the objective of this dissertation project was to define the critical time for weed removal (CTWR) in two corn planting systems. In the period from 2015 to 2017, in area of Padina (South Banat district) experiments were conducted in a split-split plot design, with two main plots: SS-standard sowing (planting rate of 80,000 plants ha-1) and SDR - sowing of double rows (planting rate of 93,900 plants ha-1). Each main plot was divided into two subplots, (without and with PRE-EM herbicide: 1.44 kg ha-¹ S-metallochlor + 0.75 kg ha-¹ terbuthylazine) which further consisted of five weed removal timings (T2 - T6 i.e. BBCH 13-16-19-34-53) and two controls (T1- weeded and T7- weedfree). To define the CTWR, the following parameters were studied: weed species composition, number and dry mass of weeds m -2; height, dry weight of maize, grain yield and yield components (cob length, number of grains in the cob and weight of 1.000 grains). The R software and the "drc" package were used for statistical analysis. Growth parameters of weeds and crops differed significantly between years in both planting systems as influenced by the amount of rainfall between the season. The lowest values of all growth parameters were determined in the season with a deficit of precipitation (281.1 mm), while the highest in the season with an optimal amount of precipitation (526.4 mm) except for the reduction in maize yield, where it was the other way around. In all three seasons, the following weed species dominated in all treatments: Amaranthus retroflexus, Chenopodium album, Helianthus annuus, Datura stramonium, Cirsium arvense, Solanum nigrum i Sorghum halepense. In the drier season (281.1 mm) CTWR in SS with PRE herbicide occurred in the corn stage BBCH 14 (26 DAE), and without PRE herbicide it was at earlier stage, BBCH 12 stage (21 DAE). In the same season in SDR with PRE treatment CTWR was similar to SS, at BBCH 13 stage (22 DAE), and without PRE herbicide at BBCH 12 (18 DAE). In the wetter season (526.4 mm) CTWR in SS with PRE herbicide was at BBCH 20 stage (58 DAE), and without PRE herbicides at much earlier stage, ie. BBCH 11 (16 DAE). In the SDR system with PRE VIII herbicide, the CTWR occurred at the latest, ie. BBCH 21 (61 DAE) and without herbicide at 41 days earlier (BBCH 12, i.e. 20 DAE)...