SUMMARY OF PhD THESIS CONTRIBUTIONS TO THE IMPROVEMENT OF POST-EMERGENT WEED CONTROL SYSTEM IN CORN CROP

Transcription

1 UNIVERSITY OF AGRICULTURAL SCIENCES AND VETERINARY MEDICINE CLUJ-NAPOCA DOCTORAL SCHOOL FACULTATY OF AGRICULTURE Ing. GEORGE - CĂLIN ROIBAN SUMMARY OF PhD THESIS CONTRIBUTIONS TO THE IMPROVEMENT OF POST-EMERGENT WEED CONTROL SYSTEM IN CORN CROP Scientific coordinator Prof. univ. dr. ing. PETRU GUŞ CLUJ-NAPOCA

2 CONTRIBUTIONS TO THE IMPROVEMENT OF POST-EMERGENT WEED CONTROL SYSTEM IN CORN CROP As agriculture developed, the weed categories continuously diversify and adapted to new conditions of agricultural technique. The result of these permanent adjustments is observed today in the great survival capacity of weeds, and in the dynamic within certain species communities; this dynamic is put in evidence by more adapted biotypes, by the continuous modification of quantitative and qualitative structure of weeding, by including new species from spontaneous local flora or from other geographical areas. Having as pre-requisite the efficient control of weed, we consider very necessary the knowledge of all elements part of the process. Corn, as the main cultivated plant in the Transylvanian agriculture exploitations, remains a preoccupation of scientists to permanently improve the culture technologies or adapt the technology to the modifications occurred in the corn crop habitat, in the specific machinery system or in the economic interests of this crop. The corn particular sensitivity to weeding is an open field for herbology research and for the study of corn crop weed control, in order to find the adequate solutions for every homogenous ecological area, solutions that will give the effective answer to reduce the weeding under the damaging level and to farmers economic effort. The new obligations imposed by the European legislation in the field of environment protection, certified by the modern techniques of plant protections, justify the selection of the research theme for the PhD thesis, due to the following aspects: corn crop is still one of the main agriculture crops at national, European and world wide level; crop sensitivity to weeding enforces the weed control by effective and rapid methods; elimination of numerous herbicidal active substances with pre-emergent application from the approved for use list; ecological impact with low risk in the case of post-emergent chemical control; 1

3 Possibility of combining the post-emergent methods for weed control with indirect preventive or agrotechnical methods in order to obtain an integrated system for weed control in corn crop, economically and ecologically efficient. Because the corn crop is cultivated on a very wide surface in different pedo-climatic areas, the weed infestation differs very much in the country. Variations are bigger if we observe the ratio of certain weed species towards other, the monocotyledonated species towards the dicotyledonated, the annual towards the perennial etc.; thus, the selection of the right strategy for weed control has to be made in the real local conditions. From the considerations that: the characteristic weed flora for corn is variable in the territory; the climatic conditions are variable as well; the herbicide effect can vary is related to their adequate selection, their application technique and the weather; safety of the agro-ecosystem, animal and human health are also variable, in relation to many natural and anthropic factors, among other things being the right approach of weed control methods in the agriculture crops; the profit of corn crop farmers varies depending on the fact that the technological steps of crop are correctly applied and on the local conditions By the research carried out for this thesis, I envisage to clarify certain aspects concerning the specificity of corn crop weeding in Alba County (commune of Noşlac), the efficacy of the post-emergence weed control strategies for corn crop, the selectivity of chemical recipes for corn crop cultivated in this area and the preservation of ecological balance. 2

4 THE PURPOSE OF THE RESEARCH The main purpose of the research studies is: to elaborate the strategies for postemergent weed control in corn crop, which are optimal from technological, economical and ecological point of view, for the high meadow area of Alba County. In order to achieve this goal, there is necessary to cover three essential steps, every one with their own specific scientific and applicative objectives. These three steps are determined by the three components needed to making efficient the results of post-emergent weed control in corn crop and the applicability of those results to extension in agriculture production of the area. Thus, the research made during is framed in the following three stages: Establishing the competition between weed and corn plants in the specific experimental conditions; Elaboration the strategies of post-emergence weed control for corn crop in high meadow areas from Alba county; Setting the minimal elements for research extension THE OBJECTIVES OF THE RESEARCH The first stage of the research studies - establishing the competition between weed and corn plants in the experimental conditions of Noşlac envisage the following study objectives: Inventory of weeding degree of corn crop from Noşlac area, Alba County. Establishing the problem: weed species for this crop culture; Establishing the correlations between the weeding level of the area crop culture and the production; Establishing the correlations between the weeding level of the crop culture and climate factors of the research years; Establishing the fluctuation of weeding level during the 4 research years; 3

5 The second stage of the research studies - elaboration the strategies of postemergence weed control for corn crop in high meadow areas from Alba County - envisages the following study objectives: Stating the basic elements for elaboration of the strategies of post-emergence weed control Testing certain chemical and mixed strategies of post-emergence weed control for corn crop; Elaboration of strategies of post-emergence weed control for corn crop in high meadow areas from Alba county, optimal from technological, economical and ecological point if view The third stage of the research studies - setting the minimal elements for research extension - envisages the following study objectives: Establishing the economic efficiency of weed control technology with associated herbicides single treatment; Establishing the economic efficiency of weed control technology with associated herbicides two treatments; Establishing the economic efficiency of weed control technology with associated herbicides single treatment + mechanical hoeing Establishing the economic efficiency of weed control technology with total herbicides applied in triticale crop stubble field + single post-emergent treatment with associated or complex herbicides. 4

6 THE EXPERIMENTAL DEVICE The researches on improving the strategies for post-emergence weed control in corn crop developed in a 4 years period: , in a private property field of Noşlac commune, Alba County, within the framework of bifactorial stationary experiments, settled after the randomized blocks method, with 28 variants in four repetitions. The total area surface was 30 sq meters. The experimental factors and their graduations are: A. Weed control method: 28 graduations grouped in 4 control technologies and 2 witnesses: a 1 = classical weed control, 3 manual hoeing control variant no 1 a 2 = no weed control control variant no 2 a 3 a 10 = chemical weed control, single post-emergence treatment with associated herbicide a 11 a 16 = chemical weed control, 2 post-emergence treatments with fractioned dosage: an early first one (2-3 corn leaves); the second one at 5-6 corn leaves stage a 17 a 22 = mixed weed control, early treatment (2-3 corn leaves) with associated or complex herbicides, followed by mechanical hoeing, a 23 a 28 = 2 years chemical weed control, treatment with total herbicides in triticale stubble field + single treatment with associated herbicides at 5-6 corn leaves stage. B. Experimental years: 4 graduations, b 1 = 2004 b 2 = 2005 b 3 = 2006 b 4 = 2007 In order to establish the efficacy in post-emergence weed control, 11 herbicide products were tested, having different active substances: foramsulfuron + isoxadifen ethyl, 5

7 rimsulfuron, mesotrione, prosulfuron + primsulphuron, 2.4D acid + MCPA+ clopyralid, bromoxynil + 2.4D (ester), florasulam+ 2,4 D (EHE), bromoxynil octanoate. The corn cultivation technology in the experimental field comprises: 3 years crop rotation: autumn triticale corn potato + sugar beet + vegetables (fig. 1); Differentiated working system function of applied weed control variants, as follows: o For the 4 treatment variants in previous crop stubble field: triticale harvest (last decade of July) - stubble field herbicide application on all area, with LEONE 36 SL: 4 l/ ha, 14 days after harvesting (30 t/ha manure applied in the second decade of September, in 2003 rotation 2 and 3 - and in 2004 rotation 2) autumn ploughing at 25 cm depth, in the last decade of September or first decade of October single rotary harrow passing o For the 4 treatment variants in previous crop stubble field: triticale harvest (last decade of July) - stubble field herbicide application all over the area, with LEONE 36 SL: 4 l/ ha, 14 days after harvesting (30 t/ha manure applied in the second decade of September, in 2003 rotation 2 and 3 - and in 2004 rotation 2) - autumn ploughing at 25 cm depth, in the last decade of September or first decade of October single rotary harrow passing GDU 3,4 (second decade of April) complex fertilisation starter fertilisation Cu N 40 P 40 single seedbed combination passing in the seeding day (third decade of April) seeded with SPC 6 post-emergence herbicide application + first foliar fertilisation (stage 5-6 corn leaves) second foliar fertilisation (at ear corn formation) harvest (first decade of October) The first cycle of the rotation Anul Rotation 1 Rotation 2 Rotation 3 triticale corn Potato+ Sugarbeet+ vegetable corn Potato+ Sugarbeet+ vegetable Potato+ Sugarbeet+ vegetable triticale Fig. 1. The crop rotation The second cycle of the rotation triticale corn triticale corn Potato+ Sugarbeet+ vegetable 6

8 o For variants without stubble field herbicide application: triticale harvest (third decade of July) remove the stubble field by superficial ploughing (immediately after harvest) single disk passing in the first decade of September - 30 t/ha manure applied in the second decade of September, in 2003 rotation 2 and 3 - and in 2004 rotation 2 autumn ploughing (first decade of October) single rotary harrow in spring (first decade of April) mineral fertilisation (second decade of April) single seedbed combination passing the day before seeding seeding (third decade of April) first hoeing in the 3 hoeing witness variant and post-emergence herbicide application (second decade of May) second hoeing in the 3 hoeing witness variant and post-emergence herbicide application + first foliar fertilisation, at 5-6 corn leaves stage third hoeing in the 3 hoeing witness variant and first in the variants with hoeing after application of associated or complex herbicides (first or second decade of June) the second foliar fertilisation - harvest Fertilisation: o organic- with fermented manure 30 to/ha starting in autumn 2003 rotations 2 and 3 and finishing in autumn 2004 (rotation 1), so that every rotation was organic fertilised; o mineral: 2 fractions: first - NPK with ratio formula 15:15:0: - at germination bed preparation is assured a N 40 P 40 dosage; the second at 6-8 leaves stage with ammonium nitrate, being assured a total dosage of N 70 P 40 K 0 ; o foliar: 2 fractions of Murtonik 20:20:20 Me: first at the same time with the post-emergence herbicide application at 5-6 leaves stage, 2 l/ha dosage; the second - at ear corn formation, the same dosage. The field where the experimental plot is organized is a class I quality type, with 86 bonitation points. Soil is an aluviosol calcaric molic coluvic soil type, with a good fertility, humus content of 3.84% in the first 60 cm, being assured a humus reserve of t/ha. Content of nutritive elements is different in the soil profile, corresponding to an average supply of total nitrogen, very good supply of potassium and weak supply in phosphorous. Chemically speaking, the only intervention needed is completion of P reserve. 7

9 The thermal and precipitation regime during the corn vegetation period was different in the experimental 4 years, thus the spring and development conditions of weed and the spring and development conditions of corn crop were also different. Year 2004 was a relatively normal year compared to multi-annual average values, during the vegetative period of corn crop being registered average thermal deviations of +0,58 o C, with significant deviations registered in April (+1,0 o C) and June (+1,6 o C) and precipitation deviations of +62,2 mm. The positive thermal and negative precipitation deviations were a surprise for the start of corn crop (May and beginning of June), thus being felt in the weed competition but also the level of production. Year 2005 was an exceptional year from climatic point of view, being characterised as extremely rainy and warm (+ 1,2 o C and mm compared to multi-annual average values). The corn vegetation period was warm (+0,95 o C compared to m.a.a. values) and rainy, especially in April, May, August and September; during the whole period of vegetation a plus of 167,1mm was registered. Over all, the agricultural year 2005 was a year with pronounced weeding potential. Year 2006 was a less warm year, compared with the previous years (the annual average deviation was +0,9 0 C) and less rainy, the sum of precipitations was close to multiannual average value (+34,1mm), but very moody, being considered as a year less favourable for the corn crop start and with negative influence of level of production, but significant influence, both positive and negative on weeding. Thus, the corn vegetation period (April-September 2006) can be appreciated as warm (the positive deviation being of 1,1 0 C). The months when significant positive deviations compared to m.a.a. values were registered were April (+2,2 0 C) and May (+1,9 0 C). Low precipitations during April September 2006 overcome the normal value by 50,1 mm, which is a deviation much smaller then the previous years, but with very large fluctuations in precipitations during corn vegetative period. April was very rainy the first two decades, followed bay a dry May, when corn crop suffered a little. The rains dropped in the second part of May saved the corn crop, which passed in optimal conditions the vegetative stages of this period. The dryness in the first half of May negatively influenced the spring and development of corn crop, but at the same time, influenced the weeding level, which was lower. 8

10 Year 2007 was a very warm (the m.a.a. deviation was +2,2 0 C) and rainy at the same time; the sum of precipitations overcome the m.a.a. by 104,4 mm, but the their repartition was less good for the corn crop. Analyzing the vegetative period of corn in 2007 showed that was not a very good year for corn crop. The excessive dryness during June and moderate in July defined the negative influence of this year climate on corn crop yield. In order to improve the system of post-emergence weed control in corn crop was important to proper organise the information system, the research data collection and to make the following determinations: Determinations of corn specific weeding characteristics in the studied area: determination of floral compositions, determination of annual and average weeding degree (number and weight), determination of annual weight of weed species and establishing their average weight, establishing the weeding fluctuations specific to the experimental 4 years, establishing the weed species problematic for corn crop cultivated in the high meadow area of Alba County (the Noşlac area) and not in the last establishing the correlations between level of corn productions and level of weeding; Determination of tested weed control variants efficacy, namely 4 different postemergence control technologies: determination of weed control degree, assured in the first days of corn vegetation (corresponding to the 30 days after first herbicide application determination), annual and 4 years average values; determination of weed control degree, assured after days of corn vegetation period, for every tested variant (corresponding to the 45 days after first herbicide application determination), annual and 4 years average values; comparative determinations between the 4 tested weed control technologies, annual and 4 years average values; Determination of level of obtained grain productions: annual and 4 experimental years average determination, comparative analyses of tested weed control variants and of tested weed control technologies; Determination of economic efficiency: calculation of production value, production expenses, total profit, and rate of profit for every tested weed control variant and their comparative analysis; also, calculation of average profit and average rate of profit for the tested 4 weed control technologies and comparative analysis; 9

11 RESULTS OBTAINED The data included in the PhD thesis, obtained from the experimental field during and interpreted, accordingly to the rules of statistical processing and interpretation, make possible the formulation of certain conclusions and recommendations concerning the improvement of post-emergence weed control system in corn crop. Based on the experimental results, I formulated the following opinions, with the mention that by these results I tried to add something to the knowledge in the field of weeding specific to the corn crop cultivated in similar areas and of present weed control methods, specifically their influence on economic indices and the possibility of extension. PARTIAL RESULTS CONCERNING THE CHARACTERISTICS OF WEEDING IN CORN CROP CULTIVATED IN NOŞLAC COMMUNE AREA, ALBA COUNTY The specific weeding of corn crop, in conditions of experimental field from Noşlac, determined in the 4 years of culture (2004, 2005, 2006 and 2007) reveals a diversified floristic composition, comprised of species from all four representative groups: annual monocotyledonous, perennial monocotyledonous, annual dicotyledonous and perennial dicotyledonous. The total number of species determined in corn crop during the four experimental years was 23 (2 annual monocotyledonous, 1 perennial monocotyledonous, 14 annual dicotyledonous and 6 perennial dicotyledonous), and the annual floristic composition of corn weed comprises between 18 and 20 species, depending on the year. plants/sq.m. The average weeding degree during the research period is very high, around 101,7 The coverage degree of soil with weed at the beginning of corn vegetative period, calculated as an 4 years average, is appreciated at 26% - a high value, considering the period in discussion (15-20 days after the spring of corn crop). In every one of the 4 experimental years, the competition between weed species was high during the whole period of corn vegetation, the soil potential for weeding being relatively high, and the climatic conditions being favourable for vegetative development of weed species and even for late infestations in weed control variants. The strong competition 10

12 of the weed species was observed especially during 2005, and the weakest competition, established by the general weeding degree and soil coverage was linked to year Statistically, the average weeding in the witness plots is significantly different in the 4 studied years (table 1). In year 2005 was observed an increased weeding of witness plots, statistically very significant compared to year 2004, the increase of weeding in 2006 being statistically distinct significant compared to year 2004, and in 2007 a decrease statistically very significant. It can be stated that, besides the dryer climate in 2007, favourable to a reduced weeding at the beginning of the vegetation period of corn crop, the effect of tested 4 year crop rotation could also be observed. Curr.no. Year Number of plants/m 2 Evolution of weed growth degree during research period Noşlac, % compared to Control Differences compared to Control (pl./m 2 ) , Ctr. Ctr ,30 184,60 75,30 *** ,00 109,00 8,00 ** ,40 74,60-22,60 LSD 5% = 4,16 plante/m 2 LSD1% = 6,31 plante/m 2 LSD 0.1% = 10,13 plante/m 2 Significance Table 1. The representative weed species is the annual monocotyledonous, representing for all 4 years an average of 48,5% from the total weed species present in corn crop. The annual dicotyledonated species follow, with an average presence of 43,6% and the perennial dicotyledonous, with an average weeding participation of 13,5% (fig. 2). It cannot be minimized a certain biological group when its frequency in a hoed crop is reduced because, by eliminating the competition of the majority group or groups (by orienting the weed control methods towards those), the low frequency specie can launch rapidly and enter the competition with the crop (especially when the weed seed reserve of soil shows potential for infestation with the minority species in vegetation). 11

13 %/total 13,5 0,5 48,5 43,6 AM AD PD PM Fig. 2. Average percent of weed groups in corn crop weed growth (Noşlac, ) In the case of experimental field in Noşlac, Alba County, during the 4 years of research, statistically, the weight of weed groups significantly modifies (fig. 3). Thus, if in 2004 the annual monocotyledonous species were dominant, significantly increase in 2005 after manure fertilisation of the corn crop and due to very favourable climatic conditions, then in the next years show a decrease, by 2007 being statistically observed a very significant decrease compared to the time that experiments began. At the same time there is registered an opposite evolution for the annual dicotyledonous and perennial species. It is remarkable that in 2007 the weight of perennial dicotyledonous species reach 20,2% compared to their weight at the beginning of experiments (11,2%). 100 number of plants/square meter Ctr ** *** ** AM AD PD DL5%=3,83; DL1%=5,80; DL0,1%=9,32 DL5%=3,46; DL1%=5,25; DL0,1%=8,43 ** Ctr - Ctr. DL5%=2,00; DL1%=3,03 DL0,1%=4,87 - year Fig.3. Frequence evolution (plants / m 2 ) for the main three groups of weed species in corn crop (Noşlac, ) 12

14 Observing the average weight of weed species within the corn crop from the research field during the 4 years of experiments (fig. 4), the constant apparition of the weed species in the weeding determination points and also the biological features of the weeds in what concerns the competition potential, we can consider that 15 weed species are problematic for the corn crop cultivated in Noşlac area, Alba county: Echinochloa crus-galli, Chenopodium album, Amaranthus retroflexus, Setaria glauca, Cirsium arvense, Galinsoga parviflora, Convolvulus arvensis, Sonchus arvensis, Polygonum lapathyfolium, Polygonum persicaria, Hibiscus trionum, Agropyron repens, Xanthium strumarium, Atriplex patula şi Chenopodium polyspermum %/total 37.9 ECHCG CHEAL AMARE SETGL CIRAR GALPA CONAR SONAR POLLA POLPE HIBTR AGRRE XANST ATRPA CHEPO STEME POLAV SYMOF LATTU RAPRA CHEHY LAPCO RUBCH Fig. 4. Average participation of weed species in corn crop weed growth (Noşlac, ) The negative evolution tendency of weeding characteristics, specific to the corn crop cultivated in the studied area, can be supported or stopped by the following aspects: o soil and climate conditions are favourable for the development of weed species (annual and perennial) that strongly compete with the corn crop and especially for the species with phased appearance, that practically invade the previous triticale stubble field or the corn crop in the second part of vegetation period; 13

15 o the massive infestation with annual mono-cotyletonated species, especially Echinochloa crus-galli and Setaria glauca, that have already a very strong seed reserve in soil and are species that strongly compete with other weed species, being present the risk of their negative impact on the cultivated field; o increase of perennial di-cotyledonated species incidence; they are dryness resistant during the stressful periods for corn crop or other annual species, and are very hard to control with corn selective herbicides (especially Convolvulus arvensis, Sonchus arvensis, Cirsium arvense, Symphytum officinale, etc); o use of weed control technologies with major impact on slowing the development of areas occupied with dangerous species (glyphosate in previous crops stubble field); o agriculture exploitations organisation, in the manner that the applied crop rotations have a bigger contribution to diminishing the biological reserve of weed species in soil and at the same time, to improving the fertility conditions of soils. PARTIAL RESULTS CONCERNING THE EFICACY OF POST-EMERGENCE WEED CONTROL TECHNOLOGIES IN CORN CROP By comparing the four tested weed control technologies with the classical weed control technology, applied in the control variant no 1 (fig. 1 and table 2), in mate matter of efficacy in weed control in the first days of corn vegetation, it can be concluded that: The 2 years chemical control technology (stubble field treatment with glyphosate and a post-emergence treatment with associated or complex herbicides) statistically presents insignificant differences compared to the manual hoeing variant, and assured an average control percent of 98.03; The other control technologies have control average values that overcome 90%, but statistically are significantly different compared to witness variant and the fourth tested technology; The 2 years chemical control technology with 2 post-emergence treatments in corn crop is very close to the mixed control technology with single treatment completed with single hoeing. To make the difference between the two, the production results and economic efficiency must be analysed. 14

16 SD Values 1,99 2,09 2,15 2,20 A A B % control C C number of variant V1control 1 1st technology 2nd technology 3rd technology 4th technology Curr No Fig.5. Specific curves of average weed control degree (%) accomplished by tested technologies in the first days of corn vegetation (Noşlac, ) Average weed control degree accomplished in tested variants from the four tested technologies in the first days of corn vegetation Noşlac, Table 2. Weed control technology Control I- Specific variants for weed control technology 3 manual hoeing Avera ge 1. Chemical: single postemergent treatment with associated herbicides Chemical: 2 postemergent treatments with associated herbicides in fractionated doses 3. Mixed: precocious postemergent treatment with associated or complex herbicides followed by a mechanical weeding 4. Chemical in 2 years: glyphosate-based herbicides applied precrop stubble and one post-emergent treatment with associated or complex herbicides V V V V V V V V V V V V V V V V V V V V V V V V LSD (p 5%) =1.99% LSD (p 1%) =2.71% LSD (p 0.1%) =3.67% V 9 V

17 and fig. 6): By adding another days to the first period of study, can be concluded (table 3 The average control percent values, calculated for every technology and period, decrease to very significant differences (statistically speaking) compared to witness technology (three manual technologies). The chemical control technology with a single treatment with associated herbicides assured just over 80% weed reduction, the other technologies overcoming 90% reduction; The glyphosate technology is surpassed (as efficacy) by the third tested technology (single post-emergence treatment with associated or complex herbicides + a late hoeing). Even if the percentual differences are small (average of 3,7%), they are all statistically assured; As the corn crop is passing through its vegetation period, the glyphosate technology Curr No matches the technology no 2 (repeated treatments with associated herbicides, in postemergence): Average weed control degree accomplished in tested variants from the four tested technologies after days of corn vegetation Weed control technology Control I - 3 manual 1. Chemical: single postemergent treatment with associated herbicides Chemical: 2 post-emergent treatments with associated herbicides in fractionated 98.5 doses 3. Mixed: precocious postemergent treatment with associated or complex 98.5 herbicides followed by a mechanical weeding 4. Chemical in 2 years: glyphosate-based herbicides applied pre-crop stubble and 98.5 one post-emergent treatment with associated or complex herbicides Noşlac, Specific variants for weed control technology Table 3. hoeing Average V V V V V V V V V V V V V V V V V V V V V V V V LSD (p 5%) =2.04% LSD (p 1%) =2.77% LSD (p 0.1%) =3.75% V 9 V

18 B A C % control C D 80 SD values 2,03 2,14 2,20 2, number of variant V1 control 1 1st technology 2nd technology 3rd technology 4th technology Fig.6. Specific curves of average weed control degree accomplished by tested technologies in the first days of corn vegetation ( Noşlac, ) Before corn crop harvest, the specific biomass of weed species present in the culture is the comparing value to appreciate the general efficacy of weed control technologies. It is remarkable that, compared to classic weed control technology, two other tested control technologies are statistically very significant: the chemical technology with glyphosate in the stubble field + post-emergence treatment with associated herbicide and the mixed control technology comprising post-emergence early treatment with associated herbicides and late mechanical hoeing (table 4). By comparing the control degree curves of the entire vegetation period of corn crop for the 4 tested control technologies (fig. 7), it can be noticed that there are no statistically assured differences between 3 of them. The exception is the chemical technology with a single treatment, which is obviously inferior. This statistically homogenisation is possible due to specific fluctuations in weeding control of every technology during the period of vegetation. 17

19 Curr No Average weed control degree accomplished in tested variants from the four tested technologies at the ending of corn vegetation Weed control technology Control I - 3 manual 1. Chemical: single postemergent treatment with associated herbicides Chemical: 2 post-emergent treatments with associated herbicides in fractionated doses 3. Mixed: precocious postemergent treatment with associated or complex herbicides followed by a mechanical weeding 4. Chemical in 2 years: glyphosate-based herbicides applied pre-crop stubble and one post-emergent treatment with associated or complex herbicides Noşlac, Specific variants for weed control technology Table 4. hoeing Avera ge V 3 V 4 V 5 V 6 V 7 V 8 V 9 V V V V V V V V V V V V V V V V V V V LSD (p 5%) =4.06% LSD (p 1%) =5.51% LSD (p 0.1%) =7.48% o 83.3 o % control B B A 80 B C SD values 4,05 4,26 4,38 4, number of variant V1 control technology 1 technology 2 technology 3 technology 4 Fig.7. Specific curves of average weed control degree accomplished by tested technologies at the ending of corn vegetation (Noşlac, ) 18

20 Compared and analyzed between them, the control degree diagrams for every of the three periods of determination, specific to the four weed control technologies in corn crop (fig. 8, 9, 10 and 11) show differences between the technologies, namely the fields limited by the control degrees on every determination period and the whole vegetation period of corn. For the first technology tested for all 8 control variants, we can observe the obvious reduction of the second moment observation area (45 days after herbicide treatment) corresponding to a days interval in the vegetation period of corn, compared to the first observation moment (corresponding to first days of corn vegetation). Also, the area corresponding to the third observations moment for control degree (end of vegetation period of corn crop) is much diminished. Therefore, the good and very good weed control assured by this chemical technology is very short in time. % of weed control oo V10 97,2 83 V1 Ctr , , ,8 V3 94,3 V9 oo 96,7 96,1 V8 81,3 81, , , ,3 73,4 80,1 79,5 67,3 80,8 77, ,3 77,7 81,7 94,5 94,4 V5 V4 91,3 30 days 45 days at the harvest V7 96,5 V6 oo LSD (p5%) = 4.85 % LSD (p1%) = 6.67 % LSD (p0.1%) = 9.19% Fig. 8. Weed control degree accomplished by first technology variants in the three moments of determinations (Chemical weed control: single post-emergent treatment with associated herbicides) 19

21 The diagram presented in fig. 9, specific to the second chemical technology of weed control (comprised by two post-emergence treatments, from which one is an precocious one) reveals a good and very good efficacy of treatments for both moments of determination, corresponding to first days of vegetation period, before harvesting showing a plus in efficacy owed to cumulating effects of the 2 treatments). % of weed control V16 91,9 91,1 80 Ctr. V ,9 98, , ,2 V11 91,4 90,55 V15 93,792,9 84,1 81, ,6 82,3 92,3 92,8 V12 91,55 90,5 92,1 90,5 V14 30 days 45 days at the harvest V13 LSD (p5%) = 1.44 % LSD (p1%) = 2.01 % LSD (p0.1%) = 2.84% Fig. 9. Weed control degree accomplished by the second technology variants in the three moments of determination (Chemical weed control: two post-emergent treatments with associated herbicides in fractionated doses) For the third control technology, tested in 6 variants, comprising a single precocious post-emergence treatment with associated or complex herbicides and a late hoeing (fig. 10), the two moments for efficacy appreciation, covering the period of maximum sensitivity of corn crop to weeding, are practically confounded because of the control degrees which are very close; thus, with this technology, the corn crop is saved from weed competition, included those with belayed spring. For this technology is observed the biggest girth of the area for control established at the end of vegetation period of corn. 20

22 % of weed control o V22 V1 Ctr ,9 98, ,3 V17 88,3 96, , , ,4 V ,1 84, ,5 88,8 90,8 V18 86,8 81,3 94,5 o 97 V20 30 days 45 days at the harvest 89,5 91,8 V19 LSD (p5%) = 2.18% LSD (p1%) = 3.05 % LSD (p0.1%) = 4.31% Fig. 10. Weed control degree accomplished by the third technology variants in the three moments of determinations (Mixed weed control: precocious post-emergence treatment with associated or complex herbicides followed by a mechanical weeding) For technology IV (fig. 11), one can observe high values of control degree, registered in the first determination, correlated to decrease of general weeding compared to control variant, due to herbicide treatment in previous crop stubble field; during the vegetation period of corn crop is observed a relatively constant decrease of control degree, measured on 6 variants, some of them over passing the 3 hoeing witness at the determination moment no 3. It is worth to mention that for this technology the level of control remains around 90% at the determination moment no 2 (day in the vegetation period) and over 80% at the determination moment no 3 (before harvest) in most of the variants. 21

23 % of weed control after 30 days, 45 days and at the harvest Ctr. V ,9 oo ,5 - V28 97,5 89,2 78, ,3 91,4 86,5 98,5 V23 65 oo V27 97, , ,8 V24 - o 84,2 90,5 98 V26 82, ,6 o V25 LSD (p5%) = 3.90% LSD (p1%) = 5.47 % LSD (p0.1%) = 7.73 % Fig.11. Weed control degree accomplished by the fourth technology variants in the three moments of determinations (Chemical weed control in two years: glyphosate-based herbicides applied pre-crop stubble and one post-emergent treatment with associated or complex herbicides) PARTIAL RESULTS CONCERNING THE INFLUENCE OF CONTROL TECHNOLOGIES TESTED ON CORN CROP YIELD The average crop yields registered in witness variants are 6884 kg/ha in control variant I classical weed control with 3 manual hoeing and only 932 kg/ha in control variant for weeding (V 2 no hoeing). The crop yields obtained in the variants within the chemical control technology for corn crop with a single post-emergence treatment framed in the interval 4720 kg/ha variant 3 (EQUIP OD 2 l/ha + CALLISTO 0.2 l/ha) and 6320 kg/ha variant 10 (TITUS 25DF 30 g/ha + BUCTRIL UNIVERSAL 0.8 l/ha). 22

24 The crop yield difference against control variant with 3 hoeing is statistically very significant for most of the tested chemical control variants, except the 2 variants that used associations of different antigraminee herbicides to antidicotyledonous herbicide BUCTRIL UNIVERSAL 0.8 l/ha. For these variants the yield difference against the witness is under 800 kg corn grains/ha. The crop yields obtained in the variants within the chemical control technology for corn crop with two post-emergence treatments framed in the interval 5980 kg/ha - variant 11 (EQUIP OD l/ha + BROMOTRIL 40EC l/ha) and 6385 kg/ha - variant 15 (TITUS 25DF g/ha + MUSTANG l/ha). Except the first variant mentioned, in all other variants tested in this technology, the crop yields obtained overcome 6000 kg/ha, being considered better variants than those tested in the first technology. The production yield differences against the witness variant I (3 manual hoeing) are lower then those registered with the chemical control technology for corn crop with a single postemergence treatment, framing between 499 kg/ha (V 15 - TITUS 25DF g/ha + MUSTANG l/ha) and 904 kg/ha (V 11 - EQUIP OD l/ha + BROMOTRIL 40EC l/ha. The crop yields obtained in the variants within the mixed control technology for corn crop with a precocious post-emergence treatment with complex or associated herbicides and a belayed mechanical hoeing, framed in the interval 6320 kg/ha - variant 18 (BASSIS 25 g/ha + Trend 0.1% and mechanical hoeing) and 6740 kg/ha - variant 22 (TITUS 25DF 30 g/ha + RING 80WG 20g/ha + Extravon 0.15l/ha and mechanical hoeing). In all variants tested with this technology, the production yields obtained are very close to control variant I yield, the registered differences being statistically insignificant for 3 of them: V 22 (TITUS 25DF 30 g/ha + RING 80WG 20g/ha + Extravon 0.15l/ha and mechanical hoeing ), V 20 (EQUIP OD 2 l/ha + RING 80WG 20g/ha + Extravon 0.15l/ha and mechanical hoeing) and V 17 ( TITUS PLUS 300 g/ha and mechanical hoeing); for the other 3 variants tested, the differences are statistically significant for DL values p5% kg corn grains/ha. It is worth to mention also for yields obtained the variants comprising associations of anti-graminee herbicides, very efficient in Noşlac conditions, and between complex 23

25 herbicides and TITUS PLUS herbicide (300 g/ha). These associations, along with the belayed mechanical hoeing, acquire a prolonged control in weeding specific to corn crop. The crop yields obtained in the variants within the chemical control technology for corn crop with two treatments: first one, in the previous crop stubble field with glyphosate based herbicides and the second, post-emergence treatment (at 5-6 corn leaves) with complex or associated herbicides, framed in the interval 6362 kg/ha - variant 28 (LEONE 36 SL 4l/ha in stubble field + BASSIS 25 g/ha + Trend 0.1%) and 6800 kg/ha - variant 24 (LEONE 36 SL 4l/ha in stubble field +TITUS 25DF 30 g/ha + Trend 0.1% + BUCTRIL UNIVERSAL 0.8 l/ha). The production yield differences against the witness variant I are framed between kg/ha (V 24 ) and 384 kg/ha (V 25 ). By comparing all variants for weed control tested with the control variant I (3 manual hoeing), one can observe the variants from the chemical control technology with 2 treatments: first one, in the previous crop stubble field with glyphosate based herbicides and the second, post-emergence treatment (at 5-6 corn leaves) with associated herbicides, followed by mixed control technology: a precocious post-emergence chemical treatment (with associated herbicides, especially anti-graminee) and a belayed mechanical hoeing (Table 5). Four of the variant for weed control tested obtained a corn grains production close to control variant I, the differences between variants or between variants and witness are statistically insignificant. These variants are: 1) V 24 : LEONE 36 SL 4l/ha applied in stubble field +TITUS 25DF 30 g/ha + Trend 0.1% + BUCTRIL UNIVERSAL 0.8 l/ha applied in post-emergence; 2) V 22 : TITUS 25DF 30 g/ha + RING 80WG 20g/ha + Extravon 0.15l/ha + belayed mechanical hoeing; 3) V 23 : LEONE 36 SL 4l/ha applied in stubble field + EQUIP OD 2l/ha + Extravon 0.15l/ha + BUCTRIL UNIVERSAL 0.8 l/ha applied in post-emergence and 4) V 26 : LEONE 36 SL 4l/ha applied in stubble field +TITUS 25DF 30 g/ha + Trend 0.1% + CALLISTO 0.2 l/ha. For all these variants, the average control percent, calculated for the entire vegetation period of corn crop, surpasses 90%. 24

26 Table 5. Weed control efficacy and corn crops yield accomplished in all of tested variants, compared to first control variant with 3 manual hoeing Curr.no Number of variant Weed control variant Average control % Significance Yield kg/ha Significance 1 V 1 Control I-3 manual hoeing 95.6 Mt 6884 Ctr. 2 V 3 EQUIP OD: 2 l/ha + CALLISTO 0.2 l/ha V 4 EQUIP OD: 2 l/ha + RING 80 WG 20 g/ha + Extravon 0,15 l/ha V 5 EQUIP OD: 2 l/ha +LONPAR: 2l/ha V 6 EQUIP OD: 2 l/ha + BUCTRIL UNIVERSAL 0.8 l/ha 6 V 7 TITUS 25DF: 30g/ha (+Trend) + CALLISTO 0.2 l/ha 85.3 oo V 8 TITUS 25DF: 30g/ha + RING 80 WG oo 5850 g/ha + Extravon 0,15 l/ha 8 V 9 TITUS 25DF: 30g/ha + LONPAR: 2 l/ha V 10 TITUS 25DF: 30g/ha (+Trend) + BUCTRIL UNIVERSAL: 0.8 l/ha 10 V 11 EQUIP OD: 1 + 1,5 l/ha + BROMOTRIL 40 EC 0,6 + 0,6 l/ha 11 V 12 EQUIP OD: 1 + 1,5 l/ha + MUSTANG: 0,5 + 0,5 l/ha 12 V 13 EQUIP OD: 1 + 1,5 l/ha + CALLISTO 0,2 + 0,2 l/ha 13 V 14 TITUS 25DF:20+20g/ha (Trend) +BROMOTRIL 40 EC 0,6 + 0,6 l/ha 14 V 15 TITUS 25DF: g/ha (Trend) + MUSTANG 0,5 + 0,5 l/ha 15 V 16 TITUS 25DF: 30g/ha (+Trend) + CALLISTO l/ha 16 V 17 1) TITUS PLUS: 300 g/ha 2) mechanical hoeing 17 V 18 1) BASSIS: 25g/ha (Trend 0,1%) 2) mechanical hoeing 18 V 19 1) EQUIP OD: 2,0 l/ha + BROMOTRIL 40 EC 0,8 l/ha 2) mechanical hoeing 19 V 20 1) EQUIP OD: 2 l/ha + RING 80 WG 20 g/ha (+ Extravon 0,15 l/ha) 2) mechanical hoeing 20 V 21 1) TITUS 25DF: 20 g/ha (Trend) + BROMOTRIL 40 EC 2) mechanical hoeing 21 V 22 1) TITUS 25DF: 30g/ha + RING 80 WG 20 g/ha (+ Extravon 0,15 l/ha) 2) mechanical hoeing 22 V 23 1) LEONE 36 SL: 4 l/ha 2)EQUIP OD: 2 l/ha +BUCTRIL U. 0.8 l 23 V 24 1)LEONE 36 SL: 4 l/ha 2) TITUS 25DF: 30g/ha (+Trend) +BUCTRIL UNIV: 0.8 l/ha 24 V 25 1)LEONE 36 SL: 4 l/ha 2)EQUIP OD: 2 l/ha +CALLISTO 0.2 l 25 V 26 1)LEONE 36 SL: 4 l/ha 2) TITUS 25DF: 30g/ha (+Trend) + CALLISTO 0.2 l/ha 85.9 oo oo o oo o oo 87.7 o oo 6520 o 86.0 oo o 6365 oo o oo o o 25

27 Curr.no Number of variant Weed control variant 26 V 27 1)LEONE 36 SL: 4 l/ha 2)TITUS PLUS: 300 g/ha 27 V 28 1)LEONE 36 SL: 4 l/ha 2)BASSIS: 25g/ha (+Trend 0,1%) Average control % Significance Yield kg/ha Significance 89.0 o 6420 oo 88.4 o 6362 LSD (p 5%) = 6.15 % LSD (p 1%) = 8.20 % LSD (p 0.1%) = % LSD (p 5%) = 293 kg/ha LSD (p 1%) = 388 kg/ha LSD (p 0.1%) = 502 kg/ha Between the control degree obtained in tested variants and the corn grains production is established a very significant positive correlation: r = *** (fig. 12), and the linear regression equation allows the calculation of production depending on achieved control degree. Thus, for an average weed control of 75%, in Noşlac conditions, the production that can be obtained is calculated with the formula y = x de kg/ha yield kg/ha y = 125,59x ,1 r = 0.859*** % of weed control Fig.12. The relationship between weed control degree (%) accomplished in tested variants and the corn crop yield (kg/ha) As a result of multiple comparisons with Duncan test, we can observe the following: 4 of the tested weed control variants are in the leading positions in production classification, with differences between them (including witness variant), statistically insignificant. These variants are: 1) V 24 : LEONE 36 SL 4l/ha applied in stubble field +TITUS 25DF 30 g/ha + Trend 0.1% + BUCTRIL UNIVERSAL 0.8 l/ha applied in post-emergence; 2) V 22 : TITUS 25DF 30 g/ha + RING 80WG 20g/ha + Extravon 0.15l/ha + belayed mechanical hoeing; 3) V 23 : LEONE 36 SL 4l/ha applied in stubble field + EQUIP OD 2l/ha + Extravon 0.15l/ha + BUCTRIL UNIVERSAL 0.8 l/ha applied in post-emergence and 4) V 26 : LEONE 36 SL 4l/ha applied in stubble field 26

28 +TITUS 25DF 30 g/ha + Trend 0.1% + CALLISTO 0.2 l/ha. Three of these variants pertain to weed control technology no IV, the success being granted by the culture hygiene achieved with herbicide LEONE 36 SL 4l/ha applied in previous triticale stubble field and by the efficacy of combinations of herbicides applied post-emergence in the corn crop (especially BUCTRIL UNIVERSAL 0.8 l/ha applied in association with TITUS 25DF 30 g/ha + Trend 0.1% or EQUIP OD 2l/ha + Extravon 0.15l/ha or the combination between 2 graminicide herbicides: TITUS 25DF: 30g/ha + RING 80 WG 20 g/ha + Extravon 0,15 l/ha completed with a belayed mechanical hoeing. 3 variants: V 20 : EQUIP OD: 2 l/ha + RING 80 WG 20 g/ha (+ Extravon 0,15 l/ha) + mechanical hoeing; V 17 : TITUS PLUS: 300 g/ha + mechanical hoeing and V 25 : LEONE 36 SL: 4 l/ha + EQUIP OD: 2 l/ha +CALLISTO 0.2 l, are near the leading variants by means of the obtained crop production, but statistically are significant different only from the witness variant I 3 manual hoeing. Another 3 tested variants for weed control: V 27 : LEONE 36 SL: 4 l/ha + TITUS PLUS 300g/ha; V 21 : TITUS 25DF: 30g/ha + Trend 0.1% + BROMOTRIL 40EC 0.8 l/ha + mechanical hoeing and V 19 : EQUIP OD: 2 l/ha + BROMOTRIL 40EC 0.8 l/ha + mechanical hoeing, obtained crop productions very close to those mentioned above q/ha yield V1 V24 V22 V23 V26 V20 V17 V25 V27 V21 V19 V15 V28 V18 V14 V12 V13 V10 V6 V16 V11 V9 V8 V5 V4 V7 V3 V2 Fig. 13. Variants of weed control classification depending on corn crop yield 27

29 PARTIAL RESULTS CONCERNING THE ECONOMIC EFFICIENCY OF IMPROVED TECHNOLOGIES FOR POST-EMERGENCE WEED CONTROL IN CORN CROP In the general classification of profit obtained from all 28 tested variants, the variant 22, component of weed control technology no III, occupied the first place; in this variant were tested 2 anti-grass herbicides associated (TITUS25DF 20 g/ha and RING 80WG 20 g/ha), followed by a belayed mechanical hoeing. For the first 13 variants in the classification, the average weed control is framed between 85.3% (V 14 ) and 94.1% (V 22 ), the crop production obtained is framed between 6290 kg/ha (V 14 ) and 6800 kg/ha (V 24 ), and the profit between lei/ha (V 26 ) and lei/ha (V 22 ). From all 26 variants tested (2 being control variants), the profit obtained is under 1000 lei/ha only for 4 variants, all in the first tested technology (chemical a single post-emergence treatment). In these variants, the average percent of control frames between 80.4 (V 3 ) and 86.6 (V 5 ), and the registered crop yields are all under 6000 de kg/ha. In the first 13 variants in the classification we can find all 6 variants from the mixed weed control technology (single precocious post-emergence treatment at 2-3 corn leaves, followed by a belayed mechanical hoeing), 4 variants from the 2 years chemical technology (glyphosate treatment in the previous crop stubble field and a post-emergence treatment in corn crop with associated or complex herbicides), 2 variants from the chemical control technology with 2 post-emergence treatments with fractioned doses herbicides (combinations between TITUS 25DF g/ha and MUSTANG l/ha or BROMOTRIL 40EC l/ha) and a variant from chemical technology with a single post-emergent treatment at 5-6 corn leaves stage (variant 10 association of TITUS25DF 30 g/ha and BUCTRIL UNIVERSAL 0.8 l/ha). 28

30 Classifi cation Variants classification depending on accomplished total profit Number Weed control variant of variant 1 V 22 1) TITUS 25DF: 20g/ha + RING 80 WG 20 g/ha (+ Extravon 0,15 l/ha) 2) mechanical hoeing 2 V 24 1)LEONE 36 SL: 4 l/ha 2) TITUS 25DF: 30g/ha (+Trend 0.1%) +BUCTRIL UNIV: 0.8 l/ha 3 V 17 1) TITUS PLUS: 300 g/ha(trend 0,1%) 2) mechanical hoeing 4 V 21 1) TITUS 25DF: 20 g/ha (Trend 0,1%) + BROMOTRIL 40 EC 0.8 l/ha 2) mechanical hoeing 5 V 10 TITUS 25DF: 30g/ha (+Trend 0,1%) + BUCTRIL UNIVERSAL: 0.8 l/ha 6 V 20 1) EQUIP OD: 2 l/ha + RING 80 WG 20 g/ha (+ Extravon 0,15 l/ha) 2) mechanical hoeing 7 V 18 1) BASSIS: 25g/ha (Trend 0,1%) 2) mechanical hoeing 8 V 23 1) LEONE 36 SL: 4 l/ha 2)EQUIP OD: 2 l/ha +BUCTRIL U. 0.8 l + Extravon 0,15 l/ha 9 V 15 TITUS 25DF: g/ha (Trend 0,1%) + MUSTANG 0,5 + 0,5 l/ha 10 V 19 1) EQUIP OD: 2,0 l/ha +Extravon 0,15 l/ha+ BROMOTRIL 40 EC 0,8 l/ha 2) mechanical hoeing 11 V 28 1)LEONE 36 SL: 4 l/ha 2)BASSIS: 25g/ha (+Trend 0,1%) 12 V 14 TITUS 25DF:20+20g/ha (Trend0,1%) +BROMOTRIL 40 EC 0,6 + 0,6 l/ha 13 V 26 1)LEONE 36 SL: 4 l/ha 2) TITUS 25DF: 30g/ha (+Trend0,1%) + CALLISTO 0.2 l/ha 14 V 27 1)LEONE 36 SL: 4 l/ha 2)TITUS PLUS: 300 g/ha (+Trend0,1% 15 V 6 EQUIP OD: 2 l/ha + BUCTRIL UNIVERSAL 0.8 l/ha +Extravon 0,15 l/ha 16 V 12 EQUIP OD: 1 + 1,5 l/ha + Extravon 0,15 l/ha + MUSTANG: 0,5 + 0,5 l/ha 17 V 8 TITUS 25DF: 30g/ha + RING 80 WG 20 g/ha + Extravon 0,15 l/ha 18 V 25 1)LEONE 36 SL: 4 l/ha 2)EQUIP OD: 2 l/ha +CALLISTO 0.2 l 19 V 9 TITUS 25DF: 30g/ha (+Trend 0,1%) + LONPAR: 2 l/ha 20 V 11 EQUIP OD: 1 + 1,5 l/ha + BROMOTRIL 40 EC 0,6 + 0,6 l/ha 21 V 16 TITUS 25DF: 30g/ha (+Trend0,1%) + CALLISTO l/ha 22 V 13 EQUIP OD: 1 + 1,5 l/ha + CALLISTO 0,2 + 0,2 l/ha 23 V 4 EQUIP OD: 2 l/ha + RING 80 WG 20 g/ha + Extravon 0,15 l/ha Average weed Yield Total Profit control % kg/ha lei/ha A A AB AB AB ABC ABC ABCD ABCD ABCD ABCDE ABCDE ABCDE BCDE BCDEF Table 6. Segnificance CDEFG CDEFG DEFG EFG FG GH GH HI 29