POSSIBILITIES FOR POST-EMERGENCE WEED CONTROL IN SORGHUM (Sorghum vulgare PERZ.) Hanna Gołębiowska, Krzysztof Domaradzki

,, 7-16 POSSIBILITIES FOR POST-EMERGENCE WEED CONTROL IN SORGHUM (Sorghum vulgare PERZ.) Hanna Gołębiowska, Krzysztof Domaradzki Institute of Soil Science and Plant Cultivation National Research Institute in Puławy 1 Abstract. Sorghum is a marginal plant in the sowing structure, therefore there is no chemical protection against its weed infestation. The usefulness of herbicides and their mixtures in weed control in maize, a plant related in origin to sorghum, provides the possibility of their use, if their selectivity is demonstrated in this crop. For this reason, before setting up field experiments, three series of biological tests were performed with several herbicides in a greenhouse. On the basis of evaluation of phytotoxic effects of herbicides and their mixtures, four most selective ones were selected for further field trials and applied in two different soil stands: phaeozem and lessive soil. Field experiments were conducted in the years 2009-2011 with randomized block design near Wroclaw. The obtained results indicated that on both soil stands, tritosulfuron + dicamba with an adjuvant was the most effective in selective control of weeds with high proportions of Chenopodium album, Solanum nigrum and Viola arvensis. Key words: dicamba, marginal plant, phytotoxic effect, selectivity of herbicides, tritosulfuron INTRODUCTION Sorghum (Sorghum vulgare PERZ.) belongs to the family of true grasses (Poaceae), just as maize. A significant feature of both sorghum and maize is their effective photosynthesis, which uses the so called C4 pathway. Under conditions of warm summer and sufficient amount of water, sorghum indicates significantly higher increase in green matter than maize [Śliwiński and Brzóska 2006]. Climate conditions in Poland meet requirements of sorghum which, from the moment of sowing until harvest, needs a sum of effective temperatures from 1600 to 1900 o C [Songin 2003]. Sorghum sown in wide row spacing is sensitive to weed infestation, especially at the initial stage of growth. In the register of products for weed control there are no Corresponding author Adres do korespondencji: dr Hanna Gołębiowska, Department of Herbology and Soil Tillage Techniques of Institute of Soil Science and Plant Cultivation National Research Institute in Puławy, Czartoryskich 8, 24-100 Puławy, e-mail: h.golebiowska@iung.wroclaw.pl

8 H. Gołębiowska, K. Domaradzki herbicides for weed control in sorghum, therefore, in practice, preparations for maize plantations are used. However, many of these substances are less selective, therefore using them before emergences should be safer and may give better results than treatments applied during plant vegetation [Kaczmarek et al. 2009]. Unfortunately, there are very few pre-emergence preparations registered for maize cultivation, and even they may show low selectivity towards sorghum, hence the need to work out recommendations for weed control in this crop plant taking into consideration also post-emergence weed control [Adamczewski et al. 2006]. Overview of active substances carried out in recent years in the European Union caused that the list of preparations for application on minor crop areas, which includes sorghum, is getting shorter, and in the case of plants of high commodity value or feed value, there is often lack of them. After another approval of active substances, many of them are limited only to major crop areas, with regard to intensifying requirements that are raised by the legislator. Another reason is lack of economic justification for producers of these substances for conducting long-term costly research on crops which will not bring repayment of expenditure. It is assumed that in sorghum cultivation, which is classified in the same taxonomic unit as maize, the same herbicides may be applied, if their selective and effective destruction of weeds will be proved. The aim of the research carried out in the years 2009-2011 was elaboration of an effective method of chemical regulation of weed control in sorghum cultivation through a proper selection of herbicides or herbicide mixtures, applied once or in a system of divided doses, depending on weed species diversity. MATERIAL AND METHODS Before starting and setting up field experiments in 2009, three series of biological tests were conducted in a greenhouse of the Department of Herbology and Soil Tillage Techniques of IUNG PIB in Wroclaw. Experiments were carried out under conditions of a controlled moisture level of soil, air and temperature. Their aim was evaluation of the phytotoxic effect of 11 herbicides and their mixtures used in maize protection at recommended doses, once or with a method of divided doses on hybrid cultivar of sorghum (Sorghum bicolor), Rona-1. Dates and doses of applied preparations are given in the result tables. Seeds of the crop plants were sown into pots of a capacity of 5 dm 3. The pots were filled with a mixture containing peat and sand at the proportion 2:1. The experiments were carried out in three replications under the following conditions: day length 14 hours, night length 10 hours, temperature 21 o C and light radiation 250 µmole m -2 s -1. After sowing and germination of seeds, plant thinning was carried out, leaving 5 plants in each pot. Herbicide treatment was conducted in the greenhouse spray chamber Aporo, equipped with a mobile head with a nozzle type TeeJet XR 11003 VS, providing maintanance of a constant working pressure of a value of 0.25 MPa, as well as of a spraying fluid consumption on the level of 250 dm 3 ha -1. With 1-week intervals, the evaluation of phytotoxic effect of herbicides was conducted four times with the use of a 9-degree bonitation method, where 1 denotes lack of a response of a crop plant, while 9 its complete destruction, also the type and degree of damage is given. After 4 weeks from the date of herbicide application, the fresh matter of

Possibilities for post-emergence... 9 the aboveground plant parts was determined in each pot, as well as the average yield of fresh plant matter. Based on the loss of fresh matter between plots treated with herbicides and the control plot (without herbicide application), effect of phytotoxic activity of studied preparations on a crop plant was determined, which allowed for selecting the safest herbicide combinations for tests under conditions of field experiments. The field experiments were set up with a randomized block design in four replications, in a 3-year cycle, on fields of individual farms (50 o 96 N; 16 o 88 E) on wrocław phaeozem soil classified in the 1st complex of agricultural usefulness, with a humus content of 3.6% and ph 6.3, as well as on brown soils (51 o 07 N; 17 o 02 E) included in the good rye complex, ph 5.6, and organic matter content being 2.3%. In the field experiments, usefulness of chosen herbicides was evaluated in the cultivation of a hybrid cultivar of sorghum Rona-1. Sorghum was sown to a depth of 3.5 cm in the second half of May, when the air temperature stabilized on the level of 10-12 o C. Sowing density of sorghum was 220,000 seeds ha -1, with a row spacing of 75 cm and seed distance in a row being 6.0 cm. Herbicidal effectiveness was determined with a visual method, expressed as a percentage in relation to the control plot, with no chemical protection against weeds. On control plots, the weeds were determined and calculated on randomly selected surfaces of an area of 1 m 2 with a frame method. Weather conditions in the years 2009-2011 were favorable for sorghum cultivation. Totals of effective temperatures from 1786 to 1992 o C as well as uniform moisture content especially in the seasons of 2010 and 2011, allowed for achieving full maturity in sorghum and conducting harvest from each plot in the second decade of September. The least favorable weather conditions, high temperatures and irregular rainfall distribution as well as slight delay in harvest was characteristic only of season 2009. During harvest, an average yield of the dry matter of plants was determined for the studied plots. Evaluation of selectivity of the tested herbicide combinations was done based on analyses of phytotoxicity of the preparation, 7, 14 and 21 days after the treatmen, and on estimating the dry matter yield of whole plants in dt ha -1. Analysis of variance was used for statistical elaboration of the results, while significance of differences was tested with the use of the Tukey confidence limits, for the significance level of 0.05. RESULTS Evaluation of herbicide combinations applied in the cultivation of sorghum Herbicides of high selectivity and effectiveness registered for maize cultivation proved to be less safe in the cultivation of sorghum. Evaluation of herbicide effect on the hybrid cultivar of sorghum, Rona-1, under conditions of greenhouse test, indicated a strong phytotoxicity of pendimethalin, s-metolachlor, acetochlor, thiencarbazone- -methyl with isoxaflutole, flufenacet with isoxaflutole, applied before emergence. Damage symptoms consisting in a strong inhibition of germination and of the seedling growth, as well as in the plant deformation were the reason for their elimination from field experiments (Table 1). Definitely, the highest fresh matter yield was obtained from post-emergence plots, from which the most selective ones were chosen for field experiments: MCPA with dicamba, tritosulfuron with dicamba with the addition of mineral oil as an adjuvant Atpolan 80 EC, acetochlor as well as florasulam with 2,4-D applied in a divided dose system (Table 1).

10 H. Gołębiowska, K. Domaradzki 10 H. Gołębiowska, K. Domaradzki Table 1. Evaluation of phytotoxic effect of herbicides on sorghum plants under greenhouse conditions Tabela 1. Ocena fitotoksycznego oddziaływania herbicydów na rośliny sorgo w warunkach testu szklarniowego Active ingredient Substancja aktywna Time of application Termin aplikacji BBCH Dose per ha Dawka na ha F-phytotoxicity weeks after application F-fitotoksyczność tygodnie po zabiegu, 1-9* 1 2 3 4 height of plants wysokość roślin cm yield of green matter, g pot -1 plon zielonej masy, g wazon -1 Control Kontrola 1 1 1 1 10.2 3.33 Stomp 400 SC 4 2 (pendimetalin 330 g L -1 ) 00 3 dm 3 ow ow, zw 1 1 7.6 2.41 Dual Gold 960 EC 3 2 (s-metolachlor 960 g L -1 ) 00 1.3 dm ow 2 2 2 8.3 2.62 Guardian 840 EC 3 5 (acetochlor 840 g L -1 ) 00 2.5 dm 3 ow 2 1 1 6.2 2.25 Adengo 315 SC 3 5 3 2 2 (thiencarbazone-methylu 90 g + isoxaflutole 225 g L -1 ) 00 0.33 dm 3 ow, zk. zs, zw zs, zw zs, zw 7.7 1.82 Boreal 58 WG 7 5 5 4 (flufenacet 48% + isoxaflutole 10%) 00 0.75 kg 7 ow, zk, zs zk, zs zk, zs zk, zs 3.51 1.58 Guardian Max 840 EC (acetochlor 840 g L -1 ) Chwastox Turbo 340 SL (MCPA 300 g + dicamba 40 g L -1 ) Emblem 20 WP (bromoxynil 20%) Mocarz 75 WG + Atpolan 80 EC (olej mineralny) (tritosulfuron 250 g + dicamba 500 g kg -1 ) + mineral oil adiuvant Mustang 306 SE (florasulam 6.25 g + 2.4-D 452 g L -1 ) Milagro 040 SC + Callisto 100SC (nicosulfuron 40 g + mezotrione 100 g L -1 ) 11 2.5 dm 3 3 chl, zw 2 lz, zw 2 1 8.9 2.72 11 2 dm 3 1 1 1 12.52 3.7 12 1.5 kg 3 def, zw 12 12 + 14 12 + 14 3 def, zw 2 zw 2 4.68 1.81 0.2 kg 1.5 dm 3 1 1 1 1 10.7 3.59 0.3 dm 3 0.3 dm 3 1 1 1 1 9.54 3.82 0.8 + 1.0 4 dm 3 b, zw 3 2 1 7.5 2.15 LSD0.05 NIR0,05 0.511

Possibilities for post-emergence... 11 Possibilities for post-emergence... 11 * 1 no effect on crop brak działania na roślinę uprawną, 9 damaged crop zniszczenie rośliny uprawnej BBCH 00 directly after crop sowing bezpośrednio po siewie BBCH 11 at 1-2 leaf stage of sorghum w fazie 1-2 liści sorga BBCH 12 at 3-4 leaf stage of sorghum w fazie 3-4 liści sorga BBCH 14 at 5-6 leaf stage of sorghum w fazie 5-6 liści sorga Symptoms of phytotoxic effect of herbicides on sorghum plants Symptomy fitotoksycznego oddziaływania herbicydów na rośliny sorgo zk germination inhibition zahamowanie kiełkowania lz leaf curling liściozwój ow delay of emergence opóźnienie wschodów def deformation of plants deformacje roślin zs wilting of seedlings zasychanie siewek pl spotting plamistość chl leaf chlorosis chloroza liści b bleaching bielenie t turgor loss utrata turgoru roślin zw growth inhibition zahamowanie wzrostu

12 H. Gołębiowska, K. Domaradzki Results of the evaluation of selectivity and effectiveness of preparations selected for field experiments indicate that before and after emergences, MCPA with dicamba may -1 be safely used in the form of a herbicide Chwastox Turbo 340 SL at a rate of 2 dm 3 ha and shortly after emergence, until the 3-leaf stage in sorghum tritosulfuron with dicamba in the form of a herbicide Mocarz 75 WG along with an adjuvant Atpolan 80 EC at a rate of 0.2 kg + 1.5 dm 3 ha -1, and later also florasulam with 2,4-D in the form of a herbicide Mustang 306 SE at a rate of 0.6 dm 3 ha -1. However, these preparations were not effective in destroying monocotyledonous species more abundant on lessive soils. On the other hand, they satisfactorily eliminated dicotyledonous species with a large proportion of Chenopodium album, Solanum nigrum or Viola arvensis, especially on phaeozem plots. Acetochlor under field conditions, proved to be the least selective, causing growth inhibition and slight plant deformations, more visible on lessive soils. Tritosulfuron with dicamba applied along with an adjuvant Atpolan 80 EC, proved to be the most useful for the regulation of weed community in the cultivation of sorghum on both soil stands. Also, no phytotoxic effect of this preparation was observed on sorghum plants (Tables 2, 3). Moreover, the highest average dry matter yield of whole plants per 1 ha was obtained on this plot. DISCUSSION On 14 June 2011, Regulation of EU No 1107/2009 came into force, concerning placing on the market and use of plant protection products as well as control over their application and placing them on the market. This legal act predicts possibility of applying for a permission concerning the use of plant protection product in other crops than the ones indicated in the directions for use, if the proposer submits required documentation, justifying usefulness of the preparation as an effective and selective one in the crop not included in the label [Surawska and Rzeźnicki 2010]. From literature report it follows that even slight weed infestation at the early stages of growth may significantly reduce sorghum yields [Berenji and Dahlberg 2004]. High weed infestation with monocotyledonous species at the initial stage of crop plant growth may cause decrease in yields by over 20% [Kaczmarek et al. 2009]. Time, in which weed species accompany a crop plant is significant with regard to the competition between the crop plant and weeds, 20-day period free from weeds decreases the risk of sorghum yield reduction, and weeds emerging after that time do not significantly affect the yield level [Espinoza and Kelly 2006]. While it is true that treatments preparing for sowing of sorghum do affect reduction of weed occurrence, they give no guarantee for obtaining satisfactory yields, therefore, application of herbicides in this crop is essential [Skrzypczak et al. 2008]. High forage yields and impressive appearance of some forms of sorghum observed on experimental fields, make the plant arouse more interest, especially in breeders of cattle and in bioenergetics, and its cultivation area increases rapidly, now exceeding 5,000 ha [Michalski 2009]. Increase in temperature compared with means from the long-term period [Zawora and Ziernicka-Wojtaszek 2005] as well as the risk of periodic droughts gives more beneficial than maize possibilities of using sorghum for biomass, thus its importance will be increasing in the next few years. Simpler possibilities of off label herbicide registration may provide that in a crop such as sorghum, obtaining satisfactory yields will never be at risk because of inaccessibility of products protecting against weeds.

Possibilities for post-emergence... 13 Possibilities for post-emergence... 13 Table 2. Effectiveness of selected herbicides in mono- and dicotyledonous weed on lessive soils and their influence on the yield of sorghum (2009-2011) Tabela 2. Skuteczność wybranych herbicydów w stosunku do chwastów jedno- i dwuliściennych występujących na glebach płowych i ich wpływ na plonowanie sorga (2009-2011) Treatment Obiekt Time of application Termin aplikacji BBCH Dose per ha Dawka na ha F 1-9 BBCH Weed control Zniszczenie chwastów % Dry matter yield of whole plants Plon suchej masy całych roślin Mg ha -1 ECHCG CHEAL VIOAR Other Pozostałe 14 18 22 Control Kontrola 1 1 1 *28 *14 *38 *24 1.43 Chwastox Turbo 340 SL (MCPA 300 g + dicamba 40 g L -1 ) 11 2 dm 3 1 1 1 56 82 89 88 2.24 Guardian Max 840 EC 3 (acetochlor 840 g L -1 ) 11 2.5 dm 3 4 3 3 84 100 88 93 1.57 Mocarz 75 WG + Atpolan 80 EC (olej mineralny) 0.2 kg (tritosulfuron 250 g + dicamba 500 g kg -1 12 ) + mineral oil adiuvant + 1.5 dm 3 1 1 1 82 100 81 100 2.95 Mustang 306 SE 0.3 dm 3 (florasulam 6.25 g + 2.4-D 452 g L -1 12 + 14 ) + 0.3 dm 3 3 2 1 63 93 88 92 2.07 LSD0.05 NIR0,05 0.595 F phytotoxicity in the scale 1-9 fitotoksyczność w skali 1-9 * number of weeds per m 2 liczba chwastów, szt. m -2 CHEAL Chenopodium album, ECHCG Echinochloa crus-galli, VIOAR Viola arvensis

14 H. Gołębiowska, K. Domaradzki 14 H. Gołębiowska, K. Domaradzki Table 3. Effectiveness of selected herbicides in mono- and dicotyledonous weeds on phaeozems and their influence on the yield of sorghum (2009-2011) Tabela 3. Skuteczność wybranych herbicydów w stosunku do chwastów jedno- i dwuliściennych występujących na czarnych glebach i ich wpływ na plonowanie sorga (2009-2011) Treatment Obiekt Time of application Termin aplikacji BBCH Dose per ha Dawka na ha F 1-9 BBCH Weed control Zniszczenie chwastów % Dry matter yield of whole plants Plon suchej masy całych roślin Mg ha -1 ECHCG CHEAL SOLNI AETCY Other Pozostałe 14 18 22 Control Kontrola 1 1 1 *18 *14 *9 *4 *7 1.62 Chwastox Turbo 340 SL (MCPA 300 g + dicamba 40 g L -1 ) 11 2 l 1 1 1 66 87 93 87 89 2.89 Guardian Max 840 EC (acetochlor 840 g L -1 ) 11 2.5 l 3 2 1 87 86 98 87 92 1.97 Mocarz 75 WG + Atpolan 80 EC (olej mineralny) 0.2 kg + (tritosulfuron 250 g + dicamba 500 g kg -1 12 ) + mineral oil adjuvant 1.5 dm 3 1 1 1 72 100 85 90 100 3.20 Mustang 306 SE 0.3 dm 3 (florasulam 6.25 g + 2.4-D 452 g L -1 12 + 14 ) + 0.3 dm 3 2 1 1 63 93 88 90 92 2.86 LSD0.05 NIR0,05 0.426 F phytotoxicity in the scale 1-9 fitotoksyczność w skali 1-9 * number of weeds per m 2 liczba chwastów, szt. m -2 ECHCG Echinochloa crus-galli, CHEAL Chenopodium album, SOLNI Solanum nigrum, AETCY Aethusa cynapium

Possibilities for post-emergence... 15 CONCLUSIONS 1. Severe symptoms of inhibition of germination and growth as well as deformations of sorghum plants indicated in biological tests were the reason for eliminating from field experiments pendimethalin, s-metolachlor, acetochlor, thiencarbazone-methyl with isoxaflutole, flufenacet with isoxaflutole, applied before emergence under greenhouse conditions. 2. The lowest phytotoxicity of herbicide combinations were obtained for post- -emergence plots, from which the most selective ones were chosen for field experiments: MCPA with dicamba, tritosulfuron with dicamba and adjuvant Atpolan 80 EC, acetochlor as well as florasulam with 2,4-D, applied in a system of divided doses. 3. Tritosulfuron with dicamba, applied along with an adjuvant Atpolan 80 EC, proved to be the most useful for the regulation of weed communities in the cultivation of sorghum, cultivar Rona-1, on both soil stands and had no phytotoxic effect on the crop plant, which allowed for obtaining the highest yield of the dry matter of plants. REFERENCES Adamczewski K., Gnusowski B., Matyjaszczyk E., 2006. Małoobszarowe uprawy rolnicze a chemiczna ochrona roślin [Chemical plant protection in minor agricultural crops]. Prog. Plant Protection/Post. Ochr. Roślin 46(1), 55-62 [in Polish]. Berenji J., Dahlberg J., 2004. Perspectives of Sorghum in Europe. J. Agron. Crop Sci. 190, 332-338. Espinoza L., Kelly J., 2006. Grain sorghum production handbook. http://www.uaex.edu/ Other_Areas/publications/HTML/MP-297.asp Kaczmarek S., Matysiak K., Krawczyk R., 2009. Badania nad chemicznym odchwaszczaniem sorga zwyczajnego (Sorghum vulgare Perz.) [Studies of the chemical weed control in Sorghum vulgare Perz.]., Agricultura 8(1), 27-35, www.agricultura.acta.utp.edu.pl [in Polish]. Michalski T., 2009. Sorgo nowa roślina energetyczna [Sorghum: a new energy crop]. http://www.dsvpoznan.eu/doc/sorgo-en-autor-prof-michalski-dla-dsv-poznan.pdf]. (dostęp 22.06.2010) [in Polish]. Songin H., 2003. Rośliny pastewne niemotylkowe [Non-leguminous forage]. [In]: Szczegółowa uprawa roślin, ed. Z. Jasińska i A. Kotecki, Wyd. AR Wrocław, 309-310 [in Polish]. Surawska M., Rzeźnicki B., 2010. Ustawodawstwo projekty ustaw i rozporządzenia z zakresu ochrony roślin [Legislation: bill drafts and regulations concerning plant production]. Mat. IX konf. Racjonalna technika ochrony roślin, IOR PIB Poznań, 9-17 [in Polish]. Skrzypczak W., Szulc P., Waligóra H., 2008. Efektywność zwalczania chwastów w sorgu [Effectiveness of weed control in sorghum]. Prog. Plant Protection/Post. Ochr. Roślin 48(2), 665-668 [in Polish]. Śliwiński B.J., Brzóska F., 2006. Historia uprawy sorga i wartość pokarmowa tej rośliny w uprawie na kiszonkę [History of sorghum cultivation and nutritive value of this plant in cultivation for silage]. Post. Nauk Rol. 1, 25-37 [in Polish]. Zawora T., Ziernicka-Wojtaszek A., 2005. Wpływ pogody i klimatu na działalność agrotechniczną i plonowanie roślin uprawnych na obszarze Polski [Impact of weather and climate on agroengineering and crop production in Poland]. Probl. Ekol. 9(5), 269-271 [in Polish].

16 H. Gołębiowska, K. Domaradzki POWSCHODOWE MOŻLIWOŚCI ELIMINACJI ZACHWASZCZENIA W UPRAWIE SORGA ZWYCZAJNEGO (Sorghum vulgare PERZ.) Streszczenie. Sorgo stanowi marginalną pozycję w strukturze zasiewów, dlatego brak jest chemicznej ochrony przed jego zachwaszczeniem. Przydatność chwastobójcza herbicydów i ich mieszanin stosowanych w kukurydzy, roślinie pokrewnej pod względem pochodzenia do sorgo, stwarza możliwość ich wykorzystania, jeżeli zostanie wykazana selektywność w tej uprawie. Z tego względu przed założeniem doświadczeń polowych wykonano trzy serie testów biologicznych w warunkach szklarniowych z udziałem kilkunastu herbicydów. Na postawie oceny fitotoksycznego oddziaływania herbicydów i ich mieszanin wybrano cztery najbardziej bezpieczne do dalszych doświadczeń polowych na dwóch odmiennych stanowiskach glebowych: glebie czarnej i płowej. Doświadczenia polowe prowadzone w latach 2009-2011 metodą losowanych bloków w okolicach Wrocławia wykazały, że na obu stanowiskach glebowych najbardziej selektywny i skuteczny w regulacji zachwaszczenia z dużym udziałem Chenopodium album, Solanum nigrum czy Viola arvensis okazał się tritosulfuron + dikamba z adiuwantem. Słowa kluczowe: dicamba, efekt fitotoksyczny, roślina marginalna, selektywność herbicydów, tritosulfuron Accepted for print Zaakceptowano do druku: 10.12.2012