SEASONAL DYNAMIC OF WEED BIOMASS IN NARROW AND WIDE ROW SOYBEAN (GLYCINE MAX (L.) MERR.)

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1 Herbologia, Vol. 16, No. 2, 2017 DOI: /Herb SEASONAL DYNAMIC OF WEED BIOMASS IN NARROW AND WIDE ROW SOYBEAN (GLYCINE MAX (L.) MERR.) Edita Štefanić 1, Darko Dimić 2, Aleksandra Sudarić 3, Ivan Štefanić 1, Slavica Antunović 4 and Gordana Horvat 5 1 Faculty of Agriculture, J.J.Strossmayer University, V. Preloga1, Osijek, Croatia 2 PhD Student, Faculty of Agriculture, J.J. Strossmayer University, V. Preloga 1, Osijek, Croatia 3 Agricultural Institute Osijek, Južno predgrađe 17, Osijek 4 College of Slavonski Brod, Agricultural Department, Dr. Mile Budaka 1, Slavonski Brod, Croatia 5 former MS Student, Faculty of Agriculture, J.J. Strossmayer University, V. Preloga 1, Osijek, Croatia Corresponding author: estefanic@pfos.hr Abstract A field study was conducted over 3 years to compare weed biomass dynamic in narrow and wide row soybean (25, 50 and 70 cm rows). Weed community were comprised of 34 grass and dicot weed species of varied perennation, and dominance of Asteraceae and Poaceae families. Weed infestation differ throughout the experiment and among all determined species Amaranthus retroflexus, Chenopodium album, Setaria viridis and Sorghum halepense are the only weeds present in all years and row spacings. Although seasonal dynamic of weed biomass from sowing to harvest varied among each row spacing and years, planting soybean in wide rows reduces early-season crop tolerance to weeds. Keywords: soybean, row spacing, weed biomass, competition Introduction Crop-weed competition can vary depending on several factors. This include crop and weed characteristics (Buhler et al., 2008), environmental variables (Lindquist et al., 1998, Bauer et al., 1991), and cropping practices like crop plant density and row spacing (Hock et al., 2006). Moreover, row spacing can affect the time of canopy closure, and therefore influence the growth and development of both crop and weeds (Knezevic et al., 2003). Since successful weed management relies on matching control strategies to the specific weed problem on field, it is necessary to know not Copyright 2017 by the Academy of Sciences and Arts of Bosnia and Herzegovina.

2 Štefanić et al. only which weed (and how many) are present in the field, but also their distribution and development stages. Numerous studies have examined weed emergence, density and aggressivity, but there is little information on weed dry matter production. Therefore, the objective of this research was to evaluate floristic composition and compare the seasonal dynamic of weed biomass growing in narrow- and wide-row soybean. Materials and methods The field experiment has been conducted near Vukovar, at the family farm Zeleno polje. During study period (2014 to 2016), monthly rainfall varied in total amount and periodicity among years. Average daily temperatures for the 3-yr study were similar to the 20-yr averages (data not shown). Cropping practice, common for this region was applied in each year (Vratarić & Sudarić, 2007). Soybean cultivar IKA (Agricultural Institute Osijek) was grown in a randomized complete block design with four replications in three row spacing (25, 50 and 70 cm). The main plot was 2.5 x 3.5 m. A naturally occurring population of mixed weed species were allowed to develop for a different periods of time and then were carefully removed. Aboveground weed biomass samples were taken from 1 m 2 quadrat placed randomly in each plot. All weeds were counted by species and then dried at 70 0C to a constant mass and weighed. In order to determine weed biomass dynamics, dry weight were assessed in each row spacing eleven times during the growing season from crop emergence to crop maturity. The timing of weed removal was according to the soybean development stage. To analyze weed biomass dynamic over time, regression analysis was performed for each row spacing and year using SPSS for Windows, version 20, and results were presented graphically. Results and discussion Weed community present in this study was comprised of 34 species consisting of summer annuals, winter annuals, biannuals, perennials and volunteer crops (Table 1). The most numerous families were Asteraceae with 7 and Poaceae with 4 species. Differences in weed species composition were visible between years, of which first year had 26, second 18 and third experimental year only 15 weed species. Amaranthus retroflexus L., Chenopodium album L., Chenopodium hybridum L., Convlovulus arvensis L., Datura stramonium 64

3 Seasonal dynamic of weed biomass in narrow and wide row soybean L., Helianthus annuus L., Setaria viridis (L.) PB. and Sorghum halepense (L.) Pers. were weeds recorded in all three years of investigation. Those are, according to previous research, a typical row-crop weed flora of this territory (Stefanic et al., 2005, Konstantinović et al., 2008). Table 1. Floristic composition in soybean crop during the experiment. Plant species Plant family Func. Groups* Years of investigation Mf LC Abutilon theoprasti Med. Malvaceae D A Amaranthus retroflexus L. Amaranthaceae D A Ambrosia artemisiifolia L. Asteraceae D A Artemisia vulgaris L. Asteraceae D P Calystegia sepium (L.) R.Br. Convolvulaceae D P Chenopodium album L. Chenopodiaceae D A Chenopodium hybridum L. Chenopodiaceae D A Convolvulus arvensis L. Convolvulaceae D P Datura stramonium L. Solanaceae D A Daucus carota L. Apiaceae D B-A Erigeron annuus (L.) Pers. Asteraceae D A-B Erigeron canadensis L. Asteraceae D A Euphorbia helioscopia L. Euphorbiaceae D A Glechoma hederacea L. Lamiaceae D P Helianthus annuus L. Asteraceae D A Hordeum murinum L. Poaceae M A Lactuca seriola L. Cichoriaceae D A-B Lathyrus pratensis L. Fabaceae D P Matricaria chamomilla L. Asteraceae D A Oxalis corniculata L. Oxalidaceae D P Papaver rhoeas L. Papaveraceae D A Plantgo major L. Plantaginaceae D P Robinia pseudoacacia L. Fabaceae D P Rorippa sylvestris (L.) Bess. Brassicaceae D P Rumex cryspus L. Polygonaceae D P Setaria verticillata (L.) PB. Poaceae M A Setaria virisdis (L.) PB. Poaceae M A Solanum nigrum L. e. Miller Solanaceae D A Sonchus arvensis L. Cichoriaceae D P Sonchus oleraceus L. Cichoriaceae D A-B Sorghum halepense (L.) Pers Poaceae M P Urtica dioica L. Urticaceae D P Veronica persica Poir. Scrophulariaceae D A-B Xanthium strumarium L. Asteraceae D A TOTAL *Functional groups: Mf=morphotype, D=dycotyledonae, M=monocotyledonae, LC=life cycle, A=annual, B=bi-annual, P=perennial 65

4 Štefanić et al. However, weed infestation differ between row spacings. Among all determined species A. retroflexus L., C. album L., S. viridis (L.) PB. and S. halepense (L.) Pers. are the only weeds present in over years and row spacing (Table 2). Dominant weeds: Table 2. Dominant weeds in different soybean planting rows. Soybean planting rows 25 cm 50 cm 70 cm Amaranthus retroflexus Ambrosia artemisiifolia Chenopodium album Chenopodium hybridum Convolvulus arvensis Datura stramonium Helianthus annuus Setaria viridis Sorghum halepense The relationship between the development of aboveground weed biomass in three different row spacing (25, 50 and 70 cm) and days from sowing to harvest was described by the polynomial (quadratic) function (Figure 1, Table 3). Seasonal dynamic of weed biomass varied among each row spacing and years. Higher weed biomass at early stage was observed at planting soybean in wide rows (in 2015 and 2016). This could confirm results of Knezevic et al. (2003) that planting soybean in wide rows reduces early-season crop tolerance to weeds and requires earlier weed management programs. But, weed biomass production in 2014, in narrow planting soybean was dominant almost during the whole season, but weeds in 70 cm rows received significantly increase in second half of season. 66

5 Seasonal dynamic of weed biomass in narrow and wide row soybean Figure 1. Seasonal dynamics of weed biomass (g m -2 ) during the soybean growing period. Fitted models are presented in Table 3. 67

6 Štefanić et al. Table 3. Regression equations that describe the relationship of weed biomass development during the growing season between narrow- and wide-row soybeans. Year Row spacing Regression equation R y = 0,0413x 2 + 7,6725x 0, y = 0,0774x 2 + 2,1893x 0, y = 0,1427x 2 4,0406x 0, y = 0,0884x 2 + 2,9718x 0, y = 0,1016x 2 + 2,8194x 0, y = 0,0202x 2 + 8,1681x 0, y = 0,1437x 2 0,2060x 0, y = 0,0898x 2 + 2,6964x 0, y = 0,0767x 2 + 6,0639x 0,874 Conclusions Out of 34 species in soybean weed community, only Amaranthus retroflexus L., Chenopodium album L., Setaria viridis (L.) PB. and Sorghum halepense (L.) Pers. were present in all years and each row spacing. Seasonal dynamic of weed biomass from sowing to harvest varied among each row spacing and years. Wide row planting soybean requires earlier weed management program. References BAUER, T.A., MORTENSEN, D.A., WICKS, G.A., HAYDEN, T.A. & MARTIN, A.,1991: Environmental variability associated with economic thresholds for soybeans. Weed Sci. 39, BUHLER, D.D., HARTZLER, R.G., FORCELLA, F. & GUNSLOUS, J.L., 2008: Relative Emergence Sequence for Weeds of Corn and Soybean. Extension and Outreach Publications. Book 73. Iowa State University. HOCK, S.M., KNEZEVIC, S.Z., MARTIN, A.R. & LINDQUIST, J.L. 2006: Soybean row spacing and weed emergence time influence weed c o m - petitiveness and competitive indices. Weed Science 54 (1), KNEZEVIC, S.Z., EVANS, S.P. & MAINZ, M., 2003: Row Spacing Influences The Critical Timing for Weed Removal in Soybean (Glycine max). Weed technology 17, KONSTANTINOVIĆ, B., MESELDŽIJA, M. & KONSTANTINOVIĆ, B., 2008: Zastupljenost dominantnih vrsta korova soje u Vojvodini. Biljni lekar, Vol.36, LINDQIST, J.L., MORTENSEN, D.A. & JOHNSON, B.E., 1998: Mechanisms of corn tolerance and velvetleaf suppressive ability. Agron. J. 90, STEFANIC, E., STEFANIC, I. & MURDOCH, A.J., 2005: Response of a weed community to different management practice in field bean. Journal of Plant Desease and Protection, 112 (5) VRATARIĆ, M. & SUDARIĆ, A., 2007: Tehnologija proizvodnje soje. Poljoprivredni institut Osijek, Zvijezda d.d. Zagreb, Priručnik. 68