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Journal of Plant Diseases and Protection Zeitschrift für Pflanzenkrankheiten und Pflanzenschutz Sonderheft XX, 935-940 (2006), ISSN 1861-4051 © Eugen Ulmer KG, Stuttgart Study on the early competition between sunflower and weeds in field experiments É. LEHOCZKY1*, P. REISINGER2, T. KŐMÍVES3, T. SZALAI4 1 Department of Herbology and Pesticide Chemistry, Georgikon Faculty of Agricultural Sciences, Veszprém University, Deák F.u. 16., H-8360 Keszthely, Hungary, e-mail: [email protected] 2 Department of Plant Protection, Faculty of Food and Agricultural Sciences, University of WestHungary, H-9200 Mosonmagyaróvár, Vár u. 2., e-mail: [email protected] 3 Plant Protection Institute of the Hungarian Academy of Sciences, H-1022 Budapest, Herman O. u. 15., e-mail: [email protected] 4 Department of Land Use and Landscape Management, Institute of Environmental Management, Szent István University, Páter K. u. 1., H-2103 Gödöllő, e-mail: [email protected] * Corresponding author Summary The aim of our study was to obtain concrete data on the competition of sunflower and weeds in the early stage of growth by measuring the biomass production of plants and to get further information on the rate of nutrient uptake of weeds under field conditions. The correlation between the biomass of weeds and sunflower was evaluated. The experimental results confirm that the importance of the early competition depends on the rate of weed infestation with special regard to the competition for nutrients. A field experiment was carried out at Baracska, Fejer county, Hungary, on a 9.2 ha area of calcareous loamy chernozem soil in 2004. Samples were taken five weeks after the sowing of sunflower at a growing stage of 8 paired leaves. Weed control was done end of April 2004 on the experimental field with herbicides as follows: Racer (fluorchloridon) 2 l/ha + Guardian Max (acetochlor + DK-29 safener) 2 l/ha + Prometrex 500 SC (prometryne) 2.2 l/ha. For the sake of competition studies no herbicides were applied further on sampling sites (2 x 2 m) that were identified by DGPS (Differential Global Positioning System). The populations of weeds growing on the sampling areas were assayed by using the Balázs-Ujvárosi coenological method and from six randomly selected sampling areas all weed and crop plants were harvested. Plants belonging to different taxa were separated, identified, counted, and the plants’ fresh and dry weights were measured. For comparison, sunflower plants were harvested from neighboring herbicide-treated sites and analyzed. Altogether 13 weed species were found such as Amaranthus blitoides, Amaranthus retroflexus, Ambrosia artemisiifolia, Bilderdykia convolvulus, Cannabis sativa, Chenopodium album, Chenopodium hybridum, Datura stramonium, Echinochloa crus-galli, Hibiscus trionum, Panicum miliaceum, Polygonum persicaria and Solanum nigrum. On average seven weed species were found per sampling site. As a result of crop-weed competition, the shoot mass of sunflower plants was 23.5 % lower on weedy sites than on herbicide treated sites (weed free). A negative linear correlation was found between the biomass weight of weeds and the shoot weight of sunflower. We found that uptake of large amounts of nutrients by weeds at the early stage of the development of sunflower is an important factor in crop-weed competition. As a result, the shoots of weed-free sunflower contained 22 % more nitrogen, 31 % more phosphorus and 43 % more potassium than those collected from weedy areas. Keywords: Crop-weed competition, biomass production, nutrient uptake, sunflower, DGPS 936 LEHOCZKY, REISINGER, KŐMÍVES, SZALAI Zusammenfassung Untersuchungen zur frühen Konkurrenz zwischen Sonnenblume und Unkräutern unter Feldbedingungen Untersuchungen zur Konkurrenz zwischen Sonnenblume und Unkräutern wurden 2004 auf einer Teilfläche von 17,8 ha eines 52 ha großen Sonnenblumenfeldes in Baracska (Lks. Fejér, Ungarn) auf kalkhaltigem Tschernosem durchgeführt. Die Probenahme erfolgte am 1. Juni, 5 Wochen nach der Saat. Zu diesem Zeitpunkt befand sich die Sonnenblume in einem Entwicklungsstadium mit 8-9 Blättern. Auf der Untersuchungsfläche wurde Ende April mit den Herbiziden Racer (Fluorchloridon) 2 l/ha + Guardian Max (Azetochlor + Antidotum) 2 l/ha + Prometrex 500 SC (Prometrin) 2,2 l/ha eine Unkrautbekämpfung durchgeführt. Auf den mit DGPS (Differenzielles Globales Positionssystem) markierten 2 × 2 m großen Versuchsparzellen wurde keine weitere Herbizidbehandlung vorgenommen. Auf diesen Flächen konnten sich sowohl die Kultur- als auch die Unkrautpflanzen „ungestört” entwickeln. An den Probenahmestellen wurden mit der Balázs-Ujvárosi Methode eine Unkrauterfassung durchgeführt. Anschließend wurden sämtliche dort vorkommende Unkrautpflanzen je nach Art gesammelt, abgezählt und schließlich die Frisch- und die Trockenmasse der Sprosse erhoben. Von den Probenahmestellen und aus dem herbizidbehandelten Umfeld wurden je 10 Sonnenblumen entnommen, ihre Blattanzahl, Sproßlänge, Frisch- und Trockenmasse ermittelt. Darüber hinaus wurde der Nährstoffgehalt (N, P, K) der entnommenen Sonnenblumen und der Unkräuter festgestellt. Es wurden insgesamt 11 annuelle dikotyle Unkrautarten registriert (Amaranthus blitoides, Amaranthus retroflexus, Ambrosia artemisiifolia, Bilderdykia convolvulus, Cannabis sativa, Chenopodium album, Chenopodium hybridum, Datura stramonium, Hibiscus trionum, Polygonum persicaria, Solanum nigrum) und zwei annuelle monokotyle Arten (Echinochloa crus-galli, Panicum miliaceum), alle mit dem Wärmeanspruch der Lebensform T4. Auf den Erfassungsflächen kamen durchschnittlich sieben Unkrautarten je Parzelle vor. Es war eine starke Konkurrenz zwischen Kultur- und Unkrautpflanzen zu beobachten, in deren Folge die Sprossmasse der Sonnenblumen auf den verunkrauteten Flächen um 23,5 % geringer war als auf den mit Herbiziden behandelten Flächen. Zwischen der Biomasse der Sonnenblumen und der Unkräuter konnte ein negativer linearer Zusammenhang nachgewiesen werden. Die Sonnenblumen auf den mit Herbiziden behandelten Flächen enthielten 22 % mehr Stickstoff, 31 % mehr Phosphor und 43 % mehr Kalium als die Sonnenblumen der unbehandelten Vergleichsflächen. Stichwörter: Konkurrenz, Sonnenblume, Biomasse, Nährstoffaufnahme, DGPS Introduction On cultivated areas, there is a constant competition between weeds and crops for nutrients, light and water. As far as densely-sown cultures are concerned, the winner of this competition is usually the crop, while in the case of loose-standing cultures, without human assistance, weeds are the winning competitors. In the early stage of their life cycles – i.e. as long as the vital factors required for their living are in abundance – weeds and crops are able to co-exist without causing any threat to each other. Living conditions will start to deteriorate when there is a shortage of nutrients, water and light. Today, the critical period of competition is known exactly for most crops. This is the time of major damage, influencing the entire vegetation period and having a great impact on yield volume and quality (BERZSENYI 2000, LEHOCZKY et al. 2004). In general, the critical period of competition are the first weeks or months of the vegetation period. In the case of maize, for instance, the beginning of this period is the third or fourth week after emergence. The critical period of competition was the subject of numerous studies in Hungary (DOBOZI-LEHOCZKY 2004, HUNYADI 1988, LEHOCZKY-BOROSNÉ NAGY 2002, LEHOCZKY 2002, VARGA et al. 2002, LEHOCZKY et al. 2004). According to these findings, certain weed species reduce crop yield and biomass production. The issue of competition between sunflower and weeds has not been extensively studied so far. It is common knowledge that by spreading of roots sunflowers are able to efficiently utilize even scarcely available sources of water and nutrients. Sunflower has a good weed-suppressing ability (LÁNG 1976). Early competetion between sunflower and weeds 937 The purpose of our study was to determine the level of competition for nutrients between sunflower and weeds in the early stage of growth and to contribute to the competition-related scientific knowledge base. Materials and methods A field experiment was performed on a calcareous chernozem soil (Tab. 1) at the Annamajor Farm of Baracska, Hungary, in the summer of 2004. The plot was cultivated with maize in the year preceding the experiment. Following the maize harvest, a deep ploughing was performed in autumn, and then a leveller and a cultivator were used to prepare the plot for sunflower sowing in spring of 2004. At the same time, a complex fertilizer (MAS) was applied at a rate of 175 kg/ha. The sowing of sunflower (Alexandra hybrid) was performed in April at a plant density of 53,000 plants/ha. The area was given a pre-emergent herbicide treatment with a combination of Racer 2.0 l/ha (fluorochloridon), Guardian Max 2.0 l/ha (antidoted acetochlor) and Prometrex 500 SC 2.2 l/ha (prometryne) soon after sowing. The harvest of sunflower took place in October and the average yield amounted to 3.6 tons/ha. For the sake of the competition studies, no herbicides were further applied on foil-covered sampling sites of 2 x 2 m, identified by DGPS, in order to ensure a “undisturbed” development for both crop and weeds on these control sites. Weed and crop samples were taken in June (5 weeks after the sowing of sunflower) at a growing stage of 8-9 paired leaves. The populations of weeds growing in the sampling areas were assayed by using the Balázs-Ujvárosi coenological method (UJVÁROSI 1973, REISINGER 2001). After that all weeds on such areas were collected. Plants belonging to different taxa were separated, identified, counted, and fresh and dry weights were determined. Ten sunflower plants were collected both from the sampling areas and from the herbicide-treated surrounding areas. The concentrations of different macronutrients (N, P, K % in dry matter) of the plant samples were examined. Tab. 1: Soil properties of the project area [means (±variances)]. Tab. 1: Bodeneigenschaften der Versuchsfläche [Mittelwerte (±Varianz)]. Type FAO USDA Texture Calcaric phaeosem Mollisol Loam Organic matter [%] CaCO3 [%] AL-P2O5 AL-K2O pH [mg kg-1] [mg kg-1] 3.2 [0.83] 7.5 [1.8] 5.7 [1.2] 283 [54] 314 [39] On a total area of 9.2 ha 21 sampling sites were marked (at a frequency of 0.5 ha). All weeds on six of such sites were collected by variety, their numbers were counted and then the fresh and dry weights were measured. The mathematical-statistical analysis of the data was done by MS Excel and ANOVA-SPSS. Results Weeds Altogether 13 (two monocotyledonous and 11 dicotyledonous) weed species were found, all of them being heat-demanding T4 weeds. Each sampling site (plot) contained an average of seven weed species (Tab. 2). The weeds present on the sampling sites had an average density of 152 plant m-2, representing a wide scale from 66 to 340 plant m-2. The two dominant species, Datura stramonium and Panicum miliaceum, were present on each plot and showed a significant density and a high biomass production. 938 LEHOCZKY, REISINGER, KŐMÍVES, SZALAI Tab. 2: Weed species present on the sampling sites, listed by occurrence and density (plant m-2). Tab. 2: Unkrautarten auf den Probennahmeflächen, aufgelistet nach Vorkommen und Dichte (Pflanzenanzahl m-2). Range 1. 1. 1. 2. 2. 3. 3. 4. 4. 4. 5. 5. 5. Minimum Maximum Average Density (plants m-2) 16 155 70 Datura stramonium 3 154 53 Panicum miliaceum 2 55 14 Cannabis sativa 3 16 5 Chenopodium hybridum 2 7 3 Amaranthus retroflexus 1 2 0.4 Amaranthus blitoides 10 27 6 Solanum nigrum 4 24 4.5 Chenopodium album 0.5 1 0.3 Polygonum persicaria 1 3 0.5 Echinochloa crus-galli 0 1 0.04 Ambrosia artemisiifolia 0 1 0.04 Bilderdykia convolvulus 0 1 0.1 Hibiscus trionum Weed species Biomass production The total average biomass weight of the weeds present on the sampling sites amounted to 16.16 g m-2, which was similar to the average dry biomass weight of 16.69 g m-2 obtained for the sunflower plants coexisting with weeds (Tab. 3 and 4). The dry biomass weight of sunflower plants living on the weedy sampling sites ranged between 11.24 and 19.24 g m-2. Within the total vegetable (weeds+sunflower plants) biomass production per unit area, the share of sunflower accounted for 26-81 %. Sunflower showed a significantly (by 23.8 %) lower biomass production on weedy plots than on the herbicide-treated areas. The average dry biomass weight of sunflower on herbicide-treated areas was 21.84 g m-2, which is one-third higher (31 %) than the same value measured on the untreated areas. A negative linear correlation was found between the biomass weight of weeds and the shoot weight of sunflower (Fig. 1). According to the relationship analysis, 1 g of dry weed biomass caused a reduction of 0.37 g in the shoot weight of sunflower per m2. Tab. 3: Average fresh and dry weight of weeds present on the sampling sites. Tab. 3: Frisch- und Trockengewicht der Unkräutern auf den Probenahmeflächen. Fresh shoot weight Dry matter weight (g m-2) 1 Panicum miliaceum 51.77 7.62 2 Datura stramonium 25.40 3.52 3 Cannabis sativa 14.36 3.47 4 Chenopodium hybridum 3.22 0.43 5 Amaranthus retroflexus 1.49 0.50 6 Amaranthus blitoides 0.27 0.05 7 Solanum nigrum 1.26 0.19 8 Chenopodium album 2.93 0.43 9 Polygonum persicaria 0.50 0.08 10 Echinochloa crus-galli 0.21 0.04 11 Ambrosia artemisiifolia 0.02 0.01 12 Bilderdykia convolvulus 0.03 0.01 13 Hibiscus trionum 0.04 0.01 Total 101.50 16.16 Weed species Early competetion between sunflower and weeds 939 2 sunflower dry biomass g/m 2 25 20 15 10 y = -0.3679x + 22.623 2 r = 0.8974 5 0 0 5 10 15 20 25 30 35 2 weed dry biomass g/m Fig. 1: Relationship between the dry biomass weights of sunflower and weed plants. Abb. 1: Beziehung zwischen den Trockenmassen von Sonnenblume und Unkräutern. Nutrient uptake The shoot weight of sunflower was 31 % higher on the herbicide-treated areas than on the untreated plots. As to nutrient uptake, the shoots of weed-free sunflower contained 22 % more nitrogen, 31 % more phosphorus and 43 % more potassium than those collected from the weedy areas (Tab. 4). Tab. 4: Biomass production and nutrient uptake (N, P, K) of sunflower on weed-free plots, sunflower on weedy plots and weeds. Tab. 4: Biomasse und Nährstoffgehalt (N, P, K) der Sonnenblumen auf den mit Herbiziden behandelten Flächen bzw. auf den verunkrauteten Flächen und der Unkräuter. Treatment Sunflower on weed free plots Sunflower on weedy plots Weeds Dry biomass weight 21.84 16.69 16.16 N content (g m-2) 0.537 0.441 0.475 P content K content 0.068 0.052 0.044 0.954 0.668 0.644 As to the nutrients taken up altogether by weeds and sunflower plants on the weedy areas, the share of potassium was similar to that of biomass production: 49 % for sunflower and 51 % for weeds. However, weeds contained 52 % and 46 % of the total uptake of nitrogen and phosphorus, respectively. The level of nutrient uptake per unit area was almost the same for weeds as for the sunflower plants co-existing with weeds. As a result of competition, the percentage of potassium uptake in sunflower plants was higher than that of biomass production: it decreased by 30 %. Conclusions The experimental plot was dominated by weed species such as Datura stramonium, Panicum miliaceum and Cannabis sativa. The weeds showed almost the same weight per unit area (g m-2) as the sunflower plants. 940 LEHOCZKY, REISINGER, KŐMÍVES, SZALAI In the case of heavy weed infestation, a competition period of only five weeks may cause a significant drop in sunflower biomass production. According to the study results, the dry biomass weight of sunflower shoots was 31 % higher on the herbicide-treated plots than on the weedy areas. Based on a regression analysis, a negative linear relationship was found between the biomass weight of weeds and the biomass production of sunflower: 1 kg of dry weed caused a reduction of 370 g in the shoot weight of sunflower. As to nutrients, the uptake of nitrogen showed the smallest difference between the weed-free and weedy sunflower plants: the former contained 22 % more nitrogen than the latter. There was a strong competition for nitrogen between weeds and sunflower plants: weeds contained 52 % of the nitrogen uptake that was more than their dry matter share (49 %). Sunflower needs a lot of potassium and, therefore, the potassium uptake of weed-free sunflower was 43 % higher than that of weedy sunflower. References BERZSENYI, Z.: Gyomszabályozási stratégiák a fenntartható növénytermesztésben. Magyar Gyomkutatás és Technológia 1, 3-21, 2000. HUNYADI, K.: Szántóföldi gyomnövények és biológiájuk. Mezőgazdasági Kiadó.Budapest, 358-380, 1988. LÁNG, G.: Szántóföldi növénytermesztés. Mezőgazdasági Kiadó Budapest, 240-247, 1976. LEHOCZKY, É.: Az Echinochloa crus-galli (L.) P.B. és a kukorica korai kompeticiójának hatása.. II. A növények tápanyag felvétele. Magyar Gyomkutatás és Technológia 3, 21-30, 2002. LEHOCZKY, É., A. BOROSNÉ NAGY: Az Echinochloa crus-galli (L.) P.B. és a kukorica korai kompetíciójának hatása. I. A növények növekedése. Magyar Gyomkutatás és Technológia 3, 13-20, 2002. LEHOCZKY, É., P. REISINGER, T. KŐMÍVES: Loss of nutrients caused by excessive weediness at the early stage of maize vegetation period. Communications in Soil Science and Plant Analysis 36, 415-422, 2004. DOBOZI, M., É. LEHOCZKY: Competition for nutrients between weeds and potato. Zeitschrift für Pflanzenkrankheiten und Pflanzenschutz, Sonderheft 19, 353-359, 2004. LEHOCZKY, É., P. REISINGER, S. NAGY, T. KŐMÍVES: Early competition between maize and weeds in the field. Zeitschrift für Pflanzenkrankheiten und Pflanzenschutz, Sonderheft 19, 319-324, 2004. UJVÁROSI, M: Gyomnövények, gyomirtás. Mezőgazdasági Kiadó Budapest. 1973 (in Hungarian). REISINGER, P: Weed survey on farmlands in Hungary (1947-2000). Magyar Gyomkutatás és Technológia 2, 3-13, 2001. VARGA, P., I. BÉRES, P. REISINGER: Gyomnövények hatása a kukorica termés-eredményére szántóföldi kísérletekben. Magyar Gyomkutatás és Technológia 1, 45-52. 2000.