Efficacy of Cultivar Selectivity and Weed Control Treatments on Wheat Yield and Associated Weeds in Sandy Soils

The effect of some weed control treatments (Bifonex, Tribenuron-methyl, hand weeding and unweeded check), five wheat cultivars (Sakha 69, Sids 6, Sids 7, Sids 8 and Sids 9) and their interaction on the productivity of wheat plants and associated weeds were examined under the sandy soil conditions. The obtained data indicated that total dry weight/m2 recorded at 60 days from wheat sowing significantly lower with Sids cultivars than with Sakha 69 cultivar, where Sids 8 surpassed all cultivars in this respect. Un-controlling weeds in wheat field caused a significant reduction in wheat grain yield by 41%. The excellent control of weeds was achieved by hand weeding twice followed by tribenuron-methyl herbicide treatment. Under the weed competition condition; Sids 9 cultivar produced the highest grain yield, while under weed free treatment; Sids 7 cultivar gave the maximum yield. The rank order of competitive ability of the five wheat cultivars was Sids 9> Sakha 69> Sids 8> Sids 7> Sids 6. Therefore planting Sids 7 cultivar and controlling weeds by hand or tribenuron-methyl herbicide produced the highest yield. Key word: Tribenuron-methyl Bifenox Competitive ability Wheat Cultivars Weeds INTRODUCTION Several researchers have shown that tribenuronWeeds limit wheat yield potential in arid region [15-18]. High wages and scarcity of labors at right time because they increase evapotranspiration and compete make hand weeding difficult and uneconomical day by with wheat plants for limited soil moisture [1], water and day, especially in new reclaimed area. Some investigators light resulting in grain yield reduction amounted to 7% found positive effect for the interaction between cultivars [2], 52% [3], 92% [4] and in serious cases may lead to and weed control treatments on weeds and yield of wheat complete crop failure [5]. crop [13, 19]. Therefore, the objective of this study was to Use of aggressive cultivars can be effective cultural investigate the effect of cultivars and weed control practice for weed growth suppression [6, 7, 8]. According treatments as well as their interaction on wheat yield and to Bussan et al. [9] the competitive ability of crop can be associated weeds under sandy soil conditions. expressed in two ways. First is the ability of the crop to compete with weeds, reducing weed seed and biomass MATERIALS AND METHODS production. The second possibility is having crop tolerate competition from weeds, while maintaining high yields. Two field experiments were performed in a private Hucl [10] found that the less competitive genotypes farm, during 2006/2007 and 2007/2008 winter seasons in a suffered a 7-9% greater yield loss than that of the more sandy loam soil to evaluate the effect of five wheat competitive genotypes. On the other hand, Cardina [11] cultivars and four weed control treatments on wheat yield concluded that more competitive cultivars are not and related weeds. Five wheat cultivars were Sakha necessarily higher yielding. Mason et al., [12] reported 69, Sids 6, Sids 7, Sids 8 and Sids 9, while the weed control that tallness and early heading and maturity were related treatments were: Bifenox (Modown 4 F 48% EC) herbicide to increase grain yield at the highest weed level. Greater [( Methyl 5(2,4 dichlorophenoxy )-2nitrobenzoate], spikes/m , tallness and early heading were associated with applied at the rate of 0.6 l/fed after 28 days after wheat 2 reduced weed biomass, depending on weed level. The sowing (DAS), Tribenuron-methyl (Granstar 75 DF) response of wheat plants to herbicides also varied among [Methyl 2-(((N(4-methoxy 6 methyl 1 , 3 , 5 triazin 2 cultivars [13, 14]. Y) methylamine ) caronyl ) amino ) sulful ) benzoate ] methyl and bifenox herbicides can control weeds in wheat World J. Agric. Sci., 4 (3): 384-389, 2008 385 herbicide, applied at the rate of 8 g/ fed at 28 DAS, hand oats (Avena fatua L.) as grass. Sids 8 cv plants weeding (twice at 28 and 49 DAS) and unweeded check suppressed weed growth by more than 80%, compared (allowing weeds to grow with wheat plants until harvest). to Sakha 69 cv., while Sids 7 cv. suffered from the weeds The experimental design was a spilt plot design with than others Sids cultivars (Table 1). Previous studies have 4 replicates, 5 cultivars were located in the main plots, shown that some wheat cultivars are more competitive while the weed control treatments were occupied in than others [8, 21, 22]. The difference in the ability of sub-plots. cultivars to suppress weed growth than other might be Wheat cultivars seeds were sown on the third due to the differential rooting patterns, allelochemicals week of November in both seasons, using a constant production, higher leaf area index and more light seeding rate (80 kg/fed). Plot area was 12 m2. The normal interception, tillering capacity and vegetative growth cultural practices for growing wheat were applied as habit [6, 23]. recommended. The crop received 90, 22.5 and 24 of Concerning the effect of weed control treatments on N, P O and K O kg /fed and preceded by maize weeds, data in Table 1 indicated that application of 2 5 2 (Zea mays L) in both seasons. After 75 DAS, weeds were tribenuron methyl herbicide resulted in marked reduction counted from one square meter randomly taken from in the dry weight of weeds when compared with hand each plot. Weeds were identified and their dry weights weeding, bifenox and unweeded treatments. The lowest were recorded. At harvest, a plant sample of one square weed control efficiency of hand weeding than meter from each plot was taken to determine number of tribenuron –methyl herbicide was due to the fact that tillers/m2, number of grains per spike and grain index hand weeding removes interrow weeds only, while the (1000 grains weight). Biological and grain yields per weeds within the crop rows and immediate vicinity of the feddan were determined by harvesting the whole plot wheat plants are not removed. area. (Feddan (fed.) = 4200 m ). Results in Table 1 revealed that the interaction 2 Combined analysis of data for the two growing between treatments had insignificant effect on weeds seasons was carried out according to Snedecor and in most cases, except on the total dry weight of weeds Cochran, [20]. For comparison between means, L.S.D. test as shown in Table 3. The lowest number and dry at 5% level was used. weight of weeds were achieved by sowing Side 8 cv. and using tribenuron methyl herbicide (Table 3). Similar RESULTS AND DISCUSSION results on the significant interaction between the Effect of Treatments on Weeds: The dominant weeds in weeds by tribenuronmethyl were reported with the unweeded plot at 60 days after wheat sowing Christensen [22]. From the data in Table 3 broadcasting (Table 1) were prickly dock (Emex spinosa(L.) Campd), Sids 8 cultivar and controlling weeds by tribenuronblack mustard (Brassica nigra L (Koch)), scorlet methyl herbicide reduced the total number and dry pimpernel (Anagallis arvensis L.) and lambsquarters weight of weeds to the lowest level compared to the other (Chenopodium album L.) as broad leaf weeds and wild interaction treatments. competitive ability of wheat cultivar and controlling Table 1: Effect of wheat cultivars, weed control treatments and their interaction on dry weight of weed species (g/m2) after 60 days from wheat sowing (Combined analysis of two seasons) Treatments Emex spinosa Brassica nigra Anagallis arvensis Chenopodium album Avena fatua Total