Competition indices of common vetch and cereal intercrops in two seeding ratio

A 2-year field study was conducted using common vetch (Vicia sativa L.), wheat (Triticum aestivum L.), triticale (xTriticosecale Wittmack), barley (Hordeum vulgare L.), and oat (Avena sativa L.) pure stands as well as two common vetch–cereal mixtures for silage with each of the above four cereals in two seeding ratios (i.e., vetch:cereal 55:45 and 65:35, based on seed numbers) to determine the competition among the different species and the economics of each intercropping system. Intercropping systems were assessed on the basis of several existing intercropping indices such as land equivalent ratio (LER), relative crowding coefficient (RCC or K), aggressivity (A), competitive ratio (CR), actual yield loss (AYL), monetary advantage index (MAI), and intercropping advantage (IA). The LER and K values were greater for the common vetch–wheat (55:45) and the common vetch–oat (65:35) mixtures indicating that in these systems, there was an advantage of intercropping for exploiting the resources of the environment. A similar trend to that of LER and K was also observed for AYL. The aggressivity, CR and partial AYL values were greater for barley and oat than for wheat and triticale, whereas the corresponding values for common vetch were lower in mixtures with barley and oat than in mixtures with wheat and triticale. These findings indicate that barley and oat were more competitive partners than wheat and triticale as common vetch was affected more in mixtures with these two crops. The highest MAI and IA values were recorded for the common vetch–wheat (55:45) and the common vetch–oat (65:35) mixtures indicating that these intercropping systems were the most profitable.     

Nitrogen effect on competition between winter cereals and littleseed canarygrass

Field experiments were conducted in northern Greece during 1994, 1995, and 1996 to study the effect of nitrogen fertilization on competition between littleseed canaryglass (Phalaris minor Retz.) and wheat (Triticum aestivum L.), barley (Hordeum vulgare =distichum L.) or triticale (Triticosecale). The presence of 400P. minor plants per square meter until early March did not have an adverse effect on dry weight of any crop. However, their further presence significantly reduced dry weight of wheat and triticale, but not that of barley. Grain yield of wheat and triticale was reduced 48% and 47%, respectively, by season-long competition ofP. minor, whereas the corresponding reduction for barley was only 8%. Crop yield reduction due toP. minor competition resulted mainly from reduction in ear number and less from reduction in 1000-grain weight. Nitrogen fertilization (150 kg N ha⁻¹), compared with control (0 kg N), slightly increased yield of all crops grown without weed competition. The same treatment also increased dry weight and competitive ability ofP. minor against wheat and triticale, compared with that of control (0 kg N); the split application of nitrogen (50 kg N ha⁻¹ before crop sowing and 100 kg N ha⁻¹ in early March) caused a slightly greater increase inP. minor dry weight than did 150 kg N ha⁻¹ applied once before crop sowing. Dry weight ofP. minor grown with barley was not affected by nitrogen fertilization, but it was severely reduced compared with that ofP. minor grown with wheat or triticale. http://www.phytoparasitica.org posting April 22, 2003.     

Wild Mustard (Sinapis arvensis L.) Competition with Three Winter Cereals as Affected by Nitrogen Supply

Two field experiments were carried out in northern Greece during the 1993–94 and 1994–95 growing seasons to investigate the effect of nitrogen (N) supply on interspecific competition between wild mustard (Sinapis arvensis L.) and wheat (Triticum aestivum L.), barley (Hordeum vulgare =distichum L.) and triticale (Triticosecale). The presence of 140 S. arvensis plants m⁻² until early March (averaged over N levels) did not have any adverse effect on the dry weight of all crops. However, its further presence significantly reduced the dry weight of wheat and triticale, but not that of barley. N fertilization (150 kg N ha⁻¹ regardless of application time) slightly increased the dry weight of wheat and triticale grown without weed competition compared with that of control (0 kg N). On the contrary, the presence of wild mustard, until harvest, reduced dry weight of wheat and triticale by 31 and 26 %, respectively, while the corresponding reduction for barley was only 1.5 %. Furthermore, N fertilization (150 kg N ha⁻¹) increased dry weight of wild mustard grown with wheat and triticale by 10 and 16 %, respectively, compared with that of control (0 kg N). Grain yield of wheat and triticale was reduced to 26 and 27 % by the competition of wild mustard, respectively, while the corresponding reduction for barley was only 3.5 %. Moreover, the wild mustard presence reduced total N content of wheat and triticale by 20 and 19 %, respectively, but this was not the case for barley.     

Interference between Avena sterilis, Phalaris minor and five barley cultivars

Field experiments were carried out in Northern Greece from 1994 to 1997 to study interference between Avena sterilis L. or Phalaris minor Retz. and five autumn-sown barley cultivars. Weed:crop interference began in early April. Avena sterilis at 120 plants m⁻² showed greater interference against barley than P. minor at 400 plants m⁻². The greatest grain yield and ear number reduction due to interference by either weed was recorded for cvs Klipper and Plaisant, and the least for cv. Athinaida; with cvs Carina and Thermi intermediate. Yield reduction due to A. sterilis for cvs Athinaida, Carina, Thermi, Klipper and Plaisant was 8, 16, 27, 61 and 67%, respectively, while corresponding losses to P. minor were 1, 8, 14, 45 and 55%. These results clearly indicate that growth and consequently yield components of cv. Athinaida were unaffected by the presence of either weed species, while those of cv. Carina were affected by A. sterilis , but not by P. minor . However, dry weight and panicle number of both weed species were severely reduced by interference with cvs Carina, Athinaida and Thermi compared with cvs Klipper and Plaisant. The order of interference of the five barley cultivars tested against A. sterilis and P. minor was Athinaida > Carina > Thermi > Klipper ≥ Plaisant.     

Effects of aromatic plants incorporated as green manure on weed and maize development

A 2-year field experiment was conducted in northern Greece to study the mulch effects of seven annual [anise (Pimpinella anisum L.), sweet fennel (Foeniculum vulgare P. Mill.), sweet basil (Ocimum basilicum L.), dill (Anethum graveolens L.), coriander (Coriandrum sativum L.), parsley (Petroselinum crispum (P. Mill.) Nyman ex A.W. Hill) and lacy phacelia (Phacelia tanacetifolia Benth.)] and three perennial [mint (Mentha X verticillata L.), oregano (Origanum vulgare L.) and common balm (Melissa officinalis L.)] aromatic plants, used as incorporated green manure, on the emergence and growth of barnyardgrass [Echinochloa crus-galli (L.) P. Beauv.], common purslane (Portulaca oleracea L.), puncturevine (Tribulus terrestris L.), common lambsquarters (Chenopodium album L.) and maize (Zea mays L.). In addition, the phytotoxic potential of the abovementioned aromatic plants extracts was determined in the laboratory using a perlite-based bioassay with maize and barnyardgrass. The bioassays indicated that germination, root elongation and fresh weight of barnyardgrass were reduced by the most aromatic plant extracts. However, maize growth parameters were only affected by the extracts of anise, sweet fennel, coriander, common balm and oregano. In the field, emergence of barnyardgrass, common purslane, puncturevine or common lambsquarters was reduced by 11–50%, 12–59%, 26–79% or 58–83% in green manure-treatment plots, respectively, as compared with green manure-free plots (control). On the contrary, maize emergence was not affected by any green manure. At harvest, maize grain yield in green manure-herbicide untreated plots was 10–43% greater than that in the corresponding green manure-free plots. In particular, maize grain yield in anise, dill, oregano or lacy phacelia green manure-herbicide untreated plots was 27–43% greater than that in the green manure-free-herbicide untreated and slightly lower than that obtained in the corresponding herbicide treated plots. These results indicated that green manure of aromatic plants, such as anise, dill, oregano or lacy phacelia could be used for the suppression of barnyardgrass and some broadleaf weeds in maize and consequently to minimize herbicide usage.     

Competitive interactions of fifty barley cultivars with Avena sterilis and Asperugo procumbens

A 2-year study was conducted in northern Greece to assess the ability of 29 six-row and 21 two-row barley (Hordeum vulgare L.) cultivars to compete with winter wild oat [Avena sterilis spp. ludoviciana (Durieu) Gill & Magne] and German-madwort (Asperugo procumbens L.). The fresh weight of both weeds grown in competition with six of the most competitive six-row barley cultivars (Bulk Resist. Desc-Sutter, Lignee 640, Paico's, Mantnan's-EH 165, Pistacho and Malebo) was reduced by 61–75% compared with one of the least competitive six-row cultivars [Gloria's-Copal's (30B-4Y-20M)]. The corresponding fresh weight reduction of both weeds grown in competition with three of the most competitive two-row barley cultivars (Goldmarker, Shanon and Helena) ranged from 59 to 76% compared with one of the least competitive two-row cultivars (Guanajuato). The ability to withstand competition (AWC) from winter wild oat and German-madwort of the six-row and two-row cultivars ranged from 33.7 to 78.3% and 26.7 to 69.2%, respectively. Representative yield losses ranged from 24 to 68% and 30 to 75%, respectively. The corresponding ability to compete (AC) indices ranged from 22.5 to 64.8% and 21.1 to 59.1%. The results of this study indicated that the barley cultivars Ligne 640 and Pistacho (2B-1Y-1B) had high AWC from winter wild oat and German-madwort and provided high grain yield in both weedy and weed-free conditions. Consequently, they could successfully be used in Mediterranean organic (no herbicide use) and conventional agricultural systems with reduced herbicide use. Barley cultivars with high AC and ability to produce high grain yield under weedy conditions [with Bulk Resist. Desc-Sutter, Arupo's and Gloria's-Copal's (30B-4Y-23M) among the most efficient] could also successfully be used in organic fields infected by the two weeds.     

Activity, adsorption and mobility of three acetanilide and two new amide herbicides

Activity, adsorption, and mobility of emulsifiable concentrate (EC) and microencapsulated (ME) formulations of alachlor and acetochlor as well as of metolachlor, S-metolachlor, dimethenamid and flufenacet were studied. Petri-dish bioassay, based on root response of oats ( Avena sativa L.), was used for their activity in sand and in a silty clay loam soil, and for determination of herbicide concentrations in soil solution (not adsorbed) and in column leachates of the adsorption and mobility studies respectively. Flufenacet and both acetochlor formulations showed the highest activity in both soils and ME-alachlor and metolachlor the lowest; the activity of dimethenamid, EC-alachlor and S-metolachlor was intermediate. Activity of both formulations of alachlor and acetochlor decreased with increasing organic matter content, but alachlor activity was reduced more than that of acetochlor. Lower amounts of dimethenamid and S-metolachlor were adsorbed by soil compared with the other herbicides and, consequently, greater amounts of these two herbicides were leached through that soil. None of the herbicides tested was detected below 30 cm. Less alachlor and acetochlor were biologically available in soil solution after their application as ME-formulations and, therefore, lower amounts of both ME-alachlor and ME-acetochlor were leached through the soil compared with those applied as EC-formulations.     

Activity,adsorption, mobility and field persistence of sulfosulfuron in soil

Petri dish bioassays, based on root response of corn grown in soil or in perlite, were used to study the activity, adsorption, mobility and field persistence of sulfosulfuron in a silty clay loam and a sandy loam soil. Both bioassays indicated that activity of sulfosulfuron increased with increasing herbicide concentration, and to a slightly greater degree in sandy loam soil than in silty clay loam soil. More sulfosulfuron was adsorbed on the sandy loam (not biologically available) than on the silty clay loam soil. Consequently, slightly greater amounts of sulfosulfuron were leached through the silty clay loam than through the sandy loam soil. Biologically available sulfosulfuron was not detected at depths below 40 cm after application in sandy loam, but this was not the case for the silty clay loam soil. In 2002, all sulfosulfuron rates showed field persistence of less than 5 months. On the other hand, in 2003, biologically available sulfosulfuron was detected in the 0–10-cm soil depth 150 days after application. http://www.phytoparasitica.org posting May 6, 2004.     

Sweet sorghum productivity for biofuels under increased soil salinity and reduced irrigation

Sweet sorghum (Sorghum bicolor (L.) Moench.) is a drought-tolerant crop with high resistance to saline-alkaline soils, and sweet sorghum may serve as an alternative summer crop for biofuel production in areas where irrigation water is limited. A two-year study was conducted in Northern Greece to assess the productivity (biomass, juice, total sugar and theoretical ethanol yields) of four sweet sorghum cultivars (Sugar graze, M-81E, Urja and Topper-76-6), one grain sorghum cultivar (KN-300) and one grass sorghum cultivar (Susu) grown in intermediate (3.2 dS m⁻¹) or in high (6.9 dS m⁻¹) soil salinity with either low (120 mm) or intermediate (210 mm) irrigation water supply (supplemented with 142–261 mm of rainfall during growth). The soil salinity and irrigation water supply effects on the sorghum chlorophyll content index, photosystem II quantum yield, stomatal conductance and leaf K/Na ratio were also determined. The sorghum emergence averaged 75,083 plants ha⁻¹ and 59,917 plants ha⁻¹ in a soil salinity of 3.2 dS m⁻¹ and 6.9 dS m⁻¹, respectively. The most affected cultivar, as averaged across the two soil salinity levels, was the Susu grass sorghum emerging at 53,250 plants ha⁻¹, followed by the Topper-76-6 sweet sorghum emerging at 61,250 plants ha⁻¹. The leaf K/Na ratio decreased with decreasing irrigation water supply, in most cases, but it was not significantly affected by soil salinity. The dry biomass, juice and total sugar yields of sorghum that received 210 mm of irrigation water was 49–88% greater than the yields of sorghum that received the 120 mm of irrigation water. Sorghum plants grown in a soil salinity of 3.2 dS m⁻¹ produced 42–58% greater dry biomass, juice and total sugar yields than the yields of sorghum plants grown in a soil salinity of 6.9 dS m⁻¹. The greatest theoretical ethanol yield was produced by sweet sorghum plants grown in a soil salinity of 3.2 dS m⁻¹ with 210 mm of irrigation water (6130 L ha⁻¹, as averaged across cultivar), and the Urja and Sugar graze cultivars produced the most ethanol (7620 L ha⁻¹ and 6528 L ha⁻¹, respectively). Conclusively, sweet sorghum provided sufficient juice, total sugar and ethanol yields in fields with a soil salinity of 3.2 dS m⁻¹, even if the plants received 50–75% of the irrigation water typically applied to sorghum.     

Differential competitive and allelopathic ability of Cyperus rotundus on Solanum lycopersicum,Solanum melongena and Capsicum annuum

A 2-year greenhouse and laboratory study was conducted to investigate the competition and allelopathy between Cyperus rotundus L. and Solanum lycopersicum L., S. melongena L. and Capsicum annuum L. All crops showed low ability to withstand competition of C. rotundus and this was the reason for the reduction of their total fruit number and fruit yield by 81%–94% and 86%–96%, respectively. The aqueous extracts from C. rotundus plant parts decreased the seed germination and root length of all vegetable cultivars, indicating supplementary allelopathic activity of C. rotundus on all vegetables. The low correlation coefficient between the total fruit yield of the cultivars grown under weed-free conditions and total fruit-yield reduction due to C. rotundus interference indicates clearly that the yielding ability of the cultivars is not related with their tolerance to C. rotundus interference.