Effect of Summer Crops Producing Allelopathic Compounds, Plant Density and Varieties of Faba Bean on Incidence of Broomrape

Allelopathy is a natural which may prove to be a unique tool for weed control treatments and thereby increase some crop yields.Two experiments were conducted in naturally infested fields with broomrape (Orobanche crenata Forsk.) at Shandaweel Research Station, Sohag Governorate during 2013/14 and 2014/15 winter seasons.The aim of this work was to study the effect of crop sequences for producing allelopathic (cotton, sorghum and maize), two faba bean varieties (Giza-843 and Giza-40) and two plant densities (one side of the ridge and two sides of the ridge) in a split split-plot design were used to study the control of broomrape in faba bean.Results showed that sowing of maize before faba bean decreased significantly numbers and weight of broomrape spikes by 32.0 & 18.5% in the first season and by 37.7 & 37.5% in second season and lead to increase in number of days to broomrape emergence above soil surface by 18.5 & 16.6% in both seasons, respectively, compared to cotton and sorghum.Faba bean seed yield and components were increased by sowing faba bean after maize compared with faba bean after cotton and sorghum.While, faba bean after maize increased the seed yield of faba bean by 13.8 and 13.6 % in both seasons, respectively.Sowing of cotton before faba bean increased significantly the plant height, weight of pods/plant, weight of seeds/plant, 100-seed weight and seed yield (ardab/fed) by 3.9, 5.2, 4.9, 4.8 and 5.8% in 1 st season, respectively, and by 9.1, 2.0, 3.5, 4.7 and 5.5% in 2 nd season, receptively, compared with sowing of sorghum before faba bean.Number, weight and days emergence of broomrape above the soil surface were significantly affected with varieties of faba bean.Superiority of Giza 843 over Giza 40 was by 30.7 and 16.8% in the first season and by 39.7 and 37.5% in the second season.Late-onset broomrape above the surface of the soil with the cultivation of Giza 843 was by 16.8 and 22.5% in the first and second seasons, respectively.Varieties of (vicia faba) were significantly increased on yield ( plant height, weight of pods/plant, weight of seeds/plant, 100seed weight and seed yield/fed) in both seasons.Seed yield of faba bean was increased at cultivation of Giza 843 by 39.7 and 37.5% in the respective 1 st and 2 nd seasons, respectively, compared with Giza 40.Plant density showed significant effect on the number and weight of broomrape and days of number emergence of broomrape above the soil surface.Increasing plant density from 13 to 26 plants/m 2 increased the number and dry weight of broomrape/m 2 by (25.5 and 36.7%) and (29.3 and 28.6%) in both seasons, respectively.Faba plant height, weight of pods/plant, weight of seeds/plant, 100-seed weight and seed yield (ardab/fed) significantly affected was plant density in both seasons.The seed yield of faba bean cultivation was increased at the rate of 26 plants/m 2 by 5.58 and 4.91% in both seasons, respectively, compared to faba density of 13 plants/m 2 .The interaction between crop sequences for producing allelopathic, faba varieties, and plant density were significant for the number and weight of broomrape spikes and also delayed the onset of broomrape above the soil surface, as well as increased faba bean yield and yield components in both seasons.This may be obtained in less number and weight of broomrape and the maximum number of days for the appearance of broomrape, as well as the higher weight of 100-seed and seed yield (ardab/fed) from the cultivation of maize crop earlier with the use of Giza 843 faba variety in the two seasons.Triple interaction between crop sequences for producing allelopathic, faba varieties and plant density was not significant for the number and weight of broomrape of spikes and faba yield and its components in the both seasons.HPLC analysis revealed that there were seven phenolic acids isolated from the foliage dry weight of cotton, sorghum and maize: (protocatechuic, caffic, p-hydroxy benzoic, vanillic, syringic, coumaric, and ferulic acid).However, the amounts of these phenols differ from plant to another.The highest values in maize are ferulic acid (325.5 µg) and coumaric acid (142.3µg),vanillic (95.5µg), p-hydroxy benzoic (53.6 µg) and caffic (36.5 µg).While, in sorghum are ferulic acid (249.9µg) and coumaric acid (120.2µg), and in cotton are ferulic acid (236.5µg) and syringic acid (204.4µg) and protocatechuic (44.4µg).From this study, it can be used the cotton, sorghum and maize as an Allelopathy influence plants in the agricultural cycle system through the cultivation of summer and winter crops relay in anti broomrape field in addition to the selection of resistant varieties and plant high density to reduce injury.Moreover, it can used these natural chemical compounds either as water extract of the shoots of plants with Allelopathy influence directly or mixed with soil in order to reduce the rate used of herbicides recommended, and increase the effectiveness of herbicides in weed control.