Integrated Broomrape (Orobanche crenata Forsk.) Control in Faba Bean (Vicia faba L.) with Nitrogen Fertilizer, Intercropping and Herbicides

TWO FIELD experiments were carried out at the farm of Sakha Agricultural Research Station, Kafrelshiekh, Egypt, during 2010-2011 and 2011-2012 faba bean growing seasons (Latitude 30º 48ˋ N, Longitude 31º 35ˋE). The trials studied integrated broomrape (Orobanche crenata Forsk.) control in faba bean cv. Giza 843 with nitrogen fertilizer, intercropping faba bean (Vicia faba L.) with oat (Avena sativa L.) or fenugreek (Trigonella foenum-graecum L.) and herbicides. Herbicide treatments were: 1- Untreated, 2- Glyphosate (48% WSC) at 36 g a.i./fed., (fed = feddan= 0.42 hectare),(once)., 3- Glyphosate (48% WSC) at 36 g a.i./fed. (twice)., 4- Imazapic (10 % EC) at 20 g a.i./fed. (once), 5- Imazapic (10 % EC) at 20 g a.i./fed. (twice). Sub-plots were assigned to faba bean (sole crop), intercropping (faba+ oats), (faba+ fenugreek) and nitrogen fertilizer with ammonium nitrate (NH₄NO₃).
The two broomrape control herbicides substantially suppressed number and dry weight of broomrape spikes / m² compared with untreated in both seasons. Foliar spray of Imazapic and Glyphosate twice on faba bean recorded a less number and dry weight of broomrape spikes / m² than its spray one time. Spikes number and dry weight of broomrape parasite weed/m² were significantly decrease in faba bean intercropped with fenugreek and oat or fertilized with nitrogen compared with sole faba bean in both seasons. Intercropping faba bean with fenugreek (Trigonella foenum-graecum L.) recorded the lowest number and dry weight of broomrape spikes/m² followed by application of N fertilizer then oat in the two seasons. Foliar spray of Imazapic twice on faba bean intercropped with fenugreek recorded a less number and dry weight of broomrape spikes/m². There were no significant differences in spikes number and dry weight of broomrape weed/m² among application of fenugreek and oat or NH₄NO₃ with spraying Imazapic or Glyphosate twice in both seasons. The greatest reduction in number (>82%) and dry weight (> 90%) of broomrape spikes/m² were obtained by application of fenugreek along with Imazapic herbicides twice in both seasons.
Repeating foliar spray with either Imazapic or Glyphosate on faba bean plants resulted in a significant decrease in photosynthetic pigments (chlorophyll a, b and total chlorophyll) content in leaves compared with untreated treatment in both seasons. All photosynthetic pigments contents were significantly greater in leaves of faba bean fertilized by N fertilizer than in those of sole faba bean plants without N fertilizer or intercropped with fenugreek or oat in both seasons. Foliar spraying of the two herbicides once or twice on faba bean significantly increased plant height, number of branches and pods/plant, 100-seed weight, seed yield/plant, seed and biological yields/fed. of faba bean compared with untreated treatment in both seasons. Faba bean plants sprayed twice with of Imazapic herbicide significantly exceeded those sprayed once with Imazapic or Glyphosate herbicides in seed and biological yields as well as its attributes in both seasons. Faba been intercropped with fenugreek or fertilized with NH₄NO₃ produced significantly taller plants and greater seed and biological yields as well as its attributes than did sole faba bean without N fertilizer in both seasons. The combination of Imazapic herbicide twice and fenugreek recorded the highest seed yield, while sole faba bean plants without N fertilizer and untreated produced the lowest one in both seasons. It can be concluded that foliar spraying with Imazapic or Glyphosate twice on faba bean intercropped or fertilized with NH₄NO₃ could be recommended for optimum broomrape parasitic weed control and highest seed yield at Kafrelsheikh Governorate, Egypt.