The competition effects of fenugreek and black cumin plants on yield and yield components under drought stress

Drought stress is one of the most important factors limiting crop production in arid and semi-arid area. Most of the agricultural land of Iran was located in arid and semi-arid area and severe water deficit threaten the agriculture of these areas. Accordingly, any strategy to reduce the effects of drought on crop yields is necessary. In agroecosystems, interspecific plant competition for water commonly is less than the intraspecific competition, because various species have different structure, root system and peak water requirements. So, the competition effects of fenugreek (Trigonella foenum graceum ) and black cumin (Nigella sativa L.) on yield and yield components were investigated with the aim of reducing damage of drought stress. In this experiment, five planting patterns including sole fenugreek, sole black cumin and intercrop ratios (2:1, 1:1, 1:2 of fenugreek and black cumin) under W1: normal conditions (maintenance of soil water between 70-100% field capacity), W2: moderate drought stress (irrigation based on 75% W1), and W3: severe drought stress (irrigation based on 50% W1) were evaluated. Consumed water volume for each plot was regulated by the counter for irrigation time determination. In fenugreek, traits such as plant height, number of branches per plant, number of pods per plant, number of seeds per pod, 1000 seed weight and grain yield were measured. For black cumin, the plant height, number of branches per plant, number of capsules per plant, number of seeds per capsule, 1000 seed weight and seed yield were measured. In moderate drought stress, the highest seed yield was observed in fenugreek: black cumin (2:1) and (1:2) on average with 1320 and 1222 kg ha-1, respectively. But, in severe drought stress, the greatest seed yield (on an average of 842) was achieved in fenugreek: black cumin (1: 2) and the lowest (on an average of 548 ) was observed in fenugreek sole cropping as well. The highest land equivalent ratio (LER) was belonged to fenugreek: black cumin (2:1) at normal conditions with average of 1.25. In moderate drought, the LER of intercropping treatments was more than one for all patterns. In severe drought stress, fenugreek: black cumin (2:1) and (1:1) had a high LER with average of 1.5 and 1.24, respectively. In general, it could be concluded that although the highest seed yield was achieved in normal irrigation, however in mild and severe drought stress, seed yields of fenugreek: black cumin (1:2 and 2:1) were significantly more than sole cropping. Therefore, could be applied for these medicinal plant production in areas with water scarcity and prevent the agricultural unsustainability via intercropping strategy