Yield and Competitive Interaction between Black Seed (Nigella sativa L.) and Chickpea (Cicer arietinum L.) as Influenced by Inter and Intra-Specific Competition
Aryan S. A. Dizayee
Department of Field Crops and Medicinal Plants, College of Agricultural Engineering Sciences, Salahaddin University-Erbil, Kurdistan Region, Iraq
Corresponding E-mail: [email protected].
Available from. http://dx.doi.org/10.21931/RB/2023.08.03.122
The study aimed to investigate the yield and competitive interaction between black seed (Nigella sativa L.) and chickpea (Cicer arietinum L.) under varying inter and intra-specific competition conditions. The pot experiment conducted at Grdarasha Research Farm, College of Agricultural Engineering Sciences. The experiment involved two species (black seed and chickpea) one intra-specific competition treatment and four inter-specific competition treatments consist of different seed rate portions. The results postulate that higher mean value of number of capsule per plant possessed at inter-specific competition (5 black seed + 4 chickpea). Additionally, intra-specific competition postulated highest mean value of grain yield per plant for both black seed and chickpea respectively. Competitive interaction especially competitive balance index and relative yield (CBIc and RYc) was more superior than other parameters of competitive indices. These findings contribute to our understanding of the competitive dynamics between these two crops and provide insights for optimizing crop management practices in intra and inter-specific competitions.
Keywords: Black seed, Chickpea, Inter-specific competition, Intra-specific competition, Yield, Competitive Interaction
Mixed cropping systems have gained attention as sustainable agricultural practices that enhance resource utilization and improved agricultural productivity1 . Black seed refers to the seeds of the plant (Nigella sativa L.) it is an annual flowering plant belonging to the Ranunculaceae family2. Black seed has been used for centuries in traditional medicine and culinary practices3. Chickpea, scientifically known as (Cicer arietinum L.), is a legume crop belonging to the Fabaceae family, it is one of the earliest cultivated crops and is widely consumed. Chickpeas are known for their high protein content and nutritional value ,Both black seed and chickpea are important crops with cultural, culinary, and economic significance, they have distinct characteristics, nutritional properties, and utilization purposes, making them valuable resources in agriculture, food production, and traditional medicine5. However, limited research has been conducted to explore the yield and competitive interaction between these two crops. Competitive interactions refer to the interactions between individuals or species that compete for limited resources within an ecological community ,These interactions can occur both (within a species) intra-specific competition and between (different species) inter-specific competition6. Competitive interactions may affect the distribution, abundance, and behavior of any organisms and play a highly significant role in designing community dynamics7. Competitive interactions can vary and depends on many factors such as resource availability, population densities, and the competitive abilities of the species involved8.
MATERIALS AND METHODS
The pot experiment conducted at Grdarasha Research Farm, College of Agricultural Engineering Sciences / Salahaddin University – Erbil / Iraq on location 36.2˚ N 44.1˚ E and elevation 440 m above mean sea level, during winter growing season 2021 and 2022. Two species, black seed (Nigella sativa L.) and chickpea (Cicer arietinum L.), were included in the study followed a completely randomized design replicated thrice. The intra-specific competition treatment involved a fixed seed rate for each species, while the inter-specific competition treatments consisted of four different seed rates to induce varying levels of competition between the two species.
Pot Preparation, Planting and Crop Management:
Uniform-sized pots were used, and each pot was labeled accordingly. Seeds of black seed and chickpea var. Rafiddain, were sown in separate pots according to the specified treatments. For the intra-specific competition treatment, a fixed seed rate was used for each species (9 seed for black seed and 9 seed for chickpea). In addition, inter-specific competition treatments, different seed rates were applied to create varying levels of competition between the two species (6 seed black seed + 3 seed chickpea, 3 seed black seed + 6 seed chickpea, 5 seed black seed + 4 seed chickpea, 4 seed black seed + 5 seed chickpea). Mechanical and chemical analysis of soil is presented in Table (1).
Table. 1 Mechanical and chemical properties of the experimental soil during 2021-2022 winter growing season.
Adequate watering was provided to maintain optimal soil moisture levels throughout the experiment. Regular monitoring and removal of weeds were conducted to minimize interference and ensure the focus was on the target species.
Data on various yield parameters were measured include (number of capsule, pod per plant and grain yield per plant). As for competitive indices which provide insights into the competitive ability and dynamics between the two species (black seed and chickpea) under varying levels of competition, such indices were measured include:
Aggressivity quantifies the competitive ability of one crop in suppressing the growth or yield of another crop9.
Aab = Yab / Yaa × Zab – Yba / Ybb × Zba
Competitive Balance Index (CBI)
It is calculated by comparing the actual species composition in a mixed stand with the expected species composition under conditions of perfect competition12
CBI = log (( Yab / Yba ) / ( Yaa / Ybb))
Competitive Ratio (CR)
CR measures the competitive ability of one crop over another in an intercropping system 13.
CRa = (( Yab /Yaa ) / ( Yba / Ybb ))
Relative Yield (RY)
It is calculated by dividing the yield of the focal species in mixed stands by its yield in monoculture 14.
RYa = Yab / Yaa
RYb = Yba / Ybb
Relative Yield Total (RYT)
RYT is a widely used competition index that measures the relative performance of intercropped crops compared to their yields in monoculture. It is calculated as the sum of the relative yields of each crop in the intercrop10
RYT = Yab / Yaa + Yba /Ybb
Yaa = Yield in pure stand of species (a).
Ybb = Yield in pure stand of species (b).
Yab = Mixture yield of species (a) in combination with species (b).
Yba = Mixture yield of species (b) in combination with species (a).
Zab = Sown proportion of species (a) in mixture with species (b).
Zba = Sown proportion of species (b) in mixture with species (a).
The collected data were analyzed using appropriate statistical software15 , program. Analysis of variance (ANOVA) was performed to determine significant differences among treatments16. post hoc test at a P value of %5, were conducted to compare means and identify treatment effects.
Yield and Yield Component of Black Seed and Chickpea as Influenced by Intra and Inter-Specific Competition
Number of Capsules, Pods per Plant
Number of capsules, pod per plant is an important yield component that contributes to the overall productivity of crops. Figure (1) presents the mean number of capsules, pods per plant for black seed and chickpea under different competition scenarios. The results indicate that the number of capsules, pods per plant varied significantly (P ≤ 0.05) among the different treatments.
Figure 1. Effect of intra and inter-specific competition on the number of capsules, and pods per plant of black seed and chickpea
Grain Yield per Plant-1
Grain yield per plant-1 is a crucial parameter that directly represent the amount of harvested grains or seeds produced by an individual plant and is an essential indicator of crop performance and yield potential. The results indicate that the mean grain yield per plant showed highly significant effects (P ≤ 0.05) among the different treatments figure (2).
Figure 2. Effect intra and inter-specific competition on grain yield per plant-1 of black seed and chickpea.
Competitive Interaction of Black seed and Chickpea as Influenced by Intra and Inter-Specific Competition
Is a measure used to postulate the competitive ability of one species compared to another species in mixtures. A species with higher aggressivity has a greater negative influence on other species, causing to reduced plant growth and productivity. Aggressivity (A) was calculated for black seed (Ab) and chickpea (Ac) by using a model applied by Mc Gilchriest, 1965 figure (3). As shown in equation (3.1 and 3.2) respectively.
Ab = -0.023x – 0.200 …..….. 3.1 R2 = 0.0992
Ac = 0.013x + 0.225 …..….. 3.2 R2 = 0.0317
Figure 3. Aggressivity (A) in black seed (Ab) and chickpea (Ac) in for different seed portions of inter-specific competition.
Competitive Balance Index (CBI)
The Competitive Balance Index is a parameter used to evaluate the relative competitive abilities of different species in a mixed community. CBI values range from (0 to 1), where values closer to (1) indicate a more balanced competition among species. Figure (4) disclosed competitive balance index (CBI) of black seed (ABIb) and chickpea (CBIc) were modified according to equation (3.3 and 3.4) respectively.
CBIb = -0.025x - 0.115 …..….. 3.3 R² = 0.0834
CBIc = 0.0541x + 0.043 …..….. 3.4 R² = 0.3966
Figure 4. Competitive Balance Index (CBI) in black seed (CBIb) and chickpea (CBIc) in for different seed portions of inter-specific competition.
Competitive Ratio (CR)
CR is a parameter that compares the yield of one species to that of a competing species. Figure (5) revealed a competitive ratio of black seed (CRb) and chickpea (CRb) were behaved according to equation (3.5 and 3.6) respectively.
CRb = -0.026x + 0.765 …..….. 3.5 R² = 0.0353
CRc = 0.086x + 1.39 …..….. 3.6 R² = 0.0771
Figure 5. Competitive Ratio (CR) in black seed (CRb) and chickpea (CRc) in for different seed portions of inter-specific competition.