عنوان مقاله [English]
Intercropping, the agricultural practice of cultivating two or more crops in the same space at the same time, is an old and commonly used cropping practice which aims to match efficiently crop demands to the available growth resources (Agegnehu et al., 2006; Dhima et al., 2007). Intercropping of chickpea with linseed reduced the chickpea yield by 60.3%, although linseed occupied only 33% of the total area. The loss of chickpea yield was compensated by the additional yield of linseed, and thus the system productivity of chickpea + linseed intercropping was increased by 43.4% compared with sole chickpea (Ahlawat & Gangaiah, 2010).
The objectives of the present study were to study the competition indices of barley and pea intercropping and effects of nitrogen and different intercropping arrangements on forage yield.
Materials and methods
In order to evaluate effects of nitrogen and different intercropping arrangements of barley and pea on yield and competitive indices, an experiment was conducted as factorial based on Randomized Complete Block Design with three replications on farm research on Gonbad Kavous University (37°26’N, 55°21’E, and 45m above sea level) in 2011-2012. Different intercropping arrangement levels were a sole crop of barley, intercropping of one line barley and one line pea, intercropping of two lines of barley and two lines of pea, intercropping of three lines of barley and three lines of pea and sole crop of pea and nitrogen consumption was in four levels of none application of nitrogen and application of 25, 50 and 75 kg.ha-1.
Seed planting was done during the first week of December 2011. Sowing was performed manually by planting twice more seeds of pea than the expected plant density. Sole barley (cv. Sahra) planted at the rate of 160 kg.ha-1 and sole pea (cv. Sungro) planted at the rate of 500000 plants.ha-1. Row spacing was 20 cm. The experimental plots for a sole crop of barley, a sole crop of pea and one row of barley + one row of pea were 4 rows and for two rows of barley + two rows of pea and three rows of barley + three rows of pea were 6 and 8 rows, respectively.
50% of urea was applied during sowing. The other 50% of urea was side banded when the barley plants were at flowering stage. Weed control was performed manually. Forage yield was determined by harvesting each crop from 2, 4 and 6 rows. Barley was harvested at soft drought and the pea was harvested at seed filling stage in 3 May 2012. Data were analyzed using SAS software. Analysis of variance was performed for the forage yield and Equal Yield of barley.
Results and discussion
The results showed the effects of different intercropping arrangements, nitrogen application and interaction of different intercropping arrangements × nitrogen application on forage yield and Equivalent Yield of barley was significant (α= 1%). The high forage yield and Equivalent Yield of barley belonged to a sole crop of barley with application of 75 and 50 kg Nha-1 with 14.51 and 14.3 tonha-1, respectively. The minimum dry weight and Equivalent Yield of barley was obtained from the sole crop of pea without consumption of nitrogen with 3.76 and 4.7 tha-1, respectively. Increasing the pea and barley rows in intercropping treatments decreased forage yield because of lower yield of pea. Land Equivalent Ratio in intercropping treatments was less than 1. This index in barley was greater than pea (0.643, 0.588 and 0.543 for barley and 0.198, 0.247 and 0.362 for pea in 1, 2 and 3 rows, respectively). Other indices (Relative Crowding Coefficient, Aggressivity, Competitive Ratio, Actual Yield addition, Intercropping Advantage and Equivalent Yield of barley) in barley were also greater than pea in intercropping. Barley was the dominant crop in this study.
Forage dry weight and Equivalent Yield of barley in a sole crop of barley with consumption of 75 and 50 kgN.ha-1 was the maximum and in sole crop of pea with non-consumption of N was minimum. All indices in barley in this study were greater than pea. This indicated that barley was the dominant crop.