FORAGE YEILD AND COMPITITION INDICES OF CEREALS MIXED INTERCROPPING WITH FORAGE LEGUMES IN SULAIMANI REGION

The present study was conducted in Sulaimani region at two different locations, Kanipanka and Qlyasan during winter season of 2019-2020 to estimate the response of forage yield and some competition indices to the effect of crop pure stands and their mixtures of barley and triticale intercropped with narbon vetch and grass pea with some different patterns. The experiment was designed according to Completely Randomized Block Design with three replications. As the average of both location the maximum green forage yield was produced by pure narbon vetch 32.610 ton ha-1, while pure barley produce maximum dry forage yield and dry matter % reached 5.506 ton ha-1 and 8.55% at booting stage respectively, but the crop mixture barley/grass pea at a rate 2:1 produce maximum green and dry forage yield 32.083 and 5.616 ton ha-1 respectively at booting stage. The crop mixture barley/vetch 1:1 gave maximum dry matter% 17.88% at the same stage. The highest value for total LER was 1.401recorded by the mixture of triticale/grass pea at elongation stage, while the highest relative crowding coefficient was 1.285 recorded by the same mixture at a rate 1:1 at the same cutting stage. Maximum competitive ratio for cereals was 3.652 recorded by barley in the mixture barley/grass pea 1:2 at elongation stage, while for legume it was 2.292 for narbon vetch in the mixture triticale/vetch 2:1 at booting stage.


INTRODUCTION
The global human population is projected to reach beyond 9.8 billion by the end of the year 2050 (32). Thus, productivity must be increased through sustainable production by taking into account climate change, rarefaction of resources like phosphorus and water, and losses of fertile lands. Crop production should be increased further without deteriorating the soil fertility, environment, and food quality (6,22). Increasing world population and the urgent need of food products are of the basic problems of today's world. Yet most challenging problem in today's world is food security of human as a first need (4). In recent years, there has been increased interest in agricultural production systems in order to achieve high productivity and promote sustainability over time. Several factors can affect growth of the species used in intercropping, including cultivar selection, seeding ratios, and competition between mixture components (8). Such as crop rotation, relay cropping and intercropping of annual cereals with legumes. Intercropping of cereals with legumes has been a common cropping system in rain-fed areas, especially in the Mediterranean countries; (17). Legumes and cereals do not provide satisfactory yields when they are pure seeded. There are some rational reasons of this situation. First of all, legume crops are low-yielding, especially in areas where rainfall is insufficient, and the plant lodging causes some problems during harvest. On the other hand, cereals produce high forage yields but with low protein content which is far from the requirements of many livestock (26). Barley and wheat respectively, are the most suitable cereals for mixtures (27). Different seeding ratios or planting patterns for cereal-legume intercropping have been practiced by many researchers (4,11,37). The greater benefit for forage quality was found when common vetch was grown in a monoculture or in mixture with cereals reported by (17). The objectives of the present study were to evaluate cereals and legumes intercrops compared to mono-crops with regard to the forage production, to estimate the effect of competition within cereals -legumes intercropping systems, and to examine different competition indices in these intercropping systems.

MATERIALS AND METHODS Site and The Experimental Set Up
Two locations were selected for applying this research in the governorate of Sulaimani which is located in the northeast of Iraq, on the border with Iran., the first was Kanipanka agricultural research station, located at ( Latitude: 35 0

Climatic conditions of Sulaimani region
The climate of Sulaimani governorate is considered as a semi-arid environment: cold and wet in winter, hot and dry in summer. The average temperature from July to august is between 39-43 0 C and often reaching nearly 50 0 C. October means high temperatures 24 -29 0 C and slightly cooling down in November. The rainfall is limited to winter and spring months (19).

Plant material and treatments
The seed-bed was well prepared through two perpendicular plowing and removing residual of the previous crop and weeds. Prior to planting, seeds were treated with benomyl at 0.2% [wt/wt] in order to protect them from soil-borne pathogens. Barley and triticale as sole, two legume monocrops, narbon vetch and grass pea as well as mixtures of each of barley and triticale with each of the above two legumes in three seeding ratios (i.e. 1:1, 1:2 and 2:1) based on seed rate.200 kg ha -1 for both triticale and Barley and 160 kg ha -1 for narbon vetch and grass pea as monoculture, while for retni -giipprec 1:1 it was 100:80 kg ha-1and for retni -giipprec 1C:2 L it was 66.7:106.7 kg ha-1, but for retni -giipprec 2C:1L it was 133.3:53.3 kg ha-1. The seeds were sown in the 12th November in Qlyasan location and 15th November in Kanipanka location 2019. Seeds in mixture treatments were mixed and sown together. The experimental design comprised a randomized complete block (RCBD) with sixteen treatments. The experimental plots were 3 X 1.5 m (6 rows, 0.25m apart), sixteen treatments were applied: pure triticale (PT), pure barley (PB), pure narbon vetch vetch (PN), pure grasspea (PG), triticale + narbon vetch (TN), triticale + grasspea (TG) barley + narbon vetch (BN) and barley grasspea (BG), 1 triticale +2narbon vetch (1T2N), 1triticale +2grasspea (1T2G),1 barley+2 narbon vetch (1B2N) and 1barley + 2grasspea (1B2G), 2 triticale +1narbon vetch (2T1N), 2triticale + 1grasspea (2T1G), 2barley+1narbon vetch (2B1N) and 2barley +1grasspea (2B1G), Pure stands and mixtures were harvested at two growth harvested at two growth stages of cereals (stem elongation and booting) according to (38). At each stage, four rows of each plot were cut to ground level with manual shears, and the forage in mixture treatments was separated by hand for the determination of the cereals' and legumes' percentage in each mixture. The samples were dried in the oven at 70˚C to a constant weight to determine the dry matter yield. The growth rate of the species between the two cutting dates was calculated. The following competition indices: Land equivalent ratio LER indicates the efficiency of retni -giipprec , using the environmental resources compared to monocropping (21). When LER >1 the retni -giipprec favors the growth and yield of the species. In contrast, when LER < 1 there is no retni -giipprec advantage and the retni cpngrerg competition is stronger than the retni cpngrerg interaction within retni -giipprec system (39). LER was calculated as: LER = (LER cereal + LER legume ); LER cereal = Yci /Yc ; LER legume = Yli/ Yl , Where Yc is the yield of cereal as sole crops, Yl is the yield of legume as sole crops, Yci is the yield of cereal as retni -giipc and Yli is the yield of legume as retni -giipc . Aggressivity Aggressivity (A) is a competitive index, which is a measure of how much the relative yield of one crop component is greater than that of another (20). Aggressivity is expressed as: A cereal = Yci/ Yc × Pci -Yli/ Yl × Pli A legume = Yli/ Yl × Pli − Yci Yc × Pci , Where Pci is the sown proportion of cereal in mixture with legume and Pli is the sown proportion of legume in mixture. If A cereal or A legume = 0, both crops are equally competitive. When A cereal is positive then the cereal species is dominant and when it is negative then legume is the dominating species.

Relative crowding coefficient
The relative crowding coefficient (RCC or K) in plant competition theory introduced by (10). The K allowed evaluating and comparing the competitive ability of one species to the other in a mixture (39). The K was calculated as: K = K cereal × K legume ; K cereal = Yci × Pli/ (Yc − Yci) × Pci ; K legume = Yli × Pci/ (Yl − Yli) × Pci , If K cereal is greater than K legume , cereal is more competitive than legume. Also, when the product of the two coefficients (K cereal and K legume ) is greater than 1 there is a yield advantage, when K is equal to 1 there is no yield advantage, and when it is less than 1 there is a disadvantage.

Competitive ratio
The CR, introduced by (36), was used as an indicator to evaluate the competitive ability of different species in inter-cropping, using the following formula (35,31). CR cereal = LER c / LER l × Pl i / Pc i ; CR legume = LER l / LER c × Pc i / Pl i , If CR cereal > 1, cereal is more competitive than legume, and if CR cereal < 1, then cereal is less competitive than legume (39).

Actual yield loss
The AYL is the proportionate yield loss or gain of inter-crops in comparison to the respective sole crop. In addition, partial AYL cereal and AYL legume represent the proportionate yield loss or gain of each species in intercropping compared to their yield in sole crops. The positive or negative values of AYL indicate the advantage or disadvantage of the inter-cropping (11) The AYL is calculated using the following formula  Table 1 show the effect of crop pure stand and their mixtures on green, dry yield ton ha -1 and dry matter% at both locations and their average at elongation stage. There were highly significant differences among treatments for all traits. maximum green and dry yield value for pure stands recorded by narbon vetch reached 37.067 and 4.136 ton ha -1 respectively at the first location, but the highest percentage of dry matter was 17.31 % obtained from barley at the second location. Data represent in Table 2 illustrate the effect of crop pure stand and their mixtures in green, dry yield and dry matter% at booting stage. The differences among treatments were highly significant. The highest value for green and dry yield for pure stands recorded by narbon vetch reached 45.473 and 6.528 ton ha -1 respectively at the first location. But the maximum dry matter % for pure stands reached 20.47 % recorded by barley at the second location. Regarding to the mixtures the highest green was 38.613 ton ha -1 obtained from barley/vetch 2:1 at the first location, but the highest dry yield reached 6.400 ton ha -1 from the mixture barley/grass pea 2:1 at the first location also. The highest dry matter % for crop mixtures recorded by barley/ vetch1:1 reached 20.89 % at the second location. Data in Table 3 explain the land equivalent ratio at stem elongation stage in mixtures at both locations. The effect of mixtures in this trait was highly significant. The highest value for total LER was 1.669 recorded by the mixture barley/grass pea 2:1 at the second location, while the lowest total LER was 0.734 for the mixture barley/vetch 1:2 at the second location. The maximum cereal LER was 0.991 exhibited by barley in the mixture barley/ vetch 2:1, and the lowest cereal LER was 0.335 for triticale in the mixture triticale/vetch 1:2 at the second location. The highest legume LER was 0.735recorded by grass pea in the mixture barley/ grass pea 2:1 at the second location, but the lowest legume LER value was 0.141 for grass pea in the mixture barley/ grass pea 2:1 at the first location.         table 13 illustrate the effect of location on fresh, dry yield and dry matter % at both elongation and booting stage. The differences between locations were highly significant for all traits at both stages with the exception of dry matter% at elongation stage, which was not significant. During elongation stage the Kanipanka location predominated the Qlyasan location high significantly in both fresh and dry yield by 68.0 % and 67.7 % respectively. At booting stage also Kanipanka exceeded Qlyasan location in both traits fresh and dry yield high significantly by 40.0 % and 28.4% respectively, this confirm the suitability of the first location more than the other for these traits, this may be due to agreement of the environment condition prevailing in the first locating in term of temperature, lighting and other factors at both stages of growth. At the second stage it was indicated the out yielding the second location in dry matter over the first location by 16.38%.  Results in that applied inter cropping system affected green, dry yield and dry matter % significantly. It was confirmed that barley and triticale are crops which can be used as mono crops or in mixture system with legumes if the harvest date was adjusted for the forage to match the quantity and quality of the resulting mixture. There are a few numbers of mixtures that are superior to monoculture in both green and dry forage yields. The superiority of barley over triticale in forage yield (green and dry) during both cutting dates and both locations in monoculture and mixtures can be interpreted by the vigor growth of barley in the early stage of its life cycle compare to triticale. Many studies have reported a yield increase of forage cereal/legume inter crops compare to cereal sole crops (7,8,20). The mixtures barley/grass pea and triticale/vetch 2:1 showed its superiority over the other mixtures at both locations and both cutting. The greater yield was found in the cereal/legume mixtures, which had the highest proportion of legume (25). Barley/legume inter crops produced the highest dry matter yield reported by (28). In contrast (9,34) confirmed no yield improvement in cereal/ legume forage mixtures compared to cereal forage sol crops. In many cases, it has been indicated that yields of mixtures between cereals and legumes were intermediate or even lower than yields of monocultures due to competition between the inter-cropped species (18, 33).It was revealed that two crops can be grown at the same field and the risk of growing one crop can be eliminated (1).The superiority of the second harvesting stage was more clear compare to the first stage indicating that the delaying of cutting stage leads to an increase in the yield of green forage, and the reason may be due to the increase in plant height, increase in leaf area and accumulation of dry matter in the later stages of cutting (16,15). The Highly significant differences among crop mixtures were noticed due to LER at both locations and both cutting stage. In most cases the partial LER legume less than partial LER cereals at both cutting stages and both locations. The best values of total LER produced by the crop mixtures triticale/grass pea 1:2 and barley/grass pea 2:1 which were more than unity. Yield advantage in term of LER total was greatest in the case of vetch/Triticale mixture (1.00) and vetch/barley mixture (1.03) when the forage harvested at stem elongation, whereas grass pea mixtures with barley and triticale recorded the greatest values at the booting stage (1.07 and 1.09) respectively (23). Yield advantage in terms of total LER was greatest in the cases pea/barley mixture (34,14) and vetch/barley mixture (34,11), this indicates an advantage from intercropping over pure stands in terms of the use of environmental resources for plant growth and better land utilization (4,11). Regarding to the relative crowding coefficient (RCC or K) value, the K value of cereals were greater than those of legumes in more cases at both cutting stages indicating the dominance of cereals under these crop mixtures. Similarly (11) found that barley and triticale were the dominant species in mixtures with common vetch. The K total was more than one in all cutting dates except for the barley/grass pea mixture in the first cutting date, which indicated a definite yield advantage due to intercropping (5). The partial K value of barley were higher than partial K of legumes in the case of grass pea75/barley25, vetch75/barley25 and vetch50/barley50 intercrops, this indicates that barley is more competitive than associated crops (11). In vetch 25/barley75 mixture, the K value was below one, which indicates that there was a yield disadvantage (12). Concerning to competitive ratio (CR) value for crop mixtures, the competitive ratio of cereals was greater than those of legumes in most cases of crop mixtures, indicating that cereals are more competitive than legumes. Inter-cropped grass pea and vetch had higher competitive in barley50/grass pea50, barley75/grass pea25 and barley75/vetch25 mixtures respectively, indicating that grass pea and vetch is more competitive than barley in these cases. However, in all other mixtures the value of CR for barley was greater than for legumes indicating the dominance of barley under these mixtures. Moreover the value of CR for grass pea was greater than vetch in all mixtures. This indicates that grass pea was more competitive than vetch (13). Aggressivity is another index that is often used to indicate how much the relative yield increase in "a" crop is greater than that of "b" crop in an inter cropping system (20). Generally cereals recorded positive aggressivity, while the legume species showed negative aggressivity values in most cases at both cutting stages. This indicate that cereals were most competitive than legumes and they are the dominant species as measured by the positive value of aggressivity (2,24) suggested that cereals may not always be the dominant crops the intercropping with legumes. AYL cereals had positive values in most crop mixtures, which indicate a yield advantage for cereals because of the positive effect of legume on cereals when grown in association. These results were in a good agreement with those reported by (5,11). Quantification of yield loss or gain due to association with other species could not be obtained through partial LER, where as partial AYL shows the yield loss or gain by its sign and as well as its value (11). The superiority of Kanipanka location in forage yield may be due to the suitability of environmental condition across vegetative growth stage especially the temperature in compare to Qlyasan location (29),while some workers concluded that Qlyasan location gave better values for almost all studied traits, this may be due to the suitability of this location to produce these crops as result of better environmental condition as precipitation amount and its distribution and also the presence of better temperature during growth stage (30). CONCLUSION The greater contribution of legumes was found when common vetch and grass pea were mixed with triticale than with barley. Aggressivity values indicated that triticale and barley were the dominant species in the intercropping system.The system 1cereal : 2legumes were more effective among the studied systems on forage yield and, followed by 1cereal : 1legume system. The predominant of Kanipanka location compared to Qlyasan in green and dry forage characters had explained the suitability of Kanipanka in environmental condition during the growing stage of these crops. Intercropping may lead to a better uses of different limiting production factors, and among them land, time and available financing capacities, than separated monocultures, therefore, land equivalent ratio LER was used to increase production in volume or value through intercropping relative to the respective sole crops.