The Performance of Two Species of Black Cumin (Nigella sativa L.) and (Nigella arvensis L.) Under Different Sowing Dates in Spring and Autumn at hallabja Governorate /Iraqi Kurdistan Region

Two field experiments were performed to study the response of two species , Nigella sativa L. and Nigella arvensis L. within different sowing dates at spring and autumn seasons which included 1st and 20th March, 10th April and 1st May for spring season, while the sowing dates for the autumn season were, 2nd November, 21st November, 11th December, 31stDecember and 20thJanuary. Both experiments conducted according to the Completely Randomized Block Design (CRBD) within three replications at hallabja/Kurdistan Region, located [35°12'48.7"N; 45°57'34.4"E] and the altitude was 596 masl. Results showed that among the four different sowing dates of spring cultivations, both species were responded to only 1st and 20th March date with some superiority of the 1st March, otherwise the survival and their yield were not acceptable at sowing date later than 20th March, while at the autumn cultivation, both species responded to all sowing date, but not to be later than 31st December, the early dates 2nd November and 21st November were showed significant differences in most yield traits. The result of the study showed that, due to the favorable environmental condition and the longer period of growth at autumn cultivation, most of the yield traits were gained significant values as the average of both species and different sowing dates of autumn compared to that occurred at spring cultivations. Some chemical contents of both species under the different environment conditions showed significant differences. Generally, N. sativa compared to N. arvensis contained more significant chemical compounds in the term of carbohydrates and protein at autumn, fixed and volatile oils at spring.

to determine the optimum sowing date and its effect on some growth characters, yield and its components, and some chemical compounds. So this study is conducted to determine the seed yield, some yield components and some chemical compounds of the two species of black cumin N. sativa and N. arvensis by different sowing dates in spring and autumn in hallabja province/Iraqi Kurdistan Region.

Material and Methods
Two field experiments were performed to study the effect of two species of the genus Nigella, namely; Nigella sativa and Nigella arvensis within different sowing dates at spring and autumn seasons which included 1 st and 20 th March, 10 th April and 1 st May for spring season, while the sowing dates for the autumn season were, 2 nd and 21 st November, 11 th and 31 st December and 20 th January. Within three replications at hallabja/Kurdistan Region, located [35°12'48.7 " N; 45°57'34.4E] and the altitude was 596 masl. The rainfall during the spring cultivation season was 87.6mm that tends to use supplementary irrigations whenever it was needed, while the amount of the rainfall during the autumn cultivation season was 607.6 mm that was sufficient without irrigations. The soil of the location of the experiment can be described as a clay texture with 2% organic matter. The study included two factors, first was using two species of black cumin which their seeds were obtained from an Iranian company of seed registration (PAKAN BAZR) and the second factor of this study was four and five different sowing dates at spring and autumn season respectively. A factorial experiment 2×4 for the 1 st experiment and a factorial experiment 2×5 for the 2 nd experiment, both were conducted according to completely Randomized-Block Design within three replicates. The land of the study prepared for cultivation by tilling the field two times using mold broad plow and harrow. Seeds of both species of Nigella were cultivated by hand in the 1 st March, 20 th March 10 th April and 1 st May for the spring season experiment, the dates2 nd November,21 st November,11 th December, 31 st December and 20 th January were appointed for the autumn season experiment. The distance between the rows was 20 cm and within the plants was 20 cm also. Each plot area at the spring experiment was 1×1mand at autumn was 2×3 m and consisted of 10 rows. Seeds were sowed at 1-3 cm depths. In the spring season, the experiment was irrigated at any growing stage when it was needed as supplemental to the precipitations, while in the autumn season the crop was grown without irrigation and completely depended on precipitation. The nitrogen fertilization was applied only in one dose, 20 g for each 1×1m at the time of plant height when 10-20 cm. All the necessary cultural practices were similarly applied to the plots during vegetation periods in both seasons. Weeds were controlled by hand when needed. The crop was attended as per routine cultural practices at each season.  Essential oil % v/w: The isolation of the essential oils from the 25g of powdered seeds was done by hydro distillation with Clevenger apparatus for 3h according to the method [18]. And the calculation was as follow:

Seed yield and yield components characters
Ash determination: The Ash determination by using Muffle Furnace in the 550C˚ the reference to method was [19].
Carbohydrates determination: The carbohydrates determination according to [20]. Statistical Analysis: Analysis of variance as a general test was done according to analysis of 2 factors in CRBD, and the means were tested according to least significant difference (LSD) using significant level of 0.05 and 0.01 confirmed by [21]. N. sativa, while the seed weight/plant and seed yield g/m 2 also N. arvensis exceeded N. sativa but insignificantly, but oppositely the significant 1000 seed weight/plant (g) was recorded by N. sativa which was 2.64 g compared to 1.80 g in N. arvensis which mostly due to the longer duration of seed filling stage spend by N. sativa compared to the shorter time spend by N.

Results and Discussions
arvensis.

Autumn Experiment
The effect of the two species of black seed on some yield and yield component traits shown in Table 3. The two species of black seed showed different significant over all the yield and yield component traits. Similar pattern as in the growth characters had been observed, N.
arvensis gave the upper significant limits compared to N. sativa in all yield and yield component traits except the 1000 seed weight (g) which records 2.42 g by N. sativa and it was significant to 1.67 g recorded by N. arvensis may be due to the longer seed filling duration in arvensis compared to N. sativa. The 5.24 g seed weight gained by N. arvensis was significant in comparison to the seed weigh/plant recorded by N. sativa which was only 3.00 g. Finally, the seed yield (g/m 2 ) was 106.73 g/m 2 obtained by N. arvensis and significantly predominated 68.31 g/m 2 seed yields recorded by N. sativa, this predominated seed yield of N. arvensis compare to the N. sativa.  [22]. Were also noticed that different sowing dates significantly affected the No. of umbrella plant -1 in black cumin. As a result of higher fertility ratio in D1 the higher significant No. of seeds also recorded in D1, which were 59.53 seeds/capsule and 3822.87 seeds/plant and the lowest values were 37.80 seeds/capsule and 989.13 seeds/plant recorded in D5, good seed setting condition in early sowing as compared to late sowing was founded in research of [23]. Regarding the 1000 seed weight, D2 gained the highest value 2.20g, insignificantly followed by 2.14 g in D1, they were not significant between themselves, but they were significant compared to other dates, the minimum value was 1.94 equally occurred in D3 and D5. The highest significant value of seed weight/plant was 7.60 g and seed yield 184.43 g/m 2 were obtained in D1 compared to all other dates without exception. The minimum seed weights were 1.63 g/plant and 25.47 g/m 2 recorded in D5. It can be summarized that the early dates especially D1 followed by D2 play a great role in the enhancement of growth and yield production of black seed in the autumn period compared to later sowing dates. On the other hand, sowing at the winter period may be succeeded but because it companied low temperature, caused a weak growth of plants and ultimately decreased seed yield. This agrees with that founded by [24]. Regarding the effect of the interactions on yield traits, the study results showed insignificant differences. Oppositely, the higher 1000 seed weight was 2.22 g recorded by plants of the spring season and a lower 1000 seed weight was 2.04 g recorded by the autumn season. Revealed that there were highly significant differences existed between the two species of black seed that cultivated under different sowing dates in spring and autumn seasons and generally, N. sativa record higher levels of the chemical contents at both seasons especially at autumn compared to N. arvensis, while the ash content observed at higher levels in N. arvensis especially at spring compared to N. sativa. These results were related to that point that the production of secondary metabolites such as essential oil within the seeds of aromatic plants was under diverse physiological, biochemical metabolic and genetic regulation and can be manipulated by alteration in the growing conditions and management of agricultural practices and confirmed by [12,13.14,15]. Regarding to results in Table 6. Carbohydrate% recorded maximum value by N. sativa that cultivated in autumn season that was 58.30% followed by N. sativa grown in spring which was 51.00%, they were highly significantly exceeded N. arvensis at both seasons autumn and spring, which indicated that the soil and environment of hallabja more suitable for growth of N. sativa compared to N. arvensis. Concerning the levels of carbohydrate of black seed that recorded by several researchers were ranged between 24.9-40.0% [25,26]. The confidence interval of this study showed higher levels and ranged between 40.95-55.10%. Similarly, protein content records highly significant level that was 20.60% by N. sativa grown at autumn compared to the rest, but the confidence interval showed the range 14.08-18.76% which was lower compared to the referenced range 20.85-31.20% recorded by [25,26]. Fixed oil content obtained by N. sativa in the spring season and autumn season were 29.66% and 28.31% respectively, followed by Oil content of N. arvensis grown at spring that was 27.36%, were not significant between themselves but they predominated significantly the oil content that recorded by N. arvensis which was only 20.37%. And regarding the lower level and upper level of fixed oil content in this study represented by confidence interval which was 22.99-29.86% it shows a lower range compared to the range recorded by [27,28,29,30]. Which was 31-35%. Volatile oil content that recorded by both species were high and acceptable values to the reference records and the higher levels also were observed in N. sativa at Spring and autumn seasons which were 0.82% and 0.71% respectively followed by 0.65% gained by N. arvensis grown at spring while the 0.62% was the lowest level recorded by N. arvensis grown at autumn season. The confidence interval for volatile oil in this study showed the range 0.62-0.78% has exceeded the range that recorded by [27,28,29,30]. which was 0.4-0.7%. Ash content in black seeds as shown in Table 6. The higher level was 5.30% followed by 4.90% both occurred in N. arvensis grown in spring and autumn respectively, while 2.84% was the lowest level recorded by N. arvensis grown at spring. The range of 3.20-5.17% that shown by the confidence interval of ash content in the seeds of both variety was the following, the range 3.7-4.7% recorded by [25,26].

Conclusions
Based on the obtained results of this study, we can conclude the following: Due to the favorable environmental and the soil condition of Hallabja, both N. sativa and N. arvensis can be cultivated successfully, in the autumn season they can be considered as rainfed crops, while in spring season they need some supplementary irrigations. The early sowing dates always at the both seasons showed superiority in most growth and yield characters, which is due to the longer life period of the crops in early sowing dates. In spring cultivation, the higher yield (25.84) g/m 2 gained by 1 st March sowing date compared to (9.82) g/m 2 of the sowing date in 20 th March, hence, every day delaying in seeding decrease seed yield by (0.8) g/m 2 , this shortage may be due to that at late dates the crop blooming and seed filling stages companied with unfavorable conditions especially, high temperature and low humidity. Also, in autumn cultivation it was concluded that the early sowing dates namely; 2 nd and 21 st November gained 6.24 fold and 3.34 fold increasing in seed yield respectively compared to the lowest yield recorded by 20 th January. Regarding to the difference between the two species, N. arvensis surpassed N. sativa in all characters except the 1000 seed weight that oppositely record higher value in N. sativa compared to N. arvensis. The interaction between species and the sowing dates were insignificantly affected on the traits of the study. Autumn cultivation surpassed significantly in growth characters compared to the spring cultivation as averages of the both species and different sowing dates. Also, the seed yield gained in autumn cultivation was significantly exceeded by 3.9 fold compared to the seed yield in spring cultivation. The seeds of N. sativa that produced at autumn contained the highest level of carbohydrates and protein, which were 58.30% and 20.60% respectively. While, they were gained high levels of fixed and volatile oils in spring cultivation, which were 29.66 and 0.82