الفهرس 
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Abstract
Two crops pea and lettuce were used in the current intercropping study. Pea (Pisum sativum L.) cultivarmaster-B (main crop) and lettuce (Lactuca sativa) cultivar Romaine (secondary crop) were used in the current investigation during growing seasons of 2017/2018 and 2018/2019.The current investigation was conducted to study the effect of intercropping pea (main crop) – lettuce (secondary crop) on the yield and yield components, nutritional quality along with the financial aspect of using different planting arrangement patterns. The experiment design was a randomized complete block (RCBD), with three replicates. The experiment consisted of eighteen plots in total (six treatments and three replications). The treatments of the planting pattern included 4 levels of combination between lettuce and pea plants according to different pea densities i.e., T1 (3 pea plants: 1 lettuce plant), T2 (2 pea plants: 1 lettuce plant), T3 (1 pea plant:1 lettuce plant), T4 (side pea plants: side lettuce plants) in addition to sole lettuce and sole pea treatments. Experimental plot consist of two rows each row was 3 m length and 70 cm in wide. The obtained results could be summarized as follows:
5.1. Results for pea crop
5.1.1.Yield and its components
Results showed that, various intercropping systems significantly affected yield parameters. The significant longest pod length was obtained when intercropping pea with lettuce. While the significant decrease in pod length, pod diameter, and the number of seeds per pod were recorded when pea was grown alone (control treatment). Although non-significant differences in dry matter percentage parameter between intercropping treatments and the control were found in the first season but a slight decrease in the second season was observed when pea was intercropped with lettuce. The values of dry matter percentage decreased significantly when pea was intercropped with lettuce by the ratio of intercropping pea with lettuce by the ratio of 1 pea plant :1 lettuce plant (T1).
Regarding total yield per plant in pea crop, T3 (1 pea plant:1 lettuce plant) treatment produced the maximum values for yields per plant with an average,140.23 and 155.16 g/plant in the two seasons respectively. However, there were no significant differences betweenT3 (1 pea plant:1 lettuce plant) and T2(2 pea plants:1 lettuce plant) in yields per plant parameter in the two seasons of study. Intercropping pea with lettuce by the ratio of 1 pea plant: 1 lettuce plant (T3) produced the lowest value for yields per plant with an average, 117.86 and 125.53 g/plant in the two seasons respectively. The highest total pea yields/feddan were achieved in treatments of sole cropping of pea with 3.039 and 3.25 ton/ feddan and T4 (Side pea: side Lettuce) with 3.018 and 3.212 ton/ feddan in the two seasons, respectively. While the least pea yield was obtained from the treatment of T3 (1 pea plant:1 lettuce plant) as the number of pea plants was the lowest in this treatment. According to the results, it seems that by increasing plant density, the maximum yield in the intercropping system will happen.
5.1.2 Nutritional quality
Regarding the percentage of protein, a significant increase was noticed in all treatments as compared to the control treatment. The percentage of protein in the control pea was 20.63%, 20.48% in the first and second seasons, respectively, then a significant increase was noticed in all treatments under study. So, the protein values in those treatments ranged in the first season from 21.36% to 24.74%. In the same way for the second season, the values were ranged from 21.40% to 24.50%. The T2(2pea: 1lettuce) treatment achieved the highest values for protein in the two seasons.
For the oil contents in the first season, T3 treatment (1pea: 1lettuce) recorded the highest value (2.59%), followed by the control (2.36%) while, in the second season, control treatment had the highest value in oil (1.50%). There was a significant increase in ash values for all intercropping treatments. However, ash contentvalue was the lowest in the control treatment.
For crude fiber contents,T2(2pea: 1lettuce) recorded the highest value for crude fiber in both seasons, where its value was 10.37 in the first season, higher than the control 9.35, and in the second season the value of fiber for same sample was 9.06 compared to 8.65 for the control.
Regarding the total carbohydrates and the caloric value, there was a significant decrease in the value of the total carbohydrates in the treatments under study compared to the control, where the contents for the control were 64.54% and 66.35% for the first and second seasons, respectively, then decreased in the treatments with values ranging from 58.99% to 63.27% in the first season, from 62.09% to 65.23% in the second season. So, as a result of this decrease in the total carbohydrate value, this led to a decrease in the caloric value, as the caloric value (kcal/100g DW) of the control was 361.93 and 360.73 for the first and second seasons, respectively, whereas it decreased in the first season in the rest of the treatments except for T3(1pea: 1lettuce) treatment. It was higher than the control 395.18, while in the second season there was a decrease in all treatments. T3 treatment (1pea: 1lettuce) gave the highest significant values for both total phenols in both seasons and total flavonoids in the 1st season only. While the difference between T3and control treatments for total flavonoids was not significant in the second season. T1 (3pea: 1lettuce) treatment recorded the lowest significant values for total flavonoids contents in both seasons.
5.1.3. Plant nutrient analysis
Results showed that, all intercropping treatments significantly increased the nitrogen percentage. The greatest value of N (3.96% and 3.92%) among all tested treatments was produced byT2(2 Pea:1Lettuce) treatment during first and second seasons, respectively while, the lowest value was recorded by the control treatment, which were 3.30%and 3.28% during the two growing seasons of 2017/2018 and 2018/2019, respectively.On the other hand, data showed that no significant difference was found between T1(3 Pea:1lettuce) and T4(side pea: side lettuce) treatments in first and second seasons. In the current experiment, pea and lettuce used as planting patterns exhibited a significant positive effect on the nutrient uptake than sole grow. The amount of phosphorous in the pea samples, we notice that T2(2 pea plants: 1 lettuce plant) recorded the highest significant values (1379.86 and 1391.33), followed by the control (1272.00 and 1261.83) in both seasons, respectively. Generally, there was a significant decrease in the rest of the treated samples, where the percentage of phosphorous ranged from 1147.17 to 1183.87 in the first season and ranged from 1148.52 to 1158.23 in the second season.
Potassium contents were ranged in the first season from 21726.00 to 23600.70, while in the second season the values were ranged from 21351.46 to 23389.22. With noticed that the T3(1 pea plant: 1 lettuce plant) treatment achieved the highest percentage of potassium compared to the control.
It is also noticed that, regarding calcium values, there was a significant increase in calcium values for all intercropping treatments than the control treatment, which ranged in both seasons between 189.94 and 308.14 in the treatments for the first season, compared to 138.22 for the control, while it ranged from 185.44: 304.07 in the treatments compared to the control 138.31 for the second season.T4 (side pea: side lettuce) treatment achieved the highest significant values in both seasons.
In the same way for the magnesium content, where there was an increase in magnesium values for the intercropping treatments compared to the control in both seasons. T1 (3Pea plants :1 Lettuce plant) treatment recorded the highest significant values for magnesium in both seasons.However, the magnesium values ranged from 212.38 to 258.90 in the treatments compared to the value 185.20 for the control in the first season, while in the second season the values were ranged from 206.58 to 247.99 in the treatments compared 181.21 for control.
For the iron content, there was a significant increase in both of T1 (3Pea plants :1 Lettuce plant) and T2(2Pea plants :1 Lettuce plant) treatments as compared to the control treatment. However, the highest content for iron was recorded for theT2(2Pea plants :1 Lettuce plant) treatment with values of 65.14 and 26.97 in the first and second seasons, respectively, compared to the control (49.22 and 46.57) for the same seasons, respectively. Copper values were present in small quantities and ranged between 0.82: 0.94 for the first season, 0.35: 0.59 for the second season in all samples under study. T2(2Pea plants :1 Lettuce plant) treatment recorded the highest significant value for copper content in the first season, while in the second season there was no difference between T2(2Pea plants :1 Lettuce plant) and T3(1Pea plants :1 Lettuce plant) treatments.
In the same way, regarding to zinc content in pea plant, it is noticeable that there was a significant increase in all intercropping treatments when compared to the control treatment in both seasons. T1(3Pea plants :1 Lettuce plant) treatment surpassed the other intercropping system treatments recording the highest significant value for zinc content in pea plant. Generally, the values for zinc content in pea plant over the intercropping treatments ranged from 12.61 to 17.05 as compared to the control value of 7.07 in the first season, and the values ranged between 11.88: 16.55 in the intercropping treatments as compared to the control value of 6.97 in the second season.
5.2. Results for lettuce crop
5.2.1 Vegetative growth and yield characteristics:
Plant growth characteristics were compared between lettuce plants with and without intercropping. Results of effect of different intercropping treatments showed that, the heaviest weight of fresh leaves of whole plant and the highest number of leaves per plant were obtained by intercropping system treatments in both seasons of study (Table 10) as compared to sole lettuce (control) treatment. However, differences in plant 1height parameter were detected in lettuce plants intercropped with pea crop. T1 (3Pea :1 Lettuce) treatment gave the tallest plant as compared to the other intercropping treatments in both seasons of study.
Intercropping of pea with lettuce seems to have a beneficial effect on lettuce yield under all intercropping systems. Increases in intercropped lettuce yields over the yield of lettuce sole crop were ranged between 12.2% and 37.7% in the first season and between 27.7% and 60% in the second season of study. The trend indicates the following results: 1- an increase in yield of 37.7 % as compared to its sole crop was obtained underT1 (3Pea :1 Lettuce) , 2- an increase in yield of 33.4% compared to its sole crop such as in T2(2Pea :1 Lettuce) treatment, 3- an increase in yield of 21.3% compared to its sole crop such as in T3(1Pea :1 Lettuce) treatment, and4-the increase in yield of was 12.2% in T4 (Side peas :side Lettuce) treatment as compared to its sole crop.Generally, the highest significant total yield per feddan was obtained when planting lettuce with peas as T1 (3Pea :1 Lettuce) and T2(2Pea :1 Lettuce) treatments . However, sole lettuce plants gave the lowest yields in both seasons.
5.2.2.Nutritional quality
The results showed that, moisture content was found in closer ranges in the first and second seasons, reaching 90.35% and 90.25% in the control in both seasons, respectively. Also, we noticed that the moisture percentage was increased in some intercropping treatments compared to the control.
There was a significant difference in the protein content in all intercropping treatments when compared with the control sample, where the percentage of protein in the control samples in the first season and the second season were 27.00% and 26.02%, respectively. The highest percentage in protein content was recorded in T4 (side pea: side lettuce) treatment as it reaches to 28.01% and 28.00% in both seasons respectively. The increasing of the pea plants number compared to lettuce led to a significant decrease in the protein percentage, which ranged in the first season from 24.59% to 26.75%, while in the second season the T1 (3Pea :1 Lettuce) gave the lowest value of protein content as it recorded 24.99% compared to the control treatment.
Regarding oil content in lettuce plant, the ratio in the control treatment for the first and second seasons were 2.25%, 2.73%, respectively. It is noticeable that the percentage of oil was increased in T4 (side pea: side lettuce) treatment as the values of oil content were 2.63%, 3.02% for the first and second seasons, respectively.
There is a significant decrease in the ash content in the intercropping treatments compared to the control in both seasons, where the values were 14.18% and 14.77% for the control in first and second seasons, respectively.
For the crude fibers, it is noticed that in the first season the percentage of fibers in the control was 12.51% while, it was increased in T4 (side pea: side lettuce) treatment as it recorded 12.96%. As for the second season, the content of crude fibers decreased in all treatments compared to the control (13.65%) and the percentage of fibers in the intercropping treatments was ranged from 12.11% to 12.97%.
The total carbohydrate content in lettuce leaf samples had a significant increase in all treatments except for the T4 (side pea: side lettuce) treatment in the first season. Also, the increase in the number of pea plants to lettuce led to a significant increase in the amount of carbohydrates. T1(3 pea plants: 1 lettuce plant) treatment gave the highest value regarding the total carbohydrate content in lettuce leaf as its values were 49.08% and 49.35 % compared with the values of 44.07% and 42.83% for the control treatment in first and second seasons, respectively.
Accordingly, we find that the caloric value (kcal/100g DW) increased in all intercropping treatments when compared to the control. The amount of the caloric value for the intercropping treatments in both seasons ranged from 306.05 to 318.41 compared to their value of 304.49 and 299.95 for the control sample in the first and second seasons, respectively. A significant increment in caloric value for all intercropping treatments due to the increment in the content of protein and total carbohydrates for the samples under study. Generally,Lettuce leaves are one of the very low-calorie green vegetables.
The content of phenolic and flavonoid substances for romaine lettuce leaves, where the value of phenolic substances (mg/100g) was ranged from 2489.13 to 2143.62 in the first season and ranged from 2083.62: 2460.81 in the second season. However, for flavonoid (mg/100g DW) contents in the first season the control treatment was 981.55, while the values were increased in both T1 (3Pea :1 Lettuce) and T4 (Side pea: side lettuce) treatments. While, as for the second season, the control percentage value was 1001.67 but it increased in all intercropping treatments. Generally, regarding the content of phenolic and flavonoid substances for romaine lettuce leaves, we found that T3 treatment (1pea: 1lettuce) gave the highest significant values for both total phenols in both seasons and total flavonoids in the 1st season only while the difference between T3 and control treatments for total flavonoids was not significant in the second season. An increment in total flavonoids was found in T1(3pea:1 lettuce) and T4 (side: lettuce side) treatments in the second season.
5.2.3 Plant nutrient analysis
In the determination process of plant nutrient analysis in lettuce leaves, it was found that intercropping systems had an important effect on the amounts of elements. It was noted that, the greatest value of N among all tested treatments was produced by T4 (side pea: side lettuce) treatment while the lowest value was recorded by T1 (3 pea: 1 lettuce) treatment during the two growing seasons of 2017/2018 and 2018/2019, respectively. However, the difference betweenT4 and either of T2, T3 and the control was significant only in the second season. It was noted that the proportion of potassium, phosphorous, and calcium had a significant decrease in all intercropping treatments under study when compared with control treatment in both seasons. For potassium, the values ranged from 10265.89 to 10800.87 in intercropping treatments when compared to 11583.88 for control treatment, and in the same way for the second season, where the values ranged from 10229.72 to 11316.10 in the intercropping treatments under study, but it recorded 11904.17 for the control treatment. As for phosphorous, the control treatment value was 1505.65 in the first season, 1603.14 in the second season but, it decreased significantly in all intercropping treatments in both seasons, and in the same way for calcium, a significant decrease occurred in all intercropping treatments under study when compared with the control.
The magnesium values for the control were 744.38 and 772.63 for the first and second seasons, respectively, but the values for all intercropping treatments were decreased. The body uses manganese as a co-factor for the antioxidant enzyme, superoxide dismutase.
Regarding iron, T1(3 pea plants: 1 lettuce plant) treatment had the highest values in the first and second seasons, as compared with the rest of the samples under study.
For selenium, all intercropping treatments were significantly lower in their content of selenium as compared to the control. Regarding to zinc, the values for the control treatment were 5.78 and 5.18 for the first and second seasons, respectively, but it is notice that there was an increase in all intercropping treatments as compared to the control.
On the other wise, regarding to the amount of manganese, a significant decrease in the intercropping treatments was observed as compared with the control treatment. Where, the control recorded the values of 14.83 and 14.30 for manganese contents in the first and second season, respectively, but the values were decreased and ranged from 11.91 to 13.55 in the first season and ranged from11.78 to 12.79 in the second season.
5.3. Intercropping efficiency parameters
5.3.1. Land equivalent ratio (LER)
Land equivalent ratio in intercropping treatments was greater than sole cropping. The maximum land equivalent ratio (2.21 and 2.44) was obtained when T1 (3 peas plants:1 lettuce plant) is applied within the first and second seasons respectively. Therefore, intercropping of pea and lettuce, especially at high legume density was appropriate. However, the LER of T3(1 pea plant:1 lettuce plant) recorded the lowest value within the two seasons of study. However, net benefit to the farmer was higher just in case of intercropping pea with lettuce as T1(3 peas plants:1 lettuce plant), followed by pea intercropping with lettuce as T4 (Side pea: side Lettuce), then by applying T2 (2 Pea plants:1Lettuce plant). The LER of all intercropping treatments were greater than 1. This can be a sign of the resource use efficiency of pea/lettuce intercropping system. Also, indicating a higher combined yield was produced than for mono-cropped pea.
5.3.2.Aggressiveness
Calculated “aggressiveness” proved that all secondary crop treatments were more dominant and were strong competitor than pea in all intercropping treatments.Aggressivity index showed that pea intercropped with lettuce as T3 (1 Pea plant: 1Lettuce plant) treatment gave the best value. However,Intercropping had sufficient economic benefits during this mixture.
5.3.3. Monetary advantage index (MAI)
Calculatingmonetary advantage index (MAI) is considered an indicator of the economic feasibility of cropping systems, results showedthat, alltreatments gave positive values of MAI because the LER values were greater than one. Indicated that the best MAI values of 33576.67 and 37195.67 were obtained from intercropping pea with lettuce by the ratio of 3Pea plants: 1 Lettuce plant (T1)treatment in both seasons respectively, followed byT4 (Side pea: side Lettuce) treatment (Table 17) followed by T2 (2Pea plants: 1 Lettuce). While, in case of intercropping pea with lettuce by the ratio of 1Pea plants: 1 Lettuce plant (T3)treatment resulted within the lowest value for MAI.
CONCLUSION
The obtained results of current investigation might be showed that successful intercropping system could be occur when each crop occupies and accesses resources from different ecological niches while reducing competitive interactions. The obtained results revealed that, intercropping lettuce with pea was more effective than planting pea crop alone, as it increased the lettuce yield by 12.2%-37.7% and 27.7%- 60 % in the first and second seasons respectively according to the intercropping system applied. All intercropping treatments except for T4 (side pea: side lettuce) treatment reduced the pea yield. The highest pea yields were produced by both sole pea andT4 treatments, while the lowest pea yield was form T3, in both seasons. T3 treatment depressed pea pod yield to 60% of its mono-cropped yield. On the other hand, T1 and T2 treatments produced the highest yield for lettuce in both seasons. Results of the chemical, mineral analysis, the phytochemical compounds of both lettuce leaves and green pea seeds that intercropping lettuce, a leafy plant on the pea, which is a root plant led to an improvement in the quantities of most of the compounds in the pea, especially the protein percentage, which increased in the pea as a result of the intercropping process. On the other hand, there was a decrease in most lettuce compounds. Therefore, it can be recommended to intercrop 3 plants from a pea into a lettuce plant so that a high-quality crop of green peas can be obtained that contains larger quantities of nutrients, whose role is reflected in human health. an improvement in the protein percentage in pea. LER of pea/lettuce intercropping treatments were more than unit. Moreover, the highest values for both LER and MAI obtained fromT1 treatment. Calculated “aggressiveness” suggested that all secondary crop treatments were more dominant than pea in all intercropping treatments. from this study it could be concluded that, the intercropping system of 3pea:1 lettuce could be a gainful system to obtain the greatest use efficiency of land.