Introduction

The onion (Allium cepa L.) belongs to the family alliaceae and is one of the oldest cultivated vegetable, for over 4000 years. It is probably originated in central Asia between Turkmenistan and Afghanistan where some of its relatives still grow as wild plants [1]. From central Asia, the supposed onion ancestor had probably migrated to the Near East. Then it was introduced to India and South-East Asia; and into the Mediterranean area and from there to all the Roman Empire [2].

Allium cepa is a popular vegetable everywhere and its bulb is used raw, sliced for seasoning salads, and cooked with other vegetables and meat. The onion bulbs are essential ingredients in many African sauces and relishes. If consumed in small amounts for their pungency, they can be considered as condiments. The leaves, whole immature plants (called ‘salad onion’ or spring onion’), or leafy sprouts from germinating bulbs are used in the same way. In some parts of West Africa, leaves still green at bulb harvest are propounded, and then used to make sun-dried and fermented balls, which are used later for seasoning dishes [2]. The extracted distillate from Allium cepa L., commonly referred as “Onion oil” is extensively used in the food industry as seasoning and flavoring agent for savory products. Onion is considerably important in the daily Ethiopian diet. All the plant parts are edible, the bulbs and the lower section of stem are the most popular as a seasoning or a vegetable in stews.

Onions are rich in two chemical groups that have perceived benefits to human health. These are flavonoids and alk(en)yl cysteine sulphoxide (ACSOs). Two flavonoids sub groups are found in onion, the anthocyanins, which impart a red or purple color to some varieties and flavones such as quercetin and its derivatives responsible for the yellow and brown skins of many other varieties. The ACSOs are the flavour precursors, which, when cleaved by the enzyme alliinase, generate the characteristic odour and taste of onion. The downstream products are a complex mixture of compounds which include thiosulfates, thiosulfonates, mono-, di- and tri-sulfides [2].

Materials and Methods

The investigations were carried out at different aspects in Dr. Y.S. Parmar University of Horticulture and Forestry, Nauni, Solan, Himachal Pradesh. The experimental site is located within 30° 51’ N latitude and 76° 11’ E longitude (survey of India Toposheet No. 55 F/1) at an elevation of 1250 m above mean sea level. The climate of the area is transitional between subtropical to sub-temperate with maximum temperatures risings up to 37.8°C during summer. The mean annual temperature is 19.8°C. In general May and June are the hottest months whereas December and January are the coldest ones. The annual rain fall ranges between 800-1300 mm of which 75 per cent is received during mid June to mid September. Growth and yield of Kaunch (Mucuna pruriens) integrated under Chir pine and without Chir pine (Open) on different aspects and under different tillage practices were studied separately. Hence, studies involved three factors i.e. topographical aspects, tillage practices and systems (crop grown in understorey of Chir pine and in open conditions). Kaunch was grown on three aspects viz Northern (A1), North western (A2) and Western (A3) at a spacing of 30 cm x 30 cm, followed by three tillage depths viz minimum (T1: 0 cm), Medium (T2: up to 10 cm ) and deep tillage (T3: up to 15 cm). The 18 treatments, including all possible combination of three aspects, three tillage depths and two systems were used for the evaluation of velvet bean performance under three replicates in factorial randomized block design.

Experimental field was prepared by removing the pine needles and tillage practices were done just before the onset of monsoon. Plots were prepared as per the treatment details under different tillage practices. The whole experiment was conducted under rain fed conditions entirely dependent on the monsoon rains. Keeping in view the forest site conditions no irrigation and fertilizer was applied and the selection of Velvet bean as medicinal plant was done on the basis of its minimum input requirement for irrigation and fertilizers. For the transplanting of seedlings nursery was prepared and with the commencement of monsoon and after getting the sufficient moisture availability in the soil in first fortnight of July, direct seeding of velvet bean collected from the local plant communities were done in the experimental field. The crop was harvested in the month of December. The observations on growth parameters (vine length, leaf area and leaf area index) were recorded at vegetative, pre-bloom and harvesting stage. Whereas, the data for the yield and the yield attributes were measured at the time of harvesting. To make the economic appraisal for Velvet bean based silvi-medicinal system, the yield of respective species was subjected to economic analysis by calculating cost of cultivation, gross and net returns per hectare.

Results and Discussion

The year wise data pertaining to growth and yield attributes in understorey and open are presented in Tables 1-5 and is described as follows:

Vine length, leaf area and leaf area index did not differ significantly by different topographical aspects and tillage practices in both understorey and open conditions (Table 1). However, on all aspects and under different tillage practices significantly higher value of vine length, leaf area and leaf area index was found in open conditions as compared to understorey of Chir pine. Seed yield did not vary significantly by different topographical aspects and tillage practices in both understorey of Chir pine and open conditions. However, on all aspect and under different tillage practices significantly higher value of seed yield (1.363 t/ha) was found in open conditions as compared to understorey of Chir pine (1.356 t/ha). Similar trend was found with respect to above ground biomass and below ground biomass by different aspects and tillage practices. The yield reduction (0.5 %) in understorey could be because of the lower value of leaf area (Table 1) and below ground dry weight (Table 2) on all aspect and tillage practices than the open conditions. Thus the significantly lower value of all growth character and yield (Table 1-4) in understorey conditions than open condition can be attributed to adverse effect of tree canopy and higher intensity of shade in understorey conditions than the open conditions. This suggests that the plants grown in the open field as sole crop has better opportunities to reap more solar energy for photosynthetic activity, less intra-specific competition for critical resources like water, nutrients, and photo synthetically active radiations. These favorable factors seem to result in higher values of growth parameters and seed yield of velvet bean grown in the open conditions. Chauhan, Karikalan et al., Thakur and Singh [7-10] have earlier made similar observations for different agricultural crop under agroforestry system. Apart from above the lower values of grown parameters and yield attributes in understorey of Pinus roxburghii might be because of the possibility of accumulation of phytotoxin in soil over number of year, which might led to allelopathic interaction with crops, cannot be ruled out.

Bio-economic appraisal of Mucuna pruriens

The total cost of cultivation in Mucuna pruriens have been found different for different treatments which include the fixed and the variable cost. The experiment involving Mucuna pruriens as intercrop clearly indicates higher net returns when crop was growing on northern aspect under minimum tillage in understorey conditions followed by Rs 14,643 ha-1 for crops grown on north western aspect under minimum tillage in understorey conditions. The minimum net returns (Rs. 8685 ha-1) were obtained for crops growing on western aspect under deep tillage in open conditions. In all different treatment combinations, higher net returns were observed in understorey than open conditions (Table 5).

The higher value of gross returns in Mucuna pruriens, in understorey conditions is attributed to the additional returns from the trees, which resulted in average higher gross returns from crops cultivated in understorey conditions than open (Table 5 ).

The positive net returns in case of, Mucuna pruriens may be due to their suitability in the environment given in open conditions and in association with the Chir pine. This finding can be supported by the Harrington et al. [11] who initiated a research to determine the separate effects of above and below ground competition and needles fall from overstorey pines on understorey plant performance and found that depending on species the effects of needle fall were positive, negative, or negligible. While the positive net returns in Mucuna pruriens are attributed to lower cost of cultivation than gross returns (Table 5). The lower cost of cultivation in the given condition can be due to three distinct reasons viz. the lower rental value of land in association with Chir pine in understorey and open conditions; no application of fertilizers and irrigation practices and lower cost of planting material as direct seeding was done in case of Mucuna pruriens in the given conditions.

Thus the successful cultivation of these species namely Mucuna pruriens, can be recommended only in the wasted land having lower rental value like land in association with Chir pine. This finding can be supported by Chatterjee et al. [12] who reported that targeted species like Andrographis paniculata etc. could better flourish on natural ecosystem under in-situ conditions and the conservation and cultivation of these species under controlled cultural practices did not prove to be economically feasible under ex-situ.

Conclusion

As there is a greater demand for Mucuna pruriens in international market and also the pressure on the natural forests for these plants is increasing day by day. Hence in a situation like Chir Pine forests having very less or no understorey growth, the integration of Mucuna pruriens led to the successful performance of Mucuna prurience with positive net returns. Thus Mucuna pruriens and Pinus roxburghii based innovative silvi- medicinal system endeavour to use the unutilized lands of Chir Pine forest by associating vines of Mucuna pruriens to improve the productivity of these forests. This agroforestry model can have a potential implications not only in improving the fertility of soil as velvet beans being nitrogen fixing in nature but also in reducing the fire hazards when pine needles piled up on the forest floor. This study leaves a scope of its implementation in the Chir pine growing belt of the continent if this innovative silvi-medicinal system is adopted by the local farmers or the forest department.

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  Figure 1: Experimental design that was constructed in Menschen fÜr Menschen Demonstration Site, Harar ETHIOPIA.
  T: Treatment; Seed rate: 2.5-3.4kg/ha; B: Block; Net Seed required: 36.72gm; P: Plot; Plot size: 4m2; Between plot: 0.5m; Between Block: 1m; Plot Size: 2mx2m; Number of row/plot: 6; Number of plant/row: 13; Number of plant/plot: 78

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  Table 1: Treatments.

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  Table 2: Effects of increasing rates of N and P on plant height, number of leaves, leaf length and diameter of onion grown at Menschen fÜr Menschen Demonstration Site Harar, ETHIOPIA./p>

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  Table 3: Effects of increasing rates of N and P on neck thickness, split bulbs, bulb diameter and length of onion grown in Menschen fÜr Menschen Demonstration Site, Harar ETHIOPIA.

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  Table 4: Total and marketable fresh bulb yield of onion as affected by different rates of N and P grown in Menschen fÜr Menschen Demonstration Site, Harar ETHIOPIA.