Introduction

Elephant foot yam has been originated from India and belongs to family araceae. The tubers serve as a cheap source of energy especially for weaker sections of the society and has many medical benefits such as stomachic, restorative, carminative and also act as a tonic. Due to its high photosynthetic efficiency and high dry matter production capability per unit area, substantial yields may be obtained even under poor and marginal soils under harsh climatic conditions. The cultivation of this crop has gained momentum in India after the introduction of non-irritant smooth corm type cultivars like Gajendra. Traditionally, elephant foot yam is propagated through corms and cormels. Whole corm or cut corm pieces weighing about 500 g to 750 g with a part of apical meristem is mainly used as planting material. A great portion (about 25 per cent) of the harvested produce is lost as source of planting material. At times, it is very difficult to provide a large quantity of quality planting materials to the farmers. However, very little information is available on the effect of dipping of seed corms (minisetts) before planting with organic and inorganic substances.

Materials and Methods

The experiment was conducted at Research and Instructional Farm of Department of Horticulture, Indira Gandhi Krishi Vishwavidyalaya, Raipur, Chhattisgarh during Kharif season of the years 2010-11 and 2011-12.The experiments were laid out in Randomized Block Design (RBD) with fifteen treatments and three replications.The treatment consisted of different concentrations of organic and inorganic substances which were applied as pre-planting soaking of corms i.e.T₁ (cow dung 50 % + water 50 %),T₂ (cow urine 50 % + water 50 %),T₃ (cow dung 25 % + cow urine 25 % + water 50 %),T₄ (cow dung 37.5 % + cow urine 37.5 % + water 25 %),T₅ (cow dung 50 % + cow urine 50 %), T₆ (thiourea at 200 ppm), T₇ (thiourea at 300 ppm),T₈ (thiourea at 400 ppm), T₉ (KNO₃ at 250 ppm), T₁₀ (KNO₃ at 500 ppm),T₁₁ (KNO₃ at 750 ppm), T₁₂ (GA₃ at 100 ppm), T₁₃ (GA₃ at 200 ppm), T₁₄(GA₃ at 300 ppm) and T₁₅ (control treatment) i.e. soaking of minisetts in water.

The observations on different growth and yield parameters were recorded on ten randomly selected plants in each treatment and three replications. Height of the plants was measured with the help of meter scale from base of pseudo-stem to the top of the leaf at 80, 100 and 120 DAP. Average height was calculated and expressed in centimeters. Girth of stem at  5 cm above ground level was measured with the help of a measuring tape from bottom, medium and top portion of the pseudo-stem of plant at 80, 100 and 120 DAP. Average girth of pseudo-stem was calculated and expressed in centimeters. Number of pseudo-stems of each randomly selected plants was counted at 80, 100 and 120 DAP and average was calculated and expressed in numbers. Canopy spread at 80, 100 and 120 DAP was measured with the help of a measuring tape in East-West and North-South directions of the compass and average values were computed and expressed in centimeters. Experimental field was visited daily to observe the days taken to first senescence, days taken to 50 per cent senescence and days taken to complete senescence (maturity) under different treatments. The number of days taken for first senescence from the date of planting were counted and expressed in days. Number of days taken for senescence of half the number of total plants from the date of planting was counted and expressed in days and the days taken to complete senescence (maturity) from date of planting and expressed in days. The harvested corms were measured with the help of a measuring tape and average values were computed and expressed in centimeters. The observations on corm yield per plant were recorded at the time of harvesting with the help of physical balance and expressed in kilogram. The corm yield per plot was recorded at the time of harvesting in kilograms and average yield per hectare was computed and expressed in tonnes.

Results and Discussion

Plant height: The height of the plant increased with the advancement of plant growth up to 120 DAP (Table 1). Pre-planting treatments of minisetts with T₈i.e.thiourea at 400 ppm (48.36 cm, pooled data) gave significantly highest plant height followed by T₇i.e.thiourea at 300 ppm (47.65 cm, pooled data) and T₉i.e. KNO₃ at 250 ppm (44.64 cm, pooled data). The taller plant under this treatment might be due to early sprouting observed under the present study. Similar results were reported by Ravi et al. (2009).Das et al.(1995) reported that plant height of elephant foot yam was higher under thiourea (300 ppm) and KNO₃ (750 ppm) at 120 DAP. Similar results have been reported in increasing the plant height of potato by Germchi et al. (2011).

Table 1 Effect of pre-planting treatments of minisett corms with different organic and inorganic substances on plant height at 80, 100 and 120 DAP in elephant foot yam cv. Gajendra Note: DAP – Days after planting

Pseudo-stem girth: The girth of pseudo-stem increased with the advancement of crop growth up to 120 DAP (Table 2) which was significantly influenced by various pre-planting treatments at different stages of plant growth i.e. 80, 100 and 120 DAP. The maximum pseudo-stem girth was recorded under T₈i.e.thiourea at 400 ppm (9.52 cm, pooled data) followed by T₇i.e.thiourea at 300 ppm (9.42 cm, pooled data) and T₉i.e. KNO₃ at 250 ppm (9.28 cm, pooled data). Mondal et al. (2005) reported higher pseudo-stem girth with thiourea and KNO₃ treatment in elephant foot yam. In the present study the cow dung based pre-planting treatments (T₁ to T₅) were also found to show significant improvement (8.89 to 8.96 cm, pooled data) in this feature over control treatment (soaking of minisetts in water). Mondal et al. (2005) have also obtained higher pseudo-stem girth with the use of cow dung slurry.

Table 2 Effect of pre-planting treatments of minisett corms with different organic and inorganic substances on pseudo-stem girth at 80, 100 and 120 DAP in elephant foot yam cv. Gajendra Note: DAP – Days after planting

Number of pseudo-stems plant^-1: The number of pseudo-stems plant^-1at different stages of plant growth i.e. 80, 100 and 120 DAP was significantly influenced by various pre-planting treatments which increased with the advancement of crop growth up to 120 DAP (Table 3). The pre-planting treatment of minisetts with T₈i.e.thiourea at 400 ppm, T₉i.e. KNO₃ at 250 ppm, T₇i.e.thiourea at 300 ppm and T₁₀i.e. KNO₃ at 500 ppm gave the highest number of pseudo-stems plant^-1 (4.23 to 4.34, pooled data) which were found to be superior to the rest of the treatments. GA₃ at all the concentrations i.e.100, 200 and 300 ppm did not give significant response towards improvement of this character.

Table 3 Effect of pre-planting treatments of minisett corms with different organic and inorganic substances on number of pseudo-stems plant-1 at 80, 100 and 120 DAP in elephant foot yam cv. Gajendra Note: DAP – Days after planting

Das et al.(1995) reported that number of pseudo-stem hill^-1 increased with crop age up to 120 DAP and Germchi et al. (2011) indicated highest number of stems plant^-1with the use of thiourea in potato. The improvement in number of pseudo-stems plant^-1under thiourea and KNO₃ pre-planting treatments could be attributed to increase in vegetative growth characters of crop under these treatments in the present study.

Canopy spread: The canopy spread was significantly influenced at different stages of crop growth at 80, 100 and 120 DAP which attained the maximum coverage at 120 DAP (Table 4 to 6). Pre-planting treatment of minisetts with thiourea at 300 and 400 ppm gave the highest canopy spread (42.25 to 42.37 cm, pooled data) followed by KNO₃ at 250 and 500 ppm (40.29 to 40.69 cm, pooled data) which were significantly superior to rest of treatments. Maximum canopy spread under these treatments could be attributed to early sprouting observed under present investigation. The cow dung based pre-planting treatments (T₁ to T₅) also showed better response towards increasing canopy spread at all the stages which may also be attributed to early sprouting observed in these treatments.

Table 4 Effect of pre-planting treatments of minisett corms with different organic and inorganic substances on canopy spread at 80 DAP in elephant foot yam cv. Gajendra Note: DAP – Days after planting

Table 5 Effect of pre-planting treatments of minisett corms with different organic and inorganic substances on canopy spread at 100 DAP in elephant foot yam cv. Gajendra Note: DAP – Days after planting

Table 6 Effect of pre-planting treatments of minisett corms with different organic and inorganic substances on canopy spread at 120 DAP in elephant foot yam cv. Gajendra

These results corroborate the findings of Mondal et al. (2005) who indicated the increase in canopy spread with pre-planting treatment of thiourea, KNO₃ and cow dung slurry in elephant foot yam. In the present study canopy spread was presumably due to early sprouting and better root ramification as reported by Sen and Das (1991).

Days to first senescence and days to 50 per cent senescence and days to maturity

The maximum number of days to first senescence (Table 7) was recorded under T₈ i.e.thiourea at 400 ppm (154.83, pooled data) followed by T₆ and T₇ (thiourea at 200 and 300 ppm) i.e. 154.17 (pooled data), T₅ and T₉ (cow dung 50% + cow urine 50% and KNO₃ at 250 ppm) i.e. 153.83 (pooled data). The minimum number of days to first senescence was observed under T₁₅i.e. control treatment(150.00, pooled data) followed by T₁₂ (GA₃ at 100 ppm) i.e. 150.83 (pooled data), T₁₃ (GA₃ at 200 ppm) i.e. 151.17 (pooled data) and T₁₄ (GA₃ at 300 ppm) i.e. 152.00 (pooled data).

Almost similar trend was noticed in case of days to 50 per cent senescence and days to maturity. In case of days to 50 per cent senescence (Table 7), the maximum number of days to 50 per cent senescence was recorded under T₈ (thiourea at 400 ppm) i.e. 164.67 (pooled data) followed by T₇ (thiourea at 300 ppm) i.e. 164.17 (pooled data), T₆ (thiourea at 200 ppm) i.e. 163.67 (pooled data) and T₉ (KNO₃ at 250 ppm) i.e. 163.00 (pooled data). The minimum number of days to 50 per cent senescence was observed under T₁₅i.e. control treatment(157.83, pooled data) followed by T₁₃ (GA₃ at 200 ppm) i.e. 158.50 (pooled data), T₁₂ and T₁₄ (GA₃ at 100 and 300 ppm) i.e. 158.67 (pooled data).

Table 7 Effect of pre-planting treatments of minisett corms with different organic and inorganic substances on days to first senescence, days to 50 per cent senescence and days to maturity in elephant foot yam cv. Gajendra

The maximum number of days to maturity (Table 7) were recorded under T₈ (thiourea at 400 ppm) i.e. 180.33 (pooled data) followed by T₇ (thiourea at 300 ppm) i.e. 180.17 (pooled data), T₆ and T₉ (thiourea at 200 ppm and KNO₃ at 250 ppm) i.e. 179.17 (pooled data). The minimum number of days to maturity was observed under T₁₅i.e. control treatment(173.00, pooled data) followed by T₁₂ i.e. GA₃ at 100 ppm (174.17, pooled data) and T₁₄ i.e. GA₃ at 300 ppm (174.33, pooled data).

In the present study, it was observed that there was a distinctive increase in the corm yield with the more number of days the crop was on field and late harvesting resulted in maximum corm diameters resulting into greater tuber yield plant^-1. This was in accordance with the findings of Liu and Chen (1986) who reported that the seed corm bulking is more related to time of harvest and the senescence is more pronounced in late harvest crop when compared to early and mid season harvest. This could be due to the fact the crop has long period to synthesize photosynthates and their translocation to the tubers and the fullest utilization of photosynthates to store in the tubers at the time of senescence. Similar results were reported by Bhagavan (2005) in elephant foot yam.

Diameter of corms: Table 8 indicated that the corm diameter was highest under T₇ i.e. thiourea at 300 ppm (7.34 cm, pooled data) followed by T₈ i.e. thiourea at 400 ppm (7.33 cm, pooled data) and its lower concentration at 200 ppm (7.16 cm, pooled data). KNO₃ at all the concentrations were the next best treatments in increasing the diameter of corms. This could be presumably due to early sprouting of minisetts in these treatments which resulted into sufficient vegetative growth and canopy spread which in turn after photosynthesis, increased the photosynthetic assimilates and these assimilates were transported to the resulting corms thereby increasing their diameter as reported by Kumar et al. (2009). Ample energy may be made available for the bulking of corms due to improvement in vegetative characters of plants. Similar results were reported by Mohan kumar et al. (1973).

Table 8 Effect of pre-planting treatments of minisett corms with different organic and inorganic substances on diameter of corm and corm yield plant-1 in elephant foot yam cv. Gajendra

Corm yield plant^-1: Table 8 indicated the highest corm yield plant^-1 under thiourea at all the concentrations i.e.200, 300 and 400 ppm (0.522 to 0.540 kg, pooled data). Similar results were reported by Germchi et al. (2011) who reported the increasing tuber yield with the use of thiourea in potato. Among the cow dung based treatment, the T₅ i.e. cow dung 50 % + cow urine 50 % (0.506 kg, pooled data) was next best treatment to thiourea in increasing the corm yield (kg plant^-1) and which was statistically as effective as KNO₃ (250 and 500 ppm) pre-planting treatment.

The findings can be supported by those of Mondal et al. (2005) who reported highest corm weight plant^-1 with thiourea, KNO₃ and cow dung slurry. The highest corm yield plant^-1 could further be attributed to enhancement of sprouting, encouragement of girth of pseudo-stem resulting into higher corm yield plant^-1in the present study. The highest pseudo-stem girth, canopy spread and corm diameter was observed under these treatments in the present study.

Corm yield: The data on corm yield (t ha^-1) are  presented in Table 9 and revealed that the pre-planting treatments of corm setts of elephant foot yam with different organic and inorganic substances registered an increased in average corm yield from 9.41 to 31.07 per cent over control treatment (soaking of minisetts in water) and the highest corm yield (12.24 to 12.57 t ha^-1, pooled data) was obtained with thiourea at all the concentrations  (200, 300 and 400 ppm)which were found to be statistically equal in increasing the corm yield. These were closely followed by KNO₃ at 250 ppm (12.11 t ha^-1, pooled data). In general, all the cow dung based pre-planting treatments (T₁ to T₅) gave better response to productivity due to enhanced sprouting but were found comparatively less superior to rest of the treatments except GA₃.

Table 9 Effect of pre-planting treatments of minisett corms with different organic and inorganic substances on corm yield in elephant foot yam cv. Gajendra

Mondal et al. (2005) obtained the highest corm yield of elephant foot yam with cow dung slurry treatment because of improvement in sprouting and vegetative growth of the crop plant. In the present study the corm yield did not show much improvement under cow dung based treatment in comparison to rest of treatments which might probably be due to comparatively low percentage of sprouting.

The results in relation to thiourea and KNO₃ in increasing the corm yield are in conformity of Das et al. (1995) who reported outstanding performance of these substances in increasing the corm yield. The increase in corm yield in these treatments might be ascribed to comparatively  greater individual growth and development of plants due to early sprouting and vigour and in the present study, corm yield plant^-1 was greater under these treatments which resulted into total corm yield. The result can be supported with the fact that plant height, pseudo-stem girth, canopy spread, corm diameter and dry matter content of corms under these treatments have shown significant improvements which resulted into greater corm yields.

Conclusion

In the present investigation, significantly greatest improvement was achieved in plant height, pseudo-stem girth, number of pseudo-stem plant^-1 and canopy spread under T₇ and T₈ (thiourea at 300 and 400 ppm) pre-planting treatments. Thiourea at higher concentration i.e. 400 ppm took significantly maximum number of days to first senescence, days to 50 per cent senescence and delayed maturity in elephant foot yam. The pre-planting corm dipping in thiourea at concentration of 300 and 400 ppm produced significantly maximum diameter of corm and those treatments (thiourea at 300 and 400 ppm) was statistically equally effective in producing maximum corm yield (kg plant^-1). Maximum values of corm yield (t ha^-1) being under thiourea at 400 ppm and there was also increase in per cent corm yield under this treatment over control treatment.

Acknowledgement

I am grateful to Head, Department of Horticulture, College of Agriculture, Raipur and Director Research Services, Indira Gandhi Krishi Vishwavidyalaya, Raipur (C.G.) for proving necessary facilities and infrastructure for this study.

References

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