Performance of baby corn ( Zea mays L . ) as influenced by spacing , nitrogen fertilization and plant growth regulators under sub humid condition in Rajasthan , India

A field experiment was conducted during kharif 2010 and 2011 at Instructional farm of Rajasthan College of Agriculture Udaipur, Rajasthan, India to study the effect of crop spacing (45 × 20, 60 × 15 and 90 × 10 cm), nitrogen levels (60, 90 and 120 kg ha -1 ) and plant growth regulators (control, N-acetyl Aspartate (NAA) at 40 ppm and mepiquat chloride at 200 ppm) on yield attributes, yield and economics of baby corn. The crop spacing 60 × 15 cm significantly influenced yield attributes. Maximum green cob yield, baby corn yield and green fodder yield was recorded at 60 × 15 cm spacing which was higher (14.0, 24.3 and 8.8%, respectively) over 90 × 10 cm. Increasing nitrogen levels up to 90 kg ha -1 markably improved the yield attributes, yields and net returns. Application of 90 and 120 kg N ha -1 exhibited significant increase in green cob yield over 60 kg N ha -1 . The results revealed that application of nitrogen up to 90 kg ha -1 level significantly increased green cob yield and baby corn yield in tune of 20.5 and 23.6% as compared to 60 kg N ha -1 . The mepiquat chloride at 200 ppm exhibited highest yield parameters viz. cob length, cob girth, cob weight, corn length, corn girth, corn weight and cobs plant -1 . The crop sprayed with mepiquat chloride produced highest green cob yield (5903 kg ha -1 ), baby corn yield (2083 kg ha -1 ) and this was comparable with application of NAA. In case of green fodder yield, NAA at 40 ppm produced significantly highest green fodder yield (26.9 t ha -1 ) over mepiquat chloride at 200 ppm (22.1 t ha -1 ).

) and plant growth regulators (control, N-acetyl Aspartate (NAA) at 40 ppm and mepiquat chloride at 200 ppm) on yield attributes, yield and economics of baby corn.The crop spacing 60 × 15 cm significantly influenced yield attributes. Maximum green cob yield, baby corn yield and green fodder yield was recorded at 60 × 15 cm spacing which was higher (14.0, 24.3 and 8.8%, respectively) over 90 × 10 cm.Increasing nitrogen levels up to 90 kg ha -1 markably improved the yield attributes, yields and net returns.Application of 90 and 120 kg N ha -1 exhibited significant increase in green cob yield over 60 kg N ha -1 . The results revealed that application of nitrogen up to 90 kg ha -1 level significantly increased green cob yield and baby corn yield in tune of 20.5 and 23.6% as compared to 60 kg N ha -1 . The mepiquat chloride at 200 ppm exhibited highest yield parameters viz.cob length, cob girth, cob weight, corn length, corn girth, corn weight and cobs plant -1 .The crop sprayed with mepiquat chloride produced highest green cob yield (5903 kg ha -1 ), baby corn yield (2083 kg ha

INTRODUCTION
Baby corn is dehusked maize ear, harvested young especially when the silk have either not emerged or just emerged and no fertilization has taken place or we can say the shank with unpollinated silk is baby corn.Baby corn ears in light yellow colour with regular row arrangement, 10 to 12 cm long and a diameter of 1.0 to 1.5 cm arrangement are preferred in the market (Muthukumar et al., 2005).The economic product is harvested just after silk emergence (1 to 2 cm long).Baby corn is an important crop of Thailand and Taiwan and in India; recently, baby corn has gained popularity as valuable vegetable in Delhi, Uttar Pradesh, Haryana, Maharashtra, Karnataka, Andhra Pradesh, Rajasthan and Meghalaya States of India.In India, it is grown on 8.5 *Corresponding author.E-mail: slagro_1967@yahoo.co.in.Tel: 09602518801.m ha area with the production and productivity of 21.3 m t and 2507 kg ha -1 , respectively (Government of India, 2011).Rajasthan State was first in respect of area, where in this crop occupies 10.5 lakh ha area (12.9%) with production of 19.5 lakh tones and productivity of 18.6 q ha -1 (Government of Rajasthan, 2010).
In order to achieve higher ear yields, maintenance of stand density is the most important factor.A spatial arrangement of plant governs the shape and size of the leaf area per plant, which in turn influences efficient interception of radiant energy and proliferation and growth of shoots and their activity.Maximum yield can be expected only when plant population allows individual plant to achieve their maximum inherent potential.Thus, there is need to work out an optimum plant spacing by adjusting inter and intra row spacings in relation to other agronomic factors.Nitrogen is a key element for achieving higher productivity of maize in southern Rajasthan (Mehta et al., 2005).Maize is an exhaustive crop and requires high quantities of nitrogen during the period of efficient utilization, for higher productivity.Nitrogen is indispensable for increasing crop production as a constituent of protoplasm and chlorophyll and is associated with the activity of every living cell.Plant growth regulators improve the effective partitioning and translocation of accumulates from source to sink in the field crops.NAA, being an auxin, promote vegetative growth by active cell division, cell enlargement and cell elongation and thus, helped in improving growth characteristics and in stimulating reproductive growth.NAA application significantly enhanced the fodder yield over other treatments (Muthukumar et al., 2005).Increase in fodder yield due to NAA spray might be due to increase in plant height, leaf area index and total biomass, which might be due to increased cell division, cell enlargement and elongation.Growth regulators spray had positive influence on green cob yield of baby corn.The increase in yield due to mepiquat chloride spray has been attributed to increased yield attributes, which in turn resulted from effective translocation of photosynthesis from source to sink due to the shortening of distance between source and sink.Since mepiquat chloride is a growth retardant, it resulted in reduced plant height and dry matter production and finally reduction in fodder yield.Cob yield increases due to increased mobilization of reserve food materials to developing sink through increase in hydrolyzing and oxidizing enzyme activities.
Thus, present investigation was carried out to assess effect of spacing, nitrogen levels and plant growth regulators on yield attributes and yield of baby corn under sub-humid condition in Rajasthan, India.

MATERIALS AND METHODS
A field experiment was conducted during kharif 2010 and 2011 on clay loam soil at Instructional Farm, Rajasthan College of Agriculture, Udaipur, which is situated at 23°34' N latitude, 73°42' E longitude and at an altitude of 582.2 m a.m.s.l.Soil was slightly alkaline pH (7.9), medium in available nitrogen (268.4 kg ha -1 ) and available phosphorus (20.8 kg ha -1 ) and high in available potassium (290.5 kg ha -1 ).The total precipitation during crop growing period was 637.4 mm in 2010 and 757.4 mm in 2011.Maximum and minimum temperature during baby corn crop growing period ranged between 35 to 27.1°C and 25.9 to 16.1°C, respectively during year 2010.The corresponding fluctuations during second year were to 23.7°C and 29.1 to 20°C.The experiment was laid out in split plot design with three replications.The treatments comprised combinations of three spacing levels (45 × 20 cm, 60 × 15 cm and 90 × 10 cm), three nitrogen levels (60, 90 and 120 kg ha -1 ) allocated in main plots and three plant growth regulators levels (control, NAA at 40 ppm and mepiquat chloride at 200 ppm) in sub-plots, thereby making 27 treatment combinations.Half nitrogen dose and full phosphorus dose was applied as basal before sowing in each plot.Remaining half nitrogen was top dressed at knee high stage as per treatments.Plant growth regulators were sprayed as control, NAA (40 ppm) and mepiquat chloride (200 ppm) at 25 and 35 days after sowing (DAS).Baby corn variety HM-4 was sown manually at varying row spacing as per treatment.Crop was harvested at just after silk emergence.Length, girth and weight of the cob from representative plants were measured from which mean values were attained.Cob sheath of tagged plants in each plot was peeled-off and the length, girth and weight of corn inside the sheath were measured.Number of cobs from the tagged plants was counted and from that mean number of cobs was calculated.The cobs from net area of each plot were harvested separately, weighed and recorded as young cob yield (kg ha -1 ).

Statistical analysis
The data on the observations made were analyzed statistically by applying the technique of analysis of variance for split plot design and significance was tested by F-test.Critical difference for examining treatment means for their significance was calculated at 5% level of probability.Standard error of mean and critical difference on interaction is presented only where ever there is significant difference among the treatments statistical analysis as per procedure suggested by Cocharan and Cox (1967).

Yield attributes and yield
The study revealed that yield components viz.cob length, cob girth, cob weight, corn length, corn girth, corn weight at first and third harvest and cobs plant -1 were influenced significantly by varying plant spacing (Tables 1 and 2, and Figures 1 to 3).There was significant improvement in length, girth and weight. of cob and corn, and numbers of cobs/plant with increasing spacing 60 × 15 cm as compared to 90 × 10 cm but was observed statistically at par with 45 × 20 cm.The crop spacing 60 × 15 cm might have resulted in higher photosynthesis and finally higher plant -1 dry matter accumulation.Higher dry matter is believed to have maintained adequate supply of metabolites for development of reproductive structures.The significantly higher green cobs, baby corn and green fodder yields of baby corn were obtained under spacing with 60 × 15 cm over 90 × 10 cm and at par with 45 ×     cm (Table 3 and Figures 4 and 5).Crop spacing of 60 ×15 cm, recorded highest green cob and baby corn yield 5759.2 and 2065.1 kg ha -1 and green fodder yield 27. 9 t ha -1 , respectively.Observed marked increases in baby corn yield appear to a resultant of remarkable improvement in different yield attributes which was brought about due to adoption of this crop spacing.This view is close conformity with the findings of Sarkar et al. (1996), Prodhan et al. (2007) and Aravinth et al. (2011), who recorded higher yields as a result of remarkable improvement in different growth and yield attributes when this crop was grown at spacing of 60 × 15 cm instead of other spacings.

Yield attributes and yield
The results indicated that application of increasing nitrogen up to 90 kg ha -1 significantly improved cob length, cob girth, cob weight, corn length, corn girth, corn weight and cobs plant -1 (Tables 1 to 2 and Figures 1 to  3).A faster growth under influence of higher level of nitrogen fertilization might have played a significant role in reducing competition for photosynthates and nutrients with other plants resulting in healthy plants.The increased availability of photosynthates might have enhanced number of flowers and their fertilization resulting in higher number of yield attributes.Further, in most of cereals, greater assimilating surface at reproductive developments results in better green cob formation because of adequate production of metabolites and their translocation towards cob.The results of present investigation indicating positive response of various yield attributes to higher nitrogen fertilization corroborate findings of several researchers (Chillar and Kumar, 2009;Bindhani et al., 2007;Gosavi and Bhagat, 2009).
The results revealed that application of 90 and 120 kg N ha -1 were found at par and both these levels exhibited significant increases in green cob yield over 60 kg N ha -1 .The results revealed that application of nitrogen up to 90 kg ha -1 level significantly increased green cob yield and baby corn yield in tune of 20.5 and 23.6% as compared to 60 kg N ha -1 (Table 3).
The higher green cob yield realization with application of higher nitrogen could be ascribed to its profound influence on vegetative and reproductive growth of the crop (Prodhan et al., 2007).The results of the present investigation are in accordance with findings of Raja (2001), Thakur and Sharma (1999) and Kumar (2009).
Application of 120 kg N ha -1 level registered significantly the highest green fodder yield over 60 and 90 kg N ha -1 levels.Application of 120 kg N ha -1 registered significantly the highest green fodder yield  (26.9 t ha -1 ) by 32.4 and 3.1% over 60 and 90 kg N ha -1 , respectively.Application of 120 kg N ha -1 recorded significantly the highest green fodder.The higher green fodder yield under the influence of increasing nitrogen fertilization levels up to 120 kg ha -1 level could be ascribed to its positive influence on both vegetative and reproductive growth of the crop which led to increase in green cob, baby corn and green fodder yields ha -1 .These results are in line with Sahoo and Mahapatra (2007), Gosavi and Bhagat (2009) and Gulabrao (2010) as they also found increased green fodder yield with increased level of nitrogen.

Yield attributes and yield
Growth regulators had positive influence on yield parameters of baby corn.Crop sprayed with mepiquat chloride at 200 ppm had highest values of yield parameters viz., cob length, cob girth, cob weight, corn length, corn girth, corn weight and cobs plant -1 (Tables 1  to 2, and Figures 1 to 3).However, this was comparable with application of NAA at 40 ppm.Mepiquat chloride at 200 ppm spray was significantly superior over control for all yield parameters. Increase in yield parameters due to mepiquat chloride spray might be ascribed to effective translocation of photosynthates from source to sink which resulted from shortening of distance between sources and sink (Muthukumar et al., 2005).Mepiquat chloride as a growth retardant would have arrested the excessive growth and thus minimized transpiration losses and increased the chlorophyll content of the plants to supply photosynthates for its larger sink and thereby increased the yield attributes of the treated plants (Muthukumar et al., 2005).NAA, being an auxin, promoted vegetative growth by active cell division, cell enlargement and cell elongation and thus, helped in improving growth characteristics and also in stimulating reproductive growth

Spacing
Nitorgen levels PGR (Muthukumar et al., 2005).The results of present investigation indicating positive response of various yield attributes to plant growth regulators corroborate findings of several researchers (Muthukumar et al., 2005;Rathika et al., 2009;Mohamed et al., 2010).Spray of mepiquat chloride at 200 ppm significantly increased green cob and baby corn yield as compared to control but was statistically at par with NAA at 40 ppm (Table 3).
The crop sprayed with mepiquat chloride exhibited highest green cob yield (5903.03 kg ha -1 ) and this was comparable with application of NAA (5767.64 kg ha -1 ).The increase in yield due to mepiquat chloride spray might be due to increased translocation of photosynthates from source to sink due to the shortening of distance between sources to sink (Muthukumar et al., 2005).
Cob yield increased due to increased mobilization of reserve food materials to developing sink through increase in hydrolyzing and oxidizing enzyme activities (Velu, 2002).NAA, being an auxin, promoted vegetative growth by cell division, cell enlargement and cell elongation and thus helped improving growth characteristics and also in stimulating reproductive growth (Muthukumar et al., 2005).
The results of the present study indicating positive response of baby corn to plant growth regulators also corroborate the findings of several research workers (Muthukumar et al., 2005;Rathika et al., 2009;Mohamed et al., 2010).
Application of growth regulators exhibited significant influence on green fodder.NAA at 40 ppm registered significantly higher green fodder yield (26.9 t ha -1 ). Application of mepiquat chloride at 200 ppm produced lowest green fodder yield (22.1 t ha -1 ).Since mepiquat chloride is a growth retardant, it resulted in reduced plant height and dry matter production and finally reduction in fodder yield.NAA application significantly enhanced the fodder yield due to increased cell division, cell enlargement and elongation.Similar findings were also reported by Muthukumar et al. (2005), Rathika et al. (2009) and Mohamed et al. (2010).

Economics
On the basis of pooled data spacing 60 × 15 cm recorded, the significantly higher net returns (Rs33547 ha -1 ) and B: C (1.86) over spacing 90 × 10 cm.The pooled data show that application of 90 kg N ha -1 recorded the significantly higher net returns (Rs34895 ha -1 ) and B: C (1.87) over 60 kg N ha -1 .In case of plant growth regulators, the spray of NAA at 40 ppm gave significantly higher net returns over control and mepiquat chloride at 200 ppm in the pooled analysis.The pooled data indicate that spray of NAA recorded significantly highest net returns (Rs34975 ha -1 ) and B: C (1.95) over control and mepiquat chloride (Table 3 and Figures 4 to 5).

Conclusion
The results of the field experiment entitled "Performance of baby corn (Zea mays L.) as influenced by spacing, nitrogen fertilization levels and plant growth regulators" indicated that spacing of 60 × 15 cm with application of 90 kg N ha -1 and foliar spray of NAA at 40 ppm proved to be beneficial for obtaining higher yield of baby corn in agro-climatic zone IV-a.These practices may be passed on to the farmers for obtaining higher returns in this agroclimatic zone.Study is valuable for enhancing the profitability of rural as well as peri-urban farmers of collateral socio-agro-economic situations in developing world in a short time period.

Figure 1 .
Figure 1.Effects of spacing, nitrogen levels and PGR on green cob yield.

Figure 2 .
Figure 2. Effects of spacing, nitrogen levels and PGR on baby corn yield.

Figure 3 .
Figure 3. Effects of spacing, nitrogen levels and PGR on green fodder yield.

Figure 4 .
Figure 4. Effects of spacing, nitrogen levels and PGR on net returns.

Figure 5 .
Figure 5. Effects of spacing, nitrogen levels and PGR on benefits cost ratio.

Table 1 .
Effect of spacing, nitrogen levels and plant growth regulators (PGR) on yield attributes (Pooled data of 2 years).

Table 2 .
Effect of spacing, nitrogen levels and PGR on yield attributes (Pooled data of two years).

Table 3 .
Effect of spacing, nitrogen levels and PGR on green cob yield, baby corn yield and green fodder yield, net returns and benefit cost ratio B: C (Pooled data of 2 years).