​Morphophenological Characters and Productivity of Pigeon Pea [Cajanus cajan (L.) Millsp.] as Influenced by Crop Geometry and Plant Growth Regulators

Pigeonpea [Cajanus cajan (L.) Millsp.] is a versatile deep rooted legume crop, well known for its drought tolerance under Kharif rainfed upland ecosystem (Emefiene et al., 2013). It is an important protein rich annual pulse crop, grown throughout the tropical and sub-tropical regions of the world.
       
Choice of a suitable geometry for a particular genotype is one of the important factors among the different agronomic techniques in deciding the yield of pigeon pea. Adaptation of proper planting geometry to a particular genotype will go a long way in making efficient use of limited growth resources and to stabilize yield. Pigeonpea being highly branching and having indeterminate growth habit responds very well to crop geometry. Hence to achieve potential yields, it is important to maintain optimum plant population which can effectively utilize available moisture, nutrients and solar radiation.
       
Microclimate coupled with physiological process may include internal hormonal imbalance and may result in abscission of flowers and immature pods and drastic reduction in yield of pigeon pea. Plant growth regulators have the capacity to stimulate and inhibit physiological processes, which directly or indirectly might affect crop yield and quality. The plant growth regulators are also known to enhance the source sink relationship and stimulate the translocation of photo assimilates, thereby increase the productivity. Brassinosteroids (BRs) are a group of steroidal plant hormones that play pivotal roles in a wide range of developmental phenomenon in plants including cell division and cell elongation in stems and roots, photomorphogenesis, reproductive development, leaf senescence and stress responses (Clouse and Sasse 1998). There is limited information on the influence of plant growth regulators on growth, development and productivity of pigeon pea. 
       
Thus scientific manipulation by synchronizing plant growth through growth regulating chemicals in pigeonpea is needed, which can check the excessive vegetative growth, thereby creating proper balance between source and sink for enhanced crop yield and also to optimize the plant density to exploit yield potential. Keeping these views, the present investigation was carried out with an objectivesto enhance yield through proper planting geometry and foliar sprays of plant growth regulators, at experimental farm, Department of Agronomy, Vasantrao Naik Marathwada Krishi Vidyapeeth, Parbhani.

Present research experiment was conducted at research farm of Department of Agronomy, Vasantrao Naik Marathwada Krishi Vidyapeeth, Parbhani (MS) during kharif season of 2018 and 2019. The experiment was laid out in split plot design with the treatments consisted of twenty treatment combinations comprising four crop geometry in main plot and five foliar applications of plant growth regulators in sub plot and replicated thrice. The main plot treatments comprised of four crop geometries as 90 cm × 20 cm, 120 cm × 20 cm 60-120 cm × 20 cm and 75-150 cm × 20 cm whiles sub plot treatments were five treatments on  foliar application of plant growth regulators i.e. NAA @ 40 ppm, Mepiquat chloride @ 50 g a.i ha^-1, Brassinosteroids @ 0.1 ppm,  Chlormequat chloride @ 75 g a.i ha^-1 and control.
       
The onset of monsoon started from 23^rd standard meteorological week and with total rainfall of 781.4  mmduring first year while during second year (2019) the total quantity of rainfall received was 928.9 mm. During first and second year of experimentation sowing was accomplished on 26^th June 2018 and 28^th June 2019 respectively. Periodical observations on growth and yield contributing characters of pigeonpea along with the yield data were recorded and statistically analyzed to evaluate the effect of different treatments. Data on seed yield and straw yield were further subjected to calculations on harvest index, economic analysis and rain water use efficiency.

The data on morpho-phonologicalparameters viz. number of functional leaves plant^-1, leaf area, number of branches plant^-1 and dry matter accumulation plant^-1, along with the seed yield of pigeonpeaas influenced by crop geometry and foliar application of plant growth regulators during the course of investigation are critically interpreted and results are presented below.
 
Effect of crop geometry on growth, phenological parameters, yield and net returns of pigeonpea
 
Various crop geometries shown remarkable effect on growth of pigeonpea. The crop geometry of 60-120 cm × 20 cm and 90 cm × 20 cm recorded maximum plant height of pigeonpea as compared to other wider crop geometries (Table 1). While in case of all the other growth attributes viz. number of functional leaves plant^-1, leaf area andnumber of branches plant^-1 dry matter accumulation plant-1, crop geometry of 120 cm × 20 cm and 75-150 cm × 20 cm were found superior as compared to other. The crop geometry of 120 cm × 20 cm and 75-150 cm × 20 cm were at par with each other, this might be due to better availability of growth factors like moisture, space etc. for enhanced development of individual plant. Similar results were obtained by Waghmare et al., (2016). Maximum mean dry matter production plant^-1 of pigeonpea was recorded with crop geometry of 120 cm × 20 cm (S2), it was at par with crop geometry of 75-150 cm × 20 cm (S₄) and significantly superior over crop geometry of  90 cm × 20 cm (S1) and 60-120 × 20 cm (S₃). The increased dry matter accumulation plant^-1 of pigeonpea plants at wider spacing may be attributed to less competition between plants  and greater availability of growth resources for each plant which might have increased production and accumulation of photosynthates resulting in more dry matter accumulation. The above findings are in line with those reported by Pavan et al., (2011) and Sujatha et al., (2018). The mean duration for flower initiation and 50% flowering of pigeonpea was delayed during 2019 as compared to during 2018 (Table 2). The flower initiation and 50% flowering of pigeonpea were earlier in crop geometry 60-120 × 20 cm (S₃) and 90 cm × 20 cm (S₁) as compared to crop geometry of 120 cm × 20 cm (S₂). The data on mean chlorophyll content was not influenced significantly by different crop geometry during both the years of investigation.




       
Different crop geometries had significant influence on the seed yield of pigeonpea. The crop geometry 60-120 cm × 20 cm (S₃) produced significantly higher seed yield (1661, 1982 and 1821 kg ha^-1) as well as net returns over crop geometry of 120 cm × 20 cm (S₂) and crop geometry 75-150 cm × 20 cm (S₄), but  it was found at par with crop geometry 90 cm × 20 cm (S₁). The percent increase in seed yield of pigeonpea recorded with crop geometry 60-120 cm × 20 cm (S₃) over crop geometry of 120 cm × 20 cm (S₂) and crop geometry 75-150 cm × 20 cm (S₄) was 22.85 and 10.82 per cent, respectively on pooled basis. The probable reason behind this increase in the seed yield at closer crop geometry as compared to wider might be that, though the closer spacings showed lower values of attributes per plant like seed weight per plant, pods per plant as a result of intra row competition, the total yield was increased at closer spacing as the lower per plant yield was compensated by higher plant population per unit area. Also suitable planting geometry with crop geometry of 60-120 cm × 20 cm (S₃) helped in optimum and efficient utilization of the available resources and ultimately enhanced the yield.
 
Effect of foliar application of plant growth regulators on morpho-phenological parameters yield and net returns of pigeonpea
 
Foliar application of plant growth regulators showed a remarkable influence on various growth attributes of pigeonpea. (Table 1) Growth characters viz., plant height, number of functional leaves, leaf area, number of branches and dry matter accumulation plant^-1 were enhanced with the foliar application of Brassinosteroids @ 0.1 ppm  and application of NAA @ 40 ppm during both the years and was significantly higher than  control, foliar application of Mepiquat chloride @ 50 g a.i ha^-1 (G₂) and Chlormequat chloride @ 75 g a.i ha^-1 (G₄). Decrease in plant height of pigeonpea sprayed with Mepiqaut chloride might be due to the interference in gibberellic acid biosynthetic pathway as the reduced amount of gibberellins in the plant system affects the growth and decrease plant height. These results correlates with the findings of Kshirsagar et al., (2008) and Kashid et al., (2010) who reported decreac se in plant height with foliar application of mepiquat chloride and cycocel treated plants. Sumathi et al., (2016) also reported that, use of Giberellic acid (GA3) and Brassinosteroid (BR) significantly increased plant height in pigeonpea.
       
Among the plant growth regulators, foliar application of Brassinosteroids @ 0.1 ppm and foliar application of NAA @ 40 ppm recorded numerically higher values of chlorophyll content over other treatments. The data presented in Table 3 indicated that the foliar application of Brassinosteroids @ 0.1 ppm (G3) recorded higher seed yield as well net returns (Table 3) and was at par with foliar application of NAA @ 40 ppm (G₁) and significantly superior over other treatments, during both the years of experimentation and in pooled analysis. The magnitude of increase in seed yield recorded under the foliar application of Brassinosteroids @ 0.1 ppm (G₃) over foliar application of Mepiquat chloride @ 50 g a.i ha^-1 (G₂), Chlormequat chloride @ 75 g a.i ha^-1 (G₄) and control (G₅) on pooled basis was 20.75 per cent, 25.70 per cent and 36 per cent respectively. The maximum yield recorded by Brassinosteroids might be due to better vegetative growth, enhanced pod number, pod clusters, pod weight and seed yield per plant. These results are in line with findings reported by Kashyap et al., (2002), Ramesh and Ramprasad (2013),  Sumathi et al., (2016).


 
Interaction effect
 
It was observed that interaction between crop geometry 60-120 cm × 20 cm (S₃) with foliar application of Brassinosteroids @ 0.1 ppm (G3) recorded  higher seed yield (Table 4) and net returns, (Table 5) it was at par with interaction between crop geometry 60-120 cm × 20 cm (S₃) with foliar application of NAA @ 40 ppm (G₁) and interaction between crop geometry 90 cm × 20 cm (S₁) with foliar application of Brassinosteroids @ 0.1 ppm (G₃).

Based on the two years findings of present investigation, it can be concluded that, crop geometry of 60-120 cm × 20 cm and 90 cm × 20 cm for pigeonpea were found to be productive and remunerative, as compared to other crop geometries. While among the different plant growth regulators, foliar application of Brassinosteroids @ 0.1 ppm or foliar application of NAA @ 40 ppm (02 sprays at  bud initiation and flowering) was found to be beneficial in improving morpho-phenological pa rameters along with chlorophyll content, early flower initiation, seed yield and net returns of pigeonpea, as compared to other plant growth regulators.

None.