Production Potential of Pigeon Pea [Cajanus cajan (L.) Millsp.] as Influenced by Crop Geometry and Plant Growth Regulators

Seed yield is product of plant populations and the single plant yield. Maximum yield in a particular cultivars and environment can be obtained at the density where competition between the plants is low. This will be attained at an optimum plant density, which not only utilizes light, moisture and nutrients in more efficient way but also avoids excessive competition among the plants. The yield potential of pigeonpea can be realized through efficient utilization of solar radiation and mitigating terminal drought for which canopy size and shape play very important role.
       
Major physiological constraints limiting pigeonpea yield are flower and fruit drop. 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. Plant growth regulators are known to improve physiological efficiency including photosynthetic ability of plant and also enhance the source sink relationship and stimulate the translocation of photo assimilates, thereby increase the productivity. Several studies on different crops have shown that the exogenous application of GA₃, an important GAs can enhance the productivity of crops influencing the vital physiological processes (Bora and Sarma, 2006).
       
Apropose to the physio-morphological characteristics of pigeon pea, there is need for scientific manipulation by synchronizing plant growth through growth regulating chemicals, which can check the excessive vegetative growth, thereby creating proper balance between source and sink for enhanced crop yield and standardize the plant density to exploit yield potential. Considering these points the present investigation was carried out at Experimental Farm, Department of Agronomy, Vasantrao Naik Marathwada Krishi Vidyapeeth, Parbhani with objectives to stabilize yield through proper planting geometry and use of plant growth regulators.

The field experiments were conducted at Research Farm of Agronomy Department, Vasantrao Naik Marathwada Krishi Vidyapeeth and Parbhani (MS) during kharif season of 2018 and 2019. The soil of the experimental plot was clayey in texture and slightly alkaline in reaction having low in organic carbon, medium in available nitrogen and phosphorus, but marginally high in available potassium.
       
The experiment was laid out in split plot design and replicated thrice. Treatments consisted of twenty treatment combinations comprising four crop geometries as 90 cm × 20 cm, 120 cm × 20 cm 60-120 cm × 20 cm and 75-150 cm × 20 cm in main plot and 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 in sub plot.
       
The rainfall received was 781.4 mm and 928.9 mm during year 2018 and 2019 respectively, which was favorable for vegetative and reproductive growth of crop. Sowing was accomplished on 26^th June 2018 and 28^th June 2019 during first and second year respectively. Periodical observations on growth and yield of pigeonpea were recorded and statistically analyzed to evaluate the effect of different treatments.  The fertility co-efficient of pigeonpea was arrived from relationship between the number of flowers and the number of pods produced per plant and the results were expressed in terms of percentage (Sumathi et al., 2016).

The data related to yield attributes along with the seed, straw, biological yield, fertility coefficient and economic aspect of pigeonpea as influenced by crop geometry and foliar application of plant growth regulators are critically interpreted and results are presented below.
 
Yield attributes of pigeonpea as influenced by different treatments
 
Effect of crop geometry
 
Persual of data from Table 1 revealed that, crop geometry significantly influenced the yield attributes of pigeonpea. Number of pods plant^-1 were significantly highest under crop geometry of 120 cm × 20 cm (S₂) and was found at par with crop geometry of 75-150 cm ×  20 cm (S₄) followed by 60-120 cm × 20 cm (S₂) and significantly superior over crop geometry of 90 cm × 20 cm (S₁). Similar variation was observed in case of mean weight of pods plant^-1, number of pod clusters per plant, seed yield per plant. This might have resulted due to reduced competition for light, aeration, nutrients and moisture under wider spacing. Mula et al., (2010) also reported that individual plants of pigeonpea at wider spacing showed significant positive traits over closer spacing.
 

       
Seed index of pigeonpea i.e. 100 seed weight, number of pods cluster^-1, number of seeds pod^-1 and mean pod length of pigeonpea were not influenced significantly by different crop geometries, however crop geometry of 120 cm × 20 cm (S₂) and 75-150 cm × 20 cm (S₄) recorded numerically higher values. Favourable influence on physiological processes and build up of photosynthates due to adequate availability of moisture and nutrients throughout the growing season may be the reason behind this. Similar kinds of findings have been reported by Waghmare et al., (2016).
 
Effect of foliar application of plant growth regulators
 
Yield contributing parameters (Table 2) of pigeonpea were influenced due to foliar application of plant growth regulators. Foliar application of Brassinosteroids @ 0.1 ppm (G3) and foliar application of NAA @ 40 ppm (G₁) produced higher mean number of pods plant^-1, weight of pods (g), number of pod clusters plant^-1, seed yield plant^-1 (g) and was found significantly superior over rest of the treatments. Further foliar application of NAA @ 40 ppm (G₁) was followed by foliar application of Mepiquat chloride @ 50 g a.i ha^-1 during both the years. This may be attributed due to reason that, plant growth regulators in general, increase the number of flowers, also reduced flower and pod drop to some extent as reported by Ramesh and Thirumuguran (2001). The results are in line with the results reported by Reddy et al., (2004), Chandewar et al., (2016).
 
Interaction effect
 
It was observed that interaction between crop geometry 75-150 cm × 20 cm (S4) with foliar application of Brassinosteroids @ 0.1 ppm (G3) recorded higher seed yield plant^-1 (48.42 g),  it was at par with interaction between crop geometry 60-120 cm × 20 cm (S3) with foliar application of Brassinosteroids @ 0.1 ppm (G₃) and interaction between crop geometry 60-120 cm ´ 20 cm (S3) with foliar application of NAA @ 40 ppm (G₁) during the first year of experimentation (Table 4).
 
Yield studies
 
Data pertaining to seed yield, straw yield, biological yield and harvest index of pigeonpea during 2018 and 2019 as influenced by different crop geometry and foliar application of plant growth regulators are presented in Table 2.
 

 
Effect of crop geometry
 
Different crop geometries had significant influence on pigeonpea yield. The crop geometry 60-120 cm × 20 cm (S₃) produced significantly higher seed yield (1661, 1982 and 1821 kg ha^-1) 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 per cent increase in seed yield of pigeonpea recorded with crop geometry 60-120 cm × 20 cm (S₃) over 120 cm × 20 cm (S₂) was 22.85 per cent, on pooled basis. Similar kind of trend was observed for straw and biological yield as well as for harvest index of pigeonpea. The probable reason behind this might be that, though it showed lower seed weight per plant, pods per plant as a result of intra row competition, the total grain 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 60-120 cm × 20 cm (S₃) helped in optimum and efficient utilization of the available resources which ultimately enhanced the growth and yield. The higher seed and straw yield of pigeonpea ultimately resulted in higher biological yield with the crop geometry of 60-120 cm × 20 cm followed by crop geometry of 90 cm × 20 cm (S₁). These findings are in line with earlier findings of Saritha et al., (2012) and Nagaraj and Murali (2018).
       
The crop geometry 60-120 cm × 20 cm (S₃) recorded the highest harvest index (27.73 and 28.47) in pigeonpea, it was followed by crop geometry of 75-150 cm × 20 cm (S₄). This might be due to optimum utilization of resources which led to enhanced economic yield. These results correlate with the findings of Pramod et al., (2010) and Waghmare et al., (2016).
 
Effect of foliar application of plant growth regulators
 
The data presented in Table 2 indicated that the foliar application of Brassinosteroids @ 0.1 ppm (G₃) recorded higher seed yield, it 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 Brassinosteroids @ 0.1 ppm (G₃) over control (G₅) on pooled basis was 36 percent. The maximum grain yield recorded by Brassinosteroids might be due to better growth, enhanced pod number, pod clusters, pod weight and seed yield per plant. These results also correlate with findings reported by Ramesh and Ramprasad (2013), Sumathi et al., (2016).
       
The straw yield and biological yield (Table 2) was influenced significantly due to plant growth regulator treatments during both the years. It was observed that, during both the years of study and in pooled analysis foliar application of NAA @ 40 ppm (G₁) and the foliar application of Brassinosteroids @ 0.1 ppm (G₃) recorded higher straw yield ha^-1 and were significantly superior over other treatments. The increase in straw yield of pigeonpea with foliar application of Brassinosteroids and foliar application of NAA was mainly attributed to enhanced growth and yield which ultimately led to increase in dry matter. These results are parallel with the findings of Upadhyay (2002). It was observed from Table 2 that the foliar application of   Brassinosteroids @ 0.1 ppm (G₃) and Mepiquat chloride @ 50 g a.i ha^-1 recorded higher values of harvest index in pigeonpea. While during second year of investigation application of Chlormequat Chloride @ 75 g a.i ha^-1(G₄) recorded higher values of harvest index. This increased harvest index might be due to the reduction in excess vegetative growth along with increased mobilization of metabolites from source to reproductive sink and conservation of biomass into yield. These findings are in line with the findings of Kalyankar et al., (2008).
 
Economics and fertility co-efficient studies
 
Data on the economics pertaining to the gross monetary returns, net monetary returns, benefit cost ratio (B:C ratio) and fertility co-efficient of pigeonpea under various treatments are furnished in Table 3.
 

 
Effect of crop geometry
 
The data regarding economic returns of pigeonpea as influenced by treatments indicated that, crop geometry of 60-120 cm × 20 cm (S₃) recorded the highest gross monetary returns (₹94003, ₹122570 and ₹108280 ha^-1), net monetary returns (₹58502, ₹85641, ₹72072) and benefit cost ratio (2.64, 3.31 and 2.97) during 2018, 2019 and pooled means respectively, while it  was at par with the crop geometry of 90 cm × 20 cm (S₁) and significantly superior over rest of the crop geometry. This higher gross and net returns with the closer crop geometry may be due to the increased yield per unit area along with the optimum and efficient utilization of the available resources. This ultimately reflected in enhanced gross and net returns. These results co insides with the findings reported by Bhavi et al., (2013) and Kittur and Guggari (2017). Among the different crop geometry, highest fertility co-efficient of pigeonpea was recorded with crop geometry of 120 cm × 20 cm (S₂), it was at par with the crop geometry of 75-150 cm × 20 cm (S₄) and crop geometry of 60-120 cm × 20 cm (S₃) during first year of study while during second year the differences in fertility co-efficient of pigeonpea were found nonsignificant among the crop geometry.
 
Effect of foliar application of plant growth regulators
 
During both the years of study as well as in pooled results, foliar application of Brassinosteroids @ 0.1 ppm (G₃) recorded higher gross and net monetary returns in pigeonpea, it was followed by foliar application of  NAA @ 40 ppm and both of these treatments were significantly superior over rest of the treatments. Similar trend was recorded for benefit : cost ratio during 2018, 2019 and pooled results (Table 3). The higher net returns and benefit: cost ratio was on account of the higher seed yield recorded with application of Brassinosteroids @ 0.1 ppm (G₃). These findings are in close conformity with those reported by Kashid et al., (2010) and Jadhav et al., 2017.
       
It was observed that, among the different plant growth regulator treatments, foliar application of  Brassinosteroids @ 0.1 ppm (G₃) recorded the highest fertility co-efficient of pigeonpea, over other treatments (Table 2) and was followed by foliar application of  NAA @ 40 ppm (G₁). This might be attributed to the reason that, these plant growth regulators increases the source activity during pod filling stage and thus diverts the assimilates for pod (sink) development. The present results correlate to the findings reported by Sumathi et al., (2016).
 
Interaction effect
 
The interaction effect between treatments on seed, straw, biological yield, gross monetary returns and net monetary returns of pigeonpea was found to be significant during both the years as well as pooled data. It was observed from the data (Table 4 and 5) that maximum seed, straw and biological yield, gross monetary  returns and net monetary returns were recorded with the interaction between crop geometry 60-120 cm × 20 cm (S₃) with foliar application of Brassinosteroids @ 0.1 ppm (G₃), it was at par with interaction between crop geometry 60-120 cm × 20 cm (S3) with foliar application of NAA @ 40 ppm (G₁), interaction between crop geometry 90 cm × 20 cm (S₁) with foliar application of Brassinosteroids @ 0.1 ppm (G₃) and interaction between crop geometry 90 cm × 20 cm (S₁) with foliar application of NAA @ 40 ppm (G₁).
 

 

Based on the two years findings and pooled results of present investigation, it can be concluded that, crop geometry of 60-120 cm × 20 cm or 90 cm × 20 cm for pigeonpea along with foliar application of Brassinosteroids @ 0.1 ppm, as well as the crop geometry of 60-120 cm × 20 cm along with foliar application of NAA @ 40 ppm  were found to be beneficial in improving seed yield, net returns and also fertility co-efficient of pigeonpea.