Productivity and Morpho-phenological Characters of Pigeonpea [Cajanus cajan (L.) Millsp.] as Influenced by Crop Geometry and Nipping Practice

Pigeonpea [Cajanus cajan (L.) Millsp.] is an important protein-rich annual pulse crop, grown throughout the tropical and sub-tropical regions of the world. It is a deep-rooted legume crop, well known for its drought tolerance under Kharif rainfed upland ecosystem (Emefiene et al., 2013). Among the different crop management techniques, suitable crop geometry for a particular genotype is one of the major factors to decide the optimum population which leads to the final yield of pigeonpea. The architecture of pigeonpea genotypes varies widely.
       
In pigeon pea, the vegetative and reproductive stages occur concurrently; as a result, the vegetative and reproductive sinks are always competing for available assimilates. PGRs have thus been characterized as the agriculturist’s most effective component for increasing crop yields. Plant hormones are compounds that, when given in minute quantities stimulate or restrict natural plant development (Kumar, 2001). It improves photo- assimilation and the source-sink relationship and thus increases the photosynthetic capacity of the plant, which is helpful in increasing productivity and thus leads to higher crop yield (Amanullah et al., 2010). The foliar application of nutrients at critical stages of crop growth is the most appropriate and accurate method of correcting nutrient deficiencies and helps to achieve maximum potential yield of the crop and ultimately sufficient plant nutrition is absolutely essential for improving productivity (Thakur et al., 2017). 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 pigeonpea. 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.

Field research experiments were conducted at farm of Department of Pulses, Tamil Nadu Agricultural University, Coimbatore during kharif season of 2021 and 2022. The experiment was laid out in split plot design with three replications. Treatments consisted of sixteen combinations comprising four crop geometry in main plot and nipping methods in sub plot. Crop geometry adopted in main plot were 120 cm × 45 cm, 120 cm × 30 cm, 90 cm × 45 cm and 90 cm × 30 cm whiles sub plot treatments were mechanical nipping, foliar application of mepiquat chloride @ 500 ppm, Chlormequate chloride @ 500 ppm and control (No nipping). Periodical observations on growth and yield contributing characters of pigeonpea along with the yield data were recorded during harvesting stage by following Sadasivam and Manickam (1996). The data collected for the various study parameters were statistically analysed using the analysis of variance (ANOVA) method for split-plot design. The 5% least significant difference was used to calculate the significance of the treatments (Gomez and Gomez, 1984). Data on seed yield and straw yield were further subjected to calculations on harvest index and economic analysis.

The data on morpho-phonological parameters viz. number of functional leaves per plant, leaf area, number of branches per plant and dry matter accumulation per plant, along with the seed yield of pigeonpea as influenced by crop geometry and nipping practice during the course of investigation are critically analysed 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 90 cm × 45 cm and 90 cm × 30 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 per plant, leaf area and number of branches per plant, dry matter accumulation per plant, crop geometry of 120 cm × 45 cm and 120 cm × 30 cm were found superior as compared to other. The crop geometry of 120 cm × 45 cm and 120 cm × 30 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 per plant of pigeonpea was recorded with crop geometry of 120 cm × 45 cm , it was at par with crop geometry of 120 cm × 30 cm  and significantly superior over crop geometry of 90 cm × 45 cm and 90 cm × 30 cm. The increased dry matter accumulation per plant 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 2022 as compared to during 2021 (Table 2). The flower initiation and 50% flowering of pigeonpea were earlier in crop geometry 90 cm × 30 cm and 90 cm × 45 cm  as compared to crop geometry of 120 cm × 30 cm  and 120 × 45cm.
 

 

      
Different crop geometries had significant influence on the seed yield of pigeonpea. The crop geometry 120 cm × 45 cm produced significantly higher seed yield (1231 kg ha^-1) as well as net returns over crop geometry of 90 cm × 30 cm  and 90 cm × 45 cm, but it was found at par with crop geometry 120 cm × 30 cm. The percent increase in seed yield of pigeonpea recorded with crop geometry 120 cm × 45 cm (M4) over crop geometry of 90 cm × 45 cm (M2) and 90 × 30 (M1) was 19 and 26 per cent, respectively on pooled basis. The probable reason behind this increase in the seed yield at wider crop geometry as compared to closermight be that, the wider spacing showed higher values of attributes per plant like seed weight per plant, pods per plant and higher per plant yield. At wider spacing, reduction of plant population per unit area was compensated by higher per plant yield.Also planting with crop geometry of 120 cm × 30 cm (M3) helped in optimum and efficient utilization of the available resources and ultimately enhanced the yield.

Effect of nipping practice on morpho-phenological parameters yield and net returns of pigeonpea
 
Different nipping practices showed a remarkable influence on various growth attributes of pigeonpea (Table 1). Growth characters viz., number of functional leaves, leaf area and dry matter accumulation per plant were enhanced with the foliar application of chlormequat chloride @ 500 ppm and application of mepiquat chloride @ 500 ppm during both the years and was significantly higher than control (No nipping) and mechanical nipping practice. 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 decrease in plant height with foliar application of mepiquat chloride and cycocel treated plants. Among the nipping practices, chemical nipping with foliar application of chlormequat chloride @ 500 ppm and foliar application of mepiqaut chloride@ 500 ppm recorded numerically higher values of chlorophyll content over other treatments. The data presented in Table 3 indicated that the foliar application of chlormequat chloride @ 500 ppm recorded higher seed yield as well net returns (Table 3) and was at par with foliar application of mepiquat chloride @ 500 ppm 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 chlormequat chloride @ 500 ppm (S3) over mechanical nipping and control (S1) on pooled basis was 21 per cent and 12.9 per cent respectively. The maximum yield recorded by chlormequat chloride might be due to better vegetative growth, enhanced pod number, pod weight and seed yield per plant. These results are in line with findings reported by Kashyap et al., (2002), Ramesh and Ramprasad (2013) and Sumathi et al., (2016).
 

 
Interaction effect
 
It was observed that interaction between crop geometry 120 cm × 45 cm (M4) with foliar application of chlormequat chloride @ 500 ppm (S3) recorded higher seed yield and net returns, (Table 4) it was at par with interaction between
crop geometry 120 cm × 45 cm (M4) with foliar application of mepiquat chloride @ 500 ppm (S2).
 

Based on the two years findings of present investigation, it can be concluded that, crop geometry of 120 cm x 45 cm for pigeonpea was found to be productive and remunerative, as compared to other crop geometries. While among the different nipping practices, chemical nipping with foliar application of chlormepiquate chloride@ 500 ppm (01 spray at bud initiation stage) was found to be beneficial in improving morpho-phenological parameters along with chlorophyll content, early flower initiation, seed yield and net returns of pigeonpea, as compared to other nipping practices.

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