Growth attributes
The plant height was significantly higher in high density planting in 30×30 cm spacing at 90 days after sowing and it was on par with high density planting in 30×30 cm spacing + 1% PPFM spray (Table 1). The higher plant height may be because of competition for light, water and space which resulted in increased plant height of crops in closer spacing as compared to wider spacing
(Rasul et al., 2012). Modification of canopy architecture by nipping reduced the plant height and increased the number of lateral branches as compared to control. Sowing in 60×30 cm spacing + nipping at 45 days after receipt of soaking rain +1% PPFM spray recorded significant reduction in plant height and it was on par sowing in 60×30 cm spacing + nipping at 45 days after receipt of soaking rain, sowing in 60×30 cm spacing + nipping at 60 days after receipt of soaking rain +1% PPFM spray and sowing in 60×30 cm spacing + nipping at 60 days after receipt of soaking rain, respectively. Nipping the apical bud induced more lateral branches instead of plant hight. Similar findings were also reported by
Bhavana et al., (2019).
Crop geometry had a significant influence on the number of days to 50% flowering of redgram. Significantly lesser number of days to 50% flowering (80 days) was recorded in high density planting in 30×30 cm spacing and this was on par with high density planting in 30×30 cm spacing + 1% PPFM spray (81 days). The competition for growth resources in high density planting quickens the maturity process. Thus earlier flowering was reported in closer spacing. These findings are in conformity with the observations of
Manjesh et al., (2019) and
Deka et al., (2015). Similarly higher number of days to 50% flowering was recorded in no nipping treatments as compared to nipping treatments (Table1). The nipping reduced apical dominance and induced the reproductive growth. No nipping delayed the leaf senescence and increased the duration of vegetative growth delaying the flowering
(Khan et al., 2018).
The crop growth rate (CGR) is an important parameter used to estimate the production efficiency. The maximum increases in CGR was recorded between 60-90 days after receipt of soaking rain in all the treatments and declined thereafter towards maturity (Table 1). Among the different treatments high density planting in 30×30 cm spacing recorded significantly higher the crop growth rate and it was at par with high density planting in 30×30 cm spacing + 1% PPFM spray. This may be attributed to higher plant population per unit area in this treatment as also reported by
Rajeshkumar et al., (2017). Likewise nipping treatments recorded maximum crop growth rate as compared to non nipping treatments. This might be due to increased accumulation of dry matter owing to enhanced production of more lateral branches (
Kithan and Singh, 2017).
Relative water content (RWC) and proline content
RWC and proline accumulations are the measures to identify tissue water status. At harvest significantly higher RWC of 51.6% was recorded in sowing at 60 × 30 cm spacing + nipping at 45 days after receipt of soaking rain. Lowest relative water content of 44.5% was recorded in control (Fig 1). Under rainfed ecosystem relative water content for all plant densities was primarily a function of rainfall events and depends on amount of rainfall received
(Suresh et al., 2013). The well distributed rainfall and optimum plant population throughout the cropping period led to efficient utilization of rain water and available soil moisture resulting in higher RWC in recommended spacing. Broadcasting resulted in lower RWC might be due to uneven plant population and reduced efficiently in using the soil moisture by the crop. High density planting results in increased competition for available soil moisture whereas in normal spacing no such competition occurs.
Through biochemical process plants synthesize osmolytes such as proline which is an indicator of drought tolerance capacity of the plants. Proline accumulation helps in maintaining the osmotic balance in plant cells suffering from water deficiency
(Pandian et al., 2017). In the present investigation the proline content ranged from 31.52 mg g
-1 .
to 26.61mg g-1 (Fig 1). Broadcasting resulted in higher proline content followed by high density planting and normal recommended spacing. Closer spacing recorded more proline content as compared to normal recommended spacing, as also observed by
Singh et al., (2015). Among the different treatments, broadcasting recorded the maximum accumulation of proline and it was associated with lower level of RWC of the crop (Fig 1). Similar findings have also been observed by
Shinde et al., (2018).
Seed yield, stalk yield and harvest index
The data on seed yield, stalk yield and harvest index are presented in (Table 2). Modified canopy architecture in treatment of sowing in 60×30 cm spacing + nipping at 45 days after receipt of soaking rain resulted in significantly higher grain yield and it was on par with sowing in 60×30 cm + nipping at 45 days after receipt of soaking rain +1% PPFM spray. The yield increase was 72% over control (Farmer practice). Nipping arrests the apical bud dominance and increases the production of side branches thus increase the canopy size, photosynthetic activity and more flower buds per plant leading to enhanced the seed yield. These results are in agreement with the findings of
Dhaka et al., (2020) and
Lakshmi et al., (2015). Significantly higher stalk yield was recorded with high density planting in 30×30 cm spacing and it was at par with high density planting in 30×30 cm spacing + 1% PPFM spray. High density planting recorded higher stalk yield as compared to other treatments, this is may due to higher plant population per unit area. Similar findings were also reported by
Sathyamoorthi et al., (2008). Harvesting index represents increased physiological capacity to mobilize photosynthates and translocate to the economical part. Harvest index did not show any significant difference among the treatments. However the maximum harvest index was recorded in sowing in 60×30 cm spacing + nipping at 45 days after receipt of soaking rain followed by sowing in 60×30 cm spacing + nipping at 45 days after receipt of soaking rain +1% PPFM spray. Modified canopy architecture by nipping increased the number of branches used for increasing the source – sink relationship and number of pods per plant leading to higher harvest index
(Khan et al., 2018).
RWUE and per day productivity
Among the different treatments higher RWUE was recorded with sowing in 60×30 cm spacing + nipping at 45 days after receipt of soaking rain followed by sowing in 60×30 cm spacing + nipping at 45 days after receipt of soaking rain +1% PPFM spray to the tune of 72.6% and 65.4% increase in rain water use efficiency over control, respectively (Table 3). Similarly higher per day productivity were also observed in the above treatments.This may be attributed to well distributed rainfall during crop growth period, adequate availability of soil moisture leading to increased rain water use efficiency and per day productivity of redgram under rainfed condition. As the rainfall was well distributed and the crop did not suffer any moisture stress during the crop growth period, there was no effect of 1% PPFM application to mitigate the moisture stress effect to the crop.
Protein content and protein yield
The seed protein content did not show any significant difference due to crop geometry, modification of canopy architecture and 1% PPFM application treatments. However, higher the protein content was recorded in sowing in 60×30 cm spacing + nipping at 60 days after receipt of soaking rain followed by sowing in 60×30 cm spacing + 1% PPFM spray (Table 4). Protein content of the seed is mainly influenced by the environmental factors and the dose of fertilizer application
(Saxena et al., 2010). However, the protein yield of redgram was significantly influenced by the different treatments. Significantly higher protein yield was recorded with sowing in 60×30 cm spacing + nipping at 45 days after receipt of soaking rain which was on par with sowing in 60×30 cm + nipping at 45 days after receipt of soaking rain +1% PPFM spray. Increased seed yield and protein yield was noted in nipping at 45th days of the crop (Table 4). Increased canopy size by producing more number of productive branches led to more assimilation of photosynthates and increased seed yield and protein yield as compared to control. Similar findings were also reported by
Dhaka et al., (2020).
Economics
Maintaining optimum plant population at 60 × 30 cm spacing + nipping at 45 days after receipt of soaking rain recorded maximum gross monetary return, net monetary return and benefit cost ratio (Fig 2). This was due to effective utilization of resources resulting in higher yield attributes which increases the yield and economics. Similar results were also obtained by
Sharma et al., (2010) and
Srinivasan et al., (2019).
Based on the findings of the present investigation it may be concluded that modification of canopy architecture by nipping at 45
th day in the crop sown in 60 × 30 cm spacing results in higher level of relative water content, maximum seed yield and protein yield of redgram under rainfed condition.
