Effect of Improved Agronomic Approaches on Growth and Yield of Redgram [Cajanus cajan (L.) Millsp.] under Rainfed Ecosystem

Rainfed agriculture plays a major role in Indian economy, food and livelihood security. The net sown area in India is 141.40 M ha out of which 73.20 M ha (52%) is under rainfed condition and contribute to 40% of the food grain production, 2/3^rd of livestock population and 80% of the total pulse production.
 
Pulses are the important group of food crops considered as a protein source for both human as well as animal nutrition (Bhatt and Karim, 2009) and it play a vital role in national food and nutritional security. Globally, India is the largest producer and consumer of pulses accounting for about 25% of production, 27% of consumption and 34% of food use (Pooniya et al., 2015). India’s population will be expected to touch 1.68 billion by 2030 and the pulses requirement will be 32 million tones with the required annual growth rate of 4.2% (Sarkar et al., 2018).
 
In India redgram [Cajanus cajan (L.) Millsp.] is commonly known as Tur or Arhar and it is the second most important pulse crop in the country next to chickpea. Redgram is considered as an important food legume which contains 20-22 % protein. So, it is a principle crop in South India to meet out the protein requirement of vegetarian people and hence referred as ‘poor man’s meat’. Redgram can fix around 40 kg ha^-1 N (Domoguen et al., 2010). The deep root system of redgram breaks the hard pan of the soil hence it is known as “biological plough”. Redgram have the ability to withstand the extreme drought condition and is an important rainfed pulse crop in South India.  Though India contributes more than 90% of world’s redgram cultivation area and production, India imports around 3.09 million tones of redgram and it contributes 6.60% share in India’s import basket during 2018 (Sarkar et al., 2018). This is mainly because of low productivity of redgram in India.
 
 Redgram largely cultivated in rainfed condition and farmers employ to faulty agro techniques is a reason for low productivity in India. Timely sowing of crops, optimum plant population and suitable agronomic practices are the main key factors to determine the crop growth and enhance the yield of rainfed crop. Rainfall is the prime source for water resource in rainfed farming. Sowing immediately after the receipt of rainfall leads to difficulties in sowing operation and reduce the availability of soil moisture during crop growth period. To avoid these difficulties pre monsoon sowing technique is adopted for rainfed farming to enhance better crop growth and yield.
 
Plant population plays a major role in determining dry matter production and yield of the crop. Nipping is an important agronomic approach to arrest the apical bud dominance and enhance the lateral growth which will ultimately increase the number of productive branches and ultimately yield (Reddy and Narayanan, 1987). However while practicing nipping; the time of nipping should be optimized to enhance the yield. Application of 1% Pink Pigmented Facultative Methylotroph (PPFM) increases the drought tolerance in plants and its application helps to mitigate drought occurring during crop growth period and also increase the crop yield. From the last 3 years the redgram production is declined in India due to occurrence of drought (Fig 1). The yield of rainfed redgram can be increased through improved agronomic management practices.


 
Considering all these factors above, the main objective of this investigation is to study the impact of improved agronomic approaches to increase the productivity of redgram under rainfed condition.

Experimental site and soil analysis
 
Field experiment was designed at Department of Agronomy, Agricultural College and Research Institute, Tamil Nadu Agricultural University – Madurai and was carried out in a progressive farmer’s field in Vadippatti Taluk of Madurai district, Tamil Nadu, India. The experiment was conducted during North East Monsoon season of 2019 to study the effect of improved agronomic manipulations on growth and yield of redgram under rainfed ecosystem. The experimental field was geographically situated between 10^o.10' N latitude and 77^o.99' E longitude with an altitude of 144 meters above the mean sea level, which will comes under the southern agro climatic zone of Tamil Nadu. The soil was sandy loam in nature with pH of 7.85.  The initial soil available N, P and K were 324, 16 and 295 kg ha^-1 respectively. The organic carbon content of the soil was 0.52%.
 
Experiment details
 
The experiment was laid out in Randomized Block design with three replications. The gross plot size of the experimental site was 24 m² (4 m X 6 m).The treatments comprised of Control (Farmer practice - T₁), Sowing at 60 cm × 30 cm (recommended spacing - T₂ ), High Density Planting at 30cm × 30 cm (T₃), Sowing at 60 cm x 30 cm + Nipping at 45 Days after receipt of soaking rain (T4), Sowing at 60 × 30 cm + Nipping at 60 Days after receipt of soaking rain (T₅), Sowing at 60 × 30 cm  + 1% PPFM spray (T₆), High Density Planting at 30 × 30 cm + 1% PPFM spray (T₇), Sowing at 60 × 30 cm + Nipping at 45 Days after receipt of soaking rain +1% PPFM spray (T₈), Sowing at 60 × 30 cm + Nipping at 60 Days after receipt of soaking rain +1% PPFM spray (T₉).
 
Agronomic practices
 
The test crop is redgram [Cajanus cajan (L.) Millsp.], a food legume. The variety used for the experimentation is Co (RG) 7. The ideal pre monsoon sowing period for the region is 35th standard week, hence the pre monsoon sowing was carried out on 31.08.2019 for all the treatments (T₁-T₉) and the crop was raised fully under rainfed condition. In sowing, broadcast was done for control (Farmer practice - T₁) and dibbling was done for remaining all other treatments (T₂-T₉). In broadcast seeds were sown randomly and in dibbling the seeds were inserted into the soil. The recommended doses of fertilizers for rainfed condition (12.5:25:12.5 kg NPK ha^-1) were applied in the form of urea, SSP, Muriate of potash. The entire doses of fertilizers were applied basally at the time of sowing the crop. As per TNAU Crop Production Guide 2019 all the recommended agronomic practices were followed to successfully cultivate the crop.  Nipping was done manually on 45 and 60 days after receipt of soaking rain for the respective treatment plots. Foliar application of 1% PPFM was carried out at 50 percent flowering of crop which occurs on 85 days after receipt of soaking rain in respective treatments plots.
 
Biometrics observation and Statistical analysis
 
The crop was raised under rainfed condition, all growth and yield parameters were recorded. The crop was harvested at its full maturity stage. The seed yield and yield attributing parameters were recorded and the economics were workout. The data on different parameters were analyzed statistically by adopting Fisher’s method of ANOVA suggested by Gomez and Gomez (1984).
 
Rainfall distribution
 
The first soaking rain (15.6 mm) was received on 10.09.2019. The rainfall received during the cropping period was 521.7 mm in 31 rainy days and is presented in Fig 2. The rainfall is well distributed and the crop did not suffer any moisture stress during its entire growing period. 


 

Growth parameters
 
The data on plant growth parameters such as plant height, Leaf Area Index (LAI) and Dry Matter Production (DMP) at harvest are presented in Table 1. The results showed that significant differences were recorded in plant growth parameters due to improved agronomic manipulations on redgram grown under rainfed condition. In the present investigation significantly higher the plant height (193.5cm) was recorded in T₃ at harvest and on par with T₇ (192.7cm). Increased plant height was noticed in high density planting due to competition between the plants for sunlight, water and space. This similar kind of results was also observed by Nagarjun et al., (1980), Rasul et al., (2012) and Manjesh et al., (2019). Among the nipping treatments, T₈ recorded the significant reduction in plant height (155.6 cm) which was on par with the treatments of T₄ (157.1 cm), T₉ (160.0 cm) and T₅ (161.2 cm) respectively. Nipping of primary branches resulted reduced plant height and increased number of secondary branches compare to no nipping. This was in line with Dhaka et al., (2020).


 
The agronomic manipulations alter the plant physiology attributes such as LAI and DMP (Table 1). Significantly higher the Leaf Area Index (5.17) at 50% flowering of the crop was recorded in T₃ which was found at par with T₇ (5.02). This can be attributed to the increased plant population. Treatments involving nipping of primary branches at 45 and 60 days significantly higher LAI (3.73) was recorded in T4 which was found at par with T₈ (3.71),T₉ (3.54) and T₅ (3.50) compared to other treatments (T₁, T₂ and T₆).  Nipping induced the lateral growth with more number of branches and subsequently recorded increased LAI values. Similar findings were reported by Sarkar and Paul (2005) in sesame and Jaidka et al., (2020) in soybean. Significantly higher dry matter production (5057 kg ha^-1) was recorded in T₃ on par with T₇ (4997 kg ha^-1) at harvesting stage due to higher plant populations compared to other treatments (Table 1). This result is accordance with the earlier findings of Sathyamoorthi et al., (2008) in greengram.
 
Yield parameters
 
The yield parameters (Total number of productive branches plant^-1, number of pods plant^-1, pod length (cm), number of seeds pod^-1, 100 seed weight (g) and seed yield) were recorded and presented in Table 2. The recorded experimental results showed nipping significantly increases the number of productive branches, number of pods plant^-1 and the seed yield over control. Among the nipping treatments, T₄ recorded significantly higher number of productive branches (16.8) which was found to be at par with T₈ (16.4). This was followed by nipping at 60 days (14.6 for T₅ and 14.3 for T₉). Lowest number of productive branches was observed in T₃ (8.4) on par with T₇ (8.7) and followed by the farmer’s conventional practice of broadcasting of seeds (Table 2). At closer spacing the plants adopt for self thinning of branches and enhance the vertical growth rather than horizontal growth. This may be attributed for the increased plant height and reduced total number of productive branches in high density planting. These results are in agreement with Joshi et al., (2019), Rajeshkumar et al., (2017), Murad et al., (2014), Kumar and Badiyala (2005).


 
Treatments with nipping of primary branches at 45 days, T₄ was recorded significantly higher number of pods plant^-1 (234.6) which was on par with T₈ (231.4). Early Nipping at 45 days increased the number of productive branches and subsequently contributed for the increased number of pods per plant and the seed yield. This was in line with Dhaka et al., (2020). The other yield parameters such as number of seeds pod^-1, 100 seed weight (g), pod length (cm) are genetic characters of the variety and are not significantly influenced by the agronomic manipulations (Table 2).
 
Yield
 
The seed yield of redgram was significantly influenced by the various agronomic manipulations. Sowing at 60 x 30 cm + Nipping at 45 Days after receipt of soaking rain (T₄) was resulted in significantly higher the seed yield of 1512 kg ha^-1 and it is on par with Sowing at 60 x 30 cm + Nipping at 45 Days after receipt of soaking rain + 1% PPFM spray (T₈) which recorded a seed yield of 1451 kg ha^-1 (Table 2). The yield increase was 72 per cent over farmer’s practice (T₁) (878 kg ha^-1). Nipping of primary branch will arrest the apical bud dominance and will induce more number of secondary branches, growth increases the accumulation of photosynthates which will ultimately increase the seed yield. Similar findings were reported by Lakshmi et al., (2015) and Sharma et al., (2003). 
 
High density planting at 30 cm × 30 cm (T₃) recorded a seed yield of 1253 kg ha^-1 which is 42.7 per cent and 13.5 per cent over farmer’s practice (T₁) (878 kg ha^-1) and with recommended spacing (T₂) (1103 kg ha^-1) respectively.  Even though the number of branches plant^-1 and number of pods plant^-1 were lower in high density planting compared with other treatments, it was compensated with the increased plant population. The rainfall received during the cropping period was 521.7 mm in 31 rainy days. The rainfall is well distributed and the crop did not suffer any moisture stress during its entire growing period.  Hence the effect of PPFM in mitigating the drought could not be capitalized in this experiment. 
 
Economics
 
Among the agronomic manipulations sowing at 60 cm × 30 cm + nipping at 45 days (T₄) recorded highest gross return of Rs. 87,710 ha^-1, net return of Rs. 54,629 ha^-1 with a benefit cost ratio of 2.65 (Table 3). 

From the experimental results it can be concluded that sowing at 60 cm × 30 cm + nipping at 45 days after the receipt of soaking rain (T₄) recorded the maximum seed yield and higher benefit cost ratio in redgram raised under rainfed condition.