Response of Super Early Varieties of Pigeonpea to Crop Geometry under Rainfed Conditions

Sri Potti Sriramulu Nellore district of Andhra Pradesh is mainly influenced by north-east monsoon and rabi is the main cropping season. A late or advancement of north east monsoon, prolonged breaks and early cessation of monsoon may have devastating effects on agriculture in rainfed areas of Sri Potti Sriramulu Nellore district, even if the mean annual rainfall is normal. However, this early cessation of rainfall, leads to terminal moisture stress in long duration crops like pigeonpea [Cajanus cajan (L.) Millsp.] at critical stages, which resulted in the lower productivity of pigeonpea.

Pigeonpea   is the second most important pulse crop of India after chickpea. In India, it is grown over an area of 48.24 lakh hectares with a production of 38.8 lakh tones and the productivity is 804 kg ha^-1. During the period, traditional long-duration types (more than 180 days) have been continually replaced by short (120-140 days) and medium duration (160-180 days) varieties to escape terminal moisture stress in the changing climate scenario. Due to ever increasing pressure on land there is need for intensification of cropping systems in a sustainable way. The indirect impact of these improved super early varieties (85-100 days) has been on the enhancement of overall cropping intensity.   

The medium and long duration varieties of pigeonpea have long vegetative growth phase (120-160 days) mainly attributed to slow initial growth (Saxena, 2008). This leads to poor productivity and less efficient utilization of land and other resources. In this context, there is a need for photo insensitive super early varieties of pigeonpea which are ideal for sowing round the year and to escape terminal moisture stress even under changing climatic situations.

Choice of a suitable geometry for a particular genotype is one of the important factors among the different agronomic practices limiting the yield of pigeonpea. Adaptation of proper planting geometry to a particular genotype will go a long way in making efficient use of limited growth resources and thus to stabilize yield. Super early varieties of pigeonpea having determinate and indeterminate growth habits respond very well to crop geometry. Keeping this in view we prosed to study the performance of different pigeonpea varieties and to find out optimum spacing for these varieties for rabi season under rainfed conditions of coastal region. 

Experimental site and soil information
 
The experiment was conducted during rabi, 2018-19 and 2019-20 at Agricultural Research Station, Podalakur (14°22'N latitude, 79°44'E longitude and 43m above mean sea-level), Sri Potti Sriramulu Nellore district Andhra Pradesh. The climatic condition of Sothern zone is sub-tropical influenced by north-east monsoon. The soils are clay loam in texture, porous and grayish black having pH of 8.48, EC of 0.229 dSm^-1, organic carbon 0.3%, available nitrogen 201 kg ha^-1, available phosphorus 46 kg ha^-1 and available potassium 225 kg ha^-1.
 
Experimental design and treatment combination
 
The present field experiment was laid out in a split plot design with 4 varieties of pigeonpea (V₁: ICPL 20338 (days to maturity 85 days, determinate growth); V₂: ICPL 20325 (days to maturity 97 days, indeterminate growth); V₃: ICPL 11255 (days to maturity 85 days, determinate growth) ; V₄: LRG 52 (days to maturity 150 days, indeterminate growth)as main plot treatments and 3 crop geometries S1: 30 cm x 15 cm; S₂: (45 cm x 15 cm); S₃: (60 cm x 15 cm) as sub plot treatments in three replications.
 
Crop management
 
Sowings were performed on 06-10-2018 and 09-10-2019 during 2018-19 and 2019-20, respectively. The recommended dose of fertilizer @ 20 kg N and 50 kg P₂O₅ per hectare were applied as basal at the time of sowing uniformly in all the treatments. Nitrogen and phosphorus were applied in the form of Urea and Single Super Phosphate, respectively.  The total rainfall of 290.3 mm was received in 10 rainy days during 2018-19 and 449.7 mm was received in 26 rainy days during 2019-20. Hand weeding was done twice at 21 and 43 days after sowing. Need based plant protection measures were taken up.
 
Plant sampling
 
Five random plant samples were collected from each plot (25.92 m²) at the time of harvesting for recording observations on plant height, no. of branches per plant  yield attributing characters and grain as well as stalk yields were recorded per plot. Harvest Index and net returns were calculated from this data.
 
Statistical analysis
 
Experimental data collected was subjected to statistical analysis by adopting Fishers method of analysis of variance (ANOVA) as outlined by Gomez and Gomez (1984), Critical Difference (CD) as calculated wherever the ‘F’ test was found significant at 5 per cent level.

The data on plant height, number of branches plant^-1, number of pods per plant, pod length, 100 seed weight and grain yield, along with the stalk yield of pigeonpea as influenced by varieties, crop geometry and their interaction during the course of investigation are critically interpreted and results are presented below.
 
Effect of variety on growth, yield parameters, yield and economics of pigeonpea
 
In both the years the plant height recorded at harvest were significantly influenced by varieties. Among the four varieties tested significantly the highest plant height was recorded with LRG-52 in both the years (Table 1). This might be due its indeterminate growth habit of LRG 52 compared to determinate growth habit of super early varieties. The lowest plant height was recorded with ICPL 20338, but which was at par with ICPL 11255.



The number of branches plant^-1 was significantly influenced by varieties in both the years, significantly the highest number of branches per plant was recorded with LRG 52. Among the three super early varieties, ICPL-20325 produced the more number of branches plant^-1. More number of branches plant-1might be due to the indeterminate nature of these genotypes.

Number of pods plant^-1and pod length were significantly influenced by varieties in both the years, ICPL- 20325 was recorded significantly the highest number of pods plant^-1 and highest pod length (Table 2). The highest number of pods per plant might be due to genetic nature of the variety and availability at bud initiation and grain filling stages. Similar observations have also been reported by Kashyap et al., (2003), Tikle and Gupta (2006) and Birendra et al., (2017). The100 grainweight was significantly influenced by varieties, among the four varieties LRG 52 recorded the highest test weight, this might be due to its long duration and genetic nature of the variety.

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In both the years as well as mean grain yield was significantly influenced by varieties (Table 3), the highest grain yield was recorded with ICPL- 20325 (1098 kg ha^-1). ICPL- 20325 (V2) variety could escape moisture stress at pod filling stage as it is extra early duration variety (97 days), while, LRG 52 couldn’t as it is of 150 days duration variety. Similar results were reported by Ramanjaneyulu et al., (2017). Among the super early varieties the higher grain yield of ICPL- 20325 might be due to high genetic yield potential, which was reflected through higher values of certain growth and yield attributes of this genotypes and their cumulative effect on yields. The genetical differences in seed yields were might be partially due to genetical efficiency of the genotype to convert biological yield into economic yield. These results were in conformity with the findings of Singh et al., (2014). Check variety LRG 52 recorded the lowest pod yield due to moisture stress coincides with grain filling, which is the critical period for moisture stress.

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Harvest index in both the years was significantly influenced by varieties, the highest was recorded with ICPL- 11255, but which was statistically on par with ICPL- 20338 during 2018-19 and which was also on par with ICPL- 20325 during 2019-20. This might be due to less vegetative growth of super early varieties (determinate growth habit) compared to check variety LRG-52. The check variety LRG-52 recorded the lowest harvest index. Among the varieties ICPL- 20325 recorded the higher net returns.
 
Effect of crop geometry on growth, yield parameters, yield and economics of pigeonpea
 
Crop geometry didn’t have any significant influence on the plant height. The number of branches plant-1 was significantly influenced by crop geometry and found superior at 60 cm x 15 cm (Table 1) as compared to other. The more number of branches per plant in wider spacing might be due to better growth of plant because of optimum resources available to individual plant and their maximum utilization throughout the growth period. Pod length was not significantly influenced by crop geometry.

Among the crop geometries, the highest number of pods plant^-1 with 45 cm x 15 cm during 2018-19 and with 60 cm x 15 cm during 2019-20, but which was on par with 45 cm x 15 cm (Table 1). In contrast, lower values of pods/plant were observed from closer spacing. The better availability of growth resources like water, nutrients, air and better cultural practices in wider plant geometry helped the plants to exhibit their full potential and produced higher yield attributes than closely spaced plants.

The results presented in Table 3 revealed that 100 seed weight was not significantly influenced by the crop geometry and the finding was in accordance with that of Islam et al., (2008) and Parameswari et al., (2003). In both the years as well as mean grain yield of pigeonpea was significantly influenced by crop geometry, significantly the highest grain yield was recorded at 45 cm x 15 cm (Table 3). This might be due to higher number of pods per plant at 45 cm x 15 cm and optimum plant population compared to 30 cm x 15 cm and 60 cm x 15 cm. These findings are in conformity with the observations of Ammaiyappan et al., (2021).

In both the years of testing, harvest index was significantly influenced by crop geometry, the highest harvest index was recorded with 60 cm x 15 cm, but which was on par with 45 cm x 15 cm in both the years. Higher net returns were recorded with crop geometry of 45 cm x 15 cm.
 
Interaction effect of varieties and crop geometry on growth, yield parameters and yield of pigeonpea
 
Interaction between varieties and crop geometry didn’t have any significant influence on the plant height, number of branches plant^-1 and pod length (Table 1) as well as on 100 grain weight (Table 3) in both the years. Interaction had a significant influence on number of pods plant^-1 in both the years. ICPL 20325 at crop geometry of 45 cm x 15 cm recorded the highest number of pods per plant. LRG 52 at 60 cm x 15 cm recorded the more number of pods per plant.

Interaction between varieties and crop geometry has a significant influence on grain yield of both the years (Table 4) as well as on mean grain yield (Table 5). Pigeonpea varieties ICPL- 20325 and ICPL- 11255 recorded higher grain yield at crop geometry of 45 cm x 15 cm. ICPL- 20338 at crop geometry of 45 cm x 15 cm recorded higher grain yield during 2019-20 (Table 4) and mean grain yield (Table 5).  LRG-52 variety recorded higher grain yield at crop geometry of 60 cm x 15 cm.

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In both the years, harvest index was not significantly influenced by interaction effect. Higher net returns were recorded with ICPL- 20325 at 45 cm x 15 cm.

The present investigation revealed that, the yield and monetary advantages were higher in ICPL- 20325, which indicated that for rabi season under rainfed conditions of coastal region, an early maturing indeterminate variety was more profitable than super early and late maturing varieties. Crop geometry of 45 cm x 15 cm was found optimum for super early and early maturing varieties (ICPL- 20325, ICPL- 11255 and ICPL- 20338), whereas late maturing variety (LRG-52) 60 cm x 15 cm was found optimum for rabi season under rainfed conditions of coastal region.