Introduction

Groundnut, the king of oil seeds is one of the important legume crops cultivated predominantly under rain-fed conditions in the tropical and semi-arid tropical countries including India, where it provides a major source of oil, carbohydrates and proteins (Pasupuleti et al., 2016; Ondulla, 2020). The seed is used mainly for edible oil and contains nearly half of the essential vitamins and one-third of the essential minerals. It is one of the most nourishing foods available in the world (Fonte et al., 2019; Samtiya et al., 2020). Apart from their nutritional value, groundnut has considerable medicinal value (Bhat et al., 2019). It is consumed in many ways and various forms. Due to its high monosaturated content, it is considered healthier than saturated oils and is resistant to rancidity (Juliet et al., 2019). Groundnut is particularly valued for its protein content (26%). In addition to protein and oil, groundnut is a good source of Ca, P, Fe, Zn and B. Hence, groundnut played an important role in nutritional security to the resource poor farmers (Meena et al., 2007; Chris et al., 2020). In addition, the haulms provided excellent fodder for livestock, cake obtained after oil extraction was used in animal feed and overall, the crop acted as good source of biological nitrogen fixation (Nautiyal et al., 2011; Kumari and Reddy, 2019). Groundnut is the sixth most important oilseed crop in the world.

Globally, the crop is raised in 25.7 million ha with a total production of 37.1 million mt. The average productivity is 1400 kg ha^-1. India shares 22% of the world production (area 4.8 mha, production 5.9 million MT (Madhusudhana, 2013). The area under rainfed groundnut in Tamil Nadu is 4.4 lakh ha with a production of 9.11 lakh tones during rabi 2018-19. Groundnut is cultivated predominantly in the tropics and subtropics, where the availability of water is a major constraint on yield (Viramani and Singh, 1986; Happy et al., 2018). The crop is subjected to water deficit stress at one stage or another leading to drastic reduction in productivity. This necessitates development of cultivars which can withstand water stress and still can be productive. Reduction in peanut yield resulting from drought has been well documented (Nageswara Rao et al., 1989; Reddy et al., 2003) and Carvalho et al., 2017. Drought during the pod and seed forming stages has been shown to reduce pod yield of peanut by 56-85% (Vincent and Pasala, 2016). Hence, the study was planned with the objectives to evaluate the drought resistant groundnut varieties with high yield and drought tolerance under rabi season through on farm trials forPerambalur district.

Materials and Methods

The present study was carried out in eight farmers’ field in Kadambur village of longitude 11’25’25 N and latitude 78’’43’’24’’ E during 2018-19 to evaluate three genotypes of Groundnut evaluation traits. The trial was conducted in randomized block design (RBD) with three replications and total area under each trial was 0.4 ha. The land was brought to a fine tilth by repeated ploughing and harrowing. The clods were broken and debris was removed. The soil was leveled and ridges were made for sowing. For raising crop, recommended package of practices were followed. The seeds were sown during November to September during, 2018, crop thinning was done for maintaining proper plant spacing of 30×10 cm². The soil of the experimental site was sandy clay loam texture with medium organic carbon content (0.55%), medium in nitrogen (285.0 kg ha^-1 ), low in phosphorus (10.6 kg ha^-1) and medium in potassium (172.0 kg ha^-1) contents. Before fertilizer application, random soil samples were taken from the experimental sites and recommended dose of fertilizers applied as per soil test basis. The farming situation was rainfed and source of supplemental irrigation with bore well. The treatments included: T₁: Farmers Practice, T₂: Dharani and T₃: Co₇. Five plants were selected randomly from each plot for recording observations. The data on plant population, physiological parameters, number of pods plant^-1, pod yield, haulm yield and economics of all the varieties were recorded. Observations on growth characters such as plant height, dry matter production were recorded at 40 DAS, 80 DAS and at harvest from five randomly selected plants in each plot. The samples were collected from sampling rows in each plot for dry matter production and were used for the estimation of DMP. The data obtained from experiments were subjected to statistical analysis by using the statistical software AGRES.  Based on the net plot yield, yield ha^-1 was calculated and expressed in q ha^-1. The cost of cultivation and gross returns were worked out by using prevailing market prices of inputs during the period of investigation. Benefit-cost ratio (BCR) was worked out by using the following formula. Benefit: Cost ratio (BCR) = Gross return (` ha^-1)/ Total cost of cultivation (Rs. ha^-1) (Table 1 and 2).

Table 1: Details of practices in Perambalur district under OFT programme

Table 2: Characteristics of varieties selected for on-farm trial

Results and Discussion

3.1.  Growth parameters

With regard to evaluation of groundnut varieties significant difference were observed on plant height at 40 DAS, 80 DAS and at harvest stage. Dharani recorded the highest value for plant height of 12.2, 33.4 cm and 44.2 cm at 40 DAS, 80 DAS and at harvest stages, respectively (Table 3). It was least in farmer practice at 80 DAS and at harvest. Higher plant height in Dharani may be attributed to the variety which tends to germinate and establish early compared to farmer practice varieties with medium and small seeds. Similar increase in plant height with large seeds was also observed by Singh et al. (1998) and Nandania et al. (1992). Mensah and Okpere (2000) showed the significant differences among the different varieties of groundnut for plant height throughout the growth period.

The variety, Dharani maintained the highest dry matter production (3730 kg ha^-1) on the account of higher magnitude of dry matter in leaves, stem and roots (Table 3). In addition, Co7 and TMV 7also recorded dry matter production of 3308 kgha^-1 and 3105 kg ha^-1 respectively. Among varieties (Dharani) recorded higher relative leaf water content (RLWC) of 67.5 at flowering stage (Table 4).

Table 3: Growth performance on groundnut varieties in farmer’s field (Average of five trials)

Table 4: Chlorophyll and RWC in groundnut leaves during water stress

The lowest relative leaf water content was recorded in farmer’s practice. The highest reduction was recorded in farmer practice (48.4%). Sunitha et al. (2015) suggested that RWC under stress condition could be used as measure of tolerance to stress. Decline in RWC under drought stress was observed earlier growth stage in groundnut. This might be due to reduction in water availability, higher stomata opening and closing. Similar results have been reported in groundnut (Kalariya et al., 2017), in horsegram (Bhardwaj and Yadav, 2012) and in pigeonpea (Kumar et al., 2011). The results obtained in the present study are in agreement with these reports. The chlorophyll content also decreased significantly under stressed condition in all genotypes of groundnut. It has been reported that the loss of chlorophyll under water stress is due to inactivation of photosynthesis (Kumar et al., 2011), furthermore, stress induced reduction is ascribed to loss of chloroplast membrane integrity due to lipid peroxidation.

3.2.  Yield attributes and yield

On-farm trials on varietal evaluation of groundnut varieties revealed that groundnut variety Dharani recorded higher pod yield (24 kg ha^-1), higher number of pods plant^-1 (26), lesser root rot incidence (1.4%) and optimum plant population (26.3 plants m^-2) as compared to Co₇ and farmer practice variety in (Table 4). Groundnut varieties, Dharani and CO₇ recorded 31.76 and 13.82% higher pod yield than check variety, respectively. With regard to haulm yield, Dharani variety recorded highest haulm yield of 4384 kg ha^-1 compared to other varieties. Similar results have been reported in groundnut (Kumari and Reddy, 2018).

Economics

Gross and net returns were Rs. 1,15,324/- and Rs. 66,593 ha^-1, respectively for CO₇ as against Rs. 99,619/- and Rs. 52,277 ha^-1 in the farmers variety. The probable reasonmight due to genotype, lesser incidence of root rot disease coupled with higher number of pods plant^-1 resulting higher pod and haulm yield, these results were in agreement with the findings of (Kumari and Reddy, 2019).

Conclusion

Groundnut variety, Dharani recorded more number of pods per plant, higher pod yield, good withstand under drought condition and performed very well compared to Co₇ and TMV7farmer practice variety under rainfed condition. Farmers are convinced with dharani, as the crop did not suffer from a dry spell of 18-22 days without rain. Thus, groundnut variety Dharani would be better option for rainfed cultivation during rabi season for Peramalur district.

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