Legume Research

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Role of Summer Legumes in Sustaining the Rainfed Groundnut Productivity

T. Prathima1,*, K.V. Nagamadhuri1, T.M. Hemalatha1, G. Subramanyam1, C.V. Madhuri1, S. Mobeena1
1Regional Agricultural Research Station, Acharya N.G. Ranga Agricultural University, Tirupati-517 501, Andhra Pradesh, India.
  • Submitted04-03-2024|

  • Accepted12-06-2025|

  • First Online 26-06-2025|

  • doi 10.18805/LR-5314

Background: In the face of quickly shifting weather patterns, sustainable agricultural production is essential. The Green Revolution in India led to intensive farming which led to loss of soil biota and degradation of organic matter content resulted in lower soil quality.

Methods: A four-year study (2016 to 2019) was taken up at Regional Agricultural Research station, Tirupati andhra Pradesh, India by growing 6 leguminous crops such as Pillipesara, Rice bean, Sunhemp, Green gram, Horse gram and Cowpea during summer under rainfed condition as a preceding crop and incorporated before sowing of Kharif groundnut. FYM was also tested as one of the treatments for comparison.

Result: Results revealed that the choice of green manure crop significantly influenced groundnut yields. Growing and incorporating cowpea before Kharif groundnut resulted higher yields (1744 kg/ha) followed by green gram (1699 kg/ha) compared to fallow (1478 kg/ha). Microbial analysis at the end of the experiment revealed that highest fungal population (28.3 x 104 cfu/g) and actinomycet population (24 x 104 cfu/g) was observed in sunhemp followed by cowpea (27 x 104 cfu/g of soil) and (19.7 x 104 cfu/g) compared to fallow (7 x104 cfu/g) and (4.7 x 104 cfu/g). The highest bacterial population (33.3 x 106 cfu/g) was observed with green gram followed by horse gram (26.7 x 106 cfu/g) and cowpea (26.3 x 106 cfu/g). The highest organic carbon content (0.5 per cent) was observed with sunhemp followed by horse gram and cowpea (0.49 per cent) compared to fallow (0.45 per cent). Leguminous crops act as cover crops during summer in maintaining the soil temperature and protecting the soil biota and as green manure crops in enriching the soil during kharif.

The sustainable production of agricultural products is imperative in the context of rapidly changing climate, which pose a significant threat to global food production. In India, the Green Revolution successfully met the needs of the growing population, but has taken a toll on soil quality, diminishing organic matter content and destroying crucial soil biota (Gardi et al., 2013). To restore the degraded soil health, cover crops, mulching and other organic management practices like incorporation of green manure etc. are used along with growing pulses. Green manure helps in gaining back the deteriorated soil quality (Israt and Parimal, 2023). It would improve the nutrient status of the soil and also increase the soil biota. The choice of an appropriate species of legume has a great impact on the amount of biomass, N accumulation and rate of nutrient release into the available forms (Jyoti  et al., 2023). Live mulch, without the need for long fallow periods, is suggested as a strategy for sustaining yields. Mulching not only contributes to soil temperature regulation but also enhances soil structure infiltration rate and stimulates microbial and meso-faunal activity. Furthermore, mulching plays a role in carbon stock by promoting mineralization and reducing erosion (Nandwa, 2001). The impact of organic management on microbial communities, specifically bacterial populations and enzyme activities, has been well-documented. However, the effects of organic modification on soil organic matter (SOM) traits and functioning, particularly in combination with cover crops, remain largely unknown. Recent studies highlight the potential of organic agriculture to increase SOM content by incorporating substantial amounts of carbon into the soil, leading to an observed increase in soil organic carbon (SOC) stocks in organic farming (Gattinger et al., 2012: Lori et al., 2017). Cover crops, in addition to increasing microbial biomass and activity, induce changes in microbial community structure, making them integral to sustainable agricultural practices (Buyer et al., 2010).
       
Amidst the ongoing climate change scenario, characterized by rising temperatures and increased monsoon irregularities, crop production in rainfed areas is challenging due to intermittent droughts. Decreased organic matter and unpredictable rainfall patterns significantly impact dryland agriculture. IN addition, producing sustainably is becoming essential to food systems and agriculture (De Ruiter  et al., 1993). Because they provide a variety of benefits in accordance with sustainability principles, legume crops have the potential to be very significant in this context (Stagnari et al., 2017). Actions such as appropriate crop rotation are recommended to sustainably manage soil resources and ensure long-term agricultural viability (Derner and Schuman, 2007; Lal, 2009). Recognizing the need for sustainable alternatives, this study explores the efficacy of leguminous crops as a protective soil cover during summer and also an organic management strategy on rainfed groundnut productivity. This study also aims to contribute insights into maintaining soil fertility, productivity and carbon sequestration, thereby reducing the greenhouse effect.
Location and design
 
Experiment was taken up at Regional Agricultural Research station, Tirupati, Andhra Pradesh, India.  Experiment was laid out in randomized block design with three replications. The test crop groundnut was raised in plots of 8 x 5 m with a spacing of 30 ´ 10 cm. A recommended fertilizer dose of 20, 40, 50 kg N, P2O5 and K2O/ha was applied at sowing followed by 500 kg /ha of gypsum was top dressed during flowering stage. The experiment was conducted for 4 years consecutively from 2016 to 2019.
 
Treatments
 
The preceding legume crops grown were Pillipesara (Vigna tribolata), rice bean (Vigna Umbellata), sunhemp (Crotalaria juncea), green gram (Vigna radiata), horse gram (Macrotyloma uniflorum), Cowpea (Vigna unguiculata). Farm Yard Manure (FYM) was also used as a treatment in the experiment. An absolute control was also maintained. The treatments were designated as, T1: Pillipesara - Groundnut, T2: Rice bean - Groundnut, T3: Sunhemp - Groundnut, T4: Green gram - Groundnut, T5: Horse gram - Groundnut, T6: Cowpea - Groundnut, T7: FYM - Groundnut, T8: Control. The preceding legume crops were sown at the receipt of sufficient rainfall during the month of May every year. In situ incorporation of these legume crops was taken up at the time of 50% flowering (Table 1).

Table 1: Dates of sowing of preceding legume crops, dates of incorporation, rainfall received for all the four years.

kharif 2016
 
Among different legume crops tried during summer before sowing of groundnut during kharif 2016, the highest groundnut yields (1405 kg/ha) were recorded when cowpea was taken as base legume crop before groundnut followed by farm yard manure applied treatment before sowing of groundnut (1363 kg/ha) (Table 2). The least groundnut yield was recorded with rice bean sown as preceding crop before sowing of groundnut (811 kg/ha).  The groundnut crop received 168 mm rainfall only during crop growth period hence three irrigations, one during pegging stage and two irrigations during pod development stage has given to protect the crop.

Table 2: Yield and yield attributes of Groundnut Kharif, 2016.



kharif, 2017
 
Legume crops were sown with 11 mm of rainfall on 21st May and incorporated after 31 days. In the same plots groundnut crop was sown and a maximum groundnut yield (2193 kg ha-1) was recorded with cowpea as preceding crop followed by farm yard manure applied plots (2008 kg/ha) (Table 3). The minimum groundnut yield was recorded with sunhemp (1703 kg/ha).  The groundnut crop received 854 mm rainfall during its crop period and took 114 days duration.

Table 3: Yield and yield attributes of groundnut Kharif, 2017.


 
kharif, 2018
 
Legume crops were sown with 21.4 mm of rainfall on 1st May and insitu incorporated after 56 days. After 18 days, groundnut was sown and a highest groundnut yield (1581 kg ha-1) was recorded with green gram as a preceding crop followed by cowpea (1191 kg ha-1) (Table 4). The least groundnut yield was recorded with pillipesara (785 kg ha-1).  The legume crops received 129.8 mm rainfall and ground-nut crop received 256.4 mm rainfall during its crop period.

Table 4: Yield and yield attributes of groundnut Kharif, 2018.


 
kharif, 2019
 
Legume crops were sown with 8.0 mm of rainfall on 29th May and insitu incorporated after 50 days. In the same plots, groundnut was sown after 23 days. During this year, no much difference was found among all the treatments on pod yield as well as other auxillary characters and was observed to be non-significant (Table 5).  In summer, during crop period of legume crops only 102 mm rain was received in 2 rainy days due to which the biomass of legume crops was observed to be very poor. During the crop period of groundnut 724.4 mm rainfall was received in 40 rainy days with good distribution. This rainfall effect masked the benefit of raising legume crops prior to kharif groundnut during the year.

Table 5: Yield and yield attributes of groundnut Kharif, 2019.


 
Pooled results of the experiment (kharif, 2016-2019)
 
Pooled analysis revealed that growing summer legumes as preceding crop during summer rains maintained the soil health by reducing soil temperatures and increasing the soil biota and assisted in better performance of Kharif Groundnut. Among different legumes crops incorporated, in-situ incorporation of cowpea resulted in a higher groundnut production (1744 kg/ha) followed by green gram (1699 kg/ha) which are comparable (Table 6). Furthermore, application of FYM during summer rains also found to be next best alternative to cowpea and green gram in achieving groundnut yield (1609 kg/ha). The percentage increase of ground nut yields from in-situ incorporation of cowpea over control is 18.6%. The higher yields of groundnut with in-situ incorporation of cowpea might be due to the addition of higher amount of nutrient rich biomass combined with higher soil organic carbon that might have provided the sustainable availability of micro and macro nutrients for the succeeding crop eventually resulting in higher yield and yield attributes of ground nut crop. Ramanjaneyulu et al. (2021) reported higher addition of biomass with in-situ incorporation cowpea compared to other legumes. In addition to that, in-situ incorporation of cowpea has also resulted in enhanced water holding capacity and microbial activity which have a significant impact on soil health thus improve in performance of ground nut crop. Nikita et al. (2015) has reported increase in yields of sweet corn with in-situ incorporation of green manures compared to control. Chaitanya Kumar et al. (2022) recorded higher yields of chickpea with in-situ incorporation of cowpea when compared to green gram and pillipesara. Similar nature of results was also reported by rani et al. (2022). The least yields of ground nut were recorded with control.

Table 6: Yield and yield attributes of Groundnut (pooled analysis of 2016-2019).



Microbial population in different green manure treatments
 
The Soil microbial populations in different legume crops sown before groundnut revealed the highest fungal population (28.3 x 104 cfu/g) and actinomycet population (24 x 104 cfu/g) in sunhemp followed by cowpea plots (27 x 104 cfu/g) and (19.7 x 104 cfu/g) (Table 7 and Plate 1 and 2). The highest bacterial population (33.3 x 106 cfu/g) was observed with green gram followed by horse gram (26.7 x 106 cfu/g) and cowpea (26.3 x 106 cfu/g). Legume incorporation treatments found to be superior in maintaining soil health compared to FYM application. In a study conducted by Muhammad et al. (2021) revealed that in comparison to no cover crop, the overall number of bacteria and fungus in the soil as well as their respective groups increased by 7-31%.

Table 7: Microbial population in different green manure treatments, 2019.



Plate 1: Microbial population in different green manure treatments.



Plate 2: Microbial Population in different green manure treatments.


 
Soil organic carbon
 
The initial soil organic carbon of the experimental field is 0.39. Over a period of years, the organic carbon in all the treatments has increased. The highest soil organic carbon content (change as 5.0 g kg-1) was observed with sun hemp followed by horse gram and cowpea (4.9 g kg-1 per cent) compared to fallow (4.5 g kg-1 per cent) (Table 8). The least values of soil organic carbon were recorded with control.

Table 8: Initial and final organic carbon in different green manure treatments, 2019.

The present investigation confirms a positive and significant impact due to in-situ incorporation of legume green manures on yield of succeeding ground nut crop. Among the different treatments tried, cowpea in-situ incorporation has resulted in higher yields of ground nut along with higher microbial population. The least yield and microbial population were observed with control. Instead of leaving land fallow, in-situ incorporation of legume green manures protect soil from erosion and loss of nutrients and also restore the soil health.
 
Authors are unaware of any conflict of interests.

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