Legume Research

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Legume Research, volume 45 issue 9 (september 2022) : 1122-1129

Microclimate Modification through Groundnut-Pigeon Pea Intercropping System and its Effect on Physiological Responses, Disease Incidence and Productivity

C. Sudhalakshmi1,*, S. Rani1, N.K. Sathyamoorthi1, B. Meena1, S.P. Ramanathan1, V. Geethalakshmi1
1Coconut Research Station, Tamil Nadu Agricultural University, Aliyar Nagar-642 101, Tamil Nadu, India
  • Submitted21-07-2021|

  • Accepted08-11-2021|

  • First Online 15-12-2021|

  • doi 10.18805/LR-4747

Cite article:- Sudhalakshmi C., Rani S., Sathyamoorthi N.K., Meena B., Ramanathan S.P., Geethalakshmi V. (2022). Microclimate Modification through Groundnut-Pigeon Pea Intercropping System and its Effect on Physiological Responses, Disease Incidence and Productivity . Legume Research. 45(9): 1122-1129. doi: 10.18805/LR-4747.

Background: Groundnut (Arachis hypogaea) is the predominant leguminous oilseed crop of India which has turned out to be a sensitive victim to climate change episodes like rising CO2 levels, erratic rainfall pattern, high temperature and moisture stress leaving deleterious imprints in physiology, disease resistance, fertility and productivity. Globally climate change is anticipated to pull down groundnut productivity by 11-25%. Agronomic manipulations like altered time of sowing, intercropping and irrigation management helps in microclimate modification towards reaping higher productivity and economic returns in groundnut.

Methods: Field experiments were conducted during 2019-2021 on sandy clay loam soil (Fluventic Ustropept) in a Randomized Block Design with three factors viz., differential cropping systems (sole groundnut, groundnut + red gram intercropping), rainfed and irrigation systems and differential sowing windows (Second fortnight of June, first and second fortnights of July). Growth parameters, physiological traits viz., photosynthetic rate, transpiration rate, stomatal conductance, canopy temperature and light interception, incidence of foliar diseases viz., leaf spot and rust; soil borne disease viz., stem rot, root rot and productivity of groundnut were recorded at critical crop growth stages.

Result: Canopy temperature was higher in sole groundnut system while light interception was higher in groundnut - redgram intercropping system, however system productivity did not register statistical superiority between the cropping systems. Irrigated system exerted its influence over rainfed system in terms of pod and kernel yield of groundnut. Sowing of groundnut during second fortnight of June was beneficial than July sowing in pod and kernel yield of groundnut due to uniform distribution of rainfall during the growth and reproductive phases of crop. Although differential cropping systems did not register their impact on disease incidence of groundnut, irrigated system and first sowing windows recorded minimum incidence of root rot, stem rot, early leaf spot, late leaf spot and rust diseases compared to rainfed system and July sowing.

The fourth assessment report of the Inter-Governmental Panel on Climate Change (IPCC, 2007) exacerbates the unabated increase in atmospheric concentrations of carbon dioxide, methane and nitrous oxide greenhouse gases (GHGs) since 1750 together with their deleterious impacts on crop production. The CO2-eq concentration in the atmosphere is expected to rise from 478 to 1100 ppm by the end of the 21st century (IPCC, 2014). Heavy precipitation (Sai et al., 2016), increased risk of drought, prolonged dry spells, total dry days and decreased light interception (Mishra and Liu, 2014) are expected to be the lethal consequences of global warming in India. Agriculture is a sensitive victim to the catastrophes of climate change and hence there is a dire need to manage the negative impacts of climate change in crop production by devising appropriate adaptation strategies (Rao and Rao, 2016). Microclimate modification is an effective tool towards mitigating the impact of climate change through altered time of sowing, intercropping strategies, tillage, mulching, establishing shelter belts and irrigation management by impacting canopy temperature, wind velocity, light interception and transpiration losses (Kingra and Kaur, 2017) which can favour better growth and yield of crops (Mahi and Kingra, 2013).
               
Groundnut (Arachis hypogaea L.) is an important leguminous oilseed and food crop of India belonging to C3 group of plant kingdom, spreading over an area of 4.70 million hectares (ha) with a production of 7.40 million tonnes and productivity of 1268 kg ha-1 (DAC and FW, 2016). 

In India about 83% of the total groundnut area is rainfed with the cultivation taken during the monsoon season (June/July to October/November) and the remaining 17% under irrigated conditions (October-March) (Singh et al., 2014). Globally climate change is expected to pull down groundnut productivity by 11-25% (Van Duivenbooden et al., 2002) and early stage agronomic adaptation strategies (Aggarwal, 2008) will help a great deal in sustaining the productivity. Thus an attempt was made at Coconut Research Station, Aliyarnagar, Tamil Nadu Agricultural University, Coimbatore during 2019-21 to elicit the impact of altered sowing windows, irrigation regimes and cropping systems on physiological responses, disease incidence and productivity of groundnut in sole groundnut and groundnut-redgram cropping system.
A field experiment was conducted at Coconut Research Station, Aliyarnagar (10°29`499²N and 76°58`821²E) during 2019-2021 on sandy clay loam soil classified taxonomically as Fluventic Ustropept, testing low for KMnO4-N (250 kg ha-1) and organic carbon (4.2 g kg-1),  medium for Olsen P (14.1 kg ha-1) and NNH4OAc-K (248 kg ha-1). The station receives southwest monsoon during the first fortnight of June and ends in August with an annual rainfall of 808 mm. Experiment was conducted in a randomized block design in plots of (5 × 5) m2 with each treatment comprising of three factors, replicated four times.
       
Factor A includes two cropping systems (C1 - Sole groundnut (variety BSR 2) and C2 - Groundnut + Redgram (CO (Rg)1) in the ratio of 6:1); Factor B comprises of three irrigation regimes viz., I1 - Rainfed and I2 - Irrigated systems (Irrigation at sowing, flowering, pegging and pod development stages); Factor C encompasses three sowing windows viz., S1 - Second fortnight of June (June 17),  S2 -  First fortnight of July (July 2) and S3 - Second fortnight of July (July 17).
       
Spacing of (30 × 10) cm for groundnut and (60 × 20) cm for red gram was adopted. For groundnut, nutrient (N- P2O5-K2O) schedule of 25-50-75 kg ha-1 (Irrigated) and 12.5-25 -37.5 kg ha-1 (Rainfed) and for redgram 25-50 -25 kg ha-1 (Irrigated) and 12.5-25-12.5 kg ha-1 (Rainfed) was adopted. Growth parameters viz., plant height, leaf area index, dry matter production; Physiological traits viz., photosynthetic rate, transpiration rate, stomatal conductance, canopy temperature and light interception were recorded at 30, 60, 90 and 120 DAS (Days After Sowing) using Portable Photosynthetic System (LI-6400 Xt (LiCor. Lincoln, Nebraska, USA) and Line Quantum Sensor. Yield parameters viz., number of pods per plant, pod and kernel yields were recorded at harvest. Rainfall received during the experimental period and irrigation water supplied was quantified.
       
Intensity of soil borne diseases viz., collar rot at 30 DAS, dry root rot at 60 DAS and stem rot at 70 DAS were recorded. Disease incidence was calculated employing the formula:
 
 
Intensity of foliar diseases viz., early leaf spot (ELS) at 45 DAS, late leaf spot (LLS) and rust at the time of physiological maturity were recorded by random selection of 25 plants per plot. Modified 1-9 disease scale was used for scoring of groundnut late leaf spot and rust diseases.
       
Per cent disease index (PDI) was calculated using the formula:
 
                                                   
The data collected from the experiments were pooled and statistically scrutinized as suggested by Gomez and Gomez (1992) and the critical difference (CD) was computed at five per cent probability.
Weather variables
 
Air temperature ranged from 17.5°C to 37°C during the first sowing windows, between 17.5 and 37.0°C during second sowing windows and 17.0 and 37.0°C during the third sowing windows. The quantum of rainfall received during the first, second and third sowing windows  were 517.7, 478.7 and 451.3 mm during 2019-20 and 340.4, 315.5 and 352.2 mm during 2020-21 respectively. The quantum of rainfall received was relatively higher during the first sowing windows (Second fortnight of June) in 2019-20 and third sowing windows during 2020-21. However, the number of rainy days was higher during the first sowing windows during both the experimental periods (Table 1a and 1b). Water supplied through irrigation was 120 mm during 2019-20 and 210 mm during 2020-21.
 

Table 1a: Weather variables recorded in the Agro Meteorological Observatory of CRS, Aliyar Nagar (2019-20).


 

Table 1b: Weather variables recorded in the Agro Meteorological Observatory of CRS, Aliyar Nagar (2020-21).


 
Growth attributes
 
Growth attributes viz., plant height, leaf area expansion and dry matter production showed a progressive increase with the advancement of crop growth stages and are presented in Table 2, 3 and 4. Plant height recorded at various stages of crop growth did not reveal statistical variation among the factors of study. Leaf area index (LAI) and drymatter production were statistically superior in sole groundnut system (C1), irrigated condition (I2) and during first sowing windows (Second fortnight of June) (S1). Irrespective of the factors of study, leaf area index shot up till 90 DAS and thereafter a dent was witnessed. Increased LAI and drymatter production in sole groundnut than the intercropping system may be attributed to the relative competition offered by the intercrop for natural resources interms of water and solar radiation. Soil water deficit at vegetative stage of groundnut has a setback in internodal length (Ochs and Womer, 1959), leaf area expansion, leaf area index (Lopez et al., 1996), in drymatter accumulation and thus in the present study, rainfed condition recorded a depression in leaf area index and dry matter accumulation irrespective of the crop growth stages. Growth attributes responded favourably to the first sowing windows compared to second and third sowing windows which may be due to the favorable microclimate for better performance through uniform distribution of rainfall and optimum air temperature. 
 

Table 2: Differential effect of treatments on plant height (cm) of groundnut at critical crop growth stages.


 

Table 3:Differential effect of treatments on leaf area index (LAI) of groundnut at critical crop growth stages.


 

Table 4:Differential effect of treatments on dry matter production (kg ha-1) of groundnut at critical crop growth stages.



Physiological traits
 
Canopy temperature registered a gradual decline and the rate of transpiration expressed an increasing trend with the advancement of crop growth stages. Canopy temperature (°C) was higher in sole groundnut than groundnut-red gram system which may be attributed to the high intensity in reflection of solar radiation in sole groundnut system compared to intercropping system. Among the irrigation regimes, rainfed system recorded higher canopy temperature than irrigated system and the results are in compliance with Reddy et al., (2003) who recorded higher canopy temperature than air temperature in rainfed groundnut. The plants under moisture deficit conditions transpire less and become warmer which can be well corroborated with the present study. The impact of sowing windows was influential on canopy temperature only at 90 DAS and the gas exchange parameters viz., rate of transpiration and canopy temperature (Table 5) were comparatively higher in first sowing windows (June 17) followed by second and third windows. Transpiration rate was higher in intercropping system than sole groundnut system which is in close compliance with Pinto et al., (2019).  Transpiration rate was higher in irrigated system than rainfed system and the results are in accordance with Li et al., (2013) who contemplated that drought can reduce photosynthesis as well as transpiration due to closure of stomata. Rate of transpiration was higher in the first sowing windows followed by second and third sowing windows.
 

Table 5:Differential effect of treatments on canopy temperature (oC) and transpiration rate (m mol H2O/m2/s) of groundnut at critical crop growth stages.


       
Stomatal conductance is the key variable that influences gas exchange through regulation of water vapour and carbon-di-oxide diffusion (Wallace et al., 1990). Stomatal conductance and photosynthetic rate (Table 6) did not reveal statistical variation among the crop establishment methods, however, both the parameters were significantly higher under irrigated system (I2) than the rainfed system. Bhagsari et al., (1976) has postulated that when the relative water content decreases below 80%, groundnut crop shows adaptation to drought by reducing stomatal conductance which has a significant bearing on the rate of photosynthesis (Boote and Williams, 1995). Under moisture stress, partial closure of stomata (Patil and Patil, 1993) resulting in repartitioning of the incident energy leading to increased temperature was recorded in oats by Sandhu and Harton (1978). Stomatal conductance was not altered by the differential sowing windows at 30 and 90 DAS however at 60 DAS stomatal conductance was higher in first sowing windows followed by the other two sowing windows which may be attributed to the hydroactive feedback in stomatal conductance to evaporative demand and soil drought involving abscisic acid production in leaves (Bukley, 2019). However photosynthetic rate was higher in first sowing windows which may be due to favourable weather variables like optimum temperature, sunshine hours and solar radiation compared to the other sowing windows.
 

Table 6:Differential effect of treatments on stomatal conductance (mol H2O/m2/s) and photosynthetic rate (ì mol CO2/m2/s) of groundnut at critical crop growth stages.


       
Light interception was higher in intercropping system than sole cropping of groundnut (Table 7). In maize - peanut intercropping system, Jiao et al., (2008) registered an enhanced utilization efficiency of strong light by maize and weak light by peanut thus proving intercropping system to be efficient. Hussainy et al., (2020) observed higher light interception in groundnut + pearlmillet intercropping than sole groundnut system. No significant differences were observed between rainfed and irrigated systems on light interception. However, light interception was higher in the first sowing windows compared to the second and third windows probably due to more sunshine hours in June compared to July. As a natural corollary, soil moisture content was higher in intercropping system due to lesser evaporation losses, in irrigated system and during first sowing windows both at 0-15 and 15-30 cm depths due to the even distribution of rainfall throughout the crop growth period.
 

Table 7: Differential effect of treatments on light interception (%) and soil moisture content (%) of groundnut at critical crop growth stages.


 
Disease incidence
 
Disease incidence did not reveal statistical variation between the differential cropping systems adopted and the results are in accordance with Boudreau et al., (2015) who observed inconsistency in disease incidence on intercropping groundnut with maize. Irrigated crop and the first sowing windows exhibited minimum incidence of early and late leaf spot, rust and collar rot diseases (Table 8). Pieces of evidence have accumulated stating that when groundnut plants are predisposed to intermittent rains, high relative humidity and temperature of 20 to 26°C (Siddaramaiah et al., 1980, Samui et al., 2005), the above diseases are likely to occur. High soil temperature is favourable for collar rot infection (Kolte, 1985) and thus in the present study, high soil temperature in rainfed regime might have contributed for the incidence of diseases. Due to better solar radiation, optimum temperature and uniformity in distribution of rainfall throughout the crop growth period, the incidence of diseases was less in June sowing compared to the second and third sowing windows.
 

Table 8: Differential effect of treatments on the incidence of soil borne and foliar diseases in groundnut.


 
Productivity of groundnut
 
During both the years of experimentation, number of pods per plant, pod yield and kernel yield did not reveal spectacular variation between sole and intercropping systems (Table 9). Irrigated system exerted positive influence on pod and kernel yield of groundnut than the rainfed system. An array of evidences accumulate stating that water stress reduces pod yield and biomass production of groundnut (Dang et al., 2013) due to reduced dry weight of roots and water use efficiency (Songsri et al., 2009), reduced conductance of stomata and rate of carbon exchange (Egli and Bruening, 2001), reduced leaf water content and cell membrane stability together with concomitant reduction in kernel yield (Dang et al., 2013), decreased chlorophyll biosynthesis (Nigam and Aruna, 2008), decreased drymatter production and atmospheric-N fixation (Pimratch et al., 2008), variation in amount and distribution of rainfall (Yayock and Owonubi, 1985). Pod and kernel yields were higher in first sowing windows (June sowing) followed by second and third windows which may be attributed to the variations in temperature and solar radiation intercepted with different sowing windows and the results are in proximity to that of Meena and Yadav (2015).

Table 9: Differential effect of treatments on yield attributes and yields of groundnut at critical crop growth stages.

In the present study, effect of sole groundnut and groundnut + red gram intercropping systems, rainfed and irrigated moisture regimes and differential sowing windows (Second fortnight of June, first fortnight of July and second fortnight of July) were evaluated for physiological responses, disease incidence and productivity of groundnut. Results clearly demonstrate that physiological traits viz., photosynthetic rate, transpiration rate and stomatal conductance were higher in sole groundnut cropping, irrigated system and during first sowing windows. Light interception was higher in red gram intercropping than sole groundnut system, in irrigated regime and in first sowing windows (Second fortnight of June).  Sole groundnut and rainfed system registered higher canopy temperature than intercropping and irrigated crop. Growing red gram as intercrop in groundnut at 6:1 ratio did not affect the yield of groundnut. Irrigated system exerted its influence over rainfed system in terms of pod and kernel yield of groundnut. Sowing of groundnut during the second fortnight of June was beneficial than July sowing due to uniform distribution of rainfall during the growth phase. Irrigated system and first sowing windows recorded minimum incidence of root rot, stem rot, early leaf spot, late leaf spot and rust diseases although differential cropping did not register their impact on disease incidence in groundnut.

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