Impact of biotic stress management technologies on yield, economics and energy indices of pigeon pea (Cajanus cajan) grown in Central India

The demand of pulses is increasing both in developed and developing countries due to increasing population and vegetarians (Singh and Singh, 2016). The availability of 19.7 to 27.5% protein in pigeon pea seed makes an important rich source of supplement energy of vegetarians’ diet. The production growth rate of pulses is less than 1% annually, while growth rate of human population is 1.58% in India (Singh and Singh, 2016). Consequently, as per recommended dietary allowances for adult male and female is 60 g and 55 g per day, while per capita availability of pulses is @ 42 g per day during 2015. Although, India leads the world both in area and production of pigeon pea, productivity remained almost static during last 50 years. In 2013-14, productivity  was around 25% lower (730 kg ha^-1)  than the world average (910 kg ha^-1). The low productivity and availability of pigeon pea seed is ascribed to various biotic stresses in different regions of the country.
               
Among biotic factors, severe infestation of weeds is observed during rainy season due to slow initial growth of pigeon pea and sowing at wider row spacing resulting in low yield. Reduction in yield due to weeds in pigeon pea to the tune of 40-64% has been reported by Ali (1991) and Kandasamy (1999). Similarly more than 250 insect species and diseases are reported to affect pulses in India (Reddy et al., 1990). Major diseases are wilt (Fusarium udum Butler), sterility mosaic virus (SMV) and blight (Phytophthora drechsleri sp cajani) and insect pests are pod-borer (Helicoverpa armigera Hubner), pod-fly (Meloidogyne, Heterodera and Rotylenchus sp) in field, and bruchids (Callosobruchus sp) in the field and as well as in storage. The infestation of pod borer and SMV increases in pigeon pea due to rise of temperature and prevalence of cloudy weather conditions (Singh and Singh, 2016). Soil born plant pathogens are mostly spread under humid and moist soil environment. Sowing of pigeon pea on flat bed is practiced in India with poor drainage/water stagnation during the rainy season resulting heavy losses to pigeon pea on account of low plant stand and increased incidence of (wilt) phytophthora blight disease (Singh and Singh, 2016). The wilt is one of major disease widely prevalent in North and Central parts of India causing yield loss ranging from 30 to 100% (Reddy et al., 1990). The yield loss due to wilt disease also depends upon the stage of plant and it can approach over 50% and even up to 100% when wilt occurs at the pre-pod stage (Okiror, 2002). Several recommendations popularize the effective control of pod borer by proper dose and time of application of pesticides, whereas indiscriminate use of synthetic pyrethroids or insecticides has resulted in the development of resistance (King and Sawicki, 1990). Bruchids are known to damage pigeon pea both in field as well as in store. Hence avoiding field infestation and curtailing their damage in storage is a must (Kumar, 2005). Pulse beetles (bruchids) attack pigeon pea including Callosobruchus chinensis (L.) and Callosobruchus maculates (Fab.) at mature crop and dried pods. The attack is conspicuous by the round holes and white eggs were laid on the pod walls. In storage, eggs were laid on the seed surface and the round holes with the ‘flap’ on the seed coat. The infestation of bruchids in field has been found to be relatively higher in medium (16.2%) and early (8.4%) cultivars than long duration pigeon pea (Lal and Yadav, 1987). The use of semi-chemicals (sex pheromones) for bruchid control has also been found promising (Phillipps et al., 1996). Drying of seed (<10% moisture) and seed treatment with malathion (for seed purpose) and ethylene dibromide (for food purpose) and also mixing of neem (Azardirechta indica) leaves besides storage of seeds in controlled atmospheric conditions are some of the measures for minimizing the storage losses. However, very little or no information is available on impact of biotic stress management of pigeon pea crop. Therefore, the present study was under taken to evaluate the on farm impact of management of biotic stress of pigeon pea on yield, economic benefits, energy indices and soil physicochemical properties.

On farm studies were conducted to assess the impact of technologies on biotic stresses during two kharif  (Rainy) seasons from 2011 to 2013. Clusters of villages namely, Sirmorkapura, Jigani, Ganjrampur, Khedamebada and Badagaon of district Morena of Madhya Pradesh state of India were selected randomly for trails. The study area lies between 23° 15’ to 26° 45’ N latitude and 70° 30’ E longitude with altitude ranging from 150 to 240 m. The climate of cluster of villages is characterized as semi-arid, extremely cold during December-January (-1.0°C minimum temperature) and hot during May-June (50°C maximum temperature). The weekly minimum and maximum relative humidity was 67 and 98% during first and 48 and 94% during second year, whereas temperature was 3 and 50°C during first and 1 and 47.5°C during second year of experimentation, respectively. Average annual rainfall of this cluster is 701 mm, mostly concentrated in the months of July and August. Annual rainfall received during 2011-12 and 2012-13 was 875 and 1074 mm, respectively (Fig 1).
 

       
Surface (0-20 cm) soil samples were collected for determining initial soil properties and after harvest of pigeon pea from each plot. The soil samples were air dried and ground to pass through a 2 mm sieve. Analysis of soil samples for pH and electrical conductivity (1:2 soil water ratio) and bulk density (0 to 15 cm) was determined by using clod method as described by Black (1965a). Infiltration rate after harvest of pigeon pea was measured by double ring infiltrometer method (Bouwer, 1986). Organic carbon was determined by Walkley and Black (1934) method; available N by Kjeltec-II auto analyzer, P by Olsen et al., (1954) method, S by Chesnin and Yien (1950) method, K by NH₄OAc extraction and micronutrient by DTPA extraction method. The selected soil of farmers’ fields was neutral in nature and sandy loam in texture of alluvial plains. The soils were deficient in organic carbon (2.8 to 4.9 g kg^-1), available N (139 to 187 kg ha^-1), S (8.2 to 13.6 kg ha^-1), Zn (0.45 to 0.59 mg kg^-1), whereas low to medium in available P (8.1 to 12.5 kg ha^-1) and medium to high in available K (206 to 294 kg ha^-1).
       
Ten farmer fields for each trial were selected for assessment of impact of each technology compared to existing farmers’ practices. The intervention impact was statistically analyzed using randomized block design. Intervention details to assess the impact on management of biotic stresses were given Table 1.  A variety of short duration maturity cycle pigeon pea cultivar ‘ICPL-88039’ was sown during 4^th week of June and harvesting at 3^rd to 4^th week of November in both years. The conventional and broad bed furrow (BBF) sowing methods are sown in Fig 2. The recommended dose of fertilizers for this zone was 20 kg N, 50 kg P₂O₅, 20 kg K₂O, 30 kg S ha^-1 for pigeon pea. Full recommended dose was applied as basal application. The sources of N, P, K and S were urea, dia-ammonium phosphate, muriate of potash and elemental sulphur, respectively. The package of practices was followed as per recommendation.
 

 

       
Seed, stalk yield, cultivation cost, gross, net returns and cost benefit ratio were calculated to find out the economics of various interventions under study. Different economic indicators of inputs were also calculated based on the existing market prices. Gross returns were calculated by multiplying seed yield with minimum support price of Government of India, and stalk yield with prevailing market price. Net returns were calculated as: Net return = Gross return-Total cost of production. Energy input and output were calculated by using the procedure described by Devasenapathy et al., (2009). Energy-use-efficiency, energy productivity, specific energy and net energy were calculated using the formula as follows:

Energy use efficiency =

        Energy output (MJ ha^-1) / Energy input (MJ ha^-1);

Energy productivity =

        Seed output (kg ha^-1) / Energy input (MJ ha^-1);

Specific energy =

        Energy input (MJ ha^-1) / Seed + Stalk output (kg ha^-1);

Net energy =

Energy output (MJ ha^-1) - Energy input (MJ ha^-1).

Weed management
 
Application of herbicide (Imazethapyr @ 10% SL 100 g ha^-1, 20 to 25 DAS) provided significantly higher average seed and stalk yield of pigeon pea compared with no use of herbicide (control). The average seed and stalk yield of pigeon pea was 26.2 and 20.8%, respectively higher under use of herbicide compared to control (Table 2). The intervention of weed management gave additional 0.44 t ha^-1 seed and 1.94 t ha^-1 stalk yield of pigeon pea compared to yield of control plots (1.68 t ha^-1 seed, 9.32 t ha^-1 stalk). Pigeon pea is also known to exhibit allelopathy effect (Balakrishnan and Rajendran, 1987) through its decomposing litter fall at the ground and also through the leaf leachates, which were found effective in taking care of weeds from 50 days onwards. Initial six weeks’ period is critical for crop-weed competition. Therefore, weeds must be controlled during this period for obtaining high seed yields (Singh and Sekhon, 2013). Bidlack et al., (2006) also reported that post emergence application of herbicides may help in alleviating weed problem. The use of herbicide significantly increased the net return and benefit cost (B:C) ratio as compared to control. The additional net income of Rs. 16,752 ha^-1 was obtained with use of herbicide compared with total net income of without using herbicide Rs. 53,774 ha^-1. The B:C ratio was 3.51 under use of herbicide, whereas 3.14 under control.
 

       
Further, the energy input was slightly higher (9,797 MJ ha^-1) under use of herbicide compared with control (9,405 MJ ha^-1). The application of herbicide significantly increased the energy output, use efficiency, energy productivity and net energy gains compared with control (Table 3). The increase of energy output, use efficiency, energy productivity and net energy gains with use of herbicide were 22.1, 17.2, 15.7 and 23.7% higher, whereas specific energy used per kg of biomass produced was 14.4% lower compared with control, respectively. The impact of weed control by herbicide on energy outcome parameters was directly and positively related to seed and stalk yield of crop.
 

 
Pod borer management
 
Control of pod borer through use of recommended technology (pheromon trap @ 20 + HaNPV 500 LE + quinolphos 25 EC @ 1.5 litre ha^-1) at ETL level resulted in significantly higher seed and stalk yield, economic benefits, energy input and output of pigeon pea compared to use of only endosulfan @ 1.5 litre ha^-1 (Table 2). The average seed and stalk yield of pigeon pea was 46.1 and 2.8% higher with recommended technique for control of pod borer compared to control. Pod borer management technique gave additional 0.71 t ha^-1 seed and 0.27 t ha^-1 stalk yield of pigeon pea compared with yield of control (1.54 t seed and 9.77 t stalk ha^-1). Similar results were reported by Reddy (2009) in pigeon pea crop. Use of recommended technique for control of pod borer of pigeon pea had significantly increased net return and B:C ratio as compared to control plot. The additional net income was Rs. 24,805 ha^-1 with recommended technique compared with total net income of Rs. 46,926 ha^-1 of control. Similarly, significantly higher B:C ratio (3.48) was recorded with recommended technique compared 2.67 value of control plot.
       
The energy output, energy use-efficiency, productivity and net energy gains were significantly higher with recommended technology as compared to control (Table 3). The increase of energy output, energy use-efficiency, productivity and net energy gains with the recommended technology were 9.5, 4.6, 42.2 and 9.9%, respectively whereas specific energy for producing per kg biomass was 3.6% lower compared with control.
 
Wilt management
 
Results of wilt management recommended technique [seed treatment with Trichoderma viride (bio-control agent and also as a plant health promoter due to its fascinating mechanisms like the production of antifungal metabolites) @ 10 g kg^-1 seed and sowing of pigeon pea on broad bed furrow] significantly increased the average seed, stalk yield and economic benefits of pigeon pea compared to control (Table 2). The average seed and stalk yield of pigeon pea was 12.2 and 5.2% higher with the recommended technique as compared to control. The recommended technique for control of wilt gave additional 0.25 t ha^-1 seed and 0.56 t ha^-1 stalk yield of pigeon pea compared to control (2.05 t seed ha^-1 and 10.75 t stalk ha^-1). Management of wilt of pigeon pea by soil application of fungicides is economically non-viable. Bio-control agent such as Trichoderma viride has the potential to replace or augment conventional plant disease management (Patel et al., 2011). Crop establishment on BBF have less water content, more porous and less humid (Agrawal and Goswami, 2003). Prasad et al., (2012) reported similar results for control of wilt of pigeon pea. The recommended technique of control of wilt of pigeon pea significantly increased the net returns and B:C ratio as compared to control plot. The additional net income was Rs. 9,401 ha^-1 with recommended technique compared with net income of control plot (Rs. 67,516 ha^-1). Like-wise significantly higher B:C ratio was recorded under recommended technique of wilt management (3.73) compared with control (3.47).
       
The energy output, energy use-efficiency, energy productivity and net energy gains were significantly higher in recommended technique of wilt management of pigeon pea compared to control plot (Table 3). The increase of energy output, energy use-efficiency, productivity and net energy gains with recommended technology were 4.0, 2.0, 9.9 and 4.1%, whereas specific energy for producing per kg biomass was 1.4% lower compared with control, respectively.
 
Bruchids management
 
Control of bruchids through spray of insecticide Trizophos 40 EC @ 1 lit. ha^-1  at maturity of pigeon pea, and after threshing sun drying of seed (moisture <6%) and application of fumigant aluminium phosphide 9 g tonne^-1  seed was saved and increase of economic benefits, energy outcomes as compared to control (not using any practice), whereas non-significant effect was found on stalk yield apparently as the pest attacked the seed only (Table 2). The average loss of seed yield by 23.6% without adopting any practice for control of bruchid was compared with recommended techniques. The recommended technique for control of bruchid was saved 0.55 t ha^-1 seed yield of pigeon pea over control (1.78 t ha^-1 seed). The use of recommended technique significantly increased net return and B:C ratio as compared to control. The additional net income was Rs. 17,524 ha^-1 under the recommended technique compared with net income of Rs. 55,656 ha^-1 under control. The B:C ratio (3.40) was significantly higher under recommended technique compared with control (2.96). Similar findings were also reported by Sharma et al., (2010).
       
The recommended technique for control of bruchids significantly increased energy output, use efficiency, energy productivity and net energy gains compared to control, whereas specific energy significantly decreased with recommended technique for control of bruchids (Table 3). The increases of energy output, use efficiency, energy productivity and net energy gain were 5.8, 2.5, 34.1 and 5.9%, respectively with recommended technique for control of bruchids, whereas specific energy use was required 3.2% lower compared with control.
 
Physicochemical properties
 
Organic carbon and infiltration rate increased significantly, whereas bulk density decreased significantly under weed and wilt management compared with control (Table 4). The values of bulk density was decreased 0.02 Mg m^-3 with weed and 0.05 Mg m^-3 with wilt management compared with control plots, whereas maximum increase of infiltration rate (+0.9 mm hr^-1) was obtained under weed followed by wilt (+0.7 mm hr^-1) management as compared to control.
 

       
The weed and wilt management also significantly affected the availability of N, P, K, S and Zn compared with existing farmers’ practice (control). The additions in availability of nutrients under weed and wilt management were 45 and 22 kg N ha^-1, 0.9 and 0.7 kg P ha^-1, 15 and 18 kg K ha^-1, 1.5 and 0.5 kg S ha^-1 and 0.2 and 0.4 mg Zn kg^-1 compared with values of control, respectively. Increase in available nutrients could be due to the fact that pigeon pea crop was capable of exploiting nutrients from deeper layers of soil through its deeper and extensive rooting system. Management of weed and wilt produced more biomass (root, stubble and shaded residue) recycling resulting in improvement of physicochemical properties of soil. Kumar and Goh (2002) reported that more crop residues and volume of roots of pigeon pea can contribute significantly to the build-up of soil organic matter and available nutrients.

Results on farmers’ participatory trials reveals that techniques of management of biotic stress significantly influenced on seed and stalk yield, net profit and B:C ratio as compared to existing practices of pigeon pea cultivation. Additional expenditure on production cost was recorded higher under management of weed followed by bruchid in field and storage, wilt and pod borer. Output, use-efficiency, productivity, net gains of energy were significantly influenced by biotic stress management over existing practices of pigeon pea cultivation. The management of weed and wilt also significantly improved the physicochemical properties of alluvial soil. Adoption of management of biotic stresses of pigeon pea was significant impact on seed yield, economic benefits, energy indices and overall improvement of physicochemical properties of soil.