Pigeonpea (Cajanus cajan L.) Growth, Yield and Monetary Influence by Drip Irrigation and Mulch in Vertisols of Madhya Pradesh

Pigeonpea (Cajanus cajan L.) is commonly known as tur or arhar in India. Pigeonpea is a perennial member of the Fabaceae family and one of the major legume crop of the tropics and subtropics (Vanaja et al., 2010). Pulses are proved as unique jewels of Indian farming. Pulses are an integral part of Indian diets as well as worldwide. It have great potential to improve human health, conserve soils, protect the environment and contribute to global food security. The United Nations, declared 2016 as “International Year of Pulses”. India has first position as producer, consumer and importer of the pulses in the world. Pigeonpea is particularly rich in lysine, riboflavin, thiamine, niacin and iron (Manikandan and Sivasubramaniam, 2015). Pigeonpea plays an important role in food security, balanced diet and the alleviation of poverty.
       
Pigeonpea is grown worldwide in an area of 4.24 mha, with a production of 4.67 MT and productivity of 750 kg/ha. Rain fed pigeon pea has more than 85% area (Sanjay et al., 2017). In India, it occupies an area of 3.75 mha with a production of 2.78 MT and a productivity of 750 kg/ha (GOI Report, 2015). Annual Report 2017-18 of IIPR Kanpur showed that per capita availability of pulses are reducing as population is increasing that resulted in reduced availability to the masses. India’s population is expected to touch 1.68 billion by 2030 and the pulse requirement for the year 2030 is projected at 32 MT (Sarkar et al., 2020).
       
Vertisols is the soil known for its shrinking and swelling properties. When the moisture content decreases the soil shrinks and creates the deep cracks in the soil surface. In such soil when water applied it gets swelled. These soils have drainage problems (Shrivastava et al., 2018). Willey et al., (1981) studied the problems and technology required for higher pulse production in such soils. Season and soil critically affect the water demand and other cultural practices of pigeonpea cultivation (Manikandan and Sivasubramanyam, 2015).
       
The demand for fresh water has been on the rise from all water user sectors. Agriculture is the biggest user of water and consuming about more than 70% of water utilization. As of now irrigation sector consumes about 83% of the total water use which may reduce to about 72% by 2025 in India (MoWR, 2014).  Thus, producing more with less is the only option. Emphasize must be on the need for water conservation and improvement in water use efficiency to achieve ‘more crop per drop’ of water. Among the various techniques advocated for economizing water use, scheduling of irrigation based on IW/CPE ratio is considered most effective and important (Gajera and Ahlawat, 2006).
       
Unavailability of water on a continuous basis is a serious hurdle to maximize pigeonpea yields (Reddy and Virmani, 1980). Water stress affects the final yield due to the reduction in growth attributes i.e. plant height, number of pods, reduction in pod weight. Roder et al., 1998 and Sharma et al., (2012) reported that more than 50% of yield loss in pigeon-pea is due to drought. The plant’s physiological processes get affected because of moisture stress in plant (Patel et al., 2001). Proper use of existing water resources by using suitable irrigation technologies to increase pigeonpea production per unit area is the need of the hour (Jeyjothi et al., 2017). Swathi et al., (2018) reported that the congenial environmental conditions determine the growth and flowering behavior of pigeon pea.
       
Drip and mulching can be a way to achieve the goal of more crop per drop (Pawar and Khanna, 2018). Importance of water requirement in kharif crop for Malwa region is also advocated by Ranade et al., (2021). Pigeonpea yield increased tremendously when irrigated through drip method. Greater attention is now needed to manage the pigeonpea because of high remunerative price. Moisture conservation techniques can enhance production and productivity of the crop. Solanki et al., (2019) indicated that drip and mulching have great influence on the productivity of pigeonpea. Vision 2050 of IIPR (ICAR) also emphasized on resource conservation techniques in pulses viz., raised bed planting, drip irrigation and mulching to minimize water loss and enhance water productivity. Tiwari et al., (2012) and Gireesh et al., (2019) studied the yield gap, constraints and economics of pigeonpea production in Madhya Pradesh. Farmers are facing many constraints related with pigeonpea cultivation therefore proper resources management and scientific practices can increase the production and productivity of pigeonpea.

The study area is located (23°16¢48² N-latitude, 77°21¢36² E-longitude) in Madhya Pradesh which is under Vindhyan plateau as an agro-climatic zone. The field experiments were conducted in a village of Sehore district of Vindhyan plateau during year 2016-17 and 2017-18. This area belongs to sub-tropical climate with mean temperature range of min. 7°C in winter and max. 43°C in summer. The experimental site soil is vertisols with uniform and leveled topography.
       
Well treated bold seeds of pigeonpea (TJT-501) were dibbed in soil on ridge-furrow land configuration. Hand dibbling @ two seeds per hill was performed at about 6 cm depth. Row to row and plant to plant distance were kept 60cm and 25cm respectively. Drip irrigation system was used to irrigate pigeonpea having main (75 mm) and sub main (63 mm) of PVC pipes. LDPE pipes of 16 mm diameter were used as lateral, keeping lateral spacing of 60 cm with inline emitters. Control valve and pressure gauge were used to regulate the pressure of 1.2 kg/cm² to get the desired discharge rate as per treatment requirement. A 7.5 HP submersible pump was installed in tube well and connected to main line for irrigation water supply. Lateral lock was provided to each lateral for delivering desired quantity of water as per treatment. A screen filter was fitted in the system to avoid chocking due to impurities in the water. Laterals were put along the row soon after sowing of seeds.  Black plastic sheet of 25 micron and wheat straw @ 5 t/ha were used as mulch. Irrigation water was applied according to daily crop evapotranspiration of pigeonpea. Daily evaporation (mm) was recorded for the two growing seasons from USWB class ‘A’ pan evaporimeter situated at experimental field.
       
Crop evapotranspiration was calculated by using following relationship.
  Where,
ETc = Crop evapotranspiration (mm).
PE = Pan evaporation (mm).
Pf = Pan fraction (0.8).
Kc = Crop coefficient.
 
Amount of water to be applied per treatment was calculated as follows:  
  Where,
V = Volume of irrigation water (lit/day/emitter).
ETc = Crop evapotranspiration (mm).
S_l = Spacing between laterals (m).
Sd = Spacing between drippers (m).
       
The experiment was laid out with twenty seven treatment combinations consisting of three mulching, three discharge rate (2 lph-D₁, 4 lph-D₂ and 8 lph-D₃) and three irrigation levels viz. 60% CPE (I₁), 80% CPE (I₂) and 100% CPE (I₃).

The treatment wise B:C ratio were calculated by using following equations.
   
       
The recorded data were statistically analyzed by using technique of analysis of variance for the split plot design given by Gomez and Gomez (1984). The critical difference (C.D.) at 5% level of significance and standard error of mean (S.Em) was worked out for treatment comparison where the F-test revealed the significant effect.

The results on the basis of pooled data showed that the crop growth and yield attributes of pigeonpea were significantly affected by different treatments. Table 1 indicated that the maximum plant height was obtained in black plastic mulch and lowest in without mulch (161.99 cm) which has significantly difference of 11.91%. The maximum plant height was recorded in I₂ (176.10 cm) which is at par in I₃ (174.16 cm). The significantly lowest height was registered in I₁ (166.22 cm). The similar result was reported by Savani et al., (2017) and Jadhav et al., (2018). The increased plant height might be due to better availability of moisture and nutrients near root zone during entire crop growth period which favoured the growth attributes. Almost similar trend was observed by Ghosh and Biswas (1984) and Solanki et al., (2019). The pooled data (Table 1) clearly indicate that the plant height was highest with 2 lph (D₁) and value recorded with D₂ is at par with D₃ (8 lph). Among different discharges evaluated, significantly highest was observed with D₁ (175.78 cm) followed by D₂ (171.28 cm) and D₃ (169.42 cm). The results are similar with Pragna et al., (2016). It might be due to soil moisture variation in vertisols with different discharge rate. In such soil, water is absorbed very slowly and runoff can possible if water is applied with higher discharge rate (Kareem et al., 2013).
 

       
Increasing the rate of discharge allows more water to move in horizontal direction, while decreasing the rate allows more water to move in vertical direction (Badr et al., 2003) and Kumar et al., (2018). Lower discharge rate gave better result than upper as reported in Table 1. The irrigation treatment significantly affects the number of branches and maximum recorded in I₂ (13.10) which is at par with I₃ (11.64). The increased number of branches per plant might be due to better availability of moisture and nutrients during entire crop growth period which favoured the growth attributes. Also, drip irrigation treatment created better micro-climate as compared because of prolonged duration of watering. The above findings are in close conformity with the findings of Yadav et al., (2006) and Savani et al., (2017) who found the same trend in dry matter accumulation. Table 1 also indicated that the maximum value of growth attributes were obtained in black plastic mulch and lowest in without mulch which has significantly difference.
       
The pooled data (Table 2) revealed that lowest value of pods per plant recorded with I₁ (106.45) and highest with I₂ (113.19) which is at par with I₃ (111.97). These results are conformity with Jadhav et al., (2018). Maximum number of pods registered with D₁ (113.62) followed by D₂ (110.05) and D₃ (107.94). Goldberg et al., (1970) reported that water movement from drip source is a function of soil type and dripper discharge together. Soil moisture variation affects the number of pods per plant. The different discharge rate did not significantly influence test weight. The highest test weight was recorded with D₁ (9.93) followed by D₂ (9.81) and D₃ (9.78) as given in Table 2. The test weight variation due to different irrigation levels found significant. On the pooled data basis, it is clear that lowest weight was recorded with I₁ (9.61) and highest with I₂ (9.96) which is at par with I₃ (9.94). The number of seeds per pod was significantly influenced by different discharge rate. The pooled data clearly indicate that was significantly difference among these. Maximum number of seeds registered with D₁ (3.41) followed by D₂ (3.25) and D₃ (3.20). The pooled data also indicate that lowest value recorded with I₁ (3.21) and highest with I₂ (3.33) which is at par with I₃ (3.32) as illustrated in Table 2. Increasing the soil moisture storage through irrigation significantly improved yield attributes. The similar results were reported by Patel and Patel (1994) and Venugopal and Rao (1999). Table 2 also indicated that the maximum values of yield attributes were obtained in black plastic mulch and lowest in without mulch which has significantly difference.
 

       
The data on results revealed that seed yield under different mulching treatments significantly affected (Table 3 and Fig 1). The pooled data revealed that significantly maximum seed yield (17.51 q/ha) registered under M₂ followed by M₁ (16.51 q/ha) and M₀ (11.83 q/ha). Savani et al., (2017) reported 48 % higher yield under plastic mulch than no mulch. Rao et al., (2018) reported that plastic mulch is far better than without mulch. Contrary result reported by Solanki et al., (2019) that higher yield in organic mulch than in plastic mulch. Maximum yield registered with D₁ (16.48 q/ha) followed by D₂ (14.91 q/ha) and D₃ (14.46 q/ha). Increasing the soil moisture storage through irrigation significantly improved yield attributes. The seed yield was found significant due to effect of different irrigation levels. The pooled data clear that lowest value recorded with I₁ (14.07 q/ha) and highest with I₂ (16.01 q/ha) which is at par with I₃ (15.77 q/ha). These results are conformity with Jadhav et al., (2018). Improvement in yield might be due to better proportion of air-soil-water which was maintained throughout the crop life in drip irrigation.
 

 

       
The significant difference recorded in net return influenced by different mulching treatments (Table 3). The significant variation observed in net return due to effect of different irrigation levels. The pooled data revealed that lowest return recorded with I₁ (Rs.44864) and highest with I₂ (Rs.55726) which is at par with I₃ (Rs.54189). These findings are conformity with Jadhav et al., (2018). Different discharge rate significantly influences the net return. On the basis of pooled data, it is clear that maximum return registered with D₁ (Rs.58504) followed by D₂ (Rs.49473) and D₃ (Rs.46802).
       
It is apparent from the data (Table 3 and Fig 2) on B:C ratio indicated that different irrigation level significantly influenced this monetary parameter. The pooled data indicate that lowest value (1.26) of it recorded with 60% IW/CPE whereas highest B:C (1.56) registered with 80% IW/CPE which is at par with 100% IW/CPE (1.52). Higher seed yields under irrigation (I₂) through drip compensated the cost incurred on installation of drip. Similar results were reported by Pramod et al., (2010) and Jadhav et al., (2018). These findings are in agreement with those of Mathukia et al., (2015). Savani et al., (2017) also reported that irrigation at 0.8 PEF with organic mulch gave better results due to higher cost of plastic sheet, it was not economical for mulching in pigeonpea crop. Different discharge rate significantly influences the B:C. On the basis of pooled data, it is clear that highest B:C registered with D₁ (1.64) followed by D₂ (1.38) and D₃ (1.31).
 

On the basis of results obtained in present study, the drip irrigation as per crop evapotranspiration demand at 80% CPE gave the best performance than lower (60%) and upper (100%) level. Mulch influenced the growth and yield attributes and finally higher B:C recorded because of soil moisture conservation and gave better result. In vertisols, lower discharge rate gave better results than higher rate.  It can be concluded that irrigation at 0.8 PEF with organic mulch gave better results and due to higher cost of plastic sheet, it was not economical with 100% supply of irrigation during kharif. It is viable to supply irrigation as per CPE only at branching, flowering and pod development stages of pigeonpea crop in vertisols of Madhya Pradesh.