Effect of Different Tillage, Nutrient Management Practices and Foliar Application of KNO₃ and Borax on Yield Attributes and Yield of Pigeonpea [Cajanus cajan (L.)]

Pulses form an important part for nutritional security, sustainable crop production and occupy a unique position in Indian agriculture, besides being rich source of protein, they maintain soil fertility through biological nitrogen fixation in soil and thus play a vital role in sustainable agriculture (Balusamy and Meyyazhagan, 2000). Pigeonpea has special morphological characters with respect to deep rooting and drought tolerance that have made adaptable for growing in wide range of unfavourable conditions with uncertain rainfall and varied soil depth. It is the second most important pulse crop of India, which occupies an area of 4.82 million hectares with production of 3.88 million tonnes and average productivity of 804 kg ha^-1. In Andhra Pradesh, pigeonpea is grown under rainfed conditions to an extent of 2.23 lakh hectares with an annual production of 1.16 lakh tonnes and productivity of 486 kg ha^-1 (Directorate of Economics and Statistics, Govt. of A.P, 2019-20).
       
The lower productivity of pigeonpea is not only due to its cultivation in sub marginal lands under  energy starving situations, low fertility and inadequate fertilizer applications, but also due to its high elasticity, indeterminate growth habit, poor source-sink relationship, poor translocation efficiency at later stages of crop growth, flower dropping and subsoil compaction that leads to restricted water infiltration, there by bringing many chemical and biological changes which affect the plant growth and regular depletion of nutrient resources of soils has led to emergence of several nutrient deficiencies (Ware et al., 2018). Among them soil tillage coupled with balanced fertilizer application and foliar nutrition are the key factors determining the yield.
 
Tillage and fertilizer management play essential roles in both the nutrient and soil moisture dynamics of soil-plant systems. The effect of tillage on the soil physical properties are often soil and site specific and they depend primarily on the cropping system, antecedent soil characteristics and available clay minerals. Studies conducted in several plants showed that vertical tillage with subsoiler could improve the soil physical properties, particularly the infiltration, bulk density, water retention, structure and aggregate stability. Subsoil tillage is one of the most effective ways to break up a plough pan, loosening the soil and deepening the topsoil without inverting it and increasing soil permeability. It can also play an important role in promoting water storage in the soil, adjusting the proportion of solid, liquid and gas of soil, improving the structure and characteristics of topsoil and improving the ecological environment for root development and root activities that enhance the anti-stress capacity of plants (Cai et al., 2014, Priya, 2017 and Ramana et al., 2015).
       
As such, there is immense scope for augmenting its yield through balanced application of nutrients. There is a need to study whether there is any scope for improving its productivity with higher rates of nutrient application. Hence, its performance has been tested at three levels of nitrogen, phosphorus and potassium application in the present investigation.
       
Among the methods of fertilizer application, foliar nutrition is recognized as an important one, since foliar nutrients usually penetrate the leaf cuticle or stomata and enters the cells facilitating easy, rapid utilization and supplying nutrient instantly to crop. The prominent effect of foliar application of nutrients at 50 per cent flowering stage was exert important consequence on physiological processes in plants like ion transport, translocation of carbohydrates, proteins and their storage during seed formation and reduction in flower shed and flower drop percentage (Sarkar et al., 2006).
               
Pigeonpea responses to tillage, nutrients and foliar application of nutrients reportedly vary considerably, depending on soil, weather and various other factors. To this end, this study was conducted to evaluate and identify efficient tillage, fertilizer management practices and foliar sprays to attain sustainable yields.

A field experiment was conducted at S.V. Agricultural College, Tirupati campus of Acharya N.G. Ranga Agricultural University andhra Pradesh during two consecutive kharif seasons of 2019-20 and 2020-21 to study the effect of different tillage, nutrient management practices and foliar application of KNO₃ and borax on yield attributes and yield of pigeonpea [Cajanus cajan (L.)]. The soil of the experimental field was sandy loam in texture, low in available N, medium in available P and available K. Pigeonpea variety LRG -52 was used for experimentation. The experiment was laid in split-split design with three tillage practices (T₁: Conventional tillage with tractor drawn cultivator, T₂: Ploughing with duck foot cultivator upto a depth of 30 cm and T₃: Vertical tillage with subsoiler upto 60 cm deep at 1.0 m interval) in main plots, three nutrient levels (N₁: 75% RDF, N₂: 100% RDF (20-50-00 kg ha^-1) and N₃: 125% RDF) in subplots and three foliar sprays (F₁: Control (No spray) F₂: Borax 0.1%  F₃: KNO₃  1%) in sub-sub plots. Three nutrient levels were applied to sub plots as per the prescribed treatments assigned. Entire quantities of N, P₂O₅ and K₂O were applied by placement method at the time of sowing and first foliar spray of Borax 0.1% and KNO₃ 1% was done at 50 per cent flowering stage and second spray at 15 days after the first spray.

Yield attributes
 
The results obtained from present study showed significant variation in yield attributes of pigeonpea among different tillage, nutrient management practices and foliar sprays.
       
The highest number of pod bearing branches plant^-1, number of pods branch^-1 and   plant^-1 with T₃ which was significantly higher than the T₂ and T₁ which recorded the lower number of pod bearing branches, number of pods branch^-1 and plant^-1 in the order of descent during both the years (Table 1).
 

       
More number yield attributes was observed in T₃ due to better translocation of photosynthates from source to developing pods on account of overall improvement in vegetative growth which favourably influenced the flowering and fruiting in pigeonpea grown under vertical tillage (Table 2). In addition, the favourable soil conditions viz., more availability of nutrients and moisture was recorded with T₃ tillage practices. The results supported the findings of Ramana et al., (2015), Mathukia et al., (2015) and Priya (2017), Wang et al., (2019), Liang et al., (2019) and Preetham et al., (2020). The lower number of yield parameters were registered with T₁ due to late flowering coupled with poor availability of nutrients and moisture (Ramana et al., 2015 and Priya 2017).
 

       
Among the nutrient doses, maximum number of pod bearing branches plant^-1, number pods branch^-1 and plant^-1 was recorded with N3 which was significantly superior to N₂ and N₁ (Table 1). The highest number of yield attributes can be attributed to an adequate and continuous availability of nutrients to plants which resulted in better partitioning of photosynthates and synchronized early flowering which facilitated for producing more number of these parameters. These results are in accordance with the findings of Nagamani (2015), Das et al., (2016), Dalai et al., (2018), Beniwal and Tomer, (2019) and Divyavani et al., (2020). The lowest number of these parameters were recorded in T₁ due to late flowering coupled with poor availability of nutrients and moisture (Priya 2017 and Ramana et al., 2015).
       
Among foliar applications, F₃ resulted in higher number of pod bearing branches plant^-1, pods branch^-1 and plant^-1 which was however comparable with F₂ and significantly superior to F₁ during both the years of study (Table 1). The better performance of foliar spray applications might be due to meeting the nutrient demand of the crop at the critical stage by providing nitrogen and potassium which delays the synthesis of abscisic acid, promotes cytokinin activity causes high chlorophyll retention, photosynthetic activity in effective leaves for supply of current photosynthates from source to sink over longer period to plants and alters physiological and biochemical aspects enhances plant vigour and strengthens the stalk, further it has synergistic effect with phosphorus that resulted in more number yield attributes. Similar results were reported by Hiwale, (2015) and Jadhav et al., (2019).
       
Among the different tillage practices tried, maximum number of seeds pod^-1 and hundred seed weight was registered with T₃ followed by T₂ and T₁ in the order of descent, during both the years (Table 2).  Maximum number of seed pod^-1 and hundred seed weight might be due to better channelization of more photosynthates from vegetative parts to developing seeds resulting in complete filling of the pods. The activities of key nitrogen metabolism, enzymes and intermediate products of nitrogen assimilation were significantly higher by subsoiling than the duck foot tillage and conventional tillage methods. Subsoiling tillage had a higher translocation and absorption of N after flowering from vegetative organs to pods increasing the number of seeds pod^-1 and higher hundred seed weight by subsoiling producing bigger sized seeds. Similar results were in accordance with findings of Cai et al., (2014), Mathukia et al., (2014) and Liang et al., (2019).
       
Increase in the nutrient dose significantly increased the number of seeds pod^-1 during both the years of study. N₃ recorded significantly higher number of seeds pod^-1 of pigeonpea which was significantly superior to N₂ and N₁. The latter two treatments were comparable with each other. The highest number of seeds pod^-1 and hundred seed weight which can be attributed to availability of balanced nutrients, which led to better translocation of assimilates to produce more number of seeds pod^-1 and larger sized seeds that ultimately resulted in higher test weight and efficient utilization of growth resources. Number of seeds pod^-1 was reduced with decreased fertilizer dose due to severe competition for growth resources and poor translocation of photosynthates from pod walls and other vegetative plant parts to developing pods. Similar results were also reported by Sharma et al., (2013) and Reddy et al., (2011). The lowest number of seeds pod^-1 was observed with 75% RDF (N₁) due to poor source-sink relations.
 
       
Foliar application (F₃) registered maximum number of seeds pod^-1 and hundred seed weight which was significantly superior to F₂ and F₁. The difference between latter two treatments was also significant.
       
Maximum number of seeds pod^-1 and hundred seed weight (Table 2) was recorded with F₃ due to the higher availability of nutrients that was supplied through foliar feeding of KNO₃ which enhanced the number of floral buds, prevented the floral shedding and activate the biochemical functions in plants, enzyme activation, photosynthesis, cell division and translocation of photosynthates from source to sink that resulted in larger pod filling period leading to greater number of seeds pod^-1. Similar results were also reported earlier by Keerthi et al., (2015), Gorakshnath et al., (2016) and Vijayakumar et al., (2019). Control (No spray) (F₁) recorded lower number of seeds pod^-1 due to poor partitioning efficiency of photosynthates from source to sink.
 
Yield
         
Higher seed yield of pigeonpea due to vertical tillage with subsoiler can be attributed to an improving soil environment by favorable soil physical conditions such as changes in soil bulk density, penetration resistance, moisture content, root proliferation, available N reserves and increase in the quantum of nutrient absorption due to better root development, improving nitrogen accumulation and translocation, amount of N mobilization in stem and sheath reflected in better development and expression of growth and yield components, better portioning of photosynthates to developing pods which inturn resulted in higher seed. Similar findings were reported by Priya et al., (2017), Feng et al., (2018) and Liang et al., (2019). Lower seed yield due to conventional tillage practice was attributed to compacted layer that was not loosened, the rooting of pigeonpea was shallower resulting in lower moisture and nutrient uptake and a more rapid depletion of moisture in the rooting zone. These results are in agreement with findings of those Jordan et al., (2008) and Barbosa et al., (1989).
       
Successive increase in fertilizer dose from 75% RDF to 125% RDF progressively increased the seed yield of pigeonpea with significant disparity among one another. N₃ recorded significantly highest seed yield followed by N₂ and N₁ in the order of descent (Table 2).
       
The highest seed yield was due to with higher nutrient dose increased supply of nutrients which inturn increased the multi role activities in plant and soil, rate of symbiotic N fixation, energy transformation and metabolic processes which resulted in maximum growth parameters, yield attributing characters and higher rate of photosynthesis that helped in the greater accumulation of carbohydrates, protein and their translocation to the reproductive organs which inturn resulted in greater translocation of photosynthates towards the sink development. The results are in close agreements with those of Singh et al., (2016), Ware et al., (2018), Nagamani et al., (2020), Tekule et al., (2020) and Ghule et al., (2021).
       
Maximum seed yield of pigeonpea was recorded with F₃ followed by F₂ and F₁ in the order of descent, with significant disparity between any two of the three foliar sprays tested.
               
Highest seed yield with foliar application of KNO₃  might be due to better transport of assimilates thereby better balanced supply with cation and anions of potassium, nitrate nitrogen respectively enhancing the each other nutrient availability at critical stages that could have induced more flowering, reduction in flower shedding, delayed the synthesis of abscisic acid and promoted cytokinin activity, activation of enzymes responsible for carbohydrates redistribution and increased transportation of photosynthates from source to sink and in later stages, more assimilates are produced than used in growth and development, excess assimilates are diverted to storage compounds resulting increased seed yield of pigeonpea. These results are in accordance with findings of Sarkar et al., (2001), Shrikanth, (2008) and Tripathy et al., (2018), Vijayakumar et al., (2019), Laishram et al., (2020) and Ghule et al., (2021).

From the present investigation it can be concluded that vertical tillage with subsoiler upto 60 cm deep at 1 m interval (T₃) with application of 125% RDF (N₃) and foliar application of KNO₃-1% (F₃) twice at 50 per cent flowering stage of pigeonpea at 15 days interval resulted in better yield attributes and seed yield of pigeonpea.