Impact of different levels of potash on growth yield and quality of pigeon pea (Cajanus cajan (L.) Huth)

Introduction

Pulse crops constitute an essential category of agronomic plants cultivated primarily for their protein-rich edible seeds, which are esteemed for their profound nutritional benefits to both human and animal diets. Exemplary members of this crop group encompass lentils, chickpeas, beans, peas, and soybeans. These leguminous species significantly bolster global agricultural systems by augmenting the availability of plant-derived proteins, thereby diversifying dietary regimes and fortifying global food security. Notably, pulses have been ascribed the moniker "poor man's meat" due to their indispensable role as a primary protein source for vegetarian populations worldwide. Pigeon pea is extensively cultivated across tropical and subtropical regions, with predominant consumption in South Asia, Southeast Asia, Africa, Latin America, and the Caribbean. Taxonomically classified within the Fabaceae family, it is indigenous to the Eastern Hemisphere. Potassium (K) is an indispensable macronutrient in plant physiology, playing a pivotal role in regulating stomatal dynamics, which govern gaseous exchange and transpiration water loss. Stomata serve as conduits through which leaves exchange carbon dioxide (CO 2 ), oxygen (O 2 ), and water vapor with the external atmosphere. When potassium ions accumulate within guard cells encircling the stomatal aperture, osmotic pressure ensues, leading to the influx of water, cellular turgidity, and stomatal opening, thereby facilitating efficient gas exchange. An inadequate potassium supply disrupts this regulatory mechanism, rendering stomatal function sluggish and inefficient, which exacerbates transpirational water loss. Closure of stomata, which ordinarily occurs within minutes under optimal potassium levels, is significantly delayed, leaving plants highly susceptible to desiccation and abiotic stress. Additionally, potassium accumulation in root tissues engenders an osmotic gradient that facilitates water uptake. Deficiency in potassium impairs this osmotic regulation, thereby diminishing root water absorption capacity and predisposing plants to drought susceptibility (Kumar et al., 2020) [4] . Consequently, potassium-deprived plants exhibit diminished biomass accumulation and retarded physiological development. Given its indispensable role in stomatal regulation, photosynthetic and optimization, potassium is a fundamental determinant for crop productivity and ecological adaptability.

Materials and Methods

This study aimed to explore how varying potassium levels influence the growth and yield of the pigeon pea variety UPAS 120. The research was conducted at the Student Research Farm within the Department of Agronomy at the School of Agriculture Science Technology and Research, Sardar Patel University, Balaghat, Madhya Pradesh, during the Kharif season of 2023.

The treatments were T 1 Control T 2 30:50:15 Kg NPK ha -1 T 3 30:50:20 Kg NPK ha -1 T 4 30:50:25 Kg NPK ha -1 T 5 30:50:30 Kg NPK ha -1 T 6 30:50:35 Kg NPK ha -1 T 7 30:50:40 Kg NPK ha -1 T 8 30:50:45 Kg NPK ha -1 The height of five randomly selected plants from each plot was measured from the ground level to the tip of the shoot, at 20, 40, and 60 days after sowing (DAS) while number of branches was recorded at 40 and 60 DAS. The total count of root nodules recorded at 35 DAS, following the uprooting of the plants. In addition the number of flowers, pods produced by each plant and count of seeds per pod was recorded. The seeds harvested from individual plots were combined and weighed to determine the seed yield per plot, categorized by treatment and replication, and subsequently analyzed. The weight of 1000 seeds was measured using a physical balance from seeds of five randomly selected plants for parameter observation, and the results were averaged and statistically analyzed. Harvest index was computed by using following formula as suggested by Singh and Stoskoff (1971) [5] . The harvest index was worked out by using following formula:

The statistical analysis was conducted using Fisher and Yates (1967).

Results and Discussion A) Growth parameters

The data depicted in Table 1 revealed that the statistically significant differences in plant height were observed among all the treatments at all recorded stages, i.e. at 20, 40, and 60 DAS, among the different combinations applied. The tallest plants measured 39.97 cm, 96.97 cm, and 140.68 cm at 20, 40, and 60 DAS, respectively, with treatment T 6 (30:50:35 Kg NPK ha -1 ) leading the results. Treatment T 7 (30:50:40 Kg NPK ha -1 ) followed closely, yielding heights of 37.32 cm, 91.76 cm, and 137.63 cm at the same intervals. In contrast, the control group (T [3] who worked to find out the effect of graded levels of potassium and micronutrients on yield, quality and nutrient uptake in Pigeon pea through soil and foliar and concluded that application of 100% NP + 50 kg K 2 O ha -1 + Grade-I improved plant height, branching in plants.

The maximum (table 1) number of root nodules per plant (22.51 nodules) was observed with treatment T 6 (30:50:35 Kg NPK ha - 1 ) followed by T 8 (30:50:45 Kg NPK ha -1 ) with 21.19 nodules. Minimum number of root nodules per plant (15.91 nodules) was observed in T 1 (Control). The application of 30:50:35 kg NPK ha -1 in pigeon pea enhances the number of root nodules per plant compared to other potassium doses due to the balanced nutrient availability, particularly the optimal potassium supply. Bagadkar et al., (2020) [1] investigated the effect of various potassium levels with addition of foliar spray of KCL (potassium chloride) on growth, yield and quality of greengram. Findings revealed that growth traits viz., plant height (cm), number of branches plant -1 , dry matter plant -1 (gm) and chlorophyll content index were found significantly superior in the treatment with application of RDF + 40 kg K 2 O ha -1 than rest of graded potassium level treatments.

B) Yield parameters Number of pods per plant, seeds per pod and seed yield per plant

Treatment T 6 (30:50:35 Kg NPK ha -1 ) achieved the highest pod count, totalling 220.67 pods, closely trailed by T 7 (30:50:40 Kg NPK ha -1 ) with 218.67 pods. In stark contrast, the control treatment T 1 produced the lowest pods 137.00 pods per plant (table 2). The greatest number of seeds per pod, recorded at 12.33 seeds per pod, was also found in treatment T 6 , closely followed by T 7 10.33 seeds per pod. The T 1 had the lowest seed count per pod, averaging just 5.33 seeds. Furthermore, the highest seed yield per plant was noted in treatment T 6 at 72.37 grams, with T 7 close behind at 68.59 grams. The control treatment T 1 yielded the least, at only 34.35 grams per plant. The application of 30:50:35 kg NPK ha⁻¹ in pigeon pea leads to better pod development, higher seed count per pod, and increased seed yield per plant due to the balanced supply of essential nutrients, particularly potassium. Kumar et al. (2020) [4] studied the effect of integrated nutrient management for sustaining the productivity of pigeon pea concluded the same.

Test weight and seed yield per plot

The highest seed yield (table 2) recorded per plot was an impressive 2.50 kg, achieved with treatment T 6 (30:50:35 Kg NPK ha -1 ), closely followed by T 7 (30:50:40 Kg NPK ha -1 ), which yielded 2.41 kg. In contrast, the lowest seed yield of 1.27 kg was noted in the control plot (T 1) . Furthermore, the maximum test weight reached an elegant 9.60 grams with treatment T 6 , while T 7 followed closely with a weight of 9.55 grams. The control plot (T 1) exhibited the minimum test weight of 7.36 grams. The application of 30:50:35 kg NPK per hectare in pigeon pea cultivation significantly enhances test weight and elevates seed yield per plot, owing to the meticulously balanced provision of vital nutrients, with potassium being particularly noteworthy.

Seed yield, Stover yield and harvest index

The highest seed yield recorded per hectare (table 2) was 20.12 q/ha, achieved with treatment T 6 (30:50:35 Kg NPK ha -1 ), closely followed by T 7 (30:50:40 Kg NPK ha -1 ) which yielded 19.42 q/ha. In contrast, the lowest seed yield of 14.19 q/ha was observed in the control plot (T 1) . When it comes to Stover yield, treatment T 6 also led the way with an impressive 50.37 q/ha, while T 7 trailed just behind at 48.67 q/ha. The control plot (T 1) recorded the least Stover yield at 36.11 q/ha. As for the harvest index (table 2), the peak was 41.83% with treatment T 6 (30:50:35 Kg NPK ha -1 ), which was nearly equal to T 3 (30:50:20 Kg NPK ha -1 ) that achieved 40.77%. The control plot (T 1) had the lowest Harvest index at 39.35%. The application of 30:50:35 kg NPK ha -1 in pigeon pea results in better seed and stover yield per hectare due to the optimal balance of essential nutrients, particularly potassium, which plays a key role in enhancing both vegetative and reproductive growth. Singh and Debbarma (2023) [5] conducted research in randomized block design consisting of 10 treatments with 3 different levels of phosphorus 40 kg/ha, 50 kg/ha, 60 kg/ha and different levels of potassium 25, 30 and 35 with three replications and the treatments were allocated randomly in each replication in pigeon pea and concluded the same better test weight, yield and harvest index

C) Economics parameters

Maximum cost of cultivation incurred in treatment T 8 (30:50:45 Kg NPK ha -1 ) with (Rs 34582 ha -1 ) and the minimum (Rs 33382 ha -1 ) was recorded in treatment T 1 (Control). Maximum gross returns were recorded in treatment T 6 (30:50:35 Kg NPK ha -1 ) with (Rs 1,55,951 ha -1 ) followed by T 7 (30:50:40 Kg NPK ha -1 ) having Rs 1,50,519 ha -1 and the minimum (Rs 1,10,139 ha -1 ) was recorded in treatment T 1 (Control). Maximum net returns were recorded in treatment T 6 (30:50:35 Kg NPK ha -1 ) with (Rs 1,21,636 ha -1 ) followed by T 7 (30:50:45 Kg NPK ha -1 ) having Rs 1,16,070 ha -1 and the minimum (Rs 76,757 ha

Conclusion

The overall results obtained from this present investigation clearly revealed that the application of T 6 (30:50:35 Kg NPK ha - 1 ) showed the better performance for vegetative growth viz., plant height (140.68 cm), number of branches per plant (21.22 branches), yield attributes like number of pods per plant (226.67 pods), pod yield (20.12 q/ha) and harvest index (41.83%) of Pigeon pea. T 6 also recorded highest net return and benefit cost

Acknowledgement

ratio. Thus, use of potassium at higher dose may be suggested for higher crop productivity along with over all betterment of pigeon pea under Balaghat (M.P.) conditions.

References

1. Bagadkar A, Hiwale S, Darekar N. Effect of graded levels of potassium on growth, yield, and economics of greengram. J Pharmacogn Phytochem. 2020;9(4):17991801.
2. Bharati M, Dwarka. Study the effect of potassium levels on pigeon pea (Cajanus cajan L.) yield attributing characters. Pharma Innov J. 2023;12(11):455-457.
3. Chavan SU, Deshmukh MS, Kachave TR. Effect of graded levels of potassium and micronutrients on yield, quality, and nutrient uptake in pigeon pea through soil and foliar application under Vertisols. J Pharmacogn Phytochem. 2020;9(1):1468-1470.
4. Kumar S, Singh RN, Kumar S, Kumar P. Effect of integrated nutrient management on growth and yield of pigeon pea (Cajanus cajan) in changing climatic condition of Bihar. Legume Res. 2020;43(3):436-439.
5. Singh KK, Debbarma V. Effect of phosphorus and potassium on growth and yield of red gram. Int J Environ Clim Change. 2023;13(10):2756-2763.