Effect of Various Potassium Levels and Organic Sources on Soil Health and Nutrient Content of Cluster Bean under Semi-arid Eastern Plain Zone of Rajasthan, India

Abstract

With the advent of high-yielding crop varieties/hybrids and the gradual intensification of agriculture, soil potassium reserves are being depleted at a quicker rate. Furthermore, due to uneven fertiliser application, potassium deficit is becoming one of the most significant restrictions in crop productivity. A field experiment was conducted to study the influence of potassium and organic sources on soil properties and nutrient content of cluster bean (Cyamopsis tetragonoloba L.) during Kharif, 2024 at Instructional Farm, SKNAU, Jobner, Jaipur (Raj.). The study comprised treatments with different potassium levels Control, 100% RDK @ (20 kg K ha⁻¹) (SA), 75% RDK @ (15 kg ha⁻¹) (SA) + KSB (5ml/kg seed) (ST) + KSB (SA) (2.5L/ha), 50% RDK @ (10 kg K ha⁻¹) (SA) KSB (5ml/kg seed) (ST) + KSB (SA) (2.5L/ha) and KSB (5ml/kg seed) (ST) + KSB (SA) (2.5L/ha)) and organic sources Control, 100% RDFYM (FYM @ 5 t/ha), 100% RDV (Vermicompost @ 2.5 t/ha) and 50% RDFYM (FYM @ 2.5 t/ha) + 50% RDV (Vermicompost @ 1.25 t/ha) arranged in a factorial randomized block design with three replications and 20 treatment combinations. The results of the experiment revealed that potassium application had no significant effect on soil pH, EC, bulk density,  organic carbon, available nitrogen and phosphorus; however, available potassium improved significantly (218.72 kg ha⁻¹ under 100% RDK), however Treatment 75% RDK + KSB (217.90 kg ha⁻¹) was found statistically at par. Organic sources significantly improved soil organic carbon (0.269 % under FYM@ 5 t/ha), reduced bulk density (1.46 Mg m⁻³ under FYM @ 5 t/ha), and enhanced available N (152.04 kg ha⁻¹), P (23.15 kg ha⁻¹) and K (217.87 kg ha⁻¹) under vermicompost @ 2.5 t/ha. 100% RDFYM stimulated the highest microbial population and DHA (21.84 µg TPF g⁻¹), however, 50% RDFYM (FYM @ 2.5 t/ha) + 50% RDV (Vermicompost @ 1.25 t/ha) was found at par. Nutrient content in seed and straw was significantly influenced by potassium and organic sources. Maximum seed N (3.48%), K (0.516%) and straw N (0.72%), K (1.18%) occurred under 100% RDK, while Vermicompost @ 2.5 t/ha recorded highest seed N (3.49%), P (0.478%) and K (0.501%) content, however 50% RDFYM (FYM @ 2.5 t/ha) + 50% RDV (Vermicompost @ 1.25 t/ha) was found at par. The interactive effect K1O2 (100% RDK + vermicompost @ 2.5 t/ha) gave maximum seed N (3.60%) and K (0.552%) content, though K2O2 (75% RDK + KSB + vermicompost @ 2.5 t/ha) was found statistically at par with K1O2. It may be concluded that 75% RDK + KSB + vermicompost @ 2.5 t/ha not only saved 25% mineral K fertiliser but also sustained soil health and productivity, representing a sustainable nutrient management option for cluster bean in the semi-arid eastern plain zone of Rajasthan.