Production technology of grain sorghum (Sorghum bicolor L. Moench) in summer rice fallows

Abstract

The study entitled “Production technology of grain sorghum (Sorghum bicolor L. Moench) in summer rice fallows” was undertaken at College of Agriculture, Vellayani, during 2022-2024. The objective was to standardize the tillage, plant population and nutrient management for grain sorghum in summer rice fallows. The field experiment was carried out at Instructional Farm, Vellayani, from January to May 2024. The experiment was laid out in design RCBD with 2 x 2 x 3 treatments, replicated thrice. The treatments comprised combinations of two tillage methods (t1-zero tillage, t2-conventional tillage), two levels of spacing (p1 – 45 x 15 cm, p2- 60 x 15 cm) and three levels of NPK (n1 – 45:25:25 NPK kg ha-1, n2 – 50:25:75 NPK kg ha-1 and n3 – 50:25:50 NPK kg ha-1). The variety used for the study was CO-32. Sorghum grown under conventional tillage (t2) resulted in taller plants, higher Leaf area index (LAI) at 30 DAS and higher number of leaves at 60 DAS and at harvest. Sorghum grown with a spacing of 60 x 15 cm (p2) recorded higher number of leaves at all stages of growth. Sorghum grown with a spacing of 45 x 15 cm (p1) recorded higher LAI at all stages of growth. With respect to nutrient management n2 (50:25:75 NPK kg ha-1) recorded taller plants at 90 DAS and at harvest, higher number of leaves at 90 DAS and higher LAI at 30 and 90 DAS. Sorghum grown under conventional tillage with spacing 45 x 15 cm and a nutrient dose of 50:25:75 NPK kg ha-1 (t2p1n2) resulted in taller plants at harvest (288.03 cm) which was at par with t2p1n3. Sorghum grown under conventional tillage with spacing 45 x 15 cm and a nutrient dose of 50:25:75 NPK kg ha-1 (t2p1n3) recorded higher LAI at 30 DAS (3.13) which was at par with t2p1n2. Sorghum grown under conventional tillage (t2) recorded higher Crop growth rate (CGR) and Relative growth rate (RGR) at 30-60 DAS interval and higher dry matter production (DMP) at 30 and 60 DAS whereas sorghum grown under zero tillage (t1) recorded higher CGR and RGR at 60-90 DAS interval and DMP at 90 DAS and at harvest. Higher CGR, RGR and DMP were estimated in sorghum grown with a spacing of 45 x 15 cm (p1) at all stages of growth. With respect to nutrient management treatments, n2 (50:25:75 NPK kg ha-1) resulted in higher CGR, RGR and DMP and was statistically comparable with n3 (50:25:50 NPK kg ha-1). The lowest number of days for 50 percent flowering (64.08 days) was recorded in the treatment n2 (50:25:75 NPK kg ha-1). Among yield attributes, sorghum grown under zero tillage with spacing 45 x 15 cm and a nutrient dose of 50:25:50 NPK kg ha-1 (t1p1n3) resulted in higher length of panicle (22.70 cm), number of grains per panicle (1836.67) and grain weight per panicle (35.96 g). Higher grain yield (5.14 t ha-1) was obtained in treatment t1p1n3, which was found on par with t1p1n2 (4.96 t ha-1) and higher stover yield (8.10 t ha-1) was obtained in treatment t1p1n2 which was found on par with t1p1n3 (7.81 t ha-1). Harvest index was higher in the treatment t2p2n1 (0.43) and remained comparable with t1p1n3 (0.40) and t1p1n2 (0.39). Sorghum grown under zero tillage recorded higher chlorophyll content (3.50 mg g -1 and 3.86 mg g -1) at 30 DAS and 60 DAS respectively and in case of nutrient application treatment n3 (50:25:50 NPK kg ha-1) recorded higher chlorophyll content and was at par with n2 (50:25:75 NPK kg ha-1) at 30 DAS and n2 (50:25:75 NPK kg ha 1) recorded higher chlorophyll content at 60 DAS. The N uptake of sorghum was higher (258.36 kg ha-1) when grown under zero tillage with spacing 45 x 15 cm and a nutrient dose of 50:25:75 NPK kg ha-1 (t1p1n2) and was found on par with t1p1n3 (242.47 kg ha-1). The uptake of P was found higher (67.38 kg ha-1) in treatment t1p1n3. The uptake of K was higher (379.57 kg ha-1) in treatment t1p1n3 which was on par with t1p1n2 (339.64 kg ha-1). Post-experiment soil analysis revealed that sorghum grown under conventional tillage resulted in higher pH (6.93) and electrical conductivity (0.54 dS m-1). With respect to nutrient management treatment n3 (50:25:50 NPK kg ha-1) recorded higher pH and electrical conductivity. Sorghum under zero tillage (t1) recorded the highest organic carbon content (1.44 %) and in case of nutrient management treatment n2 (50:25:75 NPK kg ha-1) recorded higher organic carbon content which was on par with n3 (50:25:50 NPK kg ha-1). The available N (205.86 kg ha-1), available P (88.24 kg ha 1 ) and available K (93.33 kg ha-1) status of soil was higher under zero tillage (t1). Sorghum grown with a spacing 60 x 15 cm recorded higher available N, available P and available K. In case of nutrient management treatments n3 (50:25:50 NPK kg ha-1) recorded higher available N and n1 (45:25:25 NPK kg ha-1) resulted in higher available P. The treatment n2 (50:25:75 NPK kg ha-1) recorded higher available K which was found on par with n3 (50:25:50 NPK kg ha-1). The economic analysis revealed that, among the treatment combinations t1p1n3 resulted in higher net income (98676 ₹ ha-1) and benefit cost ratio (2.77). Considering yield and economics of cultivation, sorghum may be recommended for cultivation in summer rice fallows with zero tillage, spacing of 45 cm x 15 cm and application of 50:25:50 kg NPK ha-1 along with 5 t ha-1 of FYM.