Nutrient scheduling in rainfed sorghum (Sorghum bicolor L. Moench)

Abstract

The study entitled “Nutrient scheduling in rainfed sorghum (Sorghum bicolor L. Moench)” was undertaken at College of Agriculture, Vellayani, during 2019 – 2021. The main objectives were to standardise the nutrient schedule for rainfed sorghum and to work out the economics. The field investigation was conducted during summer 2021 and the experiment was laid out in factorial randomised block design with 12 treatment combinations, replicated thrice. The treatments comprised combinations of three N:K ratios (r1 -1:0.5, r2 -1:1 and r3 -1:1.5) and four times of applications (t1- ½ N as basal + ½ N at 30 DAS + full K as basal, t2- 1 /3 N as basal + 1 /3 N at 30 DAS+ 1 /3 N at 60 DAS + full K as basal, t3- ½ N and ½ K as basal + ½ N and ½ K at 30 DAS, t4- 1 /3 N and 1 /3 K as basal + 1 /3 N and 1 /3 K at 30 DAS + 1 /3N and 1 /3 K at 60 DAS). The sorghum variety used for the study was Co-30. The results of the study revealed that plants were significantly taller in r3 at 60 DAS (122.33cm), 90 DAS (237.18 cm) and harvest (248.27cm). Plant height was significantly more at 30 and 60 DAS with t4 (27.71 and 122.97 cm respectively) while t3 resulted in significantly taller plants at 90 DAS and harvest (236.38 and 244.47 cm respectively). Among the interactions, r3t4 and r1t4 resulted in significantly taller plants at 30 DAS and 60 DAS, while at 90 DAS and harvest, r3t1 was superior. The N:K ratio r3 (1:1.5) produced significantly more number of leaves per plant at all stages of observation. The treatment t4 recorded significantly more number of leaves at 30 DAS (4.50) while t3 recorded higher number of leaves at later growth stages. Interaction r3t4 produced significantly higher number of leaves at 60 DAS, 90 DAS and at harvest. Leaf area index recorded was significantly higher with r3 (2.65), t4 (2.62) and the interaction r3t4 (5.90) at 40 DAS. The crop took least number of days to reach 50 per cent flowering in r3 (57 days), t4 (54.89) and r3t4 (50.67 days). The dry matter production at harvest was the highest in t3 (6843.00 kg ha-1 ) and was on par with t4. Chlorophyll content was significantly higher at 30 and 60 DAS in r3 and t3 respectively and t3 was comparable with t4. The interaction r2t4 recorded higher chlorophyll content at 30 DAS. Rooting depth and root volume were significantly higher in r3 and t4, and interactions r3t2 and r3t4 had higher rooting depth and root volume respectively. Length of panicle was significantly higher in r3 (24.80 cm) and t3 (20.22 cm). The treatment combination r2t3 resulted in significantly longer panicles. Grain weight per panicle (46.47 g) was significantly higher in r2. Grain yield was significantly higher with r2 (3449.33 kg ha-1 ) and was comparable with r3 (3298.67 kg ha-1 ). The highest grain yield (3532.22 kg ha-1 ) was recorded by t3, followed by t4 (3350.11 kg ha-1 ) which were on par. The treatment combination r3t3 resulted in the highest grain yield (3635.67 kg ha-1 ) and was on par with all other treatments except r1t1 and r1t2. Harvest index was significantly superior in r2 (1:1) and r3 (1: 1.5), both producing a value of 0.45 compared to r1 (0.39). N uptake and K uptake were the highest in r2 and were on par with r3 while P uptake was the highest in r3 comparable with r2. The highest N uptake was recorded with t3 which was comparable with t4. The treatment t3 which was comparable with t4 resulted in significantly higher P uptake. K uptake was the highest with t3 (272.82 kg ha-1 ) and was comparable with t2. The treatment r2 resulted in significantly higher pH (5.70) and was comparable with r3 (5.67). Both t3 and t1 recorded higher soil pH of 5.70 after the experiment. Highest organic carbon content was recorded with r3 (0.83 per cent), t3 (0.89 per cent) and r3t3 (1.06 per cent), and r3 was on par with r2 whereas t3 was comparable with t4. Significantly higher available N content was recorded with r3 and t4, and t4 was comparable with t3. The treatment combination r3t3 which was on par with r2t4 recorded significantly higher available N content. Available P content was significantly higher with r2, t3 and r2t3. Net income was the highest (₹ 39737 ha-1 ) with r3t3 while r2t4 and r3t3 resulted in the highest BCR of 2.04. Considering the growth, yield and economics, the modified fertilizer dose of 50: 25: 75 kg ha-1 NPK with N and K in two equal split doses, half of each at basal and at 30 DAS and P as basal dose can be recommended for cultivating high yielding sorghum varieties as rainfed crop in southern Kerala