GROWTH AND YIELD OF RICE-FALLOW SORGHUM AS INFLUENCED BY PLANTING DENSITY AND NITROGEN
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Date
2015
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Acharya N.G. Ranga Agricultural University, Guntur
Abstract
A field experiment entitled “Growth and yield of rice-fallow sorghum as influenced by planting density and nitrogen” was carried out on clay loam soil of Agricultural College Farm, Bapatla during rabi, 2014-15. The experiment was laid out in Factorial Randomized Block Design with three replications. The treatments comprised of three planting densities (S1 : 3.33 lakh plants ha-1, S2 : 2.22 lakh plants ha-1, S3 : 1.66 lakh plants ha-1) allotted to factor-A and four nitrogen levels (N0 : 0 kg ha-1, N1 : 50 kg ha-1, N2 : 100 kg ha-1, N3 : 150 kg ha-1) allotted to factor-B.
Plant height was significantly affected by plant densities, however; numerically taller plants were produced at a planting density of 1.66 lakh plants ha-1 than that of 2.22 and 3.33 lakh plants ha-1 at all stages of crop growth (30, 60, 90 DAS and at harvest). At 30 DAS, taller plants (30.6 cm) were produced by the application of 150 kg N ha-1 and it was on a par with the 100 kg N ha-1 and it was significantly superior to other nitrogen levels, whereas, at 60, 90 DAS and at harvest, the highest plant height recorded with the application of 150 kg N ha-1 and it was significantly superior to other N levels (0, 50 and 100 kg N ha-1). The interaction was significant a 60 DAS, where S3N3 treatment combination exhibited superior results.
Drymatter accumulation ha-1 was significantly superior at a planting density of 2.22 lakh plants ha-1 compared to that of lower and higher planting densities at 60, 90 DAS and at harvesting. At 30 DAS greater drymatter production was obtained at higher planting density of 3.33 lakh plants ha-1 compared to that of other planting densities. The maximum drymatter was recorded with the application of 150 kg N ha-1 compared to the rest of the nitrogen levels tested at 30, 60, and 90 DAS. At harvest maximum drymatter production was attained at 150 kg N ha-1 but it was on a par with 100 kg N ha-1, which was significantly superior to other N levels. The interaction was significant at 60 DAS, where S2N2 treatment combination displayed better results and it was on a par with the S1N3 and S2N3 and it was significantly superior to other treatment combinations.
Sorghum sown at a planting density of 1.66 lakh plants ha-1 took greater number of days to attain 50% earhead emergence and days to maturity over other plant densities. Rice fallow sorghum grown without nitrogen took maximum number of days to reach 50% earhead emergence and took minimum number of days to reach maturity.
Significantly higher number of earheads m-2 was noticed at a planting density of 3.33 lakh plants ha-1, which was however, superior to the 2.22 lakh plants ha-1 and 1.66 lakh plants ha-1, respectively. Sowing of sorghum at 1.66 lakh plants ha-1 was found to produce maximum earhead length and number of grains earhead-1, which was significantly higher over rest of the plant densities. The maximum number of earheads m-2, increased earhead length, higher number of grains earhead-1 and greater test weight in sorghum was observed with the application of 150 kg ha-1 nitrogen. Number of earheads m-2, did not significantly responded to application of nitrogen.
Maximum grain yield of sorghum was obtained when the crop was sown at a plant density of 2.22 lakh plants ha-1, which was significantly superior to other plant densities of 3.33 lakh plants ha-1 and 1.66 lakh plants ha-1. Significantly higher stover yield of sorghum was registered at a planting density of 3.33 lakh plants ha-1, which was superior to rest of the plant densities. Harvest index significantly influenced by planting densities, was the highest at 2.22 lakh plants ha-1, which was superior to other densities. When yield is the product of vegetative crop growth, the density-yield relationship is asymptotic. The parabolic response curve is typically a flat topped one with decrease in grain yield on both sides of an optimum. Sorghum sown at a nitrogen level of 150 kg ha1 produced the maximum grain yield which was significantly superior to other N levels. Sorghum crop sown at a nitrogen level of 150 kg ha-1 recorded higher stover yield and it was at par with 100 kg N ha-1 but was superior to other nitrogen levels. Harvest index was the maximum at 150 kg N ha-1 and it was on a par with 50 kg N ha-1 and 100 kg N ha-1, which was however significantly superior to 0 kg N ha-1.
Maximum N uptake by rice fallow sorghum crop at 60, 90 DAS and at harvest was noticed with the planting density of 2.22 lakh plants ha-1 but at 30 DAS maximum N uptake was obtained from a planting density of 3.33 lakh plants ha-1. The uptake of N by stover was higher with a planting density of 3.33 lakh plants ha-1 than that of other two planting densities. But, the uptake of N by grain was greater with a planting density of 2.22 lakh plants ha-1 than that of other two planting densities. Significantly, greater nutrient uptake was noticed in the treatment that received 150 kg N ha-1 at all stages of crop growth. The highest net returns and B : C ratio was recorded with the application of 150 kg N ha-1 at a planting density of 2.22 lakh plants ha-1 over all other treatment combinations.
The highest agronomic efficiency was obtained from S2N1 treatment combination over other treatments. The interactions of plant height and drymatter accumulation and nitrogen uptake by plant at 60 DAS, N uptake by grain at 90 DAS and at harvest, earhead length, number of grains earhead-1, grain yield and harvest index were significantly influenced by planting density and nitrogen levels.
Overall, the results manifested that sowing of rice fallow sorghum at a planting density of 2.22 lakh plants ha-1 was found optimum with a linear response up to 150 kg N ha-1 during rabi under zero - till conditions resulted in higher gross returns, net returns and returns rupee-1 of investment.
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