RHIZOSPHERE DYNAMICS AND CROP GEOMETRY IN GROUNDNUT
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Date
2019
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ACHARYA N G RANGA AGRICULTURAL UNIVERSITY, GUNTUR
Abstract
A field experiment was conducted at Agricultural College Farm, Bapatla on sandy upland soils during post-monsoon, 2018 to investigate the rhizosphere dynamics and crop geometry in groundnut. The experiment was laid out in randomized block design with factorial concept and replicated thrice. The treatments consisted of four levels of nitrogen viz., N1- 0 kg ha-1, N2- 30 kg ha1, N3- 60 kg ha-1 and N4- 90 kg ha-1 with N3 and N4 given in three splits i.e., 1/3rd basal, 1/3rd @ 30 DAS and 1/3rd @ 60 DAS. Four levels of population densities viz., 30 x 10 cm (120 kg ha-1), 25 x 10 cm (140 kg ha-1), 20 x 10 cm (180 kg ha-1) and 15 x 10 cm (230 kg ha-1).
Nitrogen levels and population densities significantly influenced growth, yield attributes, yield, nutrient uptake and net returns of groundnut as well as available soil nutrient status after harvest of the crop.
The results indicated that among the four levels of nitrogen, the growth characters viz., plant height, drymatter accumulation, nodule number and dry weight and root dry weight were higher with @ 90 kg N ha-1 followed by 60 kg N ha-1, which were on par and were significantly superior to other levels of nitrogen. Similarly, no. of pods per plant, pod yield and haulm yield were also higher with 90 kg N ha-1 closely followed by 60 kg N ha-1 which was significantly superior to 30 and 0 kg N ha-1. However, number of pops per plants decreased with increasing level of nitrogen.
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Decreasing spacing from 30 x 10 cm to 15 x 10 cm significantly increased the growth characters viz., plant height, drymatter accumulation. Number of nodule per plant, nodule dry weight per plant and root dry weight per plant decreased with increase in population densities. Similarly pod yield, haulm yield and harvest index also increased with increase in population densities and were more with 15 x 10 cm spacing. However, number of pods per plant significantly decreased due to increase in population density.
Nutrient content and uptake significantly increased with increase in nitrogen levels and higher uptakes of N, P, K, Zn and Fe were obtained with 90 kg N ha-1 which was significantly on par with 60 kg N ha-1. Nutrient content was higher with wider spacing of 30 x 10 cm, which was on par with 25 x 10 cm. However, uptake was significantly higher with narrower spacing of 15 x 10 cm over other levels.
The microbial population was significantly influenced by levels of nitrogen fertilization and significantly superior population of fungi, bacteria and actinomycetes was found with 90 kg N ha-1. Microbial responded significantly to population densities and significantly higher microbial count was obtained with 15x 10 cm spacing.
The influence of ammonium sulphate on soil bulk pH did not differ with levels of nitrogen and population densities. However, significant acidification with increasing levels of nitrogen was observed where lowest pH was obtained with application of 90 kg N ha-1 which was on par with 60 kg N ha-1 in the rhizosphere zone. Population density influenced rhizosphere pH significantly and narrower spacing of 15 x 10 cm resulted in lower pH.
Maximum gross returns were obtained with nitrogen application @ 90 kg ha-1and was on par with 60 kg N ha-1 and with population density of 15 x 10 cm. Net returns and returns per rupee investment followed similar trend as that of gross returns.
With the increase in levels of nitrogen application, soil available N increased. Application of nitrogen @ 90 kg N ha-1 resulted in significantly higher available soil N, however, it was on par with 60 kg N ha-1.
Interaction between nitrogen levels and population densities was however found to be non-significant for all parameters.
It can be concluded from the present investigation that maximum pod yield and economic returns can be obtained by the application of @ 60 kg N ha-1 and with a spacing of 15 x 10 cm which can be advisable under rainfed conditions of Coastal Andhra Pradesh.
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D5902
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