Agronomic manipulations to increase nutrient content in groundnut (Arachis hypogeae L.)

Abstract

Ammonical fertilizers reduce rhizosphere pH through release of proton and
activates wall loosening processes and root cell elongation thereby, improves the nutrient
uptake. Thus, a field experiment was conducted on the sandy soil of Agricultural College
Farm, Bapatla, Andhra Pradesh, during kharif 2018 to increase nutrient availability in
groundnut through agronomic manipulations. Sixteen treatments comprised of four levels of
nitrogen (ammonium sulphate as source) viz., 0 kg ha-1, 30 kg ha-1, 60 kg ha-1 and 90 kg ha-1
with 60 kg ha-1 and 90 kg ha-1 which were applied in three splits i.e., 1/3rd basal, 1/3rd @ 30
DAS and 1/3rd @ 60 days after sowing (DAS) and four planting geometry viz., 30 x 10 cm, 25
x 10 cm, 20 x 10 cm and 15 x 10 cm. Application of 60 kg N ha-1, produced highest root dry
weight at 30 and 60 DAS, whereas, 90 kg N ha -1 recorded the highest root dry weight at
harvest. N, P and Zn uptake was higher at 90 kg N ha-1, whereas, 60 kg N ha -1 gave greater K
and Fe uptake over other nitrogen levels. Significant acidification of rhizosphere pH was
observed with 90 kg N ha-1 which was on par with 60 kg N ha -1, however, soil bulk pH did
not influence significantly to levels of ammonium sulphate. Root dry weight and nutrient
uptake were highest and rhizosphere pH lowest under 15 x 10 cm spacing. The results thus
revealed that agronomic manipulation through application of 60 kg N ha-1 and adoption of
closer spacing (15 X 10 cm) can significantly influence rhizosphere chemistry thereby
increasing nutrient availability in the groundnut crop.