Pod yield and phosphorus-use efficiency in groundnut (Arachis hypogaea) as influenced by citric acid and its delivery methods under a semi-arid agro-ecosystem

A field experiment was conducted during 2009–11 at Junagadh, Gujarat to find out the effect of citric acid (CA) and its delivery methods on yield, nutrient uptake and use efficiencies of phosphorus in groundnut (Arachis hypogaea L.). Results (mean of three years) revealed that application of citric acid at 2 kg along with farmyard manure (FYM) at 2 t/ha recorded significantly higher pod yield (2.61 t/ha), harvest index (36%) and net returns ( 38,283/ha), which were 28.6, 22.0 and 44.5% higher respectively, over FYM at 2 t/ha without citric acid. Soil available P content (18 kg P/ha) significantly increased with citric acid at 6 kg along with single super phosphate (SSP) at 250 kg/ha over control. Citric acid at 4 and 6 kg along with SSP at 250 kg/ha significantly increased P content in pod and haulm, respectively. P uptake significantly increased with citric acid at 4 kg/ha. Application of citric acid at 2 kg along with FYM 2 t/ha (17.2 kg P), citric acid at 4 kg along with SSP 250 kg/ha (17.2 kg P) and citric acid at 4 kg along with FYM 1 t/ha (8.6 kg P) recorded higher agronomic efficiency (19.5%), recovery efficiency (10.8%) and P harvest index (69%) respectively, over control plots. Application of higher levels of citric acid decreased yield, P uptake and P-use efficiencies. Thus, application of 2 kg citric acid along with FYM at 2 t/ha found appropriate in enhancing groundnut yield and net returns under semi-arid agro-ecosystem.