Effect of biofertilizers on N and P economy in palmarosa(cymbopogon martinii)

Abstract

An investigation was undertaken at the College of Horticulture, Kerala Agricultural University, Vellanikkara, during 1994-’95 to study the effect of biofertilizers on N and P economy in palmarosa (Cymbopogon martini stapf. var. motia). The main objective of the study was to assess the possibility of using biofertilizers so as to replace or minimise the expensive synthetic nitrogen fertilizers for palmarosa. The study also aimed to find out the effect of phosphorus solubilising bacteria (Bacillus megatherium var.phosphaticum) in increasing the availability of fixed soil phosphorus, the effect of combination of chemical and biofertilizers on the growth and yield of palmarosa and to work out the N and P economy due to the integration of chemical and biofertilizers. The experiment was carried out using the palmarosa selection ODP-2. The salient findings are abstracted below: The application of chemical fertilizers increased the available N, P and K contents in soil after different harvests, resulted in increased nutrient uptake and thus improved the growth and yield of palmarosa. The oil yield obtained with the application of 20 kg ha -1 each of N and P2O5 was significantly superior to that in the control plot. The different biofertilizer levels were compared with regard to their effect on palmarosa and it was observed that the combined inoculation of Azospirillum and PSB was the best in increasing the available N, P and K contents in soil and the nutrient uptake by the crop. Hence this particular treatment resulted in the highest oil yield which was significantly superior to that in the uninoculated control. The interaction effect of chemical X biofertilizers showed that the oil yield over a period of one year obtained with the application of 20 kg ha-1 each of N and P2O5 was on par with that obtained with the applications of either Azotobacter alone or Azospirillum alone and also the combined inoculation of Azospirillum and PSB. Thus the biofertilizers Azotobacter alone, Azospirillum alone and the combined inoculation of Azospirillum and PSB could substitute chemical fertilizers to the level of 20 kg ha-1 each of N and P2O5. The data again showed that the combined application of chemical and biofertilizers ie, N and P2O5 each at 20 kg ha -1 along with Azospirillum plus PSB resulted in comparable total oil yield, total returns, net returns and benefit-cost ratio as that obtained with the application of N40 P40 along with Azospirillum plus PSB which recorded the highest value.