Effect of Zn enriched organic manures and zinc solubilizer application on the yield, curcumin content and nutrient status of soil under turmeric cultivation

Abstract: A field experiment was conducted to study the effect of Zn enriched organic manures and Zn solubilizers on the yield, curcumin content of turmeric and nutrient status of the soil. The treatment with FYM + zinc solubilizing bacteria showed higher turmeric rhizome yield increase of 21.6 percent than the FYM alone treatment (9.1 per cent) than no manure (control). The dry rhizome yield, reflected the promising effect of Zn and Fe enriched coirpith or FYM, and Zn enriched coirpith or FYM at M₁ (no manure) while at M₂ (NPK + FYM) and M₃ (NPK+FYM+Zn solubilizing bacteria), the foliar spray of Zn + Fe + MOP excelled the remaining treatments. Incorporation of farmyard manure at 12.51 ha^-1 along with Zn solubilizing bacteria stood superior by registering highest values for available of N, P and K content in the soil. The Zn solubilizing organism (Bacillus sp.) identified interestingly proved to have favorable effect on the availability of N, P and K. The effect of micronutrient treatments comprising of soil application of per se ZnSO₄, FeSO₄ and fortified FYM with Zn and Fe and foliar spray of these two nutrients resulted in synergistic effect on the enhanced availability of not only micronutrients but also K. The DTPA - Zn content of the soil though evidenced significant variation for the different treatments of FYM, FYM + ZSB (Zn solubilising bacteria) and micronutrients on an overall basis did not exceed the deficiency level. Addition of Fe with Zn either as such or fortified with FYM / with coirpith showed synergistic effect on Zn availability in the soil. The available B content of the soil showed an upheaval trend for manuring and Zn and Fe applications. During different stages of crop growth and at harvest stage, DTPA - Fe content in none of the treatments exceeded the threshold level. However, enhancement for treatments with organic manures and micronutrients were statistically perceptible. The availability of Cu and Mn in the soil, brought out the positive effect of Zn and Fe added as such or as fortified either alone or along with FYM and FYM + ZSB. Both content as well as uptake of all the major nutrients in the turmeric plant right from the early phase of crop growth to harvest were positively altered by FYM, FYM + ZSB and soil and foliar application of Zn and Fe.