BEATE FORMOWITZ1, F. ELANGO2, TORSTEN MÜLLER3, ANDREAS BUERKERT1
1University of Kassel, Germany
2Earth University, Costa Rica
3University of Kassel, Department of Soil Biology and Plant Nutrition, Germany
Effective microorganisms (EM) are often used in low-external input agricultural systems of the humid tropics to accelerate composting and enhance plant growth. However, little process-oriented research as been done to substantiate these effects and unravel possible mechanisms. This study aimed at comparing the effects of EM addition on the decomposition of banana (Musa sp.) residues and on banana root and shoot growth to those of an untreated control and a series of other composting additives.
In comparison to non-EM controls (EM-`Bokashi' produced from composted banana residues with: w = water, m = molasses, EMst = sterilized EM), EM did not increase the mineralisation of banana compost. Nitrogen concentration was highest in EMst (17.1gkg-1) and lowest in EM (15.3 g kg-1). The highest C concentration was found in EM (492gkg-1 after 30 days of composting) and the lowest in Emst (436 g kg-1). The resulting C/N ratio was 33.5 for EM and 25.6 for EMst. Concentrations of K, P, Ca, Mg and a weight loss of approximately 77.9% were similar for all treatments. The ergosterol concentration was significantly higher in EM-Bokashi (77 mg g-1), whereas it was lowest in EMst (29 mg g-1). Application of all compost variants significantly increased shoot growth of young banana plants under greenhouse conditions compared to controls grown in pure soil (final height in cm: c = 62.3; w = 69.5; EM = 70.8; m = 72.0; EMst = 72.7). EM-Bokashi and Bokashi produced with molasses significantly decreased the number of root nematodes under greenhouse conditions as compared to the control (nematodes per 100 g: c = 254; w = 143; EMst = 143; m = 67, EM = 38). Although root growth of the plants in the greenhouse was not improved by the Bokashi variants, EM-Bokashi increased secondary root growth of adult banana plants in the field (EM = 186.7 g) compared to non-composted fresh banana leaves (fb = 134.6 g) and a control without mulch application (c = 147 g). Molasses produced the lowest root mass (104.2 g).