Management of soil-borne diseases of onions in rice-vegetable system using specific biological control agents (vesicular-arbuscular mycorrhizae, VAM)
2008
Brown, M.B. | Gregon, E.B. | Gapasin, R. | Miller, S.A. | de Castro, A.M., Philippines Univ. Los Banos, College, Laguna (Philippines). National Inst. of Molecular Biology and Biotechnology
The effect of vesicular arbuscular mycorrhizae (VAM) on growth, onion yield, and root-know and pink root infection on Yellow Granex and Red Creole onions at different fertilizer levels were studied in the field. VAM was applied on the surface of the seedbed prior to seeding. Different rates of NPK in kg/ha were calculated based on the recommended rate for onions and the available P and K in the soil. Vesicular arbuscular mycorrhizae (VAM) stimulated the growth and yield of Yellow Granex. Significant increase of 10% in plant height, 27% in leaf weight, and 8% in bulb diameter were achieved at 0 or low N and available P in the soil. Results showed that high rates of N fertilizer were unnecessary when VAN are present in roots. Application of additional P fertilizer is not also required if P is available in the soil. Additional K, however, maybe important. Differences in yield per plot of 200 plants were small but results clearly indicate that VAM could enhance the yield Yellow Granex. Pre-treatment of VAM on Red Creole, however, did not contribute any improvement on its growth and yield indicating the influence of host plant to VAM infection. Result also suggest the need for a preliminary screening of host plant to VAM species before recommending the use of VAM in th e field. Fertilizer application in onion of many farmers in Nueva Ecija [Philippines] was very high with 87% were applying more than 120 kg N/ha, 52% more P and 19% more K than the recommended rate. Farmers apply a concoction of different fertilizers like a bag of urea, ammonium sulfate, and 16-20-0, and complete fertilizers at different times during the onion growing season. High fertilizer input, however, is unnecessary and a waste of money especially if VAM is present in the roots.
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