The effect of the combination of arbuscular mycorrhiza and rhizobacteria and doses of NPK fertilizer on the growth of Sorghum bicolor (L.) Moench

Sorghum bicolor (L.) Moench is one of the agricultural commodities that has important economic value. The use of fertilizer is done to increase productivity in order to follow the demand for sorghum which is quite high. Farmers widely use chemical fertilizers because they are cheap and easy to apply, but it has a negative impact on the environment. Sorghum growth naturally depends on microbes in the root area such as arbuscular mycorrhiza and rhizobacteria which have been known to increase sorghum growth. Arbuscular mycorrhiza and rhizobacteria as biological fertilizers can reduce the use of chemical fertilizers. This research aimed to study the effect of a combination of arbuscular mycorrhiza and rhizobacteria and doses of NPK fertilizer on sorghum growth. This study used two treatment factors, namely combination of microbes (arbuscular mycorrhiza, Azospirillum sp. and Klebsiella sp.) and doses of NPK (without NPK, 25% NPK, 50% NPK, 75% NPK, 100% NPK). Sorghum seeds of each treatment were individually grown on zeolite medium and were maintained in the greenhouse for two months. Plant growth parameters, colonization percentage of arbuscular mycorrhiza, rhizobacterial population, and root phosphate content were measured. Combination of Azospirillum sp. and Klebsiella sp. significantly increased shoot height and number of leaves. Combination of arbuscular mycorrhiza, Azospirillum sp. and Klebsiella sp. produced the highest dry weight. The dose of 25% NPK significantly increased all plant growth parameters. Combination of two rhizobacteria produced the highest root P content.