Efficacy of Bacterial or Fungal Soil Amendments on Vegetables Following Peanut

Abstract

Amendment of soil with microorganisms during the growth cycle of one crop may affect development of succeeding crops. Species of Rhizobium bacteria or abuscular-mycorrhizal fungi were added alone to, or in combination with, potting soil in pots in a greenhouse. Controls were no amendments. Seed of peanut (Arachis hypogaea L.) were planted and two levels of a combination NPK fertilizer, the recommended and one-fourth the recommended rate, were applied. After harvest of peanut and remoistening of soil, seed of the bell pepper (Capsicum annuum L.) or navy bean (Phaseolus vulgaris L.) were sown into the same planting medium in pots without additional inoculation with microbes. Dry weights of above-ground vegetative and edible portions of crops were determined. Inoculum type only affected peanut top and total dry weights. The recommended fertilizer level did not affect peanut yield but did cause improvement in bell pepper and navy bean yield over that of the deficient fertilizer rate. In field experiments, peanut was planted into soil receiving Rhizobium spp. bacteria, or arbuscular-mycorrhizal fungi alone or in combination. Controls consisted of no amendment. Only the recommended fertilizer rate was used. In the next 2 years, bell pepper or navy bean were established in plots without use of additional microbial amendment. Yields and nutrient contents of crops were determined. Type of inoculum did not affect yield or nutrient content in any crop. Bell pepper marketable yield was unaffected by year, and navy bean seed yield was higher in 2004 than in 2005. In both years, navy bean yields were below U.S. averages. Concentrations of most nutrients in edible portions of bell pepper and navy bean were lower in 2004 than in 2005. Results of the field trials were generally similar to those of greenhouse studies. Use of inocula did not provide substantial benefits to yield or nutrient content of peanut or vegetable crops that followed.