VESICULAR - ARBUSCULAR ENDOMYCORRHIZAL INOCULUM PRODUCTION .2. EXPERIMENTS WITH MAIZE (ZEA-MAYS) AND OTHER HOSTS IN NUTRIENT FLOW CULTURE

Experiments are described that led to a better understanding of nutrient requirements for mycorrhizal development in nutrient flow (NFT) culture. For maize infected with Glomus mosseae, solution P concentration around 0.5 mg/l-1 was optimal, giving approximately 50% infection. With more P, infection quickly decreased, and it was also low with only 0.3 mg/l-1 P. Critical solution P was thus much lower than for Phaseolus vulgaris infected with G. fasciculatum (E3). When rock phosphate was used as P source, solution pH was very important because of its effect on P solubility. N source (NO3- versus NH4+) was important for the same reason. Ca levels also affected mycorrhizal development, the optimum concentration for maize (above 15 mg/l-1) being higher than that needed for beans. Maize also had a much higher Fe requirement. The relative merits of rock versus soluble P are discussed. Observations are also reported on inoculation techniques for NFT and on mycorrhizal infection with other host-endophyte combinations.