Response of alfalfa to inoculation with Penicillium bilaii (Provide)

Abstract

Yield and phosphorus (P) uptake response of alfalfa (Medicago sativa L.) to inoculation with Penicillium bilaii (Provide) at varying rates of P fertilizer, was determined in small- and large-plot experiments located in the Dark Brown, Black or Gray soil climatic zones of Saskatchewan and Alberta from 1994 to 1996. Soil at the sites contained low to medium levels of available P. In the establishment year of the small-plot experiments, inoculation of alfalfa with P. bilaii increased yields and P uptake by 3 to 18%, when averaged across P fertilizer rates. The largest response to inoculation occurred early in the growing season. In the year following establishment, yield and P uptake of inoculated alfalfa averaged 3% greater than uninoculated plants. In the establishment year of the large-plot experiment in 1994 and 1995, yields and P uptake of inoculated alfalfa at 10% bloom were 7 and 26% greater than uninoculated plants, when grown without and with a wheat (Triticum aestivum L.) companion crop, respectively. Unlike the small-plot experiment, alfalfa in the year following establishment did not respond to inoculation performed the previous year. The P credit (P fertilizer replacement value) of P. bilaii inoculation, based on yield response in the establishment year and in the year following establishment, averaged 4.6 kg P ha−1 in the small-plot experiments and 5.3 kg P ha−1 in the large-plot experiments. Tillage cropping practices that conserve water near the soil surface, and inclusion of a companion crop, may increase the probability of alfalfa response to P. bilaii inoculation as well as the efficacy of that response. Key words: Medicago sativa, Penicillium bilaii, Rhizobium meliloti, Triticum aestivum, phosphorus