Mitigation of nitrogen (N) and phosphorus (P) runoff and leaching is a major goal of the nursery industry. Plant production in containers maybe a significant source of surface water and groundwater contamination, and increased environmental concerns have resulted in federal and state water quality regulations intended to control pollutant discharge from irrigated agricultural lands.
Mycorrhizal technology can be included as an important component of nurseries’ cultural programs to reduce nutrient runoff while maintaining plant quality and yield. Arbuscular mycorrhizal fungi are microorganisms specialized to colonize the roots of most plants, establishing a mutual beneficial relationship. They develop an extraradical mycelium that enhances plants’ ability to acquire mineral nutrients and water, and root colonization by mycorrhizal fungi often improves the growth and health of horticultural crops.
Our goal was to investigate the effects of mycorrhizal colonization on N and P leaching from plants grown in containers. We compared the growth response and the content of nitrate, ammonium, and orthophosphate, in leachates collected from mycorrhizal (AM) and nonmycorrhizal (NonAM) plants of the fast growing perennial, Encelia californica, and the slow growing woody shrub, Rhus integrifolia. Plants were grown without fertilizer, or with half and full rate of 18N-6P-12K Osmocote controlled release fertilizer.
Results/Conclusions
Mycorrhizal colonization increased the growth and nutrient uptake of E. californica and R. integrifolia, but was more effective at decreasing nutrient leaching from containers with E. californica. Leachates collected from AM plants of E. californica, had significantly lower N and P content than those from NonAM plants, at all fertilizer rates. In contrast, only the leachates from AM plants of R. integrifolia grown without fertilizer had generally lower nutrient content than those from NonAM plants. Nevertheless, mycorrhizal colonization reduced the fertilizer requirement to achieve maximum growth in both species. AM plants of E. californica and R. integrifolia grown with half rates of Osmocote had greater dry mass than the NonAM ones grown in full rates of Osmocote. Our study shows that mycorrhizal colonization can reduce N and P runoff and leaching either by increasing plant nutrient uptake, or by allowing the use of lower fertilizer rates and increasing nutrient use efficiency.