Turfgrass

Fertilization

Fertilization of turfgrass provides supplemental plant nutrients to stimulate growth to compete against weeds, recover from traffic, improve appearance, and replace exports. Nutrients are applied to turf in dry fertilizer, liquid solution and suspension in boom sprayers, and fertigation (fertilization through an irrigation system). High concentration synthetic nutrient sources and low concentration natural nutrient sources such as manure and compost are used to feed nutrients to turfgrass.

In extensive wild grasslands throughout the world the dung of herbivores is recycled naturally. Extensive grasslands were thus nourished for millions of years with no human involvement. And no fertilization.

Nutrients are exported from turfgrass by runoff, leaching, removal of clippings, and gaseous losses. Nitrogen is generally the only nutrient that can exit soil as a gas, and this is mostly from wet anaerobic soils. In wet soils ammonia gas can be produced and volatilize, and so can diatomic nitrogen and the powerful greenhouse gas nitrous oxide (N2O). Turfgrass areas can be managed to reduce nutrient exports and reduce need for supplemental fertilization by recycling clippings, using slowly available nutrients, and considering soil test results and actual plant needs in carefully metering fertilizer.

From an environmental perspective, almost all of the concern about nutrient export involves phosphorus and nitrogen as non-point pollution.  Phosphorus causes eutrophication of freshwater ecosystems. Because phosphorus is strongly retained by organic matter, if phosphorus escapes turfgrass areas at all, it is most likely by runoff of sediment or misapplication to impervious areas, so this should be easily managed. Excessive nitrogen mostly causes eutrophication of coastal (hence, saltwater) estuaries, evidenced in some cases by “red tide.” Reactive nitrogen in soil occurs mostly as nitrate anions which have low retention on soil particles. Turfgrass that is actively growing with deep roots is highly effective in capturing nitrogen and the most dramatic nitrate leaching problems have been demonstrated when highly soluble nitrate is applied to turfgrasses with shallow roots.