Localized application of sewage sludge improved plant nitrogen and phosphorus uptake by rhizobox-grown spring wheat

Summary

Sewage sludge (SS) can be used as an alternative fertilizer in agriculture. It is normally broad- casted and plowed into soil, but it is not clear if it has a potential as a placement fertilizer. A rhizo- box experiment was conducted to investigate the placement effect of SS and mineral nitrogen (N) fertilizer on shoot and root growth as well as nutrient uptake of spring wheat (Triticum aesti- vum L.). The treatments included localized SS, mixed SS, localized SS and ammonium, local- ized ammonium, and a control without addition of SS and ammonium to examine the effect of SS placement and, further, if ammonium co-localization would enhance the placement effect. The re- sults show that SS fertilization improved soil N and P availability, which significantly increased plant N and P uptake and enhanced shoot growth, while root length was significantly reduced compared to the control. Localized SS increased root proliferation in the placement region, re- sulting in enhanced uptake of P from the SS patch compared to homogenous application. How- ever, co-localized application of ammonium with SS significantly depressed plant shoot and root growth. Localized ammonium markedly restricted root proliferation in the placement region and reduced soil pH in both bulk soil and placement region, contributing to decreased nutrient uptake and plant growth.