Nitrogen efficiency of strip-till combined with slurry band injection below the maize seeds

Abstract

The slurry strip-till technique (STR) allows the combination of reduced tillage (strip tillage) with placed injection of slurry below the plant seed position. This technique should improve nitrogen (N) use efficiency of organic fertilizers. The present study aimed at evaluating the N use efficiency of the strip-till technique compared to conventional broadcast slurry application (CONV) to maize (Zea mays L.). Field trials with five treatments (unfertilized control, slurry strip-till with and without nitrification inhibitor (NI), conventional surface broadcast slurry incorporation with and without NI) were conducted on loamy sandy soils in northern and central Germany for three study years (2014–2016). Soil samples were taken from three soil layers (0–30 cm, 30–60 cm, 60–90 cm) in rows and interrows and analysed for soil mineral N (SMN) contents to ascertain N displacement out of the top soil. Furthermore, maize dry matter (DM) yields and N uptakes were determined to calculate N recovery efficiency (NRE) of the studied application systems.SMN analyses showed an increased proportion (+60%) of ammonium nitrogen (NH4-N) in SMN by addition of NI until 34–40 days after fertilization. Nevertheless, DM yields and N uptakes of STR treatments were not significantly different from CONV treated plots. The largest differences between treatments were observed at the earlier harvest dates compared to main harvest presumably due to the observed high NH4-N concentrations in the slurry band, which are known to positively affect early growth of maize plants and better preservation of soil moisture in the STR system. The addition of NI did not lead to significantly increased DM yields and N uptakes. This was most probably due to negligible nitrate leaching in the early growth stages, i.e. NH4-N stabilization took place but could not display its full potential. The STR treatments (STR and STR + NI) showed the highest N recovery efficiencies (up to 78%) among all treatments indicating the lowest potential N losses of this application system. Significant differences between STR and CONV treatments were found, however, only in 2014 and partially in 2015. Thus it can be assumed that the STR system is beneficial to enhance N efficiency of slurry application but further research is required to prove this.