¹⁵N Fertilizer recovery in different tillage–straw systems on a Vertisol in north‐west Mexico

Abstract

Tillage and residue retention affect nitrogen (N) dynamics and nutrient losses and therefore nitrogen use efficiency (NUE) and crop fertilizer use, however, there is little information about residual fertilizer effects on the subsequent crop. Micro‐plots with 15N‐labelled urea were established in 2014/2015 on a long‐term experiment on a Vertisol in north‐west Mexico. N fertilizer recovery (NFR) and the effects of residual fertilizer N for summer maize (Zea mays L.) and the subsequent wheat (Triticum durum L.) crop were studied in three tillage–straw management practices (CTB: conventionally tilled beds; PB‐straw: permanent raised beds with residue retention; PB‐burn: permanent raised beds with residue burning). Fertilizer 15N recovery rates for maize grain across all treatments were low with an average of 11%, but after wheat harvest total recovered 15N (15N in maize and wheat straw and grain, residual soil 15N) was over 50% for the PB‐burn treatment. NFR was lowest in CTB after two cropping cycles (32%). Unaccounted N from applied fertilizer for the maize crop averaged 120 kg 15N ha−1 after wheat harvest. However, more than 20% of labelled 15N was found in the 0–90 cm soil profile in both PB treatments after wheat harvest, which highlights the need for long‐term studies and continuous monitoring of the soil nutrient status to avoid over‐application of mineral N fertilizer.

Nitrogen Fertilizer Application Alters the Root Endophyte Bacterial Microbiome in Maize Plants, but Not in the Stem or Rhizosphere Soil

“…They combined two N fertilizer application rates, i.e., no fertilizer versus 300 kg urea-N ha −1 , and two tillage-residue management practices, i.e., tilled bed planting with residue incorporated and permanent beds with residue retained. Earlier research showed that retention of crop residue reduced N availability affecting C and N dynamics, grain quality, and the bacterial communities ( 12 – 14 ). The aim of this study was to investigate how two agricultural practices, i.e., tillage and N fertilizer application, affected the bacterial community structure and the microbial functionality in the rhizosphere, roots, and stem of irrigated maize plants cultivated in a Vertisol soil.…”

Application of ammonium to a N limited arable soil enriches a succession of bacteria typically found in the rhizosphere

“…The soil in the CT, PBB and PBC treatments at CENEB was N depleted, even in the soil fertilized with 300 kg urea-N ha −1 for wheat, as application of 300 mg NH 4 + -N more than doubled the emitted CO 2 . Previous findings showed that although the retention of crop residues and fertilization increased yield and wheat grain quality it affected N availability in soil 7 , 8 . As such, the amount of C substrate available for heterotrophs was high but the mineral N severely limited even in the fertilized soil, i.e.…”

“…This study used a subset of treatments with two N fertilizer application rates (no fertilizer versus 300 kg urea-N ha −1 for wheat) and three tillage-residue managements (tilled bed planting with residue incorporated [CT treatment] and permanent beds with residue burned [PBB treatment] and retained [PBC treatment]). Earlier research suggested that the retention of crop residue might lead to a limited N availability in the soil and this might affect C and N dynamics, grain quality and the bacterial communities 7 , 8 . High urea fertilization rates affect nitrifiers and ureolytic soil microbial communities 9 .…”

Effects of conservation agriculture on physicochemical soil health in 20 maize‐based trials in different agro‐ecological regions across Mexico

“…CA can improve physical soil characteristics, such as soil penetration resistance and aggregate stability (Fuentes et al, 2009; Lichter et al, 2008; Verhulst et al, 2011), which can improve infiltration and aeration and reduce erosion (Lanckriet et al, 2012) and nutrient loss. Nutrient cycles can also be impacted by CA, but little is understood about the nitrogen (N) cycle under CA (Grahmann, Dittert, Verhulst, Govaerts, & Buerkert, 2019) or the cycles of phosphorus (P), potassium (K), or micronutrients (Ranaivoson et al, 2017). Residue retention can enhance nutrient cycling but also lead to nutrient immobilization and stratification (Turmel, Speratti, Baudron, Verhulst, & Govaerts, 2015).…”