Effects of ¹⁵N Split‐application on Soil and Fertiliser N Uptake of Barley, Oilseed Rape and Wheat in Different Cropping Systems

Abstract

In intensive farming systems, farmers split up and apply the N fertilization to winter cereals and oilseed rape (OSR) at several dates to meet the need of the crop more precisely. Our objective was to determine how prior fertilizer N application as slurry and/or mineral N affects contributions of fertilizer-and soil-derived N to N uptake of barley (1997), oilseed rape (OSR; 1998) and wheat (1999). In addition, residual fertilizer N effects were observed in the subsequent crop. Since autumn 1991, slurry (none, slurry in autumn, in spring, in autumn plus in spring) and mineral N fertilizer (0, 12 and 24 g N m )2 ) were applied annually. Each year, the treatments were located on the same plots. In 1997-1999, the splitting rates of the mineral N fertilization were labelled with 15 N. Non-fertilizer N uptake was estimated from the total N uptake and the fertilizer 15 N uptake. All three crops utilized the splitting rates differently depending on the time of application. Uptake of N derived from the first N rate applied at the beginning of spring growth was poorer than that from the second splitting rate applied at stem elongation (cereals) or third splitting rate applied at ear emergence or bud formation (all three crops). In contrast, N applied later in the growing season was taken up more quickly, resulting in higher fertilizer N-use efficiency. Mineral N fertilization of 24 g N m )2 increased significantly non-fertilizer N uptake of barley and OSR at most of the sampling dates during the growing season. In cereals, slurry changed the contribution of non-fertilizer N to the grain N content only if applied in spring, while OSR utilized more autumn slurry N. In OSR and wheat, only small residual effects occurred. The results indicate that 7 years of varying N fertilization did not change the contribution of soil N to crop N uptake.

The fates of 15N-labeled fertilizer in a wheat–soil system as influenced by fertilization practice in a loamy soil

“…The total N uptake by wheat derived from urea fertilizer was higher in SA (20.7–76.1 kg ha −1 ) than in BA treatment (19.0–43.4 kg ha −1 ), showing that SA of N fertilizer could enhance N uptake from N fertilizer, especially for higher N application rates. Large amounts of N fertilizer applied at sowing time likely increased fertilizer-N immobilized by soil microorganisms, and then led to poor synchrony between N supply and crop demand 34 36 . López-Bellido et al .…”

“…The surface-applied N fertilizer absorbed by plants is dependent on subsequent rainfall and it cannot move into the root zone and be utilized by plants when rainfall is limited 19 . The other reason was that large amounts of N fertilizer were likely taken up by soil microbes in the early growing stage of wheat due to low wheat competition, and so high levels of N fertilizer were in organic forms in the soil during the rapid growth stage of wheat 36 38 . High application rate of N fertilizer at the early growth stage of the crop would enhance the unaccounted N losses through N leaching 34 .…”

Spring triticale yield formation and nitrogen use efficiency as affected by nitrogen rate and its splitting

“…The uptake of N derived from the first N rate applied at the beginning of spring growth was poorer than that from the second splitting rate applied at stem elongation or third splitting rate applied at ear emergence (Sieling, Beims, 2007). In contrast, N applied later in the growing season was taken up more quickly, resulting in higher fertilizer NUE.…”

Winter triticale yield formation and quality affected by N rate, timing and splitting

“…In intensive farming systems, farmers split up and apply the N fertilization to winter cereals (barley and wheat) and oilseed rape at several dates to meet the need of the crop more precisely (Sieling and Beims 2007). All three crops utilized the splitting rates differently depending on the time of application.…”