Natural soils change by long-term pedogenetic mechanisms, but tillage effects can also strongly affect the evolution of soils, mainly their physicochemical properties. The present paper describes the impact of fertilizers and amendments on soil mineralogy in experimental plots, without plant interaction.

The soils of the 42 plots experiment at the INRA experimental station in Versailles (France) have been managed with fertilizers without plant growth since 1929. Strong changes in pH were observed and cation exchange capacities doubled between low and high pH (from 3.6 to 8.2). Strong acidification caused more evolution in the clay particle distribution without selective action on the clay composition.

While the clay content varied only slightly, the organic matter content changed considerably, decreasing with non-organic treatment and increasing in the plot with manure treatment. The major clay minerals in the experimental plots are two disordered illite-smectite mixed-layer minerals, with minor amounts of illite/mica and kaolinite. Most treatments effected only minor changes in clay mineralogy. However the illite (non-expandable mineral) content increased in plots with K addition either as KCl treatment or in manure amendments by increasing the illite content and the illite (non-expandable layer) content of the I-S minerals. Manure changed the I-S mineral to a greater extent.

The current study evaluated the effect of sowing date (early, mid-August or timely, mid-September) on two winter wheat (Triticum aestivum L.) cultivars (Hereford, Mariboss) with different rates of nitrogen (N) (0–225 kg total N/ha) applied as animal manure (AM; cattle slurry) or mineral fertilizers (N: phosphorus: potassium; NPK). Overwinter plant N uptake and soil mineral N content were determined during 2014/15, while harvest yields (grain, straw, N content) were determined during 2014/15 and 2015/16. Overwinter uptake of N was 14 kg N/ha higher in early than in timely-sown wheat. Despite very different yield levels in 2015 and 2016 harvests, the advantage of early sowing on grain yields was similar (1.1 and 0.9 t/ha); straw yield benefits were greater in 2015 (1.7 t/ha more) than in 2016 (0.4 t/ha more). In 2015 and 2016, N offtake was 35 and 17 kg N/ha higher in early than in timely-sown wheat, respectively. The mineral N fertilizer value of cattle slurry averaged 50%. Early sowing increased the apparent N recovery (ANR) for wheat regardless of nutrient source. However, ANR was substantially higher for NPK (82% in 2015; 52% in 2016) than for AM (39% in 2015; 27% in 2016). Performance of the two cultivars did not differ consistently with respect to the effect of early sowing on crop yield, N concentration and offtake, or ANR. Within the north-west European climatic region, moving the sowing time of winter wheat from mid-September to mid-August provides a significant yield and N offtake benefit.