Interactive effects of attapulgite and nitrogen fertilizers on the nitrogen fertilizer use efficiency and residual levels in saline soil

Background and aims

Attapulgite has been widely used to reclaim saline soils because it can affect the processes of nitrogen (N) transport and transformation through adsorption. However, the impact of attapulgite on crop uptake of N and the underlying mechanisms remain poorly understood.

Methods

We conducted a pot experiment over two seasons involving a rotation of barley (Hordeum vulgare) and maize (Zea mays) in which distinct ¹⁵N-labellled fertilizers (low N [LN], 180 kg N ha⁻¹; high N [HN], 240 kg N ha⁻¹) and attapulgite (no attapulgite; 5% attapulgite) were utilized. The effects of attapulgite on the utilization of N fertilizer and its residues were analysed along with the utilization of residual N fertilizers by subsequent crops.

Results

Barley utilized 42.91–46.79% ¹⁵N fertilizer. Notably, the LN treatment involving attapulgite reduced ¹⁵N fertilizer utilization by barley by 3.33%, whereas it increased it by 4.62% in the HN treatment. A total of 14.26–20.55% of the ¹⁵N fertilizer remained in the soil, and attapulgite had no significant effect on the ¹⁵N fertilizer residual levels or its utilization by maize. The addition of attapulgite significantly reduced the abundance of genes involved in nitrification and denitrification, thereby decreasing the risk of N loss by denitrification.

Conclusion

Attapulgite offers significant benefits in terms of N fertilizer absorption and crop N utilization efficiency and mitigates the loss of N when high levels of fertilizers are applied.