Localized nutrient supply can facilitate root proliferation and increase nitrogen-use efficiency in compacted soil

Soil compaction constrains root growth and crop yield. Previous studies have shown that localized nutrient
supply can significantly improve maize plant growth in field conditions at the early growth stage. However, this
promoting effect has not been tested in the compacted soil. We describe 2-year field experimentation on a fluvo-
aquic soil in the North China Plain to investigate the effect of localized vs. broadcast ammonium and phosphorus
supply on maize under three soil compaction treatments (NC: non-compacted, C: compacted and SC: severely
compacted) during 2012 and 2013. Results showed that compared with broadcast ammonium and phosphorus
(BNP), localized ammonium and phosphorus supply (LNP) resulted in significantly higher PFPN in the NC (by
31–37%), C (by 43–44%) and SC (by 45%) treatments at harvest. When soil was compacted (C and SC), the
enhancement of nitrogen (N) utilization in the LNP treatment was attributed to the increased root growth,
including greater specific root length (a greater proportion of fine roots), lower root tissue density and deeper
rooting at the seedling stage, especially in the compacted treatment (C). The enhanced root penetration capacity
contributed to the increased N and water uptake from the deep soil layers. Our study highlighted the importance
of nutrient management for mitigating negative impacts of soil compaction on crops, and will underpin new soil
compaction management practices by considering optimal fertilization to strengthen the root-soil interactions.