Nitrogen and phosphorus fertilizer use efficiency: the interactive effects of fertilization and liming

Abstract

Nitrogen (N) and phosphorus (P) play important roles in increasing agricultural productivity. However, excessive use of N and P fertilization can result in low N and P fertilizer use efficiencies (RE_N and RE_P) and loss of N and P through gaseous emission and leaching, but which also depend on soil pH conditions. In a full factorial glasshouse experiment using pots with 2.5 kg soil and adding N (0 and 100 kg N ha⁻¹), P (0 and 50 kg P ha⁻¹) fertilizer and lime (0, 3.5, 14 t ha⁻¹, 100 % calcium carbonate equivalent) we investigated the main and interactive effects of our treatments on RE_N and RE_P in wheat (Triticum aestivum) grown in a P-poor soil. The RE_N was close to zero without P fertilization regardless of liming, but increased to 46 % with P fertilization (averaged across liming treatment) because of strong P limitation. Likewise, N fertilization increased RE_P from 6 % to 8 % averaged across the liming treatment. However, liming decreased RE_N (only when P fertilizer was added), possibly because of enhanced net N mineralization in the soil making plants less dependent on N fertilizer with liming, and increased RE_P, possibly because of reduced fertilizer P-immobilization in the soil with low pH. Overall, N and P fertilizer and lime addition changed RE_N and RE_P by changing wheat growth along with N and P uptake, thereby affecting soil available nutrients, nitrous oxide emissions and N and P loss through leaching. We highlight the importance of adjusting N and P fertilization with liming to optimize RE_N and RE_P and reduce N and P loss.