Lysimeter study of nitrogen losses and nitrogen use efficiency of Northern Chinese wheat

Abstract

A study was conducted in the lysimeters and rain-out shelter facility at Shandong Agricultural University to investigate the impact of nitrogen (N) fertilization management practices and irrigation on the losses of N and N use efficiencies of winter wheat in the Huang Huai Hai Plains of northern China. 4 factors, each with two levels, including wheat varieties (SM15 and JM19), irrigation level (well water and deficit water), N fertilizer type (manure fertilizer and urea), N fertilizer rates (90 and 180 kg N ha−1) were applied in duplicate over three wheat growing seasons from 2009 to 2012. Ammonia volatilization rates (AVR) were highest immediately following fertilizer application and declined over 20 days after fertilization, AVR following urea is significantly greater than following manure application and is largely affected by soil NH4+-N concentrations. Cumulative ammonia volatilization (CAV) from urea was approximately three times that from manure. AV accounts for most of N losses and may account for 25% or more of applied N. Leaching losses increased with N fertilization concentration. Pre-winter leaching losses accounted for 69.6–100% of total leaching loss. Total N losses through AV and leaching during the whole wheat growing season were estimated to range from 30 to 60% of applied N. Nitrogen use efficiency (NUE), and N uptake efficiency (NUpE) of the cultivar SM15 is 10.1 and 19.8% greater than JM19 by average under well watered conditions, respectively, but NUE and N utilization efficiency (NUtE) of JM19 were 17.5% and 21.8% higher than SM15 under water stress condition, respectively. In addition, the difference of crop N use efficiency (NUEc) and crop N uptake efficiency (NUpEc) between two varieties was inconsistent to NUE and NUpE. The following results were implicated from this study: (1) ammonia volatilization could be reduced by 66.6% through manure application instead of urea application; (2) reducing fertilizer and irrigation supply during pre-winter stage could be a effective method to reduce N loss in the region; (3) all treatments in this study lead to progressively lower soil fertility except for the 180 kg N ha−1 manure which is able to maintain soil fertility; (4) wheat variety, N fertilizer level, irrigation amount and their interactions have obviously impact on NUE parameters.