Effects of combined application of nitrogen from different source on nitrogen utilization of spring maize and sustainability of soil fertility in Northeast China

Objectives This paper focused on sustaining high use of nitrogen (N) and improving soil fertility by applying different N forms in Northeast China.

Methods A 3-year field experiment was conducted in Heilongjiang Province, China during 2013 to 2015. Under the same rates of P and K input, four treatments were designed: 1) only 50% maize straw (N0); 2) 100% chemical N fertilizer (N 165 kg/hm², N1); 3) 80% chemical N fertilizer (60% fast released and 20% slow released N) + 20% organic N fertilizer, as N 165 kg/hm² (N2); and 4) N2 + biochar, with the same amount as 50% maize straw (N3). The plant and soil samples (0–20 cm depth) were collected at the harvest, the related items were analyzed using regular methods. N₂O emission was analyzed after the basic and topdressing fertilization.

ResultsCompared with the N0, the average yields of the N1, N2 and N3 from 2013 to 2015 were significantly increased by 62.7%, 67.7% and 80.1% (P < 0.05), respectively. The average maize yield of three years in the N1 was 10421 kg/hm² which was 3.0% and 10.7% lower than those of the N2 and N3, respectively. The sustainable yield index (SYI) in the N3 was higher than those in other treatments. Compared with N1, the cumulative chemical N use efficiencies of the N2 and N3 were increased by 8.4% and 12.7% in 2013, by 10.2% and 15.5% in 2014, and significantly increased by 8.4% and 12.7% in 2015 (P < 0.05). The cumulative chemical N use efficiencies of the N2 and N3 showed increasing trend year after year and the increase in the N3 was bigger than in the N2. The single application of fast release N fertilizer resulted in greater soil N₂O emission. Soil N₂O emission in the N3 was significantly decreased by 53.2% compared to the N1 (P < 0.05). The integrated fertility indexes (IFI) in the N3 was higher than those in other treatments.

ConclusionsThe optimum N managements can be coordinated to achieve high maize yield and high N use efficiency in Northeast China by regulating the amount of N fertilizer with adding biochar and substituting chemical fertilizer N with organic fertilizer N and slow release N.