Responses of potato yields to nitrogen application and associated driving factors in China

Objectives The response of potato yields to nitrogen (N) application rates and its driving factors were quantitatively evaluated at national and regional scales, aiming to provide references for making rational recommendation of N management in potato production.

Methods The data of potato yield response to N rates, in field experiments published in literatures of China, were collected and screened and summarized. Meta-analysis method was used to explore the potato yields response to no N fertilizer versus N fertilizer; and meta-regression analysis and subgroup analysis were used to evaluate the effects of different factors on N application.

Results A total of 220 datasets were obtained from 52 papers, which was covering six main planting region of potato in China, and there was significant heterogeneity among different study results. According to the analysis results of the fail-safe method, this study was not significantly affected by publication deviation, and the conclusion had a high credibility. The results of meta-analysis showed that, N application significantly increased the potato yields by 31.1% in China, and there were significant differences in yield-increasing effects of N fertilizer (YIEN) among fields with different basal yields. The YIEN were significantly correlated with N rates, in spite of the significant differences among planting regions. The YIEN were the highest in southwest China with yields increasing rate of 42.6%, followed by the northeast (40.6%), central plain (37.2%), north China (34.7%), south China (17.7%) and northwest (12.1%). Under low N rate, applying methods had similar effect on YIEN, but when N rates were greater than 225 kg/hm², basal and top dressing were significantly more effective. For the planting density, the yield increasing rate of N fertilizer in low density (< 5.25 × 10⁴ plants/hm²) was 35.4%, which was significantly higher than that in medium (5.25 × 10⁴–6.75 × 10⁴ plants/hm²) and high density (> 6.75 × 10⁴ plants/hm²). The YIEN was closely related to soil properties. The YIEN were significant in yellow-brown soil, red soil, black soil, yellow soil, chernozem, paddy soil and dark loessial soil, but not in loessal soil. In clay soil, the yield increasing rate of N fertilizer was 54.8%, higher than that in sandy soil (46.5%), sandy loam (28.0%) and loam (26.0%). In the soils with pH 6.5–7.5, organic matter content < 15 g/kg, total N content of 1–2 g/kg and available P < 15 mg/kg, the YIEN were higher than that in the other soils.

Conclusions N fertilizer application is important for high potato yields, although the effect varies greatly across China. The field basal fertility, planting region, planting density and soil physio-chemical properties all affect the YIEN, and they should be considered when making N application recommendation for potato production.