Effects of nitrogen fertilizer rates on nutrient uptake, vertical nutrient distribution, and nitrogen balance in dryland spring wheat

Aixia Xu^1,2,3*Dr. Khuram Shehzad Khan^1,2Yan Zhang^1,2Nana Liu^1,2Pengbin Liu^1,2Yafei Chen^1,2Xuexue Wei^1,2Chongrui Sun^1,2ZECHARIAH EFFAH⁴Lingling Li^1,2*

• ¹State Key Laboratory of Aridland Crop Science, Gansu Agricultural University, Lanzhou, China
• ²College of Agronomy, Gansu Agricultural University, Lanzhou, China
• ³National Demonstration Center for Experimental Plant Production Education (Gansu Agricultural University), Lanzhou, China
• ⁴CSIR-Plant Genetic Resources Research Institute, Bunso, Ghana

Optimizing nitrogen (N) fertilizer management is essential for sustainable crop production in semi-arid, rain-fed agricultural regions. This study evaluated the effects of different N-fertilizer rates on nutrient uptake, soil nutrient distribution, and N balance in spring wheat (Triticum aestivum L.) under dryland conditions. The analysis was based on a long-term field experiment initiated 2003 in Dingxi, Gansu Province, China, with five N application rates: 0, 52.5, 105.0, 157.5, and 210.0 kg N ha−1 (designated as N1-N5). Study The study results showed that the concentrations and accumulations of N and K in wheat organs increased significantly with increasinghigher N rates.. However, both yield and nutrient uptake plateaued atfter the N application rate of 105 kg N ha−1 (N3) and , with no statistically significant benefits were observed atfrom higher Napplication rates.However, when the N-fertilizer rate exceeded 105 kg N ha−1 (N3), further increases in grain N and K accumulation and total plant N concentration were not significant. In contrast, increasing N fertilization significantly reducsuppressed grain P concentration, with the N5 treatment showing a 17.80% decreasereduction compared with N1. Soil nutrient responses exhibited clear vertical differentiation. Residual available N in the 0-100 cm soil layer increased significantly with increasing N rates, with a (32.20% increase underin N5 compared withvs. N1), whereasile available P decreased by 31.49%. Available K showed redistribution characteristics, with the surface layer and enrichment in the subsoil. Nitrogen balance analysis indicated that the apparent N-use efficiency decreased from 95.12% to 39.71% as N rates increased, while the apparent loss rate shifted from negative to positive values, reaching 33.79% underin N5. The N3 treatment achieved a near equilibrium N balance (8.69 kg ha−1), whereas the N5 treatment resultedexhibited in a substantial N surplus of 102.34 kg ha−1. Overall, an application rate ofUnder these conditions, applying 105 kg N ha−1 was identified as the optimal N -fertilizer rate for dryland spring wheat. This rate ensured adequatesufficient N uptake and grain yield, maintained high N use efficiency (NUE), minimized potential environmental risks, and achieved a balanced N supply-and demand relationship.