Effect of nitrogen application on nitrogen nutrition and yield of wheat in fields of different fertility

Objectives Nutrient supply of a field is determined by its soil fertility and fertilizer application. Soils with different fertility levels have different nutrient supply capacity and characteristics. This study looked at the effects of nitrogen application rates on spatial and temporal distribution characteristics of nitrogen in soil and grain yield in fields with different fertility in Henan Province to provide a reference and basis for rational use of nitrogen fertilizer and improvements in yields.

Methods A field experiment using four nitrogen rates (0, 120, 225, 330 kg/hm², represented as N0, N1, N2, N3) and Aikang58 as the wheat cultivar was conducted from 2015 to 2016. Soil nitrate concentration and yield from anthesis to maturity, dynamics of leaf nitrogen concentration, SPAD value, nitrogen accumulation of leaves of different positions, and nitrogen concentration of whole plant and all leaves at the anthesis, 10 days after anthesis and 20 days after anthesis stage were measured.

Results Nitrate concentration in soil increased with nitrogen application rates from the anthesis to maturity, and nitrate concentration in field of high fertility was significantly higher than that of low fertility field. While nitrogen application significantly increased grain yield in the low fertility field, the yield of high soil fertility field was higher than that of the low soil fertility field. The yield increase with nitrogen application in low soil fertility field was 2.63 times that of high soil fertility field compared with no nitrogen treatment. Although SPAD value of the flag leaf and the second leaf from the top in the N1and N2 treatments of the high fertility field at anthesis and 10 days after anthesis was higher than that of the low fertility field, the trend was the opposite at 20 days after anthesis. Although nitrogen concentration of the flag leaf of N1, N2 and N3 in the high fertility field at 10 days after anthesis stage was higher than that of the low fertility field, the trend was opposite at 20 days after anthesis. In the low fertility field, the contribution of the flag leaf to nitrogen accumulation of the top four leaves was the biggest (52.6%) (except the N0 treatment); the contribution of the flag leaf and the second leaf from top to nitrogen accumulation of the top four leaves was the biggest (39.9% and 39.7%) respectively. The amount and rate of nitrogen translocation of different leaves of the high fertility field were generally higher than those of the low fertility field.

Conclusions Nitrogen application increased soil nitrate concentration and soil nitrogen supplying capacity. The amount and rate of nitrogen translocation of different leaves in the higher fertility field were generally higher than those in the lower fertility field. As the yield of the lower fertility field still cannot reach that of the high fertility field, improvement of soil fertility and optional fertilizer input should be considered for improving yield. The highest nitrogen application rates for the maximum yield are 213 kg/hm² and 287 kg/hm² for the high and low fertility fields, respectively.