Abstract:

The aim was to study the effect of optimizing N management on root yield at harvest of Rehmannia glutinosa Libosch and quality. Two on-farm field experiments were conducted to evaluate dry-matter accumulation and N demand characteristics of Rehmannia glutinosa Libosch with different N management, to optimize N fertilizer application rate with different N rate experiments, and to determine optimal ratio between basal and topdressing fertilization with different base:topdressing ratio experiment. Whatever dry-matter and N uptake, the accumulation peaks occurred from root elongate to root enlargement. The highest dry-matter accumulation is 0.86 g/(day?zhu) from root elongate to root enlargement, and the highest N uptake is 0.014 g N/(day?zhu). The yield of Rehmannia glutinosa Libosch can increase by 23%-29% by optimal N application rate, compared to no N application. Compared to base N application treatment, the yield of Rehmannia glutinosa Libosch can increase by 25% with base: topdressing of 3:7 treatments. Across two years studies, the optimal N fertilizer rate should be 121-132 kg N/hm2, and 70% of total N fertilizer should be applied the fastest growing stage, such as root elongate phase.