Objective  Improvement for grouting of the commonly poorly filled grains of tetraploid tartary buckwheat by potassium fertilization was studied.

  Method  Buckwheat TB195 was treated with varying potassium fertilization at 0 kg·hm^-2 (CK), 12 kg·hm^-2 (LK), 24 kg·hm^-2 (MK), and 48 kg·hm^-2 (HK) in a randomized block experiment. Effect of the fertilizations on grain-grouting, root morphology, grain plumpness and yield of the buckwheat plants were determined.

  Result  Among all treatments, the initial grouting potential (R₀), days to reach maximum growth rate (T_max·G), weight at maximum grouting rate (W_max·G), plumpness, and yield of the grains, as well as the length, surface area, and volume of the plant roots were maximized when MK was applied. The 31.63% grain-filling under MK was 45.22%, 38.12%, and 23.79% higher than those under CK, LK, and HK, respectively. The 2-year average yield of 1, 159.3 kg·hm^-2 by MK was 54.60%, 50.19%, and 31.58% higher than CK, LK, and HK, respectively. The contribution rate of the various fertilizations in different grouting stages to the grain weight gain was the highest when potassium was applied during the middle period followed by the late stage, and the lowest in the beginning of grouting. The shape indicator (N) was the highest under CK, and lowest with MK treatment.

  Conclusion  At the rate of 24 kg·hm^-2, the application of potassium fertilizer not only promoted the growth and development of tetraploid tartary buckwheat plants, but also significantly increased the grouting and yield, as well as the market appeal, of the grains.