Effect of fertilizer levels on the traits of growth and yield in buckwheat (Fagopyrum esculentum Moench)

The experiments were conducted in Meijo University, Nagoya, Japan, to investigate the effects of different fertilizer levels on growth, flowering, seed set and yield components in buckwheat (Fagopyrum esculentum Moench). The seeds of the summer ecotype buckwheat cultivar, Shinanonatsusoba, were sown in 1/5000 a pots fertilized with 1 g, 3 g, 5 g, 10 g and 15 g of the compound fertilizer (N, P2O5 and K2O were 15%, 15% and 10% each) on 31 August in 2000 and in the pots fertilized with 1 g, 5 g, 10 g, 20 g and 40 g on 15 May in 2001. The growth of the plants and the bloomed flower number of each flower cluster were traced and the number of flowers and seeds on each flower cluster of the main stem and each branch were measured. The fertilizer levels did not affect the duration of the main stem growth, the start of flowering, the first flowering node, the progression rate of successive flowering of clusters on the main stem, the number of clusters on the main stem, seed size and one-seed-weight. Increasing the fertilizer level increased the length of the main stem and the leaves on that, but the promotions were about 10 cm and 2 cm respectively. The promotions did not seem to be the causes of the lodging by high fertilizer level. The promotion of the development of lateral branches by high fertilizer level, however, might give rise to lodging. Excessive fertilizer, for example 40 g per pot inhibited emergence and early growth. However, when the abnormal plants were neglected, increase in the fertilizer level increased the number of seeds and the seed yield per plant, although increase in the fertilizer level did not affect one-seed-weight. With increase in the fertilizer level, the development of the lower node branches and the higher order branches was promoted and the number of clusters on them increased. Furthermore, the seed number per cluster increased, because of not only the increase in the flower number per cluster but also the seed-set ratio of the clusters. The increase was greater on the primary branches than on the main stem and was further greater on the secondary branches. As the duration of flowering was prolonged because of the delay of the start of flowering in higher order branches, the variation of maturing time of seeds in a plant seemed to increase. The seed-set ratio was the highest in the clusters on the main stem and lower in the clusters on the higher order branches. Because increasing the fertilizer level increased the number of flowers on the clusters of the higher order branches which showed low seed-set ratio, the increase of the seed-set ratio with higher fertilizer level in a plant was unclear.