Buckwheat is known for its long, time-extended period of the formation and filling and ripening of grains, and besides it is very prone to the scattering of grain. In this regard, one of the most important conditions for collecting high yields of buckwheat without loss is the harvesting of crops in the optimal time. In the production of very frequent situations in which it is necessary to delay harvesting. The purpose of this study was to investigate the causes and establish the dynamics of losses from the shedding of buckwheat grain yields depending on the standstill for 5, 10, 15 days after the onset of the phase of complete ripeness of grains, as well as from the imported mineral fertilizers calculated by the balance method for obtaining pre-planned harvests.It was found that the best values of the 1000 grains mass index are formed in cases with agricultural backgrounds for harvesting 30 centners per hectare, as well as with the optimal harvesting time - 31.5 g, with a delay of 5, 10 and 15 days the value of this indicator decreased by 2.1, 5.5 and 8.5 g, accordingly. The same trend was observed for indicator of weight of seeds per bushel. 15 days delay in harvesting since start of mass ripening reduced the grain content both in the control and in all investigated agricultural backgrounds of nutrition: case No. 1 - from 662 to 627 g / l, №2 - from 688 to 647, №3 - from 689 up to 641 and 4 - from 699 to 643 g / l.