Impact of the seeding and fertilization rates of cover crop and the seeding rate of red clover on the seed yield of the cultivar 'Varte'

In the years 2012–2014, a field trial was conducted at the Estonian Crop Research Institute in order to investigate the effects of the seeding rate and nitrogen fertilizer rate of two-row barley 'Inari' on the stand formation and seed yield of the under-sown red clover tetraploid cultivar 'Varte' (4n), in the first and second years after establishment. The trial had four basic variants, with different seeding and fertilization rates of cover crop and four different seeding rates of red clover. The trial results indicated that both the seeding rate and the nitrogen fertilizer rate of the cover crop had an impact on the development of the red clover stand and its later seed yield. The effect of fertilizer rate was greater. Of the red clover seeding rates the variant with 4 kg of 100% pure live seeds (PLS) per hectare yielded, as a total of the two years, 79–142 kg ha-1 (8–16%) more clover seed than the variant half the seeding rate. The red clover seeding rates of 6 and 8 kg ha-1 were more recommended under the conditions, where the cover crop was seeded at the rate of 500 viable seeds per m2 and nitrogen applied at a rate of 90 kg ha-1. Neither the seeding and fertilization rates of the cover crop, nor the seeding rates of red clover, had any effect on the 1,000 seed weight and germination rate. Based on the received income from the sales of the grain yield of the cover crop and the seed yields over the two years, it is recommended to establish the red clover seed field by sowing under a cover crop by reducing the seeding rate and nitrogen fertilizer rate of cover crop by one third.