Yields in vetch-wheat mixed crops and sole crops of wheat
Institute of Agricultural and Environmental Sciences; Estonian University of Life Sciences, Kreutzwaldi St. 64, 51014 Tartu, Estonia; e-mail: email@example.com
Field trials with common vetch (Vicia sativa L.) and spring wheat (Triticum aestivum L.) mixes were conducted from 1994 to 2004 on pseudopodzolic moderately moist soils in the trial fields of the Institute of Agricultural and Environmental Sciences of the Estonian University of Life Sciences at Eerika, outside Tartu (58o 23´ N, 26o44´ E). The results of the research showed that in cases where the yields of post-cereal wheat monocultures were 1500–3000 kg ha-1 vetch-wheat mixed crops (at the seed densities of 50 germinating vetch seeds and 250 germinating wheat seeds per m2) guaranteed an approximate harvest of 3000 kg ha-1, even under no nitrogen fertilisation, provided the total amount of precipitation in the growth period was 300 ± 50 mm. If the yields of monocultural wheat topped the level of 3000 kg ha-1, mixed crops, however, lost their advantage over wheat monocultures as the latter’s grain harvests were greater in those cases. Vetch-wheat mixed crops maintained their advantage over sole crops of wheat insofar as protein yields were concerned, primarily due to the high protein content of vetch. The extra gain in the protein yields of mixed crops compared to wheat monocultures was 100–500 kg ha-1 in our study, and was heavily dependent on the protein levels monocultural wheat was able to produce in each particular case.