Nutrient balances in the second year of growth.

摘要

A study by the Geisenheim Research Institute (Germany) investigated growth and nutrient take-up by asparagus crowns both on experimental plots and in commercial field conditions. Fibrous roots were also analysed. In the autumn of the first year after planting, it was found that in field conditions crown mass was often 0.7 - 1.1 kg per plant. Assuming a planting density of 16,835 per hectare, N content of crowns in well-developed stands could be around 100 kg/ha with K almost the same. In the second year, with some exceptions, crown mass averaged 2-4 kg. Given the above planting density, this indicates a fresh plant mass of 33.7 - 67.3 t/ha with 6.9 - 13.8 g N retained in each crown and K still higher, potentially 116-232 kg/ha. Nutrient removal during harvest, assuming a duration of about 2 weeks, is estimated at 5 - 15 kg N/ha. A 2-week harvesting period is considered optimal for well-developed young spears. Assuming an average crown mass of 3.5 kg at the end of the second year, the requirements for N and K will be up to 128 and even over 190 kg/ha respectively. At normal density, crowns could contain 96 -307 kg N/ha.