Management, production, and nutritional characteristics of cup-plant (Silphium perfoliatum) in temperate climates of southern Chile
There is little information known about the response of cup-plant (Silphiumperfoliatum L.), a perennial forage crop introduced to Chile, to differing cultivation practices. A series of studies was conducted to evaluate the adaptation and productivity of cup-plant across a range of plant densities (104,000 - 208,000 plants ha-1), cutting stages (early vegetative to seed formation), and different levels of N (0 - 400 kg N ha-1) and P (0 - 400 kg P2O5 ha-1) fertilization. Field experiments (40°S 73°W) were conducted over a 3-yr period in a subhumid, Mediterranean climate on three distinct andisols that originated from volcanic ash, with pH values of 5.2 to 5.6. The forage dry matter yield, plant components (stem count, stem diameter, plant height, and leaf:stem ratio), and nutritional characteristics (crude protein, plant cell wall components, and in vitro dry matter digestibility) were determined. During the first year of growth, cup-plant exhibits a rosette growth habit; the measurements were begun the second spring after planting and were taken during two consecutive growing seasons. Plant density over 120,000 plants ha-1 did not affect dry matter yield, which ranged from 15 to 20 t ha-1. Stem number and thickness did vary due to plant density, but height and leaf:stem ratio were not affected by density. The leaf proportion of the plants varied between 30 and 45% in the different experiments. In the cutting regime study, lower forage yields but higher nutritional values were observed with earlier first cuts. When the first cut was delayed from the early vegetative stage to the seed stage, crude protein declined from 140 to 60 g kg-1 and digestibility from 790 to 580 g kg-1, mainly due to the low nutritional value of the stems. The dry matter yield and crude protein increased with increasing levels of N and P fertilization. Cup-plant requires and absorbs low quantities of nitrogen, what renders it to be a low protein forage resource. At seemingly low rates of nitrogen fertilization, it is an efficient biomass factory. It was concluded that cup-plant can be incorporated as a regular perennial summer fodder crop and also as a special feeding resource during summer drought as a supplement to existing pasture areas when its availability becomes limited. Its adaptive and productive characteristics also make it suitable for low-input farming systems.