Planting density and fertilisation independently affect seed and oil yields in Plukenetia volubilis L. plants

Summary

To investigate the effects of planting density and fertiliser level on some important agronomic traits of Plukenetia volubilis, a perennial oilseed species, a field experiment with four replications in a completely randomised block design was conducted in a tropical region of China in the 2012-2013 growing season. Planting density (1,666, 2,500, 4,444, 5,000, or 10,000 plants ha^–1) was assigned to the main plots and a 1:1:1 (w/w/w) NPK fertiliser at 0, 50 100, 150, or 200 kg ha^–1 was assigned factorially to the sub-plots. The results showed that neither planting density nor the rate of fertilisation affected seed size (dry matter) and the phenological development of P. volubilis plants, including the times of initial flowering and maturity, or the pattern of fruit ripening. Planting density, rather than fertiliser level, significantly affected seed oil content, but a non-linear effect was found. Across the different treatments and sampling times, seed size and oil content had relatively high and constant heritabilities indicated by low coefficients of variation. Total seed yields and total oil yields per plot over the growing season ranged from 1,340 - 2,486 kg ha^–1, and from 501 - 899 kg ha^–1, respectively, with a quadratic response to planting density at all fertiliser levels. Total seed and oil yields increased continuously with the increasing levels of fertiliser used.The absence of any planting density fertiliser level interaction on total seed and oil yields suggested that planting density and fertilisation had independent effects, and that seed or oil yield responses to planting density were not significantly affected by fertiliser level. We concluded that oil production in P. volubilis plants required high levels of fertiliser and, regardless of fertiliser level, a planting density of approx. 4,444 plants ha^–1 was required to ensure maximum yield in the field.