NITROGEN FERTILIZATION OF SEED RADISH (RAPHANUS SATIVUS L.): EFFECTS ON YIELD AND N-CONTENT IN SEED, PLANT AND SOIL(*)
A spring-sown seed crop of annual radish (Raphanus sativus, var. radicula) cultivar spaced 60 x 25 cm apart was tested in 1989, 1990 and 1991 with dressings of 0, 75, 150, 225 and 300 kg N ha-1 partitioned as follows: one-third at sowing, one-third at emergence and one-third at bolting. Seed yield always increased at N-rates up to 150 kg ha-1 - 684, 597 and 936 kg seed ha-1 in the respective years - and decreased at higher rates. This pattern also held for seed number per plant, the only one of the seed yield components to be so; 1000-seed weight and seed germination showed slight influence only in 1991. Total N-content in roots and stem-leaves at harvest increased linearly along with N-input. Seed N-content instead was never significantly affected, and soil total N-content at 0–30 cm and 30–60 cm depths was unchanged. This contrasts with NO3-N soil content at both depths: it increased linearly along with N-rates, except in the very rainy 1989 season, and was higher at the 0–30 depth. Note, however, that in two of the three years the NO3-N soil content at the 0–60 cm depth was lower at harvest than at sowing, an amount that decreased along with rising N-input. The optimum N-rate appeared to be 150 kg ha-1: at higher inputs it proved unable to increase seed yield and quality but capable of increasing NO3-N soil and biomass content, although a negative impact from leaching on the groundwater may occur.
Lovato, A., Montanari, M. and Miggiano, A. (1994). NITROGEN FERTILIZATION OF SEED RADISH (RAPHANUS SATIVUS L.): EFFECTS ON YIELD AND N-CONTENT IN SEED, PLANT AND SOIL(*). Acta Hortic. 362, 117-124