The role of fertilization practices in the yield and quality of carrot (Daucus carota L.)

Abstract

The influence of different fertilization practices on the growth, yield and inner quality of carrot (Daucus carota L.) was studied. The field experiments were carried out in Southern Finland, on the experimental farm of Kemira Oy, in 1985 and 1986. Unirrigated and irrigated placement and broadcast fertilization, NPK fertirrigations without or with basic fertilization, and PK placement with N fertirrigations were compared. Placement and broadcast fertilizations were carried out by single application, whereas NPK or N fertirrigations were performed as split applications. The highest yields were obtained when the total phytomass production was high. The yield increased by the placement of NPK fertilizer as compared to broadcast fertilization, and by the placement of P and K as compared to treatments where P and K were broadcasted or fertirrigated. The PK placement with N fertirrigations increased the root dry matter content as compared to NPK fertirrigations. The lowest NO3-N contents of roots were obtained by unirrigated placement fertilization. NPK fertirrigations caused higher root NO3-N contents than any other fertilization practice, and irrigation as such increased the NO3-N contents. Root N and P contents were increased by placement of PK or NPK fertilizers, but fertilization practices had no effects on K, Mg and Ca contents. Single application increased ash and dietary fibre contents as compared to split applications. In conclusion, the placement of NPK or PK fertilizers had positive effects on the above mentioned quality criteria and yield, and thus in future research and in commercial vegetable production these fertilization practices should be utilized. Fertilization practices had no or only slight effects on the carotene and sugar contents, taste, texture and the quality of stored carrots. Carotene content increased as the growing season progressed, and was 41 % higher in the climatically more favourable year 1986 than in 1985. Total sugar contents were higher in the climatically less favourable year 1985 and in unfertilized treatments than in 1986 and in fertilized treatments. It was hypothesized that carrot sugar contents are related to growth and total phytomass production. The indicative results showed that the NPK fertirrigations without basic fertilization had a slight positive effect on carrot taste and texture as compared to placement fertilization but, on the other hand, the NPK fertirrigations without basic fertilization showed a tendency to impair the storage ability as compared to single application. In conclusion, carotene and sugar contents are strongly influenced by genotype and climate and thus it is logical that the effects of fertilization practices remained slight. The results of carrot taste do not allow any final conclusions to be drawn; further investigation on the subject is needed.