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.

Effects of band placement and nitrogen rate on dry matter accumulation, yield and nitrogen uptake of cabbage, carrot and onion

“…As in my experiments, Evers (1989) reported that the carrot shoots grew close to their maximum weight in three months, thus following the sigmoidal growth curve. Whereas the storage roots grew slowly during the first two months, growth increased considerably during the third and fourth month.…”

“…The low yield of 50 t ha -1 in 1995 was due to the aged transplants that also suffered from the moist early summer, resulting in 30% transplant mortality. The carrot yield levels in my experiments, 45-100 t ha -1 , were usually higher than the yield levels presented by Dragland (1977) in Norway (50-70 t ha -1 ) and Evers (1989), (39-45 t ha -1 ) but close to the yields presented by e.g. Roll-Hansen (1976) in Norway and Greenwood et al (1980) in England.…”

“…This sigmoidal growth curve has been observed e.g. for cabbage by Huett and Dettman (1989), Riley and Guttormsen (1993b) and Guttormsen and Riley (1996), for carrot by Evers (1989) and for onion by Dragland (1975Dragland ( , 1992. The short growing season in Finland can sometimes cause growth cessation early, when the growth rate is still high.…”

“…This might be an additional reason why carrot yield has been relatively insensitive to experiments with water and nitrogen supply as assumed by Pietola (1995). But since placement of NPK fertilizer has resulted in higher carrot yields than broadcasting of NPK fertilizer both in Norway and Finland (Ekeberg 1986, Evers 1989, placement of N solely might also be beneficial for carrot growth. In Finnish studies con-Vol.…”

“…Regarding carrot, Evers (1989) determined that carrot shoot nitrate-N concentration decreased from 4-5 g kg -1 DM (66-75 das) to 0.5-1.5 g kg -1 DM at harvest (116-121 das). Nitrate-N content was at first approximately 15% of the Kjeldahl-N and at harvest 2-8%.…”