Effects of potassium fertilization and periderm damage on shelf life of carrots
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Short shelf life has caused a decline in the sale of B.c.-grown carrots from 8.1 million kgs in 1987 to 6.1 million kgs in 1990. This is due to greater postharvest water loss of B.C.-grown carrots compared to those from California and Washington. The aim of this study was to improve our understanding of the factors affecting carrot water loss by (1) establishing a procedure to measure surface area of carrot roots, (2) determining the effect of K fertilization on carrot growth, yield and water loss, and (3) determining the effects of periderm damage and interaction between periderm damage and K fertilization on water loss of carrots. Baugerod (1993), slicing and surface replica methods for determining surface area of carrot roots were compared using eight carrot varieties on two harvests, and on size grades small, medium, and large of carrots. Surface area values using the three methods were statistically different but the variation was less than 6%. Baugerod method is applicable to carrots of different sizes and can therefore be used to determine surface area of carrots. Carrots were fertilized with five levels of KCl and one level of K2S04 on muck soil, and stored at 13°C and two levels of relative humidity (RH) to assess the effect of rate and source of K on carrot growth, yield, and water loss. Five levels of carrot periderm damage were used to study the effect of periderm damage on water loss. The rate and source of K had no significant effects on growth and water loss. No significant effects of interaction between rate of application of KCI and periderm damage on water loss were observed. Increase in rate of KCI significantly reduced marketable yields probably due to a reduction in carrot stand. KCI significantly reduced marketable yield of carrots compared with K2S04 applied at same rate. Periderm damage and low RH significantly accelerated water loss and thereby reduced the shelf life of carrots in storage. It was concluded that there was adequate K in muck soil in Cloverdale area (B.C.) to meet carrot requirement, and that K fertilization is unnecessary. The short shelf life of B.C.-grown carrots is likely due to periderm damage and/or storing of carrots at low RH. It could be extended by minimising periderm damage and/or storing carrots at high RH to reduce water loss, hence improving their acceptability.