ISHS Acta Horticulturae 448: III International Symposium on Mineral Nutrition of Deciduous Fruit Trees
ENHANCING CALCIUM UPTAKE IN ORGANIC APPLE GROWING |
| Author: | F.P. Weibel |
| Keywords: | bitter pit, malus domestica, fertilization, calcium chloride, soil management, apple |
| Abstract:
Bitter pit of apple due to Ca deficiency in fruits is an important disease in biological (organic) apple production, where treatments with calcium chloride usually are not allowed. Organic apple growers mostly use farmyard manure as a fertilizer, which can be unbalancedly rich in K, the main antagonist to Ca uptake. We monitored the mineral status of four biological orchards in different regions of Switzerland, in order to quantify the interactions between element concentrations of soil, leaves and fruits. Per site 25, soil samples were taken on a transect along the tree strip at depths of 0–12, 13–25, 26–50 cm. Varieties were «Boskoop» on rootstock «M9vt» on three sites and «Maigold» on «M2vt» on one site. Contents of Ca, K, Mg and P were quantified in soil, young fruits and leaves at T-stage and in ripe fruits after storage from trees close to each soil sampling spot. The orchards clearly showed different nutrient levels in soil, leaves and fruits. Covariance of Ca contents within the orchard was decreasing in the order soil < young fruits < leaves < ripe fruits. Calculations showed that 20 subsamples are sufficient for mixed samples of 95 % accuracy. Closest correlations between soil and plant were found with K content in the upper soil layer and K content in young fruits and leaves (r2 = 0.79 and 0.81 respectively). With Ca the same correlation was much weeker (r2 = 0.61 and 0.22). Ca and K contents of young fruits or leaves showed no significant correlations to bitter pit in ripe fruits; nevertheless Ca content in the stored fruits played the dominant role: 3.5 g Ca 100 g-1 FM was the mean value of fruits without bitter pit, 2.45 g 100 g-1 FM was the average Ca content of affected fruits. Closest correlation to bitter pit (r2 = 0.71) was found with the ratio of K : Ca contents in the topsoil. | |
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