2009 Volume 80 Issue 2 Pages 143-151
Recently, Japan has placed a legal restriction on the stacking of livestock manure in the fields owned by livestock farmers. As a result, compost containing a large amount of sodium and potassium (salt-concentrated compost), has been made from the manure. Due to the high amount of salt, it is difficult to determine the suitable amount of salt-concentrated compost to use for vegetable cultivation in the field. This study aimed to clarify the effects of salt-concentrated compost on mini tomato (Solanum lycopersicum) growth and on soil by investigating the time course transition of soil solution composition and its cation balance. Mini tomatoes were cultivated in pots filled with an Andosol and a Brown lowland soil (Fluvisol) applied with chemical fertilizer, normal compost or salt-concentrated compost. The concentration of soil solution transited at a low level after normal compost application. However, the concentration of soil solutions increased in accordance with the amount of salt-concentrated compost applied, and was maintained at a high level during mini tomato cultivation. The application of salt-concentrated compost to the Andosol caused a blossom-end rot disease to the mini-tomato fruits. Blossom-end rot is known as a response to calcium deficiency. Since the application of the salt-concentrated compost drastically increased the concentration of potassium and sodium in the soil solution, it was suggested that the relative ratio of calcium to monovalent cations was a key factor causing the symptom. By introducing a new index for the activity ratio for potassium plus sodium, i.e. AR^<K+Na>, composition of cations in the soil solution could be evaluated quantitatively. Based on the analyses using AR^<K+Na>, it was found that blossom-end rot occurred when AR^<K+Na> value became too low and exceeded some level (-0.1 in the present case) while mini tomato fruit was constituted at the first branch. In the case that the amount of salt-concentrated compost applied to the Andosol was reduced to be 20Mg ha^<-1> or less, the values of AR^<K+Na> were higher than the value when blossom-end rot had occurred, and the blossom-end rot did not occur.
