COMPARISON OF PEAT AND BARK-HUMUS IN GREENHOUSE AND OUTDOOR VEGETABLE CULTURE
The trace elements were not analysed in the latter case, but the recommendations are given in brackets. Peat was used in basin culture as unmixed 20 cm thick substrate and was of the general ST-400 type.
In greenhouse tests with tomato, in Viik, the changes in bark-humus data are stated in table 2.
The P, K and N contents thus tend to decrease, and in spite of top dressing it was hard to keep the contents of P high enough. Corresponding data on peat are given in table 3.
The most critical nutrients in peat were Ca, K and P. The nitrogen level seemed to be easier to control. In both of the materials, however, frequent analyses and top dressings are needed in order to keep the nutrients constant. In these tests the tomato yields and their content was as follows in table 4.
In another series of test peat and bark-humus from exactly the same sources were used as before. In greenhouse peat basin culture was used in experimental farms at 69°05' and 60°11' latitudes. In order to maintain the nutrition level the following fertilisation was given: on 27th of May Ca(NO)2 40 g/m2, on 12th of June urea 10 g/m2 and Complexa (6-12-12) 40 g/m2, and finally on 3rd of August the same amounts as on 27th of May. In this way the only critical points were the Ca content and pH, which tend to decrease.
In 1969–1970 the yields in greenhouse, and in peat basins outdoors at the same sites are given in table 5.
By using the peat basin method results on similar substrates in different localities can be achieved, the variables being in this case temperature and daylength. Only results of the same year are comparable, in different years the crop varieties and climate varied considerably. Because of this, however, in the warm summer of 1969 the yields were often higher in the north than in south, due to the daylength.
At the same latitudes peat and bark-humus were compared in outdoor culture. Two amounts of bark-humus were mixed in May 1969 with sandy soil, namely 5 m3/a and 10 m3/a. Peat basins were started the same year. In the end of May 1970 and 1971 the analyses gave following data in Muddusniemi, at 69°05' latitude (table 6).
N, K and P were very low in spring due to plant consumption and to